Salvaging fossil primates from an underwater cave

SALVAGING FOSSIL PRIMATES FROM AN UNDERWATER CAVE Final Report Submitted by A.L. Rosenberger Department of Anthropology and Archaeology Brooklyn College, CUNY

The primary objective of this project was to collect additional remains of a specimen of a subfossil primate that had been encountered in a freshwater-filled underwater cave in the Dominican Republic, and determine the paleontological potential of exploring other such caves in the area. The initial find of the monkey skeleton was made by a pair of highly experienced cave divers who came across a cranium on a casual dive. After making formal arrangements to collect with the Museo del Hombre Dominicano in Santo Domingo, and SEMARENA (the national environmental and natural resources secretariat of the Dominican Republic), and in collaboration with Dr. Renato Rimoli (Department of Biology, Universidad Autónoma de Santo Domingo), we subsequently recovered a beautifully preserved partial skeleton consisting of skull, limb bones, ribs and vertebrae. Under the auspices of the Leakey Foundation, we returned to the Dominican Republic to attempt a more complete recovery of this specimen, which proved successful. The essential scientific result, from which the majority of this report is taken, appears in Rosenberger et al. (2013).

The specimen, identified as Antillothrix bernenesis, was previously known only by three teeth, from an archaeological excavation about 25 km from the flooded cave site, recovered in the 1970s. The new subfossil material was found scattered in a small rubble pile on the floor of La Jeringa cave. Our second exploration of the recovery site produced the mandible, in excellent condition though not with all the teeth in place, and other postcranial elements.

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The most important specimen collected at this time was the lower jaw. Primate dentitions are rich with taxonomic and functional/adaptive information, and this specimen was the first well preserved mandible ever found of Antillothrix bernensis. (Another specimen, in relatively poor condition, had been reported from another locality, but has since been lost.) It is undistorted and the most complete mandible ever discovered of an extinct Caribbean platyrrhine, although there is one specimen, a hemi-mandible representing the Cuban Paralouatta, that has more teeth preserved in situ. Moreover, this specimen, following detailed study, provided crucial evidence that overturned previous, and somewhat ambiguous, interpretations of the affinities of A. bernensis that were actually based largely on the cranium – sans mandible – of the original La Jeringa find. This allowed us a more complete picture of the evolutionary history of Antillothrix because it revealed a pattern of mosaic evolution that was not hinted at in the morphology of the earlier discoveries.

We determined the species identity of the mandible by fitting it to the cranium, whose teeth closely matched the type specimen which also preserved upper teeth, and comparing the relative ages and degrees of dental wear from upper and lower molars of the Jeringa material.

Both elements belong to the same individual, a young adult. More broadly, of the extinct Caribbean platyrrhines the new jaw compares well with partial mandibles representing Xenothrix mcgregori, from Jamaica. This is a very important point for three reasons: 1) among platyrrhines, lower jaws are high diagnostic of phylogenetic relationships; 2) Xenothrix is a highly enigmatic subfossil known famously for its aberrant tooth morphology and odd limb structure; and, 3) cross-island resemblances among Caribbean fossils may offer a key to the biogeographic history of Xenothrix, which thus far is the only subfossil primate from Jamaica, the westernmost island of the Greater Antilles. Among living platyrrhines, the jaw closely

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resembles the functionally specialized and derived jaws of Callicebus and Aotus. This, too, is very important because it may tie the Dominican primate to a mainland radiation, which speaks to the higher order question of the origins of the whole primate fauna from a South American ancestry: who and when? Study of the lower molars of the new mandible brings out resemblances shared with the Haitian primate, Insulacebus tousantiana, a species known by a full dentition and a small jaw fragment. It is possible that these two Hispaniolan jaws, of Antillothrix and Insulacebus, share a pattern of derived features found elsewhere in Xenothrix, exclusively Taking into account the available craniodental and postcranial evidence, we find that Antillothrix is not properly classified as cebid related to monkeys like Cebus, Saimiri and the marmosets and tamarins, which is where it was placed before the jaw was found. Rather, it is very likely a pitheciid, related to sakis, ukaris, titi and owl monkeys. The latter hypothesis has long been an idea central to discussions of the phylogenetic affinities of the Greater Antillean primate fauna. Since the morphology of Antillothrix and Insulacebus also appears to be more primitive than the comparable parts of Xenothrix where they are known, it is tempting to surmise that the origins of the latter involved a vicariance or dispersal event involving nearby Hispaniola.

Funding from the Leakey Foundation, which led directly to the discoveries summarized above, has also enabled us to enlarge the program by obtaining additional research support from National Geographic/Waitt Foundation as well as an educational/outreach grant from USAID to help support infrastructure needs and local educational/outreach programs of the Museo del Hombre Domincano. The USAID funds will contribute to the first public exhibition of our subfossils in a major gallery space in the Museo, slated to open early in 2015. The impact is being felt by others in the paleontology community also, as the new collections we have made, of

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crocodyles for example, has attracted researchers making their first scientific visits to the DR, as well as inquiries from scientists in Argentina, Great Britain, Australia and the United States from various disciplines – paleontologists, geochronologists, speleo-geologists and molecular systematists. Our critical team of cave divers, now well experienced, continues to survey and they are finding new sites containing subfossils that we plan to explore.

And, the promise of underwater primate paleontology has stimulated are least one anthropology PhD graduate student (Zachary Klukkert, CUNY), who co-authored the analytical work on the mandible, to take up scuba diving. He has now formally passed an internationally sanctioned cave diving course and will soon be going down to the Dominican Republic to begin advance training in underwater fossil collecting without team. This, too, stems from the objective of our original Leakey Foundation proposal, to investigate, and hopefully demonstrate, the scientific potential of flooded caves for primate paleontology that others will come to exploit.

Publications resulting from Leakey Foundation support 2013 Rosenberger A.L., S.Z. Klukkert, S.B Cooke and R. Rimoli Rethinking Antilllothrix: the mandible and its implications. American Journal of Primatology. DOI: 10.1002/ajp.22144.

2013 Velazco, P., H. O’Neill, G. F. Gunnell, R. Rimoli, A. L. Rosenberger and N.B. Simmons. Quaternary Bat Diversity in the Dominican Republic. American Museum Novitates.

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