Susan M. Ford

Postcranial adaptations of the earliest platyrrhine

Abstract A model of the earliest platyrrhine primate is generated as the result of a cladistic analysis of platyrrhine relationships. The morphological features of the postcranium hypothesized as present in this model are analyzed in order to suggest the adaptations and behavioral repertoire of the first platyrrhine. A consistent pattern emerges indicating a grasping, arboreal quadruped, emphasizing walking and running on horizontal supports with only limited leaping or suspensory activities, approximately 1000 g in body mass. It is suggested that this pattern, with only minor changes, also characterized the earliest euprimates. The major derivations in the first platyrrhines were increased body size from a smaller euprimate ancestor, and improvements in stability as arboreal quadrupeds. The fossil record indicates that platyrrhines evolved as a distinct group before reaching South America, with possible relatives remaining behind in Africa.

Locomotor adaptations of fossil platyrrhines

Postcranial remains of extinet platyrrhines are now known from early and middle Miocene sites in Argentina, middle-to-late. Miocene sites in Colombia, and several late Pleistocene and recent caves in the Greater Antilles. While all of these fossils retain some primitive traints from their common platyrrhine ancestor, which most likely was a generalized, arboreal quadrupedal monkey, each has altered in some distinctive ways. Several specimens from Argentina suggest monkeys that engaged in a slightly increased frequency of leaping, but another indicates a monkey retaining a primarily quadrupedal mode of locomotion accompanied by increased climbing behaviors. The skeleton of Cebupithecia from Colombia indicates a monkey with a mixed behavioral repertoire, as in the extant Pithecia , including a greater emphasis on non-horizontal supports and well-developed adaptations for leaping as well as for more suspensory or climbing behaviors. The specimens from the West Indies are difficult to interpret, although two exhibit some features which might be interpreted as suggesting an increased tendency to leaping. Reconsideration of the polarity of traits in light of recent analyses of parapithecid fossils indicates most if not all hard tissue traits previously believed to be platyrrhine synapomorphies are in fact ancestral anthropoid traits. Thus, it is not possible at present to determine with certainty if any particular fossil, either from South America or elsewhere, was a member of the Platyrrhini.

Platyrrhine evolution in the West Indies

There are now at least three, and probably five to seven, distinct endemic platyrrhine species known from the Greater Antilles. All are of Late Pleistocene or Holocene age. These include at least three from Jamaica, the distinctive Xenothrix mcgregori and two others known only from proximal femora. All three are approximately the same size. One of these is also present on Hispaniola. Dental remains from several sites on Hispaniola all probably belong to “Saimiri” bernensis (which is likely not Saimiri). Postcranial remains from Hispaniola may not belong to the same monkey; their phenetic (but perhaps not phylogenetic) affinities are to callitrichids. Cuba also had two endemic platyrrhines, less changed from their mainland relatives, a howler monkey and a spider monkey (Ateles anthropomorphus). One or more of these lineages probably reached the islands prior to the Pleistocene, and almost certainly through dispersal (via rafting) and not vicariance or human transport.

A new ceboid femur from the late Pleistocene of Jamaica

ABSTRACT A portion of a proximal right femur from Coco Ree Cave, Jamaica, provides additional evidence of the primate radiation in the West Indies. The cave material is late Pleistocene and predates human occupation in the area. The specimen is slightly larger than the femur of Pithecia, within the range of other known Antillean primates. It differs markedly from the femora of large-bodied platyrrhines and is most similar in derived characters to those of the dwarfed callitrichids from South America. More than one platyrrhine lineage may be represented in the Greater Antillean fauna despite the apparent uniformity in body size of the known fossils.

Taxonomy of the Bornean Slow Loris, With New Species Nycticebus kayan (Primates, Lorisidae)

More species of nocturnal primates are now recognized than in the past, because many are cryptic species. Subtle morphological disparities, such as pelage pattern and color variation, vocal cues, and genetics have aided in elucidating the number of diagnosable species in a genus. The slow lorises (genus Nycticebus) once included only two species, but recent taxonomic studies resulted in the description of three additional species; further incompletely explored variability characterizes each of the currently described species. The Bornean loris in particular is characterized by pelage and body size variation. In this study, we explored facemask variation in the Bornean loris (N. menagensis). Differing facemask patterns, particularly influenced by the amount of white on the face, significantly clustered together by geographic regions, separated by notable geographic boundaries. Our results support the recognition of four species of Bornean lorises: N. menagensis, N. bancanus, N. borneanus, and N. kayan. Genetic studies are required to support these findings and to refine further our understanding of the marked variability within the Bornean loris populations. Am. J. Primatol. 75:46‐56, 2013.

