Post by Infinity Blade on Feb 3, 2015 3:26:33 GMT 5
Arctocyon spp.
Life restoration of Arctocyon primaevus. © @ RomanYevseyev (Roman Yevseyev)
Temporal range: Early to Late Paleocene (Danian to Thanetian; 61.7 to 56.8 Ma[1])
Scientific classification:
Life
Domain: Eukaryota
(unranked): Unikonta
(unranked): Opisthokonta
(unranked): Holozoa
(unranked): Filozoa
Kingdom: Animalia
Subkingdom: Eumetazoa
(unranked): Bilateria
Clade: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Clade: Olfactores
Clade: Craniata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Clade: Eugnathostomata
Clade: Teleostomi
Superclass: Tetrapoda
Clade: Reptiliomorpha
Clade: Amniota
Clade: Synapsida
Clade: Eupelycosauria
Clade: Sphenacodontia
Clade: Sphenacodontoidea
Order: Therapsida
Suborder: Cynodontia
Clade: Prozostrodontia
Clade: Mammaliaformes
Class: Mammalia
Legion: Cladotheria
Sublegion: Zatheria
Infralegion: Tribosphenida
Subclass: Theria
Clade: Eutheria
Infraclass: Placentalia
Subcohort: Exafroplacentalia
Magnorder: Boreoeutheria
Superorder: Laurasiatheria
Clade: Ungulata
Order: †Arctocyonia
Family: †Arctocyonidae
Genus: †Arctocyon
Species: †A. primaevus (type)
†A. acrogenius
†A. corrugatus
†A. ferox
†A. matthesi
†A. montanensis
†A. mumak
Arctocyon is an extinct genus of archaic ungulate that lived in the Paleocene of Europe and North America.
Description:
Arctocyon (at least A. primaevus) was a wolf-sized mammal.[2][3] The limb bones not only suggest that the forelimb joints were flexible, but also that the abductor and adductor muscles of the arm and forearm were well developed, and the powerful digital flexors suggest powerful grasping and manipulative abilities with the paws. Additionally, each of the five digits possessed sharp claws. With these, Arctocyon could grasp prey.[2][3]
Although, the dentition was not specialized for cutting or slicing meat, the skull had a well developed sagittal crest and the cervical vertebrae had well developed neural processes. This suggests powerful jaw muscles and head movements consistent with active predation. The body in general was as large as those of several extant canids and felids, except with much more robust bones. Therefore, although Arctocyon was not a specialized predator, it could have still hunted other animals.[2][3] The cheek teeth were broad and flat, more like a bear’s than a specialized carnivorous mammal’s. As such, Arctocyon was omnivorous, and could get much of its diet from fruits, nuts, seeds, and insects.[3]
The hindlimb anatomy was congruent with forelimb anatomy, with powerful adductors, flexors, and rotators of the hip joint.[2] The most anterior caudal vertebrae suggest the tail was a powerful, well-muscled organ that was stiff at the base and important to locomotion.[2]
The lumbar vertebrae were stiff, possessing revolute zygapophyses no extant mammal possesses, and which would have precluded any lateral movement. It is suggested that Arctocyon probably moved in a controlled fashion (although it could also climb trees).[2] Together with the extremely stout limbs and long, heavy tail, Arctocyon may have been a rather clumsy animal.[3]
Skeleton of Arctocyon primaevus. Original source->
A. ferox was 15-20% larger than A. corrugatus, but 25% smaller than A. acrogenius. It also differed from A. corrugatus by possessing a more robust mandible and shorter postorbital constriction. Additionally, A. primaevus had a more elongated skull than A. ferox.[4]
Arctocyon possessed a relatively small brain for its size, like other Paleocene mammals. It and its contemporary mammals show that after the K-Pg extinction event, early placentals actually decreased the size of their brain by virtue of body mass increasing at a faster rate. It was later in the Eocene when crown placental groups increased the size of their brains through marked growth in sensory regions.[5]
The skull and brain cavity of Arctocyon primaevus (left) compared with that of Hyrachyus modestus, an Eocene crown group placental mammal (right). Notice the markedly smaller brain of Arctocyon.
References:
[1] www.fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=42200
[2] Argot, C. Postcranial Analysis of a Carnivoran-Like Archaic Ungulate: The Case of Arctocyon primaevus (Arctocyonidae, Mammalia) from the Late Paleocene of France. J Mammal Evol 20, 83–114 (2013). doi.org/10.1007/s10914-012-9198-x
[3] www.paleocene-mammals.de/predators.htm
[4] Kondrashov, P. E., & Lucas, S. G. (2004). [url=https://www.google.com/books/edition/Paleogene_Mammals/fJivCQAAQBAJ?hl=en&gbpv=1&dq=arctocyon+species&pg=PA11&printsec=frontcoverArctocyon (Mammalia, Arctocyonidae) from the Paleocene of North America[/url]. Bull New Mex Mus Nat Hist Sci, 26, 11-20.
[5] Bertrand, O. C., Shelley, S. L., Williamson, T. E., Wible, J. R., Chester, S. G., Flynn, J. J., ... & Brusatte, S. L. (2022). Brawn before brains in placental mammals after the end-Cretaceous extinction. Science, 376(6588), 80-85.
