Eric J. Sargis

New Paleocene skeletons and the relationship of plesiadapiforms to crown-clade primates

Plesiadapiforms are central to studies of the origin and evolution of primates and other euarchontan mammals (tree shrews and flying lemurs). We report results from a comprehensive cladistic analysis using cranial, postcranial, and dental evidence including data from recently discovered Paleocene plesiadapiform skeletons (Ignacius clarkforkensis sp. nov.; Dryomomys szalayi, gen. et sp. nov.), and the most plesiomorphic extant tree shrew, Ptilocercus lowii. Our results, based on the fossil record, unambiguously place plesiadapiforms with Euprimates and indicate that the divergence of Primates (sensu lato) from other euarchontans likely occurred before or just after the Cretaceous/Tertiary boundary (65 Mya), notably later than logistical model and molecular estimates. Anatomical features associated with specialized pedal grasping (including a nail on the hallux) and a petrosal bulla likely evolved in the common ancestor of Plesiadapoidea and Euprimates (Euprimateformes) by 62 Mya in either Asia or North America. Our results are consistent with those from recent molecular analyses that group Dermoptera with Scandentia. We find no evidence to support the hypothesis that any plesiadapiforms were mitten-gliders or closely related to Dermoptera.

Functional morphology of the hindlimb of tupaiids (Mammalia, Scandentia) and its phylogenetic implications.

In this study, the hindlimb of 12 species of tupaiids was analyzed functionally and compared to that of primates, dermopterans, and chiropterans. Many aspects of the tupaiid hindlimb vary in relation to differential substrate use. These differences include width of the ilium, shape of the acetabulum, size of the anterior inferior iliac spine, size of the greater and third trochanters, depth of the femoral condyles, shape of the patellar groove, and size of the tibial tuberosity. The hindlimb of the arboreal Ptilocercus lowii, the only ptilocercine, is better adapted for arboreal locomotion, whereas that of tupaiines is better adapted for rapid terrestrial (or scansorial) locomotion. The hindlimb of Ptilocercus seems to be habitually flexed and has more joint mobility, a condition necessary for movement on uneven, discontinuous arboreal supports. The tarsus of Ptilocercus facilitates inversion of the foot and its grasping hallux is capable of a great range of abduction. Tupaiines, on the other hand, are characterized by more extended hindlimbs and less mobility in their joints. These restricted joints limit movements more to the parasagittal plane, which increases the efficiency of locomotion on a more even and continuous surface like the ground. The hindlimb of tupaiines is adapted for powerful flexion and extension. Even the most arboreal tupaiines remain similar to terrestrial tupaiines in their hindlimb morphology, which probably reflects the terrestrial ancestry of Tupaiinae (but not Tupaiidae). Many attributes of the tupaiid hindlimb, especially those of the foot, reflect the arboreal ancestry of Tupaiidae and it is proposed that the ancestral tupaiid was arboreal like Ptilocercus. Also, compared to the hindlimb character states of tupaiines, those of Ptilocercus are more similar to those of other archontans, and it is proposed that the hindlimb features of Ptilocercus are primitive for the Tupaiidae. Hence, Ptilocercus should be considered in any phylogenetic analysis that includes Scandentia. J. Morphol. 254:149–185, 2002.

A New Genus of African Monkey, Rungwecebus: Morphology, Ecology, and Molecular Phylogenetics

A new species of African monkey, Lophocebus kipunji, was described in 2005 based on observations from two sites in Tanzania. We have since obtained a specimen killed by a farmer on Mount Rungwe, the type locality. Detailed molecular phylogenetic analyses of this specimen demonstrate that the genus Lophocebus is diphyletic. We provide a description of a new genus of African monkey and of the only preserved specimen of this primate. We also present information on the animals ecology and conservation.

