A small mixodectid called Mixodectes ate mostly leaves and had skeletal characteristics adapted for living in trees. It weighed approximately 1.3 kg.
The same forest as the early primates, such Torrejonia Wilsoni (background), was occupied by Mixodectes Pungens (foreground). Image credit: Andrey Atuchin. Mixodectes Pungens ( ) lived on the western coast of North America in the Early Paleocene, 62 million year ago. This species, first described by Edward Drinker Cope in 1883, was known only from jawbone and teeth fragments. Yale University Professor Eric Sargis, along with his team, examined the most complete dentally-associated skeleton ever recovered from a mixodectid. The skeleton was found in the Nacimiento Formation, New Mexico. The 62 million-year-old mixodectid skeleton, which is of such high quality and completeness, offers new insights about the mixodectids. It also provides a clearer view of their evolution,” said Professor Sargis. Our findings indicate that these flying lemurs are closely related to primates, and that humans share a close relationship with them. The animal’s claws and limbs suggest that the creature was arboreal, capable of clinging vertically to branches and tree trunks. The crests on its molars were designed to help break down any abrasive materials, indicating that it was an omnivore and mostly ate leaves. This fossil skeleton offers new information about how the placental mammal population diversified after the extinction of dinosaurs, said Stephen Chester, researcher at Brooklyn College City University of New York, and Yale Peabody Museum. Mixodectes Pungens (19459005) was a large tree-dwelling primate in North America in the Early Paleocene. The new skeleton, for example, is much larger than a partially skeleton discovered next to it of Torrejonia wilsoni, a small mammal of an extinct primate group called plesiadapiforms.
While the Mixodectes pungens (19459005) subsisted mostly on leaves, that of Torrejonia wilsoni (19459005) was mainly fruit. The differences in diet and size suggest that the mixodectids were able to occupy a niche that was unique in Early Paleocene, which distinguished them from other tree dwelling mammals. The phylogenetic analysis performed by two researchers to determine the evolutionary relationship of mixodectids confirmed their status as euarchontans. Euarchontans are a group that includes treeshrews and primates. Professor Sargis stated that one of the analyses supported their being archaic primates while the other didn’t.
However, the second analysis confirmed that mixodectids were primatomorphans. This group is composed of primates, colugos and not treeshrews.
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S.G.B. Chester et al . 2025. A new remarkably complete Mixodectes shows arboreality of a large Paleocene primate mammal after the Cretaceous/Paleogene Mass Extinction. Sci Rep 15, 8041; doi: 10.1038/s41598-025-90203-z
