ARTICLE IN PRESS Journal of Human Evolution

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6 Table 3 DFA classification results. ARTICLE IN PRESS A. Actual rows by predicted columns for subfamilial DFA classification results: counts and (%), DFA correctly classified 89.5% of original grouped cases. Cercopithecinae Colobinae Total Cercopithecinae 120 (89.6) 14 (10.4) 134 Colobinae 2 (11.1) 16 (88.9) 18 B. Actual rows by predicted columns for leave-one-out cross validation for subfamilial DFA classification results: counts and (%), DFA correctly classified ca. 89% of cross-validated grouped cases. Cercopithecinae Colobinae Total Cercopithecinae 119 (88.8) 15 (11.2) 134 Colobinae 2 (11.1) 16 (88.9) 18 C. Actual rows by predicted columns for cercopithecine genera DFA classification results: counts and (%), DFA correctly classified 84.1% of original grouped cases. Cercopithecus Macaca Mandrillus Papio Theropithecus Total Cercopithecus 21 (87.5) 3 (12.5) 0 0 0 24 Macaca 6 (12) 63 (84) 2 (2.7) 0 1 (1.3) 75 Mandrillus 0 1 (10) 7 (70) 2 (20) 0 10 Papio 0 0 0 16 (88.9) 2 (11.1) 18 Theropithecus 0 1 (20) 0 0 4 (80) 5 D. Actual rows by predicted columns for leave-one-out cross validation for cercopithecine genera DFA classification results: counts and (%), DFA correctly classified ca. 75% of original grouped cases. Cercopithecus Macaca Mandrillus Papio Theropithecus Total Cercopithecus 19 (79.2) 5 (20.8) 0 0 0 24 Macaca 11 (14.7) 59 (78.7) 2 (2.7) 0 3 (4.0) 75 Mandrillus 1 (20) 1 (10) 5(50) 2 (20) 0 10 Papio 0 0 1 (5.6) 14 (77.8) 3 (16.8) 18 Theropithecus 0 1 (20) 0 1 (20) 3 (60) 5 efficiency may be an additional contributing factor in long limb skeletal differences between the arboreal M. fascicularis and the terrestrial M. nemestrina (Rodman, 1979). While he did not consider the osteological morphology of the foot in his original study, it is intriguing to speculate if this hypothesis can be applied to the similarities observed here between Theropithecus and Macaca. Theropithecus forage over much shorter distances while feeding than the sympatric anubis baboons (Iwamoto, 1993), and perhaps provide an analogy to the M. fascicularis–M. nemestrina study by Rodman (1979). If this is correct, the misclassification between Theropithecus and Macaca fascicularis may be due to similarities in foraging efficiencies, which may confound the distinction in calcaneal morphology observed among arboreal and terrestrial cercopithecines. Posterior probabilities of classification to each taxon were obtained for each quartile. The results indicate that UB 330 should be assigned to the genus Theropithecus with a median probability of 98.5% (with an inter-quartile range of 98.1–99.2%). Results indicated that UB 330 can be assigned to Cercopithecus with a median probability of 1.1% (with an inter-quartile range of 0.06–1.67%), and could be assigned to Papio with a median probability of 0.22% (with an inter-quartile range of 0.01–0.35%). Probability of assignment to Macaca and Mandrillus was less than 0.001 percent. The high posterior probability in assignment of UB 330 to Theropithecus with very narrow inter-quartile ranges provides strong support for the identification of UB 330 as Theropithecus. In order to understand the morphological differences that may be driving the distinction between the genera, a scatter plot of the two first functions can be observed (Fig. 4) and analyzed in relation to the results of the stepwise linear DFA (Table 2B). The DFA plots indicate that the major separation along the first function, which explains 68.4% of the variance, is between the larger and terrestrial cercopithecine genera (Papio, Mandrillus, and Theropithecus), which score positive values on the first function, and the smaller and more arboreal genera (Macaca and M. Belmaker / Journal of Human Evolution xxx (2009) 1–11 Cercopithecus), which score negative values on the first function. While UB 330 scores clearly in the large terrestrial cercopithecine group, it occupies a unique position on the plot, specifically in relation to Theropithecus, and will be discussed later. The first function is affected primarily by Cal 20 (pedal power arm). Arboreal taxa such as Macaca have a shorter pedal power arm compared to more terrestrial taxa, since the ‘‘high gear’’ ratio contributes to increasing take off velocity required for leaping locomotion in comparison to a ‘‘lower gear’’ ratio, which is found in Figure 4. Bivariate plot of the first two axes of the Discriminant Function Analysis (DFA) separating the five cercopithecine genera and UB 330. The unique position of UB 330 is discussed in the text. Discriminant function 1 explains 68.4% of the total variance, and discriminant function 2 explains 21.1% of the total variance. Theropithecus gelada and T. oswaldi were grouped together in the analysis. Please cite this article in press as: Belmaker, M., The presence of a large cercopithecine (cf. Theropithecus sp.) in..., J Hum Evol (2009), doi:10.1016/ j.jhevol.2009.08.004