The grasping behaviour, locomotion and substrate use of the tree shrews Tupaia minor and T. tana (Mammalia, Scandentia)

The grasping behaviour, locomotion and substrate use of the tree shrews Tupaia minor and T. tana were investigated in the Department of Zoological Research at the National Zoological Park in Washington, DC. Seven arboreal T. minor and five terrestrial T. tana were observed and videotaped for 10-min focal animal samples totalling 77 h of observation. Locomotion and substrate use were scored and images of grasping behaviour were captured from videotapes. Tupaia minor individuals were videotaped crossing dowels and the number of dowel crossings that included grasps were scored. In 84% of dowel crossings, T. minor individuals used either their hallux or their pollex to grasp the dowels. Tupaia minor was also more active, moved more quickly, was more arboreal, rooted less, reversed its feet more, flexed its forelimbs more and was more semi-plantigrade than T. tana . It is proposed that arboreal tupaiids, such as Ptilocercus lowii and T. minor , may represent better models for early primates than didelphid marsupials because they are capable of grasping and are more closely related to primates.

A preliminary qualitative analysis of the axial skeleton of tupaiids (Mammalia, Scandentia): functional morphology and phylogenetic implications

In this study, the axial skeleton of 14 species of tupaiids (tree shrews) was analysed functionally and compared to that of other archontan mammals. Several differences that relate to differential substrate use were found in the ribs and vertebrae. These differences included cranio-caudal width of the ribs; number of thoracic, lumbar, and caudal vertebrae; cranio-caudal width of the atlas; orientation of the spinous process of the axis; length and cranio-caudal width of the spinous processes of the thoracic vertebrae; length of the spinous processes of the lumbar vertebrae; length and orientation of the transverse processes of the lumbar vertebrae; and the number of sacral vertebrae that articulate with the ilia. The ribs and vertebrae of the arboreal Ptilocercus lowii, the only ptilocercine, exhibit adaptations for a stable thorax that probably facilitate bridging locomotion. The vertebral columns of tupaiines, on the other hand, are more mobile and allow more flexion and extension of the spine; this increased flexion and extension increases stride length, which in turn increases speed in bounding or galloping mammals such as terrestrial tupaiines. It is proposed here that the attributes of the thorax of Ptilocercus are primitive for the Tupaiidae, that the ancestral tupaiid was arboreal, that the tupaiine condition is derived, and that the ancestral tupaiine was terrestrial. It is also proposed that: Ptilocercus may be primitive for the Archonta in its axial skeletal features; a stable thorax was first evolved in an arboreal ancestral archontan; the adaptations for stability of the thorax were retained in the Volitantia (dermopterans and chiropterans) for certain locomotor types, including gliding or flying; a mobile thorax evolved in conjunction with the shift to graspleaping in the ancestral euprimate. These scenarios may be further tested by quantitative analyses of vertebral osteology, as well as myological analyses of the epaxial musculature.

The Postcranial Morphology of Ptilocercus lowii (Scandentia, Tupaiidae): An Analysis of Primatomorphan and Volitantian Characters

The eutherian orders Scandentia, Primates, Dermoptera, and Chiroptera have been grouped together by many morphologists, using various methods and data sets, into the cohort Archonta. Molecular evidence, however, has supported a clade (called Euarchonta) that includes Scandentia, Primates, and Dermoptera, but not Chiroptera. Within Archonta, some systematists have grouped Dermoptera and Chiroptera in Volitantia, while others have grouped Dermoptera and Primates in Primatomorpha. The order Scandentia includes the single family Tupaiidae, with two subfamilies, Ptilocercinae and Tupaiinae. Ptilocercinae is represented only by Ptilocercus lowii, which has been said to be the taxon most closely approximating the ancestral tupaiid. However, most researchers working on archontan phylogeny typically do not treat the order Scandentia as being polymorphic. They usually use Tupaia to represent Scandentia, despite the fact that Ptilocercus is quite distinct from Tupaia and has been argued to be the more plesiomorphic of the two taxa. In this study, a character analysis was performed on postcranial features that have been used to support the competing Primatomorpha and Volitantia hypotheses. In recognition of the polymorphic nature of Scandentia, taxonomic sampling within Scandentia was increased to include Ptilocercus. The postcranium of Ptilocercus was compared to that of tupaiines, euprimates, plesiadapiforms, dermopterans, and chiropterans. Several character states used to support either Primatomorpha or Volitantia, while not found in Tupaia, were found in Ptilocercus. While these features may have evolved independently in Ptilocercus, it is perhaps more likely that they represent features that first evolved in the ancestral archontan and were then lost in one of the extant orders. This character analysis greatly reduces the supportive evidence for the Primatomorpha hypothesis.

