Monday, July 18, 2016

[PaleoMammalogy• 2016] Canaanimico amazonensis • Neotropics provide Insights into the Emergence of New World Monkeys: New Dental Evidence from the late Oligocene of Peruvian Amazonia

Canaanimico amazonensis 
Marivaux, Adnet, Altamirano-Sierra, Boivin, Pujos, Ramdarshan, Salas-Gismondi, Tejada & Antoine, 2016

Recent field efforts in Peruvian Amazonia (Contamana area, Loreto Department) have allowed for the discovery of a late Oligocene (ca. 26.5 Ma; Chambira Formation) fossil primate-bearing locality (CTA-61). In this paper, we analyze the primate material consisting of two isolated upper molars, the peculiar morphology of which allows us to describe a new medium-sized platyrrhine monkey: Canaanimico amazonensis gen. et sp. nov. In addition to the recent discovery of Perupithecus ucayaliensis, a primitive anthropoid taxon of African affinities from the alleged latest Eocene Santa Rosa locality (Peruvian Amazonia), the discovery of Canaanimico adds to the evidence that primates were well-established in the Amazonian Basin during the Paleogene. Our phylogenetic results based on dental evidence show that none of the early Miocene Patagonian taxa (Homunculus, Carlocebus, Soriacebus, Mazzonicebus, Dolichocebus, Tremacebus, and Chilecebus), the late Oligocene Bolivian Branisella, or the Peruvian Canaanimico, is nested within a crown platyrrhine clade. All these early taxa are closely related and considered here as stem Platyrrhini. Canaanimico is nested within the Patagonian Soriacebinae, and closely related to Soriacebus, thereby extending back the soriacebine lineage to 26.5 Ma. Given the limited dental evidence, it is difficult to assess if Canaanimico was engaged in a form of pitheciine-like seed predation as is observed in Soriacebus and Mazzonicebus, but dental microwear patterns recorded on one upper molar indicate that Canaanimico was possibly a fruit and hard-object eater. If Panamacebus, a recently discovered stem cebine from the early Miocene of Panama, indicates that the crown platyrrhine radiation was already well underway by the earliest Miocene, Canaanimico indicates in turn that the “homunculid” radiation (as a part of the stem radiation) was well underway by the late Oligocene. These new data suggest that the stem radiation likely occurred in the Neotropics during the Oligocene, and that several stem lineages independently reached Patagonia during the early Miocene. Finally, we are still faced with a “layered” pattern of platyrrhine evolution, but modified in terms of timing of cladogeneses. If the crown platyrrhine radiation occurred in the Neotropics around the Oligocene-Miocene transition (or at least during the earliest Miocene), it was apparently concomitant with the diversification of the latest stem forms in Patagonia.

Keywords: Primates; Platyrrhines; South America; Amazonia; Phylogeny; Paleobiogeography

Systematic paleontology

Class: Mammalia Linnaeus, 1758
Cohort: Placentalia Owen, 1837

Order: Primates Linnaeus, 1758
Suborder: Anthropoidea Mivart, 1864
Infraorder: Platyrrhini Geoffroy Saint-Hilaire, 1812

Family: Homunculidae Ameghino, 1894 
Subfamily: Soriacebinae Kay, 2010

Canaanimico, new genus

Type and only known species: Canaanimico amazonensis, new species.

Etymology: Canaanimico comes from“Canaan”, the name of the Shipibo Native Community, and “mico”, the Spanish for monkey. The Canaan Community is located near the small city of Contamana, Loreto Department (Peruvian Amazonia); in recognition of the hospitality of the inhabitants of this community during our yearly fieldwork on their territory.

Diagnosis: As for the type and only known species (see below).

Canaanimico amazonensis, new species

Etymology: Refers to the Amazonian Basin. 

Type-locality: Contamana locus n61 (CTA-61), Cachiyacustream, Canaan territory, Contamana area, Loreto Department, Peru (Fig. 1).