ARTICLE IN PRESS the more terrestrial locomotion of baboons (Strasser, 1992). However, pedal power arm is also positively correlated with body mass (Langdon, 1986; Strasser, 1992). Thus, we cannot exclude a body mass component in the distinction between groups of cercopithecine genera along the first function. The average body weight calculated for Macaca and Cercopithecus is ca. 5.5 kg compared to the average body weight of 21.3 kg for Papio, Mandrillus, and Theropithecus. The distinction along the second dimension, which accounts for only 21.1% of the variance, is more difficult to explain. In the smaller-bodied cercopithecine group, there is a gradient from negative to positive scores, from Macaca (a more terrestrial genus) to Cercopithecus (a more arboreal genus on average). In the larger taxa, a reverse trend is observed from negative to positive scores, from Mandrillus (which is the most arboreal), to Papio, and then Theropithecus, which is the most terrestrial. This similarity in positive scores between Cercopithecus and Theropithecus is surprising since both have different behavioral positions. Most of the Cercopithecus species sampled in this study are arboreal, and the two that score the highest on the second function of the DFA are C. mitis and C. ascanius, while Theropithecus is an extremely terrestrial species with a ‘‘shuffling forward bipedally’’ type of locomotion (Wrangham, 1980). The variable that most affected the second dimension is Cal 22, anterior height to anterior length of the calcaneus. An increase in height relative to length provides additional strength and robusticity to the calcaneus and suggests an adaptation to stresses in the sagittal plane produced by m. triceps surae (Langdon, 1986; Youlatos, 2003). A well-developed m. triceps surae provides the necessary force required for terrestrial locomotion, as opposed to the more slender m. triceps surae observed in more arboreal taxa (Strasser, 1988; Youlatos, 2003). Thus, it is not surprising that we observe the trend in the smaller-bodied cercopithecines. The more terrestrial Macaca score negatively (i.e., have higher anterior calcanei relative to length) while the more arboreal Cercopithecus have more positive scores (i.e., have shorter anterior calcanei relative to length). However, the results of the larger-bodied cercopithecines are more difficult to explain as it may have been expected that Theropithecus would score negatively on the second function. However, unlike other terrestrial cercopithecines, Theropithecus invert their feet much of the time while feeding, so a more agile and flexible ankle is advantageous, and perhaps convergent in some of its morphology to more arboreal forms (Krentz, 1993). Theropithecus shares with the arboreal Colobus an angulated medial malleolus and a pronounced notch for m. tibialis posterior, which aids in inverting the foot and increased flexibility of the ankle (Krentz, 1993). It is interesting to note that the score for UB 330 on the second function falls above any of the observed values for the comparative samples. This is supported by the fact that the two Theropithecus oswaldi from Kanjera score the highest on the second dimension within the Theropithecus sample (T. oswaldi mean ¼ 2.53, S.D. ¼ 1.279; T. gelada mean ¼ 0.84, S.D. ¼ 0.645). However, the two species do not differ significantly along the second dimension (twotailed student t-test P value >0.1), probably due to the low sample size of the comparative Theropithecus sample, making it difficult to evaluate the significance of the extreme value of UB 330. While probabilistically UB 330 is more similar to Theropithecus than other genera, the unique position of UB 330 along the second function may indicate either an undocumented high variability in