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Epicyon
Temporal range: Late Miocene to Early Pliocene (Clarendonian to Hemphillian), 12–5 Ma
Mounted E. haydeni skeleton
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Canidae
Subfamily: †Borophaginae
Tribe: †Borophagini
Subtribe: †Borophagina
Genus: †Epicyon
Leidy, 1858
Type species
†Epicyon haydeni
Leidy, 1858
Other Species[1]
  • †E. aelurodontoides
  • †E. saevus

Epicyon ("more than a dog") is a large, extinct, canid genus of the subfamily Borophaginae ("bone-crushing dogs"), native to North America. Epicyon existed for about 7 million years from the early Clarendonian age of the Late Miocene to the late Hemphillian age of the Early Pliocene.[2][1] E. haydeni is the largest known canid of all time, with the type species reaching 2.4 m (7.9 ft) in length, 90 cm (35 in) in shoulder height and approximately 100–125 kg (220–276 lb) in body mass.[3][4][5] The largest known humerus specimen belonged to an individual weighing up to 170 kg (370 lb).[6]

Taxonomy

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Epicyon was first named by Joseph Leidy in 1858 as a subgenus of Canis. It was also mentioned as belonging to the Aelurodontina by Matthew and Stirton in 1930. Later studies indicates that it was not a species of Canis, but a borophagine.

Epicyon haydeni, the type species, existed from 10-5 million years ago. It is synonymous with Aelurodon aphobus, Osteoborus ricardoensis, Osteoborus validus, and Tephrocyon mortifer, and was named by Joseph Leidy as a subgenus. It was recombined as Aelurodon haydeni by Scott and Osborn in 1890. Further study by Matthew in 1899, Matthew and Gidley in 1904, VanderHoof and Gregory in 1940, McGrew in 1944, Bennett in 1979, (1979) and Becker (1980). It again was recombined as Epicyon haydeni by Baskin in 1980, Voorhies in 1990, (1990), Baskin (1998), Wang et al. in 1999.

Mandible of Epicyon saevus

Epicyon saevus existed from 12 to 7 million years ago. It is synonymous with Aelurodon inflatus and was named by Joseph Leidy in 1858 or 1859. In the late 1880s-early 1900s, Scott, Matthew, Cope and Matthew, Troxell recombined the animal as Aelurodon saevus. It was recombined as Epicyon saevus by Baskin in 1980, Munthe in 1989, Voorhies in 1990, and Wang et al. 1999.

Epicyon aelurodontoides existed from 9 to 7 million years ago and was named by X. Wang and others in 1999. This species was found south of the Young Brothers Ranch, Kansas.[1]

Description

[edit]
Restoration

Epicyon had a massive head and powerful jaws that were well adapted for bone-crushing, with enlarged fourth premolars like some hyenas, giving its skull a lion-like shape rather than having a skull similar in shape to that of a wolf; the adaptation would have allowed Epicyon to scavenge as well as hunt, giving it access to the nutritious marrow other contemporary carnivores could not access.[4]

E. haydeni was the largest known species of canid; it is estimated to have had a body length of 2.4 m (7.9 ft), a shoulder height of 90 cm (35 in) and a body mass of approximately 100–125 kg (220–276 lb),[3][4][5] with the largest known specimen weighing up to 170 kg (370 lb).[6]

E. saevus is estimated to have a shoulder height is up to 56 cm (22 in) and body mass up to 66.5 kg (147 lb).[5]

Paleobiology

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Predatory behavior

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The molars of E. haydeni were grindstone-like teeth that allow for a canid diet that includes both meat and plant and insects. The proportional size of an animal's molars is a great measure of the nutritional diversity of its diet.[7] Based on fossilized feces and its robust teeth and jaw muscles it is believed to have consumed large amounts of bone and share a similar digestive tract to modern day hyenas due to their ability to break down bones.[7][8] The deadly bite of a E. haydeni was delivered by the canine teeth, which are placed near the front of the upper and lower jaws, the shortening of the jaws can be an effective method for getting the canines closer to the mandibular condyle, thereby increasing the biting force.[7]

