DEERFIELD, IL (December 2008) When you take a bite out of a hamburger or chomp down on a piece of gum, you share this function of the lower jaw with the vast majority of animals. But not all: for some animals, lifting the head rather than dropping the jaw is a good idea. This bizarre reversal of how feeding occurs was achieved in 210-million-year-old amphibians, as described in the December 2008 issue of the Journal of Vertebrate Paleontology.
The animals in question are plagiosaurs – a group of flat-headed, armored amphibians unrelated to living amphibians such as frogs, salamanders and caecilians. Fossils of this group of animals have been known for a hundred years, but finds of complete specimens have been elusive. The article, authored by a team led by Dr. Farish A. Jenkins, Jr. of Harvard University, describes new, relatively complete material of a plagiosaur called Gerrothorax pulcherrimus from the 210-million-year-old Fleming Fjord Formation of East Greenland. “With their very flat, heavily armored bodies, short, stubby limbs, massive shoulder girdles and well-developed gills, these amphibians are an oddity by any measure,” says Dr. Jenkins. “The animals could throw their heads upward and backward, creating a huge mouth gape with only the slightest lowering of the lower jaw… perfect for a bottom-dwelling ambush predator,” he continues. By special adaptation of the joint between the skull and first neck vertebra, the animal was able to raise its head relative to its lower jaw by as much as 50 degrees, giving it the wide gape it needed to swallow its unsuspecting prey. “That the same species is found in Greenland as well as Western Europe and Scandinavia suggests that their unique structure was hugely successful,” said Dr. Anne Warren of La Trobe University in Melbourne, Australia, a member of the team that conducted the study.
ABOUT THE SOCIETY OF VERTEBRATE PALEONTOLOGY
Founded in 1940 by 34 paleontologists, the Society now has more than 2,300 members representing professionals, students, artists, preparators and others interested in vertebrate paleontology. It is organized exclusively for educational and scientific purposes, with the object of advancing the science of vertebrate paleontology.
Journal of Vertebrate Paleontology
The Journal of Vertebrate Paleontology (JVP) is the leading journal of professional vertebrate paleontology and the flagship publication of the Society. It was founded in 1980 by Dr. Jiri Zidek and publishes contributions on all aspects of vertebrate paleontology.
Reconstruction of head lifting during aquatic feeding in Gerrothorax pulcherrimus, Upper Triassic, Greenland. Drawings by L. L. Meszoly; composition arranged by D. Smiley
Dr. Farish A. Jenkins, Jr.
Alexander Agassiz Professor of Zoology
Department of Organismic and Evolutionary Biology, and Museum of Comparative Zoology
Dr. Neil H. Shubin
Department of Organismal Biology and Anatomy
The University of Chicago
Chicago IL 60637
Dr. Stephen M. Gatsey
Department of Ecology and Evolutionary Biology
Providence, RI 02912
Dr. Anne Warren
Department of Zoology
La Trobe University
Melbourne, Victoria 3086, Australia
(Originally posted Dec. 11, 2008.)