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Sphenacodontidae
 
 
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The Sphenacodontidae are a family of small to large, advanced, carnivorous
Carnivore

A carnivore , meaning 'meat eater' , is any animal with a diet consisting mainly of meat, whether it comes from animals living or dead .In a more general sense, an animal may be considered a carnivore if it prefers feeding on animal matter over plant matter....
, Late Pennsylvanian to middle Permian pelycosaur
Pelycosaur

The pelycosaurs were primitive Late Paleozoic synapsid amniotes. Some species were quite large and could grow up to 3 meters or more, although most species were much smaller....
s. Primitive forms (Haptodus
Haptodus

Haptodus was a small sphenacodontia, a lineage that includes therapsids. It was at least in length. It lived from Latest Carboniferous to Early Permian, in the equatorial Pangea....
, etc) were generally small in size (60 cm to 1 meter), but during the later part of the early Permian these animals grew progressively larger (up to 3 meters or more), to become the top predators
Apex predator

Apex predators are predators that, as adults, are not normally preyed upon in the wild by other large animals in significant parts of their range....
 of their environments.

The skull is long, deep and narrow, an adaptation for strong jaw muscles.






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The Sphenacodontidae are a family of small to large, advanced, carnivorous
Carnivore

A carnivore , meaning 'meat eater' , is any animal with a diet consisting mainly of meat, whether it comes from animals living or dead .In a more general sense, an animal may be considered a carnivore if it prefers feeding on animal matter over plant matter....
, Late Pennsylvanian to middle Permian pelycosaur
Pelycosaur

The pelycosaurs were primitive Late Paleozoic synapsid amniotes. Some species were quite large and could grow up to 3 meters or more, although most species were much smaller....
s. Primitive forms (Haptodus
Haptodus

Haptodus was a small sphenacodontia, a lineage that includes therapsids. It was at least in length. It lived from Latest Carboniferous to Early Permian, in the equatorial Pangea....
, etc) were generally small in size (60 cm to 1 meter), but during the later part of the early Permian these animals grew progressively larger (up to 3 meters or more), to become the top predators
Apex predator

Apex predators are predators that, as adults, are not normally preyed upon in the wild by other large animals in significant parts of their range....
 of their environments.

The skull is long, deep and narrow, an adaptation for strong jaw muscles. The front teeth are large and dagger-like, whereas the teeth in the sides and rear of the jaw are much smaller (hence the name of the well-known genus Dimetrodon
Dimetrodon

Dimetrodon was a predatory synapsid genus that flourished during the Permian Period , living between 280?265 million years ago. It was more closely related to mammals than to true reptiles such as lizards....
 - "two-measure tooth", although all members of the family have this attribute).

Several large (~3 meters) and advanced members of this group (Secodontosaurus
Secodontosaurus

Secodontosaurus was a pelycosaur that lived in Texas during the Early Permian age. Though it had the same body style as other sphenacodontidae, it had an unusually low and narrow skull....
, Ctenospondylus
Ctenospondylus

Ctenospondylus, was a pelycosaur that was about 3 meters long. It lived from Latest Carboniferous to Early Permian. It has been found in Ohio and Texas....
, Dimetrodon
Dimetrodon

Dimetrodon was a predatory synapsid genus that flourished during the Permian Period , living between 280?265 million years ago. It was more closely related to mammals than to true reptiles such as lizards....
) are distinguished by a tall sail along the back, made up of elongated vertebra
Vertebra

A vertebra is an individual bone in the flexible column that defines vertebrate animals. The vertebral column encases and protects the spinal cord, which runs from the base of the cranium down the dorsal side of the animal until reaching the pelvis....
l neural spines, which in life must have been covered with skin and blood vessels, and presumably functioned as a thermoregulatory
Thermoregulation

Thermoregulation is the ability of an organism to keep its core temperature within certain boundaries, even when the surrounding temperature is very different....
 device. However, possession of a sail does not appear to have been essential for these animals. For example there is the case in which one genus (Sphenacodon
Sphenacodon

