Hemiauchenia

Hemiauchenia Temporal range: Mid Miocene – Late Pleistocene c. 10.3 – 0.012  Ma PreꞒ Ꞓ O S D C P T J K Pg N
Reconstructed H. macrocephala skeleton, Florida Museum of Natural History
Scientific classification
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 H. mirim Greco et al., 2022
Synonyms
TanupolamaStock 1928HolomeniscusCope 1884

Hemiauchenia ^[1] is a genus of lamine 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 three to two 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 (llamas and relatives) than to other Hemiauchenia species. ^{[2] [3]}

This genus gave rise to the genus Lama , of which modern lamines belong to.

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]

H. macrocephala gave rise to modern lamines (guanacos, vicuñas, and their domesticated forms) when a population migrated southward towards South America. ^{[10] [11] [12]}

South American fossils

Fossil skull of the type species, H. paradoxa

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 Córdoba Province, Argentina, the Tarija Formation of Bolivia, Pilauco of Osorno, Los Lagos, Chile and Paraíba, Ceará, and the Touro Passo Formation of Rio Grande do Sul, Brazil. ^[13] Hemiauchenia paradoxa is suggested to have been a browser. ^[14]

Distinguishing characteristics of members of Hemiauchenia

H. vera

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

H. blancoensis

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

H. macrocephala

Skull of H. macrocephala

• 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

Thought to have been browsers ^[15] and mixed feeders. ^[16] 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, ^[17] and as far north as Nebraska. ^[16] Also present in Mexico. ^[15]

H. minima

Right hind limb of H. minima, Florida Museum of Natural History

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

Other species

Toe bone of H. edensis, Florida Museum of Natural History

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. ^[18] 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. ^[19] In Florida, Hemiauchenia populations were predominantly strict C₃ browsers before the Blancan-Irvingtonian boundary but shifted towards a mixed feeding diet at the start of the Irvingtonian, a dietary shift coinciding with the arrival of Mammuthus in North America. This dietary shift has proposed to have been caused by floral changes as well as potentially by the ecosystem engineering of Mammuthus increasing the prevalence of open habitats. ^[20] 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 C₃ grasses. ^[21]

See also

• Paleontologyportal
• Prehistoric mammalsportal

Notes

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"). ^[6]

