Drepanosaur

Last updated

Drepanosaurs
Temporal range: Late Triassic, 230–201.3  Ma
Drepanosaurus unguicaudatus.JPG
Fossil specimen of Drepanosaurus unguicaudatus
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Neodiapsida
Clade: Drepanosauromorpha
Renesto et al., 2010
Subgroups

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. [1] The various species of drepanosaurid were characterized by specialized grasping limbs and often prehensile tails, adaptions for arboreal (tree-dwelling) and fossorial (digging) lifestyles, with some having also been suggested to be aquatic. [2] Fossils of drepanosaurs have been found in Arizona, New Mexico, New Jersey, Utah, England, and northern Italy. The name is taken from the family's namesake genus Drepanosaurus , which means "sickle lizard," a reference to their strongly curved claws.

Contents

Description

Skeletal restoration of Megalancosaurus preonensis Megalancosaurus skeletal.png
Skeletal restoration of Megalancosaurus preonensis

Drepanosaurs are notable for their distinctive, triangular skulls, which resemble the skulls of birds. Some drepanosaurs, such as Avicranium, had pointed, toothless, bird-like beaks. This similarity to birds may have led to the misattribution of what may be a drepanosaur skull to the would-be "first bird," Protoavis . [3]

Megalancosaurus preonensis restoration Megalancosaurus BW.jpg
Megalancosaurus preonensis restoration

Drepanosaurs featured a suite of bizarre, almost chameleon-like skeletal features. Above the shoulders of most species was a specialized "hump" formed from fusion of the vertebrae, possibly used for advanced muscle attachments to the neck, and allowing for quick forward-striking movement of the head (perhaps to catch insects). Many had derived hands with two fingers opposed to the remaining three, an adaptation for grasping branches. Some individuals of Megalancosaurus (possibly exclusive to either males or females) had a primate-like opposable toe on each foot, perhaps used by one sex for extra grip during mating. Most species had broad, prehensile tails, sometimes tipped with a large "claw," again to aid in climbing. These tails, tall and flat like those of newts and crocodiles, have led some researches to conclude that they were aquatic rather than arboreal. In 2004, Senter dismissed this idea, while Colbert and Olsen, in their description of Hypuronector, state that while other drepanosaurs were probably arboreal, Hypuronector was uniquely adapted to aquatic life. [4] The tail of this genus was extremely deep and non-prehensile: much more fin-like than members of the more exclusive group Drepanosauridae. [5] Aerial locomotion has been attributed to at least two drepanosaur genera: Megalancosaurus and Hypuronector . The first was originally suggested by Ruben et al. 1998 on the basis of bird-like characters and limb proportions. [6] While the suggestion has not been ruled out entirely, it has since been largely dismissed, due to Megalancosaurus' clunky, chameleon-like anatomy. [3] Hypuronector, however, is much more likely to be a glider or flyer due to the elongated forelimbs. [7] Fossorial or digging-related adaptations have been recognized in three drepanosaur genera: Skybalonyx , Ancistronychus , and Drepanosaurus. In particular, Drepanosaurus may have been adapted to hook-and-pull digging, similar to modern-day anteaters. Skybalonyx possessed claws similar in shape to modern-day moles and echidna, both of which are humeral-rotation diggers. [2]

Vallesaurus cenensis fossil Vallesaurus cenensis.JPG
Vallesaurus cenensis fossil

The phylogenetic position of drepanosaurs is highly disputed. Various studies have proposed that drepanosaurs are protorosaurian archosauromorphs, [8] lepidosauromorphs related to kuehneosaurids, [9] non-saurian diapsids related to weigeltisaurids, [4] or (most recently) basal neodiapsids. [10]

Early studies

When Drepanosaurus and Dolabrosaurus were first discovered (in 1980 and 1992, respectively), they were each considered early lepidosaurians, ancestral to modern lizards. Megalancosaurus was first believed to be athecodont (i.e. an archosauriform) upon its discovery in 1980, but later studies placed it as a prolacertiform, and perhaps even an ancestor to birds, although this latter hypothesis has not been supported by subsequent studies. [10]

