Prolacerta

Last updated

Prolacerta
Temporal range: Early Triassic, Induan-Olenekian
~252–247  Ma
Ꞓ
O
S
D
C
P
T
J
K
Pg
N
↓
Prolacerta skull diagram.png
The skull of Prolacerta broomi
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauromorpha
Clade: Crocopoda
Family:† Prolacertidae
Genus:† Prolacerta
Parrington, 1935
Species:
†P. broomi
Binomial name
†Prolacerta broomi
Parrington, 1935
Synonyms
  • Pricea longicepsBroom & Robinson, 1948

Prolacerta is a genus of archosauromorph from the lower Triassic of South Africa and Antarctica. [1] The only known species is Prolacerta broomi. Prolacerta was a small and slender reptile, with a rather long neck, low skull, and serrated teeth. It would have resembled a modern monitor lizard at a quick glance, [2] though this is an example of convergent evolution as opposed to close affinities. [3]

Contents

When first discovered, Prolacerta was considered to be ancestral to modern lizards ("lacertilians"). [2] 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 (including birds). [3] Prolacerta is now understood to be one of the most well-known early members of this lineage, formally known as Archosauromorpha. Some paleontologists have previously used the term "Prolacertiformes" in reference to superficially lizard-like early archosauromorphs, though the usage of Prolacertiformes as a valid group has lost support in recent decades. Many modern paleontologists consider Prolacerta to be among the closest relatives of the Archosauriformes, an advanced group of archosauromorphs including true archosaurs. [4] [1]

History of discovery

South African fossils

Prolacerta was first described by Francis Rex Parrington in 1935 from a single skull discovered near the small town of Middelburg in the Eastern Cape of South Africa. The fossil was recovered from an exposure of rock from the Katberg Formation in the Lystrosaurus Assemblage Zone. [2] [5] This original skull, the holotype, is now stored at the Cambridge University Museum of Zoology as specimen UMZC 2003.40 [1] [6] (or UCMZ 2003.41R). [7]

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. [2]

Beyond Parrington's original skull fossil, additional skull material was slowly accumulated over the course of the mid-20th century. [8] [9] One skull, BPI 471, was originally described as a new genus and species, Pricea longiceps, by Broom and Robinson (1948). [10] Later authors concluded that Pricea was a junior synonym of Prolacerta, only distinguishable by its style of preservation. [3] As of 2018, 25 different Prolacerta specimens have been found in South Africa. One (the holotype) is accessioned at Cambridge, one at UCMP (University of California Museum of Paleontology), 7 at BPI (Bernard Price Institute for Palaeontological Research), 2 at NMQR (National Museum, Bloemfontein), 13 at SAM-PK (Iziko South African Museum), and one is yet to acquire a repository. [6]

Gow (1975) provided the most complete description of the fossil material collected and stored at BPI up to that point, establishing Prolacerta's affinities with archosaurs rather than lizards. [3] Evans (1986) described the braincase in more detail. [11] Modesto and Sues (2004) redescribed the skull as a whole, focusing on the UCMP specimen alongside 5 specimens stored at BPI. [12] The holotype skull in Cambridge was redescribed by Gabriela Sobral (2023). [7]

Antarctic fossils

Prolacerta was first reported from Antarctica by Edwin H. Colbert in 1987. The original Antarctic fossils were collected from 1969 to 1971 by James Kitching and his colleagues, working in the Fremouw Formation near the junction of the McGregor and Shackleton glaciers. [13] Colbert described 17 different Prolacerta specimens from Antarctica, all of which are stored at the American Museum of Natural History (AMNH). Most of the AMNH specimens are rather fragmentary, but two nearly complete skulls are included among the sample: AMNH 9520 and AMNH 9521. [13]

The Antarctic Prolacerta fossils were amended by Stephan Spiekman (2018), with the description of a new articulated skeleton stored at the Burke Museum of Natural History and Culture (UWBM). This specimen, UWBM 95529, is both the largest and most complete Prolacerta skeleton which has been described, though only fragments of the skull are preserved. The 2018 study re-evaluated Colbert's sample, finding that 14 of the AMNH specimens are still validly referable to Prolacerta. [6]

