Press Release - A well-preserved skeleton reveals the ecology and evolution of early carnivorous mammals

December 8, 2015

DEERFIELD, IL USA (December, 2015) – Prior to the rise of modern day mammalian carnivores (lions and tigers and bears, as well as weasels, raccoons, wolves and other members of the order Carnivora), North America was dominated by a now extinct group of mammalian carnivores – the hyaenodontids.  While fossils of hyaenodontids are relatively common from the early Eocene (between 50 and 55 million years ago), most of these are specimens of teeth.  A new find of a nearly complete skeleton, described in the most recent issue of the Journal of Vertebrate Paleontology, has allowed for a more detailed study of the ecology and evolutionary relationships of these early carnivores.

The recent find, a skeleton of the hyaenodontid Galecyon, was found in an area of Wyoming well-known for fossils of this age.  Lead author Shawn Zack of the University of Arizona says, “The skeleton of Galecyon shows why we keep looking for fossils even in places where we already have a lot of specimens.  When this skeleton was found, tens of thousands of mammalian fossils had been collected from the Bighorn Basin, but this was the first decent skeleton of this animal.”

Galecyon was about the size of a modern coyote, and the new find allowed the researchers, Zack and co-author Ken Rose of Johns Hopkins University, to infer the locomotory abilities of this fossil taxon.  “Galecyon may have moved around like a living wolverine or skunk,” says Zack, “probably not much of a runner, but spending most of its time on the ground, while some of its relatives spent a lot more time in the trees.”

In addition to telling us something about the way this fossil animal lived, the fossil also allowed the researchers to investigate the ecological and evolutionary relationships among hyaenodontids.  Since teeth are the most commonly found elements of the skeleton, this is normally done using dental characters, but the new specimen allows for the addition of characters in other parts of the skeleton.

“This study is a ‘tour de force’ in terms of the completeness of the description, imaging and analysis – a great example of how to combine systematics with functional morphology and phylogenetic reconstruction to produce a solid result and testable hypotheses for future work” says Gregg Gunnell, a paleontologist from Duke University not involved with the study.

“This study shows that postcranial and dental morphology support different patterns of hyaenodontid relationships. That is an indication that there is still a lot to learn about hyaenodontid evolution,” says Zack.  In addition, “This study shows that early hyaenodontids had diverse habitat preferences, which helps explain how several different hyaenodontids were able to coexist in the same faunas, despite having similar diets and comparable body sizes.”


About the Society of Vertebrate Paleontology
Founded in 1940 by thirty-four paleontologists, the Society now had 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 objective of advancing the science of vertebrate paleontology.
Society of vertebrate Paleontology:
Journal of Vertebrate Paleontology
The Journal of vertebrate Paleontology (JVP) is the leading journal of the 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.
Journal Web site:

Zack, S. P., and K. D. Rose. 2015. The postcranial skeleton of Galecyon: evidence for morphological and locomotor diversity in early Hyaenodontidae (Mammalia, Hyaenodontida). Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2014.1001492.
For complimentary access to the full article, visit:
The article appears in the Journal of Vertebrate Paleontology 31(1), published by Taylor and Francis

Department of Basic Medical Sciences
University of Arizona College of Medicine–Phoenix
Phoenix, Arizona 85004, U.S.A.

Johns Hopkins University School of Medicine
Baltimore, Maryland 21205, U.S.A.

Other Experts Not Associate with the Study
P. David Polly
Indiana University
Department of Geological Sciences
Indiana University
1001 E. 10th St
Bloomington, IN 47405-1405
(812) 855-5582

Gregg Gunnell
Duke University Lemur Center
Division of Fossil Primates
Duke University Lemur Center
1013 Broad Street
Durham, NC 27705-5000
(919) 684-9820

Figure 1: Photograph of typical fossiliferous exposures of the Willwood Formation in the southern Bighorn Basin.  Photograph by K. Rose.
Figure 1: Photograph of typical fossiliferous exposures of the Willwood Formation in the southern Bighorn Basin.  Photograph by K. Rose.

Figure 2: Ankle bones of Galecyon in dorsal (top) view.  Elements are (clockwise from top left) astragalus, calcaneus, and cuboid.  Image by S. Zack.
Figure 2: Ankle bones of Galecyon in dorsal (top) view.  Elements are (clockwise from top left) astragalus, calcaneus, and cuboid.  Image by S. Zack.

Figure 3: Humerus (arm) bone of Galecyon in anterior (front view).  Image by S. Zack.
Figure 3: Humerus (arm) bone of Galecyon in anterior (front view).  Image by S. Zack.