Sphenacodon was a pelycosaur that was about in length. Sphenacodon belongs to the family Sphenacodontidae, a lineage that was related to the therapsids....
 - fossils known from New Mexico
New Mexico

New Mexico is a U. S. State located in the Southwestern United States of the United States. Inhabited by Native Americans in the United States populations for many centuries, it has also has been part of the Spanish Empire viceroyalty of New Spain, part of Mexico, and a U.S....
) lacks a sail, while a very similar and closely related genus (Dimetrodon
Dimetrodon

Dimetrodon was a predatory synapsid genus that flourished during the Permian Period , living between 280?265 million years ago. It was more closely related to mammals than to true reptiles such as lizards....
 - fossils known from Texas
Texas

Texas is a U.S. state located in the South Central United States, nicknamed the Lone Star State. Texas is the second largest U.S. state in both area and population, spanning , and with a growing population of 24.3 million residents....
) has one. During the Permian
Permian

The PermianThe term "Permian" was introduced into geology in 1841 by Sir Roderick Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian system" after the ancient kingdom...
, these two regions were separated by a narrow sea-way, but it is not clear why one geographically isolated
Geographical isolation

Geographic isolation, or allopatry, is a term used in the study of evolution. When part of a population of the same species becomes geographically isolated from the remainder, it may over time evolve characteristics different from the parent population ...
 group should evolve a sail, but the other group not.

The family
Scientific classification

Biological classification or scientific classification in biology, is a method by which biologists group and categorize species of organisms....
 Sphenacodontidae is actually paraphyletic as originally described, defined by shared primitive synapsid characters; these animals constitute an evolutionary gradation from primitive synapsid
Synapsid

Synapsids , also known as theropsids , are a class of animals that includes mammals and everything closer to mammals than to other living amniotes....
 to early therapsid. The clade
Clade

A clade is a term used in modern alpha taxonomy, the scientific classification of living and fossil organisms, to describe a monophyletic group, defined as a group consisting of a single common ancestor and all its descendants.The term "monophyletic group" is used in this article in the conventional sense of "an a...
 Sphenacodontia
Sphenacodontia

Sphenacodontia is the name given to the clade that includes the Sphenacodontidae and all their descendants . They first appear during the Late Pennsylvanian epoch....
 is used to designate the monophyletic group that includes Sphenacodontids and all their descendants (including mammals), while Sphenacodontidae in the strict sense includes only specialised pelycosaurs, and not earlier more primitive members of the family like Haptodus, Palaeohatteria, Pantelosaurus, and Cutleria (in pre-cladistic
Cladistics

Cladistics is the hierarchical classification of species based on evolutionary ancestry. Cladistics is distinguished from other taxonomic systems because it focuses on evolution rather than similarities between species, and because it places heavy emphasis on objective, quantitative analysis....
 classifications all included under the genus Haptodus). The clade Sphenacodontoidea is used by Laurin and Reisz 1997 to designate the most recent common ancestor
Most recent common ancestor

In genetics, the most recent common ancestor of any set of organisms is the most recent individual from which all organisms in the group are directly Common descent....
 of Sphenacodontidae and Therapsida
Therapsida

Therapsids are an Order of synapsids ,and are believed to include mammals and their immediate evolutionary ancestors....
 and all their descendants, and is defined by certain features of the skull.

Sphenacodontid fossils are so far known only from North America
North America

North America is the northern continent of the Americas, situated in the Earth's northern hemisphere and almost totally in the western hemisphere....
 and Europe
Europe

Europe is, conventionally, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural , the Caspian Sea, and by the Caucasus Mountains to the southeast....
.

See also

  • Evolution of mammals
    Evolution of mammals

    __FORCETOC__The evolution of mammals from synapsids was a gradual process which took approximately 70 million years, beginning in the mid-Permian....
  • haptodus
    Haptodus

    Haptodus was a small sphenacodontia, a lineage that includes therapsids. It was at least in length. It lived from Latest Carboniferous to Early Permian, in the equatorial Pangea....


External links

  • - list of species