Metacheiromys, now a pangolin ancestor in the LRT

Pangolins
(Figs 1, 2, genus Manis) have a Cenozoic heritage, slightly expanded today in the constantly updated large reptile tree (LRT, 2324 taxa) with the addition of Metacheiromys (Fig 3). I was remiss in not mentioning the addition of Patriomanis, ‘the father of pangolins’ when it entered the LRT years ago.

That omission is rectified today.

Patriomanis americana
(Emry 1970; Gaudin, Emery and Morris 2016, Late Eocene, Wyoming) is only slightly different from the extant pangolin, Manis. This taxon is based on several specimens.

Manis pentadactyla
(Gray 1821) is the extant, scaly anteater, a member of the order Pholidota. That order has been traditionally difficult to nest. Often it has been nested with aardvarks, like Orycterpus. Here Manis nests with Metacheiromys (below) and Chriacus. These taxa nest with Paleocene tree shrews that ventured to the ground following the dinosaur extinction event. Uniquely, keratinized scales cover the body. Those are modified hairs.

Metacheiromys tatusia
(aka M. marshi Wortman 1903, Osborn 1904, Simpson 1931, AMNH 11718, 25cm presacral lengh; YPM 12903 holotype is chimaera, part primate; Middle Eocene; ) was originally considered a primate, then an edentate and then as a palaenodont. Here it nests with pangolins, like Manis and Patriomanis Few to no teeth line the jaws, except for the upper and lower canines, which were retained. The sacrum appears odd in that only the posterior sacral ribs attached to the ilia. Manual digts 1 and 5 might be absent. Pedal digit 5 is absent.

Alocodontullum atopum
(Rose, Bown and Simons 1978; Rose, Emery and Gingerich 1992; early Eocene, 45 cm in length; UM 93740) is a close relative of Metacheiromys differing chiefly in relative metatarsal and toe lengths and having flat-cusped teeth poterior to the fang-like canines. Claws and forelimbs appear ready to dig. Hands and feet are relatively larger. Mandible is relatively smaller.

Rose, Emery and Gingerich 1992 nest Alocondontulum in a clade named Epoicotheriidae, but Epoicotherium and Xenocranium nest in another clade, that of fairy armadillos in the LRT.

Earlier
the LRT nested pangolins with aardvarks (Orycteropus), despite several obvious shared traits (Fig 2).

That is the nature of study, restudy and revision, all through a human filter.

Genomics
According to Wikipedia – Pangolin, “The order Pholidota was long considered to be the sister taxon to Xenarthra (neotropical anteaters, sloths, and armadillos), but recent genetic evidence indicates their closest living relatives are the carnivorans, with which they form a clade, the Ferae.”

This is untenable. One more nail in the coffin of deep time genomics.

Gaudin et al 2009 used fossils and trait analysis.
They erected, “Pholidotamorpha. Definition: Node-based, the least inclusive clade including the common ancestor of Metacheiromys dasypus and Manis pentadactyla and its descendents.”

The LRT confirms this hypothesis of interrelationships.

Now the bigger question that only the LRT has resolved (for now)…
Where did Metacheiromys evolve from? Presently Metacheiromys has an ancestor in middle Eocene Paroodectes with roots in the Late Jurassic, based on phylogenetic bracketing and the splitting of Madagascar from its former neighbors. Related taxa with more teeth include Vulpavus, Siamotherium, Anagale, Notharctus and Barylambda. each basal to their own placental 1 clade.

Orycteropus, the aardvark, remains a sister taxon at the base of the anteater/armadillo clade, no longer related to glyptodons + fairy armadillos, despite many convergent traits.

Sorry for earlier errors. Sometimes the obvious escapes me.

References
Emry RJ 1970. A North American Oligocene Pangolin and Other Additions to the
Pholidota. Bulletin of the American Museum of Natural History, 142:459–510.
Gaudin et al. 2009. The phylogeny of living and extinct pangolins (Mammalia, Pholidota) and associated taxa: a morphology based analysis. Journal of Mammalian Evolution 16:235-305.
Gaudin TJ, Emery RJ and Morris J 2016. Skeletal Anatomy of the North American Pangolin Patriomanis americana (Mammalia, Pholidota) from the Latest Eocene of Wyoming (USA). Smithsonian Institution Scholarly Press.
Rose KD, et al. 2005. Xenarthra and Pholidota. In The Rise of Placental Mammals. Rose KD, Archibald JD. Baltimore: Johns Hopkins University Press.

wiki/Manis
wiki/Patriomanus
wiki/Pangolin = Pholidota
wiki/Metacheiromys

Source: https://pterosaurheresies.wordpress.com/2024/08/23/metacheiromys-now-a-pangolin-ancestor-in-the-lrt/