Gustafsonia

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Gustafsonia
Temporal range: 39–33 
Ma
Early Oligocene
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: †Amphicyonidae
Genus: †Gustafsonia
Tomiya & Tseng, 2016
Species:
†G. cognita
Binomial name
†Gustafsonia cognita
(Gustafson, 1986)
Synonyms
Miacis cognitus

Gustafsonia is an extinct

University of Texas
holds this specimen. It is the only confirmed fossil of this species.

Morphology

Fossil

The holotype is missing the mandible, upper canines, and zygomatic arch. The remainder of the skull is damaged, but relatively intact.

Teeth

It preserves the old style of many teeth, probably having forty-two, as compared to most modern carnivorans in the low thirties. With the later species of Miacis, the size of the certain teeth were decreasing, namely the foremost

felids. Most members of Miacoidea have forty four teeth, so this advanced species has already lost two bottom premolars. Though the upper canines are missing, these teeth can be reconstructed due to the foramen for the tooth root remaining intact. These canines were not particularly long or short, though they were not stout or shaped for great stress. The molars of this species were small and not suited for grinding large amounts of material. The premolars show carnassial
form that makes carnivorans unique and were good for slicing rather than crushing or grinding.

drawing of the original holotype
The African palm civet (Nandinia binotata), a modern species resembling Gustafsonia cognita in skull morphology.

Comparison to modern species

The skull of G. cognita is long and low. In skull morphology, the African palm civet, Nandinia binotata takes the prize of looking most like its distant relative.

Digital morphology and CT scanning

The information core for the Digital Morphology library is generated using a state-of-the-art high-resolution X-ray computed tomographic (X-ray CT) scanner. This instrument is comparable to a conventional medical diagnostic CAT scanner, but with greater resolution and penetrating power. The CT scanner was custom built and optimally designed to explore the internal structure of natural objects and materials at mega- and microscopic levels. This instrument is at the center of The University of Texas High-Resolution X-ray Computed Tomography Facility (UTCT), a designated NSF-supported Multi-User Facility. Now in its seventh year, UTCT has scanned hundreds of rocks, meteorites, fossils, and modern organisms, providing unique data and visualizations for a wide range of interests in education and research.

The holotype of Gustafsonia cognita was made available to the University of Texas High-Resolution X-ray CT Facility for scanning by Dr. Timothy Rowe of The University of Texas at Austin, Department of Geological Sciences. The specimen was scanned by Richard Ketcham on 3 December 2007 along the coronal axis for a total of 1010 slices. Each 1024×1024-pixel slice is 0.08551 mm thick, with an interslice spacing of 0.08551 mm and a field of reconstruction of 40 mm.[4]

Surface views allow one to roll, pitch, and yaw the specimen to see the fossil as though you were holding it in your hand. A second series is much more in depth slice movies, with coronal, transverse, and sagittal slices of the fossil. The last series is a dynamic cutaway from coronal, transverse, and sagittal angles as well.

a facial profile of Gustafsonia cognita

Evolution

The

pinnipeds, skunks, ferrets, amphicyonids, etc.). *Gustafsonia*, being an early amphicyonid, is a caniform. Around this time, the formerly dominant oxyaenids and mesonychians began to decline as a result of climatic changes; open niches left by these predators were quickly filled by some of the carnivorans, namely the feliform nimravids
, and by the hyaenodonts; hyaenodonts would remain successful in various predatory niches until the end of the Middle Miocene, but the carnivorans were much more diverse, becoming the dominant group of land predators in Laurasia by the start of the Miocene and fully taking over once hyaenodonts entered terminal decline in the Late Miocene.

Ecology

the local, large oreodont Merycoidodon
the medium-sized equid Mesohippus

Reeves bonebed is well known for its

perissodactylid. The medium-sized herbivores Agriochoerus, Hyracodon, Mesohippus and Leptotragulus, were again probably Hyaenodon prey and Miacis would have left it alone completely. Leptomeryx inhabited the same range and was smaller. Its young would have been ample prey, and the adults might have been tackled. The rodent Ardynomys was of perfect size and would have been hunted by Miacis. Within the region, there were many smaller rodents, and with so many animals in the area that were too large for Miacis to kill, it is likely that the small animal, somewhere between the size of a cat and a begal, would have been a prolific rodent hunter and a hunter of Bathygenys.[5]

References

  1. doi:10.1111/j.1475-4983.2010.00963.x
  2. PMID 27853569
    .
  3. ^ "Miacis cognitus Gustafson 1986 (carnivoran)". Paleobiology Database. Archived from the original on March 25, 2012.
  4. ^ Digimorph (Digital morphology). "Miacis cognitus, extinct carnivoran".
  5. ^ University of Texas, Austin. "Reeves bonebed".
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