canid Canidae (; from Latin, '' canis'', " dog") is a biological family of dog-like carnivorans, colloquially referred to as dogs, and constitutes a clade. A member of this family is also called a canid (). There are three subfamilies found withi ...

Caninae The Caninae, known as canines, are one of three subfamilies found within the canid family. The other two canid subfamilies are the extinct Borophaginae and Hesperocyoninae. The Caninae includes all living canids and their most recent fossil rel ...

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Hesperocyoninae. The earliest and most primitive borophagine is the genus ''

Archaeocyon ''Archaeocyon'' ("ancient dog") is an extinct genus of the Borophaginae subfamily of canids native to North America. It lived during the Oligocene epoch 32-24 Ma., existing for approximately . Species of ''Archaeocyon'' are among the earliest k ...

'', which is a small fox-sized animal mostly found in the fossil beds in western North America. The borophagines soon diversified into several major groups. They evolved to become considerably larger than their predecessors, and filled a wide range of niches in late Cenozoic North America, from small omnivores to powerful, bear-sized carnivores, such as '' Epicyon''.

Species

There are 66 identified borophagine species, including 18 new ones that range from the

Orellan The Orellan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), 34-32 million years ago. It is usually considered to fall within the Early Oligocene. ...

to Blancan ages. A

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

analysis of the species was conducted using

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...

methods, with Hesperocyoninae as an archaic group of canids, as the outgroup. Aside from some transitional forms, Borophaginae can be organized into four major clades:

Phlaocyonini Phlaocyonini is an extinct clade or tribe of hypocarnivorous borophagines (bone-crushing dogs). They were endemic to North America and from the Oligocene epoch (Whitneyan stage) to the Miocene ( Early Barstovian) living ~33.3–5.3 Ma, exi ...

,

Cynarctina Cynarctina is an extinct clade of the Borophaginae subfamily of canids native to North America. They lived from the Early to Middle Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). Th ...

, Aelurodontina, and Borophagina (all erected as new tribes or subtribes). The Borophaginae begins with a group of small fox-sized genera, such as ''

Archaeocyon ''Archaeocyon'' ("ancient dog") is an extinct genus of the Borophaginae subfamily of canids native to North America. It lived during the Oligocene epoch 32-24 Ma., existing for approximately . Species of ''Archaeocyon'' are among the earliest k ...

'', '' Oxetocyon'', '' Otarocyon'', and ''

Rhizocyon ''Rhizocyon'' ("root dog") is an early member of the subfamily Borophaginae, an extinct subgroup of canids that were endemic to western North America during the Oligocene epoch, living from ~31—24.5 Ma., existing for approximately . ''Rhizocy ...

'', in the

Orellan The Orellan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), 34-32 million years ago. It is usually considered to fall within the Early Oligocene. ...

through early

Arikareean The Arikareean North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 30,600,000 to 20,800,000 years BP, a period of . It is usuall ...

stages. These canids reached their maximum diversity of species around 28 million years ago. Often generically referred to as "bone-crushing dogs" for their powerful

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, t ...

and jaws, and hyena-like features (although their dentition was more primitive than that of hyenas), their

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s are abundant and widespread; in all likelihood, they were probably one of the top predators of their

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

s. Their good fossil record has also allowed a detailed reconstruction of their

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spe ...

, showing that the group was highly diverse in its heyday. All Borophaginae had a small fifth toe on their rear feet (similar to the toes that bear dew claws on the front feet), where as all modern

Caninae The Caninae, known as canines, are one of three subfamilies found within the canid family. The other two canid subfamilies are the extinct Borophaginae and Hesperocyoninae. The Caninae includes all living canids and their most recent fossil rel ...

have only four toes normally. Noteworthy genera in this group are '' Aelurodon'', '' Epicyon'', and ''

Borophagus ''Borophagus'' ("gluttonous eater") is an extinct genus of the subfamily Borophaginae, a group of canids endemic to North America from the Middle Miocene epoch through the Early Pleistocene epoch 12—1.8 Mya. Evolution ''Borophagus'', like o ...

'' (='' Osteoborus''). According to Xiaoming Wang, the Borophaginae played broad ecological roles that are performed by at least three living carnivoran families, Canidae (which they were a part of), Hyaenidae, and Procyonidae. Wang Borophagine Construct

Classification

Borophagine taxonomy, following Wang et al. (million years=in existence) *Family Canidae **Subfamily †Borophaginae ***†''

Archaeocyon ''Archaeocyon'' ("ancient dog") is an extinct genus of the Borophaginae subfamily of canids native to North America. It lived during the Oligocene epoch 32-24 Ma., existing for approximately . Species of ''Archaeocyon'' are among the earliest k ...

'' 33—26 Ma, existing ***†'' Oxetocyon'' 33—28 Ma, existing ***†'' Otarocyon'' 34—30 Ma, existing ***†''

Rhizocyon ''Rhizocyon'' ("root dog") is an early member of the subfamily Borophaginae, an extinct subgroup of canids that were endemic to western North America during the Oligocene epoch, living from ~31—24.5 Ma., existing for approximately . ''Rhizocy ...

