Unclaimed Bodies in Anatomical Education: Medical Student Attitudes at One U.S. Medical Institution.

PHENOMENON: Dissection of cadavers is a common practice in anatomical education. To meet demand for cadavers, some medical institutions facilitate dissection of individuals who did not provide consent during their life. This includes the bodies of individuals who passed away with either no living kin or no kin able to claim and bury their body. Recent literature demonstrates widespread discomfort with this practice among anatomy course directors at U.S. institutions, bringing into question continuation of this practice. However, attitudes among medical students must similarly be assessed as they represent key stakeholders in the dissection process. The purpose of this study was to assess prevailing attitudes among a sample of medical students at one U.S. medical institution regarding the dissection of unclaimed bodies and identify emerging themes in ethical viewpoints. APPROACH: Two-hundred-twelve students (35% response rate) at one U.S. medical institution completed an anonymous online survey. Students came from different class cohorts at various stages of their training. Survey items were developed to capture students' academic and emotional experience with anatomical dissection and to identify emerging themes in attitudes. FINDINGS: Students reported high regard for cadaveric dissection in general with 170 (80%) respondents endorsing it as critical to anatomical education. Regarding dissection of unclaimed bodies, 30% of students found the practice ethical while 47% of students found the practice unethical. Multivariate analysis found that ethical view was directly associated with comfort level (OR= 156.16; 95% CI: 34.04, 716.40). Most students expressed comfort dissecting self-donated bodies (n = 206, 97%), while fewer students expressed comfort dissecting unclaimed bodies (n = 66, 31.1%). This latter finding significantly correlated with gender (t = 3.361. p < 0.05), class cohort (F = 3.576, p < 0.01), but not with religious affiliation or age. Thematic analysis revealed the following themes in student responses: (1) invoking ethical paradigms to either justify or condemn the practice, (2) subjective experiences, and (3) withholding judgment of the practice. INSIGHTS: Many students expressed negative attitudes toward the dissection of unclaimed bodies, with some citing issues of social vulnerability, justice, and autonomy. These findings indicate that many students' ethical code may conflict with institutional policies which permit this practice. Medical school represents a critical time in the professional development of trainees, and development practices which align with the moral code of local institutions and stakeholders is crucial.

Colonial Legacies Influence Biodiversity Lessons: How Past Trade Routes and Power Dynamics Shape Present-Day Scientific Research and Professional Opportunities for Caribbean Scientists.

AbstractScientists recognize the Caribbean archipelago as a biodiversity hotspot and employ it for their research as a natural laboratory. Yet they do not always appreciate that these ecosystems are in fact palimpsests shaped by multiple human cultures over millennia. Although post-European anthropogenic impacts are well documented, human influx into the region began about 5,000 years prior. Thus, inferences of ecological and evolutionary processes within the Caribbean may in fact represent artifacts of an unrecognized human legacy linked to issues influenced by centuries of colonial rule. The threats posed by stochastic natural and anthropogenically influenced disasters demand that we have an understanding of the natural history of endemic species if we are to halt extinctions and maintain access to traditional livelihoods. However, systematic issues have significantly biased our biological knowledge of the Caribbean. We discuss two case studies of the Caribbean's fragmented natural history collections and the effects of differing governance by the region's multiple nation states. We identify knowledge gaps and highlight a dire need for integrated and accessible inventorying of the Caribbean's collections. Research emphasizing local and international collaboration can lead to positive steps forward and will ultimately help us more accurately study Caribbean biodiversity and the ecological and evolutionary processes that generated it.

Temporomandibular joint shape in anthropoid primates varies widely and is patterned by size and phylogeny.