The AMNH fossils are distinctly smaller than the South African remains, and several anatomical differences are apparent. The AMNH fossils tend to have a shorter snout, more conical teeth, dorsal neural spines which are slanted backwards, and a proportionally shorter tibia, among other traits. Colbert preferred the hypothesis that they simply represent juvenile fossils, though he could not disprove the idea that they were from a second species which was smaller than P. broomi. [13] Some of the differences between the AMNH and South African fossils are ambiguous due to quirks of preservation and limited overlap between specimens. [6] UWBM 95529 is not only comparable in size to the South African fossils, but also anatomically indistinguishable from them. This supports the interpretation that the AMNH fossils are juveniles, while dissuading the idea that the Antarctic remains are from a dwarfed species. [6]

Description

Life restoration of Prolacerta broomi Prolacerta broomi.jpg
Life restoration of Prolacerta broomi

Prolacerta were small reptiles that lived during the Induan and Olenekian stages of the lower Triassic. Prolacerta is arguably the most well-represented stem-archosauriform, with numerous well preserved specimens housed in various research institutions in South Africa, Europe, and in the United States. With the skull of adult specimens ranging between 8 – 10 cm in length, Prolacerta were considered to have been small, lizard-like animals. However, several cranial and postcranial features set Prolacerta apart from lizards and instead show that it is an early relative of crown-archosaurs. Some of these notable features include elongated cervical vertebrae with elongate, thickened neural spines, which gave Prolacerta a slightly elongated neck and a wide range of flexibility. [14] Cranial features include thecodont teeth, a feature observed in all ancestors of crown archosaurs, which were pointed and caniniform in shape.

Prolacerta was probably a small, active, terrestrial carnivore or insectivore due to its fang-like teeth of roughly the same size and shape. Prolacerta is considered to have been a quadruped, although due to its hind limbs being larger and longer than its front limbs, there is a possibility that it was habitually bipedal during high activity. [3] It has been hypothesized that Prolacerta was capable of cranial kinesis, although research into this possible feature of Prolacerta remains inconclusive.

Classification

At the time that Parrington described the first Prolacerta fossil, the early evolutionary relationships of archosaurs was even more poorly understood than they are currently. Due to its small size and lizard-like appearance, Parrington placed Prolacerta between basal younginids and modern lizards. [2] Parrington's classification of Prolacerta was accepted for several decades, including by the paleontologist Charles Lewis Camp who conducted further research on Prolacerta. [8] [9] It was only after more Prolacerta fossils were found that more in depth research was undertaken on this animal. In the 1970s the close link between Prolacerta and crown archosaurs was first hypothesized, [3] which lead to numerous phylogenetic analyses being conducted on Prolacerta and other stem archosaurs from the 1980s onwards. [11] [13] [4] [15] [12] [16] [17]

Initially hypothesized to be ancestral to lizards, Prolacerta was later identified as an archosauromorph by Gow (1975). Gow placed it into a group known as the Prolacertiformes, which also contained "protorosaurs" such as Protorosaurus , Macrocnemus , and the long-necked tanystropheids. Macrocnemus and a few other "prolacertiforms" were allied with Prolacerta in the family Prolacertidae. [3] However, later studies starting with Dilkes (1998) have split apart the concept of Prolacertiformes, with "protorosaurs" being placed near the base of Archosauromorpha, and Prolacerta being much closer to Archosauriformes. Prolacertidae was also split by this reassessment, with Macrocnemus now considered a tanystropheid. [4] Currently, Prolacertidae is restricted to Prolacerta and its close Australian cousin Kadimakara . Prolacertids are considered to be archosauromorphs within the clade Crocopoda, along with the allokotosaurs, rhynchosaurs, and archosauriforms. [1]

The following cladogram is based on a large analysis of archosauriforms published by M.D. Ezcurra in 2016

Sauria

† Choristodera Champsosaurus BW flipped.jpg

Lepidosauromorpha British reptiles, amphibians, and fresh-water fishes (1920) (Lacerta agilis).jpg

 Archosauromorpha 

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.

<span class="mw-page-title-main">Archosauriformes</span> Clade of reptiles

Archosauriformes is a clade of diapsid reptiles encompassing archosaurs and some of their close relatives. It was defined by Jacques Gauthier (1994) as the clade stemming from the last common ancestor of Proterosuchidae and Archosauria. Phil Senter (2005) defined it as the most exclusive clade containing Proterosuchus and Archosauria. Archosauriforms are a branch of archosauromorphs which originated in the Late Permian and persist to the present day as the two surviving archosaur groups: crocodilians and birds.