Drepanosaurs outside Neodiapsida: Avicephala and Simiosauria

A 2004 study by Senter placed drepanosaurs with the coelurosauravids (weigeltisaurids) and Longisquama in a clade called which he called Avicephala. Senter's analysis placed Avicephala within Diapsida but outside Neodiapsida, defined by Senter as the clade containing "all taxa phylogenetically bracketed by Younginiformes and living diapsids." [4] [11]

Within Avicephala, Senter named the group Simiosauria ("monkey lizards") for the extremely derived tree-dwelling forms. Simiosauria was defined as "all taxa more closely related to Drepanosauridae than to Coelurosauravus or Sauria." However, Renesto and colleagues (see below) found drepanosaurids to lie within Sauria, which would make the clade Simiosauria obsolete. Senter found that Hypuronector , originally described as a drepanosaurid, actually lies just outside that clade, along with the primitive drepanosaur Vallesaurus . He also recovered a close relationship between the drepanosaurids Dolabrosaurus and Megalancosaurus . [4]

The following cladogram was proposed by Senter in his 2004 analysis: [4]

Simiosauria

Vallesaurus

unnamed

Hypuronector

Drepanosauridae

Drepanosaurus

unnamed

Dolabrosaurus

Megalancosaurus

A clade containing drepanosaurids, Longisquama, and Coelurosauravus (as well as Wapitisaurus ) was also recovered in a 2003 analysis conducted by John Merck; however, in Merck's analysis this clade was nested within Neodiapsida as the sister taxon of Sauria. [12]

Drepanosaurus unguicaudatus restoration Drepanosaurus unguicaudatus on a branch.jpg
Drepanosaurus unguicaudatus restoration

In a 2006 study, Renesto and Binelli found that when pterosaur Eudimorphodon was added to Senter's original matrix, it was found to be a member of Avicephala. [13] The authors also conducted a second analysis, this time based on a character set and matrix updated by scoring additional characters previously reported as unknown and by adding a few relevant characters. This analysis recovered drepanosaurids as the sister taxon of Eudimorphodon; the clade containing pterosaurs and drepanosaurids was recovered as the sister taxon of Archosauriformes. Longisquama and Coelurosauravus were not found to be closely related to drepanosaurids, but instead were recovered as non-neodiapsid diapsids as in Senter's analysis. However, it is feasible that this arrangement might be a result of poor knowledge of Longisquama rather than a reflection of its true phylogenetic position. The authors did note that there are similarities in the structure of the forelimb and shoulder regions of Longisquama and all or some drepanosaurids (e.g. the humerus of both Longisquama and Vallesaurus is as long as the fourth digit of the manus). They stressed that they could not rule out the possibility that at least some of the similarities are convergent due to a similar behaviors, and that they did not examine Longisquama firsthand. Therefore, further studies of drepanosaurids should take the hypothesis that Longisquama might be a drepanosaurid into consideration. [13]

Drepanosaurs as relatives of kuehneosaurids

Drepanosaurids were also found to be non-saurian neodiapsids in a 2004 analysis conducted by Johannes Müller; however, in this analysis Drepanosauridae were not found to be closely related to Coelurosauravus , but rather were recovered as the sister taxon of Kuehneosauridae. [14] In a 2009 study, Susan E. Evans conducted a phylogenetic analysis using a modified version of Müller's matrix. Evans also recovered Drepanosauridae as the sister taxon of the clade containing basal kuehneosaurid Pamelina and the rest of Kuehneosauridae; however, unlike Müller's analysis, drepanosaurids and kuehneosaurids were recovered as non-lepidosaurian lepidosauromorphs. Evans did note that the two families share few synapomorphies, with Müller citing only two. One of them is the increased angulation of the zygapophyses in the posterior dorsal vertebrae; Evans noted that this character is also present in the skeletons of lizards belonging to the modern genus Draco "and is likely to be functional (and thus potentially convergent)." The other synapomorphy, the enclosed thyroid fenestra in the pelvis, "may be variable in the British kuehneosaurs and remains unknown in Pamelina," according to Evans. The author also noted that there are many differences between the skulls of drepanosaurids and kuehneosaurids, and that the only skull characters shared by members of both families are primitive neodiapsid characters and thus cannot be used to support a close relationship between the two clades. [9]