The temporomandibular joint is the direct interface between the mandible and the cranium and is critical for transmitting joint reaction forces and determining mandibular range of motion. As a consequence, understanding variation in the morphology of this joint and how it relates to other aspects of craniofacial form is important for better understanding masticatory function. Here, we present a detailed three-dimensional (3D) geometric morphometric analysis of the cranial component of this joint, the glenoid fossa, across a sample of 17 anthropoid primates, and we evaluate covariation between the glenoid and the cranium and mandible. We find high levels of intraspecific variation in glenoid shape that is likely linked to sexual dimorphism and joint remodeling, and we identify differences in mean glenoid shape across taxonomic groups and in relation to size. Analyses of covariation reveal strong relationships between glenoid shape and a variety of aspects of cranial and mandibular form. Our findings suggest that intraspecific variation in glenoid shape in primates could further be reflective of high levels of functional flexibility in the masticatory apparatus, as has also been suggested for primate jaw kinematics and muscle activation patterns. Conversely, interspecific differences likely reflect larger scale differences between species in body size and/or masticatory function. Results of the covariation analyses dovetail with those examining covariation in the cranium of canids and may be indicative of larger patterns across mammals.

Craniofacial fluctuating asymmetry in gorillas, chimpanzees, and macaques.

OBJECTIVES: Craniofacial fluctuating asymmetry (FA) refers to the random deviations from symmetry exhibited across the craniofacial complex and can be used as a measure of developmental instability for organisms with bilateral symmetry. This article addresses the lack of data on craniofacial FA in nonhuman primates by analyzing FA magnitude and variation in chimpanzees, gorillas, and macaques. We offer a preliminary investigation into how FA, as a proxy for developmental instability, varies within and among nonhuman primates. MATERIALS AND METHODS: We generated 3D surface models of 121 crania from Pan troglodytes troglodytes, Gorilla gorilla gorilla, and Macaca fascicularis fascicularis. Using geometric morphometric techniques, the magnitude of observed FA was calculated and compared for each individual, sex, and taxon, along with the variation of FA across cranial regions and for each bilateral landmark. RESULTS: Gorillas and macaques exhibited higher and more similar magnitudes of FA to each other than either taxon did to chimpanzees; variation in magnitude of FA followed this same trend. No significant differences were detected between sexes using pooled data across species, but sex did influence FA magnitude within taxa in gorillas. Further, variation in FA variance across cranial regions and by landmark was not distributed in any particular pattern. CONCLUSION: Possible environmentally induced causes for these patterns of FA magnitude include differences in growth rate and physiological stress experienced during life. Developmental stability may be greatest in chimpanzees in this sample. Additionally, these results point to appropriate landmarks for future FA analyses and may help suggest more urgent candidate taxa for conservation efforts.

Bolstering geometric morphometrics sample sizes with damaged and pathologic specimens: Is near enough good enough?

Obtaining coordinate data for geometric morphometric studies often involves the sampling of dry skeletal specimens from museum collections. But many specimens exhibit damage and/or pathologic conditions. Such specimens can be considered inadequate for the analyses of shape and are excluded from study. However, the influences that damaged specimens may have on the assessment of normal shape variation have only been explored in two-dimensional coordinate data and no studies have addressed the inclusion of pathological specimens to date. We collected three-dimensional coordinate data from the cranium and mandible of 100 crab-eating macaques (Macaca fascicularis). Tests typically employed to analyze shape variation were performed on five datasets that included specimens with varying degrees of damage/pathology. We hypothesized that the inclusion of these specimens into larger datasets would strengthen statistical support for dominant biological predictors of shape, such as sex and size. However, we also anticipated that the analysis of only the most questionable specimens may confound statistical outputs. We then analyzed a small sample of good quality specimens bolstered by specimens that would generally be excluded due to damage or pathologic morphology and compared the results with previous analyses. The inclusion of damaged/pathologic specimens in a larger dataset resulted in increased variation linked to allometry, sexual dimorphism, and covariation, supporting our initial hypothesis. We found that analyzing the most questionable specimens alone gave consistent results for the most dominant aspects of shape but could affect outputs for less influential principal components and predictors. The small dataset bolstered with damaged/pathologic specimens provided an adequate assessment of the major components of shape, but finer scale differences were also identified. We suggest that normal and repeatable variation contributed by specimens exhibiting damage and/or pathology emphasize the dominant components and shape predictors in larger datasets, however, the various unique conditions may be more influential for limited sample sizes. Furthermore, we find that exclusion of damaged/pathologic specimens can, in some cases, omit important demographic-specific shape variation of groups of individuals more likely to exhibit these conditions. These findings provide a strong case for inclusion of these specimens into studies that focus on the dominant aspects of intraspecific shape variation. However, they may present issues when testing hypotheses relating to more fine-scale aspects of morphology.

