| Dasygnathoides Temporal range: Late Triassic | |
|---|---|
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| 18877 drawing of the cast from the holotype natural mold | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Archosauria |
| Clade: | Pseudosuchia |
| Genus: | † Dasygnathoides Kuhn, 1961 |
| Species: | †D. longidens |
| Binomial name | |
| †Dasygnathoides longidens (Huxley, 1877) | |
| Synonyms | |
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Dasygnathoides is an extinct genus of pseudosuchian from the Late Triassic (Carnian) Lossiemouth Sandstone of Scotland.
"Dasygnathus" longidens was erected by Thomas Huxley for a maxilla from the Lossiemouth Sandstone in 1877. The genus name Dasygnathus had already been used for a coleopteran insect, so Oskar Kuhn renamed it Dasygnathoides. [1] Although synonymized with Ornithosuchus by Walker (1964), a 2016 study found Dasygnathoides indeterminate beyond Pseudosuchia. [2] For this reason, many paleontologists consider 'Dasygnathoides' a nomem dubium.
The lack of synapomorphies shared by ornithosuchids indicates that Dasygnathoides was not an ornithosuchid as previously thought, but there are no links between it and any other family of pseudosuchians. It has remained impossible to resolve further. The morphology of the maxilla is quite different from aetosaurs, silesaurids, erpetosuchians, saurischians or ornithischians. The interdental plates also differ greatly from erythrosuchids and proterosuchids. Dasygnathoides cannot be assigned to any particular group of pseudosuchians at present. It is probably the first or only specimen of an entirely new group. [2]
Thomas Huxley first found the maxilla in the Lossiemouth Sandstone in 1859, and originally identified it as Stagonolepis, due to its very similar tooth implantation pattern. He later changed his mind and reidentified it as a new species, "Dasygnathus". This name later had to be changed in 1961 as it had already been used for a beetle. [2]
In 1964, the specimen of Dasygnathoides was compared with all the known Ornithosuchus specimens and then synonymized by Walker. This was due to the shared presence of 'rear forking' at the posterior end of the maxillae, only nine maxillary teeth, and the similarity between their right pterygoid bones. [2]
In 2016, M. Belén von Baczko and M. Ezcurra reassessed this synonymization and found that Dasygnathoides was in fact a much larger and quite different species to Ornithosuchus, and not even an ornithosuchid (see above). [2]
Dasygnathoides is known from a right maxilla and pterygoid, a partial vertebra, a haemal arch and a phalanx, an articular and an osteoderm. They all come from the same animal. There was also a small radius and ulna found in the slab, but this was far too small to have been from the same specimen and can probably be discounted as stomach contents.
The total skull length is estimated to have been about 450 mm, almost twice as long as the largest Ornithosuchus skull found, and the entire animal was probably between 3 and 4 metres long. It is the largest predatory tetrapod known from Triassic Scotland. [2]
The maxilla found has four teeth remaining in it and nine interdental plates, showing that five teeth are missing. The total length of the maxilla is 195 mm and the teeth range from 29.5 mm to 53.5 mm long. The teeth are posteriorly curved and have sharp edges, indicating that they might have been used as blades to slice flesh rather than merely to impale and grip. The interdental plates are pentagonal, would have formed the medial walls of the tooth sockets, and in life were richly supplied with blood vessels, giving them a rather wrinkled look. [2]
No ascending or palatal process can be found on the specimen, and nor can the 'rear forking prong' mentioned above. Indeed, the prong mentioned can only be found on a single specimen of Ornithosuchus. [2]
This specimen shows the dorsal surface of the right pterygoid bone, and a small part of either a palatine or vomer bone. It is 164 mm long. The anterior ramus is narrow and tapering, but the medial margin is thick and the quadrate ramus is almost as wide as it is long. Th quadrate ramus is dorsally curved and bears a groove extending anterolaterally.
Unlike Ornithosuchus, Dasygnathoides did not appear to have a palatine-pterygoid fenestra as the homologous area of bone is curved outwards. This indicates that, in fact, it is not an ornithosuchan at all. [2]
The partial vertebra is found in the same piece of stone as the maxilla. It has a well-developed transverse process and is probably a dorsal or anterior caudal vertebra. [2]
These are small and fragmentary, and little information can be gained from them. It is possible that they are, in fact, stomach or throat contents of the actual Dasygnathoides fossil. [2]
This was previously identified as a possible nasal bone, but is far more likely to be an osteoderm indicating that Dasygnathoides had skin armour. It resembles the elongated osteoderms of Ornithosuchus. [2]
Ornithosuchus is an extinct genus of pseudosuchians from the Late Triassic (Carnian) Lossiemouth Sandstone of Scotland. It was originally thought to be the ancestor to the carnosaurian dinosaurs, but it is now known to be more closely related to crocodilians than to dinosaurs.
