Itty-bitty cold-hardy Cretaceous marsupial lived above the Arctic Circle

February 27, 2019 8:09 AM

Though most people associate marsupials (Wikipedia) with kangaroos and koalas in Australasia, marsupials probably evolved in North America, expanded into South America and the Pacific rim of Asia (Natural History Collection of the University of Edinburgh). During this period of migration the North American marsupials became extinct, followed by extinctions in Europe during the Miocene epoch of the Tertiary period. Recently, fossils of a tiny Cretaceous marsupial were discovered above the Arctic Circle (Sci-News.com), the farthest north marsupial fossils have been discovered. "Northernmost record of the Metatheria: a new Late Cretaceous pediomyid from the North Slope of Alaska" (Journal of Systematic Palaeontology; abstract only)

Unnuakomys hutchisoni: Paleontologists Discover Northernmost Marsupial Known to Science (Paleontology World)

The ancient creature was about the size of a house mouse, probably munched on insects, and may have lived underground.

“Despite an estimated weight of less than an ounce, this itty-bitty animal was probably pretty hardy,” said Dr. Jaelyn Eberle, curator of fossil vertebrates at the University of Colorado Museum of Natural History.

“It would have needed to survive 120 days of darkness in the winter and temperatures that averaged just 42 degrees Fahrenheit (about 6 degrees Celsius).”

“These guys must have been adapted to darkness because they spent a lot of time in it.”

For more context and history of marsupials: 150 Million Years of Marsupial Evolution -- The Evolution of Marsupials, from Sinodelphys to the Giant Wombat (ThoughtCo.)

posted by filthy light thief (6 comments total)

Fascinating! I know which rabbit hole I’m going down to take a break!
posted by Katjusa Roquette at 8:29 AM on February 27, 2019 [1 favorite]

I know which rabbit hole I’m going down to take a break!

Psst . . . wombat hole. #marsupialsplaining
posted by The Bellman at 8:35 AM on February 27, 2019 [6 favorites]

Am I understanding correctly that an itty bitty anti-freezy skin-flap carries kids betweeny?
posted by cortex at 9:06 AM on February 27, 2019 [6 favorites]

cortex: unclear. The Paleontology World article called it an "opossum-like critter," but the more general ThoughtCo. article notes:

Because the mammals of the Mesozoic Era were so small--and because soft tissues don't preserve well in the fossil record--scientists can't directly examine the reproductive systems of animals from the Jurassic and Cretaceous periods. What they can do, though, is examine and compare these mammals' teeth, and by that criterion, the earliest identified marsupial was Sinodelphys, from early Cretaceous Asia. The giveaway is that prehistoric marsupials possessed four pairs of molars in each of their upper and lower jaws, while placental mammals had no more than three.

So until someone finds an early marsupial in amber, or maybe shale, we can only imagine about the presence or lack of itty-bitty anti-freezy pouchy.
posted by filthy light thief at 9:28 AM on February 27, 2019 [3 favorites]

Don't believes it. North 'Merica just jealous. Think you invent everything... 'are thought' and 'probably' not good enough.
posted by Thella at 12:15 PM on February 27, 2019 [1 favorite]

This is awesome—I work with two of the authors!
posted by leahwrenn at 8:06 PM on February 27, 2019 [1 favorite]