Paleontologists have unveiled a remarkable discovery—a new species of multituberculous mammal from the genus Simolodon based on fossils found in Baja California, Mexico.
The newly identified mammal, Simolodon de Sosai, roamed the region that is now Mexico approximately 75 million years ago, during the Cretaceous period.
This ancient creature was about the size of a golden hamster, weighing around 100 grams.
It likely foraged on the ground and in trees, primarily consuming fruits and insects.
According to Professor Gregory Wilson Mantilla, a paleontologist at the University of Washington and curator of vertebrate paleontology at the Burke Museum, “Genus Simolodon was quite prevalent during the Late Cretaceous, the final chapter of the dinosaur era.”
Fossils of Simolodon have been uncovered across Western North America, stretching from western Canada to Mexico.
This new species, Simolodon de Sosai, represents an ancestor of those that survived the mass extinction event.
“Its relatively small size and omnivorous diet likely contributed to its survival advantages,” said Professor Mantilla.
Fossilized remains of Simolodon de Sosai, including parts of its skeleton such as teeth, skull, jaw, femur, and ulna, were discovered in the El Gallo Formation of Baja California in 2009.
This specimen is considered the most complete mammal known from the Mesozoic era in Mexico and one of the best-studied representatives of simolodontans, a significant group of multituberculates from North America.
“Fossil discoveries here are rare when compared to other regions,” explained Professor Wilson Mantilla.
The discovery of more than just teeth for Simolodon de Sosai enhances understanding of its anatomical features and locomotion.
This contributes to a broader comprehension of the genus and its ecological niche, providing insights into the multituberculate lineage.
Research indicates that the local mammalian fauna of El Gallo is currently represented by 16 specimens, including three multituberculates, one metatherian, and one eutherian.
“While additional sampling is necessary, the existing mammalian fauna appears to exhibit the highest biogeographic similarity to the native fauna of Terlingua in West Texas,” the researchers noted.
The findings were published in a recent paper in the Journal of Vertebrate Paleontology.
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Gregory P. Wilson Mantilla et al. New skull and postcranial remains of Simolodon (Mammalia, Polytuberculata, Cymolodontidae) from the Upper Cretaceous (Campanian) El Gallo Formation of Baja California, Mexico. Journal of Vertebrate Paleontology, published online on April 22, 2026. doi: 10.1080/02724634.2026.2641109
Source: www.sci.news
