Arsinoitherium, Uintatherium and Gobiatherium redux

Once again
huge-horned Arsinoitherium (Fig 1) is more closely related to hornless Gobiatherium in the large reptile tree (LRT, 2336 taxa) and both are related to horned uintatheres derived from hornless, but equally massive Coryphodon (Fig 1).

This interrelationship is based on maximum parsimony, each taxon playing its part in bringing these four similar yet disparate taxa together for the second time.

https://pterosaurheresies.wordpress.com/2025/02/06/vegavis-skull-2025-taxon-exclusion-and-genomics-adversely-affect-this-study/ ” data-image-caption=”

Figure 1. Arsinoitherium, Uintatherium, Gobiatherium and Coryphodon skulls compared.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/02/uintatherium-coryphodon-bathyopsis_skull-lat.jpg?w=105″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/02/uintatherium-coryphodon-bathyopsis_skull-lat.jpg?w=358″ class=”size-full wp-image-91556″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/02/uintatherium-coryphodon-bathyopsis_skull-lat.jpg” alt=”https://pterosaurheresies.wordpress.com/2025/02/06/vegavis-skull-2025-taxon-exclusion-and-genomics-adversely-affect-this-study/” width=”584″ height=”1669″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/02/uintatherium-coryphodon-bathyopsis_skull-lat.jpg?w=584&h=1669 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/02/uintatherium-coryphodon-bathyopsis_skull-lat.jpg?w=53&h=150 53w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/02/uintatherium-coryphodon-bathyopsis_skull-lat.jpg?w=105&h=300 105w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/02/uintatherium-coryphodon-bathyopsis_skull-lat.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 1. Arsinoitherium, Uintatherium, Gobiatherium and Coryphodon skulls compared. The basics are shared traits here. The differences are in the size of the horns, the size and distribution of the teeth, etc. No wonder this interrelationship has gone unnoticed elsewhere, but recovered in the LRT. The key take-away here is this: no other texted taxa are closer to these three than they are to each other.

That completely circumscribed naris,
rare in mammals, but found in Gobiatherium and Arsinoitherium turns out to be a homology, not a convergent character. Those similar horns on Arsinoitherium and Uintatherium likewise turn out to be a homology, not a convergent character. Getting them together on the same graphic (Fig 1) is instructive.

Traditionally Arsinoitherium zitteli
has been hard to classify. Wikipedia reports, “Arsinoitherium (Beadnell 1902; Eocene-Oligocene, 36-30mya; 3 m in length; Fig. 1) is related to elephants, sirenians, hyraxes and the extinct desmostylians.”

That’s a pretty broad gamut of taxa not recovered by the LRT.

Earlier the LRT nested Arsinoitherium with Gobiatherium when only 812 taxa were present and tested. Since then Arsinoitherium bounced out and around as more taxa were added. Today it comes back to its original nesting site.

Which came first?
Arsinoitheriidae – Andrews 1904
Dinocerata – Marsh 1872 (includes unrelated Prodinoceras)
Uintatheriidae – Flower 1876

That makes Arsinoitherium a member of the Uintatheriidae and the Dinocerata.

9 years later this remains a novel hypothesis of interrelationships.
If not, please provide a citation so I can promote it here.

References
Beadnell HGC 1902. A preliminary note on Arsinoitherium zitteli, Beadnell, from the Upper Eocene strata of Egypt. Public Works Ministry, National Printing Department. Cairo: 1–4.
Lucas SG 2001. Gobiatherium (Mammalia: Dinocerata) from the Middle Eocene of Asia: Taxonomy and biochronological Significance. Paläontologische Zeitschrift 74 (4): 591–600.
Osborn HF and Granger W 1932. Coryphodonts and uintatheres from the Mongolian expedition of 1930. American Museum Novitates 552:1-16.

wiki/Arsinoitherium
wiki/Gobiatherium
wiki/Arsinoitheriidae

Nesting twin-horned Arsinoitherium within the Condylarthra

Gobiatherium and Arsinoitherium updated with a Meniscotherium Bauplan