Hemiauchenia

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Hemiauchenia
Temporal range: Mid Miocene-Late Pleistocene
~10.3–0.012 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)
H. seymourensis
H. edensis
H. guanajuatensis

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 Biotic 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.

North American fossils[edit]

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 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.[5]

South American fossils[edit]

Fossils of Hemiauchenia in South America are restricted to the Pleistocene and have been found in the Luján and Agua Blanca Formations of Buenos Aires Province and in Córdoba Province, Argentina, the Tarija Formation of Bolivia, and in Paraíba, Ceará, and in the Touro Passo Formation of Rio Grande do Sul, Brazil.[6]

Distinguishing characteristics of members of Hemiauchenia[edit]

Hemiauchenia 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

Hemiauchenia blancoensis ("Blancan hemiauchenia")[edit]

Hemiauchenia 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

Hemiauchenia minima ("Least hemiauchenia")[edit]

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

Other species[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.[citation needed]

Classification history[edit]

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.[7] 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)