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| Figure 1: An artistic rendition of a Purgatorius species (Image Credit: Andrey Atuchin) |
Today’s blog post will discuss some revolutionary news that has come out over the past few years in regards to primate ancestors, specifically those known as the plesiadapiforms (Figure 1). For current and/or former students of physical anthropological or evolutionary biology courses this name should sound familiar. There had been much previous study on these species, but this knowledge was based on small samples of largely fossilized teeth. A recent discovery of tarsal (ankle) bones and teeth, however, has broadened our knowledge of these species and provides greater insights into the origins of all primates.
Plesiadapiforms belong to the genus known as Purgatorius. It was originally believed that they evolved 66 million years ago (MYA), about 100,000 years after the extinction of the dinosaurs. They were characterized as being small bodied primates with long snouts and specialized diets, subsisting on either insects or fruit based on extensive analyses of fossilized teeth. They were also believed to have been largely terrestrial, a conclusion that was based on no substantive evidence as the teeth were the only remains discovered.
That was until recently when the discovery of two tarsal (ankle) bones opened up new avenues of research that broadened the current understanding of Plesiadapiform species. Extensive analysis of the tarsal bones demonstrate that these species were not terrestrial but instead arboreal, upending a long held assumption that primates evolved to be tree dwellers over time. Instead, this evidence demonstrates that primates just adapted to be better able to navigate and survive in the trees, eventually moving onto land several millennia later.
Additional discoveries of new fossilized teeth also provided new insights into the plesiadapiforms, specifically in the identification of a new species and a more definitive timeline for when plesiadapiforms first evolved. Teeth discovered in Montana confirmed the existence of a previously known species, Purgatorius janisae, but also led to the naming of a new species, Purgatorius mckeeveri. The latter was named after the family who had been supporting area excavations for some time.
Even more exciting was the discovery that these fossilized remains showed that plesiadapiforms were the oldest primates, and that these ancestral primates may have lived among dinosaurs prior to their extinction! Unfortunately, this also may account for how and why the went extinct around 56 MYA. This was most likely the result of being too adapted to their climatic and environmental conditions and being unable to adapt to the rapidly changing environmental conditions they existed in. Regardless, these new pieces of evidence provide new information into primate origins and greater knowledge into what exactly makes up the Primate order.
Bibliography
Chester, S. G., Bloch, J. I., Boyer, D. M., & Clemens, W. A. (2015). Oldest known euarchontan tarsals and affinities of Paleocene Purgatorius to Primates. PNAS, 1487-1492.
News Staff. (2021, March 1). 65-Million-Year-Old Primate Fossils Uncovered in Montana. Retrieved from Sci News: http://www.sci-news.com/paleontology/purgatorius-fossils-montana-09402.html
No Author. (2021, February 24). Earliest-known fossil primate discovered in Montana. Retrieved from The Leakey Foundation: https://leakeyfoundation.org/earliest-known-fossil-primate-discovered-in-montana/?fbclid=IwAR05TLfQNZbLaYmNrDjemMGr5PmhFsXqlUDb6WlGUjrNPp117bQt5_0UK-M
Shelton, J. (2015, January 19). Fossil ankles indicate Earth’s earliest primates lived in trees. Retrieved from Yale News: https://news.yale.edu/2015/01/19/fossil-ankles-indicate-earth-s-earliest-primates-lived-trees
3 comments:
I have read about this creature before, I remember that small creatures such as these are difficult to find fossils of given the small fragile skeletons not surviving fossilization. But what I had learned was that these animals were terrestrial, I had not realized that the Purgatorius were now classified as being arboreal. Another reason why I chose Paleontology as my dream job, to be able to illuminate the features of animals extinct for thousands of years would be very rewarding.
I learned from this blog post that plesiadapiforms are the oldest primates and possibly lived amongst dinosaurs. This is an impressive discovery! Although information on the species remains limited, being able to compare the oldest primate to extant primates will release a lot of useful information about our evolution. -Tala Caples
The recent discovery of tarsal bones and teeth has revolutionized our understanding of these species, challenging long-held assumptions and opening up new avenues for research. It’s particularly interesting to learn that these primates were arboreal rather than terrestrial, which significantly changes our perspective on primate evolution.
-Ahmesha Johnson
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