Pecora

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 their 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 have cranial appendages, only some of these are properly called “horns”, and many scientists agree that these appendages did not arise from a common ancestor, but instead evolved independently on at least two occasions.[2][3][4][5] Likewise, while Pecora as a group is supported by both molecular and morphological studies, morphological support for interrelationships between pecoran families is disputed.[2]

For other uses, see Pecora (disambiguation).

Pecora
Temporal range: 50–0 Ma
Early Eocene - recent
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Suborder: Ruminantia
Infraorder: Pecora
Flower, 1883[1]
Families

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

Evolutionary history

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 that its rapid diversification may correspond to the climate change events of that epoch.[6][7]

Taxonomy

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

Infraorder Pecora ("horned ruminants", "higher ruminants")

Anatomy

Pecorans share characteristics with other artiodactyls, including a four-chambered stomach, and a paraxonic foot, meaning that it supports weight on the third and fourth digits. Several characteristics distinguish Pecora from its sister taxon, Tragulina: an astragalus with parallel sides, a loss of the trapezium, and differences in parts of the skull such as the petrosal bone.[4]

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

  • 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 are bony 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 the moose (Alces alces).
  • 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 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 the 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
  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. Hassanin, A.; Douzery, E. (2003). "Molecular and Morphological Phylogenies of Ruminantia and the Alternative Position of the Moschidae". Systematic Biology. 52 (2): 206–228. doi:10.1080/10635150390192726. PMID 12746147.
  3. 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. 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.; Delsuc, F.; Ropiquet, A.; Hammer, C.; Matthee, C.; Ruiz-Garcia, M.; Catzeflis, F.; Areskoug, V.; Nguyen, T. T.; Couloux, A. (2012). "Pattern and Timing of Diversification of Cetartiodactyla (Mammalia, Laurasiatheria), as Revealed by a Comprehensive Analysis of Mitochondrial Genomes". Comptes Rendus Biologies. 335 (1): 32–50. doi:10.1016/j.crvi.2011.11.002. PMID 22226162.
  6. DeMiguel, D.; Azanza, B.; Morales, J. (2014). "Key Innovations in Ruminant Evolution: A Paleontological Perspective". Integrative Zoology. 9 (4): 412–433. doi:10.1111/1749-4877.12080. PMID 24148672.
  7. Morales, J.; Pickford, M.; Soria, D.; Pachyostosis (1993). "Lorancameryx pachyostoticus Nov. Gen. Nov. Sp. and Its Bearing on the Evolution of Bony Appendages in Artiodactyls". Geobios. 26 (2): 207–230. doi:10.1016/S0016-6995(93)80016-K.
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