TAXONOMY & NOMENCLATURE * *How Do We Know This? Like living animals, fossil remains of once-living animals
classified and grouped according to their relationships
each other and to their ancestors.
(Cui et al 2007) (Dalquest 1991) (Honey et al 1998)(Janis et al 2002) (McKenna and Bell 1997) (Scherer 2007) (Webb 1977) (Webb et al 2006)
Describer (Date): Cope 1893
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Artiodactyla (pigs, camels, deer, giraffes, cattle, and their kin) Superfamily: Cameloidea Family: Camelidae Subfamily: Camelinae Tribe Lamini (includes extinct genera plus modern llamas, vicunas, guanacos) Genus: Hemiauchenia Species:Hemiauchenia macrocephala - Extinct Large-headed or Stilt-legged Camel Species:Hemiauchenia blancoensis Species:Hemiauchenia vera Species:Hemiauchenia paradoxa Tribe: Camelini (extinct genera plus modern dromedary and bactrian camels)
Taxonomic History and Nomenclature
Several researchers have re-established the validity of this species after it was earlier synonymized. (Honey et al 1998)
Some taxonomists have questioned the validity of Hemiauchenia paradoxa in South America, but recent studies have helped distinguish this species from other camelids. (Scherer 2007)
The camelid family began in North America some 46 million years ago in the Eocene Epoch.
(Whistler and Webb 2005)
Sheep-sized Probrotherium is the most primitive camel-like ancestor. (Janis et al 2002)
A drying tend that produced the first areas of true savanna in North America coincided with the rise of camels. (Webb 1977)
A small camel, Miotylopus, lived in southern California, around 28 million years ago.
New DNA studies reveal that the two camel family tribes separated around 25 million years ago, much earlier than previously believed. (Cui et al 207)
Between 20 and 14 million years ago, some 13 genera of camels flourished throughout North America. (Honey et al 1998)
During the Pleistocene, five genera of camels lived in North America. (Dalquest 1992)
Hemiauchenia closely related to extinct Camelops. (Webb et al 2006).
Hemiauchenia was probably ancestral to other North and South American llamas (Webb et al 2006)
South American guanacos, alpacas, vicuñas are among its descendants (Webb 2006)
By 10,000 years ago, Hemiauchenia was extinct.
DISTRIBUTION & HABITAT * *How Do We Know This? Scientists use knowledge of the earth's rocks, global plate tectonic movements,
and the chemical process of fossilization
to make sense of fossil distribution patterns and ancient habitats.
(Scherer et al 2007) (Honey et al 1998) (Webb et al 2006)
Florida, Texas, Great Plains states in U.S., South America including Argentina, Uruguay, Brazil, Chile, Peru, Venezuela, Bolivia, Ecuador, Paraguay. (Honey et al 1998)
(Scherer et al 2007)
In California: rare at La Brea deposits, more common in San Joaquin Valley, Mojave Desert, possibly in Anza Borrego Desert (Webb 2006) (Shaw 2001).
Like modern camels,adapted to open spaces and dry land.
PHYSICAL CHARACTERISTICS* *How Do We Know This? Careful study of fossil bone or tooth anatomy yields much exact information
about placement and strength of muscles, tendons, ligaments, nerves, and blood vessels.
In rare cases, skin and hair impressions or actual skin or hair is preserved.
Body weight is more difficult to gauge because fat leaves no impression on the skeleton.
(Shaw 2001) (Janis et al 2002) (Shaw 2001)(Webb 2006)
Estimated Body Weight: 300 kg (661 lbs) Estimated Height at Shoulder: 2 m (6.5 ft) Tail Length: A short tail
A small camel similar in size and appearance to the modern domestic llama, except for its longer neck and more slender limbs
Fossils in the genusare best distinguished by long slender legs, long and narrow foot bones, and details of the anatomy of its terminal toe bones (Webb 2006)
High crowned (hypsodont) teeth
Canine teeth are recurved and somewhat flattened sideways
Unknown but most likely similar to modern dromedary and bactrian camels
Dalquest (1992) reported Hemiauchenia may have had more sexual dimorphism than seen in modern llamas.
Other Physical Characteristics
As in all camelids, long toe and finger bones (medapodials) allow for a long stride and a pacing gait (Webb et al 2006)
Limb proportions mirror those of the African gerenuk
Some researchers speculate Hemiauchenia, like the gerenuk, had the ability to browse upright on hind legs (Shaw 2001)
BEHAVIOR & ECOLOGY* *How Do We Know This? Since direct observation of a fossil animal's behavior isn't possible, paleontologists
comparison and contrast with living animals for guidance. Tracks can sometimes
reveal further clues.
(Janis et al 2002) (Webb 2006)
Not known, but may have been similar to modern camels that live in small family groups of 2-20 individuals.
One report of three adults and a juvenile that fell in the same event into an entrance fissure of a New Mexico cave. (Harris 2007)
Perhaps this group represented a small herd.
Like modern camels, highly adapted for a running
Long slender limbs with a long stride.
Hemiauchenia probably had the running pace gait unique to modern camels (Janis et al 2002)
This is suggested by this camel's feet which are like those of modern camels (Janis et al 2002)
Several species of camels co-existed with Hemiauchenia, each most likely feeding in different places or on different plants. (Webb 2006)
DIET & FEEDING* *How Do We Know This? Clues to fossil mammals' diets come from teeth,skull shape,
from fossil dung and gut contents, from
lab analysis of oxygen
in bone and teeth,
looking at diets of similar modern animals.
A herbivore adapted for browsing or mixed browsing/grazing (Dompierre & Churcher 1996)
A herbivore with high crowned teeth like Hemiauchenia often assumed to be a grazer feeding mostly on abrasive grasses (Webb 2006) (Feranec 2003)
Looking at carbon isotopes in Hemiacuchenia teeth, Feranec (2003) concluded:
This herbivore was mainly a browser feeding on more tropical plants
Hemiauchenia also grazed on some grasses and drought tolerant plants.
Hemiauchenia was an intermediate feeder that could graze and browse.
REPRODUCTION & DEVELOPMENT * *How do We Know This? Isotope studies of elements present fossil bones and tusks
about timing of reproductive stress, and timing of nursing.
Clues to stages of development come from tooth
replacement patterns and closure of sutures
in skull and limb bones.
Juvenile Hemiauchenia are recognized by the same criteria that identify
modern young camels
(baby teeth, unfused ends of long bones and unfused vertebrae)
Old age individuals are identified by large size, worn teeth, and age-related arthritic bones.
Medium to large-sized sized cats, and wolves might have preyed on these small camels.
One isotope study of Smilodongracilis teeth in Florida found this predator had a diet of herbivores such as Hemiauchenia that fed mainly on, wet-climate C3 plants. (Feranec 2002)
DISEASES AND PATHOLOGY*
*How do We Know This? Abnormalities in fossils bones may show
evidence of arthritis, cancer, nutritional stress, fractures and more.
None presently known.
Important Web Resources (including where to view fossils in museums):
FAUNMAP -- This useful website created and maintained by the Illinois State Museum gives the known distributions in map and list format for many fossil species in North America.
The Paleobiology Database -- This site is a scientific organization run by paleontological researchers from around the world. It features taxonomic and distribution information for the entire fossil record.