A novel method for quantifying femoral neck anteversion: A case study in extinct and extant sloths.

Extinct sloths represent a wide range of morphological, locomotor, and body size variation. Researchers have examined femoral neck angle in two dimensions to hypothesize locomotor behaviors in this group; however, this measure does not account for femoral neck anteversion. Here, we present a new method for quantifying femoral neck anteversion angle, in addition to femoral neck angle, to capture the 3D position of the femoral head/neck. Femora of extant (n = 21; Bradypus and Choloepus) and extinct (n = 49; Acratocnus, Megalocnus, Neocnus, and Parocnus) sloths were surface scanned and their surface models used to calculate three angles of femoral neck anteversion and femoral neck angle. Femoral neck anteversion was calculated as the angle between the femoral neck axis and the geometric axis of the femoral condyles (GA), the 35% cross section axis, and a trochanter axis. Femoral neck angle was calculated as the angle between the femoral neck and shaft axes. Genera were compared using ANOVAs with post hoc multiple comparisons for each angle. Femoral neck angle and femoral neck anteversion relative to the cross section were also analyzed. Significant differences among genera exist for all angles, (p < .001) but not all angles separate all genera. Femoral neck and anteversion angles typically yield different results, demonstrating the utility of analyzing both angles. The GA and cross section angles are highly correlated in sloths, with the exception of comparisons among Megalocnus, Parocnus, and Neocnus, suggesting morphological variation in the distal femur. While this method was applied to sloths, it has broad applicability to mammalian groups.

New insights on the anatomy and ontogeny of the largest extinct freshwater turtles.

There are many questions regarding the largest freshwater turtle that ever existed, including how its morphology changed during its ontogeny and how a single ecosystem was able to support more than one group of giant turtles. Here, we report the first individual preserving an associated skull and shell for Stupendemys geographica (currently the largest known side-necked turtle) and a nearly complete skull of Caninemys tridentata found in Miocene rocks of the Tatacoa Desert in Colombia. These two specimens indicate that more than two large freshwater turtle species shared a single ecosystem during the middle Miocene in northern South America. We also show the changes in the shell and scutes that occurred along the ontogeny of S. geographica, including a flattening of the carapace, constriction of the vertebral scutes, and increase in the height and thickness of the nuchal upturn wall; some of these changes are also evident in extant representatives of Podocnemididae, and have implications for a better understanding of their phylogeny.

Parvimico materdei gen. et sp. nov.: A new platyrrhine from the Early Miocene of the Amazon Basin, Peru.

Three field seasons of exploration along the Río Alto Madre de Dios in Peruvian Amazonia have yielded a fauna of micromammals from a new locality AMD-45, at ∼12.8°S. So far we have identified the new primate described here as well as small caviomorph rodents, cenolestoid marsupials, interatheriid notoungulates, xenarthrans, fish, lizards and invertebrates. The site is in the Bala Formation as exposed where the river transects a syncline. U-Pb dates on detrital zircons constrain the locality's age at between 17.1 ± 0.7 Ma and 18.9 ± 0.7 Ma, making the fauna age-equivalent to that from the Pinturas Formation and the older parts of the Santa Cruz Formation of Patagonian Argentina (Santacrucian). The primate specimen is an unworn M1 of exceptionally small size (equivalent in size to the extant callitrichine, Callithrix jacchus, among the smallest living platyrrhines and the smallest Eocene-Early Miocene platyrrhine yet recorded). Despite its small size it is unlike extant callitrichines in having a prominent cingulum hypocone. Based on the moderate development of the buccal crests, this animal likely had a diet similar to that of frugivorous callitrichines, and distinctly different from the more similarly-sized gummivores, Cebuella and C. jacchus. The phyletic position of the new taxon is uncertain, especially given the autapomorphic character of the tooth as a whole. Nevertheless, its unusual morphology hints at a wholly original and hitherto unknown Amazonian fauna, and reinforces the impression of the geographic separation of the Amazonian tropics from the more geographically isolated southerly parts of the continent in Early Miocene times.

