Acerosodontosaurus

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Acerosodontosaurus
Temporal range: Late Permian, 260–252  Ma
Acerosodontosaurus color coded skull diagram.png
Skull diagram
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Family:† Tangasauridae
Genus:† Acerosodontosaurus
Currie 1980
Type species
†Acerosodontosaurus piveteaui

Acerosodontosaurus is an extinct genus of neodiapsid reptiles that lived during the Late Permian of Madagascar. [1] [2] The only species of Acerosodontosaurus, A. piveteaui, is known from a natural mold of a single partial skeleton including a crushed skull and part of the body and limbs. The fossil was discovered in deposits of the Lower Sakamena Formation. Based on skeletal characteristics, it has been suggested that Acerosodontosaurus individuals were at least partially aquatic. [2]

Contents

Acerosodontosaurus has generally been considered a "younginiform", part of a paraphyletic grade of Permian diapsids which linked the most basal ("primitive") diapsids (araeoscelidians such as Petrolacosaurus ) to more derived ("advanced") diapsids, including the earliest ancestors of modern reptiles such as crocodilians and lizards (Sauria). [2] However, its position within the grade is controversial. Initially considered a specimen of the contemporaneous Tangasaurus , Acerosodontosaurus was later described as a younginid in 1980 [1] and a tangasaurid in 2009. [2] More recent studies have even supported the hypothesis that it was not a "younginiform" at all, but rather that it was an early member of Pantestudines, the reptile lineage that would lead to modern turtles. [3] [4] However, this theory is still controversial, [5] and other studies have continued to support the "younginiform" interpretation. [6]

History

Acerosodontosaurus is known from a single specimen stored at the Museum National d'Histoire Naturalle in Paris, France. This specimen, MNHN 1908-32-57, was referred to Tangasaurus and stayed undescribed until Phillip J. Currie recognized it as a new genus. He described it as Acerosodontosaurus piveteaui in 1980, a name which roughly translates to "Piveteau's needle-toothed lizard". The specific name references Jean Piveteau, a paleontologist who pioneered the study of Permian reptiles of Madagascar. [1]

The specimen was extracted from an unknown locality in the Lower Sakamena Formation, an Upper Permian geological formation in Madagascar. The Sakamena Formation was formed by coastal rift valleys, and can be characterized by a diverse assortment of aquatic, semiaquatic, and terrestrial animals, including many early diapsids. The Acerosodontosaurus specimen is a partial skeleton preserved as a compression fossil within a sandstone nodule. The skeleton is mostly but not entirely articulated, preserving most of the trunk, right forelimb, and small portions of the left forelimb and hindlimbs. Bones on the left side of the skull were displaced as the animal decayed, but the majority of the right side was able to fossilize. [1]

Most of the actual fossilized bones had been eroded away once the specimen was found, although well-preserved molds were left behind in the sandstone. Currie's description was based on latex casts made from the molds. [1] During a 2009 redescription by Constanze Bickelmann, Johannes Mueller, & Robert R. Reisz, new high-fidelity latex molds were created using improved techniques. [2]

Description

Life restoration by Nobu Tamura Acerosodontosaurus BW.jpg
Life restoration by Nobu Tamura

The preserved skeleton was about 30 centimeters (12 inches) in length from the tip of the snout to the base of the tail. The tail is unknown, but Currie (1980) estimated that the total length of the animal from snout to tail tip would have been 60 to 70 centimeters (24 to 28 inches). The body was wide and the limbs were of medium length. The overall impression was that of a medium-sized lizard, although Acerosodontosaurus is completely unrelated to true modern lizards. [1] Although the tail is unknown, it could have had a fin-like structure similar to that of Hovasaurus , which has been considered a close relative of Acerosodontosaurus. [2]