Drepanosaurs as archosauromorphs and the abandonment of Avicephala

In 1998, Dilkes argued that drepanosaurs were close relatives of tanystropheids, and his phylogenetic analysis has been used by many other authors. [8] Gottmann-Quesada and Sander (2009) included one member of Drepanosauridae, Megalancosaurus, in their analysis of archosauromorph relationships; it was found to be one of the most basal known members of Archosauromorpha and the sister taxon of Protorosaurus . [15]

In a later study, Renesto et al. [1] demonstrated that Senter's 2004 cladogram was based on poorly defined characters and data. The resulting phylogeny was therefore very unusual compared to any other previous study on drepanosaurs or related taxa. The new cladogram proposed in this last study abandoned both Avicephala (because it was polyphyletic) and Simiosauria. Senter's definition of Simiosauria included Sauria as an external specifier, causing the clade to become obsolete in Renesto et al.'s study (where drepanosaurs nested within Sauria). Renesto and colleagues instead defined a new clade, Drepanosauromorpha, as the least inclusive clade containing Hypuronector limnaios and Megalancosaurus preonensis. A more inclusive taxon, Elyurosauria ("lizard with coiled tail"), was erected in order to include all the drepanosaurs with coiled tails. Vallesaurus is thus more derived than Hypuronector (as shown by its morphology). Drepanosaurus and Megalancosaurus were also placed in a new taxon named Megalancosaurinae.

The alternative cladogram presented in Renesto et al. (2010). [1]

Drepanosauromorpha

Hypuronector

Elyurosauria

Vallesaurus

Drepanosauridae

Dolabrosaurus

Megalancosaurinae

Drepanosaurus

Megalancosaurus

Renesto et al. (2010) used modified versions of the matrices from the earlier analyses of Laurin (1991) [16] and Dilkes (1998) [8] in order to determine the phylogenetic position of Drepanosauromorpha within Diapsida. The analyses using Laurin's matrix recovered drepanosaurs either as the sister group of the clade containing Prolacerta , Trilophosaurus and Hyperodapedon , (Archosauromorpha), or in unresolved polytomy with Archosauromorpha and Lepidosauromorpha. The analyses using Dilkes' matrix recovered drepanosaurs either as "protorosaur" archosauromorphs and the sister taxon to the clade containing Tanystropheus , Langobardisaurus and Macrocnemus , or in unresolved polytomy with Lepidosauromorpha, Choristodera and several archosauromorph clades. Renesto et al. (2010) concluded that avicephalan synapomorphies proposed by Senter (2004) are merely evolutionary convergences caused by common lifestyle shared by drepanosaurids, coelurosauravids and Longisquama. The authors did not rule out the possibility that drepanosaurs and Longisquama might really be close relatives. [1]

Drepanosaurs as basal diapsids

In 2017, Pritchard and Nesbitt employed a phylogenetic analysis in their description of Avicranium, a new genus of drepanosaur. This study found that Drepanosauromorpha was one of the earliest diverging groups of diapsids in the analysis, even more basal than weigeltisaurids (such as Coelurosauravus ), tangasaurids (such as Hovasaurus ), and younginids (such as Youngina ). However, they were not found to be as basal as Petrolacosaurus , one of the earliest and most primitive diapsids known. Although drepanosaurs are only known from the late Triassic, this new finding suggests that the first members of the drepanosauromorph lineage may have evolved much earlier, in the Permian (about 260 million years ago). [10]