References

1. "Paleobiology Database - Hemiauchenia basic info". Archived from the original on 2012-10-16. Retrieved 2009-11-15.
2. Scherer, Carolina Saldanha (March 2013). "The Camelidae (Mammalia, Artiodactyla) from the Quaternary of South America: Cladistic and Biogeographic Hypotheses" . Journal of Mammalian Evolution . 20 (1): 45–56. doi:10.1007/s10914-012-9203-4. ISSN   1064-7554.
3. Lynch, Sinéad; Sánchez-Villagra, Marcelo R.; Balcarcel, Ana (December 2020). "Description of a fossil camelid from the Pleistocene of Argentina, and a cladistic analysis of the Camelinae". Swiss Journal of Palaeontology . 139 (1): 5. Bibcode:2020SwJP..139....8L. doi: 10.1186/s13358-020-00208-6 . ISSN   1664-2376. PMC   7590954 . PMID   33133011.
4. ἡμι- . Liddell, Henry George ; Scott, Robert ; A Greek–English Lexicon at the Perseus Project
5. αὐχήν . Liddell, Henry George ; Scott, Robert ; A Greek–English Lexicon at the Perseus Project
6. ὑψηλαυχενία. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project
7. Hulbert Jr., Richard C.; Valdes, Natali (June 6, 2015). "Hemiauchenia macrocephala". Florida Museum. Florida Museum of Natural History. Retrieved 16 May 2021.
8. Heckert, Andrew B. Ph D. "Pliocene (latest Hemphillian and Blancan) vertebrate fossils from the Mangas Basin, southwestern New Mexico". libres.uncg.edu. Retrieved 2022-01-17.
9. Ruez, D. R. (2005-09-30). "Earliest Record of Palaeolama (Mammalia, Camelidae) with Comments on "Palaeolama" guanajuatensis". Journal of Vertebrate Paleontology . 25 (3). Society of Vertebrate Paleontology: 741–744. doi:10.1671/0272-4634(2005)025[0741:eropmc]2.0.co;2. JSTOR   4524496. S2CID   86522528.
10. Meachen, Julie A. (2005-12-31). "A New Species of Hemiauchenia (Artiodactyla, Camelidae) from the Late Blancan of Florida". Bulletin of the Florida Museum of Natural History. 45 (4). University Press of Florida: 435–448. doi:10.58782/flmnh.stwk6834.
11. Cowie, Helen (2017-05-15). Llama. Reaktion Books. p. 10. ISBN   978-1-78023-786-2.
12. Defler, Thomas (2018-12-19). History of Terrestrial Mammals in South America: How South American Mammalian Fauna Changed from the Mesozoic to Recent Times. Springer. pp. 266–267. ISBN   978-3-319-98449-0.
13. Hemiauchenia at Fossilworks.org
14. Lopes, Renato Pereira; Scherer, Carolina Saldanha; Pereira, Jamil Corrêa; Dillenburg, Sérgio Rebello (July 2023). "Paleoenvironmental changes in the Brazilian Pampa based on carbon and oxygen stable isotope analysis of Pleistocene camelid tooth enamel" . Journal of Quaternary Science . 38 (5): 702–718. Bibcode:2023JQS....38..702L. doi:10.1002/jqs.3502. ISSN   0267-8179 . Retrieved 21 September 2025– via Wiley Online Library.
15. Marín-Leyva, Alejandro Hiram; Delgado-García, Sabrina; García-Zepeda, María Luisa; Arroyo-Cabrales, Joaquín; López-García, J. Ramón; Plata-Ramírez, Ramón Adrián; Meléndez-Herrera, Esperanza (3 June 2023). "Environmental inferences based on the dietary ecology of camelids from west-central Mexico during the Late Pleistocene" . Historical Biology . 35 (6): 1011–1027. Bibcode:2023HBio...35.1011M. doi:10.1080/08912963.2022.2073822. ISSN   0891-2963.
16. Semprebon, Gina M.; Rivals, Florent (September 2010). "Trends in the paleodietary habits of fossil camels from the Tertiary and Quaternary of North America" . Palaeogeography, Palaeoclimatology, Palaeoecology . 295 (1–2): 131–145. Bibcode:2010PPP...295..131S. doi:10.1016/j.palaeo.2010.05.033.
17. Grayson, D. K. 1994. The extinct Late Pleistocene mammals of the Great Basin. Pages 55–85 in Natural 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.
18. "Hemiauchenia macrocephala". University of Florida, Florida Museum of Natural History. Retrieved 23 May 2016.
19. Feranec, Robert S. (Spring 2003). "Stable isotopes, hypsodonty, and the paleodiet of Hemiauchenia (Mammalia: Camelidae): a morphological specialization creating ecological generalization" . Paleobiology . 29 (2): 230–242. doi:10.1666/0094-8373(2003)029<0230:SIHATP>2.0.CO;2. ISSN   0094-8373 . Retrieved 6 May 2024– via Cambridge Core.
20. Feranec, Robert S.; MacFadden, Bruce J. (15 September 2000). "Evolution of the grazing niche in Pleistocene mammals from Florida: evidence from stable isotopes". Palaeogeography, Palaeoclimatology, Palaeoecology . 162 (1–2): 155–169. doi:10.1016/S0031-0182(00)00110-3 . Retrieved 21 September 2025– via Elsevier Science Direct.
21. Carrasco, Thayara S.; Scherer, Carolina S.; Ribeiro, Ana Maria; Buchmann, Francisco S. (12 April 2022). "Paleodiet of Lamini camelids (Mammalia: Artiodactyla) from the Pleistocene of southern Brazil: insights from stable isotope analysis (δ 13 C, δ 18 O)" . Paleobiology . 48 (3): 513–526. Bibcode:2022Pbio...48..513C. doi:10.1017/pab.2022.10. ISSN   0094-8373 . Retrieved 5 May 2024– via Cambridge Core.

Further reading

• 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)"; Archived 2021-12-13 at the Wayback Machine " 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)