The small clavicle, flexible back, and digitigrade posture of E. haydeni are all postcranial features shared with other canids and are likely adaptations designed to increase the animal's stride length. Examinations of the limb proportions and toughness of the skeleton suggests that E. haydeni was less cursorial than hyenas or modern wolves but more cursorial than other borophagine species like Aelurodon.[9][10] Unlike hyenas, E. haydeni must have used their rearmost lower premolar (p4) and upper carnassial (P4) to crack large bones (ibid.)[clarification needed]. Smaller bones and bone fragments were likely crushed with the carnassials and post-carnassial molars just as in extant canids.[11] Due to its larger size and less gracile skeleton, E. haydeni was less cursorial and unable to run as long a distance as E. saevus, instead it relied on bursts of speed.[9]

Predatory behavior for Epicyon heavily depends on the methods used. Schwab et al. (2019) found E. haydeni likely practiced pounce predation based on the anatomy of its bony labyrinth,[12] while Figueirido et al. (2015) analysis on elbow morphology suggests E. haydeni was more of an ambush hunter.[13] On the other hand, Martín-Serra et al. (2016) found E. haydeni practiced pursuit or pounce-pursuit predation, while E. saevus practiced pounce-pursuit predation based on forelimb analysis. Their analysis also suggests borophagines predatory behavior was not equivalent to any living species.[14]

Social behavior

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Whether or not Epicyon was gregarious or solitary is unclear. Tomida and colleagues believed E. haydeni was gregarious as it was very prevalent in the fossil record, and was one of the most common carnivores in North America at the time.[15] Valkenburgh and colleagues also argued gregariousness because of their adaptation to hunting large prey and canids not being able to grapple large prey like felids can.[11]

This interpretation was called into question by Ki Anderson, as craniodental and elbow joint morphology of borophaginae resembled that of pantherinae instead of recent canids, arguing that the latter are unsuitable modern analogues and not a reliable indicator. The author of the paper admitted that this is not enough to refute or support pack hunting among borophaginae as lions are capable of grappling prey, but they still hunt in social groups, showing the complexity of social behavior in carnivorans.[5]

Paleoecology

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Skull and mandible casts of E. saevus, Florida Museum of Natural History

Fossil specimens range from Florida to California and have been found in Nebraska, Montana, Kansas, Texas, New Mexico, Colorado, Oklahoma, Idaho, Oregon, Arizona within the United States, as well as in Alberta, Canada.[15][16]

In Coffee Ranch in Texas, Epicyon shared territory with the bear Huracan, machairodont feline Amphimachairodus coloradensis, and fellow canid Borophagus. All of these animals were potential competitors that would have occasionally conflicted with Epicyon for food and territory. Prey for Epicyon included herbivores such as the camel Aepycamelus, the pronghorn Cosoryx, horses such as Neohipparion and Nannippus, the peccary Prosthennops, and the rhinoceroses such as Teleoceras, all of which could provide a suitable meal through hunting or scavenging.[17][18]

Epicyon was also found in Love Bone Beds deposits (of Clarendonian Age). This locality had a mixture of grassland, riverine forest, and marshes, in which Epicyon would have shared territory with herbivorous animals include rhinoceroses like Teleoceras and Aphelops, the protoceratid Synthetoceras, the camel Aepycamelus, horses like Neohipparion and Nannippus, the proboscidean Gomphotherium, and carnivores like the nimravid Barbourofelis, the machairodont Nimravides, borophaginae canid Borophagus, and mustelids Leptarctus and Sthenictis.[19][20][21]

Epicyon was one of the last of the borophagines, and shared its North American habitat with several other canids, including:

References

[edit]

