Chilecebus: Oldest South American monkey

Flynn et al. 1995 brought us
Chilecebus carrascoensis (Early Miocene; 20mya; Fig. 1 lower left) a tiny New World monkey from Early Miocene Chile.

Figure 1. Chilcebus compared to other Western Hemisphere primates.

Figure 1. Chilcebus compared to other Western Hemisphere primates. Note the three molars in Chilecebus, as in Smilodectes and Aotus, not Alouatta. Dorsal view and CT scan view of Chilecebus on second of two frames.

When added to
the large reptile tree (LRT, 1753+ taxa) Chilecebus nested with the other South American monkeys.

Figure 1. At the start of the Eocene this is the distance monkeys would have to raft to get to South America. This hypothesis is invalidated by today's blogpost.

Figure 2. At the start of the Eocene this is the distance monkeys would have to raft to get to South America. This hypothesis is invalidated by today’s blogpost.

Worth remembering…
(since there IS this myth out there) there was no need for a monkey or two from Africa to raft over to South America (Fig. 2). The large reptile tree (LRT, 1753+ taxa) documents descent from Smilodectes (Fig. 1) an adapid living in Texas (Fig. 3).

Figure 3. The North Pole during the earliest Eocene from the CR Scotese Paleomap project with early primate skulls added, each demonstrating a gradual accumulation of traits.

Figure 3. The North Pole during the earliest Eocene from the CR Scotese Paleomap project with early primate skulls added, each demonstrating a gradual accumulation of traits.

Incrementally adding taxa to the LRT
has become less harrowing and more confident because there are no longer any large gaps, no odd enigmas, and lots of similar taxa for new specimens to nest alongside. By getting to this size the LRT has become a tool that no longer needs shaping, but can come out whenever needed to nest new specimens that others find difficult to understand. Even so, the LRT is still subject to constant scrutiny and polishing to further increase its usefullness.


References
Flynn J et al. 1995. An Early Miocene anthropoid skull from the Chilean Andes. Nature 373, 603 – 607.

wiki/Chilecebus

https://pterosaurheresies.wordpress.com/2018/12/10/the-lrt-solves-the-south-american-monkey-puzzle/

https://www.eurekalert.org/pub_releases/2019-08/amon-2ss081919.php

https://nypost.com/2019/08/22/what-a-20-million-year-old-monkey-skull-reveals-about-the-evolution-of-human-brains/

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