Articular scaling and body mass estimation in platyrrhines and catarrhines: Modern variation and application to fossil anthropoids.

Body mass is an important component of any paleobiological reconstruction. Reliable skeletal dimensions for making estimates are desirable but extant primate reference samples with known body masses are rare. We estimated body mass in a sample of extinct platyrrhines and Fayum anthropoids based on four measurements of the articular surfaces of the humerus and femur. Estimates were based on a large extant reference sample of wild-collected individuals with associated body masses, including previously published and new data from extant platyrrhines, cercopithecoids, and hominoids. In general, scaling of joint dimensions is positively allometric relative to expectations of geometric isometry, but negatively allometric relative to expectations of maintaining equivalent joint surface areas. Body mass prediction equations based on articular breadths are reasonably precise, with %SEEs of 17-25%. The breadth of the distal femoral articulation yields the most reliable estimates of body mass because it scales similarly in all major anthropoid taxa. Other joints scale differently in different taxa; therefore, locomotor style and phylogenetic affinity must be considered when calculating body mass estimates from the proximal femur, proximal humerus, and distal humerus. The body mass prediction equations were applied to 36 Old World and New World fossil anthropoid specimens representing 11 taxa, plus two Haitian specimens of uncertain taxonomic affinity. Among the extinct platyrrhines studied, only Cebupithecia is similar to large, extant platyrrhines in having large humeral (especially distal) joints. Our body mass estimates differ from each other and from published estimates based on teeth in ways that reflect known differences in relative sizes of the joints and teeth. We prefer body mass estimators that are biomechanically linked to weight-bearing, and especially those that are relatively insensitive to differences in locomotor style and phylogenetic history. Whenever possible, extant reference samples should be chosen to match target fossils in joint proportionality.

Evaluating causes of error in landmark-based data collection using scanners.

In this study, we assess the precision, accuracy, and repeatability of craniodental landmarks (Types I, II, and III, plus curves of semilandmarks) on a single macaque cranium digitally reconstructed with three different surface scanners and a microCT scanner. Nine researchers with varying degrees of osteological and geometric morphometric knowledge landmarked ten iterations of each scan (40 total) to test the effects of scan quality, researcher experience, and landmark type on levels of intra- and interobserver error. Two researchers additionally landmarked ten specimens from seven different macaque species using the same landmark protocol to test the effects of the previously listed variables relative to species-level morphological differences (i.e., observer variance versus real biological variance). Error rates within and among researchers by scan type were calculated to determine whether or not data collected by different individuals or on different digitally rendered crania are consistent enough to be used in a single dataset. Results indicate that scan type does not impact rate of intra- or interobserver error. Interobserver error is far greater than intraobserver error among all individuals, and is similar in variance to that found among different macaque species. Additionally, experience with osteology and morphometrics both positively contribute to precision in multiple landmarking sessions, even where less experienced researchers have been trained in point acquisition. Individual training increases precision (although not necessarily accuracy), and is highly recommended in any situation where multiple researchers will be collecting data for a single project.

New cranium of the endemic Caribbean platyrrhine, Antillothrix bernensis, from La Altagracia Province, Dominican Republic.

