66 million years ago, the mass extinction that wiped out the dinosaurs provided an opportunity for the expansion and evolution of mammals, which until then had occupied very restricted ecological niches. A new work published in the Journal of Systematic Palaeontology describes three new species of prehistoric mammals that would have lived in North America during the Paleocene and that suggest that this group would have diversified after the extinction of the dinosaurs much faster than what is known. thought.
The new species have been named Miniconus jeanninae, Conacodon hettingeri and Beornus honeyi . Although they differ in size, B. honeyi , the largest of them, would have been similar to a modern domestic cat, much larger than most mammals (the size of a rat) that had lived with dinosaurs in this area of the planet .
Archaic ungulates forerunners of hoofed mammals
The new group belongs to a group of placental mammals called archaic ungulates (or condyles), primitive ancestors of current hoofed mammals (horses, elephants, cows, hippos, etc.). Furthermore, the new species are distinguished from each other by their dental characteristics, and for example B. honeyi has been named after Beorn, the character from The Hobbit, because of its inflated molars.
The authors of the work, from the University of Colorado in Boulder, believe that these animals would have been omnivores, since their teeth allowed them to grind both meat and plants, although this fact does not rule out that they had been exclusively herbivores. The description of the species has been made from the anatomical and phylogenetic analysis of the teeth and bones of the lower jaw of 29 fossil species of archaic ungulates.
“Previous studies suggest that during the first hundreds of thousands of years after the extinction of the dinosaurs there was relatively low diversity of mammalian species in the western interior of North America, but the discovery of three new species in the Great Divide Basin – an endorheic basin located in the south of the state of Wyoming and that marks the dividing line of the waters that discharge into each ocean- suggests a rapid diversification after extinction ”, explains Madelaine Atteberry, lead author of the work. “These new archaic ungulates make up just a small percentage of the more than 420 mammalian fossils discovered at this site. We have not yet fully captured the extent of mammalian diversity in the earliest Paleocene and we predict that several more new species will be described. “
Seizing the opportunity
“When the dinosaurs became extinct, access to different foods and environments allowed mammals to rapidly flourish and diversify in the anatomy of their teeth and evolve to a larger body size. They clearly took advantage of this opportunity, as we can see in the radiation of new species of mammals that took place in a relatively short period of time after the mass extinction ”, reflects the expert.
Referencia: Atteberry and Eberle, 2021. New earliest Paleocene (Puercan) periptychid ‘condylarths’ from the Great Divide Basin, Wyoming, USA. Journal of Systematic Palaeontology ttps://doi.org/10.1080/14772019.2021.1924301