Skull

The tip and upper side of the snout were not preserved, but most of the other skull bones are known. The orbits (eye holes) were large, and the skull was longer in front of the eyes than behind them. The lower edge of each orbit was formed by a long forward branch of the jugal bone, which overlies an equally elongated rear branch of the tooth-bearing maxillary bone. The skull was somewhat broader than that of most other "younginiforms", as indicated by the width and curvature of the frontal and prefrontal bones. Nevertheless, it was proportionally similar to that of Hovasaurus. [7] The skull had an estimated total length of 55 millimeters (2.2 inches). [1]

The mandible (lower jaw) was long and slender. The rear part of the mandible, which was formed by the articular bone, bears a facet which connects to the quadrate bone of the cranium to form the jaw joint. Both the quadrate and the corresponding facet on the mandible are very large and strongly built. [2]

The numerous teeth of Acerosodontosaurus are conical, sharply pointed, and somewhat recurved. They are slightly longer towards the front of the skull, but otherwise are similar in size and shape throughout the skull and jaw, in contrast to the condition in earlier diapsids like Petrolacosaurus. Currie (1980) estimated that 37 teeth were present in the maxilla and 32 were in the preserved portion of the mandible, based on both preserved teeth and empty tooth sockets. [1] Under the same criteria but using different latex casts, Bickelmann, Mueller, & Reisz (2009) estimated 36 and 34, respectively. [2] The mandible would have had many more teeth than these estimations, since the front half of the jaw was not preserved. Acerosodontosaurus translates to "Needle-tooth lizard", referring to its high number of needle-like teeth which differ from those of other "younginiforms" in both shape and abundance. [1]

As a diapsid, Acerosodontosaurus had two holes known as temporal fenestrae on each side of the skull, behind the eyes. However, the lower temporal fenestra was not completely enclosed from below. In most early diapsids, such as Petrolacosaurus and Youngina , the lower edge of the lower temporal fenestra is formed by a bony bar composed of the rear branch of the jugal and the forward branch of the quadratojugal bone. Yet Acerosodontosaurus has a short rear branch of the jugal, and is completely missing a quadratojugal, rendering the lower temporal fenestra incompletely enclosed. While many later diapsids also have an incomplete lower temporal fenestra, the only other "younginiform" with such a trait is Hovasaurus. [2]

Vertebrae and ribs

At least 21 vertebrae were present, all from the neck, back, and hip; the tail is missing. The cervical (neck) vertebrae had shorter centra (main components) than the dorsal (back) vertebrae. A small pit (subcentral foramen) was present on both the left and right sides of each vertebral centrum. The neural spines (spinous processes) of the dorsal vertebrae are characteristically tall and rectangular compared to most "younginiforms", though not quite as tall as those of Hovasaurus. The centra are at their maximum length and the neural spines are at their maximum height at the vertebrae directly in front of the hip. The transverse processes (rib facets) were quite short. Although many ribs are incomplete, those that were mostly complete were long and curved, indicating that Acerosodontosaurus was a rather wide-bodied animal. As with most early diapsids, small wedge-like bones known as intercentra fill in the gaps between vertebrae. Numerous small, slender gastralia (belly ribs) were also present. [1] [2]

Forelimbs

The forelimbs of Acerosodontosaurus are among the most diagnostic parts of the body. The only preserved portion of the pectoral girdle is a thin, slightly curved bone with tapered tips. This is likely a cleithrum, a bone which is absent in practically all diapsids. The only other neodiapsid known with certainty to retain a cleithrum is Hovasaurus. [2]

The humerus (forearm bone) is incomplete, but the entepicondyle and its corresponding foramen are rather well-developed. The capitulum and trochlea, on the other hand, are poorly differentiated. [2] The radius is twisted and curved, unusually similar to that of the choristodere Champsosaurus . The ulna is hourglass-shaped, straighter and characteristically slightly longer than the radius. Unlike in terrestrial diapsids, the olecranon process of the ulna was absent. Both the radius and ulna were flatter near the wrist and more blocky near the elbow. [1]

