JOURNAL OF MORPHOLOGY 269:1387–1411 (2008) Skeletal Indicators of Locomotor Adaptations in Living and Extinct Rodents Joshua X. Samuels* and Blaire Van Valkenburgh Department of Ecology and Evolutionary Biology, University of California-Los Angeles, Los Angeles, California 90095 ABSTRACT Living rodents show great diversity in their locomotor habits, including semiaquatic, arboreal, fossorial, ricochetal, and gliding species from multiple families. To assess the association between limb morphology and locomotor habits, the appendicular skeletons of 65 rodent genera from 16 families were measured. Ecomorphological analyses of various locomotor types revealed consistent differences in postcranial skeletal morphology that relate to functionally important traits. Behaviorally similar taxa showed convergent morphological characters, despite distinct evolutionary histories. Semiaquatic rodents displayed relatively robust bones, enlarged muscular attachments, short femora, and elongate hind feet. Arboreal rodents had relatively elongate humeri and digits, short olecranon processes of the ulnae, and equally proportioned fore and hind limbs. Fossorial rodents showed relatively robust bones, enlarged muscular attachments, short antebrachii and digits, elongate manual claws, and reduced hind limb elements. Ricochetal rodents displayed relatively proximal insertion of muscles, disproportionate limbs, elongate tibiae, and elongate hind feet. Gliding rodents had relatively elongate and gracile bones, short olecranon processes of the ulnae, and equally proportioned fore and hind limbs. The morphological differences observed here can readily be used to discriminate extant rodents with different locomotor strategies. This suggests that the method could be applied to extinct rodents, regardless of ancestry, to accurately infer their locomotor ecologies. When applied to an extinct group of rodents, we found two distinct ecomorphs represented in the beaver family (Castoridae), semiaquatic and semifossorial. There was also a progressive trend toward increased body size and increased aquatic specialization in the giant beaver lineage (Castoroidinae). J. Morphol. 269:1387–1411, 2008. Ó 2008 Wiley-Liss, Inc. KEY WORDS: ecomorphology; functional morphology; locomotion; rodents; beavers; convergent evolution The order Rodentia includes about 2,000 living species and has members that occupy nearly every terrestrial habitat on Earth. Compared with most other mammalian orders, rodents span a wide range of body sizes, from <10 g in some mice to >50 kg in the capybara, Hydrochaeris, and >500 kg in Phoberomys and Josephoartigasia, extinct relatives of the pacarana (Nowak, 1999; SanchezVillagra et al., 2003; Rinderknecht and Blanco, 2008). Rodents have also evolved a diverse array of ecological specializations including semiaquatic, Ó 2008 WILEY-LISS, INC. arboreal, fossorial, jumping, and gliding forms. Similar adaptations are seen in distantly related families suggesting widespread convergence and parallelism over the course of rodent evolution (Howell, 1930; Nevo, 1995; Lacey et al., 2000; Stein, 2000). Many previous studies have compared rodents with particular locomotor habits to their more generalized terrestrial counterparts; however, few studies have examined locomotor characteristics across a wide range of specializations (Bou et al., 1990; Casinos, 1994; Elissamburu ´ and Vizcaıno, 2004). This study examines the morphology of a broad sample of living rodents to: (1) identify skeletal characteristics linked to locomotor behaviors; and (2) identify which characteristics differ between groups. These skeletal features are also used to infer the locomotor behavior of extinct rodent species and improve our understanding of rodent evolution. Ecomorphological analyses have often been used to examine locomotor habits of extant species and to infer behavior in their extinct counterparts (e.g., Van Valkenburgh, 1987; Stein, 1988; Lessa and Patton, 1989; Lessa and Stein, 1992; Biknevicius, 1993; Fernandez et al., 2000; Argot, 2001; ´ Gingerich, 2003; Elissamburu and Vizcaıno, 2004; O’Keefe and Carrano, 2005). These studies use a variety of statistical techniques to relate morphological variables to the ecological niches occupied by species. Their goals are to characterize the morphological space occupied by modern taxa with distinct ecologies and then infer the ecologies of extinct groups from the morphological spaces they occupy. To date, few such morphometric comparisons have examined locomotor adaptations across rodent groups. Previous studies of rodents using ecomorphological analysis include the analysis of specializations for digging in gophers (Lessa and Patton, 1989; Lessa and Thaeler, 1989; Lessa and *Correspondence to: Joshua X. Samuels, Department of Ecology and Evolutionary Biology, 621 Charles E. Young Drive South, University of California-Los Angeles, Los Angeles, CA 90095-1606, USA. E-mail:
[email protected] Published online 5 September 2008 in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/jmor.10662 1388 J.X. SAMUELS AND B. VAN VALKENBURGH TABLE 1. Locomotor categories used in the analyses and their definitions Locomotor category Terrestrial (T) Semiaquatic (Sa) Arboreal (A) Semifossorial (Sf) Fossorial (F) Ricochetal (R) Gliding (G) Definition Rarely swims or climbs, may dig to make a burrow (but not extensively), may show saltatory behavior (quadrupedal only), never glides (e.g., rats and mice). Regularly swims for dispersal, escape, or foraging (e.g., beavers and muskrats). Capable of and regularly seen climbing for escape, shelter, or foraging (includes scansorial species; e.g., tree squirrels and erethizontid porcupines). Regularly digs to build burrows for shelter, but does not forage underground (e.g., ground squirrels). Regularly digs to build extensive burrows as shelter or for foraging underground (e.g., gophers and mole rats). Display a predominantly subterranean existence. Capable of jumping behavior characterized by simultaneous use of the hind limbs, commonly bipedal (e.g., kangaroo rats). Capable of gliding through the use of a patagium, commonly forage in and rarely leave trees (e.g., flying squirrels). Complete lists of extant species included and their classifications are in Appendix (Table A1 and A2. Species were assigned to categories deemed most appropriate, but given that there is some gradation between categories, individual species may be capable of placement within more than one category (e.g., the European water vole is commonly known for swimming and burrowing behaviors). Stein, 1992), semiaquatic locomotion in muskrats (Stein, 1988), and locomotor specializations in cav´ iomorph rodents (Elissamburu and Vizcaıno, 2004). This study includes 65 rodent genera from 16 living families that show terrestrial, semiaquatic, arboreal, semifossorial, fossorial, ricochetal, and gliding locomotor habits (Table A1). We predict rodents with similar locomotor habits will show similar morphologic features as a result of convergent or parallel evolution. Selection pressure for functionally advantageous structures should lead to similarities between taxa regardless of their ancestry. Postcranial material from extinct rodents can be compared with that of extant rodents to determine whether these species had similar locomotor adaptations and lifestyles. Here we apply these methods to extinct members of the families Castoridae (beavers) and Sciuridae (squirrels). MATERIALS AND METHODS A total of 293 individuals of 65 extant rodent genera (67 species) from 16 families were used in this study (average n 5 4.4, n for each species can be found in Table A1). These taxa were chosen to represent a wide range of body morphs and locomotor specializations. Examination at the generic rather than species level was used, because species within the same genus are expected to have similar form. Members of both sexes were used, and only adult, wild-caught specimens were examined. A literature survey was used to classify each species into one of seven locomotor groups: terrestrial, semiaquatic, scansorial/arboreal, semifossorial, fossorial, ricochetal, and gliding (Table 1) (Howell, 1930; Nevo, 1999; Nowak, 1999; Lacey et al., 2000). Each locomotor group includes members of multiple families. Additionally, 15 extant species from other mammalian orders were used to assess the feasibility of applying our results to a broader mammalian sample (Table A2). Specimens of 11 extinct beaver species from three beaver subfamilies, as well as the extinct giant marmot Paenemarmota barbouri were also examined in order to infer their locomotor behaviors (Table A3). Skeletal specimens from extant and extinct species were examined at the following institutions: Museum of Natural History of Los Angeles County, Los Angeles; Donald R. Dickey Collection of the University of California, Los Angeles; Museum of Verte- brate Zoology, University of California, Berkeley; University of California Museum of Paleontology, Berkeley; Idaho Museum of Natural History, Pocatello; University of Kansas Natural History Museum, Lawrence; Field Museum of Natural History, Chicago; American Museum of Natural History, New York; United States National Museum of Natural History, Washington, D.C.; and Hagerman Fossil Beds National Monument, Hagerman. A set of 20 osteological characteristics were measured to the nearest 0.01 mm using digital calipers (Chicago 12‘‘EDC). Measurements included lengths and midshaft diameters of the limb bones, as well as lengths of various functionally important muscular insertions (Fig. 1, Table 2). These measurements were used to compute a set of 16 functional indices (ratios) indicative of locomotor adaptations (Table 3); some indices were novel to this study, whereas others were adopted from previous studies (Tarasoff, 1972; Hildebrand, 1985; Stein, 1988; Elissamburu ´ and Vizcaıno, 2004). Indices represent overall limb proportions and mechanical advantages of the primary muscles used in locomotion. Ratios are commonly used in biological studies because they reflect functional and easy to understand features of organisms. However, the use of ratios can pose problems when used in statistical analyses as they tend to violate assumptions of normality and homoscedasticity included in parametric tests (Sokal and Rohlf, 1995). However, many studies have found the use of ratios in multivariate statistical analyses to be robust (Corruccini, 1987, 1995; Van Valkenburgh and Koepfli, 1993; Elissam´ buru and Vizcaıno, 2004), and additional considerations can alleviate some issues related to their use. Arcsine transformation of ratios prior to analysis can help restore normality to the data set (Atkinson et al., 2004; Christiansen, 2006). Rodents examined in this study include a wide range of body sizes; thus, it is necessary to assess the influence of body size on structures being examined. One method that can be used to examine the interaction between size and shape utilizes the geometric mean (GM) (Jungers et al., 1995; Madar et al., 2002). The GM is a size variable derived from the nth root of the product of n measurements, and the ratio of any particular measurement to the GM is a Mosimann shape variable (Mosimann and James, 1979). Log transformed raw measurements were regressed against log GM scores (as a proxy for body size) to analyze interspecific allometry, with equations in the form of: log y ¼ log a þ b log x where x, body size (log GM); y, measurement; a, y-intercept; and b, slope. Negative allometry was indicated by slopes significantly <1.0, positive allometry by slopes significantly >1.0, and isometry by slopes not significantly different from 1.0 (Schmidt- Journal of Morphology MT3L. manus digit 3 terminal phalanx length. d. 15 extant species from other mammalian orders and the capybara. metacarpal 3 length. Journal of Morphology . deltopectoral crest length. Mph3p. but these deviations did not tend to be significant at the P < 0. 