Lophiodon revisited: now a marsupial close to Paedotherium

According to Wikipedia – Lophiodon,
“Lophiodon is an extinct genus of mammal related to chalicotheres. It lived in Eocene Europe 52 to 38 million years ago,^[3] and was previously thought to be closely related to Hyrachyus. Lophiodon was named and described by Cuvier (1822) based on specimens from the Sables du Castrais Formation“ – [France].

This taxon goes back to Cuvier 1822.

Figure 1. Lophiodon compares a little better with Paedotherium, within the Marsupialia. Formerly it nested with Macrauchenia and kin. ” data-image-caption=”

Figure 1. Lophiodon compares a little better with Paedotherium, within the Marsupialia. Formerly it nested with Macrauchenia and kin.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/lophiodon_recon588.jpg?w=185″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/lophiodon_recon588.jpg?w=584″ class=”size-full wp-image-86139″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/lophiodon_recon588.jpg” alt=”Figure 1. Lophiodon compares a little better with Paedotherium, within the Marsupialia. Formerly it nested with Macrauchenia and kin.” width=”584″ height=”945″ />

Figure 1. Lophiodon compares a little better with Paedotherium, within the Marsupialia. Formerly it nested with Macrauchenia and kin. All claws are also missing in this specimen as in Paedotherium. Strange.

According to Verault et al 2020,
“Despite their preponderance in the European fossil record, their exact origin and relationships within the perissodactyls remains unknown…”

According to Wikipedia = Lophiodontidae
“Previously thought to be related to tapirs, it is now thought that they were most likely related to early chalicotheres, although they are distinct from that group.”

With convergence possible, the tested taxon was expanded.

Figure 2. Paedotherium, an ungulate-like marsupial. ” data-image-caption=”

Figure 2. Paedotherium, an ungulate-like marsupial.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/paedotherium-recon588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/paedotherium-recon588.jpg?w=584″ class=”size-full wp-image-86140″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/paedotherium-recon588.jpg” alt=”Figure 2. Paedotherium, an ungulate-like marsupial.” width=”584″ height=”389″ />

Figure 2. Paedotherium, an ungulate-like marsupial. Digit tips are all missing.

Until yesterday,
Lophiodon (Fig 1) also nested with chalicotheres in the LRT.

After review
Lophiodon now nests with more similar Paedotherium (Fig 2) and Interatherium (Fig 3) within the Marsupialia in the large reptile tree (LRT, 2319 taxa).

The closest living relatives of interatheres are kangaroos.

Figure 3. Interatherium is another close relative to Paedotherium and Lophiodon. ” data-image-caption=”

Figure 3. Interatherium is another close relative to Paedotherium and Lophiodon.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/interatherium588.jpg?w=104″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/interatherium588.jpg?w=354″ class=”size-full wp-image-86142″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/interatherium588.jpg” alt=”Figure 3. Interatherium is another close relative to Paedotherium and Lophiodon.” width=”584″ height=”1690″ />

Figure 3. Interatherium is another close relative to Paedotherium and Lophiodon.

Along with Lophiodon,
Eolophiodon and Litolophus also made the shift to the Marsupialia. Others may follow. This clade also produced the herbivorous behemoth, Toxodon (Fig 4), which was hunted by early humans with stone spear tips.

Figure 4. A bison-like marsupial, Toxodon. ” data-image-caption=”

Figure 4. A bison-like marsupial, Toxodon.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/toxodon_588.jpg?w=276″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/toxodon_588.jpg?w=584″ class=”size-full wp-image-86155″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/toxodon_588.jpg” alt=”Figure 4. A bison-like marsupial, Toxodon. ” width=”584″ height=”635″ />

Figure 4. A bison-like marsupial, Toxodon. Note the labeling of the pedal digits. Now these may be 3-4-5.

During the course of study here,
The tarsal axis in Interatherium (Fig 3) was shifted laterally from 2-3to 3-4, which is not only more central but opens the door to reidentifying the pedal digits on Lophiodon to 3-4-5. A descending flange of the jugal below the orbit is a shared trait. In Lophiodon this jugal flange (cyan) appears to have broken off but preserved and replaced here (Fig 1). Toxodon (Fig 4) also retains this jugal flange.

Strangely, all claws are missing (or remain unidentified) from the fossil remains of Paedotherium (Fig 3) and Lophiodon (Fig 1). Coincidence? Or trait?

This appears to be a novel hypothesis of interrelationships.
If not, please provide a citation so I can promote it here. You can tell by the previous nesting error that I endeavor to nest taxa traditionally, but am able to test alternative hypotheses as they arise.

References
Bai B, Wang Y-Q and Meng J 2010. New craniodental materials of Litolophus gobiensis (Perissodactyla, “Eomoropidae”) from Inner Mongolia, China, and phylogenetic analyses of Eocene chalicotheres. American Museum Novitates 3688: 27pp.
Bai B, Wang Y-Q and Meng J 2010. Early Eocene chalicothere Litolophus with hoof-like unguals. Journal of Vertebrate Paleontology 31(6):1387-1391.
Cuvier G 1822. Recherches sur les Ossemens Fossiles (Nouvelle Edition)2(1): Chez G. Dufour et E. D’Ocagne, Paris, France.
Holbrook LT 2009. Osteology of Lophiodon Cuvier, 1822 (Mammalia Perissodactyla) and its phylogenetic implications. Journal of Vertebrate Paleontology 29(1):212–230.
Radinsky LB 1964b. Notes on Eocene and Oligocene fossil localities in Inner Mongolia.
American Museum Novitates 2180: 1–11.
Robinet et al. 2015. A new genus of Lophiodontidae (Perissodactyla, Mammalia) from the early Eocene of La Borie (Southern France) and the origin of the genus Lophiodon Cuvier, 1822. Geobios 48 (2015) 25–38.
Verault Q et al (more than 9 co-authors) 2020. New remains of Lophiaspis maurettei (Mammalia, Perissodactyla) from the Early Eocene of France and the implications for the origin of the Lophiodontidae. Journal of Vertebrate Paleontology 40 (6): e1878200.

wiki/Lophiodon
wiki/Lophiodontidae
wiki/Litolophus
wiki/Eolophiodon – not yet posted