As with other early diapsids, Acerosodontosaurus had 11 carpal (wrist) bones. All of the carpals are well-separated. Most are similar in size and shape to those of Hovasaurus, with the exception of the medial centrale, a bone between the radiale and distal carpal I which is much smaller in Acerosodontosaurus. The first metacarpal (the hand bone which connects to the thumb) is small and stout, while the second, third, and fourth (which connect to the index, middle, and ring fingers) are incrementally longer. This contrasts with most other "younginiforms", in which the fourth metacarpal is significantly longer than the third. Hovasaurus is an exception, but even Acerosodontosaurus differs from that genus in that its metacarpals are not as short. The fifth metacarpal (which connects to the little finger) is as short as the first, but has a more "pinched" appearance. Some phalanges (finger bones) are obscured by the overlain skull, but those that are visible are short, with sharp and curved claws. [1] [2]

Hip and hindlimbs

The ilium (upper blade of the hip) is fairly similar to that of Hovasaurus and other reptiles, though seemingly slightly thicker. The pubis (forward blade of the hip) is a heavily built bone, strongly curving inwards. As a result, the hips would have been quite wide in life. The outer surface of each pubis has a large, diagonally-oriented tubercule (knob- or ridge-like growth). The plate-like ischium (rear-blade of the hip) is incomplete and was initially overlooked. The femur (thigh bone) is long, curved, and robust, while the tibia and fibula (shin bones) are only preserved near the knee so their form is difficult to determine. No foot bones are preserved. [1] [2]

Classification

Initially considered a specimen of Tangasaurus, Currie (1980) subsequently assigned Acerosodontosaurus to the family Younginidae. [1] The next year, his study of Hovasaurus noted that Acerosodontosaurus shared similarities with both tangasaurids and younginids, and he considered it ancestral to both families. [7] Other studies found a similar result, placing it as the most basal member of "Younginiformes". [8] The 2009 redescription of the genus partially deconstructed the concept of a monophyletic "Younginiformes" and assigned it to Tangasauridae. [2] The 2011 description of the basal neodiapsid Orovenator considered tangasaurids to be stemward (further from modern reptiles) compared to younginids, [9] while a 2016 study of archosauromorphs placed Acerosodontosaurus crownward (closer to modern reptiles) compared to Youngina. [10]

Bever et al. (2015) analyzed Acerosodontosaurus alongside other neodiapsids via both maximum parsimony and Bayesian analyses, and cranial-only vs full body data. Their full specimen parsimony analysis found that it was a pantestudine lepidosauromorph related to sauropterygians, Eunotosaurus , Odontochelys , and Pappochelys. This result argues that Acerosodontosaurus was more closely related to turtles than to any other modern reptile, and that turtles were more closely related to lizards and kin (lepidosaurs) than to crocodilians and birds (archosaurs). Their cranial-only parsimony analysis matrix retained Acerosodontosaurus's identity as a basal pantestudine but removed Pantestudines from Sauria (the lepidosauromorph + archosauromorph clade). The link between Acerosodontosaurus and turtles was more tenuous in the Bayesian analyses, where it was placed as a neodiapsid closely related to Sauria but independent from Pantestudines. [3]

During their redescription of Pappochelys, Schoch & Sues (2018) revised the matrix of Bever et al. (2015) but failed to resolve the relations of most reptile lineages near the base of Sauria, including Acerosodontosaurus. [11] Li et al. (2018) described the new pantestudine Eorhynchochelys and revised Schoch & Sues (2018)'s data matrix further. They were able to find more stability, recovering Acerosodontosaurus as the sister taxon of Claudiosaurus and not closely related to Hovasaurus. Acerosodontosaurus and Claudiosaurus were still indeterminate neodiapsids if all taxa were included, but they were found to be the earliest pantestudines under a specific set of parameters which excluded 21 poorly-described taxa. [4]

Paleobiology

Several skeletal features support the hypothesis that Acerosodontosaurus was aquatic. The olecranon process of the ulna was absent (or not developed into bone), a trait in common with the aquatic nothosaurs, ichthyosaurs, and thalattosaurs, but in contrast to terrestrial reptiles such as Thadeosaurus . Moreover, the radius is twisted (similarly to that of the aquatic champsosaurs), and the wrist has a "relaxed" structure, with the carpals (wrist bones) separated by gaps rather than tightly connected. [2]