2004). Many characters in the total sample of rodents displayed slight deviation from isometry. olecranon process length. Bivariate plots and linear regressions were used to visualize indices used in the analysis and aid in interpretation of extinct taxa represented by incomplete specimens. radius length. denominator. humerus mediolateral diameter. Another potential problem associated with using ratios is that differences in the numerator. Read and Tolley. TSL. femoral epicondylar breadth. tibial tuberosity length. Measurements of the limb skeleton used in this study. Also. Femoral epicondylar breadth (FEB) showed a significant positive allometry. or both may lead to similar values for a ratio in functionally distinct forms (Emerson.0 was tested with a t-test in the form of: ts ¼ ðb À 1Þ=SEb where b. This technique reviews and selects variables for inclusion in the model that contribute most to discrimination among groups. Resultant discriminant functions were also used to classify the extinct rodent species into locomotor groups. HL..05 level (Table 4). In addition to extinct rodents. semiaquatic and arboreal taxa were included. The null hypothesis of b 5 1. slope. were included as unknowns in the classification phase of the discriminant analysis. Pph3t. FL. a fundamentally different mode from hind limb or tail paddling locomotion seen in most other semiaquatic rodents (Nowak. and a 5 0. Mph3t. tibia length. Hydrochaeris hydrochaeris. Regression of log transformed raw variables (used to compute the indices) versus log GM scores can be used to examine the influence of the numerator or denominator on a functional index. HEB. pes digit 3 terminal phalanx length. 1. humeral epicondylar breadth. SEb. 1999). tibia mediolateral diameter. Lessa and Stein.0. shortening a proximal segment (without a change to the distal segment) and elongating a distal segment of a limb (without a change in the proximal segment) could produce equal values for an index but with distinctly different consequences for the function of that limb. functional ulna length. 1985). RESULTS Allometry The possible influence of allometry was assessed using regressions of log transformed measurements against the log GM score (a measure of body size) for each individual. ulna mediolateral diameter.05. only seven of the surveyed extinct species were complete enough to be included in this step of the analysis (Table A3). RL. Stepwise discriminant function analysis (DFA) was used to determine linear combinations of variables that maximize separation among rodent taxa belonging to the seven locomotor groups. humerus length. Fig. Statistical analyses were performed using SPSS 13. UMLD. in clear violation of the assumption of mutually exclusive groups in DFA. For example.f. FUL. FEB. 1988. 5 n 2 2. Capybaras were not included in construction of the model as they are known for both cursorial and semiaquatic habits.LOCOMOTOR ADAPTATIONS IN RODENTS 1389 ´ 1992. Nonrodent species were chosen to represent a diverse array of locomotor types. The functional indices and GM-transformed shape variables were tested for significant differences among locomotor groups using multivariate analysis of variance (MANOVA) with Scheffe’s F and Tamhane’s T2 procedures used for post hoc comparisons. These tests were chosen because they are commonly used for these types of ecomorphological analyses and have been effectively used to study the locomotor specializations of other rodents (for examples see: Stein. whereas metatarsal three length showed a significant negative allomeTABLE 2. Osteological measurements used in the analyses Measurement Abbreviation HL HMLD DPCL HEB RL FUL UMLD ULOL MC3L Mph3p Mph3t FL FAPD FGT FEB TL TMLD TSL MT3L Pph3t Nielsen. metatarsal 3 length. HMLD. TMLD. greater trochanter height. femur length. Greatest length of the humerus Midshaft mediolateral diameter of the humerus Length of the deltopectoral crest Epicondylar breadth of the distal humerus Greatest length of the radius Functional length of the ulna Midshaft mediolateral diameter of the ulna Length of the olecranon process of the ulna Greatest length of metacarpal 3 Greatest length of proximal phalanx of digit 3 of manus Greatest length of terminal phalanx of digit 3 of manus Greatest length of the femur Midshaft anteroposterior diameter of the femur Height of the greater trochanter of the femur Epicondylar breadth of the distal femur Greatest length of the tibia Midshaft mediolateral diameter of the tibia Length of tibial tuberosity Greatest length of metatarsal 3 Greatest length of terminal phalanx of digit 3 of pes Measurements used are illustrated in Figure 1. capybaras use all fourwebbed feet when swimming. Detailed descriptions of measurements are included in Table 2. DPCL. but not forelimb dominated swimmers or brachiators). FGT. manus digit 3 proximal phalanx length. 1997). but still consistent with locomotor modes of the rodents studied (i. ULOL. femur anteroposterior diameter. standard error of the slope. 1993. TL. FAPD. MC3L. Elissamburu and Vizcaıno.e. measurement. Indicates relative proportions of proximal and distal elements of the hind limb. Functional lengths of the humerus and radius divided by lengths of the femur and tibia [(HL 1 RL)/(FL 1 TL)].024 0.542 0.866 0. SEb. a.946 0. Indicates the size of manual claws relative to the pedal claws. Indicates relative mechanical advantage of the gluteal muscles used in retraction of the femur. Manus digit 3 proximal phalanx length divided by metacarpal 3 length (Mph3p/MC3L).996 0. standard error. Epicondylar breadth of humerus divided by functional length of the humerus (HEB/HL).060779 0. Indicates relative proportions of proximal and distal elements of the manus and size of the palmar surface.881 0. Functional length of the tibia divided by functional length of the femur (TL/FL).118864 0.958 1.171443 0. Indicates robustness of the ulna and its ability to resist bending and shearing stresses. r2.756 0. and supinators. Journal of Morphology .105 0.114637 0.084444 0. Indicates relative proportions of proximal and distal elements of the hind limb. and relative size of the hind foot.060 1.339 20. Significant deviations from isometry (b 5 1) at the P > 1 for positive allometry and b < 1 for negative allometry.066949 0.180 0. and supinators.050411 0.X.060284 0.089 0. their definitions. Olecranon process length divided by functional length of the ulna (ULOL/FUL).966 0.948 0.085089 0.143061 0. slope. Indicates relative area available for the origins of the forearm flexors.593 0.843 20.891 0.1390 J. Morphological indices used in analyses.112097 0.061814 0.426 20.912 0.098 1. Indicates robustness of the femur and its ability to resist bending and shearing stresses (AP diameter is used due to transverse expansion of the femora in semiaquatic rodents).981 1. Indicates robustness of the tibia and its ability to resist bending and shearing stresses. x. and relative area available for the origin and insertion of forearm and manus flexors.840 20.717 20. VAN VALKENBURGH TABLE 3.060563 0. Indicates robustness of the humerus and its ability to resist bending and shearing stresses. Mediolateral diameter of tibia divided by functional length of the tibia (TMLD/TL). b.161235 0.045 1.888 1.944 0.940 0.939 0. Anteroposterior diameter of femur divided by functional length of the femur (FAPD/FL).526 0.103 0. 0.141 20. Mediolateral diameter of humerus divided by functional length of the humerus (HMLD/HL). Manus digit 3 terminal phalanx length divided by pes digit 3 terminal phalanx length (Mph3t/ Pph3t).247 0.056372 0. Functional length of the radius divided by functional length of the humerus (RL/HL).926 0.077332 0. Mediolateral diameter of ulna divided by functional length of the ulna (UMLD/FUL). Indicates relative proportions of proximal and distal elements of the forelimb.726 0.021 0.057 20. Indicates relative mechanical advantage of the hamstrings and biceps femoris muscles acting across the knee and hip joints.608 20. Indicates relative mechanical advantage of the triceps brachii and dorsoepitrochlearis muscles used in elbow extension.178 b 1. pronators. Metatarsal 3 length divided by functional length of the femur (MT3L/FL).078293 b51 b b b b b b b b b b b b b b b b b b b b 51 51 51 51 51 51 51 51 51 51 51 51 51 51 >1 51 51 51 <1 51 Regression equations were calculated in the form log y 5 log a 1 b log x. Length of distal extension of the greater trochanter of the femur divided by functional length of the femur (FGT/FL). and inferred functional significance Index Shoulder moment index (SMI) Brachial index (BI) Humeral robustness index (HRI) Humeral epicondylar index (HEB) Olecranon length index (OLI) Ulnar robustness index (URI) Manus proportions index (MANUS) Claw length index (CLAW) Crural index (CI) Femoral robustness index (FRI) Gluteal index (GI) Femoral epicondylar index (FEB) Tibial robustness index (TRI) Tibial spine index (TSI) Pes length index (PES) Intermembral index (IM) Definition Deltopectoral crest length divided by functional length of the humerus (DPCL/HL).078398 0. This is identical to the index of fossorial ability used by Hildebrand (1985). pronators. Epicondylar breadth of femur divided by the functional length of the femur (FEB/FL).961 0.833 0.018 r2 0. Indicates the length of the forelimb relative to the hind limb.120 1.313 0.094720 0. SAMUELS AND B.102 0.049 1. TABLE 4.019 1. Measurements used to calculate indices are illustrated in Figure 1 and described in Table 2. Indicates relative area available for the origins of the gastrocnemius and soleus muscles used in extension of the knee and plantar-flexion of the pes. Indicates mechanical advantage of the deltoid and pectoral muscles acting across the shoulder joint.599 20.819 0.916 SEb 0. GM score. y.05 level are indicated with b correlation coefficient. Length of distal extension of the tibial tuberosity (spine) divided by functional length of the tibia (TSL/TL).931 0.509 0. Interspecific allometric relationships for log transformed measurements regressed against body size (log GM) Measurement (y) Humerus length Humerus ML diameter Humeral epicondylar breadth Deltopectoral crest length Radius length Functional ulna length Ulna ML diameter Olecranon process length Metacarpal 3 length Manus proximal phalanx length Manus terminal phalanx length Femur length Femur AP diameter Greater trochanter height Femoral epicondylar breadth Tibia length Tibia ML diameter Tibial tuberosity length Metatarsal 3 length Pes terminal phalanx length a 0.546 20.671 1.942 1.851 0. y intercept.962 0.002 1.149 0.094253 0.073 0. F.170 0. manus proportions index. Sa.023)Sa.R.Gl 0.Sa.A. MANOVA found all groups to be significantly different (P < 0.Sf.Gl (0.F 1. 53 SMI BI HRI HEB OLI URI MANUS CLAW CI FRI GI FEB TRI TSI PES IM 0.0).016)T.R.R (0.057)T.062)T.R 0.Sf.0).Gl 0.Sa.014)T.Gl 0.F.F.010)Sa. longer distal hind limb elements (high CI and PES).Sf. and some of these are summarized as follows.181 (0.082)A.Sf.Sa. Semifossorial rodents showed relatively short antebrachii (low BI). and FRI). and TSI).800 (0.032) T.Gl 0. PES.F (0.A.739 (0. semifossorial.009)Sa.Sf.057 (0.R. ulnar robustness index.F.005)T. intermembral index).Gl 1. CI.Sf.A.F.R 0.072)A.R.504 0. MANUS.Gl 0. F. The number of species and individuals sampled are listed below each category. fossorial.F.996 0. low TRI and TSI).Gl 0.129 0. Sf.R. and enlarged muscular attachments (high GI.Gl (0.219 (0.A.A.014)T.R.310 (0.104 (0.A. CLAW.Sa.A.F. n 5 9. Arboreal rodents display elongate humeri and hands (low BI and high MANUS).054 (0.Gl 0.073)A.008)Sa.Gl 0.Sf. TSI.Sf. 38 0.Sa. and TSI).Gl 0.539 (0.Gl (0.012)Sa. and enlarged manus terminal phalanges (CLAW >1.094 (0. including: enlarged muscles or greater mechanical advantages of muscles (high SMI.416 0.F.416 (0.005)T.435 (0.328 (0.803 (0. elongate tibiae (high CI. brachial index. femoral epicondylar index.F.015)R.Gl 0.931 (0.F.Sa.019)T. Mean values and standard deviations of indices for each locomotor group Semiaquatic.051)T. elongate hand (high MANUS).208 (0. but also reflected in low SMI.013)T. n 5 16. proximal muscle insertion (low TSI).R.072)T.F.Sf.043 0.050)F.016)R.024)T.R Stepwise DFA was performed using the same data set as previous analyses. relatively equal limb lengths (IM closer to 1.Sf. and equal claw lengths (CLAW 5 1.027)T. and disproportionately long hind limbs (IM <0.001).Sf.039)F.Gl 0.Gl 1.R.452 (0.524 (0.F. Our findings are consistent with the pattern of geometric similarity commonly found in smaller mammals (Biewener.079) A.474 (0.R.F.051)T.023)T. terrestrial.336 1.R.339 (0.076 (0.Sa.268 (0.015) Sa.080)T.112 (0.F (0. Ricochetal rodents were characterized by short humeri (high BI).411 (0.361 (0.Sf.F. scansorial/arboreal.018)T.R (0.Sf.307 (0. F.069)T.086 (0.Gl 0.048) Sa.Gl 0. FEB.F. Semiaquatic rodents were characterized by relatively robust limbs (high HRI and FRI).930 (0. n 5 4.R 0.F.220 (0.Gl 0.F.Sf.A.443 (0.021)Sa. 27 0. A. OLI.R.A.Sa. tibial spine index.022)Sa.Sf.007)T. crural index.017)T. FRI.R.Sf.Sf. Variable Terrestrial.Sf.Sa.R (0. n 5 14.Sa.F.Gl 0.247 (0.Gl 0.854 (0.024)T.Gl (0.079) Sa.Gl 0.271 (0.045)Sa.Gl 0.116)T.196) T.A.Gl (0.F 0. elongate hind foot (high PES).055 (0.062 0.015)T.025)Sa.192 0.093)Sa.072 (0.R.079 (0.463 (0.R.A.033)T.R. 1990).Sf.F. species averages for each index are included in Table A4).Sa. URI.067 0.036)T. Fossorial rodents display many significantly different features from other groups.092 0.Sa.R (0.A.A.A.Sf. Gliding rodents possess elongate.Gl (0.162 0.245 (0.019)T.F.138 0.R.R.056 0.592 (0.079)T.018)T.Gl 0.R 0.063)A.578 (0.033)T.R 0.Sf.Sa.057)T.099)F 1.R.A.Sf.0).F.F. with the addition of extinct rodent taxa as unclassified cases.Gl 0. HEB.F.573 (0. GI.F. FEB.A.086)A.156 (0.Sa.620)T.F (0.876 (0.Gl 0. pes length index.Gl 1.Gl 0.Sf.Sa.R.Gl 0.046 (0.F. tibial robustness index.A.Gl 0.R.F.Sa. humeral epicondylar index.F 1.R (0.015)T. robust limbs (high HRI.Sf.F.A.R.F.378 (0.144)Sf.112 (0.Sa.086 0.A.086)F (0.083)T.A.A.049)T.A.R 0.007)Sa. 46 Semifossorial.R.Gl 0.055 (0.Gl 0.125 (0.069 (0.R.624 0. enlarged olecranon processes (high OLI).012)Sa. URI.F.Sf.Gl 0.Sf.R (0.5 on average).Gl 0.840 (0.Sf.A. as none of the species studied are particularly massive.081)T.A.Sa. equal claw lengths (CLAW 5 1.012) Sa.Gl 0.062) F.050)T.Gl 0. HEB. enlarged olecranon processes (high OLI).090)T.368 (0.032)Sa.908 (0.Gl 0.067 (0.Gl (0.R (0.0).F.114)A.Gl (0.Gl Journal of Morphology Each index is defined in Table 3 (SMI.218 (0.Gl (0.Gl 0.Gl 0. gracile limbs (low HRI. Gl.Gl 1.046) T.048) T.5 on an average). .R (0.Sa.R 1. TSI).Sf.Gl 0.789 1.Gl 0.A. IM.021 0. 