Weigeltisauridae is a family of gliding neodiapsid

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...

s that lived during the Late Permian, between 258 and 252 million years ago. Fossils of weigeltisaurids have been found in Madagascar, Germany, Great Britain, and Russia. A possible weigeltisaurid, ''

Wapitisaurus Weigeltisauridae is a family of gliding neodiapsid reptiles that lived during the Late Permian, between 258 and 252 million years ago. Fossils of weigeltisaurids have been found in Madagascar, Germany, Great Britain, and Russia. A possible weigelt ...

'', been found in Early Triassic strata in North America, but its poor preservation makes referral to the group questionable. They are characterized by long, hollow rod-shaped bones extending from the torso that probably supported wing-like membranes. Similar membranes are also found in several other extinct reptiles such as kuehneosaurids and ''

Mecistotrachelos ''Mecistotrachelos'' is an extinct genus of gliding reptile believed to be an archosauromorph, distantly related to crocodylians and dinosaurs. The type and only known species is ''M. apeoros''. This specific name translates to "soaring longes ...

'', as well as living gliding lizards, although each group evolved these structures independently.

Skeleton

The skulls and jaws of weigeltisaurids are ornamented with horns and tubercles, including chameleon-like frills. The torso and limbs are slender. The skeletons of weigeltisaurds are lightened by large air spaces (

skeletal pneumaticity Skeletal pneumaticity is the presence of air spaces within bones. It is generally produced during development by excavation of bone by pneumatic diverticula (air sacs) from an air-filled space, such as the lungs or nasal cavity. Pneumatization is h ...

) within the bones. The

phalanges The phalanges (singular: ''phalanx'' ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones. ...

of the hands and feet are elongate contrasting strongly with those of most other primitive diapsids, but are similar to those of modern arboreal lizards. Unique to weigeltisaurids, the group possesses between 25 and 30 pairs of long, hollow rod-like bones, which project from the lower abdomen. These have been proposed to be modified gastralia or otherwise a novel bone ossification. Weigeltisaurus jaekeli diagram

Paleobiology

Weigeltisaurids have been suggested to be arboreal insectivores. Their limb morphology was well adapted for grasping tree bark, including vertical tree trunks. Due to their limb morphology, they were highly adapted for movement in the trees, and would likely have not been capable of moving quickly or efficiently on the ground. The cranial ornamentation may have served a display purpose.

Gliding

The gliding membrane of weigeltisaurids is distinct from those of other gliding reptiles, which are modified ribs originating from the upper-lateral surface of the body. In contrast, in weigeltisaurids, the rods originate from the lower-lateral surface of the body. The furling and unfurling of the gliding membrane were likely controlled by the abdominal muscles. Preserved fossils show that the bony rods had a high degree of flexibility, similar to the ribs of living gliding lizards. Due to the low-wing configuration, it is likely that the gliding surface was angled upwards to increase stability. In living gliding lizards, it has been found that the forelimbs grab hold of the membrane during flight, suggesting that the forelimbs are used to control the patagium while in flight. Similar behaviour has been proposed for weigeltisaurids, which is supported the presence of an additional phalange in the fourth digit of the hands of weigeltisaurids, which would have allowed them to more effectively grasp the wing. In a 2011 study comparing ''Coelurosauravus'' and other extinct gliding reptiles to modern ''Draco'' species, ''Coelurosauravus'' was found to be a less efficient glider than modern ''Draco'' due to its larger body size, with a substantial drop in height per glide.

Relationships

Weigeltisaurids have generally been interpreted as primitive neodiapsids, that lie outside of Sauria. It has been proposed that they are closely related to the

drepanosaur Drepanosaurs (members of the clade Drepanosauromorpha) are a group of extinct reptiles that lived between the Carnian and Rhaetian stages of the late Triassic Period, approximately between 230 and 210 million years ago. The various species of dre ...

s, a group of arboreal basal neodiapsids native to northern Pangaea during the Late Triassic. The proposed

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

containing the two groups was named Avicephala by Senter in 2004. Proposed

synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...

of the clade include "absence of intercentra in cervical region; absence of intercentra in dorsal region; scapulocoracoid, ratio of anteroposterior length at base of scapular blade to dorsoventral height of scapular blade between 0.4 and 0.25; outer process of fifth metatarsal absent."

Taxonomy

* '' Coelurosauravus'' Lower Sakamena Formation, Madagascar * '' Weigeltisaurus''

Kupferschiefer The Kupferschiefer (German for Copper Shale, also called Copper Slate) or Kupfermergel (Copper Marl), (T1 or Z1) is an extensive and remarkable sedimentary unit in Central Europe. The relatively monotonous succession is typically and maximum th ...

, Germany,

Marl Slate The Marl Slate Formation is a geological formation in England. Despite its name, it is mostly dolomite rock. The Marl Slate Formation was formed about 273 to 259 million years ago, during the Guadalupian and Lopingian epochs of the late Permian ...

, England * ''

Rautiania ''Rautiania'' is an extinct genus of gliding neodiapsid reptiles belonging to the family Weigeltisauridae. Isolated fossil remains of ''Rautiania'' are known from the Late Permian of Russia. The genus is known from two species, ''Rautiania alexan ...

'' Vyasovka Formation, Russia * '' Glaurung'' Kupferschiefer, Germany

References

Permian diapsids Triassic diapsids Avicephalans Lopingian first appearances Early Triassic extinctions Prehistoric reptile families {{triassic-reptile-stub