Paleoenvironment

The Lower Sakamena Formation was deposited in a wetland environment situated within a North-South orientated rift valley, perhaps similar to Lake Tanganyika. The climate at the time of deposition was temperate, warm, and humid, with seasonal rainfall and possible monsoons. [12] Flora from the formation includes the equisetalean Schizoneura , the glossopterid gymnosperm Glossopteris , and seed fern Lepidopteris. Other vertebrates known from the Lower Sakamena Formation include the palaeoniscoid fish Atherstonia , the procolophonid parareptile Barasaurus , the gliding reptile Coelurosauravus , the neodiapsids Hovasaurus, Claudiosaurus, Thadeosaurus fragments of rhinesuchid temnospondyls, an indeterminate theriodont therapsid and the dicynodont Oudenodon . [13]

Related Research Articles

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Diapsids are a clade of sauropsids, distinguished from more primitive eureptiles by the presence of two holes, known as temporal fenestrae, in each side of their skulls. The group first appeared about three hundred million years ago during the late Carboniferous period. All diapsids other than the most primitive ones in the clade Araeoscelidia are sometimes placed into the clade Neodiapsida. The diapsids are extremely diverse, and include birds and all modern reptile groups, including turtles, which were historically thought to lie outside the group. Although some diapsids have lost either one hole (lizards), or both holes, or have a heavily restructured skull, they are still classified as diapsids based on their ancestry. At least 17,084 species of diapsid animals are extant: 9,159 birds, and 7,925 snakes, lizards, tuatara, turtles, and crocodiles.

The quadratojugal is a skull bone present in many vertebrates, including some living reptiles and amphibians.

<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.

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

Neodiapsida is a clade, or major branch, of the reptilian family tree, typically defined as including all diapsids apart from some early primitive types known as the araeoscelidians. Modern reptiles and birds belong to the neodiapsid subclade Sauria.

<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>Petrolacosaurus</i> Genus of tetrapods

Petrolacosaurus is an extinct genus of diapsid reptile from the late Carboniferous period. It was a small, 40-centimetre (16 in) long reptile, and one of the earliest known reptile with two temporal fenestrae. This means that it was at the base of Diapsida, the largest and most successful radiation of reptiles that would eventually include all modern reptile groups, as well as dinosaurs and other famous extinct reptiles such as plesiosaurs, ichthyosaurs, and pterosaurs. However, Petrolacosaurus itself was part of Araeoscelida, a short-lived early branch of the diapsid family tree which went extinct in the mid-Permian.

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

Coelurosauravus is an extinct genus of gliding reptile, known from the Late Permian of Madagascar. Like other members of the family Weigeltisauridae, members of this genus possessed long, rod-like ossifications projecting outwards from the body. These bony rods were not extensions of the ribs but were instead a feature unique to weigeltisaurids. It is believed that during life, these structures formed folding wings used for gliding flight, similar to living gliding Draco lizards.

<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">Younginiformes</span> Extinct group of reptiles

Younginiformes is a group of diapsid reptiles known from the Permian-Triassic of Africa and Madagascar. It has been used as a replacement for "Eosuchia". Younginiformes were historically suggested to be lepidosauromorphs, but were later suggested to be basal non-saurian neodiapsids. The group is sometimes divided into two families, Tangasauridae and Younginidae. The monophyly of the group is disputed. A 2009 study found them to be an unresolved polytomy at the base of Neodiapsida, while a 2011 study recovered the group as paraphyletic. A 2022 study recovered the Younginiformes as a monophyletic group of basal neodiapsid reptiles, also including Claudiosaurus and Saurosternon as part of the group. Some younginiforms like Hovasaurus and Acerosodontosaurus are thought to have had an amphibious lifestyle, while others like Kenyasaurus, Thadeosaurus and Youngina were probably terrestrial.

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

Claudiosaurus is an extinct genus of diapsid reptiles from the Late Permian Sakamena Formation of the Morondava Basin, Madagascar. It has been suggested to be semi-aquatic.