General references

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Epicyon

View on Grokipedia
from Grokipedia
Epicyon is an extinct genus of large canids in the subfamily Borophaginae, commonly known as "bone-crushing dogs," that lived in North America during the late Miocene epoch, from the Clarendonian to the Hemphillian North American land mammal ages (approximately 13 to 5 million years ago). The genus is characterized by its hypercarnivorous adaptations, including robust skulls, powerful jaws, and specialized dentition for crushing bones, similar to those of modern hyenas. Fossils of Epicyon have been discovered across a broad geographic range in the United States, from Florida in the east to California in the west, with notable sites including Nebraska (the type locality), Texas, and Montana. The most prominent species, Epicyon haydeni, represents the pinnacle of borophagine size and is the largest known canid in history, reaching dimensions comparable to those of a , with estimates suggesting lengths up to 2.4 meters and weights of 100–170 kilograms. This species featured a short rostrum, dome-shaped , and enlarged teeth, adaptations that supported a durophagous (bone-cracking) diet primarily consisting of large carcasses. Named by paleontologist Joseph Leidy in 1858 after Ferdinand V. Hayden, E. haydeni exemplifies the evolutionary trends toward increased body size and craniodental robusticity within , though the genus as a whole includes approximately five valid species that varied in size and temporal distribution. Epicyon played a key ecological role as a top predator and in ecosystems, coexisting with proboscideans, equids, and other before the decline of borophagines near the end of the . Its is linked to broader faunal turnover, possibly influenced by climatic changes and competition from emerging canids and felids. Well-preserved specimens, such as partial skulls and mandibles from sites like the Love Bone Bed in , provide insights into its morphology and , revealing heavy tooth wear indicative of a tough, bone-inclusive diet.

Discovery and taxonomy

Discovery history

The genus Epicyon was first described by paleontologist Joseph Leidy in 1858, based on isolated teeth collected from the Miocene deposits along the valley in . These initial specimens, including upper and lower molars, indicated a large carnivorous and were named as a subgenus of Canis, with the Epicyon haydeni honoring Ferdinand V. Hayden, a involved in early western surveys. Another key Nebraska locality is the Snake Creek Formation in Sioux County, which has produced numerous Epicyon haydeni cranial and postcranial elements, contributing to understanding its distribution in the Great Plains during the late Miocene. In Florida, the Love Bone Bed (University of Florida locality AL001) in Alachua County represents a significant eastern extension of Epicyon's known range, with fossils recovered from Hemphillian (late Miocene) fluvial deposits indicating the genus reached the southeastern United States. Excavations at this site from 1974 to 1981 uncovered over 20,000 identifiable bone fragments, including isolated Epicyon haydeni teeth and postcranial elements showing signs of transport and weathering, preserved in a channel-fill lag with a bias toward larger vertebrates. Key 20th-century efforts advanced Epicyon research through targeted expeditions, notably the American Museum of Natural History's Thomson Expeditions to the Snake Creek quarries in from 1921 to 1927, led by Albert Thomson, which collected hundreds of Miocene fossils including multiple Epicyon specimens that informed early reconstructions of its and . These field seasons, spanning seven years, focused on systematic quarrying in the Valentine and Snake Creek formations, yielding well-preserved material now housed in the AMNH collections and supporting studies on borophagine canid diversity.

Etymology and classification

The genus Epicyon was named by Joseph Leidy in 1858 as a subgenus of Canis, based on isolated teeth from the Miocene deposits of the valley in . The etymology derives from the Greek "epi," meaning "upon" or "near," combined with "kyon," meaning "dog," reflecting its robust, dog-like build that exceeded typical canine proportions in size and form. Initially classified within the living genus Canis, Epicyon was elevated to genus rank and assigned to the newly established Borophaginae by W.D. Matthew in 1909, recognizing its specialized bone-crushing adaptations distinct from modern . This , comprising hypercarnivorous North American often termed "bone-crushing dogs," highlights Epicyon's evolutionary divergence toward hyena-like feeding mechanics. Cladistic analyses confirm Epicyon as a member of , positioned within the subtribe Borophagina as the sister to the Aelurodontina , which includes Aelurodon; this placement underscores its late radiation as one of the largest and most specialized borophagines. Systematic revisions have resolved several junior synonyms for Epicyon haydeni, the , including Osteoborus ricardoensis and Osteoborus validus, based on shared cranial and dental features indicating conspecificity across Hemphillian localities.

