Re: Late Cretaceous Metatherian

On 10/24/24 7:49 PM, John Harshman wrote:

On 10/24/24 8:31 AM, erik simpson wrote:

A good-sized (muskrat) Cretaceous mammal fossil has been found in Colorado.  It lived in a swampy environment, probably not inhabited by dinosaurs. The fossil consists of a jaw with some teeth.
>
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0310948
>
Abstract
>
Heleocola piceanus, a new, relatively large metatherian from Upper Cretaceous (‘Edmontonian’) strata of the Williams Fork Formation in northwestern Colorado is described, based on a recently discovered jaw fragment (MWC 9744), in addition to three isolated teeth initially referred by other studies to Aquiladelphis incus and Glasbius piceanus. Although sharing several morphologic characters with the Lancian genus Glasbius, H. piceanus lower molars are considerably larger than those of Glasbius and differ from the latter in lacking a buccal cingulid, possessing carnassiform notches on the cristid obliqua and entocristid, and bearing an entoconulid on m3. To examine the relationship of Heleocola piceanus to other metatherians, H. piceanus was scored into a previously existing taxon-character matrix. Our phylogenetic analysis recovers H. piceanus as the sister taxon to Glasbius, which is consistent with our morphologic comparisons. H. piceanus represents the oldest member of the Glasbiidae. A regression equation for predicting body mass of dentally conservative metatherians that utilizes the length of m1 estimates the mass of H. piceanus at 855–1170 g, which is comparable in mass to today’s muskrat (Ondatra zibethicus) and large relative to other Late Cretaceous pediomyoids. Based upon its molar morphology, specifically the low inflated cusps, low height differential between the trigonid and talonid, and near-bunodont morphology, H. piceanus is interpreted as an omnivore with a plant-dominated diet.

 Of course I turn immediately to the phylogenetic analysis. Do you have any idea why there were no crown-group taxa in the data set?

I hadn't conisidered that.  I imagine it's because of the limited characters in fossil they've got.  Still, at least one crown taxon would have been a good idea.