Nimravidae
Cat-like predators, Hoplophoneus and Dinictis
The most specialized of all carnivores are the nimravids, primitive saber-toothed predators distantly related to the more familiar but later appearing true cats of the family Felidae. Like true felids, nimravids were obligate carnivores, and had large eyes placed frontally for binocular vision. Nimravids are cat-like in general appearance (short faced with hooded retractable claws and reduced posterior molars) and were probably able to climb trees. Their predatory adaptations are readily apparent, particularly in their saber-shaped canines and most were designed as ambush predators, probably well camouflaged and able to take prey that is both smaller and larger than themselves. Among all the different mammals found in the White River Badlands, and especially the predators, nimravid "cats" are among the rarest fossils of all.
Nimravids entered North America during the late Eocene and occupied the niche of modern felids until they disappeared in the very late Oligocene. Only Barbourofelis remains as a possible nimravid despite its appearance in the late Miocene. From the time of their general disappearance at the end of the Oligocene until the appearance of true Felidae from Europe in the early Miocene, North America lacked a cat-like predator for 5 million years.
The cat-like nimravids as well as all true cats had/have enlarged canines divided into three shapes: highly elongate, flattened canines with fine serrations (dirk-toothed); somewhat elongated, more coarsely serrated flattened canines (scimitar-toothed); and short round conical canines like the ones found in modern felids. The dirk-toothed forms (Hoplophoneus and Eusmilus) tended to be short legged and more plantigrade, and ranged in size from that of a puma, in the case of Hoplophoneus primaveus, to that of a jaguar (Holophoneus occidentalis and Eusmilus). Dirk-toothed species were badger or bear-like in proportions and probably ambushed their prey. The scimitar-toothed Dinictis was smaller but gave rise to the jaguar-sized Nimravus and Pognodon, both genera of which were more cursorial.
Dinictis and Hoplophoneus were the most common nimravids found in the White River Badlands. Hoplophoneus was a long sleek cat, measuring 4ft in length plus tail, with short legs, a stout muscular neck and nearly the size of a modern leopard. Both Hoplophoneus and the smaller, lynx-sized Dinictis were characterized by a skull which allowed the jaw to open incredibly wide. This was thought to allow the nimravid to kill by stabbing its prey with its large canines. Nimravids must have been one of the most feared hunters of these times. Its strong fast body, amazing bite and sharp claws would have been deadly to many Badlands herbivores.
Habitat preference played a key role in the evolution and distribution of nimravids. The dirk-toothed Hoplophoneus probably lived in more forested habitats than did the long-limbed, scimitar-toothed Dinictis of more open grassland, the latter group stalking its prey prior to attack. Regardless, the opening of the heavily forested Eocene woodlands into parkland and savanna habitats helped diversify nimravids but their dentition, developed for killing large prey in relation to their body size worked to their disadvantage. In the face of continually opening, arid habitats, only small mammals were periodically left available as food and probably hastened their extinctino. Later Barbourofelinae lineages probably suffered in the face of competition from true felids.
Written by Ryan C and Alan S
Nimravids entered North America during the late Eocene and occupied the niche of modern felids until they disappeared in the very late Oligocene. Only Barbourofelis remains as a possible nimravid despite its appearance in the late Miocene. From the time of their general disappearance at the end of the Oligocene until the appearance of true Felidae from Europe in the early Miocene, North America lacked a cat-like predator for 5 million years.
The cat-like nimravids as well as all true cats had/have enlarged canines divided into three shapes: highly elongate, flattened canines with fine serrations (dirk-toothed); somewhat elongated, more coarsely serrated flattened canines (scimitar-toothed); and short round conical canines like the ones found in modern felids. The dirk-toothed forms (Hoplophoneus and Eusmilus) tended to be short legged and more plantigrade, and ranged in size from that of a puma, in the case of Hoplophoneus primaveus, to that of a jaguar (Holophoneus occidentalis and Eusmilus). Dirk-toothed species were badger or bear-like in proportions and probably ambushed their prey. The scimitar-toothed Dinictis was smaller but gave rise to the jaguar-sized Nimravus and Pognodon, both genera of which were more cursorial.
Dinictis and Hoplophoneus were the most common nimravids found in the White River Badlands. Hoplophoneus was a long sleek cat, measuring 4ft in length plus tail, with short legs, a stout muscular neck and nearly the size of a modern leopard. Both Hoplophoneus and the smaller, lynx-sized Dinictis were characterized by a skull which allowed the jaw to open incredibly wide. This was thought to allow the nimravid to kill by stabbing its prey with its large canines. Nimravids must have been one of the most feared hunters of these times. Its strong fast body, amazing bite and sharp claws would have been deadly to many Badlands herbivores.
Habitat preference played a key role in the evolution and distribution of nimravids. The dirk-toothed Hoplophoneus probably lived in more forested habitats than did the long-limbed, scimitar-toothed Dinictis of more open grassland, the latter group stalking its prey prior to attack. Regardless, the opening of the heavily forested Eocene woodlands into parkland and savanna habitats helped diversify nimravids but their dentition, developed for killing large prey in relation to their body size worked to their disadvantage. In the face of continually opening, arid habitats, only small mammals were periodically left available as food and probably hastened their extinctino. Later Barbourofelinae lineages probably suffered in the face of competition from true felids.
Written by Ryan C and Alan S
Taxa of Cats listed by abundance
Hoplophoneus primaveus (large sized type)
Hoplophoneus occidentalis (large sized type)
Dinictis squaliadens (medium sized type)
Eusmulis dakotensis (uncommon large lion sized type)
OBSOLETE TAXA
Dinictis fortis (lower zone Titanothere zone)
Dinictis paucidens, Hoplophoneus oreodontis, H. marshi, H. molossus (Middle Oligocene Oreodont zone)
Dinictis bombifrons, Hoplophoneus insolens, (Upper Oligocene, Protoceras zone)
Hoplophoneus occidentalis (large sized type)
Dinictis squaliadens (medium sized type)
Eusmulis dakotensis (uncommon large lion sized type)
OBSOLETE TAXA
Dinictis fortis (lower zone Titanothere zone)
Dinictis paucidens, Hoplophoneus oreodontis, H. marshi, H. molossus (Middle Oligocene Oreodont zone)
Dinictis bombifrons, Hoplophoneus insolens, (Upper Oligocene, Protoceras zone)