Jack Tseng, PhD, and Connor J. Grabowski

Jack Tseng, PhD, left, and anatomical sciences master’s student Connor J. Grabowski study a black bear skull using a high-resolution surface scanner.

New Study Sheds Light on Evolution of Carnivoran Skulls

Published February 21, 2018

Jack Tseng, PhD, assistant professor of pathology and anatomical sciences, is lead author on a newly published paper in Science Advances that finds the evolution of carnivoran skull function and shape is much more complex than previously thought.

“One of the main findings from this paper is that the anatomical variations we observed across species are related as intimately to diet as they are to several environmental factors.”
Assistant professor of pathology and anatomical sciences

Several Environmental Factors Influence Process

Carnivorans are the large mammalian order including dogs, cats and bears. While they vary greatly from one species to another, their skulls tend to take the form of a few shapes. Scientists have long attributed this pattern to a shared diet.

The new study, however, demonstrates that there is far more variability in environmental influences of skull function and shape in carnivorans than has been understood.

The paper, “Structure-Function Covariation With Nonfeeding Ecological Variables Influences Evolution of Feeding Specialization in Carnivora,” was published online Feb. 7.

“One of the main findings from this paper is that the anatomical variations we observed across species are related as intimately to diet as they are to several environmental factors,” Tseng says.

“These factors don't necessarily have to do with feeding behavior or preference, but still can significantly influence how different skulls function as food processing tools,” he adds.

Digital, Biomechanical Models of Skulls Utilized

Together with co-author John J. Flynn, PhD, the Frick Curator of Fossil Mammals in the American Museum of Natural History’s Division of Paleontology, Tseng used data from more than 50 living species to develop sophisticated structural and biomechanical models of a broad range of skulls from carnivorans with every imaginable type of diet.

The pair used the models to see how skull shape and size are related to and influenced by the environments of each species.

They found that, for example, sexual maturity and precipitation-related arboreality (how much rain falls in a habitat influences what species eat and how they interact with their environment) can generate structure-function relationships in the skulls of carnivorans that correlate with “masticatory performance.”

Studying the Relationships Between Structure, Function

“This is a common theme between my different model organisms (carnivorans vs. humans),” explains Tseng, research associate at the museum. “The relationships between structure and function allow us to make predictions about how well parts of our body work given their anatomy, but factors influencing those anatomical variations do not necessarily have to be directly related to the functions those variations affect.”

“Understanding the proximal mechanisms of a structural system — be it a bone-crushing carnivore skull or a patient suffering from temporomandibular joint pain — is not the same as understanding the systemic pathways that underlie an evolutionarily adapted system or development of a pathological condition.”

The National Science Foundation and the Frick Fund of the American Museum of Natural History funded the work.