Related Research Articles

<i>Dinocephalosaurus</i> Extinct genus of reptiles

Dinocephalosaurus is a genus of long necked, aquatic protorosaur that inhabited the Triassic seas of China. The genus contains the type and only known species, D. orientalis, which was named by Chun Li in 2003. Unlike other long-necked protorosaurs, Dinocephalosaurus convergently evolved a long neck not through elongation of individual neck vertebrae, but through the addition of neck vertebrae that each had a moderate length. As indicated by phylogenetic analyses, it belonged in a separate lineage that also included at least its closest relative Pectodens, which was named the Dinocephalosauridae in 2021. Like tanystropheids, however, Dinocephalosaurus probably used its long neck to hunt, utilizing the fang-like teeth of its jaws to ensnare prey; proposals that it employed suction feeding have not been universally accepted. It was probably a marine animal by necessity, as suggested by the poorly-ossified and paddle-like limbs which would have prevented it from going ashore.

<i>Protorosaurus</i> Extinct genus of reptiles

Protorosaurus is an extinct genus of reptile. Members of the genus lived during the late Permian period in what is now Germany and Great Britain. Once believed to have been an ancestor to lizards, Protorosaurus is now known to be one of the oldest and most primitive members of Archosauromorpha, the group that would eventually lead to archosaurs such as crocodilians and dinosaurs.

<span class="mw-page-title-main">Rhynchosaur</span> Extinct order of reptiles

Rhynchosaurs are a group of extinct herbivorous Triassic archosauromorph reptiles, belonging to the order Rhynchosauria. Members of the group are distinguished by their triangular skulls and elongated, beak like premaxillary bones. Rhynchosaurs first appeared in the Early Triassic, reaching their broadest abundance and a global distribution during the Carnian stage of the Late Triassic.

<i>Elachistosuchus</i> Extinct genus of reptiles

Elachistosuchus is an extinct genus of neodiapsid reptile, most likely basal archosauromorph, known from the Late Triassic Arnstadt Formation of Saxony-Anhalt, central Germany. It contains a single species, Elachistosuchus huenei, known from a single individual E. huenei, originally considered a pseudosuchian archosaur and then a rhynchocephalian lepidosaur, was largely ignored in the scientific literature, as its small size and fragility did not permit further mechanical preparation and examination. More recently however, a non-invasive μCT scanning was performed to resolve its placement within Reptilia, and found it to represent a more basal reptile, potentially closely related to several early archosauromorph clades.

<span class="mw-page-title-main">Avicephala</span> Extinct clade of neodiapsid reptiles

Avicephala is a potentially polyphyletic grouping of extinct diapsid reptiles that lived during the Late Permian and Triassic periods characterised by superficially bird-like skulls and arboreal lifestyles. As a clade, Avicephala is defined as including the gliding weigeltisaurids and the arboreal drepanosaurs to the exclusion of other major diapsid groups. This relationship is not recovered in the majority of phylogenetic analyses of early diapsids and so Avicephala is typically regarded as an unnatural grouping. However, the clade was recovered again in 2021 in a redescription of Weigeltisaurus, raising the possibility that the clade may be valid after all.

<i>Hovasaurus</i> Extinct genus of reptiles

Hovasaurus is an extinct genus of basal diapsid reptile. It lived in what is now Madagascar during the Late Permian and Early Triassic, being a survivor of the Permian–Triassic extinction event and the paleontologically youngest member of the Tangasauridae. Fossils have been found in the Permian Lower and Triassic Middle Sakamena Formations of the Sakamena Group, where it is amongst the commonest fossils. Its morphology suggests an aquatic ecology.

<i>Megalancosaurus</i> Extinct genus of reptiles

Megalancosaurus is a genus of extinct reptile from the Late Triassic Dolomia di Forni Formation and Zorzino Limestone of northern Italy, and one of the best known drepanosaurids. The type species is M. preonensis; a translation of the animal's scientific name would be "long armed reptile from the Preone Valley."

