New fossil materials of the earliest new world monkey, Branisella boliviana, and the problem of platyrrhine origins

Abstract

Branisella boliviana, from the Late Oligocene of Salla, Bolivia, is the oldest fossil platyrrhine monkey discovered. To date, several fossil specimens of Branisella have been obtained, but most of them are fragmentary dentitions, so the animals craniodental morphology is still obscure. During the 1996 field season a pair of upper and lower jaw fragments and another nearly complete mandible were recovered. These new fossil materials reveal the following morphological features in Branisella: 1) P(2) is much smaller than P(3,4), whereas P(2) is relatively small but probably sexually dimorphic; 2) the zygomatic arch protrudes smoothly posterolaterally from the maxillary bone, as in extant Callicebus; 3) the mandibular arcade is nearly V-shaped and the symphysial angle, which is formed by the horizontal plane and the anterior face of mandibular symphysis, is about 40 degrees, i.e., it neither leans as far anteriorly as in callitrichines nor does it stand as vertically as Cebus; 4) upper and lower molars wore down rapidly in life, suggesting a herbivorous diet and the possibility of terrestriality; and 5) dental eruptive sequence is the same as in extant Aotus. As a whole, the dentition of Branisella is very similar to that of Proteopithecus from the Late Eocene of Fayum, Egypt, except in the lower canine morphology, suggesting a close phyletic relationship between them. The origin and early diversification of platyrrhine monkeys might have occurred on the African continent before crossing the Atlantic Ocean.

Late Middle Eocene primate from Myanmar and the initial anthropoid colonization of Africa

“…Recent paleontological discoveries in Peru indicate that (at least) hystricognathous rodents achieved this feat remarkably early, during the middle Eocene (38). It is highly probable that platyrrhine primates followed the same dispersal pathway, but their South American fossil record does not begin until the late Oligocene (39,40). Therefore, the middle Eocene appears to be a critical interval for the intercontinental dispersal of land mammals, meriting additional fieldwork on all southern continents.…”

New perspectives on anthropoid origins

“…Proteopithecids (Proteopithecus, and possibly Serapia) have been linked with the oligopithecids Catopithecus and Oligopithecus (8), but postcranial evidence (31-33) does not support this link. Proteopithecids also exhibit some resemblance to platyrrhines (34), but a close phylogenetic relationship between these two groups is supported neither by character distribution (35) nor phylogenetic analyses (36). The most that can be said is that proteopithecids are stem anthropoids sufficiently primitive to have given rise to catarrhines, platyrrhines, both, or neither (13).…”

A New Platyrrhine from the Middle Miocene of La Venta, Colombia, and the Phyletic Position of Callicebinae.

“…Moreover, if the estimated divergence time for extant platyrrhines is actually 21.3 Ma, Branisella, the oldest fossil platyrrhine discovered from the latest Oligocene of Bolivia (about 26-27 Ma, MacFadden et al, 1985;Kay et al, 1998), should be excluded from the extant platyrrhine Glade. Although the phyletic position of Branisella has not yet been well established, several researchers have pointed out the resemblance between Branisella and callitrichine monkeys (Rosenberger et al, 1991;Takai and Anaya, 1996;Takai et al, 2000). The estimated divergence dates for platyrrhine clades seem to be too young for the estimations based on fossil records.…”