Pecora

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Pecora
Temporal range: 20–0Ma Early Miocene - Recent
Pronghorn antelope
Scientific classification e
Kingdom:Animalia
Phylum:Chordata
Class:Mammalia
Order:Artiodactyla
Suborder:Cetruminantia
(unranked):Ruminantiamorpha
Suborder:Ruminantia
Infraorder:Pecora
Flower, 1883[1]
Families

 Cervidae
 †Gelocidae
 †Palaeomerycidae
 †Hoplitomerycidae
 †Climacoceratidae
 Giraffidae
 Antilocapridae
 †Leptomerycidae
 Moschidae
 Bovidae

 
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Pecora
Temporal range: 20–0Ma Early Miocene - Recent
Pronghorn antelope
Scientific classification e
Kingdom:Animalia
Phylum:Chordata
Class:Mammalia
Order:Artiodactyla
Suborder:Cetruminantia
(unranked):Ruminantiamorpha
Suborder:Ruminantia
Infraorder:Pecora
Flower, 1883[1]
Families

 Cervidae
 †Gelocidae
 †Palaeomerycidae
 †Hoplitomerycidae
 †Climacoceratidae
 Giraffidae
 Antilocapridae
 †Leptomerycidae
 Moschidae
 Bovidae

Pecora is an infraorder of even-toed hoofed mammals with ruminant digestion (Ruminantia, a clade within the Artiodactyla). Most members of Pecora have cranial appendages projecting from the frontal bones; only two extant genera lack them, Hydropotes and Moschus.[2] The name “Pecora” comes from the Latin word pecus, which means “horned livestock.”[3] Although most pecorans do have cranial appendages, only some of these appendages are properly called “horns,” and many scientists agree the appendages did not arise from a common ancestor, but instead evolved independently.[2][3][4][5] Likewise, while Pecora is a group supported by both molecular and morphological studies, morphological support for interrelationships among pecoran families is disputed.[2]

Evolutionary History[edit]

The first fossil ruminants appeared in the mid-Eocene, and were small, likely omnivorous, forest-dwellers.[6] Artiodactyls with cranial appendages first occur in the early Miocene.[6] The appearance of Pecora during the Miocene suggests their rapid diversification may correspond to the climate change events of that epoch.[6][7]

Taxonomy[edit]

Current attempts to determine the relationships among pecoran families (as well as all Artiodactyls) rely on molecular studies, as there has been little historical consensus in morphological studies.[2] The different families within Pecora are recognized as valid by different groups of scientists.[6]and sources therein, pp. 4-5

Anatomy[edit]

The Pecora share characteristics with other Artiodactyls, including a four-chambered stomach, and a paraxonic foot, meaning it supports weight on the third and fourth digits. Janis and Scott (1987) recognize several characters that distinguish Pecora from their sister taxon, Tragulina: an astragalus with parallel sides, a loss of the trapezium, and differences in parts of the skull such as the petrosal.[4]

Cranial Appendages[edit]

The distinguishing features of most pecoran families are cranial appendages. Modern Pecora (with the exception of the Moschidae) have one of four types of cranial appendages: horns, antlers, ossicones, and pronghorns.[6]

Horns[edit]

True horns have a bone core that is covered in a permanent sheath of keratin. They are indicative of Bovidae. Horns develop in the periosteum over the frontal bone, and can be curved or straight.[4] Surface features on the keratin sheath (e.g., ridges or twists) are thought to be caused by differential rates of growth around the bone core.[4]

Antlers[edit]

Antlers are bone structures that are shed and replaced each year in members of the family Cervidae. They grow from a permanent outgrowth of the frontal bone called the pedicle.[4] Antlers can be branched, as in the White-tailed deer (Odocoileus virginianus), or palmate, as in Moose (Alces alces).

Ossicones[edit]

Ossicones are permanent bone structures that fuse to the frontal or parietal bones during the lifetime of an animal.[4] They are found only in the Giraffidae and closely related extinct clades,[4] represented in modern animals by the Giraffe (Giraffa camelopardalis) and the Okapi (Okapia johnstoni).

Pronghorns[edit]

Pronghorns are similar to horns in that they have keratinous sheaths covering permanent bone cores; however, these sheaths are deciduous and can be shed like antlers.[4] Very little is known about development of pronghorns, but they are generally presumed to have evolved independently.[4] The only extant animal with pronghorns is the Pronghorn antelope (Antilocapra americana).

References[edit]

  1. ^ Flower, W. On the Arrangement of the Orders and Families of Existing Mammalia. Proceedings of the Zoological Society of London. 178 -186. 1883.
  2. ^ a b c d Hassanin, A., E. Douzery. Molecular and Morphological Phylogenies of Ruminantia and the Alternative Position of the Moschidae. Systematic Biology. 52: 206-228. 2003. doi: 10.1080/10635150390192726
  3. ^ a b Bubenik, A. Epigenetical, Morphological, Physiological, and Behavioral Aspects of Evolution of Horns, Pronghorns, and Antlers. in Horns, Pronghorns, and Antlers. G. Bubenik and A. Bubenik eds. Springer-Verlag. New York. 1990
  4. ^ a b c d e f g h i Janis, C., K. Scott. The Interrelationships of Higher Ruminant Families with Special Emphasis on the Members of the Cervoidea. American Museum Novitates. 2893: 1-85. 1987. http://digitallibrary.amnh.org/dspace/handle/2246/5180
  5. ^ Hassanin, A., F. Delsuc, A. Ropiquet. C. Hammer, B. Jansen van Vuuren, C. Matthee, M. Ruiz-Garcia, F. Catzeflis, V. Areskoug, T. T. Nguyen, A. Couloux. Pattern and Timing of Diversification of Cetartiodactyla (Mammalia, Laurasiatheria), as Revealed by a Comprehensive Analysis of Mitochondrial Genomes. Comptes Rendus Biologies. 335: 32-50. 2012. http://dx.doi.org/10.1016/j.crvi.2011.11.002
  6. ^ a b c d e DeMiguel, D., B. Azanza, J. Morales. Key Innovations in Ruminant Evolution: A Paleontological Perspective. Integrative Zoology. doi: 10.1111/1749-4877.12080
  7. ^ Morales, J., M. Pickford, D. Soria. Pachyostosis in a Lower Miocene Giraffoid from Spain, Lorancameryx pachyostoticus Nov. Gen. Nov. Sp. and Its Bearing on the Evolution of Bony Appendages in Artiodactyls. Geobios. 26:207-230. 1993. http://www.sciencedirect.com/science/article/pii/S001669959380016K
  8. ^ Ursing, B., K. Slack, U. Arnason. Subordinal artiodactyl relationships in the light of phylogenetic analysis of 12 mitochondrial protein-coding genes. Zoologica Scripta. 29: 83-88. 2000. http://onlinelibrary.wiley.com/doi/10.1046/j.1463-6409.2000.00037.x/abstract