Newly‐discovered craniomandibular remains preserve the first known incisors of the extinct Dominican monkey Antillothrix bernensis

Antillothrix bernensis , an extinct platyrrhine primate from the Dominican Republic, has been under intensive study following a series of new finds from two flooded cave sites. To date, three nearly complete crania and one mandible have been described, but none of them preserve the anterior dentition. This study reports the first discovery of Antillothrix incisor teeth from two crania and three mandibles from a new flooded cave site in the Altagracia region of the Dominican Republic. The new fossils provide valuable data on the diet and phyletic affinities of Antillothrix . The craniodental traits of Antillothrix suggest a phyletic assignment within the family Pitheciidae due to similarities with the sclerocarpic harvester, Callicebus . Platyrrhine sclerocarpic harvesters are hard‐skinned‐fruit specialists that apply their anterior teeth to break down the outer husks of these foods to access the pulp and/or seeds within. Two hallmarks of this strategy are specialized anterior teeth and a vertically deep jaw that distributes stresses resulting from loads at the incisors and canine teeth during ingestion. Previously described Antillothrix material resembles Callicebus by sharing relatively short canine teeth and posteriorly expanded rami in their mandibles. Upper incisors in the new fossils are broad and spatulate but relatively small and short, more similar to those of atelids than sclerocarpic harvesters. The lower incisor crowns are also relatively short and lack the signature mesiodistally‐narrow shape found in pitheciids. In sum, the newly discovered fossils illustrate an anterior dental battery that is inconsistent with sclerocarpic harvesting or close affiliation with the extant pitheciids despite other similarities in the jaw and molar teeth. These results expand upon the conclusions from molar crown morphology – Antillothrix was a generalized frugivore that likely fed on soft and/or small fruits without intensive ingestive steps. The lack of derived features in the dentition accords with previous interpretations of various aspects of Antillothrix cranial morphology, e.g., small relative brain size and a vertically oriented nuchal plane, as being primitive for pitheciids or even for platyrrhines more generally. Altogether the craniodental traits of this enigmatic primate continues to preclude direct analogy with any extant platyrrhine. Support or Funding Information This work is supported by an Explorers Club Exploration Fund grant to ZSK. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .