Arctocyonidae
Encyclopedia
Arctocyonidae is an extinct family
of unspecialized, primitive mammal
s with more than 20 genera most abundant during the Paleocene
, but extant from the late Cretaceous
to the early Eocene
.
These animals are thought to be the ancestors of the orders Mesonychia and Cetartiodactyla
.
s. Arctocyonid teeth show much individual variation and because many members of this family are only known from fossil teeth, the taxonomy of the genera is highly unstable.
They had relatively short limbs lacking specializations associated with ungulate
s (e.g. reduced side digits, fused bones, and hoofs), and long, heavy tails. Their primitive anatomy makes it unlikely that they were able to run down preys, but with their powerful proportions, claws, and long canines, they may have been able to overpower smaller animals in surprise attacks.
. Archaic arctocyanids, such as Prolatidens, have been found in the early Paleocene layers in Hainin, Belgium. From there this family evolved into a wide variety of genera, including Arctocyon
(known as/similar to Claenodon in North America), Arctocyonides, Landenodon, and Mentoclaenodon
, found in the late Paleocene layers of Cernay
, France.
A near-complete skeleton of the North American Chriacus
, an early arctocyonid and also one of the smallest, has been found in Wyoming. This raccoon
-like animal had powerful limb muscles and a long, robust, and maybe prehensile tail. Capable of both balancing in a tree and digging, it was adapted both to an arboreal and a terrestrial life.
Larger arctocyonids spent most of their time on the forest floor but were probably still able to climb trees. It can be assumed that they may have partly taken over the role of large predators in Paleocene faunas together with other similar groups, such as the triisodontids and mesonychid
s, two families traditionally classified as condylarths but now assigned to the order Mesonychia.
Large arctocyonids include:
The Arctocyon
features the characteristics of the entire family. This robust, bear-sized animal was a plantigrade
ungulate
with short limbs; its feet had claws and it had a long tail. It had a long skull equipped with a large sagittal crest
and large canines, especially the lower ones. It had low-crowned, bunodont molars (i.e. teeth with rounded cusps) similar to modern bears, and it is assumed that they had a similar omnivorous diet. The related subfamily Arctocyonides were smaller and more slender.
Mentoclaenodon
were, judging from the scarce material available on the genus, larger than the other two large genera and tended to develop long canines similar to early big cat
s.
(incertae sedis
)
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of unspecialized, primitive mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s with more than 20 genera most abundant during the Paleocene
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...
, but extant from the late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
to the early Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
.
These animals are thought to be the ancestors of the orders Mesonychia and Cetartiodactyla
Cetartiodactyla
Cetartiodactyla is the clade in which whales and even-toed ungulates have currently been placed. The term was coined by merging the name for the two orders, Cetacea and Artiodactyla, into a single word. The term Cetartiodactyla reflects the idea that whales evolved within the artiodactyls...
.
Characteristics
Arctocyonid skulls had large canines and relatively sharp teeth and were thus superficially similar to those of modern carnivores. However, arctocyanid teeth were not specialized for slicing meat; these animals were probably omnivorous and definitely the least herbivorous of the condylarthCondylarth
Condylarthra is an order of extinct placental mammals known primarily from the Paleocene and Eocene epochs. Condylarths are among the most characteristic Paleocene mammals and they illustrate the evolutionary level of the Paleocene mammal fauna....
s. Arctocyonid teeth show much individual variation and because many members of this family are only known from fossil teeth, the taxonomy of the genera is highly unstable.
They had relatively short limbs lacking specializations associated with ungulate
Ungulate
Ungulates are several groups of mammals, most of which use the tips of their toes, usually hoofed, to sustain their whole body weight while moving. They make up several orders of mammals, of which six to eight survive...
s (e.g. reduced side digits, fused bones, and hoofs), and long, heavy tails. Their primitive anatomy makes it unlikely that they were able to run down preys, but with their powerful proportions, claws, and long canines, they may have been able to overpower smaller animals in surprise attacks.
Evolutionary variation
The arctocyonids were the most common mammals in Europe during the PaleocenePaleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...
. Archaic arctocyanids, such as Prolatidens, have been found in the early Paleocene layers in Hainin, Belgium. From there this family evolved into a wide variety of genera, including Arctocyon
Arctocyon
Arctocyon is an extinct genus of condylarth mammals. The jackal-sized creature was plantigrade, that is, it walked on the soles of its feet, like a bear. Although probably mainly terrestrial, it is possible that it also climbed trees. Arctocyon was probably an omnivore....
(known as/similar to Claenodon in North America), Arctocyonides, Landenodon, and Mentoclaenodon
Mentoclaenodon
Mentoclaenodon is an extinct genus of condylarth mammals.Mentoclaenodon had large upper canines like some Miocene and Pleistocene big cats. In fact,the Arctocyonid Mentoclaenodon, its close relative Anacodon, and the Creodont Machaeroides were the first mammals to develop saber-teeth....
, found in the late Paleocene layers of Cernay
Cernay-lès-Reims
Cernay-lès-Reims is a commune in the Marne department in north-eastern France.-See also:*Communes of the Marne department...
, France.
A near-complete skeleton of the North American Chriacus
Chriacus
Chriacus is an extinct genus of prehistoric mammal which lived around 63 million years ago.Chriacus was a raccoon-like mammal of the Paleocene epoch, with a length of about including its long, robust tail, which may or may not have been prehensile. It had a light build, weighing approximately...
, an early arctocyonid and also one of the smallest, has been found in Wyoming. This raccoon
Raccoon
Procyon is a genus of nocturnal mammals, comprising three species commonly known as raccoons, in the family Procyonidae. The most familiar species, the common raccoon , is often known simply as "the" raccoon, as the two other raccoon species in the genus are native only to the tropics and are...
-like animal had powerful limb muscles and a long, robust, and maybe prehensile tail. Capable of both balancing in a tree and digging, it was adapted both to an arboreal and a terrestrial life.
Mesonychid
Mesonychia are an extinct order of medium to large-sized carnivorous mammals that were closely related to artiodactyls and to cetaceans...
s, two families traditionally classified as condylarths but now assigned to the order Mesonychia.
Large arctocyonids include:
The Arctocyon
Arctocyon
Arctocyon is an extinct genus of condylarth mammals. The jackal-sized creature was plantigrade, that is, it walked on the soles of its feet, like a bear. Although probably mainly terrestrial, it is possible that it also climbed trees. Arctocyon was probably an omnivore....
features the characteristics of the entire family. This robust, bear-sized animal was a 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...
ungulate
Ungulate
Ungulates are several groups of mammals, most of which use the tips of their toes, usually hoofed, to sustain their whole body weight while moving. They make up several orders of mammals, of which six to eight survive...
with short limbs; its feet had claws and it had a long tail. It had a long skull equipped with a large sagittal crest
Sagittal crest
A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull of many mammalian and reptilian skulls, among others....
and large canines, especially the lower ones. It had low-crowned, bunodont molars (i.e. teeth with rounded cusps) similar to modern bears, and it is assumed that they had a similar omnivorous diet. The related subfamily Arctocyonides were smaller and more slender.
Mentoclaenodon
Mentoclaenodon
Mentoclaenodon is an extinct genus of condylarth mammals.Mentoclaenodon had large upper canines like some Miocene and Pleistocene big cats. In fact,the Arctocyonid Mentoclaenodon, its close relative Anacodon, and the Creodont Machaeroides were the first mammals to develop saber-teeth....
were, judging from the scarce material available on the genus, larger than the other two large genera and tended to develop long canines similar to early big cat
Big cat
The term big cat – which is not a biological classification – is used informally to distinguish the larger felid species from smaller ones. One definition of "big cat" includes the four members of the genus Panthera: the tiger, lion, jaguar, and leopard. Members of this genus are the only cats able...
s.
Classification
Subfamilies and genera:(incertae sedis
Incertae sedis
, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
)
- Arctocyonides Lemoine, 1891
- Arctocyonides weigelti Lemoine, 1891
- Carcinodon Scotti, 1892
- Carcinodon aquilonius
- ChriacusChriacusChriacus is an extinct genus of prehistoric mammal which lived around 63 million years ago.Chriacus was a raccoon-like mammal of the Paleocene epoch, with a length of about including its long, robust tail, which may or may not have been prehensile. It had a light build, weighing approximately...
(syn. Epichriacus, Metachriacus, Spanoxyodon, Tricentes)- Chriacus badgleyi
- Chriacus badwini
- Chriacus calenancus
- Chriacus gallinae
- Chriacus katrinae
- Chriacus metocometi
- Chriacus oconostotae
- Chriacus pelvidens
- Chriacus punitor
- Deuterogonodon
- Heteroborus
- Hyodectes
- Lambertocyon
- Landenodon
- MentoclaenodonMentoclaenodonMentoclaenodon is an extinct genus of condylarth mammals.Mentoclaenodon had large upper canines like some Miocene and Pleistocene big cats. In fact,the Arctocyonid Mentoclaenodon, its close relative Anacodon, and the Creodont Machaeroides were the first mammals to develop saber-teeth....
- Mimotricentes
- Oxytomodon
- Paratriisodon
- Princetonia
- Prothryptacodon (syn. Pantinomia)
- Thryptacodon
- Loxolophinae
- Baioconodon (syn. Ragnarok)
- Loxolophus (syn. Paradoxodon, Paradoxodonta, Protochriacus, Protogonodon)
- Arctocyoninae
- Anacodon Cope,1882
- Anacodon cultridens Matthew,1915
- Anacodon nexus Gazin,1956
- Anacodon ursidens Cope,1882
- ArctocyonArctocyonArctocyon is an extinct genus of condylarth mammals. The jackal-sized creature was plantigrade, that is, it walked on the soles of its feet, like a bear. Although probably mainly terrestrial, it is possible that it also climbed trees. Arctocyon was probably an omnivore....
Blainville, 1841 (syn. Claenodon, Neoclaenodon)- Arctocyon corrugatus (Cope,1883)
- Arctocyon ferox
- Arctocyon latidens
- Arctocyon montanensis
- Arctocyon mumak
- Colpoclaenus Patterson & McGrew,1962
- Colpoclaenus keeferi
- Colpoclaenus procyonoides
- Anacodon Cope,1882