Valid species

The genus Epicyon includes three valid recognized in modern , distinguished primarily by differences in size, cranial proportions, and dental morphology. These span the middle to , with delimitation based on discrete traits such as mandibular robusticity and facial elongation rather than continuous size gradients alone, though ontogenetic and sexual variation complicates some boundaries. Epicyon haydeni, the , is the largest and most derived member of the , known from numerous complete skeletons that provide a robust basis for anatomical reconstruction. Named by Joseph Leidy in 1858 from material collected in , it is characterized by a robust , shortened rostrum, pronounced frontal doming, and specialized bone-crushing dentition including enlarged and a broad talonid basin on the lower first molar. This occurs in late Clarendonian to early Hemphillian strata (approximately 12–5 million years ago), with type locality in the late Clarendonian of and additional records from early Hemphillian sites in , such as Haile 19A. Epicyon saevus, a smaller contemporaneous species, is distinguished by a more gracile and shallower mandibular ramus, longer facial region, less domed forehead, and relatively larger compared to E. haydeni, representing about 16–23% smaller overall size. Originally described by Leidy in 1858 from material but with its range spanning the late Barstovian to early Clarendonian (approximately 16–9 million years ago), it is documented from sites like the Love Bone Bed in . Dental proportions show less emphasis on hypercarnivory, with subtler cusp shearing adaptations. Some older referrals, such as to Aelurodon inflatus, have been synonymized under E. saevus based on shared cranial metrics. Both E. haydeni and E. saevus are documented from the Love Bone Bed, suggesting in late Clarendonian . Epicyon aelurodontoides, named by Wang et al. in 1999, represents a transitional form with intermediate features, including a gracile similar to E. saevus but with cranial proportions bridging earlier borophagines. Known primarily from cranial material, it exhibits elongated auditory bullae and dental traits indicative of evolving durophagy, such as reinforced molars. This is restricted to middle to horizons (approximately 10–7 million years ago), with the type locality south of the Young Brothers Ranch in . Taxonomic debates have considered potential synonymy with smaller E. haydeni variants, but discrete mandibular and zygomatic differences support its validity, emphasizing trait-based rather than size-only delimitation.

Physical characteristics

Size and build

Epicyon species exhibited a range of body sizes, with E. haydeni representing the largest known member of the genus and subfamily . This species is estimated to have reached a body length of up to 2.4 meters, a shoulder height of 90 centimeters, and a body mass between 100 and 170 kilograms, making it substantially larger than modern gray wolves (Canis lupus), which typically measure 1.2–1.6 meters in length, 60–90 centimeters at the shoulder, and 30–80 kilograms in mass. Smaller species, such as E. saevus, scaled down proportionally, with estimated masses around 50–70 kilograms and corresponding reductions in linear dimensions (shoulder height up to 56 cm), reflecting evolutionary trends toward in later borophagines. These estimates derive from skeletal measurements, including length scaled against extant analogs like the (Crocuta crocuta), highlighting Epicyon's position as the largest canid ever documented. The postcranial skeleton of Epicyon featured robust limb bones suited for stability and with prey, with limited adaptations for locomotion compared to modern wolves, including reduced mobility that supported movement in varied habitats rather than specialized efficient pursuit over open terrain. Forelimbs displayed moderate flexibility, with a shallow humeral trochlea permitting some supination and rotation outside the parasagittal plane, which would have aided maneuverability in varied habitats, including forested areas. This combination of robustness and limited flexibility distinguished Epicyon from more specialized canids, allowing with prey while maintaining stability during chases. Overall body proportions included a massive supported by a sturdy vertebral column, contributing to the animal's powerful build for tackling large prey, and a relatively short that provided balance without excessive drag during movement. Across , these traits scaled with size, with E. haydeni exemplifying the most exaggerated form, its elongated postcranial elements underscoring adaptations for a predatory lifestyle in North American ecosystems.

Cranial and dental features

The of Epicyon was notably robust, featuring a prominent that provided extensive attachment sites for the temporalis and masseter muscles, facilitating powerful closure. In E. haydeni, the largest species, basilar lengths measured 28–32 cm, contributing to its overall massive cranial profile adapted for durophagous feeding. The was prominently domed, enhancing structural during high-stress biting by dissipating tensile forces rostro-ventrally across the facial region. Dentition in Epicyon reflected its bone-crushing specialization, with hypertrophied (P4 and m1) and enlarged fourth premolars resembling those of , enabling efficient shearing and fracturing of . Unlike modern canids, the lower first molar retained a well-developed talonid basin for grinding, while incisors were enlarged to secure large prey, prioritizing posterior teeth for processing tough food items including . These features supported a hypercarnivorous yet durophagous diet, allowing complete carcass utilization. Jaw mechanics in Epicyon emphasized temporalis-driven , which optimized production while minimizing cranial deformation at the region, as revealed by finite element analyses. model simulations indicated that derived species like E. haydeni generated relatively high compared to basal forms, with enhanced efficiency in stress distribution for sustained bone-cracking. Intraspecific variations highlighted evolutionary progression within the ; E. saevus, a basal , exhibited less robust and cranial architecture, with lower bite force efficiency and reduced specialization for durophagy relative to the more derived E. haydeni.

