Anthracobune and Cambaytherium (= Anthracobunidae) have new relatives in the LRT

Again, hindsight reveals the obvious.
Even so, this blogpost apparently ‘reveals the obvious’ for the first time in the literature.

A little backstory
According to Wikipedia – Anthracobune, “Anthracobune is an extinct genus of stem perissodactyl from the middle Eocene of the Upper Kuldana Formation of Kohat, Punjab, Pakistan. The size of a small tapir, it lived in a marshy environment and fed on soft aquatic plants. It is the largest known anthracobunid. This group was formerly classified with proboscideans (according to Gingerich et al. 1990).“

According to Wikipedia – Cambaytherium, “Cambaytherium is an extinct genus of placental mammals in the family Cambaytheriidae whose fossils were found in an open pit coal mine located in Gujarat, India. The fossils were dated to the Early Eocene, 54.5 million years ago. The teeth and the number of sacral vertebrae, are intermediate between Perissodactyla and earlier mammals and may be indicative of what the common ancestor of all of Perissodactyla looked like. The animal was capable of running, but would not have been as fast as early perissodactyls. The fore-feet had at least four toes, and the hind-feet had five, one of which was vestigial, whereas even the earliest perissodactyls known had no more than four toes on each foot.”

Figure 1. Anthracobune, Cambaytherium and relatives in the LRT. These include Periphgragnis, Rostriamynodon and Agriochoerus antiquus. ” data-image-caption=”

Figure 1. Anthracobune, Cambaytherium and relatives in the LRT. These include Periphgragnis, Rostriamynodon and Agriochoerus antiquus.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/09/rostriamynodon-cambaytherium588.jpg?w=70″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/09/rostriamynodon-cambaytherium588.jpg?w=239″ class=”size-full wp-image-88903″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/09/rostriamynodon-cambaytherium588.jpg” alt=”Figure 1. Anthracobune, Cambaytherium and relatives in the LRT. These include Periphgragnis, Rostriamynodon and Agriochoerus antiquus.” width=”584″ height=”2503″ />

Figure 1. Anthracobune, Cambaytherium and relatives in the LRT. These include Periphgragnis, Rostriamynodon and Agriochoerus antiquus.

Currently in the LRT
Anthraocbune (Fig 1) nests with Cambaytherium between Periphragnis (basal to the Notoungulata) and Rostriamynodon + Agriochoerus antiquus (basal to hippos, desmostylians and mystictes). In the LRT anthracobunids are also basal to gracile Artiodactylia with pigs at its base. Perissodactylia (including rock hyraxes) evolved from this clade.

So in a way Anthracobune was “an extinct genus of stem perissodactyl.”

Rostriamynodon grangeri
(Wall and Manning 1986; AMNH 107635; Eocene) was originally considered amynodontid rhino. In the LRT it nests with oreodonts like Agriochoerus antiquus and also with Cambaytherium + Anthracobune. Note the shape of the nasals and the anterior extension of the frontals along with the wide molars and the molarized premolars.

Cambaytherium thewissi 
(Rose et al. 2014; Eocene, 55 mya; 45-75 lbs) was originally considered a basal perissodactyl, but nests here between Periphragnis and Rostriamynodon. The anterior palate has the same three lobes found in Hippopotamus. The posterior mandible has a long retroarticular process as in Anthracobune. Cambaytherium was found on the marine coastline of island India, close to where pakicetid aand archaeocete whales were convergently evolving from terrestrial tenrec ancestors.

Anthracobune pinfoldi
(Pilgrim 1940; Kumar 1991, middle Eocene, size of a small tapir) The anthracobunids were originally considered proboscideans, like Elephas. Cooper et al. 2014 nested them with perissodactyls, like Ancodus. Here anthracobunids nest basal to Hippopotamus and the desmostylian Paleoparadoxia.

Anthracobunids
have small and simple upper and lower incisors and relatively small canines. The naris opens dorsally signaling a greater aquatic niche. The retroarticular process is the largest among all mammals. The mandible is longer than the rostrum.

Let us all know
if this hypothesis of interrelationships is incorrect or was published earlier. Adding taxa and correcting earlier scoring errors in unrelated taxa brought these taxa (Fig 1) together in the LRT.

References
Cooper LN, Seiffert ER, Clementz M, Madar SI, Bajpai S, Hussain ST, Thewissen JGM 2014. Anthracobunids from the Middle Eocene of India and Pakistan Are Stem Perissodactyls. PLoS ONE. 9 (10): e109232. doi:10.1371/journal.pone.0109232. PMID 25295875.
Gingerich PD, Russell DA and Wells NA 1990. Astragalus of Anthracobune (Mammalia,
Proboscidea) from the Early-MiddleEocene of Kashmir. Contr. Paleontol. Univ. Michigan 28: 71-77.
Kumar K 1991. Anthracobune aijiensis nov. sp. (Mammalia: Proboscidea) from the Subathu Formation, Eocene from NW Himalaya, India”. Geobios. 24 (2): 221–39. doi:10.1016/s0016-6995(91)80010-w. OCLC 4656806310.
Leidy J 1850. [Abstract of remarks made before a meeting of the Academy of Natural Sciences of Philadelphia, December 17th, 1850]. Proceedings of the Academy of Natural Sciences of Philadelphia 5(1):121-122.
Pilgrim GE 1940. Middle Eocene mammals from north-west Pakistan. Proceedings of the Zoological Society. B. London. 110: 127–152.
Rose, KD et al. (8 other authors) 2014. Early Eocene fossils suggest that the mammalian order Perissodactyla originated in India. Nature Communications. 5 (5570). doi:10.1038/ncomms6570.
Rose KD et al, 2020. Anatomy, Relationships, and Paleobiology of Cambaytherium (Mammalia, Perissodactylamorpha, Anthracobunia) from the lower Eocene of western India, Journal of Vertebrate Paleontology (2020). DOI: 10.1080/02724634.2020.1761370
Rose, KD et al. (8 other authors) 2014. Early Eocene fossils suggest that the mammalian order Perissodactyla originated in India. Nature Communications. 5 (5570). doi:10.1038/ncomms6570.
Rose KD et al, 2020. Anatomy, Relationships, and Paleobiology of Cambaytherium (Mammalia, Perissodactylamorpha, Anthracobunia) from the lower Eocene of western India, Journal of Vertebrate Paleontology (2020). DOI: 10.1080/02724634.2020.1761370
Wall WP and Manning E 1986. Rostriamynodon grangeri n. gen., n. sp. of amynodontid (Perissodactyla, Rhinocerotoidea) with comments on the phylogenetic history of Eocene Amynodontidae. Journal of Paleontology 60(4):911–919.

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