A new large Late Cretaceous lamniform shark from North America, with comments on the taxonomy, paleoecology, and evolution of the genus Cretodus
by: Kenshu Shimada, Micheal J. Everhart
Summarized by: Baron Hoffmeister
What data were used? : This study examined a partial skeleton of the Late Cretaceous shark, Cretodus, collected from the Blue Hill Shale in north-central Kansas, U.S.A. It had unique teeth not present in any other species of Cretodus.
Methods: This study used a taxonomic analysis of the fossilized remains found and compared them to other members of the Cretodus genus.
Results: The study found that the species of the fossilized partial shark skeleton found does not share enough similar features with any of the other four known species within the genus Cretodus. Therefore it has been listed as a new species, C. houghtonorum. Researchers found that it had a unique tooth size and pattern that didn’t match any previously discovered species (figure 1). Its calcified cartilage scales along with the inference that this shark had a large girth due to its bone structure that was preserved, indicated that this organism was likely a sluggish shark that lived in a nearshore environment. This study examined growth bands in its vertebral column and found that this shark had a lifespan of around 51 years.
Why is this study important? Aside from discovering a new species, this study recognizes the fact that the evolutionary relationships of several shark families is still relatively unknown. However, this new finding provides data linking it with other members at the genus level. Without understanding these relationships, it’s difficult to understand the distribution of these organisms, how they changed over time, and why they went extinct.
The big picture: Overall, this study is useful in determining possible links between extant and extinct shark species. This study provides data that can rework our understanding of evolutionary traits between extinct and modern-day sharks as well. The skeletal and dental data found in this study can be useful for other studies incorporating evolutionary trends, prehistoric ecology, and the taxonomic differences within the genus Cretodus.
Citation: Shimada, K., & Everhart, M. J. (2019). A new large Late Cretaceous lamniform shark from North America, with comments on the taxonomy, paleoecology, and evolution of the genus Cretodus. Journal of Vertebrate Paleontology, 39(4). doi: 10.1080/02724634.2019.1673399