Behavior and paleobiology

Hunting strategies

Epicyon employed a pounce-based , characterized by short bursts of agile movement to and overpower prey, as inferred from morphometric analysis of its , which indicate enhanced sensitivity to rapid head rotations suitable for close-range attacks rather than prolonged pursuits. This style aligns with its robust limb proportions, featuring strong forelimbs adapted for and subduing victims, contrasting with the builds of pursuit-oriented canids. The genus specialized in bone-crushing, facilitated by cranial adaptations such as reinforced frontal bones and enlarged teeth that distributed biting stresses evenly during durophagous feeding, allowing it to access marrow from large carcasses. Heavy wear on teeth of Epicyon haydeni further supports routine consumption of hard material, enabling efficient exploitation of prey remains that softer-jawed carnivores could not utilize. Prey preferences centered on medium- to large-sized ungulates, such as the camelid , whose body mass (approximately 400–700 kg) matched Epicyon's predatory capabilities, as evidenced by their in faunas like those from . associations suggest Epicyon targeted these herbivores in open environments, with predatory or scavenging interactions inferred from , though direct attribution remains challenging due to taphonomic overlap with other carnivorans. Compared to earlier borophagine relatives like Aelurodon, Epicyon represents a pronounced shift toward hypercarnivory, marked by reduced or lost grinding molars and enhanced shearing that prioritized and over omnivorous , allowing it to dominate as a top predator in its . This evolutionary trend, initiated in mid-Miocene forms like Protepicyon, underscores Epicyon's departure from the more generalized diets of basal borophagines toward specialized predation.

Social structure

The social structure of Epicyon remains a subject of ongoing debate among paleontologists, with evidence pointing toward gregarious behavior rather than strict solitude, though direct proof such as communal dens is absent. assemblages, particularly from the Love Bone Bed in —a locality yielding thousands of remains—include multiple specimens of E. haydeni and E. saevus, suggesting either or mass mortality events that concentrated individuals. This site's prolific carnivoran record, including at least two Epicyon species represented by numerous cranial and postcranial elements, indicates high local population densities compatible with social aggregation, akin to modern canid packs. Morphological features of Epicyon, such as its robust skeletal build with deep jaws, large teeth, and moderate forelimb supination for prey restraint, support the potential for cooperative pursuits of large herbivores exceeding individual body mass. These traits, combined with the genus's hypercarnivorous and prevalence across North American faunas, imply that pack hunting would have been more effective than solitary ambushes, as Epicyon's blunt claws limited capabilities against struggling prey. However, earlier interpretations based on braincase morphology suggested limited compared to modern wolves, though this has been contested as insufficient to rule out . Recent phylogenetic analyses (as of 2023) continue to explore pack hunting potential through comparative morphology. Size variation between co-occurring Epicyon species, up to 16–23% and exceeding the typical ~5% intraspecific range in living canids, has been considered for dimorphism but is more likely interspecific; this pattern may hint at dominance hierarchies potentially involving for mates or resources, a pattern seen in social carnivorans. The absence of fossilized dens or trackways showing coordinated movement leaves room for debate, with analogies to solitary hyena-like feeders contrasting evidence from abundance and morphology favoring at least loose social groups.