'' 33—26 Ma, existing ***Tribe †

Phlaocyonini Phlaocyonini is an extinct clade or tribe of hypocarnivorous borophagines (bone-crushing dogs). They were endemic to North America and from the Oligocene epoch (Whitneyan stage) to the Miocene ( Early Barstovian) living ~33.3–5.3 Ma, exi ...

33—13 Ma, existing ****†''

Cynarctoides ''Cynarctoides'' is an extinct genus of the Borophaginae subfamily of canids native to North America. It lived from the Early Oligocene to the Middle Miocene, 33.3—13.6 Mya, existing for approximately . Seven species are currently recognised, ...

'' 30—18 Ma, existing ****†''

Phlaocyon ''Phlaocyon'' (from Greek ''phlao'', "eat greedily" and ''cyon'', "dog") is an extinct genus of the Borophaginae subfamily of canids native to North America. It lives from the Early Oligocene to the Early Miocene epoch 33.3–16.3 Annum, Mya, exi ...

'' 30—19 Ma, ***Tribe † Borophagini 30—3 Ma, existing ****†'' Cormocyon'' 30—20 Ma, existing ****†'' Desmocyon'' 25—16 Ma, existing ****†'' Metatomarctus'' 19—16 Ma, existing ****†'' Euoplocyon'' 18—16 Ma, existing ****†'' Psalidocyon'' 16—13 Ma, existing ****†'' Microtomarctus'' 21—13 Ma, existing ****†''

Protomarctus ''Protomarctus'' is an extinct monotypic taxon, monospecific genus of the Borophaginae subfamily of canids native to North America. They lived during the Middle Miocene 16.0—13.6 Mya (unit), Mya, existing for approximately . It was an intermed ...

'' 20—16 Ma, existing ****†'' Tephrocyon'' 16—14 Ma, existing ****Subtribe †

Cynarctina Cynarctina is an extinct clade of the Borophaginae subfamily of canids native to North America. They lived from the Early to Middle Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). Th ...

20—10 Ma, existing *****†'' Paracynarctus'' 19—16 Ma, existing *****†''

Cynarctus ''Cynarctus'' is an extinct genus of the Borophaginae subfamily of canids native to North America. The genus was first founded by W. D. Matthew in 1901, based from a pair of lower jaws, ''Cynarctus saxitilis,'' found in the Pawnee Creek Beds of ...

'' 16—12 Ma, existing ****Subtribe † Aelurodontina 20—5 Ma, existing *****†'' Tomarctus'' 23—16 Ma, existing *****†'' Aelurodon'' 16—12 Ma, existing ****Subtribe † Borophagina *****†''

Paratomarctus ''Paratomarctus'' is an extinct monospecific genus of the Borophaginae subfamily of canids native to North America. It lived from the Middle to Late Miocene, 16.3—5.3 mya, existing for approximately . It was about the size of a coyote, and was ...

'' 16—5 Ma, existing *****†''

Carpocyon ''Carpocyon'' is an extinct genus of the Borophaginae subfamily of canids native to North America. It lived from the Middle to the Late Miocene, 13.6 to 5.3 Ma Mya, existing for approximately . The four species in the genus varied in size, with ...

'' 16—5 Ma, existing *****†''

Protepicyon ''Protepicyon'' is an extinct monospecific genus of the Borophaginae subfamily of canids native to North America. It lived during the Barstovian stage of the Middle Miocene 16.0—13.6 mya. One of the top predators of its time, it was the probab ...

'' 16—12 Ma, existing *****†'' Epicyon'' 12—10 Ma, existing *****†''

Borophagus ''Borophagus'' ("gluttonous eater") is an extinct genus of the subfamily Borophaginae, a group of canids endemic to North America from the Middle Miocene epoch through the Early Pleistocene epoch 12—1.8 Mya. Evolution ''Borophagus'', like o ...

'' (='' Osteoborus'') 12—5 Ma, existing Cladogram showing borophagine interrelationships, following Wang et al., figure 141:

Extinction

According to an analysis of the fossil record of North American fossil carnivorans, the decline of borophagines from a diversity of about 30 species 15 million years ago to extinction was largely driven by competition with

felid Felidae () is the family of mammals in the order Carnivora colloquially referred to as cats, and constitutes a clade. A member of this family is also called a felid (). The term "cat" refers both to felids in general and specifically to the dom ...

s and canines. Felids invaded the continent from Eurasia about 20 million years ago and were better ambush predators, in part due to their retractable claws. Climate change, which led to the replacement of North American forests with grasslands, may also have been a factor; borophagines were less suited to running down prey than canines. Although these specific species developed powerful limbs that are capable of cracking bones in vicious pounce attacks, other carnivorous species that rely on quick ambush for catching prey were likely more successful than the slower Borophaginae. Martín-Serra, A., Figueirido, B. & Palmqvist, P
In the Pursuit of the Predatory Behavior of Borophagines (Mammalia, Carnivora, Canidae): Inferences from Forelimb Morphology
''J. Mammal. Evol.'' 23, 237–249 (2016)

Species

Classification

Extinction

References

Further reading