Recent paleontological collection in submerged caves in the eastern Dominican Republic has yielded new specimens of Antillothrix bernensis. Here we describe a complete cranium of an adult individual (MHD 20) and provide phenetic comparisons to other endemic Caribbean taxa and extant mainland platyrrhines using three-dimensional geometric morphometric methods (3DGM). Qualitative and quantitative comparisons support conclusions based on other recently described fossil material: Antillothrix has a dentition lacking clear dietary specialization, an elongated brain case with strong temporal lines, and a vertically oriented nuchal plane. MHD 20 shares a combination of traits with a previously published subadult specimen (MHD 01) including a deep depression at glabella, dorsoventrally elongated orbits, and a relatively large face. This shared morphology reinforces the taxonomic affinity of the two specimens, with differences between the two likely reflecting the younger ontogenetic age of MHD 01. Comparisons to the extant platyrrhines paint a complicated picture as the results of between-group principal components analyses (bgPCA) indicate that Antillothrix does not share a suite of morphological features exclusively with any one genus. Depending on which bgPC axes are visualized, and which subset of landmarks is included (i.e., only those describing the shape of the face/palate for inclusion of Xenothrix), MHD 20 is most similar in shape to the atelids, Alouatta, Lagothrix, and Brachyteles, or an otherwise "empty" region of shape space. It groups neither with Cebus nor Callicebus, two taxa that Antillothrix has been associated with in previous studies based on much less complete material. The Antillothrix cranium does not exhibit any of the derived characters classically used to diagnose or define any single clade; rather its morphology shares features with multiple platyrrhine groups. This is consistent with the interpretation that Antillothrix preserves a primitive morphology, which accords with the hypothesis positing an early arrival of platyrrhines in the Caribbean.

New endemic platyrrhine humerus from Haiti and the evolution of the Greater Antillean platyrrhines.

Much debate surrounds the phylogenetic affinities of the endemic Greater Antillean platyrrhines. Thus far, most phylogenetic analyses have been constructed and tested using craniodental characters. We add to this dialog by considering how features of the distal humerus support or refute existing hypotheses for the origins of fossil Caribbean primates, utilizing three-dimensional geometric morphometric data in combination with character based cladistic analyses. We also add to the sample of fossil platyrrhine humeri with the description of UF 114718, a new distal humerus from Haiti. We reconstruct UF 114718 to be a generalized, arboreal quadruped attributed to the species Insulacebus toussantiana. Our results from phylogenetic analyses lend some support to the idea that some Greater Antillean fossil taxa including Xenothrix mcgregori, Antillothrix bernensis, and Insulacebus toussaintiana could form a monophyletic clade that is sister to either extant Platyrrhini or basal pitheciids. Based on the distal humeral data, we reconstruct the earliest ancestral platyrrhine to be a generalized, arboreal quadruped that potentially emphasized pronated arm postures during locomotion and may have engaged in some limited climbing, most similar in shape to early anthropoids and some of the earliest Antillean forms. However, aspects of shape and standard qualitative characters relating to the distal humerus seem to be variable and prone to both homoplasy and reversals; thus these results must be interpreted cautiously and (where possible) within the context provided by other parts of the skeleton.

1.32 ± 0.11 Ma age for underwater remains constrain antiquity and longevity of the Dominican primate Antillothrix bernensis.

Endemic New World monkeys are an important element of the extinct mammal faunas of the Caribbean's Greater Antilles. Here we report the first geochronometric evidence that the primate Antillothrix bernensis existed in the Dominican Republic during the Pleistocene, based on the uranium-series age of carbonate speleothem that encased a tibia when it was collected in a flooded cave. Three-dimensional geometric morphometrics of laser-scanned living and extinct samples provide evidence to support the hypothesis that this specimen and other Dominican primate tibial remains belong to that same species. U-Th dating of the host cave carbonate returns ages consistently at the 600 ka upper limit of the technique. However, U-Pb, capable of resolving ages of greater antiquity, is more robust in this context, returning a secure age of 1.32 ± 0.11 Ma, which is the oldest chronometric age recorded for a Hispaniolan mammal. While its origins and manner and time of arrival are obscure, the morphometric studies are consistent with phylogenetic analyses that place A. bernensis within the pitheciid clade of the platyrrhines. The species apparently endured for over 1 million years during the climatic perturbations of the Pleistocene, as a frugivorous climbing quadruped, one of two known primate species occupying the hazard prone island of Hispaniola.

Dietary inference from upper and lower molar morphology in platyrrhine primates.

