Fastnacht triassic pdf Http:app. Ble anterior to the first vertebra, and Fastnacht also reported a potential steinkern. Temporal range: Early Triassic, Olenekian. It was described in by Michael Fastnacht, who also reported that the specimen had an impression of the palate. Jump up Schoch, R.
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Description[ edit ] Dorsal left , ventral center , and posterior right views of the skull of Metoposaurus Many temnospondyls are much larger than living amphibians, and superficially resemble crocodiles. Others are smaller and resemble salamanders. The skulls are rounded or triangular in shape when viewed from above, and are usually covered in pits and ridges.
The rugged surfaces of bones may have supported blood vessels, which could transfer carbon dioxide to the bones to neutralize acidic build up in the blood early semiaquatic tetrapods would have had difficulty expelling carbon dioxide from their bodies while on land, and these dermal bones may have been an early solution to the problem.
The sulci, which usually run around the nostrils and eye sockets, are part of a lateral line system used to detect vibrations in water. Among the most distinguishing features of temnospondyls are the interpterygoid vacuities, two large holes in the back of the palate. Another pair of holes, choanae , are present in front of these vacuities, and connect the nasal passage with the mouth. Temnospondyls often have teeth on their palates, as well as in their jaws.
Some of these teeth are so large, they are referred to as tusks. In some temnospondyls, such as Nigerpeton , tusks in the lower jaw pierce the palate and emerge through openings in the top of the skull.
A block of sandstone, described in from the Early Carboniferous Mauch Chunk Formation of Pennsylvania , included impressions of the bodies of three temnospondyls. These impressions show, when alive, they had smooth skin, robust limbs with webbed feet, and a ridge of skin on their undersides. The trackways, called batrachichni , are usually found in strata deposited around freshwater environments, suggesting the animals had some ties to the water.
The undersides of most temnospondyls are covered in rows of large ventral plates. During early stages of development, they first have only small, rounded scales. Fossils show, as the animals grew, the scales on the undersides of their bodies developed into large, wide ventral plates.
The plates overlap each other in a way that allows a wide range of flexibility. Later semiaquatic temnospondyls, such as trematosaurs and capitosaurs , have no evidence of scales. They may have lost scales to make movement easier under water or to allow cutaneous respiration , the absorption of oxygen through the skin. One temnospondyl, Peltobatrachus , has armour-like plating that covers both its back and underside. Most members of the family Dissorophidae also have armor, although it only covers the midline of the back with two narrow rows of plates.
All of these temnospondyls were adapted to a terrestrial lifestyle. Armor may have offered protection from predators in the case of Peltobatrachus. Plagiosaurs may have inherited their armor from a terrestrial ancestor, as both Peltobatrachus and Laidleria have been considered close relatives of the group. In living tetrapods, the main body of the vertebra is a single piece of bone called the centrum , but in temnospondyls, this region was divided into a pleurocentrum and intercentrum.
Two types of vertebrae are recognized in temnospondyls: stereospondylous and rhachitomous vertebrae. The strong backbone and strong limbs of many ratchitomous temnospondyls allowed them to be partially, and in some cases fully, terrestrial. In stereospondylous vertebrae, the pleurocentra have been lost entirely, with the intercentra enlarged as the main body of the vertebrae.
This weaker type of backbone indicates that stereospondylous temnospondyls spent more time in water. However, temnospondyl remains have been known since the early part of the 19th century. The earliest described temnospondyl was Mastodonsaurus , named by Georg Friedrich Jaeger in from a single tooth that he considered to belong to a reptile.
Mastodonsaurus means "breast tooth lizard" after the nipple-like shape of the tip of the tooth. Leopold Fitzinger named the animal Batrachosaurus in In , the English palaeontologist Richard Owen referred to the genus as Labyrinthodon to describe its highly folded or labyrinthine teeth. Owen thought that the name Mastodonsaurus "ought not to be retained, because it recalls unavoidably the idea of the mammalian genus Mastodon, or else a mammilloid form of the tooth Although the two genera have similarly sized conical teeth, Phytosaurus was later found to be a crocodile-like reptile.
