A study published by Scientific Rreports sheds light on the anatomy, behavior, and evolutionary significance of Mixodectes pungens, an ancient mammal that lived shortly after the extinction of the dinosaurs.
A new examination of the most complete skeleton of Mixodectes pungens answered many lingering questions about the species. The specimen includes a partial skull with teeth, spinal column, rib cage, forelimbs, and hind limbs, offering novel insights into its anatomy and ecological niche.
The specimen studied represents a mature adult that weighed about three pounds. Body mass was estimated at approximately 1,370 grams based on femoral length measurements. The anatomy of its limbs and claws suggests that Mixodectes pungens was an arboreal animal, specialized for life in trees. Its physical characteristics were adapted for grasping trunks and branches, indicating it could vertically cling to tree trunks and branches, detailed Tech Explorist.
By analyzing the molar teeth, which had crests suited for breaking down tough vegetation, researchers concluded that Mixodectes pungens had a predominantly herbivorous diet, primarily feasting on leaves. This dietary preference highlights the importance of vegetation in its habitat during the Paleocene epoch.
The study was led by Yale anthropologist Eric Sargis and co-authored by Stephen Chester, associate professor of anthropology at Brooklyn College of the City University of New York. "This study narrows the evolutionary debate surrounding mixodectids and gives us a clearer picture of their relationships," said Sargis, according to Phys.org. The research supports a close relationship between Mixodectes pungens, primates, and colugos, suggesting that mixodectids occupied a distinctive ecological niche among arboreal mammals of the time.
To determine where Mixodectes pungens fits on the evolutionary tree, the research team conducted two phylogenetic analyses. Both analyses confirmed that mixodectids belonged to the group of primatomorphs, a subgroup of Euarchonta that includes primates and colugos but excludes treeshrews. This implies that Mixodectes pungens represents a relatively close evolutionary cousin to humans.
The skeleton of Mixodectes pungens was collected in New Mexico's San Juan Basin by co-author Thomas Williamson, curator of paleontology at the New Mexico Museum of Natural History & Science, under a permit from the federal Bureau of Land Management. The discovery offers valuable information about how ancient mammals diversified to fill newly vacated ecological niches following the extinction of the dinosaurs.
Mixodectes pungens lived only a few million years after the dinosaurs went extinct, occupying a unique ecological niche in the early Paleocene. Its larger body size and leaf-heavy diet allowed it to thrive alongside early primate relatives in the same treetop environments. While Mixodectes pungens primarily ate leaves, another early primate, Torrejonia wilsoni, which was found in association with it, mostly consumed fruit. These distinctions in both size and diet suggest that mixodectids were differentiated from their tree-dwelling contemporaries.
The researchers compared the new Mixodectes pungens skeleton to those of other placental mammals, including plesiadapiforms, euprimates, treeshrews, and colugos. This comparison illuminated its place in the evolutionary tree and provided a clearer picture of the relationships between different species.
"This fossil skeleton provides new evidence concerning how placental mammals diversified ecologically following the extinction of the dinosaurs," said Chester.
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