18 (0.Gl 1. TABLE 5.049)A.R (0.008)T.R (0.A.092 0.A.A.073 (0.Sf.Gl 0.Sa. changes in limb posture and muscle mechanical advantages can compensate for increasing size without strong skeletal allometry.116 (0.Gl 0. BI.Gl 0.026)Sa.Gl 0. humeral robustness index.Gl 0.Gl (0.Sa. shortened antebrachii and hands (low BI and MANUS).283)T.F.Sa.Sa.F. FRI.099)T.F.Gl 0.071 0.F.R.084 0. FEB.075)R. n 5 9.016)Sa.013)F. olecranon length index.Sf.R Ricochetal.Sa.F. Significant differences between groups in univariate ANOVA tests (at the P 0. and relatively equal limb lengths (IM closer to 1.080 (0.Sf.R.F.Sf.137)Sf.0).F.068)T.Gl 0.Sf.F.Gl 0.F.Sa.Sf.Sa.Sf.060)Sa.395 0.F.087 (0.059 0.004)T.F.F.Sa.F 0.Gl 0.R Arboreal.057 (0.119 (0.Sa.Gl (0. Numerous significant differences in functional indices distinguish locomotor groups (Table 5).F. HEB. Over the range of body mass included in this study.F. dramatically enlarged manus terminal phalanges (CLAW >1.F.095 (0. Absence of interspecific allometry is not surprising.059)T.086)T.068)T.Sa.011)T.Sf.R.247 0.A.148 (0.Sf.073)Sf.A.R 0.Sa. GI.R.R (0.573 (0.421 (0.Gl 0.Sf.Gl 0. claw length index. gluteal index.R.Gl 0. and equal limb lengths (IM close to 1.045 (0.F.062)Sa.Sa.004)T.Gl 0.617 (0.Gl 0.022)Sa.F.Sf.921 (0.F.763 (0.886 0.081)T.090)T.A.210)Sf.105 (0.A. n 5 7.355 (0.014) R. GI.R 0.254 (0.F.Sf.105 (0.Gl 0.Sf.009)Sa.146 (0.A.Gl 0.013)Sa.Gl 0.R.006)F.A.721 (0.813 Gliding. shoulder moment index. 44 Fossorial.Sa. ricochetal.F.Gl 0.05 level) are indicated by: T. URI.Sf. OLI.977 1.F.011)Sa.129)A.327 0.042)T.312 0.A.F.289 (0.032)T.F.F.Sa.A.089 (0.R. R. gliding.A. n 5 8. TRI.Gl 0. 67 0.115 (0.A. femoral robustness index.Sa.R (0.0).R.Sa. and TRI. This analysis was run separately for functional indices LOCOMOTOR ADAPTATIONS IN RODENTS 1391 Mean values and standard deviations of functional indices were calculated for locomotor groups (Table 5.Sf.F.165)T.089) T.Gl 0.F.Sa.733 (0.Sa.066)A. semiaquatic.012)T. HRI.179 0.Gl 0.Gl 0. FEB. OLI.R.054)T.091)T.Gl 0.A.Sf.R (0.013)T.Sf. Differences for individual indices were assessed by univariate ANOVAs with Scheffe’s F and Tamhane’s T2 post hoc procedures.524 (0.F 0.Gl (0.447 (0.Sf.050)Sa.045 0.Sa.F (0.DFA Analysis of Variance try.094 (0. 330 20.110 0.515 0.243 0. 2) and both showed features that facilitate climbing. FRI.261 1. intermembral index).8 97.128 0. Discriminant analysis classification matrix of rodent taxa Predicted Group Observed group Original Terrestrial Semiaquatic Arboreal Semifossorial Fossorial Ricochetal Gliding Total Terrestrial Semiaquatic Arboreal Semifossorial Fossorial Ricochetal Gliding Total % Correct 86.105 0. VAN VALKENBURGH TABLE 6. the DFA showed good separation of groups and was significant (Wilks’ k 5 0.221 20.171 4.284 0. OLI. this was primarily due to TABLE 7. and negatively correlated with manus proportions (MANUS).461. Each index is defined in Table 3 (SMI.0 91. large olecranon processes (high OLI).093 0.145 0.000. Some ricochetal rodents also had positive scores for DF2.494 0. The analysis yielded three discriminant functions with eigen values >1 which accounted for 90.053 0.0 100. The second discriminant function (DF2) accounted for 27.076 0.8 86.101 0. The first discriminant function (DF1) accounted for 54. and thus is not influenced by body size. and some terrestrial taxa showed negative scores for DF1 reflecting their hind limb dominated locomotion. crural index. Ricochetal.1392 J. F(6. and GM transformed data. IM. gluteal index.0 92. claw length index.162 0.338 0.028 0. TRI. P 5 0. characterized by elongate hind limbs (low IM) and distally elongate hind limb elements (high CI and PES). SAMUELS AND B. manus proportions index. URI.494 0. eigenvalues.7% of total variance. CI.534 0. and robust forelimb elements (high HRI and URI).0). HRI.1% of the variance and was positively correlated with intermembral index (IM) and negatively correlated with brachial index (BI).8 95.8 90. PES.5% of variance and was positively correlated with ulnar and humeral robustness (URI. and relative hind foot length (PES). olecranon length (OLI). GI. tibial spine index.242 0.001).090 0. femoral robustness index.242 20. shoulder moment index. fossorial. reduced manual phalanges (low MANUS).861 81. humeral robustness index.156 20. however. humeral epicondylar index.4 94.189 20.99). 2 and 3) reflecting their tendency to use the limbs equally or show forelimb dominated locomotion.514 0.474 0. and proportions of variance explained by each function Discriminant function 1 SMI* BI HRI HEB OLI URI MANUS CLAW CI GI FRI* FEB TRI TSI PES IM Eigenvalue cumulative (%) Variance 0. as well as nearly equally proportioned proximal and distal limb segments (BI and CI). distal elongation of the manus (high MANUS). semiaquatic. including elongate humeri and ulnae (reflected in low HRI.131 20.269 0.8 86.7 86. brachial index.0 100.7 Indices with asterisks were not included in the stepwise discriminant function model.061 0. DF1 is not correlated with GM values (r2 5 0. results did not differ appreciably and only the more easily calculated and interpreted indices are discussed here.237 0. HEB.165 20. HEB.110 0.249 0.383 0.X.014 0.257 0. and URI scores).576 54. pes length index. CLAW. Discriminant analysis structure matrix.8 Terrestrial 46 5 0 1 0 0 0 52 46 5 0 2 0 0 0 53 Semiaquatic 0 33 0 0 0 0 0 33 0 33 0 0 0 0 0 33 Scansorial/ arboreal 0 0 45 2 0 0 0 47 0 0 44 2 0 0 0 46 Semifossorial 7 0 1 40 4 0 0 52 7 0 2 38 4 0 0 51 Fossorial 0 0 0 1 63 0 0 64 0 0 0 2 63 0 0 65 Ricochetal 0 0 0 0 0 27 0 27 0 0 0 0 0 27 0 27 Gliding 0 0 0 0 0 0 18 18 0 0 0 0 0 0 18 18 Crossvalidated Journal of Morphology .8 86.006 0. As expected from the great differences between some of the locomotor types examined. Fossorial taxa had positive scores for DF2 and displayed relatively broad humeral epicondyles (high HEB).367 20. Arboreal and gliding rodents showed strongly negative DF2 scores (see Fig. HRI. and reduction of the olecranon process (low OLI). olecranon length index.0 100. ulnar robustness index.0 100. Fourteen of the 16 indices were included in the stepwise discriminant model (Tables 6–9).002.175 20.227 20.631 9.9 94.297 0.237 0.055 0. and gliding taxa tended to have positive scores for DF1 (Figs. BI. crural index (CI). HEB). Arboreal. tibial robustness index. TSI.619 90.394 0.276) 5 36. P < 0.290 0.5 3 0. FEB. MANUS. characterized by forelimbs and hind limbs of similar length (IM 5 1.1 2 0. femoral epicondylar index. semiaquatic. Extinct species are indicated by y.000 0. given membership in the most likely group.000 0.000 0. ricochetal. gliding. 3). Sf. and only the terrestrial and semiaquatic groups had <90% correct classification. P(G/D) represents the posterior probability that a case belongs to the predicted group. The ability of the discriminant model to separate taxa into locomotor groups was assessed using the classification phase (in which individual specimens are excluded from creating the functions. Gl.000 0.901 2nd Most likely group A T A T F F A Species classifications are indicated by: T.000 1. Sf. P 5 0. and is not influenced by body size.994 1. Discriminant analysis classification of other mammalian orders Species Hydrochaeris hydrochaeris Cynocephalus volans Macropus robustus Dasypus novemcinctus Choloepus didactylus Mephitis mephitis Ailurus fulgens Procyon lotor Mustela frenata Neovison vison Lontra canadensis Taxidea taxus Gulo gulo Phoca vitulina Sorex vagrans Scapanus townsendi Actual group T/Sa G R F A Sf A T T T Sa Sf T A T F Most likely group Sf G Sa F T Sf A T A Sf Sa F Sf Sa F F P(D/G) 0. terrestrial.000 0.LOCOMOTOR ADAPTATIONS IN RODENTS TABLE 8.086 0. Discriminant analysis classification of extinct taxa Species Castor californicusy Dipoides stirtoniy Procastoroides idahoensisy Castoroides ohioensisy Palaeocastor fossory Palaeocastor nebrascensisy Paenemarmota barbouriy Most likely group Sa Sa Sa Sa Sf Sf Sf P(D/G) 0. Sa. terrestrial.079 P(G/D) 1.005 0.000 P(G/D) 0. Arvicola terrestris. showed misclassification of both individuals used in the analysis as semifossorial.8% correct classification when cases were cross-validated. F. P(D/G) represents the conditional probability of the observed discriminant function score. gliding.849 1.999 0.880 1.001 0. DF3 distinguished semiaquatic rodents.998 0. scansorial/arboreal.000 0.000 0. The third discriminant function (DF3) accounted for 9. P < 0.05). Dinomys branickii.004 0. three taxa were consistently misclassified by the discriminant analysis. given the sample used to create the discriminant model.000 1. the European water vole. Hind limb paddling locomotion of semiaquatic rodents demands adaptations to minimize drag and maximize thrust.010 0.930 0. However.000 0. from all other groups (see Fig. P(D/G) represents the conditional probability of the observed discriminant function score. and DF3 is weakly correlated with GM (r2 5 0. The terrestrial pacarana.1% of variance. This classification showed 92.000 0.998 1. ricochetal.000 0.8% correct classification of individuals. Sa. which tended to have positive scores for DF3. such as shortened femora (high FEB) and enlarged hind limb musculature (high FEB and TSI).512 0.836 0.997 0.504 0.011 0. fossorial. were misclassified by the discriminant analysis as arboreal rather than terrestrial. R. Journal of Morphology . Most misclassifications (11 of 21) were of individual specimens rather than entire species. Gl. All individuals of the grasshopper mouse. scansorial/arboreal. but are instead classified using models derived from the remaining specimens) (Table 7). DF3 scores tended to be higher in larger semiaquatic species.002.047 0. TABLE 9.000 0.000 0. R. DF2 was not correlated with GM (r2 5 0. Onychomys leucogaster.000 0.000 2nd most likely group T T R Sf F F Sf Sf Sf T A A F R Sf Sf 1393 Nonrodent taxa were excluded from the discriminant model formation. semifossorial.001 0. P(G/D) represents the posterior probability that a case belongs to the predicted group. semiaquatic. and it was primarily associated (and positively correlated) with FEB and tibial spine length (TSI).106 0. fossorial.067. as well as 91.000 0. given membership in the most likely group. F. A. A. given the sample used to create the discriminant model. had all 3 individuals misclassified as terrestrial rather than semiaquatic.47).000 0.990 0.004 0. semifossorial. Species classifications are indicated by: T.748 0.702 0. shortening of the humerus (high HRI and HEB) and collinearity in the data set (some indices that are correlated with DF2 were colinear with PES and IM).508 0. Ricochetal and gliding groups had 100% correct classification. . All 10 individuals of the cursorial and semiaquatic capybara. Castoroides. fossor. four were classified as semiaquatic (Dipoides. VAN VALKENBURGH Fig. SAMUELS AND B. Hydrochaeris hydrochaeris. Individual specimens for each species were collapsed to a single point. and Paenemarmota barbouri). Of these species. but on the periphery or outside of the observed morphospace for that group (low conditional probability). 