Hemiauchenia

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Hemiauchenia
Temporal range: Miocene - Pleistocene, 10–0.010 Ma
Fossil maxilla Hemiauchenia Boulle.png
Fossil maxilla of Hemiauchenia cf. paradoxa
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Family: Camelidae
Tribe: Lamini
Genus: Hemiauchenia
Gervais & Ameghino, 1880
Species

H. macrocephala (Cope, 1893)
H. minima (Leidy, 1886)
H. blancoensis (Meade,1945)
H. vera (Matthew, 1909)
H. paradoxa (Gervais & Ameghino, 1880)

Hemiauchenia,[1] synonym Tanupolama, is a genus of lamine camelids that evolved in North America in the Miocene period approximately 10 million years ago. This genus diversified and moved to South America in the early Pleistocene as part of the Great American Interchange, giving rise to modern lamines. The genus became extinct at the end of the Pleistocene.

Broad features of genus Hemiauchenia[edit]

The genus name is derived from the Ancient Greek: ἡμι- (hēmi-, "half"-)[2] and αὐχήν (auchēn, "neck").[3][nb 1] Species are specified using Latin adjectives or Latinised names from other languages.

Remains of these species have been found in assorted locations around North America including: Florida, Texas, Kansas, Nebraska, Arizona, Mexico, California, Oklahoma, New Mexico, Colorado and Washington. The "large-headed llama", H. macrocephala, was widely distributed in N. and Central America, with H. vera being known from the western U. S. and northern Mexico. H. minima has been found in Florida, and H. guanajuatensis in Mexico.[5]

Distinguishing characteristics of members of Hemiauchenia[edit]

Hemiaucheia vera ( "True hemiauchenia")[edit]

• Relatively low-crowned teeth (part of visible teeth ends close to gums)
• Large caniniform (canine-like) upper first premolar
• Retention of lower third premolar

Hemiaucheia blancoensis ("Blancan hemiauchenia")[edit]

• Named for Blancan Age stratum where typically found
• Shorter mandibular diastema (teeth-spacing between incisors and molars) than macrocephala but shorter than vera
Caniniform upper first premolar
• Absent second premolar
• Upper third premolar present or absent
• Lower crowned molars

Hemiaucheia macrocephala ("Great-headed hemiauchenia")[edit]

• Possesses a larger skull relative to other species
• Long, robust limbs
• Large skeletal size
• Presence of a deciduous upper second premolar
• Fully molariform deciduous second premolar (its infant bicuspids were like molars)
• High-crowned molars
• Thick layer of cementum on the teeth
• Broad mandibular symphysis (line where the bones of the jaw join together) with incisors in a vertical fashion

Hemiaucheia minima ("Least hemiauchenia")[edit]

• Despite being the earliest recognized species, general distinguishing characteristics for H. minima are little known.

Other[edit]

There are also a few lesser known species such as: H. paradoxa, H. seymourensis, H. edensis and H. guanajuatensis. According to which source is consulted, these may or may not be considered legitimate taxa.

Classification history[edit]

Prior to 1974, fossil specimens now thought to be hemiaucheniae where classified as holomeniscus, lama, and tanupolama, until S.David Webb recognised that these North and South American fossil species were part of a single genus.[6] 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.

Notes[edit]

  1. ^ These are used to form a feminine noun to mean "half-neckedness" or "half-carrying the neck"; cf. ὑψηλαυχενία, (hypsēlauchenía, "carrying the neck high").[4]

References[edit]

Further reading[edit]

  • 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).
  • Meachen, Julie A. "A New Species of Hemiauchenia (Camelidae; Lamini)" Diss. University of Florida, 2003. Abstract
  • McKenna, M. C. and S. K. Bell. 1997. Classification of Mammals above the Species Level. Columbia University Press, NY, 631 pp. (camels - pp. 413–416).
  • Nowak, R. M. 1999. Walker's Book of Mammals, vol. 1. Johns Hopkins University Press, Baltimore, pp. 837 – 1936. (camels - pp. 1072–1081)