Pecora
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Pecora is an
infraorder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between Family_(biology), family and Class_(biology), class. In biological classification, the order is a taxonomic rank used in the classific ...
of even-toed hoofed
mammals A mammal () is a vertebrate animal of the class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle e ...
with
ruminant Ruminants are herbivorous grazing or browsing artiodactyls belonging to the suborder Ruminantia that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microb ...
digestion. Most members of Pecora have cranial appendages projecting from their frontal bones; only two extant genera lack them, '' Hydropotes'' and '' Moschus''. The name "Pecora" comes from the Latin word , 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.


Evolutionary history

The first fossil ruminants appeared in the
Early Eocene In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...
and were small, likely
omnivorous An omnivore () is an animal that regularly consumes significant quantities of both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize ...
, forest-dwellers. Molecular dating studies estimate that
Ruminantia Ruminants are herbivorous grazing or browsing artiodactyls belonging to the suborder Ruminantia that are able to acquire nutrients from plant-based food by Enteric fermentation, fermenting it in a specialized stomach prior to digestion, principa ...
split into the two sister clades Pecora and Tragulina around 45 million years ago, during the
Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...
. However, it was not until 15 million years later, at around 30 million years ago during the
Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
, that the
evolutionary radiation An evolutionary radiation is an increase in taxonomic diversity that is caused by elevated rates of speciation, that may or may not be associated with an increase in morphological disparity. A significantly large and diverse radiation within ...
of Pecora began and the five families appeared (
Bovidae The Bovidae comprise the family (biology), biological family of cloven-hoofed, ruminant mammals that includes Bos, cattle, bison, Bubalina, buffalo, antelopes (including Caprinae, goat-antelopes), Ovis, sheep and Capra (genus), goats. A member o ...
, Cervidae, Moschidae, Giraffidae, and Antilocapridae). The appearance of many Pecoran fossils during the
Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
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.


Taxonomy and classification

Pecora is an
infraorder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between Family_(biology), family and Class_(biology), class. In biological classification, the order is a taxonomic rank used in the classific ...
within the larger suborder
Ruminantia Ruminants are herbivorous grazing or browsing artiodactyls belonging to the suborder Ruminantia that are able to acquire nutrients from plant-based food by Enteric fermentation, fermenting it in a specialized stomach prior to digestion, principa ...
, and is the
sister A sister is a woman or a girl who shares parents or a parent with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to ref ...
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
to the
infraorder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between Family_(biology), family and Class_(biology), class. In biological classification, the order is a taxonomic rank used in the classific ...
Tragulina (of which Tragulidae is the only surviving
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
). Pecora's placement within
Artiodactyla Artiodactyls are placental mammals belonging to the order (biology), order Artiodactyla ( , ). Typically, they are ungulates which bear weight equally on two (an even number) of their five toes (the third and fourth, often in the form of a hoof ...
can be represented in the following
cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
:(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 A sister is a woman or a girl who shares parents or a parent with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to ref ...
to Cervidae. However, a 2003
phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...
study by Alexandre Hassanin (of National Museum of Natural History, France) and colleagues, based on
mitochondria A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is us ...
l and nuclear analyses, revealed that Moschidae and
Bovidae The Bovidae comprise the family (biology), biological family of cloven-hoofed, ruminant mammals that includes Bos, cattle, bison, Bubalina, buffalo, antelopes (including Caprinae, goat-antelopes), Ovis, sheep and Capra (genus), goats. A member o ...
form a
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
sister to Cervidae. According to the study, Cervidae diverged from the Bovidae-Moschidae clade 27 to 28 million years ago. The following
cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
is based on the 2003 study. Infraorder Pecora ("horned ruminants", "higher ruminants") *
Incertae sedis or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...
** Family † Dromomerycidae ** Family Antilocapridae ( pronghorn) * Parvorder Bovimorpha ** Superfamily Cervoidea *** Family Cervidae ( deer) ** Superfamily Bovoidea *** Family Moschidae (
musk deer Musk deer can refer to any one, or all eight, of the species that make up ''Moschus'', the only extant genus of the family (biology), family Moschidae. Despite being commonly called deer, they are not true deer belonging to the family Cervidae, b ...
) *** Family
Bovidae The Bovidae comprise the family (biology), biological family of cloven-hoofed, ruminant mammals that includes Bos, cattle, bison, Bubalina, buffalo, antelopes (including Caprinae, goat-antelopes), Ovis, sheep and Capra (genus), goats. A member o ...
(
cattle Cattle (''Bos taurus'') are large, domesticated, bovid ungulates widely kept as livestock. They are prominent modern members of the subfamily Bovinae and the most widespread species of the genus '' Bos''. Mature female cattle are calle ...
,
goat The goat or domestic goat (''Capra hircus'') is a species of Caprinae, goat-antelope that is mostly kept as livestock. It was domesticated from the wild goat (''C. aegagrus'') of Southwest Asia and Eastern Europe. The goat is a member of the ...
s,
sheep Sheep (: sheep) or domestic sheep (''Ovis aries'') are a domesticated, ruminant mammal typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus '' Ovis'', in everyday usage it almost always refers to d ...
, and
antelope The term antelope refers to numerous extant or recently extinct species of the ruminant artiodactyl family Bovidae that are indigenous to most of Africa, India, the Middle East, Central Asia, and a small area of Eastern Europe. Antelopes do ...
s) * Parvorder Giraffomorpha ** Family † Palaeomerycidae ** Superfamily Giraffoidea *** Family Giraffidae (
giraffe The giraffe is a large Fauna of Africa, African even-toed ungulate, hoofed mammal belonging to the genus ''Giraffa.'' It is the Largest mammals#Even-toed Ungulates (Artiodactyla), tallest living terrestrial animal and the largest ruminant on ...
s and okapi) *** Family † Climacoceratidae


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. 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. * True horns have a bone core that is covered in a permanent sheath of
keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. It is the key structural material making up Scale (anatomy), scales, hair, Nail (anatomy), nails, feathers, horn (anatomy), horns, claws, Hoof, hoove ...
. They are indicative of Bovidae. Horns develop in the
periosteum The periosteum is a membrane that covers the outer surface of all bones, except at the articular surfaces (i.e. the parts within a joint space) of long bones. (At the joints of long bones the bone's outer surface is lined with "articular cartila ...
over the frontal bone, and can be curved or straight. 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. *
Antler Antlers are extensions of an animal's skull found in members of the Cervidae (deer) Family (biology), family. Antlers are a single structure composed of bone, cartilage, fibrous tissue, skin, nerves, and blood vessels. They are generally fo ...
s 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. 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. They are found only in the Giraffidae and closely related extinct clades, 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. Very little is known about the development of pronghorns, but they are generally presumed to have evolved independently. The only extant animal with pronghorns is the pronghorn antelope ('' Antilocapra americana'').


References


External links

* {{Taxonbar, from=Q772442 Ruminants Extant Burdigalian first appearances