Hemicyonidae
Encyclopedia
Hemicyonidae is an extinct family of so-called "dog-bears", literally "Half Dog" (Greek
: "hemi-kuôn"), bear-like carnivora
n living in Europe
, North America
, Africa
, and Asia
during the Oligocene
through Miocene
epochs 33.9—5.3 Ma, existing for approximately .
Hemicyonids are widely accepted to have been hypercarnivorous
and highly predaceous
. They walked on their toes, i.e., they were digitigrade
, with long metapodials
. In these respects they were similar to dogs, and unlike modern bears, which are plantigrade
with short metapodials. This suggests that hemicyonids must have been active hunters and good runners, and presumably hunted on the plains, possibly in packs. Note that the hemicyonids are easily confused with the related and often similar-looking "bear-dogs" of the family Amphicyonidae.
, and Dinocyon
). The earliest known occurrence of the hemicyonids is in Europe from 22.8–20 Ma of Spain: Phoberocyon hispanicus from Loranca and Zaragocyon daamsi from Cetina de Aragon.
existing from ~33.9—20 Ma. In North America specimens have been uncovered which date from ~21.6—21.2 Ma. Phoberocyon johnhenryi is yet another old specimen from the large Thomas Farm Site
, Florida
, (~19–18 Ma). This species of the genus Phoberocyon
is confirmed by diagnostic features of the lower dentition
: posterior accessory cusps in lower premolar
s and paraconid in m2, and it is a more derived species than Phoberocyon hispanicus in that it is larger and has diastemata between the premolar
s.
All the American hemicyonids are more advanced in character, and are assigned to genus Plithocyon
. They are known from the Barstovian
of California, New Mexico, Nebraska, Wyoming and the Love Bone Bed Local Fauna in Florida. In Asia, the earliest hemicyonid is Phoberocyon youngi from Shanwang, Shandong (16 Ma) and is very close to the North American Phoberocyon johnhenry. The latest occurrence in China is from the Tung-Gur Formation, Nei-Mongol (13 Ma). Dispersal probably occurred from Europe to North America prior to 19 Ma and the American Plithocyon is probably a descendant of the Phoberocyon.
The genus Agriotherium
is sometimes considered a member of Hemicyonidae due to the presence of many similar hemicyonine characters (unelongated molars, premasseteric fossa, etc.) and this strongly substantiates its closer affinity with hemicyonines rather than with ursines. Agriotherium has its longest history in Asia. The most primitive and earliest form is from a Hipparion fauna in Hezheng, Gansu, 9 Ma. All other forms of Agriotherium occurred in the Pliocene (5.3 to 2 Ma) in Eurasia and Africa, leaving a hiatus in the record between 9 and 5.3 Ma. In North America, Agriotherium appeared suddenly around 7 Ma and probably emigrated from Eurasia. Agriotherium fossils have been found at Coffee Ranch, Texas (6.6 Ma); Guymon Local Fauna, Oklahoma; Mount Eden Local Fauna, California; and Old Cabin Quarry, Quiburis Formation (late Hemphillian), Arizona. The occurrence of Agriotherium in North and Central America is thus limited to the later half of the Hemphillian (7–5 Ma).
Hemicyonidae fossil evidence may also have been found in the Gaillard Cut Local Fauna, former Panama Canal Zone
, Republic of Panama, but it is indeterminant with Amphicyonidae. Despite its close proximity to South America, given the geological context, the Gaillard Cut Local Fauna are distinctly North American fauna and the age of this assemblage is dated between 19.5 and 14 Ma.
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
: "hemi-kuôn"), bear-like carnivora
Carnivora
The diverse order Carnivora |Latin]] carō "flesh", + vorāre "to devour") includes over 260 species of placental mammals. Its members are formally referred to as carnivorans, while the word "carnivore" can refer to any meat-eating animal...
n living in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, and Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
during the Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
through Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
epochs 33.9—5.3 Ma, existing for approximately .
Morphology
They were about 1.50 m (5 ft) long, 70 centimetres (28 inches) tall, with somewhat tiger-like proportions and dog-like teeth, weighing as much as 69 kg (152.1 lb).Hemicyonids are widely accepted to have been hypercarnivorous
Hypercarnivore
A hypercarnivore is an animal which has a diet that is more than 70% meat, with the balance consisting of non-animal foods such as fungi, fruits or other plant material. Some examples include the big cats, dolphins, eagles, snakes, marlin, most sharks, and such invertebrates as octopuses and sea...
and highly predaceous
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
. They walked on their toes, i.e., they were digitigrade
Digitigrade
A digitigrade is an animal that stands or walks on its digits, or toes. Digitigrades include walking birds , cats, dogs, and many other mammals, but not plantigrades or unguligrades...
, with long metapodials
Metatarsus
The metatarsus or metatarsal bones are a group of five long bones in the foot located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the medial side : the first, second, third, fourth, and fifth...
. In these respects they were similar to dogs, and unlike modern bears, which are plantigrade
Plantigrade
right|151px|thumb|Human skeleton, showing plantigrade habitIn terrestrial animals, plantigrade locomotion means walking with the podials and metatarsals flat on the ground. It is one of three forms of locomotion adopted by mammals...
with short metapodials. This suggests that hemicyonids must have been active hunters and good runners, and presumably hunted on the plains, possibly in packs. Note that the hemicyonids are easily confused with the related and often similar-looking "bear-dogs" of the family Amphicyonidae.
