Diadectes was a genus of large, very reptile

Reptile

Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

-like amphibians that lived during the early Permian

Permian

The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. 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...

 period (Cisuralian - Guadalupian epochs, between 299 and 271 million years ago). It is one of the very first herbivorous

Herbivore

Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...

 tetrapod

Tetrapod

Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...

s, and also one of the first fully terrestrial animals to attain large size.

Description

Diadectes was a heavily built animal, 1.5 to 3 meters long, with a thick-boned skull, heavy vertebrae and rib

Rib

In vertebrate anatomy, ribs are the long curved bones which form the rib cage. In most vertebrates, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax...

s, massive limb girdle

Girdle

A girdle is a garment that encircles the lower torso, perhaps extending below the hips, and worn often for support. The word girdle originally meant a belt. In modern English, the term girdle is most commonly used for a form of women's foundation wear that replaced the corset in popularity...

s and short, robust limbs. The nature of the limbs and vertebrae clearly indicate a terrestrial animal.

Paleobiology

It possesses some characteristics of reptilians and amphibians, combining a reptile-like skeleton with a more primitive, seymouriamorph

Seymouriamorpha

Seymouriamorpha were a small but widespread group of reptiliomorphs. Many seymouriamorphs were terrestrial or semi-aquatic. However, aquatic larvae bearing external gills and grooves from the lateral line system has been found, making them unquestionably amphibians. The adults were terrestrial...

-like skull. Diadectes has been classified as belonging to the sister group of the amniote

Amniote

The amniotes are a group of tetrapods that have a terrestrially adapted egg. They include synapsids and sauropsids , as well as their fossil ancestors. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes...

s.

Among its primitive features, Diadectes has a large otic notch

Otic notch

Otic notches are invagination in the posterior margin of the skull roof, one behind each orbit. Such notches are found in labyrinthodonts and some of their immediate ancestors, but not their reptilian descendants...

 (a feature found in all labyrinthodonts

Labyrinthodontia

Labyrinthodontia is an older term for any member of the extinct subclass of amphibians, which constituted some of the dominant animals of Late Paleozoic and Early Mesozoic times . The group is ancestral to all extant landliving vertebrates, and as such constitutes an evolutionary grade rather...

, but not in reptiles) with an ossified tympanum

Tympanum (zoology)

The tympanum is an external hearing structure in animals such as frogs, toads, insects, and mammals, to name a few.-Anurans:In frogs and toads, it is located just behind the eye. It does not actually process sound waves; it simply transmits them to the amphibian's inner ear, which is protected...

. At the same time its teeth show advanced specialisations for a herbivorous diet that are not found in any other type of early Permian animal. The eight front teeth are spatulate and peg-like, and served as incisor

Incisor

Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...

s that were used to nip off mouthfuls of vegetation. The broad blunt cheek teeth show extensive wear associated with occlusion

Occlusion (dentistry)

Occlusion, in a dental context, means simply the contact between teeth. More technically, it is the relationship between the maxillary and mandibular teeth when they approach each other, as occurs during chewing or at rest....

, and would have functioned as molar

Molar (tooth)

Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....

s, grinding up the food. It also had a partial secondary palate

Secondary palate

The secondary palate is an anatomical structure that divides the nasal cavity from the oral cavity in many vertebrates.In human embryology, it refers to that portion of the hard palate that is formed by the growth of the two palatine shelves medially and their mutual fusion in the midline...

, which meant it could chew its food and breath at the same time, something many even more advanced reptiles were unable to do.

These traits are likely adaptations related to the animals high fiber herbivorous diet, and evolved independently of similar traits seen in some reptilian groups. Many of the reptile-like details of the post-cranial skeleton are possibly related to carrying the substantial trunk, these may be independetly derived traits on Diadectes and their relatives. Though very similar, they would be anaologous

Analogy (biology)

An analogy is a trait or an organ that appears similar in two unrelated organisms. The cladistic term for the same phenomenon is homoplasy, from Greek for same form. Biological anologies are often the result of convergent evolution....

 rather than homologous

Homology (biology)

Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...

 to those of early amniotes like pelycosaurs and pareiasaur

Pareiasaur

The Pareiasaurs - Family Pareiasauridae - are a clade of medium-sized to large herbivorous anapsid reptiles that flourished during the Permian period....

s, as the first reptiles evolved from small, swamp dwelling animals like Casineria

Casineria

Casineria was a tetrapod which lived 340 million years ago in the Mississippian epoch. Casineria was a small animal with a total length estimated to have been 15 centimeters. It lived in what was then a fairly dry environment in Scotland. It is noted for its mix of primitive and advanced ...

and Westlothiana

Westlothiana

Westlothiana lizziae was a reptile-like amphibian or possibly early reptile that bore a superficial resemblance to modern-day lizards. It lived during the Carboniferous period, about 350 million years ago. The type specimen was discovered in East Kirkton Quarry, Bathgate, Scotland, in 1984, and was...

.

Discovery

Diadectes fossil remains are known from a number of locations across North America, especially the Texas Red Beds

Red beds

Red beds are sedimentary rocks, which typically consist of sandstone, siltstone, and shale that are predominantly red in color due to the presence of ferric oxides. Frequently, these red-colored sedimentary strata locally contain thin beds of conglomerate, marl, limestone, or some combination of...

 (Wichita

Wichita River

The Wichita River, part of the Red River watershed, lies in north-central Texas. Rising in northeastern Knox County at the confluence of its North and South Forks, the river flows northeast across Baylor, Archer, Wichita, and Clay counties before joining the Red River just west of Byers Bend in...

 and Clear Fork

Clear Fork

Clear Fork may refer to a location in the United States:*Clear Fork in Tennessee*Clear Fork in Kentucky and Tennessee*Clear Fork Mohican River in Ohio*Clear Fork, West Virginia, a town...

).

Classification and species

Numerous species have been assigned to Diadectes, though most of those have proven to be synonyms of one another. Similarly, many supposed separate genera of diadectids have been shown to be junior synonyms of Diadectes. One of these, Nothodon, was actually published by Othniel Charles Marsh

Othniel Charles Marsh

Othniel Charles Marsh was an American paleontologist. Marsh was one of the preeminent scientists in the field; the discovery or description of dozens of news species and theories on the origins of birds are among his legacies.Born into a modest family, Marsh was able to afford higher education...

 five days before the name Diadectes was published by his rival Edward Drinker Cope

Edward Drinker Cope

Edward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen...

. Despite this fact, in 1912 Case synonymized the two names and treated Diadectes as the senior synonym, which has been followed by other paleontologists since, despite the fact that it violates the rules of biological nomenclature

International Code of Zoological Nomenclature

The International Code of Zoological Nomenclature is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...

.