Scientists recently discovered a new species of ancient aquatic predator from well-preserved fossils in the Canadian Arctic. The extinct freshwater fish would have been up to six feet long with a torpedo-shaped body and fangs.
The species, Eusthenopteron jenkinsi, belongs to a group of aquatic animals that is significant to understanding animals’ fin-to-limb transition — which enabled a transition from the water to land. The new, large-bodied species of Eusthenopteron would have lived during the Late Devonian Period (approximately 375 million years ago).
Researchers from Delaware Valley University, the Academy of Natural Sciences of Drexel University, and the University of Chicago published a detailed description of the creature in the June 22 issue of Breviora, the journal of the Museum of Comparative Zoology at Harvard University.
Jason Downs, PhD, a DelVal assistant professor of biology and Academy research associate, was the lead author on the paper officially describing the fish, which was co-authored by Ted Daeschler, PhD, associate curator of vertebrate zoology at the Academy of Natural Sciences as well as a Drexel University professor.
Neil Shubin, of the University of Chicago, and Allison Long ’18, a DelVal biology alumna, also served as co-authors on the paper. Long worked alongside the team while she was a DelVal student as a summer research intern in 2017.
“This is an especially large species for the group Eusthenopteron,” said Dr. Downs. “It had a torpedo-shaped body that suggests a free-swimming lifestyle. Its powerful jaws and many long fangs suggest an active predatory feeding strategy.”
While the ancient predator lived in the water, it is important for understanding life on land.
“The new fossils represent the fourth new species described from the NV2K17 field locality on Ellesmere Island in Canada’s Nunavut Territory,” said Dr. Downs. “They occupy different positions along the fin-to-limb transition. Despite their fish-like appearance, these species are more closely related to limbed animals (including humans) than they are to true fish.”
The new species, Eusthenopteron jenkinsi, is named in honor of the late Dr. Farish A. Jenkins, Jr., a faculty member at Harvard and a participant in the Nunavut Paleontological Expeditions from 1999 to 2008. He was a key contributor to the fossil collecting, anatomical research and the quality of life during the fieldwork in Nunavut.
Dr. Downs said this new, well-preserved example gives scientists a better look at the Eusthenopteron group.
“Eusthenopteron may be the most well-known group of aquatic vertebrates in the key evolutionary transition from fins with supporting rods to limbs with fingers and toes,” said Dr. Downs. “Eusthenopteron jenkinsi, is one of the best preserved and most complete species in the group. Our new research, then, improves understanding of Eusthenopteron, and this can help efforts to reconstruct the relationships among all those vertebrate species in the fin-to-limb transition.”
Dr. Daeschler and Dr. Downs have collaborated on work in the past including a re-description of another extinct fish from the same time period, Hyneria lindae.
“Eusthenopteron jenkinsi (the new species) is another example of a group of lobe-finned fished that we have gotten very familiar with (the tristichopterids),” said Dr. Daeschler. “This group of fish filled the niche of the top predators in Late Devonian freshwater ecosystems. Interestingly, each area where we collect Late Devonian fossil fish, we find a different member of this family. Our recent re-description of Hyneria lindae is an example. Work on other related forms is ongoing.”
The paper describes the anatomy of the new species in detail. The completeness of the fossil material allowed the team to describe parts that are otherwise poorly known for the grouping Eusthenopteron. These include the braincase, shoulder, and pectoral fin.
“Euthenopteron jenkinsi shared its aquatic ecosystem with a variety of other forms including armored fish, lungfish, porolepiform fishes, and Tiktaalik roseae,” said Dr. Daeschler. “Any and all of these animals may have been prey items for E. jenkinsi. Although the fossils are found on a landmass high in the Arctic Circle today, the positions of continental landmasses were very different in the Devonian Period and conditions were likely subtropical.”
In addition to providing a detailed picture of a new Eusthenopteron species, the paper will also help with determining which fossils belong to the grouping.
“The name Eusthenopteron is an old one, and since its first use, there have been questions about how to apply the name or how to recognize new fossils as belonging to the grouping,” said Dr. Downs. “In the paper, we also review how the name Eusthenopteron has been used through its history, and we revise the intentions of the name so that it applies to a simple, easily recognized combination of anatomical features. This revision of the name could allow Eusthenopteron to play a more important role in future efforts to organize the evolutionary relationships among the species in the vertebrate fin-to-limb transition.”
Post by Delaware Valley University