Hemiauchenia

Hemiauchenia; Temporal range: Mid Miocene-Late Pleistocene; ~10.3–0.012 Ma PreꞒ Ꞓ O S D C P T J K Pg N
	Fossil skull of the type species Hemiauchenia paradoxa
Scientific classification
Domain:	Eukaryota
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
	Tanupolama Stock 1928 Holomeniscus Cope 1884

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]

South American fossils

Skull of Hemiauchenia macrocephala

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.^[10] Hemiauchenia paradoxa is suggested to have been a browser.^[11]

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

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^[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 C₃ grasses.^[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]

References

^ "Paleobiology Database - Hemiauchenia basic info". Archived from the original on 2012-10-16. Retrieved 2009-11-15.
^ ^a ^b 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.
^ ^a ^b 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.
^ ἡμι-. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project
^ αὐχήν. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project
^ ὑψηλαυχενία. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project
^ Hulbert Jr., Richard C.; Valdes, Natali (June 6, 2015). "Hemiauchenia macrocephala". Florida Museum. Florida Museum of Natural History. Retrieved 16 May 2021.
^ 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.
^ 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.
^ Hemiauchenia at Fossilworks.org
^ 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.
^ ^a ^b 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 (2023-06-03). "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.
^ ^a ^b 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.
^ 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.
^ "Hemiauchenia macrocephala". University of Florida, Florida Museum of Natural History. Retrieved 23 May 2016.
^ 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.
^ 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.