Taxonomy
Classification of the hemicyonids has become complicated. Some classifications subdivide the Hemicyonidae into two subfamilies: Phoberocyoninae (including Phoberocyon and Plithocyon) and Hemicyoninae (including Zaragocyon, HemicyonHemicyon
Hemicyon the so-called "dog-bear," literally "Half Dog" , is an extinct genus of the family Hemicyonidae, which probably originated in Eurasia but was found in Europe, Asia and North America during the Miocene epoch , existing for approximately .-Morphology:Hemicyon was about long, and tall, with...
, and Dinocyon
Dinocyon
Dinocyon is an extinct genus of bear-like hemicyonid carnivore of the Miocene epoch, endemic to Europe living from around 20.3—5.3 Ma, existing for approximately .-Taxonomy:...
). The earliest known occurrence of the hemicyonids is in Europe from 22.8–20 Ma of Spain: Phoberocyon hispanicus from Loranca and Zaragocyon daamsi from Cetina de Aragon.
Genus identification
Hemicyonids lived continuously in Europe with the oldest known being CephalogaleCephalogale
Cephalogale is an extinct genus of bear-like hemicyonid carnivore of the late Oligocene through Miocene epochs, endemic to North America and Europe living from around 33.9—20 Ma, existing for approximately ....
existing from ~33.9—20 Ma. In North America specimens have been uncovered which date from ~21.6—21.2 Ma. Phoberocyon johnhenryi is yet another old specimen from the large Thomas Farm Site
Thomas Farm Site
The Thomas Farm site is an Early Miocene, Hemingfordian assemblage of vertebrate fossils located in Gilchrist County, northern Florida.The Thomas Farm site is one of the richest terrestrial deposits of Miocene vertebrates in the 18 Ma range found in eastern North America according to the Florida...
, Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
, (~19–18 Ma). This species of the genus Phoberocyon
Phoberocyon
Phoberocyon is a large extinct genus of carnivorous Ursidae, subfamily Hemicyonidae, endemic to what would be North America during the Miocene living from 20.6—16.3 mya, existing for approximately .-Taxonomy:Phoberocyon was named by Ginsburg...
is confirmed by diagnostic features of the lower dentition
Dentition
Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, the characteristic arrangement, kind, and number of teeth in a given species at a given age...
: posterior accessory cusps in lower premolar
Premolar
The premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered as a 'transitional tooth' during chewing, or...
s and paraconid in m2, and it is a more derived species than Phoberocyon hispanicus in that it is larger and has diastemata between the premolar
Premolar
The premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered as a 'transitional tooth' during chewing, or...
s.
All the American hemicyonids are more advanced in character, and are assigned to genus Plithocyon
Plithocyon
Plithocyon is an extinct genus of bear-like hemicyonid carnivore of the Miocene epoch, endemic to North America and Europe living from ~15.97—7.25 Ma, existing for approximately .-Taxonomy:Plithocyon was named by Ginsburg...
. They are known from the Barstovian
Barstovian
The Barstovian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 16,300,000 to 13,600,000 years BP, a period of . It is usually considered to overlap the Langhian and Serravallian...
of California, New Mexico, Nebraska, Wyoming and the Love Bone Bed Local Fauna in Florida. In Asia, the earliest hemicyonid is Phoberocyon youngi from Shanwang, Shandong (16 Ma) and is very close to the North American Phoberocyon johnhenry. The latest occurrence in China is from the Tung-Gur Formation, Nei-Mongol (13 Ma). Dispersal probably occurred from Europe to North America prior to 19 Ma and the American Plithocyon is probably a descendant of the Phoberocyon.
The genus Agriotherium
Agriotherium
Agriotherium is an extinct genus of Ursidae of the Miocene through Pleistocene epochs, endemic to North America, Europe, Africa, and Asia living from ~13.6–2.5 Ma, existing for approximately .-Taxonomy:...
is sometimes considered a member of Hemicyonidae due to the presence of many similar hemicyonine characters (unelongated molars, premasseteric fossa, etc.) and this strongly substantiates its closer affinity with hemicyonines rather than with ursines. Agriotherium has its longest history in Asia. The most primitive and earliest form is from a Hipparion fauna in Hezheng, Gansu, 9 Ma. All other forms of Agriotherium occurred in the Pliocene (5.3 to 2 Ma) in Eurasia and Africa, leaving a hiatus in the record between 9 and 5.3 Ma. In North America, Agriotherium appeared suddenly around 7 Ma and probably emigrated from Eurasia. Agriotherium fossils have been found at Coffee Ranch, Texas (6.6 Ma); Guymon Local Fauna, Oklahoma; Mount Eden Local Fauna, California; and Old Cabin Quarry, Quiburis Formation (late Hemphillian), Arizona. The occurrence of Agriotherium in North and Central America is thus limited to the later half of the Hemphillian (7–5 Ma).
Hemicyonidae fossil evidence may also have been found in the Gaillard Cut Local Fauna, former Panama Canal Zone
Panama Canal Zone
The Panama Canal Zone was a unorganized U.S. territory located within the Republic of Panama, consisting of the Panama Canal and an area generally extending 5 miles on each side of the centerline, but excluding Panama City and Colón, which otherwise would have been partly within the limits of...
, Republic of Panama, but it is indeterminant with Amphicyonidae. Despite its close proximity to South America, given the geological context, the Gaillard Cut Local Fauna are distinctly North American fauna and the age of this assemblage is dated between 19.5 and 14 Ma.