15 nonrodents) included in the classification phase of the analysis as unknowns produced mixed results (Table 8). and Castor californicus) and three were classified as semifossorial (Palaeocastor nebrascensis.1394 J. 2. The 16 extant species (1 rodent. were incorrectly classified as semifossorial. Plot of first and second discriminant function scores for rodent locomotor types. This pattern can result from the unknown taxon being closest to the centroid for a group (high posterior probability). Classifications of some unknown taxa (both extant and extinct) resulted in high posterior probabilities and low conditional probabilities (Tables 8 and 9). Numbers associated with each point identify individual species (Table A1). but some of those correctly classified showed discriminant function scores well outside the range of the sample used to create the discriminant model. Eight were correctly classified. Six extinct species from the Family Castoridae and the extinct giant marmot Paenemarmota barbouri were complete enough to be included as ungrouped cases in the classification phase of the Journal of Morphology analysis (Table 9).X. P. Procastoroides. Bivariate plots include the linear measurements (log transformed) for each of the functional indices. Semifossorial and fossorial rodents had significantly longer olecranon processes than other rodents. Fig. with values tending to be <1 (Table 5. whereas low scores in semifossorial and fossorial rodents were related to shortening of the antebrachium. and fossorial rodents had lower BI scores than the other groups. 4a). plotted with the numerator (on the y-axis) against the denominator (on the x-axis). however. Plot of first and third discriminant function scores for rodent locomotor types. Arboreal. often represented by incomplete specimens. bivariate plots. 3. Bivariate Plots To further examine morphological differences between locomotor groups. Fig. 4b). and linear regressions are included for the nine indices with significant discriminating power. The semiaquatic Castor and its extinct relatives also showed particularly large humeral epicondyles. Bivariate plots facilitate visual comparisons across taxa and are especially useful for inferring habits of extinct taxa. semifossorial. Numbers associated with each point identify individual species (Table A1). Individual specimens for each species were collapsed to a single point. Regression of humerus and radius length versus the GM scores revealed low BI scores in arboreal rodents were related to elongation of the humerus. many larger semiaquatic rodents showed similar OLI Journal of Morphology . Fossorial species had significantly broader humeral epicondyles than other rodent groups (Table 5.LOCOMOTOR ADAPTATIONS IN RODENTS 1395 Fig. 142. scores (Table 5. Regression line: y 5 20.782 1 1. g: Tibial spine index (TSI).053.928 x.05 level. Cursorial taxa would presumably show low scores for this index due to elongation of the metacarpals. d: Manus proportions index (MANUS). Dashed reference line represents equal proximal and distal proportions: y 5 0 1 1 x. Numbers associated with each point identify individual species (Table A1).943 x.1396 J.067 x. 4. Regression line: y 5 20. Fig. with the y-axis representing the numerator and the x-axis representing the denominator.969.X. Fig.791. Correlation coefficient r 5 0. Regression line: y 5 20. . Regression line: y 5 20.434 1 1.097. c: Olecranon length index (OLI). Standard error of the estimate 5 0.116 1 0. h: Pes length index (PES).897 x.915 x. Standard error of the estimate 5 0.157 1 0. Fig.099.109. Regression line: y 5 0. SAMUELS AND B. Correlation coefficient r 5 0. Regression line: y 5 0. Standard error of the estimate 5 0. Correlation coefficient r 5 0.920. Regression line: y 5 0.181 1 0.173.557 1 0. Standard error of the estimate 5 0. VAN VALKENBURGH Fig. f: Femoral epicondylar index (FEB).931.734 x. b: Humeral epicondylar index (HEB). 4c). Correlation coefficient r 5 0. 4d). e: Crural index (CI). resulting in greater scores for relative to other groups (Table 5.978.944. a: Brachial index (BI). Units are in log (mm). Correlation coefficient r 5 0.087. Correlation coefficient r 5 0. Dashed reference line represents equal proximal and distal proportions: y 5 0 1 1 x.053 1 0. Regression line: y 5 20. Correlation coefficient r 5 0.060. Phalanges were relative to metacarpals in gliding and rodents.962 x. Standard error of the estimate 5 0. Standard error of the estimate 5 0. Standard error of the estimate 5 0.804.439 1 0. Log/log plot of ratio components.014 x. Correlation coefficient r 5 0. Individual points represent the average for each species. 4d). Journal of Morphology elongate arboreal MANUS MANUS scores were particularly small in fossorial rodents due to distal shortening (Table 5. Standard error of the estimate 5 0.937. Slopes for all regressions are significant at the P 0. with more pronounced tibial elongation (see Fig. 4e). 5a. The similar CI values in these groups were due to fundamentally different morphological features. Colomys goslingi. and thus using only this index to infer fossoriality is not recommended. Because of pronounced shortening of the femur as well as enlarged femoral epicondyles semiaquatic and fossorial rodents had significantly greater values for FEB than all other rodent Journal of Morphology . but a significantly lengthened tibia. One exception to this is the African water rat. 5). Fig. Ricochetal rodents are characterized by elongation of both the femur and tibia relative to body size. Ricochetal and semiaquatic rodents both had relatively high values for the CI.LOCOMOTOR ADAPTATIONS IN RODENTS 1397 Figure 4. On the other hand. (Continued). semiaquatic rodents showed shortening of the femur relative to body size and the expected tibia length of a rodent their size. (no. Other rodent groups studied tended to have more equally proportioned proximal and distal elements. 11 in Fig.b) which displayed the expected femur length of a rodent its size. indicating relatively longer distal elements (tibiae) than proximal elements (femora) in the hind limbs (Table 5. Finally. and many fossorial taxa.X. The length of the tibial tuberosity (spine) relative to tibia length was significantly shorter in ricochetal and gliding rodents than in all other groups. Differences between the locomotor modes studied are great enough to readily discriminate groups and accurately classify group membership. dig. 4g and 5b). b: Tibia length. fossorial. Finally. some arboreal rodents (porcupines and South American climbing rats). The DFA showed good separation of locomotor groups studied here (Figs. 4h). Distantly related rodents surveyed in this study that have similar locomotor behaviors generally show convergent morphological characters. as a function of tibial elongation (Table 5.922. including CI. Because the ultimate goal of this study is inference of extinct species’ locomotor habits. SAMUELS AND B. Figs. 2 and 3). This separation was related to shortening of the femur and enlarged attachments of hind limb muscles. consequences of this can be seen in Figure 4b–d.969.094. 4f and 5a). the folJournal of Morphology lowing discussion will begin by covering which features can be used to discriminate groups and how accurately these features classify living species. Castor).888 x. Statistical Analyses Both multivariate analyses and bivariate plots revealed correlations between skeletal form and locomotor function in rodents. we discuss how each group of specialized rodents compares to their more generalized terrestrial counterparts and assess the functional implications of group differences. they can climb. Figs. Numbers associated with each point identify individual species (Table A1). Log/log plots of femur and tibia lengths versus geometric mean scores. we discuss what application of these methods reveals about evolution in some extinct rodents. a: Femur length. IM. Standard error of the estimate 5 0.1398 J. Next. Elongation of the limbs in gliding rodents separates them from other groups. This function is primarily related to limb proportions.. Individual points represent the average for each species. Correlation coefficient r 5 0. DISCUSSION The average rodent is capable of an impressive array of locomotor behaviors. and gliding taxa from the hind limb dominated semiaquatic and ricochetal taxa. Standard error of the estimate 5 0. Manus proportions and robusticity of the limbs were linked to separation along this axis. Regression line: y 5 0. had significantly greater relative pes lengths than the other locomotor groups (Table 5. 5. Nevertheless. Higher values for TSI were seen in large bodied semiaquatic rodents (e.843 1 0. groups (Table 5.g.717 1 0. Correlation coefficient r 5 0. and relative pes length. Ricochetal rodents. and to a lesser degree semiaquatic rodents. many locomotor specialists have evolved (often in independent lineages) and can be found in nearly every terrestrial habitat. Consistent differences between locomotor groups can be used to accurately classify the locomotion of .f. discriminant function 3 separated semiaquatic rodents from all other groups. Discriminant function 1 separated forelimb dominated arboreal. Regression line: y 5 0. and swim without extensive morphological specializations. Discriminant function 2 separated climbers and gliders from more terrestrial and fossorial taxa. VAN VALKENBURGH Fig. Fig.958 x.g.062. Taxidea taxus. (the striped skunk). Misclassification of all individuals of the grasshopper mouse. was correctly classified as gliding and possesses the elongate. positions of these taxa (plus the river otter Lontra) relative to one another in shape space are similar to those seen in comparable rodents. respectively. were both correctly classified as fossorial. but with a centroid displaced in shape space relative to rodents. were both classified as semiaquatic. Macropus robustus.3 compared to the average of 1. as was also the ´ case in Elissamburu and Vizcaıno (2004). Onychomys leucogaster. but this species fell well outside the range of discriminant function scores seen in rodents. the use of both the fore and hind limbs to displace water may explain their classification as semifossorial. Dasypus novemcinctus. Phoca vitulina. is very similar to the arboreal rodents in most features studied. gracile limbs characteristic of rodent gliders. Limb proportions in capybaras differ from the more common hind limb paddling semiaquatic rodents included in the DFA in several ways. and more equally proportioned fore and hind limbs (IM % 1. the highly fossorial mole. was misclassified as fossorial due to relatively high shoulder moment index. capybaras are very large rodents that both swim and run. and terrestrial. and Procyon lotor (the raccoon) were correctly classified as semifossorial. This may be partly linked to the size of water voles. Lontra canadensis. and the semiaquatic Lontra had relatively lower discriminant function 1 and higher discriminant function 3 scores. Sloth hands display particularly short proximal phalanges and elongate middle phalanges. Although they rarely dig. the European water vole. as a way to accommodate both larger body mass and stresses placed on the bones during running and swimming. included as unknowns in the DFA were classified as semifossorial based on their limb proportions and robusticity. dis- play some differences from the gliding rodents. 1999). while the semifossorial Taxidea had higher discriminant function 1 and discriminant function 2 scores. as arboreal is likely due to its specialized carnivorous/insectivorous diet. Sloths are also atypical climbers in that their body is suspended below the limbs (Adam. The terrestrial Mustela. was misclassified as semifossorial. and relatively shorter metatarsals relative to femur length (pes length index). Neovison. resulting in particularly high CI and femur epicondylar index scores. Members of other mammalian orders included as unknowns in the DFA were correctly classified in half of the cases.3 in hind limb paddlers). but enhanced to a greater degree. Sorex vagrans. Compared with the terrestrial shrew. but an alternative explanation is that conflicting specializations for aquatic and fossorial habits result in the absence of pronounced skeletal specializations in Arvicola. Cynocephalus volans. Hydrochaeris hydrochaeris. The mustelids Mustela frenata. This suggests similar evolutionary trajectories for locomotor specializations in this family. it has relatively longer radii (higher BI). Colugo hands have relatively shorter proximal phalanges and more elongate long middle phalanges than those of gliding rodents. Onychomys displays relatively large humeral epicondyles and elongate manual claws when compared with closely related terrestrial species. arboreal. Ailurus fulgens (the red panda). and Gulo had moderate scores. However. Relatively robust bones are also expected. however. Capybaras swim via quadrupedal paddling.0 compared to the average of 1. the shrew. Cynocephalus does. Phoca is fully aquatic but extended the trend toward femoral shortening seen in semiaquatic taxa. Confounding factors such as dietary habits and conflicting specializations for different locomotor modes should be considered. shows both aquatic and fossorial adaptations. The terrestrial pacarana. 