<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>Eunotosaurus</i> Extinct genus of reptiles

Eunotosaurus is an extinct genus of amniote, possibly a close relative of turtles. Eunotosaurus lived in the late Middle Permian and fossils can be found in the Karoo Supergroup of South Africa. Eunotosaurus resided in the swamps of southern Africa. Its ribs were wide and flat, forming broad plates similar to a primitive turtle shell, and the vertebrae were nearly identical to those of some turtles. Accordingly, it is often considered as a possible transitional fossil between turtles and their prehistoric ancestors. However, it is possible that these turtle-like features evolved independently of the same features in turtles, since other anatomical studies and phylogenetic analyses suggest that Eunotosaurus may instead have been a parareptile, an early-diverging neodiapsid unrelated to turtles, or a synapsid.

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

Tangasauridae is an extinct family of diapsids known from fossil specimens from Madagascar, Kenya and Tanzania that are Late Permian to Early Triassic in age. Fossils have been found of numerous specimens of common members of this family such as Hovasaurus in different stages of ontogenic development. Recent material from the Middle Sakamena Formation of the Morondava Basin of Madagascar that dates back to the early Triassic period suggests that the Tangasauridae were relatively unaffected by the Permian-Triassic extinction event.

<i>Heleosaurus</i> Extinct genus of tetrapods

Heleosaurus scholtzi is an extinct species of basal synapsids, known as pelycosaurs, in the family of Varanopidae during the middle Permian. At first H. scholtzi was mistakenly classified as a diapsid. Members of this family were carnivorous and had dermal armor, and somewhat resembled monitor lizards. This family was the most geologically long lived, widespread, and diverse group of early amniotes. To date only two fossils have been found in the rocks of South Africa. One of these fossils is an aggregation of five individuals.

<i>Orovenator</i>

Orovenator is an extinct genus of diapsid from Lower Permian deposits of Oklahoma, United States. It is known from two partial skulls from the Richards Spur locality in Oklahoma. The holotype OMNH 74606 consists of a partial skull preserving snout and mandible, and the referred specimen, OMNH 74607, a partial skull preserving the skull roof, vertebrae and palatal elements. It was first named by Robert R. Reisz, Sean P. Modesto and Diane M. Scott in 2011 and the type species is Orovenator mayorum. The generic name means "mountain", oro, in Greek in reference to the Richards Spur locality, which was mountainous during the Permian period and "hunter", venator, in Latin. The specific name honours Bill and Julie May. Orovenator is the oldest and most basal neodiapsid to date.

Tangasaurus is an extinct genus of aquatic basal tangasaurid neodiapsid known from the Late Permian period of Tanga, northeastern Tanzania. It contains a single species, Tangasaurus mennelli.

Kenyasaurus is an extinct genus of basal tangasaurid known from the Early Triassic period of Coast Province, southeastern Kenya. It contains a single species, Kenyasaurus mariakaniensis.

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

Younginidae is an extinct family of diapsid reptiles from the Late Permian and Early Triassic. In a phylogenetic context, younginids are near the base of the clade Neodiapsida. Younginidae includes the species Youngina capensis from the Late Permian of South Africa and Thadeosaurus colcanapi from the Late Permian and Early Triassic of Madagascar. Heleosuchus griesbachi from the Late Permian of South Africa may also be a member of the family.

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

Pantestudines or Pan-Testudines is the group of all reptiles more closely related to turtles than to any other living animal. It includes both modern turtles and all of their extinct relatives. Pantestudines with a complete shell are placed in the clade Testudinata.

