Paleontologists have made a remarkable discovery in Big Bend National Park in Texas, unearthing fossilized remains of a giant possum-like mammal that roamed the Earth approximately 60 million years ago. This significant find pertains to an ancient group of near-marsupials from the Paleocene period, known scientifically as Swaindelphys. The findings were detailed in a recent paper published in the Journal of Vertebrate Paleontology.
The prehistoric species identified as Swaindelphys solastella was considerably larger than its contemporaries within the Swaindelphys group. However, the size of this species is comparable to that of a modern hedgehog, according to the research team. Kristen Miller, a doctoral student at The University of Kansas' Biodiversity Institute and Natural History Museum, and lead author of the study, noted, “I compared them to a lot of other marsupials from around the same time period to see what they’re most closely related to.”
Initially, the paleontologists speculated that the fossils belonged to a group of metatherians—marsupial-like mammals—from the Cretaceous period. This group was believed to have survived the Cretaceous-Paleogene extinction, a mass extinction event that eradicated the dinosaurs around 66 million years ago. However, further analysis revealed that the specimens actually belonged to a surprisingly large new species of Swaindelphys, making this find even more significant.
Not only is Swaindelphys solastella the largest metatherian identified from this time period, but it is also the youngest specimen discovered at the most southern latitude. Chris Beard, senior curator with the Biodiversity Institute, remarked, “Since everything is bigger in Texas, this is perhaps not surprising.” He referred to these creatures as “primatomorphans,” indicating that while they are not technically primates, they are closely related to the ancestry of both living and fossil primates. Beard speculated that these marsupials might serve as ecological analogues to early primates.
The researchers aim to uncover more about the smaller and harder-to-find fossil mammals that once inhabited the region of Big Bend during the Paleocene. Beard emphasized the importance of studying the differences in fossil types found in northern regions, such as Wyoming and Alberta, Canada. “North of that ancient divide, we see the classic Bighorn Basin taxa in their expected time periods,” Miller explained. “But south of that, in river drainages that originate in the central Rockies and areas farther to the south, things start to go a little wacky.”
Future fieldwork in Big Bend is planned, with researchers eager to delve deeper into the history of Swaindelphys solastella and its ecological implications during the Paleocene epoch.