1985). The 10 individuals of the capybara. and Gulo gulo were all misclassified. Mephitis mephitis. humeral epicondylar index.LOCOMOTOR ADAPTATIONS IN RODENTS 1399 individual species. Scapanus. and the mole. with features in Scapanus similar to those of fossorial rodents. however. The armadillo. the sloth was misclassified as terrestrial due to its rather low manus proportions index scores. but the systematic misclassification of a few taxa suggests caution is warranted. using all four legs for both activities. The primary reason for this misclassification was the high femur epicondylar index score of Macropus combined with its extremely high CI score (tibia more than 2x femur length). which facilitate the capture and grasping of prey. Neovison vison. but this is not surprising as the species has been documented to both dig and climb readily (Nowak. The discriminant analysis accurately classified extant rodents. Choloepus didactylus. but through modification of different elements (Mendel. Capybaras have a greater BI value ($ 1. Dinomys branickii. The macropodid marsupial. Similarly. Scapanus townsendi. was classified as semiaquatic rather than ricochetal. thus grasping is still facilitated by elongate digits. shorter proximal phalanges (lower manus proportions index). and the harbor seal. and olecranon length index scores. The river otter. but was classified as neither. The overall success of the discriminant analysis in classifying living species shows this method can be applied to fossil rodent species with some confidence. 1999).0). The two-toed sloth. Arvicola terrestris. with 93% of individuals correctly placed. The colugo.0 in hind limb paddlers) and much smaller CI value ($1. has far greater Journal of Morphology . Development of larger muscles and muscle attachments would facilitate propulsion of a large body mass on land and in the water. inference of locomotor habits from a single or a few measurements should only be done with great caution. and valvular ears and nostrils (Howell. may be related to their use of the forelimbs to handle wood and vegetation. and proportion of the limbs (Howell. Young. but these results suggest similar modifications of the limbs for a common function. The primary mode of swimming in rodents is dragbased and utilizes alternate paddling of the hind limbs. Fig. which facilitate digging as well as use of the forelimb in turning and keeping the head raised during swimming. which shows a negative allometry with body size. 1930. Ancestrally. Fish. 1988. which includes a power stroke and recovery stroke (Stein. thus increasing propulsive forces produced during swimming.X. femur robustness index. biceps femoris. the ability of this method to classify rodents suggests that application to other extinct mammals based on members of their own family or order may be similarly successful. which act in plantar flexion of the pes and are important in the power stroke. The shorter femur in semiaquatic species.. flexor digitorum group. Semiaquatic rodents in our study display relatively robust bones (high values of humeral and femoral robustness index). However. Reduction of the in-lever for the primary limb retracting muscles (i. VAN VALKENBURGH values for each of these indices and fell well outside the range of values observed for rodents. In semiaquatic species. and semitendinosus) may be compensated by increases in their size (femoral epicondylar index. femoral epicondylar index. increasing the surface area of the paddle. relatively short femora (indicated by high values of CI. and simultaneously minimizes induced drag by allowing the hind limb to be brought closer to the body in the recovery stroke (Stein. In beavers the medial epicondyle of the humerus is the origin of the flexor carpi ulnaris. 4c) indicates the presence of relatively large triceps brachii muscles. enlarged muscular attachments (olecranon length index. semiaquatic taxa are relatively more muscular and often exhibit skeletal differences related to the size. and thus the mainteJournal of Morphology nance of swimming speed through mechanical advantage of the limb retractors may be under less selective pressure than improving swimming efficiency through reduction of drag. Limb proportions of the ancestors of different mammalian orders were likely quite different. Semiaquatic rodents tend to use water for refuge rather than foraging (like many other secondarily aquatic mammals). as many features that distinguish locomotor groups are not exclusive to a single group. Castor. when compared with their terrestrial relatives. Our results are consistent with previous studies on rodents and other semiaquatic mammals and suggest that. Additionally. gluteals. semimembranosus. Tarasoff. Misclassifications observed here are likely results of the separate phylogenetic histories of these groups. The relatively large tibial tuberosity (tibial spine index) increases the area of insertion for the limb retracting semimembranosus. webbed feet. Fig. shape. SAMUELS AND B. 1988). and forearm pronators and supinators. reduces the mechanical advantage of muscles acting in the power stroke. 1937). digital flexors.1400 J. Precise handling of vegetation by beavers would be facilitated by enlarged carpal flexors. such features are not typically preserved in fossils. eulipotyphlans and rodents likely had very different limb proportions. 1996). Fig. as well as minimizing drag produced by the paddling limb during the recovery stroke. 1972. Adaptations to a semiaquatic existence include soft tissue features like a fusiform body shape. and femur epicondylar index). The enlarged hind foot (pes length index. the long olecranon process (olecranon length index. Increased femoral epicondyle (femoral epicondylar index) size in semiaquatic taxa increases the area of insertion for the limb retracting semimembranosus and also increases the areas of origin for the gastrocnemius and soleus muscles. 4h) of semiaquatic rodents increases the length of the paddling limb and also the size of the paddle. increasing thrust produced by the musculature (which aids in the power stroke). The relatively long olecranon process may also be linked to the presence and relatively large size of the anconeus and flexor carpi ulnaris muscles. and the pelvic head of the biceps femoris. 1988). however. The extensor digitorum longus also originates on the lateral epicondyle of the femur. 1930). 1994. semitendinosus. and thus application of our methods to infer the habits of a broader sample of nonrodent mammals is not recommended. Fig. whereas the lateral epicondyle is the origin of the supinator (Young. and elongate hind feet (pes length index) when compared with other rodents (Table 5). tibial spine index.g) to generate the necessary propulsive forces during the power stroke. 4f. and tibial spine index). 1937. Functional Analyses of Locomotor Modes Semiaquatic. and pronator teres. . 4b) of the beaver. This type of locomotion is facilitated by increasing the length of the paddling limb. The particularly large humeral epicondyles (humeral epicondylar index. palmaris longus. The anconeus acts as a forelimb extensor and rotator and may aid in turning while swimming or in the manipulation of aquatic vegetation (Stein. Semiaquatic mammals show an array of specializations to life in an aquatic environment while maintaining the ability to disperse across or acquire food on land.e. this muscle acts in toe extension and likely aids in maintaining the shape of the paddle. climbing rats. Van Valkenburgh. 4a). all of which aid in overcoming the greater drag associated with larger body size. Major limb elements of arboreal rodents are also relatively gracile (humeral. and. 4a). The olecranon process acts as the insertion for the elbow extending dorsoepitrochlearis. such as the deltoids which primarily protract the arm. 1987). epicondyles of the humerus. 1988). 1978. 1974. Enlarged muscle attachments in semifossorial rodents include the deltopectoral crest of the humerus. 1979. Arboreal rodents have relatively short olecranon processes of the ulnae (olecranon length index. pes length index) similar to terrestrial or fossorial rodents. 1985. the latissimus dorsi which retracts the arm. and sublimis) and the forearm flexing pronator teres (Holliger. equally proportioned limbs (IM). Consistent with their smaller size. which allows full extension at the elbow. it is not surprising that Castor is the largest hind limb paddling rodent and also displays the most pronounced aquatic specializations of any living rodent. 1994). 1985). but have been described as less structurally modified for climbing than other arboreal mammals (Cartmill. 5b). Stein. Arvicola terrestris. femoral. For example. Many features in the skeletons of arboreal rodents are consistent with those seen in arboreal marsupials and tree shrews (Argot. and enlarged appendicular muscles. 1972. features not measured in this study. While soft-tissue adaptations like fringe hairs and webbed feet may be sufficient in small rodents. but this is due to tibial elongation rather than femoral shortening (Fig. Hildebrand. vesper rats. 2002a. of the skeletal features that characterize the group in general. the pectoral muscles which adduct and retract the arm. other extant semiaquatic rodent species possess some. and erethizontid porcupines are all good climbers. 1981). 1985).LOCOMOTOR ADAPTATIONS IN RODENTS 1401 Stein. Larger size in swimming animals creates increased profile drag (O’Keefe and Carrano. In addition. Stein. Thorington and Heaney. humeral epicondylar index. Colomys goslingi. palmaris longus. Elbow extension. nificantly different from terrestrial forms. The unusual proportions of Colomys may reflect the distinctive wading behavior it uses when hunting (Kingdon. arboreal rodents studied here consistently differed from the other groups of rodents studied. particularly the medial epicondyle which serves as the origin of the manual flexors (flexor carpi radialis. and tibial robustness index values not sig- . Digging is also enhanced by enlarged humeral epicondyles. Journal of Morphology Arboreal Tree squirrels. ulnar. 2002. shortening of the forelimb (reducing out-lever) and enlarged muscular attachments (increasing both in-lever and the area of insertion) both result in improved mechanical advantage for the primary digging muscles (Hildebrand. and the origin of the flexor carpi ulnaris (Lehmann. the tiny European water vole. ($160 g) has limb proportions (CI. Nevertheless. Kerbis Peterhans and Patterson. The trend towards a shorter femur in larger species minimizes induced drag. 4d). 1916). and olecranon length index. 1953. but not all. along with retraction of the arm. joint mobility is largely related to the shape of bone articular surfaces and the structure of limb girdles (Cartmill. anconeus. tibial spine index) and a larger paddle (pes length index) increase propulsion during the power stroke. The deltopectoral crest acts as the insertion for several groups of muscles important for digging. enlarged terminal phalanges with fast-growing claws on the manus are used in breakdown of the soil (Hildebrand. 2000). the FEB (femoral epicondylar index) of Colomys is enlarged like other semiaquatic taxa. larger species require greater specialization. ($60 g) is similar to other swimming taxa in its CI. However. Table 5). 1985). 1995). Grasping is important for climbing (Wood Jones. Thus. Our results are consistent with previous studies which found adaptations that facilitate climbing in rodents include overall joint mobility as well as elongate and gracile limbs (both proximally and distally) (Thorington. flexors digitorum profundis.0). They display relatively elongate humeri (BI. Fig. in some species. the semifossorial rodents in this study displayed relatively elongate claws on the manus (claw length index >1. typically scratch-diggers. Table 5). Fig. Fig. as both fore and hind limbs are used in climbing. whereas larger hind limb muscles (femoral epicondylar index. 4c). and the digits of arboreal rodents are relatively elongate (manus proportions index. Nevertheless. Consistent with previous observations. and olecranon process of the ulna (shoulder moment index. particularly in features associated with grasping. and triceps brachii muscles. 2005). Scratch-digging behavior is typified by production of large forces by the forelimbs.b). and equal claw lengths (claw length index) on the manus and pes. thus. Semifossorial Nearly all rodents do some digging and most rodent families include species with fossorial habits. Sargis. The African water rat. is the primary action used to break up and remove soil when most mammals dig. 2001. 