Hemiauchenia[1] is a genus of laminoid camelids that evolved in North America in the Miocene period about 10 million years ago. This genus diversified and entered South America in the Late Pliocene about 3-2 million years ago, as part of the Great American Biotic Interchange. The genus became extinct at the end of the Pleistocene. The monophyly of the genus has been considered questionable, with phylogenetic analyses finding the genus to paraphyletic or polyphyletic, with some species suggested to be more closely related to living lamines than to other Hemiaucenia species.[2][3]
Broad features of genus Hemiauchenia
The genus name is derived from the Ancient Greek: ἡμι- (hēmi-, "half"-)[4] and αὐχήν (auchēn, "neck").[5][nb 1] Species are specified using Latin adjectives or Latinised names from other languages.
North American fossils
Restoration of Hemiauchenia (right) and other animals of the Rattlesnake Formation fleeing a volcanic eruption
Remains of these species have been found in assorted locations around North America, including Florida, Texas, Kansas, Nebraska, Arizona, Mexico, California, Oklahoma, New Mexico, Oregon, Colorado, and Washington.[7][8]
The "large-headed llama", H. macrocephala, was widely distributed in North and Central America, with H. vera being known from the western United States and northern Mexico. H. minima has been found in Florida, and H. guanajuatensis in Mexico.[9]
Broad mandibular symphysis (line where the bones of the jaw join together) with incisors in a vertical fashion
Thought to have been browsers[12] and mixed feeders.[13] Suggested to be less closely related to modern Lama and Vicugna than H. paradoxa is.[3]
Native to the southern United States, spanning from California to Florida,[14] and as far north as Nebraska.[13] Also present in Mexico.[12]
H. minima
Despite being the earliest recognized species, general distinguishing characteristics for H. minima are little known.
Other species
Also, a few lesser known species, such as H. paradoxa, H. seymourensis, H. edensis and H. guanajuatensis, have been found. Depending on which source is consulted, these may or may not be considered legitimate taxa.[citation needed]
Classification history
Prior to 1974, fossil specimens now thought to be Hemiauchenia were classified as Holomeniscus, Lama, and Tanupolama, until S. David Webb proposed that these North and South American fossil species were part of a single genus.[15] This has been accepted by all subsequent researchers, although in 2013, Carolina Saldanha Scherer questioned the inclusion of a certain North American species and suggested that Hemiauchenia is paraphyletic.[2]
Diet
Over the Pliocene and Pleistocene, Hemiauchenia was an intermediate feeder that preferred browsing with a hypsodont dentition.[16] According to δ13C analyses of H. paradoxa teeth from the Touro Passo and Santa Vitória Formations of Brazil, H. paradoxa was primarily a grazer of C3grasses.[17]
Notes
^These are used to form a feminine noun to mean "half-neckedness" or "half-carrying the neck"; cf.ὑψηλαυχενία, (hypsēlauchenía, "carrying the neck high").[6]
^Hulbert Jr., Richard C.; Valdes, Natali (June 6, 2015). "Hemiauchenia macrocephala". Florida Museum. Florida Museum of Natural History. Retrieved 16 May 2021.
^Grayson, D. K. 1994. The extinct Late Pleistocene mammals of the Great Basin. Pages 55–85 inNatural history of the Colorado Plateau and Great Basin ( K. T. Harper, J. L. ST. Clair, K. H. Thorne, and W. M. Hess, editors). University Press of Colorado, Niwot.
Honey, J. H., J. A. Harrison, D. R. Prothero, and M. S. Stevens. 1998. Camelidae. pp. 439–462. In: Evolution of Tertiary Mammals of North America, Eds: C. M. Janis, K. M. Scott, and L. L. Jacobs, Cambridge University Press, Cambridge, United Kingdom. 691 pp.
Hulbert, R. C. 1992. A checklist of the fossil vertebrates of Florida. Papers in Florida Paleontology, no. 6:25-26.
Kurtén, B. and E. Anderson. 1980. Pleistocene Mammals of North America. Columbia University Press, NY, 442 pp. (camels - 301, 306-307).