<span class="mw-page-title-main">Archosauromorpha</span> Infraclass of reptiles

Archosauromorpha is a clade of diapsid reptiles containing all reptiles more closely related to archosaurs rather than lepidosaurs. Archosauromorphs first appeared during the late Middle Permian or Late Permian, though they became much more common and diverse during the Triassic period.

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

Tanystropheus is an extinct genus of archosauromorph reptile which lived during the Triassic Period in Europe, Asia, and North America. It is recognisable by its extremely elongated neck, longer than the torso and tail combined. The neck was composed of 13 vertebrae strengthened by extensive cervical ribs. Tanystropheus is one of the most well-described non-archosauriform archosauromorphs, known from numerous fossils, including nearly complete skeletons. Some species within the genus may have reached a total length of 6 meters (20 ft), making Tanystropheus the longest non-archosauriform archosauromorph as well. Tanystropheus is the namesake of the family Tanystropheidae, a clade collecting many long-necked Triassic archosauromorphs previously described as "protorosaurs" or "prolacertiforms".

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

Youngina is an extinct genus of diapsid reptile from the Late Permian Beaufort Group of the Karoo Red Beds of South Africa. This, and a few related forms, make up the family Younginidae, within the order Eosuchia. Eosuchia, having become a wastebasket taxon for many probably distantly-related primitive diapsid reptiles ranging from the Late Carboniferous to the Eocene, Romer proposed that it be replaced by Younginiformes.

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

Erythrosuchus is an extinct genus of archosauriform reptiles from the early Triassic of South Africa. Remains have been found from the Cynognathus Assemblage Zone of the Beaufort Group in the Karoo of South Africa.

<i>Proterosuchus</i> Extinct genus of reptiles from the Early Triassic of South Africa

Proterosuchus is an extinct genus of archosauriform reptiles that lived during the Early Triassic. It contains three valid species: the type species P. fergusi and the referred species P. alexanderi and P. goweri. All three species lived in what is now South Africa. The genus was named in 1903 by the South African paleontologist Robert Broom. The genus Chasmatosaurus is a junior synonym of Proterosuchus.

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

Tasmaniosaurus is an extinct genus of archosauromorph reptile known from the Knocklofty Formation of West Hobart, Tasmania, Australia. The type species is T. triassicus. This genus is notable not only due to being one of the most complete Australian Triassic reptiles known, but also due to being a very close relative of Archosauriformes. Once believed to be a proterosuchid, this taxon is now believed to have been intermediate between advanced non-archosauriform archosauromorphs such as Prolacerta, and basal archosauriforms such as Proterosuchus. Features traditionally used to define Archosauria and later Archosauriformes, such as the presence of an antorbital fenestra and serrated teeth, are now known to have evolved prior to those groups due to their presence in Tasmaniosaurus.

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.

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

Archosaurus is an extinct genus of carnivorous proterosuchid archosauriform reptile. Its fossils are dated to the latest Permian of Russia and Poland, it is one of the earliest known archosauriforms. The type and only species is Archosaurus rossicus, known from several fragmentary specimens which cumulatively represent parts of the skull and cervical vertebrae. It would have been 3 metres (9.8 ft) long when fully grown.

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

Cosesaurus is a genus of archosauromorph reptiles likely belonging to the family Tanystropheidae. It is known from fossil imprints of a single small skeleton, MGB V1, which was found in Muschelkalk outcrops near the municipalities of Mont-ral and Alcover in Spain. These outcrops are dated to the Ladinian age of the middle Triassic about 242 to 237 million years ago. The specimen is stored at the Museu Martorell, which is now part of the Museu de Ciències Naturals de Barcelona. The poor preservation and likely juvenile nature of the specimen has led to the anatomy of Cosesaurus being misidentified by several different sources. For example, Paul Ellenberger claimed that it was an ancestor to birds in the 1970s, while David Peters claimed that it was a pterosaur ancestor in 2000. Both of these claims contrast with mainstream scientific theories on the origins of either group, and other paleontologists who study the specimen are unable to find the features which Ellenberger or Peters reported to be present. The Ellenberger and Peters hypotheses are thus considered fringe theories with questionable scientific soundness due to their low reproducibility. Mainstream hypotheses for the relations of Cosesaurus generally agree that it is a "protorosaur", specifically a tanystropheid closely related to long-necked reptiles such as Macrocnemus, Tanytrachelos, Tanystropheus, or Langobardisaurus.