<i>Hypuronector</i> Extinct genus of reptiles

Hypuronector is a genus of extinct drepanosaur reptile from the Late Triassic Lockatong Formation of New Jersey. The etymology of the name translates as "deep-tailed swimmer from the lake", in reference to its assumed aquatic habits hypothesized by its discoverers. Hypuronector was related to the arboreal Megalancosaurus. It was a small animal, estimated to be only 12 cm (4.7 in) long in life. So far dozens of specimens of Hypuronector are known, though scientists have not found any complete skeletons. This makes attempts to reconstruct Hypuronector's body or lifestyle highly speculative and controversial.

<i>Drepanosaurus</i> Extinct genus of reptiles

Drepanosaurus is a genus of arboreal (tree-dwelling) reptile that lived during the Triassic Period. It is a member of the Drepanosauridae, a group of diapsid reptiles known for their prehensile tails. Drepanosaurus was probably an insectivore, and lived in a coastal environment in what is now modern day Italy, as well as in a streamside environment in the midwestern United States.

<i>Mecistotrachelos</i> Extinct genus of reptiles

Mecistotrachelos is an extinct genus of gliding reptile from the Late Triassic of Virginia. It is generally interpreted as an archosauromorph, distantly related to crocodylians and dinosaurs. The type and only known species is M. apeoros. This specific name translates to "soaring longest neck", in reference to its gliding habits and long neck. This superficially lizard-like animal was able to spread its lengthened ribs and glide on wing-like membranes. Mecistotrachelos had a much longer neck than other gliding reptiles of the Triassic such as Icarosaurus and Kuehneosaurus. It was probably an arboreal insectivore.

<i>Vallesaurus</i> Extinct genus of reptiles

Vallesaurus is an extinct genus of Late Triassic elyurosaur drepanosauromorph. First found in Northern Italy in 1975, it is one of the most primitive drepanosaurs. V. cenenis is the type species, which was first mentioned in 1991 but only formally described in 2006. A second species, V. zorzinensis, was named in 2010.

Langobardisaurus is an extinct genus of tanystropheid archosauromorph reptile, with one valid species, L. pandolfii. Its fossils have been found in Italy and Austria, and it lived during the Late Triassic period, roughly 228 to 201 million years ago. Langobardisaurus was initially described in 1994, based on fossils from the Calcare di Zorzino Formation in Northern Italy. Fossils of the genus are also known from the Forni Dolostone of Northern Italy and the Seefeld Formation of Austria.

<span class="mw-page-title-main">Kuehneosauridae</span> Extinct family of reptiles

Kuehneosauridae is an extinct family of small, lizard-like gliding diapsids known from the Triassic period of Europe and North America.

<span class="mw-page-title-main">Weigeltisauridae</span> Extinct family of reptiles

Weigeltisauridae is a family of gliding neodiapsid reptiles that lived during the Late Permian, between 259.51 and 251.9 million years ago. Fossils of weigeltisaurids have been found in Madagascar, Germany, Great Britain, and Russia. 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, as well as living gliding lizards, although each group evolved these structures independently.

<span class="mw-page-title-main">Protorosauria</span> Extinct order of reptiles

Protorosauria is an extinct, likely paraphyletic group of basal archosauromorph reptiles from the latest Middle Permian to the end of the Late Triassic of Asia, Europe and North America. It was named by the English anatomist and paleontologist Thomas Henry Huxley in 1871 as an order, originally to solely contain Protorosaurus. Other names which were once considered equivalent to Protorosauria include Prolacertiformes and Prolacertilia.

<i>Prolacerta</i> Extinct genus of reptile from the lower Triassic

Prolacerta is a genus of archosauromorph from the lower Triassic of South Africa and Antarctica. The only known species is Prolacerta broomi. The generic name Prolacerta is derived from Latin meaning “before lizard” and its species name broomi is in commemoration of the famous paleontologist Robert Broom, who discovered and studied many of the fossils found in rocks of the Karoo Supergroup. When first discovered, Prolacerta was considered to be ancestral to modern lizards, scientifically known as lacertilians. However, a study by Gow (1975) instead found that it shared more similarities with the lineage that would lead to archosaurs such as crocodilians and dinosaurs. Prolacerta is considered by modern paleontologists to be among the closest relatives of the Archosauriformes.