1988. The extent to which the skeleton and musculature are modified relates to the fraction of time spent in water and body size (Dunstone. 1963). The mechanical advantage of the gluteal muscles (gluteal index) of semifossorial rodents is also significantly greater than that of their terrestrial relatives. Korth. shortened antebrachii (BI. Fig. relatively short antebrachii (BI). 1993). and olecranon length index). 2000). Relative olecranon lengths for the blind mole-rats Spalax and Nannospalax are Journal of Morphology extremely high. Distal shortening of the manus (manus proportions index. and tibial spine index scores. The two latter modes of digging are primarily seen in highly fossorial. It is noteworthy that in contrast to other fossorial mammals. the length of the deltopectoral crest in fossorial species is more than half the length of the humerus. A similar pattern of more pronounced fossorial specializations in larger squirrels was observed in Lagaria and Youlatos’ (2006) study. enlarged muscle attachments. dorsoepitrochlearis. The small ground squirrels Ammospermophilus ($120 g) and Tamias ($75 g) are less specialized than their larger relatives. with the process making up more than 1/3 of the total length of the ulna. Nevo. and olecranon process of the ulna (shoulder moment index.X. other than the claws and pisiform (the insertion of the manual flexors) the manual bones of subterranean rodents are extremely reduced (Stein. and the forelimbs and hind limbs are more similar in length (IM). Like semifossorial rodents. Hildebrand. respectively. Additionally. Relative to semifossorial rodents. including the humeral retractors. and head-lift digging. including triceps brachii. and olecranon indices than their nonburrowing relatives. however. Fossorial Fossorial and subterranean rodent species are known from five extant families (21 genera) and occur on every continent except Australia and Antarctica (Stein. chisel-tooth. ulnar robustness index. and observed values are particularly high in subterranean species belonging to the Bathyergidae (mole-rats). femoral robustness index. robust limbs and feet. epicondyles of the humerus. a powerful flexor of the manus and the largest muscle in the forelimb of gophers (Lehmann. and anconeus. Moreover.1402 J.b). The primarily chiseltooth digging bathyergids Cryptomys. 4c. the flexor carpi ulnaris.f). VAN VALKENBURGH likely reflecting the importance of these muscles in resisting the tendency of the body to be pushed backwards when digging. Fossorial rodents also show relatively more robust bones (humeral robustness index. fossorial rodents exhibit many of the same adaptations seen in semifossorial species but to a greater degree (Lehmann. Since bodies of fossorial rodents tend to be pushed backwards as soil resists digging. 1963. like semifossorial rodents. 5a. tibial spine index) to aid in resisting the tendency of the body to be pushed backwards while digging. gastrocnemius. 2000). 1995. On an average. and Spalacidae (blind mole-rats and zokors). Body size may have a significant impact on the degree of specialization in semifossorial rodents. the presence of other fossorial adaptations in the postcranial skeleton of these rodents (high shoulder moment index and olecranon length index) indicates the conserved role of the forelimbs and overall limb proportions in removing soil when digging. Fig. their habit of burrowing primarily for shelter and refuge means their specializations need not be as extreme as larger or more extensive burrowers. Chisel-tooth digging bathyergids and spalacids also show enlarged hind limb muscle attachments (femoral epicondylar index. . elbow extensors. 1993. 1993). fossorial species also display high gluteal index. related to enlarged gluteus medius. A recent study of squirrels by Lagaria and Youlatos (2006) yielded similar results to our own. Stein. reflecting the fact that teeth rather than claws are used to break up soil. fossorial rodents display three distinct digging modes: scratch. Biknevicius. including: the deltopectoral crest of the humerus.5). Finally. SAMUELS AND B. 1916. femoral epicondylar index. These head-lift diggers also possess shoulder moment index and ulnar robustness index values greater than any other rodents in the analysis. Geomyidae (gophers). which are evident in their skeletal morphology. Not surprisingly. and Heterocephalus all show comparatively low humeral epicondylar index and claw length index scores compared to other fossorial rodents (Fig. and manual and digital flexors (Lagaria and Youlatos. but as mentioned previously the relative size of the olecranon processes in the blind mole rats Spalax and Nannospalax exceeds that of any other rodents. forearm pronators and flexors. humeral epicondylar index. However. fossorial rodents in this study display elongate claws on the manus (average claw length index >1. 1999). 4d) reduces the out-lever and improves the mechanical advantage of muscles employed during digging. Stein. subterranean rodents with shortened. 1916) along with a second head of the flexor digitorum profundis in some fossorial rodents (Gambaryan and Gasc. and hamstrings. 2000). Table 5) that accommodate the compressive and torsional stresses placed on the limbs when digging (Holliger. regardless of digging mode. Head-lift diggers show many features seen in chisel-tooth diggers. Heliophobius. Skeletal modifications in semifossorial squirrels corresponded with extensive muscular enlargement. with burrowing species showing significantly larger shoulder moment. the femur and tibia of fossorial species are reduced (Fig. and modifications of the skull and jaws (Nevo. 1963) originates from the olecranon as well (Holliger. The enlarged olecranon process increases the moment arm of elbow extending muscles that insert there. all of which act to resist the tendency to move rearward when digging. 2006). epicondylar. 1985. enlargement of these muscles aids in maintaining a stable position. and reduce load on the patagium. Howell. but their adaptations are not as extreme. Elongation of the tibia and pes paired with proximal insertion of muscles and reduction in digit number (seen in Dipodidae) all act to increase the speed of hind limb rotation and jump length. whereas a smaller olecranon would allow full extension of the elbow. When combined. Casinos. 4h). 1995). manual digits in gliding rodents are relatively elongate (manus proportions index. these result in hind limbs being more than twice the length of the forelimbs on average (IM < 0. Gambaryan. similar to the arboreal group. reduce induced drag. 1995.. ´ 1987. including two families of rodents (Anomaluridae and Sciuridae). largely on the basis of qualitative assessment of morphologic characteristics. 1994. Fig. femoral. 5b) and hind foot (pes length index. 4d) to improve grasping. suggesting larger gliders should have significantly greater loading on their patagium (since area and mass show a 2/3 scaling factor). As climbing is fundamentally linked to gliding behavior in rodents.e). humeral epicondylar index. Fig. including both quadrupedal hoppers and complete bipeds. Gliding squirrels possess elongate antebrachii and show an increase in the ratio of forelimb to hind limb length when compared to similar sized tree squirrels (Thorington and Heaney. 2003). More proximal insertion of the pectoralis and deltoid muscles in gliders would reduce power and increase mobility of the shoulder joint. members of the Family Castoridae vary in limb morphology and inferences concerning extinct castorid locomotion have been postulated for some of the nearly 50 species represented in the fossil record. humeral epicondyles. 1985). When compared with most nongliding rodents. CI. Korth. Runestad and Ruff. ulnar. Skeletal features of gliding rodents do not display significant allometric changes. olecranon length index. like the quadrupedal jumping mice Zapus and Napaeozapus. with the consequence of reduced power and improved ranges of motion for these muscles. Fig. Ricochetal rodents included in this analysis are characterized by having hind limbs much longer than their forelimbs (IM) due to both elongation of the tibia (CI. Hugueney and Escuillie. tibial spine index). Gliding Gliding is seen in four extant families of mammals. Gliding rodents in this study display relatively elongate and gracile bones (low humeral. femoral epicondylar index. The enlarged greater trochanter of the femur (seen in high gluteal index scores. especially proximally (humeri and femora) when compared with nongliders (Norberg. These features increase the aspect ratio. Previous research revealed saltatory and ricochetal animals tend to show longer. 1981. 1994. but detailed quantitative comparisons of locomotor characteristics within and between subfamilies are lacking. which powers hind limb retraction vital for jumping behavior. they found relatively smaller deltopectoral crests. Korth. These findings are similar to a recent study of flying squirrels by Thorington et al. more gracile hind limbs. Gliding rodents also display relatively equally proportioned limbs and equal claw lengths on the manus and pes (claw length index). 1985. The most strongly adapted saltatory rodents include kangaroo rats. 1933. and reorientation of these muscles to improve velocity of the limbs during the propulsive stroke (Hatt. and tibial robustness index scores. Emerson. despite their independent evolution. Korth and Rybczynski.5). 4a. Saltatory rodents. These animals possess skin folds (patagia) extending from the body to the limbs that act as airfoils to provide the lift necessary for gliding. are similar to ricochetal species in the structure and proportions of the limbs. Fig. despite having relatively elongate femora) increases the mechanical advantage for the gluteus medius. whereby the hind limbs are used simultaneously to produce a jump. and springhares that display ricochetal behavior. Application to Extinct Taxa Past researchers have inferred dietary and locomotor habits of some extinct rodent species. Both flying squirrels (Family Sciuridae) and scaly tailed flying squirrels (Family Anomaluridae) show nearly identical postcranial proportions. the gliders studied also show relatively elongate distal limb segments (high BI. Table 5). which decreases the in-lever of hind limb retracting muscles and hence increases the speed of rotation about the knee. Journal of Morphology . Alexander et al. For example. Low tibial spine index scores in ricochetal rodents are related to a more proximal insertion of the semimembranosus and semitendinosus muscles. 1932. and depositional environments. jerboas. Previous work indicates that gliding mammals have an elongate appendicular skeleton. gluteal index. Hypothesized locomotor habits from previous research on the Castoridae divide the group into two specialized classes: fossorial/ subterranean adapted beavers (Palaeocastorinae and Migmacastorinae) and semiaquatic adapted beavers (Castorinae and Castoroidinae) (Martin. and olecranon processes in gliding squirrels. (2005). phylogenetic affinities. features that increase the size of and decrease loading on the patagium. larger hind limb muscles. 1974. 1981). Elongation of these bones without enlargement of many muscle attachments results in low scores for many of the muscle moment arms (shoulder moment index. 1996. 2002.LOCOMOTOR ADAPTATIONS IN RODENTS 1403 Ricochetal Many rodents show saltatory behavior. Procastoroides. Individual specimens for each species were collapsed to a single point. but at times in the Tertiary Castor co-occurred with members of the giant beaver lineage including: Dipoides. the IM scores are more similar to semifossorial rodents. Correlation coefficient r 5 0. 1994). which classified them as semifossorial.028 x. Pseudopalaeocastor barbouri. The three early Miocene beavers from the Palaeocastorinae included in the analysis show adaptations suggestive of fossoriality. 4a. Palaeocastor nebrascensis and P. 2002). Only one beaver genus.137. 2003. The two species of Palaeocastor have scores for their fossorial ability and claw length indices similar to highly fossorial gophers and mole-rats. but has significantly narrower cut marks suggesting different cutting capabilities between species (Tedford and Harington.164. thus understanding their evolution and inferring their behaviors would aid in interpretation of their paleoecological roles. .745 1 12. Rybczynski. however. If these giant beavers show both tree-cutting and semiaquatic behaviors. then competition and consequent niche partitioning may have occurred. Castor. Kurten and Anderson. Shotwell. 