Barbourofelis

''Barbourofelis'' is an extinct genus of large, predatory, from a subfamily of feliform carnivoran mammals of known as Barbourofelinae, part of the Nimravidae superfamily. ''Barbourofelis'', along with ''Albanosmilus'', was the last members barbourofelids, as well as the last nimravids. ''Barbourofelis'' lived North America and Eurasia during the Miocene epoch from 12 to 7 Ma.

Four species are currently recognized within the genus: ''B. fricki'', ''B. loveorum'', ''B. morrisi'', and ''B. piveteaui''. ''B. loveorum'' directly evolved from from ''B. morrisi'', and later evolved into ''B. fricki''. ''B. morrisi'' likely evolved from ''Albanosmilus'' migrating into North America. With ''B. piveteaui'' evolving from reverse migration from North America into Eurasia.

''B. morrisi'' and ''B. piveteaui'' were the smallest species being about as large as a leopard. ''B. loveorum'' was the second largest species and could’ve weighed anywhere from . ''B. fricki'' was the most recent and largest species of the genus, estimated to have been as large as lions, weighing around . It’s believed that ''Barbourofelis'' was an ambulatory, ambush predator that hunted within closed forested environments.

Taxonomy

Classification

''Barbourofelis'' was named by Bertrand Schultz, Marian Schultz, and Larry Martin in 1970 in honor of Erwin Hinckley Barbour, who died a few days before the holotype was discovered. Its type species is ''Barbourofelis fricki'' and is the type genus of the subfamily Barbourofelinae. Originally, barbourofelids were considered members of the machairodont subfamily. However, this was called into question, and by the 1980s and 90s barbourofelids were considered to be nimravids instead of felids. In the 2000s, Morlo et al. (2004) argued that barbourofelids ranked as their own family, known as Barbourofelidae. This was also the prevailing view for barbourofelids during the 2010s, although some experts still considered them to be nimravids.

However, in the 2020s, majority of experts have began reclassifying them as nimravids.

Evolution

'' Albanosmilus jourdani'' is believed to be the ancestor to the genus, which migrated into North America sometime during the Late Miocene. ''B. morrisi'' was the earliest species within the genus, probably from the result ''Albanosmilus'' migrating to North America and was likely ancestral to ''B. loveorum'', which later evolved into ''B. fricki''. The discovery ''B. piveteau'' suggests ''Barbourofelis'' reverse migrated back into Eurasia.

Description

The type species, ''B. fricki'', is thought to have been a lion-sized predator, having a weight comparable to an African lion, with limb bones indicating a muscular, robust body. Large individuals of ''B. fricki'' have been reconstructed with shoulder heights of around . In 2021, Barret estimated based on m1 length regression, ''B. fricki'' may have weighed up to , making it the largest nimravid. However, ''B. morrisi'' was believed to have been closer to the size of a large leopard and , being intermediate in size between '' Sansanosmilus'' and ''B. fricki''. ''B. loveorum'' was the second largest species within the genus. In a 2012 paper, Meachen estimated that ''B. loveorum'' may have weighed on average. However, Orcutt and Calde estimated that the species may have been larger, averaging around , based on articular width of the humerus. ''B. piveteaui'' was described to being similar in size to ''B. morrisi''.

The genus had the longest canines of all the barbourofelids, which were also flattened, indicating a high degree of specialization to its diet. These canines had a longitudinal groove on the lateral surface that has been described as a means of allowing blood from a wound they have inflicted to flow away. This groove more likely was an adaptation to make the canines lighter while maintaining their strength. Other notable traits include the presence of a postorbital bar, the presence of a ventrally extended mental process (bony extensions on either side of the lower jaw), and the shortening of the skull behind the orbits, in addition to having a very robust constitution. The barbourofelids were probably very stocky in build, resembling a bear-like lion or lion-like bear. Based on its foot structure, species of ''Barbourofelis'' might have had a semi-plantigrade walking stance.

The most extensive selections of bones found for this genus come from ''B. loveorum'' and have allowed further inference to the proportions of other members of the genus.

Paleobiology

Growth and development

A 1988 study found that based on the analysis of the skulls and maxillary materials, ''Barbourofelis'' had delayed eruptions of deciduous upper canines, which suggests that ''Barbourofelis'' practiced a long period of parental care. In addition, skeletons of juvenile ''Barbourofelis'' have been found, and examination of their skeletons indicates that the cubs would reach near-adult size before their milk sabers would begin to erupt. This indicates that they were dependent on their mother or potential family group until well into their second year. Such a long period of dependence would have likely led to situations in which near-adult cubs would have likely helped to restrain prey while their mother made the kill.

Social behavior

''Barbourofelis'' was found to have large carnassial teeth, meant it was for efficiently processing a carcass and ate at a fast and competitive manner. This indicated it either lived in a highly competitive ecosystem or that it was social, or even a combination of both scenarios. In addition, experts also argued due to the delayed eruption of their upper canines, which may be further evidence of gregariousness in ''Barbourofelis.'' Although, some authors have suggested that ''Barbourofelis'' was a solitary ambush predator.

