Postorbital bone

The postorbital is one of the bones in vertebrate skulls which forms a portion of the dermal skull roof and, sometimes, a ring about the orbit. Generally, it is located behind the postfrontal and posteriorly to the orbital fenestra. In some vertebrates, the postorbital is fused with the postfrontal to create a postorbitofrontal.


  • Roemer, A. S. 1956. Osteology of the Reptiles. University of Chicago Press. 772 pp.

Abelisaurus (; "Abel's lizard") is a genus of predatory abelisaurid theropod dinosaur during the Late Cretaceous Period (Campanian) of what is now South America. It was a bipedal carnivore that probably reached about 7.4 metres (24 ft 3 in) in length, although this is uncertain as it is known from only one partial skull.


Austriadraco is a genus of pterosaur living during the Late Triassic in the area of present Austria. Its only species—Austriadraco dallavecchiai—was previously attributed to Eudimorphodon, and its closest relatives may have been Eudimorphodon or Arcticodactylus.In June 1994, near Seefeld in Austrian Tirol, at a 1600 metres high mountain trail to the Reither Spitze, in the vicinity of the Reither Joch-Alm, Bernd Lammerer discovered a pterosaur skeleton. The remains have been secured as five stone plates, removed on several occasions. In 2003, Peter Wellnhofer identified the fossil as a specimen of Eudimorphodon, a cf. E. ranzii. As it was 10 to 25% shorter than the latter's holotype, Wellnhofer considered it a juvenile. The same year Fabio Marco Dalla Vecchia doubted the comparability to E. ranzii and suggested that it represent a separate Eudimorphodon species. In 2009, Dalla Vecchia concluded that the specimen was neither a juvenile nor closely related to Eudimorphodon.In 2015, Alexander Kellner named the separate genus Austriadraco, with the type species Austriadraco dallavecchiai. The generic name is a combination of the Latin words Austria and draco, "dragon". The specific name honours Dalla Vecchia. The Life Science Identifiers are for the genus 120B3003-6DE3-41B4-AF6B-6F242FB2A777 and for the species 6E123721-07EA-419CB755-9981CC7D9209.The holotype, BSP 1994 I 51, was found in a layer of the Seefeld Formation, dating from the late Norian. It consists of a partial and disarticulated skeleton with skull. It contains both frontal bones, a left jugal, the lower jaws, loose teeth, vertebrae of the neck, back and tail, the shoulder girdle, both humeri, a first wing phalanx, the pelvis, a shinbone and a calf bone. The fused frontals had in 2003 been incorrectly identified as a breast bone by Wellnhofer. The bones have been partly preserved as impressions only and many are fragmented. The fossil is part of the collection of the Bayerische Staatssammlung für Paläontologie und historische Geologie at Munich.Austriadraco dallavecchiai is a small species. Humerus length is about four centimetres. In 2015 Kellner indicated several distinguishing traits. Some of these are autapomorphies. The frontal bone has a short front branch. The jugal bone has short branches to the front, in the direction of the maxilla and the nasal bone, and a long narrow upwards branch running towards the postorbital bone. In the outer rear side of the lower jaw an opening is present, the mandibular fenestra. The coronoid process of the surangular bone is low. The shoulder blade is considerably longer, 62%, than the coracoid.Additionally, a unique combination of in themselves not unique traits is present. The coracoid is broad, with a constricted shaft. In the pelvis, the ischipubic plate, the fusion of the pubic bone with the ischium, is deep. The shinbone is relatively long, with a length of 57.7 millimetres attaining 70% of the length of the humerus and 92% of the length of the first phalanx of the (fourth) wingfinger.According to Dalla Vecchia's analysis, Austriadraco would have a very basal position in the Pterosauria. Kellner concluded that its affinities were uncertain and placed Austriadraco in a separate, undefined, Austriadraconidae. He suggested a close relationship with Arcticodactylus as both taxa shared the trait of a short coracoid.