<i>Pamelaria</i> Extinct genus of reptiles

Pamelaria is an extinct genus of allokotosaurian archosauromorph reptile known from a single species, Pamelaria dolichotrachela, from the Middle Triassic of India. Pamelaria has sprawling legs, a long neck, and a pointed skull with nostrils positioned at the very tip of the snout. Among early archosauromorphs, Pamelaria is most similar to Prolacerta from the Early Triassic of South Africa and Antarctica. Both have been placed in the family Prolacertidae. Pamelaria, Prolacerta, and various other Permo-Triassic reptiles such as Protorosaurus and Tanystropheus have often been placed in a group of archosauromorphs called Protorosauria, which was regarded as one of the most basal group of archosauromorphs. However, more recent phylogenetic analyses indicate that Pamelaria and Prolacerta are more closely related to Archosauriformes than are Protorosaurus, Tanystropheus, and other protorosaurs, making Protorosauria a polyphyletic grouping.

<span class="mw-page-title-main">Azendohsauridae</span> Extinct family of reptiles

Azendohsauridae is a family of allokotosaurian archosauromorphs that lived during the Middle to Late Triassic period, around 242-216 million years ago. The family was originally named solely for the eponymous Azendohsaurus, marking out its distinctiveness from other allokotosaurs, but as of 2022 the family now includes four other genera: the basal genus Pamelaria, the large horned herbivore Shringasaurus, and two carnivorous genera grouped into the subfamily-level subclade Malerisaurinae, Malerisaurus and Puercosuchus, and potentially also the dubious genus Otischalkia. Most fossils of azendohsaurids have a Gondwanan distribution, with multiple species known across Morocco and Madagascar in Africa as well as India, although fossils of malerisaurine azendohsaurids have also been found in the southwestern United States of North America.

<i>Avicranium</i> Extinct genus of reptiles

Avicranium is a genus of extinct drepanosaur reptile known from the Chinle Formation of the late Triassic. The type species of Avicranium is Avicranium renestoi. "Avicranium" is Latin for "bird cranium", in reference to its unusual bird-like skull, while "renestoi" references Silvio Renesto, a paleontologist known for studies of Italian drepanosaurs.

<span class="mw-page-title-main">Dinocephalosauridae</span> Extinct clade of reptiles

Dinocephalosauridae is an extinct clade of marine and terrestrial archosauromorph reptiles that lived throughout the Triassic period. Like tanystropheids, they are characterized by their long necks, lengthened by either addition of cervical vertebrae or elongation of the individual bones.

