Pleuraspidotherium: now a tillodont = plesiadapiform in the LRT
Known and scored from an incomplete skull
and more complete mandible, Pleuraspidotherium (Figs 1, 2) was a traditional Paleocene condylarth of otherwise uncertain affinity found in Spain and France. Note the rodent-like (and camel-like!) diastema (= toothless jaw margin) and molar-like fourth premolar (cyan).
Pleuraspidotherium has bounced around the LRT for years based on 1) it’s incomplete data, 2) that diastema and 3) that very canine-like premolar.
Figure 1. Pleuraspidotherium newly interpreted with a large canine-like premolar.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/pleuraspidotherium_skull588.jpg?w=213″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/pleuraspidotherium_skull588.jpg?w=584″ class=”size-full wp-image-92945″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/pleuraspidotherium_skull588.jpg” alt=”Figure 1. Pleuraspidotherium newly interpreted with a large canine-like premolar.” width=”584″ height=”822″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/pleuraspidotherium_skull588.jpg?w=584&h=822 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/pleuraspidotherium_skull588.jpg?w=107&h=150 107w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/pleuraspidotherium_skull588.jpg?w=213&h=300 213w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/pleuraspidotherium_skull588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 1. Pleuraspidotherium newly interpreted with a large canine-like premolar. Here the traditional canine is reidentified as a premolar 1, as in related taxa.
Now joining the now larger clade of taxa
with a canine replaced by a canine-like first premolar, Pleuraspidotherium (Figs 1, 2) will hopefully rest there from now on and not cause further trouble. Trogosus (Fig 2) is a large tillodont = plesidapiform related to Pleuraspidotherium. An ancestor close to Labidotherium is Siamotherium in the large reptile tree (LRT, 2338 taxa).
Figure 2. Trogosus, the tillodont, and its smaller relatives in the LRT, Siamotherium and Pleuraspidotherium.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/trogosus_skulls588-1.jpg?w=182″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/trogosus_skulls588-1.jpg?w=584″ class=”size-full wp-image-92950″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/trogosus_skulls588-1.jpg” alt=”Figure 2. Trogosus, the tillodont, and its smaller relatives in the LRT, Siamotherium and Pleuraspidotherium. ” width=”584″ height=”963″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/trogosus_skulls588-1.jpg?w=584&h=963 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/trogosus_skulls588-1.jpg?w=91&h=150 91w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/trogosus_skulls588-1.jpg?w=182&h=300 182w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/trogosus_skulls588-1.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 2. Trogosus, the tillodont, and its smaller relatives in the LRT, Siamotherium and Pleuraspidotherium.
Siamotherium pondaungensis
(Suteethorn et al. 1988; Soe et al. 2017; Eocene, Fig 2) was originally considered a small anthracothere close to Anthrcotherium, but here nests with Pleuraspidotherium and Trogosus among the tillodonts = plesiadapiformes. It also has a newly identified canine-like premolar. That’s an overlooked secret the LRT has revealed.
Convergent traits in unrelated mammals cause many headaches like these two hard-to-nest taxa where the ‘obvious’ canine turned out to be a premolar. That’s why mammal workers have turned to a belief in genomics.
Figure 3. Tillodon is the largest tillodont. Here it is shown to scale with Trogosus, Plesiadapis and other related taxa.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/tillodonta588.jpg?w=140″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/tillodonta588.jpg?w=479″ class=”size-full wp-image-92953″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/tillodonta588.jpg” alt=”Figure 3. Tillodon is the largest tillodont. Here it is shown to scale with Trogosus, Plesiadapis and other related taxa.” width=”584″ height=”1247″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/tillodonta588.jpg?w=584&h=1247 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/tillodonta588.jpg?w=70&h=150 70w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/tillodonta588.jpg?w=140&h=300 140w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/05/tillodonta588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 3. Tillodon is the largest tillodont. Here it is shown to scale with Trogosus, Plesiadapis and other related taxa close to the ancestry of multituberculates and rodents.
This appears to be a novel hypothesis of interrelationships.
If not, please provide a citation so I can promote it here.
Editors note:
If you want to replicate the LRT in order to confirm, refute or modify it, I suggest you do what I did (by accident) and save the mammal clade for last. And maybe devote your retirement years to this pursuit. Don’t think of mammals as a headache, which they are, but as a learning experience, like a safe-cracker slowly learning what the combination is.
No wonder workers have opted for a less frustrating method = genomics.
Unfortunately genomics too often delivers false positives AND omits fossil taxa.
References
Lemoine V 1885. Le Pleuraspidotherium. La Nature 13(I): 47.
Lemoine V 1885. Etude sur quelques mammiferes de petite taile de la faune cernaysienne des environs d Reims. Bulletin de la Societed geologique de France 13:203-217.
Soe AN et al. (6 co-authors) 2017. New remains of Siamotherium pondaungensis (Cetartiodactyla, Hippopotamoidea) from the Eocene of Pondaung, Myanmar: Paleoecologic and phylogenetic implications. Journal of Vertebrate Paleontology 37(1):e1270290https://doi.org/10.1080/02724634.2017.1270290
Suteethorn V, Buffetaut E Helmcke-Ingava Rt JaegerJ-J and Jongkanjanasoontorn Y 1988. Oldest known Tertiary mammals from South-East Asia: Middle Eocene primate and anthracotheres from Thailand. Neues Jahrbuch f€ur Geologie und Palaontologie, Monatshefte 9:563–570.
wiki/Pleuraspidotherium
wiki/Siamotherium– not posted yet
Source: https://pterosaurheresies.wordpress.com/2025/05/25/pleuraspidotherium-now-a-tillodont-plesiadapiform-in-the-lrt/
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