Bergamodactylus is a genus of basal pterosaur living during the Late Triassic (early Norian) in the area of present-day Bergamo province in Italy. Its only species is Bergamodactylus wildi. It was previously regarded as a juvenile Eudimorphodon or as identical to Carniadactylus.In 1978, Rupert Wild described a small pterosaur specimen in the collection of the Museo di Paleontologia dell´Università di Milano, found near Cene in Lombardy. He referred to it as the "Milan Exemplar" and identified it as a juvenile of Eudimorphodon ranzii. Wild noted considerable differences with the latter's type specimen but these were explained as reflecting the young age of the animal.In 2009, Fabio Marco Dalla Vecchia confirmed an earlier conclusion by Alexander Kellner that the specimen must have been at least subadult in view of the fusion of the scapula and the coracoid, the upper wristbones being fused into a syncarpal, and the fusion of the extensor process on the first wing phalanx. Dalla Vecchia referred the specimen to Carniadactylus.In 2015, Kellner concluded that the Milan Exemplar represented a different species from Carniadactylus. It showed differences in build that could not be explained by individual variation, it was much smaller though of similar age, and it was of a younger geological age. He named a separate genus and species Bergamodactylus wildi. The generic name combines a reference to Bergamo with a Greek δάκτυλος, daktylos, "finger", a usual suffix in pterosaur names since Pterodactylus. The specific name honours Wild.The holotype, MPUM 6009, was found in a layer of the Calcari di Zorzino Formation dating from the early Norian (upper Alaunian). It consists of a partial skeleton including the skull, compressed on a single plate. It is largely articulated and includes the lower jaws, most of the wings, much of the vertebral column except the tail, and hindlimb elements. Some bones have only been preserved as impressions.Bergamodactylus is one of the smallest known pterosaurs: Kellner in 2015 estimated the wingspan at just 465 millimetres. He also established some distinguishing traits. The postorbital bone is slender with a thin branch towards the frontal bone. The praemaxilla does not reach the lower rim of the external nostril. The fourth metacarpal is short, with only 40% of the length of the humerus and 30% of the length of the ulna. The thighbone is short, attaining just half of the length of either the ulna or the first wing finger phalanx.Bergamodactylus has multi-cusped teeth like Eudimorphodon but their number strongly differs: fourteen in both the upper jaw and the lower jaw as against respectively twenty-nine and twenty-eight in the latter species. Additional differences with Carniadactylus include a tooth row that extends further to the rear, a lower mandibula, a higher placed deltopectoral crest on the humerus and a shorter upper part of the kinked pteroid. Bergamodactylus has a short second phalanx of the wing finger in common with Carniadactylus.Kellner placed Bergamodactylus, within the Novialoidea, in the Campylognathoidea.


Derwentiinae is a subfamily of rhytidosteid temnospondyls from the Permian and Triassic periods of Australia and India. It includes the genera Arcadia, Deltasaurus, Derwentia, Indobrachyops, and Rewana. Derwentiinae was named in a 2011 study that analyzed the phylogenetic relationships of rhytidosteids. It was a replacement name for the family Derwentiidae, which was named in 2000.


Eohyosaurus is an extinct genus of basal rhynchosaur known from the early Middle Triassic (early Anisian stage) Burgersdorp Formation of Free State, South Africa. It contains a single species, Eohyosaurus wolvaardti.

Glaurung schneideri

Glaurung is an extinct genus of weigeltisaurid reptile from the Upper Permian of Germany. The only known species is Glaurung schneideri. Originally considered a specimen of Coelurosauravus, a later study named it as a new genus after noting that it had several unique characteristics relative to other weigeltisaurids. These characteristics included a low skull, small eyes, smooth parietal and squamosal bones, and spiny jugal bones.