1969. discriminant analysis allows comparisons of overall similarity in locomotor morphology seen in extant and extinct rodents.814.e. Castor. 1986. and Castoroides in North America and Trogontherium in Eurasia. Wright and Jones. 1970. 6. and olecranon processes. Journal of Morphology The combination of bivariate plots and DFA used here allows inference and interpretation of the extinct rodent ecologies.643 1 7. Correlation coefficient r 5 0.358 x. and pes length index scores very different from living beavers (Fig. Muller-Schwarze and ¨ Sun. 1929. Numbers associated with each point identify individual species (Table A1).. fossor were complete enough for inclusion in the discriminant analysis. they have BI. Although some authors propose members of the giant beaver lineage (Castoroidinae) show adaptations to semiaquatic locomotion. Correlation coefficient r 5 0. survives at present.001. a: Femur Epicondylar Index.001. VAN VALKENBURGH Fig. and Palaeocastor fossor all show large deltopectoral crests. Semiaquatic fit line (Dashed): y 5 10. Total fit line (Solid): y 5 14. 2003).h). Limb proportions in the palaeocastorine beavers are similar to those of semifossorial and fossorial rodents.X. P < 0. Castoroidines increased in size over time to become some of the largest known rodents (Schreuder. humeral epicondyles. 2007). CI. A semifossorial way of life is consistent with artifactual evidence of digging and fossilized burrow systems associated with these beavers. Korth. which are similar to extant prairie dog towns (Martin and Bennett.821 x.398 1 15. There is evidence of tree-cutting behavior in one genus (Dipoides). b: Tibial Spine Index. Presumably the influence of beavers on ecosystems and community structure would have been similar in the past. Living beavers are considered keystone species for forest and waterway ecosystems throughout their range (Naiman et al. Palaeocastor nebrascensis. the cut wood is similar to that of the modern beaver.1404 J. SAMUELS AND B. 2002. P < 0. Korth. 1977). Symbols represent locomotor types. Semiaquatic fit line (Dashed): y 5 18.704 x. others suggest that they possess a relatively unspecialized skeleton (Zakrzewski. When more complete specimens are available. Bivariate plots allow the examination of morphological similarities between living rodents and potentially incomplete fossil specimens. Total fit line (Solid): y 5 28. Plots of selected functional indices versus the log geometric mean (a proxy for body size).289 1 25.670. Correlation coefficient r 5 0. 1980. 1935. Corresponding with the increase in size of the lineage through time there is an increase in aquatic specialization. 4f). but the higher femoral epicondylar index scores in semiaquatic species are primarily due to a strong negative allometry in femur length (a trend that is not seen in other rodent groups). broad femoral epicondyles (Fig. 2007) suggest that these beavers likely competed with Castor for food. potentially allowing for niche partitioning. 2007). The enlarged epicondyles of the castoroidines suggest that. as well as the independently large European giant beaver Trogontherium would result in very high profile drag when swimming. Paenemarmota shows relatively large deltopectoral crests. and Castoroides were complete enough to be included in the discriminant analysis. 4e and 5a). Undulation of the tail and simultaneous paddling of the hind feet when submerged result in a significantly lower cost of transport for living beavers than for other semiaquatic mammals (Allers and Culik. like Castor. 1937). Fish. Although the hind limbs are similar. Like the extant Castor.LOCOMOTOR ADAPTATIONS IN RODENTS 1405 The discriminant analysis places the Pliocene Castor californicus within the semiaquatic group. Repenning (1962) suggested that the co-occurrence of Paenemarmota and the hyaenid Chasmaporthetes in Pliocene faunas may indicate the giant marmots were their preferred prey. Journal of Morphology . Procastoroides. and large manual terminal phalanges. Competition between the two lineages may have led to the progressive increase in body size seen in the Castoroidinae after the arrival of Castor in North America around the Hemphillian. and the previously mentioned hyaenids. Paenemarmota may have thus filled a similar ecological role to living marmots and ground squirrels. including saber-toothed cats. The broad. see Fig. The massive size (likely 50–100 kg) of the two North American giant beavers Procastoroides and Castoroides. 6a. coyotes. and birds of prey (Nowak. but in semiaquatic rodents the scores for these indices show a dramatic increase with increasing body size (Fig. The presence of semiaquatic adaptations in the Castoroidinae paired with the tree-cutting behavior seen in Dipoides (Tedford and Harrington. Dipoides. The early members of this lineage in North America. 1997. Living marmots and ground squirrels are commonly preyed upon by badgers. show distinctive semiaquatic adaptations and later members of the lineage show markedly shortened femora (Figs. as are extant marmots and ground squirrels. and elongate hind feet (Fig. they may have used their forelimbs to handle wood and vegetation. Castor co-occurs repeatedly with other beaver species from the subfamily Castoroidinae in the fossil record of North America and Eurasia. Members of the Castoroidinae lack this specialized tail. olecranon processes. The molars of both lineages are lophodont and show high hypsodonty indices. with Castor californicus slightly larger than Castor canadensis but both species having the same limb proportions (Zakrzewski. Rybczynski. 2007). This increased specialization can be seen in the castoroidine discriminant function scores. Stirton. wolves. this is reassuring as the early North American Castor is essentially indistinguishable in postcranial morphology from the living species. raising the question of how these beavers avoided competition. Differences in cutting performance and incisor structure suggest the types of trees favored by Castor and castoroidine beavers may have been quite different (Rybczynski. members of the Castoroidinae display particularly large humeral epicondyles (Fig. The bivariate plots confirm the overall similarity of these two species. where Procastoroides and Castoroides have higher discriminant function 1 and discriminant function 3 scores than Castor (the most aquatic living rodent). 6) may be of consequence to its ecology. borophagine dogs. flattened tail characteristic of Castor allows the undulatory mode of swimming that beavers use when submerged. with fully hypselodont teeth seen in all of the castoroidine beavers examined here (Stirton. The large size of Paenemarmota would require significantly larger burrow diameters than are seen for any living rodent. All of the castoroidine beavers studied show features characteristic of semiaquatic habits. 2000). For the total rodent sample both femoral epicondylar index and tibial spine index show very low correlations with body size. If Paenemarmota were social. 1969). 4h). a fact that would make them vulnerable to predation by larger carnivores. Rybczynski. 2003. consistent with the inference of tree-cutting and lodge or dam building behavior in these beavers (Tedford and Harrington. 2003. it would potentially represent large and relatively easy to subdue prey for many of the large carnivores in the Pliocene. There is significant positive allometry in FEB (Table 4). which is known only from the Pliocene. The medial and lateral epicondyles of the humerus are the origin of the carpal flexors. 4b). however its large size (similar to that of a living beaver. which classified them as semiaquatic. humeral epicondyles. Paenemarmota barbouri. 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Extant rodent species used in analysis of locomotor characteristics ID. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 Species Allactaga hotsoni Ammospermophilus leucurus Anomalurus pelii Aplodontia rufa Arvicola terrestris italicus Cannomys badius Castor canadensis Chelemys macronyx Clethrionomys (Myodes) californicus Coendou prehensalis Colomys goslingi Cryptomys hottentotes Cynomys gunnisoni Dinomys branickii Dipodomys deserti Dipodomys merriami Dipus (Jaculus) aegypticus Erethizon dorsatum Geomys bursarius Georychus capensis Geoxus valdivianus Glaucomys sabrinus Heliophobius argenteocinereus Heterocephalus glaber Hydromys chrysogaster Hylopetes nigripes Hyomys goliath Hystrix cristata Jaculus orientalis Marmota flaviventris Microtus californicus Myocastor coypus Nannospalax (Spalax) leucodon Napaeozapus insignis Nectomys squamipes Neofiber alleni Neotoma cinerea Nyctomys sumichrasti Ondatra zibethicus Onychomys leucogaster Orthogeomys grandis Oxymycterus dasytrichus Pappogeomys (Cratogeomys) tylorhinus Paraxerus cepapi Pedetes capensis Perognathus parvus Common name Hotson’s jerboa White-tailed antelope squirrel Pel’s scaly-tailed squirrel Mountain beaver European water vole Lesser bamboo rat American beaver Andean long-clawed mouse Western red-backed vole Brazilian porcupine African water rat African mole-rat Gunnison’s prairie dog Pacarana Desert kangaroo rat Merriam’s kangaroo rat Northern three-toed jerboa American porcupine Plains pocket gopher Cape mole-rat Long-clawed mole mouse Northern flying squirrel Silvery mole-rat Naked mole-rat Golden-bellied water rat Palawan flying squirrel Eastern white-eared giant rat Crested porcupine Greater Egyptian jerboa Yellow-bellied marmot Meadow Vole Nutria Lesser mole rat Woodland-jumping mouse South American water rat Round-tailed muskrat Bushy-tailed woodrat Vesper rat Muskrat Northern grasshopper mouse Giant pocket gopher Burrowing mouse Naked-nosed pocket gopher Smith’s bush squirrel Springhare Great Basin pocket mouse Family Dipodidae Sciuridae Anomaluridae Aplodontidae Cricetidae Spalacidae Castoridae Cricetidae Cricetidae Erethizontidae Muridae Bathyergidae Sciuridae Dinomyidae Heteromyidae Heteromyidae Dipodidae Erethizontidae Geomyidae Bathyergidae Cricetidae Sciuridae Bathyergidae Bathyergidae Muridae Sciuridae Muridae Hystricidae Dipodidae Sciuridae Cricetidae Echimyidae Spalacidae Dipodidae Cricetidae Cricetidae Cricetidae Cricetidae Cricetidae Cricetidae Geomyidae Cricetidae Geomyidae Sciuridae Pedetidae Heteromyidae n 4 6 1 8 3 1 10 5 5 4 5 3 6 2 4 5 2 6 6 1 7 7 2 4 2 6 2 5 4 5 5 6 4 2 3 4 7 2 5 5 5 3 4 5 5 5 Locomotion type Ricochetal Semifossorial Gliding Fossorial Semiaquatic Fossorial Semiaquatic Semifossorial Terrestrial Arboreal Semiaquatic Fossorial Semifossorial Terrestrial Ricochetal Ricochetal Ricochetal Arboreal Fossorial Fossorial Fossorial Gliding Fossorial Fossorial Semiaquatic Gliding Terrestrial Semifossorial Ricochetal Semifossorial Terrestrial Semiaquatic Fossorial Terrestrial Semiaquatic Semiaquatic Terrestrial Arboreal Semiaquatic Terrestrial Fossorial Semifossorial Fossorial Arboreal Ricochetal Terrestrial Journal of Morphology . and in application to other mammalian orders ID no. 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 Species Ailurus fulgens Choleopus didactylus Cynocephalus volans Dasypus novemcinctus Gulo gulo Hydrochaeris hydrochaeris Lontra canadensis Macropus robustus Mephitis mephitis Mustela frenata Neovison vison Phoca vitulina Procyon lotor Scapanus townsendi Sorex vagrans Taxidea taxus Common name Red panda Southern two-toed sloth Philippine colugo Nine-banded armadillo Wolverine Capybara Northern river otter Hill wallaroo Striped skunk Long-tailed weasel American mink Harbor seal Raccoon Townsend’s mole Vagrant shrew American badger Family Ailuridae Megalonychidae Cynocephalidae Dasypodidae Mustelidae Caviidae Mustelidae Macropodidae Mephitidae Mustelidae Mustelidae Phocidae Procyonidae Talpidae Soricidae Mustelidae n 1 1 1 1 1 10 1 1 1 1 1 1 1 1 1 1 Locomotion type Arboreal Arboreal Gliding Fossorial Terrestrial (Scansorial) Cursorial/Semiaquatic Semiaquatic Ricochetal Semifossorial Terrestrial Terrestiral/Semiaquatic Aquatic Terrestrial/Scansorial Fossorial Terrestrial Semifossorial TABLE A3. Extant species used in analyses of unknown locomotor types. 1929) Extinct species are indicated by y. 84 85 86 87 88 89 90 91 92 93 94 Species Castor californicus Castoroides ohioensisy Dipoides stirtoniy Paenemarmota barbouriy Palaeocastor fossory Palaeocastor nebrascensisy Procastoroides idahoensisy Pseudopalaeocastor barbouriy Monosaulax pansusy Eucastor tortusy Trogontherium cuvieriy y Family/subfamily Castoridae/Castorinae Castoridae/Castoroidinae Castoridae/Castoroidinae Sciuridae/Marmotinae Castoridae/Palaeocastorinae Castoridae/Palaeocastorinae Castoridae/Castoroidinae Castoridae/Palaeocastorinae Castoridae/Castoroidinae Castoridae/Castoroidinae Castoridae/Castoroidinae Age of specimens used Pliocene Pleistocene Miocene Pliocene Miocene Miocene Pliocene-Pleistocene Miocene Miocene Miocene Pleistocene (Schreuder. 