Locomotion and physiology

Epicyon displayed adaptations suited to endurance running across open terrains, featuring elongated limbs, a reduced that enhanced mobility, a flexible vertebral column, and a posture that facilitated efficient stride extension. These traits align with those of other large canids, though Epicyon haydeni exhibited a less gracile build compared to more specialized runners like wolves, likely due to its greater body mass limiting top speeds in favor of sustained pursuit. Forelimb morphology in combined efficiency with notable flexibility, as evidenced by humeral and radial features that cluster near felid-like scansorial morphospaces in geometric morphometric analyses. This suggests capabilities for supination and maneuvering in varied terrain, including potential climbing or pouncing, rather than purely linear running; studies of postcranial elements from sites, including localities, support this intermediate locomotor profile between terrestrial endurance and arboreal agility. Sensory adaptations in Epicyon included a prominent nasal chamber indicative of strong olfaction for prey detection over distances, consistent with borophagine cranial architecture that prioritized scent-based foraging alongside visual cues. The relatively short, robust skull shape raised debate on , potentially enhancing for close-range pursuits, though quantitative assessments of orbital orientation suggest it was moderate compared to predators like felids. Additionally, an elongated external auditory meatus points to acute hearing for locating prey or conspecifics in open environments. Physiological inferences from postcranial robusticity and limb scaling indicate Epicyon maintained a high metabolic rate to support its active, hypercarnivorous lifestyle, with proportions reflecting rapid growth and demands akin to modern large carnivorans. This endothermic profile, inferred from ecomorphological proxies rather than direct , underscores adaptations for prolonged activity in grasslands.

Paleoecology

Geographic and temporal distribution

Epicyon fossils date from the late Miocene to the early Pliocene, spanning the late Clarendonian North American Land Mammal Age (approximately 12–9 million years ago) to the early Hemphillian (approximately 9–5 million years ago). The genus achieved its greatest abundance and diversity during the Clarendonian stage, with records becoming sparser in the Hemphillian. The geographic distribution of Epicyon encompassed much of western, central, and eastern , ranging from in the east to and in the west, and northward into southern . Fossils have been recovered from at least 12 U.S. states, including , , , , , , , , , , , and . The type locality for E. haydeni, the most widespread , is the Merritt Dam Member of the Ash Hollow Formation in the Valley of . Stratigraphically, Epicyon remains are most commonly associated with the Ogallala Group in the central , as well as equivalent fluvial and lacustrine deposits elsewhere. Notable occurrences include the Snake Creek and Ash Hollow Formations in , the Love Bone Bed and Haile local faunas in , the Dove Spring and Green Valley Formations in , the Jack Swayze Quarry in , and the Port of Entry Pit in . These sites reflect a broad to continental interiors during a period of relative climatic warmth in the , prior to range contraction near the onset.

Habitat preferences

Epicyon primarily inhabited grassland-savanna environments across Miocene , as evidenced by , , macrofossil, and records from multiple sites indicating widespread open vegetation by the (approximately 11.6–5.3 Ma). These habitats featured a mix of grasses and scattered woodlands, particularly in the , where open landscapes covered up to 68% of the area by around 17 Ma. Sediment analyses from formations like the Ogallala in western further support a transition to expansive savannas during this period, driven by increasing aridity and cooling following the Middle Miocene Climatic Optimum. Fossil evidence from the Love Bone Bed in Alachua County, Florida, reveals habitat variability, with Epicyon occurring in more mesic, warm-temperate deciduous settings that included denser woodlands and savannas along the Gulf Coast, contrasting with the drier midcontinental plains. These eastern environments supported a higher proportion of browsers, indicating tolerance for closed-canopy areas amid overall open habitats. Epicyon showed a preference for warm, semi-arid conditions prevalent in the , yet demonstrated adaptability to mesic regions with increased moisture and winter precipitation. Stable data from paleosols and faunal teeth confirm that these climates facilitated the ecological shift toward open landscapes without a strict to extreme . Paleo-vegetation records associate Epicyon with the proliferation of C₄ grasses, which expanded rapidly in the (around 6.6–5.5 Ma), replacing C₃-dominated woodlands and forming mixed C₃-C₄ savannas that supported diverse mammalian communities. This co-occurrence is documented in the western through carbon ratios in sediments and enamels, highlighting Epicyon's to ecosystems where C₄ biomass reached modern levels by the Neogene-Pliocene boundary.