Venaticosuchus is a genus of pseudosuchian archosaurs from the family Ornithosuchidae. Known from a single species, Venaticosuchus rusconii, this genus is described based on an incomplete skull and jaw collected from the Late Triassic (Carnian) Ischigualasto Formation in the Ischigualasto-Villa Unión Basin in northwestern Argentina, which was deposited around 230 million years ago. This fossil material has been termed the holotype specimen PVL 2578. Venaticosuchus incorporated a myriad of features present in the other two genera of ornithosuchids, Ornithosuchus and Riojasuchus. However, it also had several unique traits, relating to the lower jaw.
Gracilisuchus is an extinct genus of tiny pseudosuchian from the Late Triassic of Argentina. It contains a single species, G. stipanicicorum, which is placed in the clade Suchia, close to the ancestry of crocodylomorphs. Both the genus and the species were first described by Alfred Romer in 1972.
Hyperodapedon is a genus of rhynchosaurs from the Late Triassic period. Fossils of the genus have been found in Africa, Asia, Europe and North and South America. Its first discovery and naming was found by Thomas Henry Huxley in 1859. Hyperodapedon was a herbivore that used its beaked premaxilla and hindlimbs to dig for plants in dry land.
Riojasuchus is an extinct genus of ornithosuchid archosaur from the Late Triassic (Norian) of Argentina. Ornithosuchidae was a widespread family of facultatively bipedal pseudosuchians with adaptations for scavenging. Riojasuchus is notable as one of the youngest and most complete members of the family. The type and only known species, Riojasuchus tenuisceps, was named and described by José Bonaparte in 1967. It was one of the first of many well-preserved Triassic archosaurs to be discovered in Argentina. The holotype specimen, PVL 3827, was found in the Los Colorados Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina.
Calyptosuchus is an extinct genus of aetosaur from the Late Triassic of North America. Like other aetosaurs, it was heavily armored and had a pig-like snout used to uproot plants.
Ornithosuchidae is an extinct family of pseudosuchian archosaurs from the Triassic period. Ornithosuchids were quadrupedal and facultatively bipedal, meaning that they had the ability to walk on two legs for short periods of time. They had distinctive, downturned snouts, unique, "crocodile-reversed" ankle bones, and several other features that distinguish them from other archosaurs. Ornithosuchids were geographically widespread during the Carnian and Norian stages of the Late Triassic with members known from Argentina, Brazil, and the United Kingdom. Four genera, comprising Ornithosuchus, Venaticosuchus, Dynamosuchus, and Riojasuchus are presently known. The family was first erected by German paleontologist Friedrich von Huene in 1908.
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.
Anatosuchus is an extinct genus of notosuchian crocodylomorph discovered in Gadoufaoua, Niger, and described by a team of palaeontologists led by the American Paul Sereno in 2003, in the Journal of Vertebrate Paleontology. Its duck-like snout coincidentally makes it resemble a crocoduck, an imagined hybrid animal with the head of a crocodile and the body of a duck.
Yarasuchus is an extinct genus of avemetatarsalian archosaur that lived during the Anisian stage of the Middle Triassic of India. The genus was named and described in 2005 from a collection of disarticulated but fairly complete fossil material found from the Middle Triassic Yerrapalli Formation. The material is thought to be from two individuals, possibly three, with one being much more complete and articulated than the other. The type and only species is Y. deccanensis. Yarasuchus was a quadruped roughly 2–2.5 metres (6.6–8.2 ft) long, with an elongated neck and tall spines on its vertebrae. Unlike other quadrupedal Triassic reptiles, the limbs and shoulders of Yarasuchus were slender, and more like those of ornithodirans.
Biseridens is an extinct genus of anomodont therapsid, and one of the most basal anomodont genera known. Originally known from a partial skull misidentified as an eotitanosuchian in 1997, another well-preserved skull was found in the Qingtoushan Formation in the Qilian Mountains of Gansu, China, in 2009 that clarified its relationships to anomodonts, such as the dicynodonts.
Polonosuchus is a genus of rauisuchid known from the late Triassic of Poland. It was a huge predator about 5–6 metres in length and, like all rauisuchians, was equipped with a large head of long sharp teeth. The legs were placed almost underneath the body, unlike most reptiles, which would have made it quite fast and a powerful runner. The appearance was very similar to that of the more known Postosuchus, of North America, and shared with the latter the ecological niche of the apex predator.
Archeopelta is an extinct genus of carnivorous archosaur from the late Middle or early Late Triassic period. It was a 2 m (6 ft) long predator which lived in what is now southern Brazil. Its exact phylogenetic placement within Archosauriformes is uncertain; it was originally classified as a doswelliid, but subsequently it was argued to be an erpetosuchid archosaur.
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Aenigmaspina is an extinct genus of enigmatic pseudosuchian (=crurotarsan) archosaur from the Late Triassic of the United Kingdom. Its fossils are known from the Pant-y-ffynnon Quarry in South Wales, of which its type and only known species is named after, A. pantyffynnonensis. Aenigmaspina is characterised by the unusual spines on its vertebrae, which are broad and flat on top with a unique 'Y' shape. Although parts of its skeleton is relatively well known, the affinities of Aenigmaspina to other pseudosuchians are unclear, although it is possibly related to families Ornithosuchidae, Erpetosuchidae or Gracilisuchidae.
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