Cotylorhynchus romeri

Overview

Cotylorhynchus romeri is a synapsid known for its large body and very small head. Its short, robust jaws have been studied at the species level. The striking contrast between its head and trunk offers a starting point for examining the arrangement within its jaws.^[1][2]

Key facts

Researchers interpreted its skull and jaw structure as evidence of feeding on fibrous terrestrial plants. Its small head is an important clue for exploring questions about its way of life.^[1]

Time and place

Early Permian material from the Hennessey Formation in present-day Oklahoma has been studied. The Permian as a whole spans roughly 300–250 million years ago. Comparing the structure of its small head with its large body provides a basis for understanding this animal.^[1][4]

The time range describes source context, not the complete duration of this species.

Size, form and skeleton

The species-level cranial description describes a small skull and short, robust jaws. Museum material at the genus level presents the contrast between its large body and small head. Phylogenetic comparisons have also discussed the condition of the five digit rays in the hind foot.^[1][2][3]

Cotylorhynchus romeri is estimated to have reached about 4.5 m in body length. A 2022 skull study cited this figure from an earlier skeletal study, describing it as a large herbivore of the Early Permian.^[11]

Habitat and reproduction

What food might an animal with such a large body have handled with its small head? A 2022 cranial anatomical study interpreted it as feeding on fibrous terrestrial plants. This research connects jaw shape with the function of processing food.^[1]

Fossil discovery

A 2015 study of caseid phylogeny compared the condition of the feet in Cotylorhynchus. In 2022, the cranial anatomy of romeri was examined in detail. Different questions about form arise from the ends of the limbs and the small head.^[3][1]

References

1. Reisz·Scott·Modesto (2022) — Head anatomy of Cotylorhynchus romeri
2. Sam Noble Museum — Permian organisms
3. Romano·Nicosia (2015) — Phylogenetic comparison of caseids
4. International Commission on Stratigraphy (2024) — Geological time chart
5. Modesto (2010) — Postcranial bones of Mesosaurus tenuidens
6. National Museum of Natural History, Paris — Mesosaurus type specimen
7. International Commission on Stratigraphy (2024) — Geological time chart
8. Reisz·Scott·Modesto (2022) — Head anatomy of Cotylorhynchus romeri
9. Sam Noble Museum — Permian organisms
10. International Commission on Stratigraphy (2024) — Geological time chart
11. Reisz et al. (2022) — Skull anatomy of Cotylorhynchus romeri

Research questions

How can the feet of closely related species be compared? The study explains that the hind-foot condition described in other Cotylorhynchus species also occurs in romeri. This research seeks shared structures in material from several species of the same genus.^[3]

Observation

Move your gaze from the large body to the very small head and its short, robust jaws. Then picture the several digit rays in the hind feet to examine the different arrangements of the head and the ends of the limbs together.^[1][2][3]