Ecological role and extinction

Epicyon served as an in North American ecosystems during the , occupying the top carnivore niche and primarily preying on large herbivores such as camelids like and equids like Neohipparion, which were abundant in open habitats. Its hypercarnivorous diet, exceeding 70% meat consumption, and bone-crushing adaptations enabled it to exploit these grazing ungulates effectively, filling a role similar to modern lions in maintaining dynamics through predation pressure on mid-to-large herbivores. This position as a dominant predator likely influenced prey population structures and nutrient cycling, with Epicyon's scavenging behaviors further contributing to decomposition processes. Epicyon faced competition from other borophagines, such as Borophagus, which overlapped in dietary niches and territorial ranges, as well as from declining amphicyonids and emerging early felids like machairodonts that specialized in ambush predation. These interactions, particularly with felids adapting to similar prey, intensified resource competition in increasingly arid landscapes, potentially limiting Epicyon's access to preferred prey. The genus underwent a gradual decline starting around 8 million years ago (Ma), coinciding with the diversification peak of borophagines in the Hemphillian, before becoming extinct by approximately 5 Ma. This temporal pattern reflects broader borophagine trends, with large species like Epicyon disappearing amid environmental shifts. Primary extinction drivers included the decline of key prey populations, such as oreodonts and other herbivores, during the Late Miocene as grasslands expanded and C4 vegetation dominated, reducing biomass for large grazers. Climate cooling from the mid-Miocene onward further exacerbated habitat fragmentation and prey scarcity through aridification. Heightened competition from advancing Caninae subfamilies and felids, better adapted to pursuit in open terrains, compounded these pressures, as evidenced by recent analyses linking borophagine declines to synchronous herbivore extinctions.

References

  1. https://www.floridamuseum.ufl.edu/florida-vertebrate-fossils/species/epicyon-haydeni/
  2. https://www.nps.gov/articles/000/revisiting-the-1940-badlands-expedition.htm
  3. https://www.smithsonianmag.com/science-nature/what-happened-to-the-bone-crushing-dogs-that-once-hunted-across-north-america-180987037/
  4. https://data.library.amnh.org/archives/agents/amnhc_2000180
  5. https://www.floridamuseum.ufl.edu/florida-vertebrate-fossils/sites/love-site/
  6. https://www.researchgate.net/figure/Epicyon-haydeni-from-the-Love-Bone-Bed-Local-Fauna-Alachua-County-Florida-UF-24570_fig2_254665578
  7. https://www.biodiversitylibrary.org/bibliography/213608
  8. https://www.researchgate.net/publication/267156822_Phylogenetic_systematics_of_the_Borophaginae_Carnivora_Canidae
  9. https://digitallibrary.amnh.org/items/89b7ec72-5735-4fd0-a24f-d97659f6e0b9
  10. https://onlinelibrary.wiley.com/doi/10.1002/jmor.10881
  11. https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1284&context=museummammalogy
  12. https://digitallibrary.amnh.org/bitstreams/45985d97-a9d2-4157-87c6-d2e21be36dc3/download
  13. https://doi.org/10.1038/s41598-018-37106-4
  14. https://doi.org/10.1002/jmor.10881
  15. https://museum.unl.edu/collections/vertebrate-paleontology/nebraska-county-fossils/keith.html
  16. https://store.beg.utexas.edu/files/GB/BEG-GB0024D.pdf
  17. https://digitalcommons.unl.edu/museummammalogy/282/
  18. https://pmc.ncbi.nlm.nih.gov/articles/PMC5936914/
  19. https://flmnhbulletin.com/index.php/flmnh/article/download/flmnh-vol45-no4-pp413-434/vol45-no4/1185
  20. https://pubs.geoscienceworld.org/paleobiol/article/86441/Were-there-pack-hunting-canids-in-the-Tertiary-and
  21. https://ufdcimages.uflib.ufl.edu/UF/E0/05/20/74/00001/HOLTE_S.pdf
  22. https://www.academia.edu/27222584/Evolutionary_trends_in_the_late_Miocene_hyena_like_dog_Epicyon_Carnivora_Canidae_
  23. https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=2587&context=wnan
  24. https://www.nature.com/articles/s41467-022-32300-5
  25. https://www.sciencedirect.com/science/article/pii/S2950117223000195
  26. https://www.researchgate.net/publication/260213073_A_new_stable_isotope_record_of_Neogene_paleoenvironments_and_mammalian_paleoecologies_in_the_western_Great_Plains_during_the_expansion_of_C4_grasslands
  27. https://www.nature.com/articles/ncomms8976
  28. https://pmc.ncbi.nlm.nih.gov/articles/PMC7442796/
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