2018/07/23 by Robert F. Stewart, Jordan C. Mallon · 2 citations
Earth and Planetary Sciences · Environmental Science · #Paleontology and Evolutionary Biology #Evolution and Paleontology Studies #Amphibian and Reptile Biology #Allometry #Rostrum #Biology #Skull #Ontogeny #Squamata #Morphometrics #Zoology #Anatomy #Ecology
paper · pdf · doi:10.18435/vamp29339
openalex publication_date 2018/07/23 · openalex created_date 2025/10/10 · openalex updated_date 2026/06/11
Ontogeny—the growth and development of an organism—is among the more poorly understood aspects of the life history of mosasaurs, largely owing to a dearth of fossil material from young individuals. We describe the partial and complete skulls of two subadult individuals of the mosasaurid Tylosaurus proriger from the upper Smoky Hills Chalk Member of the Niobrara Formation in Kansas. We include the more complete of the two specimens in an allometric analysis to better understand proportional changes of the skull through growth. Although our small sample size produces several instances of ‘soft isometry’, we recover the length of the edentulous rostrum as significantly negatively allometric, and quadrate height as significantly positively allometric. In light of our findings, we go on to consider the question of whether T. kansasensis represents an immature ontogimorph of T. nepaeolicus, but find no convincing evidence that this is the case.