Alticonodon

Alticonodon is a genus of extinct mammal from the Late Cretaceous of North America. It is the geologically youngest known eutriconodont, and is a fairly more specialised animal than earlier representatives of this clade.[1]

Alticonodon
Temporal range: Santonian, 85–84 Ma
↓
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Subphylum:
Vertebrata
Class:
Mammalia
Order:
†Eutriconodonta
Family:
†Triconodontidae
Subfamily:
†Alticonodontinae
Genus:
†Alticonodon

Foz, 1969
Type species
†Alticonodon lindoei
Fox, 1969

Description

Alticonodon is currently a monotypic genus, represented exclusively by A. lindoei. Its is known from the Milk River Formation deposits of the early Campanian of Alberta, Canada. It is known from two specimens: a dentary fragment bearing two molars, and an isolated lower last molar.

Classification

Alticonodon has been consistently recovered as a triconodontid, and more specifically as an alticonodontine,[2] though the latter term may be redundant in relation to the rest of Triconodontidae.[3]

Biology

Compared to earlier eutriconodonts, Alticonodon has molars better specialised for shearing.[4][5] As eutriconodonts as a group had shearing molars due to their carnivorous habits,[6] it can be inferred that Alticonodon was hypercarnivorous.

This ecological speciation might have come due to competition with other mammals in the region, such as the various metatherians.[7]

Ecology

The Milk River Formation is a rich fossil environment that covered near-shore and terrestrial deposits. It included a few dinosaur species like Saurornitholestes and Acrotholus, as well as a variety of other vertebrate such as the crocodilian Gilchristosuchus, various turtles and fish.

The mammalian fauna was primarily dominated by metatherians and multituberculates, as usual for Late Cretaceous mammaliafaunas, but a variety of older taxa remained; besides Alticonodon, there was also the symmetrodont Symmetrodontoides, and the illusive Potamotelses and picopsids. These were the last non-therian mammals (other than the highly successful multituberculates) in North America, suggesting a relictual element to the region's fauna.

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References
  1. R. C. Fox. 1969. Studies of Late Cretaceous vertebrates. III. A triconodont mammal from Alberta. Canadian Journal of Zoology 47:1253-1256
  2. L. C. Gaetano and G. W. Rougier. 2011. New materials of Argentoconodon fariasorum (Mammaliaformes, Triconodontidae) from the Jurassic of Argentina and its bearing on triconodont phylogeny. Journal of Vertebrate Paleontology 31(4):829-843 [R. Benson/R. Benson]
  3. Thomas Martin, Jesús Marugán-Lobón, Romain Vullo, Hugo Martín-Abad, Zhe-Xi Luo & Angela D. Buscalioni (2015). A Cretaceous eutriconodont and integument evolution in early mammals. Nature 526, 380–384. doi:10.1038/nature14905
  4. R. C. Fox. 1969. Studies of Late Cretaceous vertebrates. III. A triconodont mammal from Alberta. Canadian Journal of Zoology 47:1253-1256
  5. Richard C. Fox, Studies of Late Cretaceous vertebrates. III. A triconodont mammal from Alberta Article in Canadian Journal of Zoology 47(6):1253-1256 · February 2011 doi:10.1139/z69-196
  6. Zofia Kielan-Jaworowska, Richard L. Cifelli, Zhe-Xi Luo (2004). "Chapter 7: Eutriconodontans". Mammals from the Age of Dinosaurs: origins, evolution, and structure. New York: Columbia University Press. pp. 216–248. ISBN 0-231-11918-6.
  7. R. C. Fox. 1969. Studies of Late Cretaceous vertebrates. III. A triconodont mammal from Alberta. Canadian Journal of Zoology 47:1253-1256
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