Formation and Age: Chambira Formation (Kummel, 1948). In the sedimentological section of the Chambira Fm., CTA-61 is conformably situated 5 m above a tuffaceous silt, which is dated 26.56±0.07 Ma (late Oligocene, i.e., Deseadan SALMA) by radiometric U/Pb analyses performed on detrital zircon grains (Antoine et al., 2016a).

Figure 1. Geographic location and Cenozoic stratigraphy of the Contamana area, Peru.
A, location map of the Contamana area situated in Peruvian Amazonia (Loreto Department); B, synthetic stratigraphic units (both sides of the Maquía anticline) of the complete Contamana Cenozoic sequence through the Cachiyacu stream (modified after Antoine et al., 2016a: fig. 3), with the location of the fossil-bearing localities, notably the primate-bearing locality CTA-61 (see photograph [by L. Marivaux]). In the Cachiyacu stream section of the Chambira Fm., CTA-61 is conformably situated 5 m above a tuffaceous silt (CTA-08SA), which is dated at 26.56±0.07 Ma (late Oligocene; Deseadan SALMA) by radiometric U/Pb analyses performed on detrital zircon grains (Antoine et al., 2016a). The late Oligocene CTA-32 locality has also yielded a pollical phalanx of a primate (undescribed material,shown in Antoine et al., 2016a: fig. 8). Note also in the same section, the location of the primate-bearing locality CTA-43 in the Pebas Fm., which has yielded isolated teeth of primates documenting two new cebids (a medium-sized cebine and a tiny callitrichine; Antoine et al., 2016a,b; work in preparation). It is noteworthy that in the same section, in the underlying Pozo Fm. (formerly interpreted erroneously as Yahuarango Fm. in Antoine et al., 2012; see Antoine et al., 2016a), CTA-27 is a vertebrate-bearing locality, which has yielded the earliest caviomorph rodents known thus far (Antoine et al., 2012). Fm., Formation; R., River. 

Diagnosis: Medium-sized stem platyrrhine, similar in size to Homunculus patagonicus. Differs from all other homunculids (Homunculus, Soriacebus, Mazzonicebus, Carlocebus, Dolichocebus, and Tremacebus) in having M2 with a more transversecrown outline, a smaller hypocone, a shorter metacrista, thebuccal margins of the paracone and metacone less inflated (more steep-sided), a stronger development of the post-paracrista and premetacrista (except when compared with Soriacebus), in lacking the mesostyle, and in developing anaccessory cusp (neo-cusp) at the distal extremity of a strong and short postprotocrista. Differs more specifically from other members of the soriacebines (Soriacebus and Mazzonicebus) in lacking the prehypocrista on M2 (as in Dolichocebus), in displaying a weaker development (low and thin) of the latter creston M1, and in having a distal crown margin (M2), which isstraight rather than convex. As in soriacebines, M2 of Canaanimico lacks a paraconule and the development of a mesial cingulum, two characters which are present and well-developed in Homunculus, Carlocebus and Dolichocebus. As Mazzonicebus (but also Homunculus and Carlocebus), Canaanimico differs from Soriacebus in having stronger and more trenchant hypometacrista and hypoparacrista. In Canaanimico (as in Mazzonicebus), the hypoparacrista is lingually interrupted (short) and does not reach the preprotocrista (notably the point where aparaconule would normally occur), as is observed in Carlocebus and Homunculus (complete hypoparacrista linking the paraconeto the paraconule). Adult body weight estimated at ~2.0 kg on the basis of M2 area (MUSM-2499), using the regression equation provided by Gingerich et al. (1980, 1982), which is based on M1 size of generalized primates. 

 Laurent Marivaux, Sylvain Adnet, Ali J. Altamirano-Sierra, Myriam Boivin, François Pujos, Anusha Ramdarshan, Rodolfo Salas-Gismondi, Julia Tejada and Pierre-Olivier Antoine. 2016. Neotropics provide Insights into the Emergence of New World Monkeys: New Dental Evidence from the late Oligocene of Peruvian Amazonia.
 Journal of Human Evolution. 97; 159–175. DOI:  10.1016/j.jhevol.2016.05.011