Tanyrhinichthys, a long-rostrumed Carboniferous ray-finned fish (Actinopterygii), and the evolution of elongate snouts in fishes

Jack next to a Tanyrhinichthys

Students

2019
College

Faculty

Assistant Professor of Earth and Environmental Science

Project Summary

     My goal this summer was to learn about ancient ray-finned fishes known as paleoniscoids, a group that I aim to study in the future as a paleontologist. They are found in the fossil record of the Late Paleozoic, 360-250 million years ago. The paleoniscoids are a poorly known group, even though they represent the early evolutionary history of the ray-finned fishes. Ray-finned fishes represent over half of modern vertebrate species, inhabiting every conceivable aquatic environment and having great importance in both industry and biological research. In order to gain knowledge and experience with this group, I visited important collections of fossil fishes in London and Chicago. During these visits, I was able to examine, draw, and photograph hundreds of specimens of paleoniscoids from all over the world. In the process, I was able to learn a great deal about the morphology and diversity of these fishes.

     I also worked on re-describing Tanyrhinichthys, a paleoniscoid from the Pennsylvanian of New Mexico (about 305 million years ago). This fish stands out because the bones at the front of its skull are lengthened into an elongate rostrum or snout that projects beyond its orbits and nares. Tanyrhinichthys was originally described from a single, incomplete specimen. Recently, however, six better preserved specimens were uncovered. I used these specimens to revise our understanding of the morphology of this fish, in the process learning a lot about the anatomy of paleoniscoids. I reconstructed Tanyrhinichthys as a living animal and compared it to modern fishes in order to make inferences about its ecology. I found that it was most likely a bottom feeding predator, similar to modern sturgeons. I was also able to place Tanyrhinichthys into context with other ray-finned fishes that possess elongate rostra, finding that its rostrum is an early iteration of a type of structure that appears in a wide variety of ray-finned fishes across their 400 million year history.

       Working on this project, and on fishes with elongate rostra in particular, gave me an idea for my senior thesis project. I will be conducting an exhaustive survey of the ecology and morphology of ray-finned fishes bearing elongate rostra in order to determine if the patterns I observed in my brief survey hold when all of the known taxa bearing these structures are considered. I am also interested in how the patterns surrounding the occurrence of these structures can be used to make inferences regarding how convergent evolution works on macroevolutionary timescales (over millions of years). Working with Dr. Sallan this summer has been immeasurably beneficial in preparing to pursue a career as a paleontologist. I was able to learn about how fossil fishes are described, reconstructed, and analyzed from an expert. I also had the opportunity to meet with two other world experts in fish paleontology during my travels. Overall, I was able to gain a great deal of both knowledge and experience in my chosen field of research and significantly further my personal research goals.