Theropithecus calcaneal morphology reflective of variable locomotion patterns (Elton, 2002), or an otherwise unknown calcaneus of a fossil taxon, such as Paradolichopithecus. However, current assessments of the positional behavior of the latter taxon point to an increased terrestrial locomotion (Sondaar et al., 2006; E. Delson and W. Harcourt-Smith, pers. comm.), whereas T. oswaldi has been M. Belmaker / Journal of Human Evolution xxx (2009) 1–11 7 shown to have occupied a more arboreal habitat than modern T. gelada (Elton, 2002), and ‘‘shuffling forward bipedally’’ is an early locomotor adaptation in the Theropithecus lineage (Krentz, 1993), both of which support the former hypothesis. Body mass estimates The body mass for UB 330 was 25.56 kg based on the pedal power arm regression equation and 22.83 kg based on the calcaneal load arm regression equation (Strasser, 1992). Since DFA results indicated that UB 330 could be classified as a cercopithecine, the body size of UB 330 was compared to fossil and extant cercopithecines only. The body size estimates for UB 330 are higher than modern Cercopithecus and Macaca (both sexes). It is also higher than modern Mandrillus, Papio, and Theropithecus females but within the range of the males of these genera. It is only slightly above the range of modern Theropithecus males (Delson et al., 2000). This value is higher than Plio-Pleistocene fossil populations of Macaca in general (10–16 kg for males and 6.5–12.5 kg for females) and the ‘Ubeidiya Macaca sylvanus in particular (6.5–9.5 kg for females) (Delson et al., 2000). The body mass estimate is within the estimated range for T. oswaldi oswaldi, dated between 2.5–1.2 Ma, and obtained from both dental and postcranial measurements (13–36 kg for females and 20–86 kg for males) (Delson et al., 2000), and is consistent with the identification of UB 330 as Theropithecus (Table 4). However, it is also just within the estimated body size range for Paradolichopithecus avernensis females (12–23 kg) and males (25–41 kg) (Delson et al., 2000). Discussion The identification of primate fossil material to genus based on postcranial material alone is a difficult task. This study indicates that cercopithecid calcanei can be used to distinguish between subfamily and genera using both univariate and multivariate methods. The measurements of specimen UB 330 may have been a slight underestimation of the full adult size due to its adolescent age. However, the estimated adult length was probably only an additional 1–2 mm due to incomplete ossification of the epiphysis. Primate calcanei attain their adult shape by adolescence. Since Macaca sylvanus are smaller than other terrestrial Cercopithecinae, the comparisons with adult Macaca provide a conservative size comparison with UB 330. Based on the results in this study, UB 330 can be identified as a cercopithecine with a very high level of confidence. DFA analysis identified UB 330 as a cercopithecine with a posterior probability of nearly 90%. Of the cercopithecine genera analyzed, UB 330 differed significantly from Cercopithecus, Mandrillus, Papio, and Macaca. One sample t-test differed in one variable or more from each of these genera, and stepwise linear DFA classification results indicated that UB 330 could be classified as Cercopithecus, Mandrillus, or Macaca with a probability of less than 0.0001. Moreover, UB 330 fell above the estimated size range for Cercopithecus and Macaca as well as Mandrillus females. The distinction from Cercopithecus and Mandrillus is not surprising as their current and fossil biogeographic distribution is confined to sub-Sahara Africa (Pickford, 1987). The distinction from Macaca is of particular importance. Macaca has been previously found in ‘Ubeidiya (Tchernov and Volokita, 1986). Given the difference in size between UB 330 and other Macaca specimens at the site, specifically the Macaca calcaneus UB 101, the null hypothesis was that UB 330 represents a large male Macaca sylvanus. The DFA provides the most significant distinction along the first function, which separates the smaller-bodied taxa (Macaca and Cercopithecus) from the larger and more terrestrial Please cite this article in press as: Belmaker, M., The presence of a large cercopithecine (cf. Theropithecus sp.) in..., J Hum Evol (2009), doi:10.1016/ j.jhevol.2009.08.004
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