Additional material, including skulls, firmly placed Labyrinthodon as an amphibian. Jaeger also named Salamandroides giganteus in , basing it on partial occiput, or back portion of the skull.
In , he described a complete skull of S. Because Mastodonsaurus was named first, it has precedence over the other names as a senior subjective synonym. Mastodonsaurus and other similar animals were referred to as labyrinthodonts , named like Labyrinthodon for teeth that were highly folded in cross section.
Other specimens were found in the red sandstone of Warwickshire. As more fossils were uncovered in England, Owen depicted these labyrinthodonts as the "highest" form of batrachian and compared them to crocodiles, which he considered the highest form of reptiles.
He also noted the large labyrinthodonts of the Keuper a unit of rocks that dates to the Late Triassic were younger than more advanced reptiles in the Magnesian and Zechstein , which are Late Permian in age. Owen used these fossils to counter the notion that reptiles evolved from a sequential progression from early amphibians what he called "metamorphosed fishes". Cope placed stegocephalians in the class Batrachia, the name then used for Amphibia.
Stegocephalia means "roof-headed" in Greek , a reference to the wide, flat heads of temnospondyls and other early tetrapods. During this time, palaeontologists considered temnospondyls to be amphibians because they possessed three main features: gill arches in juvenile skeletons, indicating they were amphibious for at least the first part of their lives; ribs that do not connect at the underside of the rib cage; and deep pits in the skull that were interpreted as space for mucous glands.
Animals now regarded as temnospondyls were primarily labyrinthodonts, but some were classified in the Branchiosauria. Branchiosaurs were small-bodied and had simple conical teeth, while labyrinthodonts were larger and had complex, folded dentin and enamel in their teeth. Branchiosauria included only a few forms, such as Branchiosaurus from Europe and Amphibamus from North America, that had poorly developed bones, external gills, and no ribs.
Some skeletons of Amphibamus were later found with long ribs, prompting its reassignment to Microsauria although more detailed studies found it to be a temnospondyl. In the early 20th century, branchiosaurs would be recognized as larval forms of temnospondyls lacking many of the typical features that define the group, and is no longer recognized as a distinct group. Unlike labyrinthodonts, they did not have parietal foramina , small holes in their skulls behind their eye sockets.
Archegosaurus , Dendrerpeton , Eryops and Trimerorhachis were placed in this group and were considered to be the most primitive members of Reptilia. Their rhachitomous vertebrae, notochord , and lack of occipital condyles which attached the head to the neck were features that were also shared with fishes. Thus, they were considered a link between early fishes and more advanced forms such as stegocephalians. He classified Microsauria as a subgroup of Labyrinthodontia, placing many small, amphibian-like animals within it.
Among them was Dendrerpeton, once placed in Ganocephala. Dendrerpeton was later placed as a labyrinthodont with other temnospondyls, but confusion existed for many years over the classification of small amphibians. The American paleontologist Ermine Cowles Case called it Labyrinthodonta vera or "true labyrinthodonts". The labyrinthodontian suborders Microsauria and Branchiosauria, both of which contain temnospondyls, were distinct from Labyrinthodonta.
Within Labyrinthodonta were the groups Rhachitomi, Labyrinthodonti, and Embolerimi. Members of Rhachitomi, such as Archegosaurus and Eryops, had rhachitomous vertebrae with enlarged intercentra that displaced the pleurocentra. Labyrinthodonti, such as Mastodonsaurus, Trematosaurus, and Micropholis , had lost their pleurocentra, and the intercentra made up the entire body of the vertebrae.
Embolerimi had intercentra and pleurocentra that were of equal size. Embolomeres are now identified as reptiliomorphs distantly related to temnospondyls. In , von Zittel divided stegocephalians among three taxa: Lepospondyli, Temnospondyli, and Stereospondyli. He placed microsaurs in Lepospondyli, a group which he characterized as having simple, spool-shaped vertebral centra. Temnospondyli included forms with the centra divided into pleurocentra and intercentra. All members of Stereospondyli had amphicoelous centra composed only of the intercentra.