The correlation between diet and dental topography is of importance to paleontologists seeking to diagnose ecological adaptations in extinct taxa. Although the subject is well represented in the literature, few studies directly compare methods or evaluate dietary signals conveyed by both upper and lower molars. Here, we address this gap in our knowledge by comparing the efficacy of three measures of functional morphology for classifying an ecologically diverse sample of thirteen medium- to large-bodied platyrrhines by diet category (e.g., folivore, frugivore, hard object feeder). We used Shearing Quotient (SQ), an index derived from linear measurements of molar cutting edges and two indices of crown surface topography, Occlusal Relief (OR) and Relief Index (RFI). Using SQ, OR, and RFI, individuals were then classified by dietary category using Discriminate Function Analysis. Both upper and lower molar variables produce high classification rates in assigning individuals to diet categories, but lower molars are consistently more successful. SQs yield the highest classification rates. RFI and OR generally perform above chance. Upper molar RFI has a success rate below the level of chance. Adding molar length enhances the discriminatory power for all variables. We conclude that upper molar SQs are useful for dietary reconstruction, especially when combined with body size information. Additionally, we find that among our sample of platyrrhines, SQ remains the strongest predictor of diet, while RFI is less useful at signaling dietary differences in absence of body size information. The study demonstrates new ways for inferring the diets of extinct platyrrhine primates when both upper and lower molars are available, or, for taxa known only from upper molars. The techniques are useful in reconstructing diet in stem representatives of anthropoid clade, who share key aspects of molar morphology with extant platyrrhines.

Form and function in the platyrrhine skull: a three-dimensional analysis of dental and TMJ morphology.

Cranial and temporomandibular joint (TMJ) form has been shown to reflect masticatory forces and mandibular range of motion, which vary in relation to feeding strategy. Similarly, the dentition, as the portion of the masticatory apparatus most directly involved in triturating food items, strongly reflects dietary profile. Fine control over condylar and mandibular movements guides the teeth into occlusion, while the topography and position of the dental arcade mediate mandibular movements. We hypothesize that masticatory, and particularly TMJ, morphology and dental form covary in predictable ways with one another and with diet. We employed three-dimensional geometric morphometric techniques to examine inter-specific variation in ten platyrrhine species. Landmarks were collected on six datasets describing the upper and lower molars, cranium, glenoid fossa, mandible, and mandibular condyle; two-block partial least squares analyses were performed to assess covariation between cranial morphology, dentition, and diet. Significant relationships were identified between the molars and the cranium, mandible, and glenoid fossa. Some of these shape complexes reflect feeding strategy; for example, higher crowned/cusped dentitions, as found in primates consuming larger quantities of structural carbohydrates (e.g., Alouatta and Saimiri), correspond to anteroposterior longer and deeper glenoid fossae. These results indicate strong covariance between dental and TMJ form, aspects of which are related to feeding behavior. However, other aspects of morphological variation display a strong phylogenetic signal; we must therefore examine further ways in which to control for phylogeny when examining covariation in interspecific masticatory form.

Form, function, and geometric morphometrics.

Geometric morphometrics (GM) has increasingly become an important tool in assessing and studying shape variation in a wide variety of taxa. While the GM toolkit has unparalleled power to quantify shape, its use in studies of functional morphology have been questioned. Here, we assess the state of the field of GM and provide an overview of the techniques available to assess shape, including aspects of visualization, statistical analysis, phylogenetic control, and more. Additionally, we briefly review the history of functional morphology and summarize the main tools available to the functional morphologist. We explore the intersection of geometric morphometrics and functional morphology and we suggest ways that we may be able to move forward in profitably combining these two research areas. Finally, this paper provides a brief introduction to the papers in this special issue and highlights the ways in which the contributing authors have approached the intersection of GM and functional morphology.

Dental topography of platyrrhines and prosimians: convergence and contrasts.