Ilokelesia is an abelisaur found in 1991, preserved in the layers of the earliest Late Cretaceous of the Huincul Formation, Neuquén Group, located near Plaza Huincul, Neuquén Province, Argentina. The specimen, consisting of very fragmentary elements of the skull and the axial and appendicular skeleton, was described by Rodolfo Coria and Leonardo Salgado in late 1998.


Jinyunpelta ("Jinyun shield") is a genus of herbivorous ankylosaurine thyreophoran dinosaur from the Cretaceous Liangtoutang Formation of Jinyun County, Zhejiang, China; it has one species, the type species J. sinensis. This species is the basalmost ankylosaur known to have had a proper tail club.

Kadimakara australiensis

Kadimakara is an extinct genus of early archosauromorph reptile from the Arcadia Formation of Queensland, Australia. It was seemingly a very close relative of Prolacerta, a carnivorous reptile which possessed a moderately long neck. The generic name Kadimakara references prehistoric creatures from Aboriginal myths which may have been inspired by ice-age megafauna. The specific name K. australiensis relates to the fact that it was found in Australia. Prolacerta and Kadimakara were closely related to the Archosauriformes, a successful group which includes archosaurs such as crocodilians, pterosaurs, and dinosaurs.


Mosaiceratops is a genus of ceratopsian described by Zheng, Jin & Xu in 2015 found in the Xiaguan Formation of Neixiang County. Although phylogenetic analysis have found it to be the most basal neoceratopsian, the authors noted that several features in the premaxilla and nasal bones are shared with the family Psittacosauridae, indicating that neoceratopsians evolved premaxillary teeth twice and that Psittacosauridae is not a primitive family as previously thought.


Myrmecodaptria (meaning "ant eater" in Greek) is an extinct genus of scleroglossan lizard from the Late Cretaceous Djadokhta Formation in Ukhaa Tolgod, Mongolia. The type and only species, Myrmecodaptria microphagosa (microphagosa meaning "eating little" in Greek), was named in 2000 by paleontologists Gao Keqin and Mark Norell. Myrmecodaptria is known from a single holotype skull and lower jaws. It is distinguished from all other lizards by its extremely elongated skull. The eyes are placed close to the snout, which is short and rounded. The top of the skull is covered in bony knobs called osteoderms. The parietal bone at the back of the skull is elongated and about as long as the frontal bones, which are the usually the longest bones along the top of the skull in lizards. The squamosal bone at the back of the skull reaches forward to connect with the jugal bone behind the eye, forming a thin arch between the temporal fenestrae. Myrmecodaptria also has fewer and more widely spaced teeth in its jaws than do most other lizards.When Myrmecodaptria was first described in 2000 it was thought to be a member of Gekkota, the group that includes living geckos and pygopodids (legless lizards). Characteristics that Myrmecodaptria shares in common with gekkotans include fused frontal bones that form a tube within the skull and the absence of a postorbital bone. However, Myrmecodaptria has many features that are not found in gekkotans, such as the presence of a small hole at the top of the skull called the parietal foramen, a thick jugal bone forming a complete postorbital bar behind the eye socket, and a complete upper temporal arch closing off a pair of holes at the top of the skull called the supratemporal fenestrae. The first study to include Myrmecodaptria in a phylogenetic analysis was published in 2006, and it did not find support for Myrmecodaptria being a gekkotan. Instead, Myrmecodaptria was found to be more closely related to a group of lizards called Autarchoglossa, a large clade or evolutionary grouping that includes skinks, anguimorphs, and snakes. The supposedly gekkotan features seen in Myrmecodaptria may instead be characteristic of the earliest members of Scleroglossa, which split into gekkotans and autarchoglossans. Myrmecodaptria is part of the scleroglossan lineage leading to autarchoglossans, making it a "stem" autarchoglossan. Myrmecodaptria was again included in a phylogenetic analysis authored by Jack Conrad in 2008, which placed it in an extinct group called Bainguidae. Bainguidae was positioned at the stem of Autarchoglossa in the analysis (within a larger clade called Evansauria), but this relationship had only weak support. The best known member of Banguidae, Bainguis, may instead be a closer relative of living anguids or lacertoids, in which case Bainguidae would not be a valid grouping.A large phylogenetic analysis published in 2012, which resulted a very different hypothesis for the evolutionary relationships of lizards than those of previous analyses, found Myrmecodaptria to be closely related to the genus Carusia, which is also from the Late Cretaceous of Mongolia. In Conrad's 2008 analysis, Carusia was deeply nested within Autarchoglossa as a close relative of the living genus Xenosaurus. The 2012 analysis instead found that Myrmecodaptria and Carusia were close relatives of the family Scincidae, which includes modern skinks. Both genera were placed in a family called Carusiidae. While a close relationship to scincids was only weakly supported, the grouping of Myrmecodaptria and Carusia as sister taxa was strongly supported by nine shared characteristics, including fused frontals (which, according to the analysis, evolved independently in gekkotans and Carusiidae).