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 5 6 7 8 9 10 11 12 13 14 Currie, Philip J. (1980). "A new younginid (Reptilia: Eosuchia) from the Upper Permian of Madagascar" (PDF). Canadian Journal of Earth Sciences. 17 (4): 500–511. Bibcode:1980CaJES..17..500C. doi:10.1139/e80-046. Archived from the original (PDF) on 2023-04-21.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Bickelmann, Constanze; Müller, Johannes & Reisz, Robert R. (22 September 2009). "The enigmatic diapsid Acerosodontosaurus piveteaui (Reptilia: Neodiapsida) from the Upper Permian of Madagascar and the paraphyly of "younginiform" reptiles". Canadian Journal of Earth Sciences. 46 (9): 651–661. Bibcode:2009CaJES..46..651S. doi:10.1139/E09-038.
  3. 1 2 Bever, G. S.; Lyson, Tyler R.; Field, Daniel J. & Bhullar, Bhart-Anjan S. (2015). "Evolutionary origin of the turtle skull". Nature. 525 (7568): 239–242. Bibcode:2015Natur.525..239B. doi:10.1038/nature14900. PMID   26331544. S2CID   4401555.
  4. 1 2 Li, Chun; Fraser, Nicholas C.; Rieppel, Olivier & Wu, Xiao-Chun (22 August 2018). "A Triassic stem turtle with an edentulous beak". Nature. 560 (7719): 476–479. Bibcode:2018Natur.560..476L. doi:10.1038/s41586-018-0419-1. ISSN   1476-4687. PMID   30135526. S2CID   52067286.
  5. ↑ Nathan E. Van Vranken. "The Permian diapsid reptiles Acerosodontosaurus and Claudiosaurus are not stem-turtles: Morphological and fossil phylogenetic analyses must take a cautious, holistic approach toward turtle origins". 95th Annual Meeting Abstracts. doi: 10.55632/pwvas.v92i1.626 .
  6. ↑ Simões, Tiago R.; Kammerer, Christian F.; Caldwell, Michael W.; Pierce, Stephanie E. (2022-08-19). "Successive climate crises in the deep past drove the early evolution and radiation of reptiles". Science Advances. 8 (33): eabq1898. Bibcode:2022SciA....8.1898S. doi:10.1126/sciadv.abq1898. ISSN   2375-2548. PMC   9390993 . PMID   35984885.
  7. 1 2 Currie, P.J. (1981). "Hovasaurus boulei, an aquatic eosuchian from the Upper Permian of Madagascar" (PDF). Palaeontologia Africana. 24: 99–168. Archived (PDF) from the original on 2022-09-20.
  8. ↑ Evans, Susan E. (1988). "The early history and relationships of the Diapsida". In Benton, M. J. (ed.). The Phylogeny and Classification of the Tetrapods, Volume 1: Amphibians, Reptiles, Birds. Oxford: Clarendon Press. pp. 221–260.
  9. ↑ Reisz, Robert R.; Modesto, Sean P. & Scott, Diane M. (2011-12-22). "A new Early Permian reptile and its significance in early diapsid evolution". Proceedings of the Royal Society B: Biological Sciences. 278 (1725): 3731–3737. doi:10.1098/rspb.2011.0439. ISSN   0962-8452. PMC   3203498 . PMID   21525061.
  10. ↑ 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.
  11. ↑ Schoch, Rainer R. & Sues, Hans-Dieter (2018). "Osteology of the Middle Triassic stem-turtle Pappochelys rosinae and the early evolution of the turtle skeleton". Journal of Systematic Palaeontology. 16 (11): 927–965. Bibcode:2018JSPal..16..927S. doi:10.1080/14772019.2017.1354936. S2CID   90014658.
  12. ↑ Buffa, Valentin; Frey, Eberhard; Steyer, J.-Sébastien; Laurin, Michel (2021-07-12). "A new cranial reconstruction of Coelurosauravus elivensis Piveteau, 1926 (Diapsida, Weigeltisauridae) and its implications on the paleoecology of the first gliding vertebrates". Journal of Vertebrate Paleontology. 41 (2): e1930020. Bibcode:2021JVPal..41E0020B. doi:10.1080/02724634.2021.1930020. ISSN   0272-4634. S2CID   237517962.
  13. ↑ Smith, R. M. H. 2000. Sedimentology and taphonomy of Late Permian vertebrate fossil localities in Southwestern Madagascar. Paleontologia Africana 36:25–41
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