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

Jesairosaurus is an extinct genus of early archosauromorph reptile known from the Illizi Province of Algeria. It is known from a single species, Jesairosaurus lehmani. Although a potential relative of the long-necked tanystropheids, this lightly-built reptile could instead be characterized by its relatively short neck as well as various skull features.

<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>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.

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

Prolacertoides is an extinct genus of archosauromorph reptile from the Early Triassic of China, the type species being Prolacertoides jimusarensis. Prolacertoides means 'like Prolacerta', in reference to Prolacerta, another genus of archosauromorph which Prolacertoides was once believed to have been closely related to. Prolacertoides is known from a single partial skull, IVPP V3233, which was discovered in Xinjiang in northwestern China. The locality of its discovery belongs to the Cangfanggou Group of the Jiucaiyuan Formation, which is dated to the Induan age of the very early Triassic.

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

Aenigmastropheus is an extinct genus of early archosauromorph reptiles known from the middle Late Permian Usili Formation of Songea District, southern Tanzania. It contains a single species, Aenigmastropheus parringtoni, known solely from UMZC T836, a partial postcranial skeleton of a mature individual. It was collected in 1933, and first described in 1956, as a "problematic reptile" due to its unique morphology. Therefore, a binomial name was erected for this specimen in 2014. Aenigmastropheus was probably fully terrestrial.

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

Prolacertidae is an extinct family of archosauromorph reptiles that lived during the Early Triassic epoch. It was named in 1935 by the British palaeontologist Francis Rex Parrington to include the species Prolacerta broomi of South Africa and Antarctica. In 1979 a second species, Kadimakara australiensis, was described from Australia. Several other genera, such as Macrocnemus, Pamelaria and Prolacertoides, have also been assigned to this family in the past, but these have been placed elsewhere by later studies, leaving Prolacerta and Kadimakara as the only well-supported members.

<i>Ozimek volans</i> Extinct species of reptile

Ozimek is a genus of sharovipterygid archosauromorph reptile, known from Late Triassic deposits in Poland and closely related to the Kyrgyzstani Sharovipteryx. It contains one species, O. volans, named in 2016 by Jerzy Dzik and Tomasz Sulej. Like Sharovipteryx, Ozimek had long, slender limbs with the hindlimbs longer than the forelimbs; the hindlimbs likely supported gliding membranes as fossilized in Sharovipteryx. Another unusual characteristic was the shoulder girdle, where the massive coracoids formed a shield-like structure covering the bottom of the shoulder region that would have limited mobility. In other respects, such as its long neck, it was a typical member of the non-natural grouping Protorosauria. Phylogenetic analysis has indicated that it, possibly along with Sharovipteryx, may have been an unusual member of the protorosaur group Tanystropheidae, although further study of its anatomy is needed to resolve its precise relationships.

<i>Kadimakara australiensis</i> Extinct species of reptile

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.

Boreopricea is an extinct genus of archosauromorph reptile from the Early Triassic of arctic Russia. It is known from a fairly complete skeleton discovered in a borehole on Kolguyev Island, though damage to the specimen and loss of certain bones has complicated study of the genus. Boreopricea shared many similarities with various other archosauromorphs, making its classification controversial. Various studies have considered it a close relative of Prolacerta, tanystropheids, both, or neither. Boreopricea is unique among early archosauromorphs due to possessing contact between the jugal and squamosal bones at the rear half of the skull.

