Permian Synapsid Had Hippopotamus-Like Semi-Aquatic Lifestyle


A new genus and species of caseid synapsid that lived 264 million years ago (Permian period) has been identified from a partial but well-preserved postcranial skeleton found in France.

Life restoration of Lalieudorhynchus gandi and an associated aquatic tupilakosaurid temnospondyl (bottom left); estimated water depth about 2 m, algae are possible. Image credit: Frederik Spindler.

Life restoration of Lalieudorhynchus gandi and an associated aquatic tupilakosaurid temnospondyl (bottom left); estimated water depth about 2 m, algae are possible. Image credit: Frederik Spindler.

Lalieudorhynchus gandi lived in what is now France during the Guadalupian epoch of the Permian period, some 264 million years ago.

The ancient animal belonged to Caseidae, a group of primitive synapsids (mammals and their close relatives) that existed from the Carboniferous to the Permian period.

“The Caseidae were among the first large herbivorous amniotes that have evolved on the supercontinent Pangea,” Dr. Ralf Werneburg from the Museum of Natural History in the Castle Bertholdsburg Schleusingen and his colleagues wrote in their paper.

“These early synapsids are known from the Pennsylvanian of the United States, then in the Permian of the paleo-equatorial belt, from the United States to Siberia.”

“While the first caseids were small to moderate in size, later forms acquired a very peculiar body shape, with enormous, barrel-shaped trunks, comparatively tiny triangular skulls with large nares and leaf-like teeth, and massive limbs ending in short digits and powerful unguals.”

“Recently, numerous discoveries and redescriptions allowed a better understanding of their paleobiodiversity and paleobiology, but their precise phylogenetic relationships remain discussed.”

The partial skeleton of Lalieudorhynchus gandi was unearthed at the La Lieude Formation, approximately 15 km south of Lodève in Occitanie, France.

Despite its large size, the specimen shows an interesting mix of immature and mature features.

“A mix of both juvenile and adult features was already observed on other large caseid specimens,” the paleontologists wrote.

“Juveniles grew rapidly and adults much more slowly. Delaying skeletal maturity would have enabled caseids to attain very large sizes by having an extended period of growth.”

“The coexistence of immature and mature features may have been the result of a compromise between evolutionary constraints in the largest caseids, such as the necessity to grow sustainably and to support a heavy weight.”

The team’s analysis suggests that Lalieudorhynchus gandi had a semi-aquatic lifestyle.

“Our anatomical and histological observations suggest that this caseid may have spent time underwater,” the researchers explained.

“Yet our sedimentological analysis, together with the associated flora, suggests it may have browsed outside water.”

“The mixture of mature and immature ontogenetical characters is consistent with a possible semi-aquatic lifestyle.”

The authors also assessed the phylogenetic position of Lalieudorhynchus gandi within its group.

“Interestingly, Lalieudorhynchus gandi is closer to the North American caseid Cotylorhynchus hancocki than to the other French caseids Ruthenosaurus and Euromycter from the geographically closer Rodez Basin,” they wrote.

“These two last caseids document the Artinskian radiation of the clade, which remained diverse until Olson’s extinction.”

“Caseids survived, as Lalieudorhynchus gandi is one of the youngest representatives of the clade, and may have used novel ecological strategies to access their vegetarian food sources.”

The team’s paper was published in the journal Palaeovertebrata.

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R. Werneburg et al. 2022. A New caseid Synapsid from the Permian (Guadalupian) of the Lodève basin (Occitanie, France). Palaeovertebrata 45 (2)-e2; doi: 10.18563/pv.45.2.e2




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