Predatory behavior

Ormsby 2021 found that ''B. loveorum'' may have less constrained forelimb movement compared to the contemporary machairodont '' Nimravides galiani'' and extant felids. The increase in mobility suggests it relied on grappling prey and subduing prey, as an ambulatory ambush predator, that walked and trotted around the forest floor similar to ursids, wolverines, and badgers. It would’ve been opportunistic and attacked prey upon reach, and could’ve engaged in scavenging similar to wolverines due to their large carnassial teeth. In addition to possibly being able to climb, although it wouldn’t have been arboreal. A 2005 study found that the leopard-sized ''B. morrisi'' had a similar crural index to the lion-sized ''Smilodon fatalis'', but had a lower brachial index than the machairodont and ambush predators, having an index closer to that of ambulators. This suggests ''Barbourofelis'' had the same leverage as ''Smilodon''. In addition, ''B. loveroum'' and ''B. fricki'' were found to have even smaller brachial and crural indexes than ''Smilodon'', suggesting that barbourofelids possibly had a greater power output of the limbs than ''Smilodon''. The robustness of the humerus suggests it could’ve taken on prey larger than itself.

Previously, it has been suggested by Naples and Martin that ''B. fricki'' had a jaw gape of 115 degrees or greater. However, Lautenschlager et al. (2020) suggests a lower jaw gape for ''Barbourofelis''. Their analysis suggests jaw gapes of 89.13, 85.29, and 65.68 degrees for ''B. fricki'', ''B. loveorum'', and ''B. morrisi'' respectively''. ^{Including supplementary materials}''

Figueirido et al. (2024) study on the cranial biomechanics of ''B. fricki'' found based on m. masseter pars profunda, this species would’ve had a maximum jaw gape of 73 degrees and found little evidence to support jaw gapes of over 90 degrees''.'' They also found that ''Barbourofelis'' skull was less stressed when it came to bilateral canine biting compared to ''Smilodon fatalis''. When it came to stabbing, the skull of ''Barbourofelis'' were not as evenly distributed as ''Smilodon'', with regional stresses mainly present in occipital and parietal bones, as well as the upper canines. With pulling-back, stress in ''Smilodon'' skull was more evenly distributed than ''Barbourofelis'', with the stress of ''Barbourofelis'' being concentrated in the premaxilla, parietal-occipital region, postorbital bar, and canines. Despite having a stress resistant skull, the canines were found to be very weak when extrinsic forces are applied due to its sharp and flattened canines, so it would’ve been able to penetrate the more easily than ''Smilodon''. The authors argued, since ''Barbourofelis'' skull experiences less stress than ''Smilodon'', it may have been more generalist in prey killing than ''Smilodon''.

Brain anatomy

Despite its derived craniodental adaptations, ''Barbourofelis'' brain was similar to that of Oligocene nimravids. Compared to living felids, its brain its anterior lobes were more narrow and the highest point of the cerebrum was situated more caudally.

Paleoecology

''B. loveorum's'' environment in the Love Bone Beds deposits (of Clarendonian Age) was a mixture of grassland, riverine forest, and marshes, in which it would have shared territory with herbivorous animals like the amphibious rhinoceros ''Teleoceras'', the protoceratid ''Synthetoceras'', the camel ''Aepycamelus'', horses like ''Neohipparion'' and ''Nannippus'', and carnivores like ''Nimravides'', in addition to borophaginae canids such as ''Epicyon'' and ''Borophagus'', and the bear ''Agriotherium''. Forelimb morphology suggests ''B. loveorum'' and ''N. galiani'' weren’t competing with one another, but instead niche partitioned by preferring different habitats. The robust forelimbs of ''Barbourofelis'' suggests it preferred forested environments, while ''Nimravides'' preferred more open habitats. This is further supported by forest dwelling fauna such as tapirs, '' Prosthennops'', ''Aepycamelus'', and ''B. loveorum'' itself being unusually abundant in Love Bone Beds compared to Late Miocene sites. In addition, the shorter metacarpals of ''Barbourofelis'' suggested it hunted smaller prey than ''Nimravides.''

During the following stage, the Hemphillian, ''B. fricki'' shared territory with the machairodont species '' Amphimachairodus coloradensis''. Both genera of machairodont, as well as the bear ''Agriotherium'' and the dogs ''Epicyon'' and ''Borophagus'' would have presented competition to the barbourofelid, while any and all of the large animals present were potential prey species.

The extinction of ''Barbourofelis'', is thought to have been due to faunal overturn in the Late Miocene, not competition with machairodonts.

References

{{Taxonbar, from1=Q133084, from2=Q11908163, from3=Q118645088, from4=Q111039026, from5=Q111039508

Miocene feliforms
Barbourofelidae
Miocene mammals of North America
Pliocene mammals of North America
Fossil taxa described in 1970
Prehistoric carnivoran genera