A Tiny New Mammal from the Age of Dinosaurs
A research team led by the University of Washington has identified a new species of ancient mammal from a fossil discovered in Baja California. The specimen, estimated to be 75 million years old, provides new insight into the creatures that lived alongside the dinosaurs.
A Hamster-Sized Survivor
The new species, named Cimolodon desosai, was roughly the size of a golden hamster. It likely spent its time both on the ground and in trees, feeding on fruits and insects. This small, agile mammal belonged to the genus Cimolodon, a group that was common during the Late Cretaceous period.
Key Fossil Evidence
The fossil remains include teeth, a skull, jaws, a femur, and an ulna. To analyze the specimen, researchers employed advanced digital imaging and micro-computed tomography to capture high-resolution images. By carefully comparing the teeth of C. desosai to those of related species, the team was able to confirm it as a distinct, new species.
A Namesake Lost
The species name honors Michael de Sosa VI, the field assistant who first discovered the fossil. Tragically, de Sosa passed away during the analysis of the specimen.
Evolutionary Significance
Fossils of the Cimolodon genus have been found throughout western North America. This new species is particularly significant because it is ancestral to mammals that ultimately survived the catastrophic Cretaceous-Paleogene extinction event—the same event that wiped out the non-avian dinosaurs.
Publication and Funding
The findings were published April 22 in the Journal of Vertebrate Paleontology.
The research was supported by UC MEXUS-CONACYT, Dirección General de Asuntos del Personal Académico PAPIITIN 111209-2, the UW College of Arts and Sciences, the UW Department of Biology, and the American Philosophical Society.