References

  1. 1 2 3 4 Renesto, S.C.; Spielmann, J.A.; Lucas, S.G. (2009-05-29). "The oldest record of drepanosaurids (Reptilia, Diapsida) from the Late Triassic (Adamanian Placerias Quarry, Arizona, USA) and the stratigraphic range of the Drepanosauridae". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. 252 (3): 315–325. doi:10.1127/0077-7749/2009/0252-0315. ISSN   0077-7749.
  2. 1 2 Jenkins, X.A.; Pritchard, A.C.; Marsh, A.D.; Kligman, B.T.; Sidor, C.A.; Reed, K.E. (2020-10-08). "Using manual ungual morphology to predict substrate use in the Drepanosauromorpha and the description of a new species". Journal of Vertebrate Paleontology. 40 (5): e1810058. doi:10.1080/02724634.2020.1810058. ISSN   0272-4634. S2CID   225136171.
  3. 1 2 Renesto, S. (2000-07-31). "Bird-like head on a chameleon body: New specimens of the enigmatic diapsid reptile Megalancosaurus from the Late Triassic of Northern Italy". Rivista italiana di Paleontologia e Stratigrafia. 106 (2): 157–179. doi:10.13130/2039-4942/5396.
  4. 1 2 3 4 5 Senter, P. (2004). "Phylogeny of Drepanosauridae (Reptilia: Diapsida)". Journal of Systematic Palaeontology. 2 (3): 257–268. doi:10.1017/s1477201904001427. ISSN   1477-2019. S2CID   83840423.
  5. Colbert, E.H.; Olsen, P.E. (2001-06-22). "A New and Unusual Aquatic Reptile from the Lockatong Formation of New Jersey (Late Triassic, Newark Supergroup)". American Museum Novitates (3334): 1–24. doi:10.1206/0003-0082(2001)334<0001:anauar>2.0.co;2. ISSN   0003-0082. S2CID   17294610.
  6. Schoch, R.R. (2007-11-29). "Osteology of the small archosaur Aetosaurus from the Upper Triassic of Germany". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. 246 (1): 1–35. doi:10.1127/0077-7749/2007/0246-0001. ISSN   0077-7749.
  7. Renesto, S.; Spielmann, J.A.; Lucas, S.G.; Spagnoli, G.T. (2010). The taxonomy and paleobiology of the Late Triassic (Carnian-Norian: Adamanian-Apachean) drepanosaurs (Diapsida: Archosauromorpha: Drepanosauromorpha). Albuquerque, NM, US: New Mexico Museum of Natural History and Science. OCLC   550640808.
  8. 1 2 3 Dilkes, D.M. (1998). "The Early Triassic rhynchosaur Mesosuchus browni and the interrelationships of basal archosauromorph reptiles". Philosophical Transactions of the Royal Society of London, Series B. 353 (1368): 501–541. doi:10.1098/rstb.1998.0225. PMC   1692244 .
  9. 1 2 Evans, S.E. (2009). "An early kuehneosaurid reptile from the Early Triassic of Poland" (PDF). Palaeontologia Polonica. 65: 145–178.
  10. 1 2 3 Pritchard, A.C.; Nesbitt, S.J. (2017-10-01). "A bird-like skull in a Triassic diapsid reptile increases heterogeneity of the morphological and phylogenetic radiation of Diapsida". Royal Society Open Science. 4 (10): 170499. Bibcode:2017RSOS....470499P. doi:10.1098/rsos.170499. ISSN   2054-5703. PMC   5666248 . PMID   29134065.
  11. Renesto, S. (1994-03-31). "Megalancosaurus, a possibly arboreal archosauromorph (Reptilia) from the Upper Triassic of northern Italy". Journal of Vertebrate Paleontology. 14 (1): 38–52. doi:10.1080/02724634.1994.10011537. ISSN   0272-4634.
  12. Merck, J. (2003). "An arboreal radiation of non-saurian diapsids". Journal of Vertebrate Paleontology. 23 (Supplement to 3): 78A. doi:10.1080/02724634.2003.10010538. S2CID   220410105.
  13. 1 2 Renesto, S.; Binelli, G. (2006-03-31). "Vallesaurus cenensis WILD, 1991, a drepanosaurid (Reptilia, Diapsida) from the Late Triassic of northern Italy". Rivista italiana di Paleontologia e Stratigrafia. 112 (1): 77–94. doi:10.13130/2039-4942/5851.
  14. Müller, J. (2004). "The relationships among diapsid reptiles and the influence of taxon selection". In Arratia, G.; Wilson, M.V.H.; Cloutier, R. (eds.). Recent Advances in the Origin and Early Radiation of Vertebrates. Verlag Dr. Friedrich Pfeil. pp. 379–408. ISBN   978-3-89937-052-2.
  15. Gottmann-Quesada, A.; Sander, P.M. (2009-03-19). "A redescription of the early archosauromorph Protorosaurus speneri MEYER, 1832, and its phylogenetic relationships". Palaeontographica Abteilung A. 287 (4–6): 123–220. doi:10.1127/pala/287/2009/123.
  16. Laurin, M. (1991). "The osteology of a Lower Permian eosuchian from Texas and a review of diapsid phylogeny". Zoological Journal of the Linnean Society. 101 (1): 59–95. doi:10.1111/j.1096-3642.1991.tb00886.x.