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Pecora is an infraorder of Artiodactyla mammals with ruminant digestion. Most members of Pecora have cranial appendages projecting from their frontal bones; only two extant genera lack them, Hydropotes and Musk Deer. The name "Pecora" comes from the Latin word pecus, which means "cattle".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 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.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 Likewise, while Pecora as a group is supported by both molecular and morphological studies, morphological support for interrelationships between pecoran families is disputed.
The appearance of many Pecoran fossils during the Miocene suggests that its rapid diversification may correspond to the climate change events of that epoch, as this time period was marked by much of Earth's forest habitats being replaced by grasslands due to widespread cooling and drying.
It is likely that the antelopes, giraffids, and pronghorns evolved in an open environment while the cervids, including the caribou, evolved in a woodland habitat. The type of gallop in Pecorian species is shown to be closely related to their environment and anatomy, where light Pecorian species use both flexed and extended suspensions in their fast gallops. The white-tail and mule-deer have been observed to primarily use the extended suspension, since in this phase of their gallop they leap over bushes and logs that are present in their brush environment. However, heavy Pecorian species do not use extended suspensions as most have backs that slope downward with shorter hind legs.
Pecora's placement within Artiodactyla can be represented in the following cladogram:(see e.g. Fig S10)
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. Different families within Pecora are recognized as valid by different groups of scientists.and sources therein, pp. 4–5
Until the beginning of the 21st century it was understood that the family Moschidae (musk deer) was sister taxon to Cervidae. However, a 2003 phylogenetic study by Alexandre Hassanin (of National Museum of Natural History, France) and colleagues, based on and nuclear analyses, revealed that Moschidae and Bovidae form a clade sister to Cervidae. According to the study, Cervidae diverged from the Bovidae-Moschidae clade 27 to 28 million years ago. The following cladogram is based on the 2003 study.
Infraorder Pecora ("horned ruminants", "higher ruminants")
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.
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