Pegomastax ("strong jaw") is a genus of heterodontosaurid dinosaur discovered in Lower Jurassic rocks in South Africa. It is based on SAM-PK-K10488, a partial skull including a postorbital bone, both dentaries (the tooth-bearing bone of the lower jaw), and a predentary (a toothless beak-like bone found at the tip of the lower jaw). From head to tail the parrot-like herbivore measured no more than 60 cm.

This specimen was found in Voyizane, Joe Gqabi District, Cape Province, in rocks of the upper Elliot Formation, a rock formation that dates to the early part of the Early Jurassic (Hettangian–Sinemurian, approximately 200 to 190 million years ago). It was collected during a 1966–1967 expedition but not formally named and described until 2012, when Paul Sereno, who had recognized it as unusual in the 1980s, published a description. The type species is P. africana. Pegomastax differed from other heterodontosaurids by details of the skull. The lower jaw was robust, with a short beak. Like most other heterodontosaurids, Pegomastax had an enlarged canine-like tooth at the beginning of the lower jaw's tooth row, which may have had a defensive function.

Postorbital bar

The postorbital bar (or postorbital bone) is a bony arched structure that connects the frontal bone of the skull to the zygomatic arch, which runs laterally around the eye socket . It is a trait that only occurs in mammalian taxa, such as most strepsirrhine primates and the hyrax, while haplorhine primates have evolved fully enclosed sockets. One theory for this evolutionary difference is the relative importance of vision to both orders. As haplorrhines (tarsiers and simians) tend to be diurnal, and rely heavily on visual input, many strepsirrhines are nocturnal and have a decreased reliance on visual input.Postorbital bars evolved several times independently during mammalian evolution and the evolutionary histories of several other clades. Some species, such as Tarsiers, have a postorbital septum. This septum can be considered as joined processes with a small articulation between the frontal bone, the zygomatic bone and the alisphenoid bone and is therefore different to the postorbital bar, while it forms a composite structure together with the postorbital bar. Other species such as dermopterans have postorbital processes, which is a more primitive incomplete stage of the postorbital bar.


