Locomotor Evolution of Mesopithecus (Primates: Colobinae) from Greece: Evidence from Selected Astragalar Characters
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Primates (2010) 51:23–35 DOI 10.1007/s10329-009-0161-2 ORIGINAL ARTICLE Locomotor evolution of Mesopithecus (Primates: Colobinae) from Greece: evidence from selected astragalar characters Dionisios Youlatos Æ George D. Koufos Received: 21 May 2009 / Accepted: 14 July 2009 / Published online: 14 August 2009 Ó Japan Monkey Centre and Springer 2009 Abstract This paper reports our investigations into slight preference of terrestrial substrates. The results functional aspects of the astragalus of four samples of the mainly conform to paleoenvironmental reconstructions of genus Mesopithecus from Greece. More particularly, it the fossiliferous localities and denote that Mesopithecus aims to infer substrate preferences of M. delsoni/pentelicus was mainly a semiterrestrial radiation throughout its from the Middle Turolian site of Perivolaki (central evolutionary history, with differential rates of use between Greece), M. pentelicus from the late Middle Turolian site arboreal and terrestrial substrates. These adaptations could of Pikermi (southern Greece), and M. cf. pentelicus and have promoted the dispersal of the genus throughout M. cf. monspessulanus from the Late Turolian site of Eurasia during the latest Miocene and Early Pliocene. Dytiko (northern Greece). For these purposes, selected astragalar functional features, such as trochlea wedging, Keywords Mesopithecus Á Colobinae Á Astragalus Á proximal facet curvature, and head rotation were expressed Functional morphology Á Locomotion Á Turolian Á as linear measurements on both fossil and selected extant Miocene Á Greece colobines. The size-adjusted measurements were used for univariate comparisons as well as a multivariate principal components analysis. Both approaches revealed that the Introduction selected characters were able to discriminate between extant arboreal and semiterrestrial colobines, but all fossil In this paper, we examine functional aspects of selected forms presented mosaic morphology. Thus, the oldest astragalar features of the Miocene colobine Mesopithecus representative, M. delsoni/pentelicus was reconstructed as from Greece. Previous reports analyzed combined astrag- mainly semiterrestrial. On the other hand, the astragalus of alar and calcaneal features of M. pentelicus from Pikermi M. pentelicus appeared to reflect semiterrestrial habits with by means of multivariate analyses (Youlatos 1999), as well a moderate adaptation to arboreality. Similar habitus as calcaneal features via univariate comparisons (Youlatos reconstruction was allocated to the more recent M. cf. 2003). The astragalus is a proximal foot bone that is fre- pentelicus, whereas the sympatric and synchronous M. cf. quently well preserved and considered as a good indicator monspessulanus showed semiterrestrial adaptations with a of locomotor and postural patterns. More particularly, fossil astragali have often been used to infer substrate preference in many fossil primates, and many astragalar D. Youlatos (&) features, such as the shape of the trochlea, the curvature of Department of Zoology, School of Biology, the proximal astragalocalcaneal facet, and the torsion angle Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece of the head, have been well described functionally e-mail: [email protected] (e.g. Szalay and Decker 1974; Conroy 1976; Szalay and Langdon 1986; Langdon 1986; Strasser 1988; Gebo 1989; G. D. Koufos Lewis 1989; Carrano 1997; Seiffert and Simons 2001). Laboratory of Geology and Palaeontology, Department of Geology, Aristotle University of Thessaloniki, Herein, we consider the functional morphology of 54124 Thessaloniki, Greece selected astragalar characters, aiming to trace the evolution 123 24 Primates (2010) 51:23–35 of locomotor behavior of the genus Mesopithecus in Greece throughout the Turolian (Late Miocene). Mesopi- thecus Wagner, 1839, is known from numerous cranial, dental, and postcranial specimens from many Eurasian Late Miocene to Late Pliocene sites (8.5–3 Ma), representing three or four different species (Delson 1975; Szalay and Delson 1979; de Bonis et al. 1990, 1997; Zapfe 1991; Jablonski 2002; Koufos et al. 2004; Delson et al. 2005; Harrison and Delson 2007; Pradella and Rook 2007; Tsoukala and Bartsiokas 2008; Koufos in press b). It appears to bear close affinities to Asian colobines (Szalay and Delson 1979; Hohenneger and Zapfe 1990; Zapfe 1991; Jablonksi 1998; Pan et al. 2004), but the primitive nature of its character still classifies it as Colobinae in- certae sedis (Szalay and Delson 1979; Strasser and Delson 1987; Jablonski 2002). For the purposes of our study, we examined the astragali of four samples of Mesopithecus, here considered as chronospecies, from different localities of the Turolian age in Greece. The oldest fossil material is attributed to M. delsoni/ pentelicus and was recently discovered in the Middle Turolian site of Perivolaki (MN-12) in central Greece, with a magnetostratigraphic record suggesting an age of 7.3– 7.1 Ma (Koufos 2006a; Koufos et al. 2006a). The richest known material belongs to M. pentelicus and originates from the classic late Middle Turolian locality of Pikermi (MN-12) in southern Greece (Gaudry 1862–1867; Szalay and Delson 1979; Zapfe 1991). The age of the Pikermi Fig. 1 Biochronological table of the Greek mammal localities bearing Mesopithecus fauna is still under debate, but an age of about 7.0 Ma is accepted by most authors (Koufos 2006b, 2008 b). Finally, to examine functional aspects of selected characters of rich fossil remains that are attributed to both M. cf. pen- the astragalus of the different intermediate forms of the telicus and M. cf. monspessulanus have been discovered in recognized species of Mesopithecus from Greece. The the Late Turolian sites of Dytiko 1, 2, 3 (DTK, DIT, DKO) inference of substrate preference via this functional anal- in the Axios valley of Macedonia, northern Greece, all of ysis will provide evidence for the evolution of locomotor MN-13 age, ca. 7–5.3 Ma (de Bonis et al. 1990, 1997; behavior and paleoecology of the genus in the Late Koufos et al. 2004; Koufos 2006b, in press a). All the Miocene in Greece and the Greco-Iranian paleobiogeo- known Mesopithecus-bearing Greek localities and their graphic province. geological ages are summarized in Fig. 1. These samples appear to represent different chronospecies, and perhaps intermediate forms between the recognized species of Methods Mesopithecus. Inferences of substrate preference of the recognized The fossil material consisted of 12 astragali (Table 1, forms of Mesopithecus vary, mainly due to the mosaic Fig. 2). For comparative purposes, we examined the character of their postcranium (Szalay and Delson 1979). astragali of 72 recent Colobinae representing eight genera The Early Turolian M. delsoni has been compared with and 19 species (Table 2). The extant specimens belong to terrestrial cercopithecids, inferring terrestrial habits. On the adult wild-shot individuals and are housed in the collec- other hand, habitus reconstruction for the Middle-Late tions of the Laboratoire d’Anatomie Compare´e and Labo- Turolian M. pentelicus varies from arboreal (Escarguel ratoire d’Anthropologie Biologique of the Muse´um 2005), semiterrestrial (Simons 1972; Szalay and Delson National d’Histoire Naturelle, Paris, France, and the 1979; Youlatos 1999; 2003) to terrestrial (Gaudry 1862; Mammal Collections, Department of Zoology, Natural Ko¨hler et al. 1999; Jablonski 2002). Lastly, the Early History Museum, London, UK. Each species was classified Pliocene M. monspessulanus has been suggested as rela- as semiterrestrial when activities were shared between tively arboreal (Szalay and Delson 1979). Our study aimed ground and trees or when there appeared to be great 123 Primates (2010) 51:23–35 25 Table 1 Fossil astragali of Museum Catalog no. Side Location Age Species Mesopithecus examined in this study LGPUT PER-1290 L Perivolaki Middle Turolian delsoni/pentelicus MNHN PIK-236 R Pikermi Middle Turolian pentelicus MNHN PIK-237 R Pikermi Middle Turolian pentelicus MNHN PIK-238 L Pikermi Middle Turolian pentelicus NHMW 1863-1/6 L Pikermi Middle Turolian pentelicus LGPUT Aristotle University of Thessaloniki, Laboratory of LPUW Unnumb. L Pikermi Middle Turolian pentelicus Geology and Paleontology, LGPUT DKO-72 R Dytiko 3 Late Turolian cf. pentelicus LPUW Laboratory of LGPUT DKO-171 L Dytiko 3 Late Turolian cf. pentelicus Paleontology, Universita¨t Wien, LGPUT DIT-82 L Dytiko 2 Late Turolian cf. pentelicus MNHN Laboratory of Paleontology, Muse´um National LGPUT DTK-277 L Dytiko 1 Late Turolian cf. pentelicus d’Histoire Naturelle, Paris, LGPUT DTK-279 R Dytiko 1 Late Turolian cf. pentelicus NHMW Naturhistorisches LGPUT DIT-76 R Dytiko 2 Late Turolian cf. monspessulanus Museum, Wien Cercopithecids—in general and in our case—colobines show unmistakable signs of terrestriality in their feet, as it seems clear that they have gone through a terrestrial phase in their evolution (Strasser 1988, 1992; Harrison 1989; Gebo 1989, 1993). Arboreal locomotion is hypothesized to have been secondarily developed (Harrison 1989; Strasser 1988, 1992), and tarsal morphology of arboreal species should differ only slightly from that of more terrestrial ones, rendering difficult any morphofunctional associations with substrate preferences. This would have been even more difficult when tarsal elements were considered, as in this report. For these reasons, we conducted a preliminary qualitative and quantitative study within the subfamily in order to assess those astragalar