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 Species Peromyscus maniculatus Petaurista petaurista Phloeomys pallidus Pygeretmus pumilio Rattus norvegicus Rattus rattus Ratufa affinis Rhizomys pruinosus Sciurus niger Sigmodon hispidus Spalax giganteus Spermophilus beecheyi Sphiggurus mexicanus Tachyoryctes splendens Tamias palmeri Tamiasciurus hudsonicus Thomomys bottae Tylomys nudicaudus Xerus inauris Zapus princeps Zygogeomys trichopus Common name Deer mouse Red giant flying quirrel Northern Luzon giant cloud rat Dwarf fat-tailed jerboa Norway rat Black rat Pale giant squirrel Hoary bamboo rat Fox squirrel Hispid rice rat Giant mole rat California ground squirrel Mexican hairy dwarf porcupine East African mole rat Palmer’s chipmunk Red squirrel Botta’s pocket gopher Peter’s climbing rat South African ground squirrel Western jumping mouse Michoacan pocket gopher Family Cricetidae Sciuridae Muridae Dipodidae Muridae Muridae Sciuridae Spalacidae Sciuridae Cricetidae Spalacidae Sciuridae Erethizontidae Spalacidae Sciuridae Sciuridae Geomyidae Cricetidae Sciuridae Dipodidae Geomyidae n 5 4 3 3 5 5 5 6 6 5 1 6 4 4 6 5 6 4 2 2 5 Locomotion type Terrestrial Gliding Terrestrial Ricochetal Terrestrial Terrestrial Arboreal Fossorial Arboreal Terrestrial Fossorial Semifossorial Arboreal Fossorial Semifossorial Arboreal Fossorial Arboreal Semifossorial Terrestrial Fossorial 1409 TABLE A2. no. (Continued). ID. Extinct rodent species used in the analyses ID no.LOCOMOTOR ADAPTATIONS IN RODENTS TABLE A1. Journal of Morphology . 166 0.691 0.055 0.090 0.087 0.143 0.526 0.311 0.521 1.267 0.094 0.131 0.223 0.200 0. VAN VALKENBURGH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 Allactaga hotsoni Ammospermophilus leucurus Anomalurus pelii Aplodontia rufa Arvicola terrestris italicus Cannomys badius Castor canadensis Chelemys macronyx Clethrionomys (Myodes) californicus Coendou prehensalis Colomys goslingi Cryptomys hottentotes Cynomys gunnisoni Dinomys branickii Dipodomys deserti Dipodomys merriami Dipus (Jaculus) aegypticus Erethizon dorsatum Geomys bursarius Georychus capensis Geoxus valdivianus Glaucomys sabrinus Heliophobius argenteocinereus Heterocephalus glaber Hydromys chrysogaster Hylopetes nigripes Hyomys goliath Hystrix cristata Jaculus orientalis Marmota flaviventris Microtus californicus Myocastor coypus Nannospalax (Spalax) leucodon Napaeozapus insignis Nectomys squamipes Neofiber alleni Neotoma cinerea Nyctomys sumichrasti Ondatra zibethicus Onychomys leucogaster Orthogeomys grandis Oxymycterus dasytrichus Pappogeomys (Cratogeomys) tylorhinus Paraxerus cepapi Pedetes capensis Perognathus parvus .639 0.103 0.224 0.115 0.391 1.113 0.476 0.123 0.386 0.646 0.679 1.327 0.401 0.367 0.073 0.495 0.331 0.499 0.494 0.056 0.118 0.637 0.045 0.129 0.492 0.104 0.404 0.063 0.356 0.093 0.273 0.607 0.328 1.103 0.051 0.376 0.829 0.727 0.142 0.052 0.108 0.650 0.349 0.104 0.088 0.097 0.096 0.043 0.060 0.317 1.438 0.076 0.952 1.807 1.057 0.103 0.626 0.102 0.434 0.109 0.113 0.079 0.279 0.048 0.803 0.075 0.445 0.522 0.908 0.254 0.769 0.363 0.220 0.768 1.318 0.266 0.380 0.079 1.971 1.039 1.179 0.072 0.336 0.790 0.079 1.231 0.591 0.269 0.036 0.107 0.326 0.087 0.236 1.304 1.562 0.105 0.910 0.091 0.316 0.451 0.145 0.813 0.311 0.246 0.914 0.037 0.244 0.520 0.087 0.532 0.081 0.704 0.163 1.127 0.093 0.122 0.240 0.226 0.711 0.215 0.217 0.082 0.260 0.172 0.943 1.109 0.246 0.779 0.112 0.363 1.304 0.609 0.419 0.429 0.362 0.517 0.082 0.398 0.177 0.949 0.308 0.343 0.142 0.126 0.034 1.042 0.295 1.567 0.786 0.073 0.455 0.850 0.346 0.204 0.056 0.043 0.400 0.349 0. 0.547 0.747 0.057 0.757 0.323 0.873 0.071 0.490 0.148 0.319 0.124 0.074 0.079 0.167 0.928 1.380 0.421 0.838 1.338 0.046 0.934 0.471 0.061 0.140 0.145 0.989 0.449 0.759 0.904 0.188 0.915 0.201 0.120 0.527 0.489 1.752 0.064 0.569 0.121 0.446 0.141 0.456 0.112 0.925 0.062 1.080 0.063 0.131 0.201 0.052 0.202 0.437 0.870 0.155 0.885 0.127 0.353 0.267 0.698 0.314 0.123 0.556 0.058 0.568 0.056 0.202 0.233 0.246 0.466 0.246 0.479 0.100 0.373 0.321 0.130 0.000 10.803 1.041 0.078 0.536 0.223 0.115 0.082 0.857 1.098 0.067 0.157 0.056 0.040 0.456 0.228 0.688 0.060 0.087 0.881 1.294 0.567 0.086 0.174 0.222 0.562 0.172 0.908 0.255 0.930 0.624 0.580 0.089 0.633 0.076 0.060 0.652 0.118 0.646 0.052 0.327 0.901 0.869 0.658 0.440 0.962 1.139 0.251 0.041 0.081 0.725 0.159 0.134 0.905 0.098 0.655 0.251 1.267 0.949 0.028 1.118 0.513 0.465 0.382 0.016 0.064 0.581 0.166 0.292 0.946 0.410 0.387 0.093 0.655 0.066 1.066 0.494 0.112 0.618 0.829 0.226 1.466 0.101 0.072 0.086 0.295 0.082 0.X.087 0.102 0.735 0.333 0.230 0.108 0.510 0.092 0.316 0.787 0.498 0.055 0.040 1.390 0.234 0.326 0.351 0.093 0.279 0.527 0.827 0.548 0.101 0.265 0.036 0.155 1.955 1.155 0.420 1.538 0.386 0.052 0.094 0.060 0.102 1.410 0.100 0.163 0.095 0.275 0.082 0.905 0.129 1.368 0.114 0.049 0.393 0.982 1.379 0.507 0.128 0.094 0.116 0.276 0.195 0.283 0.943 2.590 0.486 0.068 0.137 0.079 0.280 0.471 0.812 0.461 0.551 0.TABLE A4.655 0.095 0.140 0.843 0.317 0.229 0.626 0.828 0.992 1.249 1.118 0.253 0.683 1.263 0.074 0.510 0.845 0.526 0.308 0.330 0.423 0.252 0.551 0.704 Species SMI BI HRI HEB OLI URI MANUS CLAW CI GI FRI FEB TRI TSI PES IM Journal of Morphology J.163 0.237 0.056 0.458 0.475 0.644 0.068 0.212 0.999 1.329 0.147 1.349 0.037 0.310 0.042 0.746 0.849 0.047 0.044 0.120 0.091 0.010 1.294 0.337 1.028 0.995 0.043 0.846 0.216 0.975 1.110 0.242 0.136 0.785 0.572 0.250 0.913 0.308 0.062 1.101 0.175 0.263 0.093 0.075 0.217 0.053 0.296 1.825 0.974 1.425 0.470 0.723 0.103 0.228 0.102 0.940 1.012 0.254 0.354 0.098 0.074 0.089 0.561 1.081 0.260 0.121 0.857 1.650 0.864 0.025 0.261 0.108 0.076 0.880 0.049 0.129 0.074 0.074 0.051 0.457 0.458 0.104 0.175 1.191 0.078 0.930 0.456 0.204 0.090 0.053 0.326 0.094 0.050 0.450 0.089 0.112 0.500 0.249 0.091 0.267 0.209 0.277 0.079 0.426 0.197 0.142 0.400 0.617 1.688 0.433 0.091 0.042 0.101 0.015 2.098 0.080 0.503 0.078 0.420 0.966 0.066 0.343 1.284 0.189 0.509 0.213 0.778 0.215 0.290 0.513 0.274 0.946 1.303 0.098 0.206 0.088 0.677 0.230 0.425 0.059 0.090 0.052 0.572 0.314 0.139 0.022 0.105 0.020 1.099 0.267 0.011 1.230 0.070 0.057 0.057 0.182 0.367 0.047 0.397 0.107 0.048 0.306 0.091 0.092 0.495 1.159 0.449 0.662 1.880 0.870 0.069 0.512 0.421 0.913 1.029 1.739 1.131 0.089 0.079 0.467 0.361 0.054 0.314 0.490 0.068 0.429 0.601 0.077 0.032 0.790 0.227 0.134 0.109 0.421 0.925 0.527 0.613 0.489 0.383 0.325 0.131 0.121 1.048 0.127 1.086 0.585 0.922 0.392 0.294 0.622 0.656 1.296 0.412 0.075 0.113 0.055 0.628 0.514 0.057 0.504 0.270 0.056 0.764 0.373 0.507 1.422 0.159 0.810 0.077 0.091 0.129 0.367 0.084 0.216 0.692 0.079 0.101 0.258 0.495 0.090 0.042 1.196 0.940 0.202 1.583 0.933 0.239 0.465 0.169 0.096 0.064 0.136 0.093 0.091 0.484 0.207 1.118 0.045 0.968 0.113 1.046 0.129 0.466 0. Species averages for functional indices used in the analyses 1410 ID no.156 0.749 0.440 0.142 0.610 0.058 0.076 0.078 0.044 0.072 0.173 1.033 1.588 0.526 0.031 0.078 0.459 0.760 0.416 0.321 0.980 1.816 0.099 1.343 0.137 0.219 1.849 0.577 0. SAMUELS AND B.175 2.416 0.635 0.285 0.116 0.384 0.112 0.341 0.058 0.124 0.358 0.334 0.074 0.884 0.774 1.032 0.604 0.238 0.112 0.064 0. 452 0.542 0.582 0.TABLE A4.563 0.901 0.084 0.803 1.130 0.336 0.072 0.736 0.264 0.040 0.113 0.570 0.770 0.499 0.092 0.092 0.063 0.629 0.942 0.085 0.248 0.137 1.262 0.046 0.092 0.347 0.124 0.022 1.333 0.577 0.039 0.081 0.064 0.088 1.739 0.489 0.505 1.587 0.354 BI HRI HEB OLI URI MANUS CLAW CI GI FRI FEB TRI TSI PES IM 0.804 0.654 0.075 0. (Continued).163 1.499 0.462 0.941 0.097 0.001 1.114 0.058 0.319 0.444 0.308 0.265 0.940 1.248 0.063 0.159 0.087 0.265 0.087 0.240 0.488 0.136 0.401 0.193 0.396 0.948 0.248 0.290 0.247 0.054 0.239 0.862 0.310 0.058 0.108 0.900 0.077 0.823 0.141 0.511 0.095 0.753 1.830 0.269 0.819 0.035 1.077 0.933 1.071 0.067 0.155 0.881 0.049 0.084 0.304 0.160 0.001 0.058 0.513 0.309 0.483 0.793 0.324 0.165 0.274 0.081 0.250 0.630 0.626 0.102 0.123 0.435 0.060 0.533 0.558 0.142 0.228 0.077 0.023 0.319 0.358 0.051 0.657 0.125 0.207 0.851 0.339 0.720 0.958 0.500 0.967 0.901 1.109 0.992 0.237 0.181 0.240 0.186 0.116 1.185 0.219 0.899 1.331 0.431 0.131 0.369 0.379 0.267 0.338 0.865 0.078 0.711 1.123 0.401 0.146 0.039 0.154 0.736 0.105 0.076 0.943 0.234 0.262 0.111 0.054 0.467 0.684 0.771 0.496 0.174 0.180 0.037 0.951 1.773 0.339 0.246 0.390 0.313 0.337 0.342 0.017 1.250 0.973 0.107 0.278 2.057 0.756 0.712 0.572 0.093 0.670 0.014 0.094 0.952 0.324 0.402 1.021 1.148 0.466 0.422 0.401 0.101 0.157 0.136 0.629 1.589 0.269 0.121 0.062 0.006 0.326 1.161 0.041 0.997 1.095 0.563 0.684 2.409 0.069 0.072 0.183 0.097 0.304 0.172 0.108 0.705 0.056 0.050 0.052 0.066 0.105 0.148 0.871 0.078 0.365 0.397 0.142 0.568 0.085 0.440 0.823 0.138 0.284 0.066 0.079 0.750 1.912 0.630 0.414 0.455 0.147 0.254 0.126 0.086 0.089 0.307 0.088 0.043 0.981 0.108 0.745 0.708 0.399 0.979 0.554 0.762 0.737 0.647 0.071 0.178 1.195 0.790 0.192 0.952 1.731 0.071 0.217 0.432 0.484 0.234 0.274 0.554 0.101 0.780 0.702 0.239 0.600 0.093 0.160 0.049 0. Species 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 LOCOMOTOR ADAPTATIONS IN RODENTS 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 Peromyscus maniculatus Petaurista petaurista Phloeomys pallidus Pygeretmus pumilio Rattus norvegicus Rattus rattus Ratufa affinis Rhizomys pruinosus Sciurus niger Sigmodon hispidus Spalax giganteus Spermophilus beecheyi Sphiggurus mexicanus Tachyoryctes splendens Tamias palmeri Tamiasciurus hudsonicus Thomomys bottae Tylomys nudicaudus Xerus inauris Zapus princeps Zygogeomys trichopus Ailurus fulgens Choloepus didactylus Cynocephalus volans Dasypus novemcinctus Gulo gulo Hydrochaeris hydrochaeris Lontra canadensis Macropus robustus Mephitis mephitis Mustela frenata Neovison vison Phoca vitulina Procyon lotor Scapanus townsendi Sorex vagrans Taxidea taxus Castor californicusy Castoroides ohioensisy Dipoides stirtoniy Paenemarmota barbouriy Palaeocastor fossory Palaeocastor nebrascensisy Procastoroides idahoensisy Journal of Morphology 1411 Extinct species are indicated by y.294 0.089 0.590 0.161 1.500 0.082 0.042 0.102 2.313 0.081 0.261 0.102 0.059 0.535 0.824 0.212 0.118 0.182 0.189 0.355 0.176 0.233 0.048 0.125 0.497 0.442 0.478 0.500 0.058 0.818 1.598 0.008 1.085 0.049 0.185 0.096 0.080 0.399 0.279 0.677 0.253 0.357 0.734 0.485 0.302 0.072 0.197 1.974 0.120 0.799 0.092 0.052 0.200 0.260 0.286 0.552 1.774 1.335 0.255 0.051 0.739 0.050 0.206 0.235 0.177 0.420 0.358 0.253 0.076 0.429 0.309 0.409 0.276 0.070 0.139 0.372 0.605 0.095 0.351 1.166 0.310 0.078 0.309 0.753 0.464 0.521 0.108 0.079 0.677 0.906 0.537 0.447 0.070 1.915 0.295 0.076 0.474 0.119 0.245 0.859 0.474 1.536 0.038 0.962 0.454 0.123 1.998 0.135 0.046 0.166 1.378 0.994 0.037 0.362 0.314 0.100 0.113 0.102 0.539 0.063 0.298 0.168 0.760 0.077 0.054 0.823 0.127 1.160 0.826 0.089 0.304 1.755 0.251 0.097 0.101 0.507 0.039 0.069 0.438 0.502 0.081 0.081 0.895 0.635 0.672 0.120 0.772 0.312 0.562 0.083 0.433 0.291 0.081 0.074 0.428 0.257 0.131 1.189 0.842 1.587 1.086 0.235 0.203 0.048 0.644 0.542 0.371 0.582 0.768 0.451 0.339 0.569 0.452 0.708 2.992 0.947 0.013 1.083 0.826 0.096 0.497 0.995 0.691 0.090 0.556 0.956 1.569 0.713 0.346 0.736 0.348 0.103 0.585 1.247 0.325 0.106 0.169 0.157 0.270 0.101 0.067 0.041 0.883 0.353 0.112 0.085 0.226 0.584 0.108 0.531 1.195 1.175 0.080 0.030 1.342 0.393 0.302 0.383 0.344 0.380 0.081 0.303 0.066 0.297 0.888 0.151 0.059 0.842 0.093 0.566 0.122 0.365 0.408 0.422 0.095 0.506 0.073 0.207 0.838 0.011 0.106 0.452 0.136 0.170 1.807 1.125 0.032 0.490 0.186 0.794 0.376 0.283 0.167 0.233 0.359 0.398 0.079 0.913 1.077 0.675 0.102 0.190 1.289 0.377 0.658 0.552 0.475 0.010 0.601 0. SMI 0.288 0.262 0. .596 1.941 0.758 0.469 0.850 0.313 0.084 1.124 0.274 0.033 0.106 0.417 0.046 1.372 0.032 0.909 0.167 0.983 1.242 0.140 0.645 0.353 0.788 0.053 0.560 0.391 0.095 0.771 ID no.792 0.018 0.078 0.168 0.096 0.401 0.150 1.067 1.870 0.601 0.104 0.077 0.075 0.057 0.683 0.713 0.240 0.140 0.060 0.191 0.514 0.266 0.023 0.803 1.095 0.248 0.514 0.075 0.101 0.141 0.089 0.046 0.089 0.917 0.147 0.419 0.323 0.190 0.058 0.077 0.047 0.146 0.393 0.092 0.262 0.939 0.069 0.582 0.045 1.904 0.193 0.372 0.945 0.938 1.071 0.982 0.143 1.639 0.737 0.663 0.091 0.038 0.787 0.447 1.409 0.076 0.099 0.088 0.324 1.133 0.085 0.129 0.378 0.128 0.076 0.086 0.330 0.302 0.322 0.064 0.144 0.074 0.371 0.082 0.116 0.071 0.216 0.192 0.114 0.969 0.046 0.280 0.839 0.142 0.722 1.276 0.483 0.513 0.056 0.287 0.640 0.461 0.035 0.080 0.088 0.383 0.801 0.389 0.062 0.412 0.