References

  1. 1 2 3 4 Ezcurra, Martín D. (2016-04-28). "The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms". PeerJ. 4: e1778. doi: 10.7717/peerj.1778 . ISSN   2167-8359. PMC   4860341 . PMID   27162705.
  2. 1 2 3 4 5 Parrington, F.R. (1935-08-01). "XVI.—On Prolacerta broomi, gen. et sp. n., and the origin of lizards". Annals and Magazine of Natural History. 16 (92): 197–205. doi:10.1080/00222933508655037. ISSN   0374-5481.
  3. 1 2 3 4 5 6 7 Gow, Chris E. (1975). "The morphology and relationships of Youngina capensis Broom and Prolacerta broomi Parrington". Palaeontologia Africana. ISSN   0078-8554.
  4. 1 2 3 Dilkes, David W. (1998-04-29). "The early Triassic rhynchosaur Mesosuchus browni and the interrelationships of basal archosauromorph reptiles". Philosophical Transactions of the Royal Society B: Biological Sciences. 353 (1368): 501–541. doi:10.1098/rstb.1998.0225. ISSN   0962-8436. PMC   1692244 .
  5. ↑ Sobral, Gabriela; Sookias, Roland B.; Bhullar, Bhart-Anjan S.; Smith, Roger; Butler, Richard J.; Müller, Johannes (2016-07-01). "New information on the braincase and inner ear of Euparkeria capensis Broom: implications for diapsid and archosaur evolution". Royal Society Open Science. 3 (7): 160072. Bibcode:2016RSOS....360072S. doi:10.1098/rsos.160072. ISSN   2054-5703. PMC   4968458 . PMID   27493766.
  6. 1 2 3 4 5 Spiekman, Stephan N. F. (2018-12-20). "A new specimen of Prolacerta broomi from the lower Fremouw Formation (Early Triassic) of Antarctica, its biogeographical implications and a taxonomic revision". Scientific Reports. 8 (1): 17996. doi:10.1038/s41598-018-36499-6. ISSN   2045-2322. PMC   6301955 .
  7. 1 2 Sobral, Gabriela (2023). "The holotype of the basal archosauromorph Prolacerta broomi revisited" (PDF). Acta Palaeontologica Polonica. 68 (3): 393–413.
  8. 1 2 Camp, Charles L. (1945-01-01). "Prolacerta and the protorosaurian reptiles; Part I". American Journal of Science. 243 (1): 17–32. Bibcode:1945AmJS..243...17C. doi:10.2475/ajs.243.1.17. ISSN   0002-9599.
  9. 1 2 Camp, Charles L. (1945-02-01). "Prolacerta and the protosaurian reptiles; Part II". American Journal of Science. 243 (2): 84–101. Bibcode:1945AmJS..243...84C. doi: 10.2475/ajs.243.2.84 . ISSN   0002-9599.
  10. ↑ Broom, R.; Robinson, J. T. (1948). "Some Now Fossil Reptiles from the Karoo Beds of South Africa". Proceedings of the Zoological Society of London. 118 (2): 392–407. doi:10.1111/j.1096-3642.1948.tb00384.x. ISSN   0370-2774.
  11. 1 2 Evans, Susan E. (1986). "The braincase of Prolacerta broomi (Reptilia, Triassic)". Neues Jahrbuch für Mineralogie - Abhandlungen Journal of Mineralogy and Geochemistry. 173 (2): 181–200.
  12. 1 2 Modesto, Sean P.; Sues, Hans-Dieter (2004-02-24). "The skull of the Early Triassic archosauromorph reptile Prolacerta broomi and its phylogenetic significance". Zoological Journal of the Linnean Society. 140 (3): 335–351. doi: 10.1111/j.1096-3642.2003.00102.x . ISSN   1096-3642.
  13. 1 2 3 4 Colbert, Edwin H. (24 June 1987). "The Triassic reptile Prolacerta in Antarctica". American Museum Novitates (2882): 1–19. hdl:2246/5211.
  14. ↑ Botha-Brink, Jennifer; Smith, Roger M. H. (2011-11-01). "Osteohistology of the Triassic archosauromorphs Prolacerta, Proterosuchus, Euparkeria, and Erythrosuchus from the Karoo Basin of South Africa". Journal of Vertebrate Paleontology. 31 (6): 1238–1254. doi:10.1080/02724634.2011.621797. ISSN   0272-4634. S2CID   130744235.
  15. ↑ Groenewald, G.H. and Kitching, J.W., 1995. Biostratigraphy of the Lystrosaurus assemblage zone. In Biostratigraphy of the Beaufort Group (Karoo Supergroup) (Vol. 1, pp. 35-39). Pretoria: Council for Geosciences.
  16. ↑ Nesbitt, Sterling J. (2011-04-29). "The Early Evolution of Archosaurs: Relationships and the Origin of Major Clades". Bulletin of the American Museum of Natural History. 352: 1–292. doi: 10.1206/352.1 . hdl:2246/6112. ISSN   0003-0090. S2CID   83493714.
  17. ↑ Ezcurra, Martín D.; Scheyer, Torsten M.; Butler, Richard J. (2014-02-27). "The Origin and Early Evolution of Sauria: Reassessing the Permian Saurian Fossil Record and the Timing of the Crocodile-Lizard Divergence". PLOS ONE. 9 (2): e89165. Bibcode:2014PLoSO...989165E. doi: 10.1371/journal.pone.0089165 . ISSN   1932-6203. PMC   3937355 . PMID   24586565.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.