Kayla Bazzana

Kayla's 1st First Authored Paper is obviously on Seymouria

Kayla D. Bazzana, Bryan M. Gee, Joseph J. Bevitt & Robert R. Reisz (2020) Neurocranial anatomy of Seymouria from Richards Spur, Oklahoma, Journal of Vertebrate Paleontology, DOI: 10.1080/02724634.2019.1694535

Seymouriamorphs are a globally distributed group of tetrapods (four-legged critters) that lived in the Permian period, and belong to a larger group we refer to as reptiliomorphs due to the fact that they look more like reptiles than earlier groups did. This is a fancy way of saying that they are an early offshoot of the lineage that led to modern amniotes (mammals and reptiles), but are not in fact true amniotes. Based on our current knowledge of early tetrapod relationships, seymouriamorphs are important for helping us understand how different groups of early tetrapods adapted to the challenges of life on land. Despite their importance, we still know relatively little about seymouriamorph anatomy or about how they lived; in particular, we know very little at all about their brains, sensory systems, or the structures that housed them.

 In this paper, we described two particularly well-preserved specimens of Seymouria, the genus the seymouriamorphs are named after (we palaeontologists are very creative with names). Thanks to the wonders of modern technology, we were able to stick them through a fancy neutron scanner to acquire extremely high-resolution digital scans of the entire skulls and everything inside them. By digitally separating each bone, we were able to describe the internal skull anatomy of Seymouria for the first time.

One of the really interesting things we found is a structure known as a “pressure relief window”; this is something that’s really important for land-dwelling animals, as it’s involved in accommodating the fluids housed inside the inner ear, and is important for allowing animals to hear sound on land. Prior to our discovery of this particular structure in Seymouria, it was only known in “true” amniotes; other Palaeozoic tetrapods achieve the same function by using existing openings, rather than evolving new ones. What this means for the ecology of Seymouria is still unclear, but it has opened the door for a whole new avenue of questions!

We also attempted to determine exactly which species of Seymouria these skulls belong to; unfortunately, we quickly discovered that the existing methods for differentiating the species rely on a lot of features that can change throughout an animal’s life. Our specimens showed some features associated with one species, and some features associated with another species; as a result, there was no way to tell which species these skulls represent, and suggests that we need to take a much closer look at how we’ve historically distinguished the different species of Seymouria.

February 10, 2020

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