Protoichthyosaurus is a genus of ichthyosaur from the early Jurassic of southern England. Two species are known, P. prostaxalis—the type species, named by Appleby in 1979—and P. applebyi. A third species, P. prosostealis, was named by Appleby, but it was removed from the genus in 2017 due to its similarity to Ichthyosaurus. The genus Protoichthyosaurus was synonymized with Ichthyosaurus by Maisch and Hungerbuhler in 1997, and again by Maisch and Matzke in 2000. However, it was found to be distinct in 2017 by Dean Lomax and colleagues, who separated it from Ichthyosaurus on account of differences in the arrangement and shape of the carpal ossifications, as well as the absence of the fifth digit. The species most likely lived during the Hettangian epoch, but may have lived as early as the Rhaetian and as late as the Sinemurian.Species belonging to the genus were medium-sized, with P. prostaxalis measuring no more than 2.5 metres (8 ft 2 in) in length and P. applebyi reaching 2 metres (6 ft 7 in) at most. P. prostaxalis can be distinguished from P. applebyi and from other ichthyosaurs by the large, tall, and triangular maxilla that extends beyond the nasal bones at its front end; a vertically short but thick postorbital bone; and the lacrimal bone having an upward projection longer than its forward projection. Meanwhile, P. applebyi can be distinguished by the narrow, crescent-shaped postorbital; the low maxilla; the nasal reaching to the front of the maxilla; the lacrimal having a forward projection the same length as or longer than the upward projection; and the presence of a plate-like upward projection on the humerus.The nominal species Ichthyosaurus fortimanus Owen, 1849-1884 based on the holotype forefin NHMUK R.1063 and synonymized with Ichthyosaurus communis by McGowan (1974), was referred to Protoichthyosaurus, as P. fortimanus, based on comparisons with known Ichthyosaurus and Protoichthyosaurus species.


Qianxisaurus is an extinct genus of pachypleurosaur or alternatively a basal eosauropterygian known from the Middle Triassic (Ladinian age) of Guizhou Province, southwestern China. It contains a single species, Qianxisaurus chajiangensis.


Scythosuchus is an extinct genus of rauisuchid. Remains have been found from Olenekian-age Lower Triassic beds in Russia, hence the name meaning 'Scythian crocodile'. The type and only species is S. basileus, described in 1999. Scythosuchus was between 2 and 3 metres long, and relatively heavily built. It is known from a partial skull, much of the spine, a fragment of the humerus and most of the hind leg and foot.


Slaugenhopia is an extinct genus of dvinosaurian temnospondyl within the family Tupilakosauridae. Fossils have been found from the Early Permian San Angelo Formation in Texas. The type and only species, S. texensis, was named in 1962. It may be closely related to the dvinosaur Kourerpeton. Slaugenhopia was once classified as a trimerorhachid but is now classified as a tupilakosaurid.


Texacephale is a genus of basal pachycephalosaurid dinosaur from the Campanian stage of the Late Cretaceous. The type species is Texacephale langstoni; its fossils were discovered in the Aguja Formation and described in 2010 by Longrich, Sankey and Tanke. The generic name means Texas + "head" (kephale in Greek) in reference to its place of discovery, and the specific name honors Wann Langston.


Westlothiana ("animal from West Lothian") is a genus of reptile-like tetrapod that lived about 338 million years ago during the latest part of the Visean age of the Carboniferous. Members of the genus bore a superficial resemblance to modern-day lizards. The genus is known from a single species, Westlothiana lizziae. The type specimen was discovered in the East Kirkton Limestone at the East Kirkton Quarry, West Lothian, Scotland in 1984. This specimen was nicknamed "Lizzie the lizard" by fossil hunter Stan Wood, and this name was quickly adopted by other paleontologists and the press. When the specimen was formally named in 1990, it was given the specific name "lizziae" in homage to this nickname. However, despite its similar body shape, Westlothiana is not considered a true lizard. Westlothiana's anatomy contained a mixture of both "labyrinthodont" and reptilian features, and was originally regarded as the oldest known reptile or amniote. However, updated studies have shown that this identification is not entirely accurate. Instead of being one of the first amniotes (tetrapods laying hard-shelled eggs, including synapsids, reptiles, and their descendants), Westlothiana was rather a close relative of Amniota. As a result, most paleontologists since the original description place the genus within the group Reptiliomorpha, among other amniote relatives such as diadectomorphs and seymouriamorphs. Later analyses usually place the genus as the earliest diverging member of Lepospondyli, a collection of unusual tetrapods which may be close to amniotes or lissamphibians (modern amphibians like frogs and salamanders), or potentially both at the same time.


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