Life restoration of Arctocyon primaevus. © @ RomanYevseyev (Roman Yevseyev)
Temporal range: Early to Late Paleocene (Danian to Thanetian; 61.7 to 56.8 Ma[1])
Scientific classification:
Life
Domain: Eukaryota
(unranked): Unikonta
(unranked): Opisthokonta
(unranked): Holozoa
(unranked): Filozoa
Kingdom: Animalia
Subkingdom: Eumetazoa
(unranked): Bilateria
Clade: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Clade: Olfactores
Clade: Craniata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Clade: Eugnathostomata
Clade: Teleostomi
Superclass: Tetrapoda
Clade: Reptiliomorpha
Clade: Amniota
Clade: Synapsida
Clade: Eupelycosauria
Clade: Sphenacodontia
Clade: Sphenacodontoidea
Order: Therapsida
Suborder: Cynodontia
Clade: Prozostrodontia
Clade: Mammaliaformes
Class: Mammalia
Legion: Cladotheria
Sublegion: Zatheria
Infralegion: Tribosphenida
Subclass: Theria
Clade: Eutheria
Infraclass: Placentalia
Subcohort: Exafroplacentalia
Magnorder: Boreoeutheria
Superorder: Laurasiatheria
Clade: Ungulata
Order: †Arctocyonia
Family: †Arctocyonidae
Genus: †Arctocyon
Species: †A. primaevus (type)
†A. acrogenius
†A. corrugatus
†A. ferox
†A. matthesi
†A. montanensis
†A. mumak
Arctocyon is an extinct genus of archaic ungulate that lived in the Paleocene of Europe and North America.
Description:
Arctocyon (at least A. primaevus) was a wolf-sized mammal.[2][3] The limb bones not only suggest that the forelimb joints were flexible, but also that the abductor and adductor muscles of the arm and forearm were well developed, and the powerful digital flexors suggest powerful grasping and manipulative abilities with the paws. Additionally, each of the five digits possessed sharp claws. With these, Arctocyon could grasp prey.[2][3]
Although, the dentition was not specialized for cutting or slicing meat, the skull had a well developed sagittal crest and the cervical vertebrae had well developed neural processes. This suggests powerful jaw muscles and head movements consistent with active predation. The body in general was as large as those of several extant canids and felids, except with much more robust bones. Therefore, although Arctocyon was not a specialized predator, it could have still hunted other animals.[2][3] The cheek teeth were broad and flat, more like a bear’s than a specialized carnivorous mammal’s. As such, Arctocyon was omnivorous, and could get much of its diet from fruits, nuts, seeds, and insects.[3]
The hindlimb anatomy was congruent with forelimb anatomy, with powerful adductors, flexors, and rotators of the hip joint.[2] The most anterior caudal vertebrae suggest the tail was a powerful, well-muscled organ that was stiff at the base and important to locomotion.[2]
The lumbar vertebrae were stiff, possessing revolute zygapophyses no extant mammal possesses, and which would have precluded any lateral movement. It is suggested that Arctocyon probably moved in a controlled fashion (although it could also climb trees).[2] Together with the extremely stout limbs and long, heavy tail, Arctocyon may have been a rather clumsy animal.[3]
Skeleton of Arctocyon primaevus. Original source->
A. ferox was 15-20% larger than A. corrugatus, but 25% smaller than A. acrogenius. It also differed from A. corrugatus by possessing a more robust mandible and shorter postorbital constriction. Additionally, A. primaevus had a more elongated skull than A. ferox.[4]
Arctocyon possessed a relatively small brain for its size, like other Paleocene mammals. It and its contemporary mammals show that after the K-Pg extinction event, early placentals actually decreased the size of their brain by virtue of body mass increasing at a faster rate. It was later in the Eocene when crown placental groups increased the size of their brains through marked growth in sensory regions.[5]
The skull and brain cavity of Arctocyon primaevus (left) compared with that of Hyrachyus modestus, an Eocene crown group placental mammal (right). Notice the markedly smaller brain of Arctocyon.
References:
[1] www.fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=42200
[2] Argot, C. Postcranial Analysis of a Carnivoran-Like Archaic Ungulate: The Case of Arctocyon primaevus (Arctocyonidae, Mammalia) from the Late Paleocene of France. J Mammal Evol 20, 83–114 (2013). doi.org/10.1007/s10914-012-9198-x
[3] www.paleocene-mammals.de/predators.htm
[4] Kondrashov, P. E., & Lucas, S. G. (2004). [url=https://www.google.com/books/edition/Paleogene_Mammals/fJivCQAAQBAJ?hl=en&gbpv=1&dq=arctocyon+species&pg=PA11&printsec=frontcoverArctocyon (Mammalia, Arctocyonidae) from the Paleocene of North America[/url]. Bull New Mex Mus Nat Hist Sci, 26, 11-20.
[5] Bertrand, O. C., Shelley, S. L., Williamson, T. E., Wible, J. R., Chester, S. G., Flynn, J. J., ... & Brusatte, S. L. (2022). Brawn before brains in placental mammals after the end-Cretaceous extinction. Science, 376(6588), 80-85.
