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Xenothrix mcgregori

Jamaican monkey
Temporal range: -Holocene

Extinct  (c.1500-1700) (IUCN 3.1)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Pitheciidae
Subfamily: Callicebinae
Tribe: Xenotrichini
Genus: Xenothrix
Williams & Koopman, 1952
Species: X. mcgregori
Binomial name
Xenothrix mcgregori

The Jamaican monkey (Xenothrix mcgregori) is an extinct species of New World monkey first uncovered at Long Mile Cave in Jamaica by Harold Anthony in 1919. Anthony is responsible for many species descriptions of Caribbean taxa during this period and his field notes record the discovery of the monkey material:

“January 17 – Spent all day digging in the long mile cave and secured some good bones. The most important find was the lower jaw and femur of a small monkey, found in the yellow limestone detritus. It was not associated with the human remains but not so far from them that the animal must not be strongly suspected as an introduced species. It was deeper than any of the human bones by at least 10” to 1’…” (reproduced in Williams and Koopman, 1952)

The eventual species description was not completed until 1952 when two graduate students, Ernest Williams and Karl Koopman, found the associated femur and mandibular fragment forgotten in a drawer at the American Museum of Natural History. They remained circumspect in placing this primate taxonomically as it had shared characteristics with a number of platyrrhine taxa.

The small mandible has a dental formula of 2 incisors, 1 canine, 3 premolars and 2 molars – a departure from the vast majority of living platyrrhines, with the notable exception of the callitrichines. It is significantly larger than the living callitrichines, and work by Rosenberger has largely eliminated the possibility that these taxa share a close phylogenetic relationship. Rosenberger suggested that the absence of the third molar in Xenothrix was not homologous with this character state in callitrichines. He based his assessment on the length of the molars relative to the molar row, and the inferred retention of hypocones on M1-2, which have been greatly reduced in the marmosets and tamarins. He further suggested that Xenothrix shared a close phylogenetic affinity with Callicebus or Aotus. His conclusions were tentative due to the fragmentary nature of the material.


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