Evolutionary morphology of the Tenrecoidea (Mammalia) hindlimb skeleton

The tenrecs of Central Africa and Madagascar provide an excellent model for exploring adaptive radiation and functional aspects of mammalian hindlimb form. The pelvic girdle, femur, and crus of 13 tenrecoid species, and four species from the families Solenodontidae, Macroscelididae, and Erinaceidae, were examined and measured. Results from qualitative and quantitative analyses demonstrate remarkable diversity in several aspects of knee and hip joint skeletal form that are supportive of function‐based hypotheses, and consistent with studies on nontenrecoid eutherian postcranial adaptation. Locomotor specialists within Tenrecoidea exhibit suites of characteristics that are widespread among eutherians with similar locomotor behaviors. Furthermore, several characters that are constrained at the subfamily level were identified. Such characters are more indicative of postural behavior than locomotor behavior. J. Morphol., 2009.

The biogeography of introgression in the critically endangered African monkey Rungwecebus kipunji

In the four years since its original description, the taxonomy of the kipunji (Rungwecebus kipunji), a geographically restricted and critically endangered African monkey, has been the subject of much debate, and recent research suggesting that the first voucher specimen of Rungwecebus has baboon mitochondrial DNA has intensified the controversy. We show that Rungwecebus from a second region of Tanzania has a distinct mitochondrial haplotype that is basal to a clade containing all Papio species and the original Rungwecebus voucher, supporting the placement of Rungwecebus as the sister taxon of Papio and its status as a separate genus. We suggest that the Rungwecebus population in the Southern Highlands has experienced geographically localized mitochondrial DNA introgression from Papio, while the Ndundulu population retains the true Rungwecebus mitochondrial genome.

Lesula: A New Species of Cercopithecus Monkey Endemic to the Democratic Republic of Congo and Implications for Conservation of Congo’s Central Basin

In June 2007, a previously undescribed monkey known locally as “lesula” was found in the forests of the middle Lomami Basin in central Democratic Republic of Congo (DRC). We describe this new species as Cercopithecus lomamiensis sp. nov., and provide data on its distribution, morphology, genetics, ecology and behavior. C. lomamiensis is restricted to the lowland rain forests of central DRC between the middle Lomami and the upper Tshuapa Rivers. Morphological and molecular data confirm that C. lomamiensis is distinct from its nearest congener, C. hamlyni, from which it is separated geographically by both the Congo (Lualaba) and the Lomami Rivers. C. lomamiensis, like C. hamlyni, is semi-terrestrial with a diet containing terrestrial herbaceous vegetation. The discovery of C. lomamiensis highlights the biogeographic significance and importance for conservation of central Congo’s interfluvial TL2 region, defined from the upper Tshuapa River through the Lomami Basin to the Congo (Lualaba) River. The TL2 region has been found to contain a high diversity of anthropoid primates including three forms, in addition to C. lomamiensis, that are endemic to the area. We recommend the common name, lesula, for this new species, as it is the vernacular name used over most of its known range.

Additional molecular evidence strongly supports the distinction between the recently described African primate Rungwecebus kipunji (Cercopithecidae, Papionini) and Lophocebus

Department of Mammalogy, University of Alaska Museum, 907 Yukon Drive, Fairbanks, AK 99775, USA b Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA Department of Anthropology, Yale University, P.O. Box 208277, New Haven, CT 06520-8277, USA Division of Vertebrate Zoology, Peabody Museum of Natural History, Yale University, New Haven, CT 06520-8118, USA Department of Zoology, Field Museum of Natural History, 1400 S Lake Shore Drive, Chicago, IL 60605, USA Wildlife Conservation Society, Tanzania Program, P.O. Box 1475, Mbeya, Tanzania