Dental topographic analysis is the quantitative assessment of shape of three-dimensional models of tooth crowns and component features. Molar topographic curvature, relief, and complexity correlate with aspects of feeding behavior in certain living primates, and have been employed to investigate dietary ecology in extant and extinct primate species. This study investigates whether dental topography correlates with diet among a diverse sample of living platyrrhines, and compares platyrrhine topography with that of prosimians. We sampled 111 lower second molars of 11 platyrrhine genera and 121 of 20 prosimian genera. For each tooth we calculated Dirichlet normal energy (DNE), relief index (RFI), and orientation patch count (OPCR), quantifying surface curvature, relief, and complexity respectively. Shearing ratios and quotients were also measured. Statistical analyses partitioned effects of diet and taxon on topography in platyrrhines alone and relative to prosimians. Discriminant function analyses assessed predictive diet models. Results indicate that platyrrhine dental topography correlates to dietary preference, and platyrrhine-only predictive models yield high rates of accuracy. The same is true for prosimians. Topographic variance is broadly similar among platyrrhines and prosimians. One exception is that platyrrhines display higher average relief and lower relief variance, possibly related to lower relative molar size and functional links between relief and tooth longevity distinct from curvature or complexity. Explicitly incorporating phylogenetic distance matrices into statistical analyses of the combined platyrrhine-prosimian sample results in loss of significance of dietary effects for OPCR and SQ, while greatly increasing dietary significance of RFI.

Rethinking Antillothrix: the mandible and its implications.

A mandible of the Hispaniolan primate Antillothrix bernensis, virtually complete and providing the only definitive evidence of the species' lower dentition, has been discovered in a submerged Dominican Republic cave. The new specimen enables a more certain assessment of the species' phylogenetic position than previously possible. It belongs to the same individual as the nearly complete young adult cranium and postrcranial elements found earlier at the same site. Of the extinct Caribbean platyrrhines, the jaw compares well with partial mandibles representing Xenothrix mcgregori, from Jamaica. Among living platyrrhines, it closely resembles Callicebus and Aotus, as documented in a biometric analysis employing three-dimensional geometric morphometrics of Callicebus, Aotus, Pithecia, Chiropotes, Cacajao, Cebus, and Saimiri. The jaw falls within the morphological variability of Callicebus and Aotus in this three-dimensional analysis, is otherwise most similar to Pithecia, and is distinct from cebines. Lower molars resemble the Haitian primate, Insulacebus, a genus known by a full dentition and gnathic fragments with a pattern of derived features also present in Xenothrix. Considering the available craniodental and postcranial evidence, we conclude that Antillothrix is not properly classified as cebid but rather is best grouped with Pitheciidae, an idea long central to discussions of the phylogenetic affinities of the Greater Antillean primates. Since Antillothrix and Insulacebus are more primitive anatomically than the highly modified Xenothrix, it is tempting to surmise that the origins of the latter involved a vicariance or dispersal event via Hispaniola isolating it on Jamaica.

The making of platyrrhine semifolivores: models for the evolution of folivory in primates.

Among living New World monkeys, Howlers and Muriquis are by far the most folivorous. We examine how well the morphology and behavior of Alouatta and Brachyteles conform to leaf-eating adaptational models derived from other studies. Both genera match these expectations unevenly, which suggests a broader conception of primate folivory is in order. Hence the notion of "semifolivory." While their dentitions prove highly sensitive to selection for leaf-eating, core features relating to body size, brain size, ranging behavior and presumed energy budgets are less predictable corollaries. Leaf-eating in atelines and colobines may have evolved from a preadaptive reliance on seed-eating, which would have necessitated comparable gastric adaptations. Fossils suggest semifolivory in the low-energy Howler lineage may have begun with an increase in body size, a relatively small brain and, possibly, a concomitantly enlarged gut, followed by dental adaptations. It may have advanced via body-size reduction, part of a pioneering adaptation in marginal ecologies on the periphery of rich Amazonian habitats or as a strategy to minimize competition among an abundance of frugivores within the lowland forest-perhaps not as a fallback scheme. In the high-energy Muriqui, semifolivory may have evolved in more intensely seasonal, low-yield forests where frugivores were constrained and rare, a model more consistent with the fallback paradigm. The seed-to-leaves evolutionary pathway hypothesized for anthropoid leaf-eaters may be a widespread phenomenon in primates. We propose it is ultimately rooted in a pre-euprimate reliance on the seeds and seed coats of primitive angiosperms before the latter evolved attractive sugary fruits to coax primates into becoming dispersers of seeds, instead consumers.