Intraspecific, Interspecific, Metabolic, and Phylogenetic Scaling in Platyrrhine Primates

The relative scaling of body parts to body size is an important consideration in modern primatology. Allometric studies allow investigation of changes in shape that occur in conjunction with changes in body size separately from those independent of body size change, the latter often a result of significant new adaptations (Aiello, 1981; Gould, 1975).

The effects of ecology and evolutionary history on robust capuchin morphological diversity

Recent molecular work has confirmed the long-standing morphological hypothesis that capuchins are comprised of two distinct clades, the gracile (untufted) capuchins (genus Cebus, Erxleben, 1777) and the robust (tufted) capuchins (genus Sapajus Kerr, 1792). In the past, the robust group was treated as a single, undifferentiated and cosmopolitan species, with data from all populations lumped together in morphological and ecological studies, obscuring morphological differences that might exist across this radiation. Genetic evidence suggests that the modern radiation of robust capuchins began diversifying ∼2.5 Ma, with significant subsequent geographic expansion into new habitat types. In this study we use a morphological sample of gracile and robust capuchin craniofacial and postcranial characters to examine how ecology and evolutionary history have contributed to morphological diversity within the robust capuchins. We predicted that if ecology is driving robust capuchin variation, three distinct robust morphotypes would be identified: (1) the Atlantic Forest species (Sapajus xanthosternos, S. robustus, and S. nigritus), (2) the Amazonian rainforest species (S. apella, S. cay and S. macrocephalus), and (3) the Cerrado-Caatinga species (S. libidinosus). Alternatively, if diversification time between species pairs predicts degree of morphological difference, we predicted that the recently diverged S. apella, S. macrocephalus, S. libidinosus, and S. cay would be morphologically comparable, with greater variation among the more ancient lineages of S. nigritus, S. xanthosternos, and S. robustus. Our analyses suggest that S. libidinosus has the most derived craniofacial and postcranial features, indicative of inhabiting a more terrestrial niche that includes a dependence on tool use for the extraction of imbedded foods. We also suggest that the cranial robusticity of S. macrocephalus and S. apella are indicative of recent competition with sympatric gracile capuchin species, resulting in character displacement.

Species Definition and Differentiation as Seen in the Postcranial Skeleton of Cebus

A critical aspect of any study of evolutionary process is an understanding of the nature and distinctiveness of species. While species are generally recognized as real entities, the identification of members of a species remains problematic, particularly for members of a paleospecies. Most researchers seek analogues in the defining differences among modern species, but little of this work has focused on the postcranial skeleton. Recent studies have shown that most species differences are manifested in the soft tissue, but several studies have documented some hard tissue differences between closely related species.

2H stable isotope analysis of human tooth enamel: a new tool for forensic human provenancing?†

Stable isotope analysis of biogenic tissues such as tooth enamel and bone mineral has become a well-recognised and increasingly important method for determining the provenance of human remains, and it has been used successfully in bio-archaeological studies as well as forensic investigations. In particular, (18)O and (2)H stable isotope signatures of bone and hair, respectively, are well-established proxies of climate (temperature) and source water and are therefore considered as indicators of geographic life trajectories of animals and humans. While the methodology for (2)H analysis of human hair, fingernails, and bone collagen is currently used to determine human provenance, i.e. geographic origin and identify possible migration patterns, studies involving the analysis of (2)H in tooth enamel appear to be nonexistent in the scientific literature. Ground tooth enamel was analysed by continuous-flow isotope ratio mass spectrometry (IRMS) coupled on-line to a high-temperature conversion elemental analyser (TC/EA). An array of tooth enamel samples from archaeological and modern teeth has been analysed under different experimental conditions, and the results of this proof-of-concept study are presented. While no significant differences in (2)H abundance were noted as a result of H exchange studies or different sample preparation protocols, no significant differences or trends in measured δ(2)H-values were observed either with regard to known differences in geographical provenance. We concluded that the δ(2)H-values obtained from tooth enamel could not be used as proxy for a persons geographical origin during adolescence.

The Locomotor Behavior of Callicebus brunneus and Callicebus torquatus

This study presents data on the positional behavior of Callicebus torquatus and Callicebus brunneus collected from two different localities in Peru. C. brunneus primarily utilizes short-distance, bounding leaps, while C. torquatus relies predominantly on quadrupedal walking. Both species utilize small, horizontal and terminal branches more than any other substrate class. We relate the differences in locomotor behaviors between the two species to their utilization of different forest levels. C. brunneus tends to reside in the understory and brush layer forest levels. These more discontinuous strata necessitate higher frequencies of short-distance leaping. C. torquatus occupies the more continuous, interconnected canopy level, and much of its food is found in this level. Comparisons with other species show that Callicebus spp. locomote along smaller-sized, horizontal branches using quadrupedal progression and leaping.