He continued to use Ganocephala and Labyrinthodonta which he alternatively referred to as Rhachitomi to distinguish animals based on the absence or presence of occipital condyles. In , British paleontologist D. Watson proposed that the evolutionary history of these large amphibians could be seen through changes in their vertebrae. Embolomerous forms in the Carboniferous graded into rhachitomous forms in the Permian, and finally into stereospondyls in the Triassic.
More importantly, Watson began using the term Labyrinthodontia to refer to these groups. His classification of labyrinthodonts was based heavily on characteristics of the skull rather than the vertebrae. Romer agreed with this classification, but used the name Temnospondyli to avoid confusion with Labyrinthodontia in its wider sense sensu lato.
Unlike modern temnospondyl classification, however, Romer included the primitive Ichthyostegalia in the group. Temnospondyls first appeared in the Early Carboniferous around million years ago Mya. During the Carboniferous, temnospondyls included basal medium-sized forms such as Dendrerpeton or large semiaquatic forms such as Cochleosaurus. Other, more derived temnospondyls, such as the amphibamids , were smaller and more terrestrial.
They resembled salamanders , and some taxa, such as the genus Branchiosaurus , even retained external gills like the modern-day axolotl. During the latest Carboniferous and Early Permian around Mya, several groups, such as the dissorophids and trematopids evolved strong, robust limbs and vertebrae and became adapted to life on land while others such as the eryopids , developed into large semiaquatic predators.
The dvinosaurs , a group of small aquatic temnospondyls, evolved from terrestrial ancestors in the Late Carboniferous. Other temnospondyls, such as archegosaurids , developed long snouts and a close similarity to crocodiles, although they lacked the armor characteristic of the latter group. These temnospondyls included the largest known batrachomorph, the 9-m-long Prionosuchus of Brazil. The vertebrae became weak,  the limbs small, and the skull large and flat, with the eyes facing upwards.
During the Triassic period, these animals dominated the freshwater ecosystems, evolving in a range of both small and large forms. During the Early Triassic Another group, the capitosauroids , included medium- and large-sized animals 2. These animals spent most or all their lives in water as aquatic predators, catching their prey by a sudden opening of the upper jaw and sucking in fish or other small animals.
Metoposaurids are distinguished from capitosauroids by the positioning of their eye sockets near the front of their skulls. Another group of stereospondyls, the plagiosaurs , had wide heads and gills , and adapted to life at the bottom of lakes and rivers.
By this time, temnospondyls had become a common and widespread component of semiaquatic ecosystems. Some temnospondyls, such as Cryobatrachus and Kryostega , even inhabited Antarctica , which was covered in temperate forests at the time.
Large assemblages of metoposaurs with hundreds of individuals preserved together have been found in the southwestern United States. They have often been interpreted as mass death events caused by droughts in floodplain environments. Recent studies show these dense assemblages were instead probably the result of currents accumulating dead individuals in certain areas.
Fastnacht Triassic PDF
Not wider than shaft 0or significantly While the other sutures are mostly straight, that with jugal is narrow having a serrated suture with the squamosal, the jugal is markedly serrated. Journal of Vertebrate Paleontology Cultriform process ventrally flat 0margin 0or extending anteriorly 1. The being only slightly longer than wide. The body of Sclerothorax is covered by small scale-like fastacht ossicles that would have been embedded in the dermis in life. The morphology of the early Amphibia and some mungslehre A similar opening was described in plate. Reconstruction of skull and mandible of Sclerothorax hypselonotus Huene, Life restoration of Prionosuchus plummeri. Studies on braincases of early tetrapods: Quadrate condyles posterior to parasphenoid 1.
FASTNACHT TRIASSIC PDF
Description[ edit ] Restoration Among the most unusual features of Sclerothorax are its elongated neural spines. The neural spines are tallest at the front of the spine. Sclerothorax also has a very large pectoral girdle ; the interclavicle bone is longer than the skull, meaning that Sclerothorax has the proportionally largest interclavicle of any temnospondyl. The body of Sclerothorax is covered by small scale-like bony ossicles that would have been embedded in the dermis in life. The skull of Sclerothorax is short, wide, and roughly rectangular in shape.
Nisar The cultriform process, marking the most anterior extension of pterygoid is separated from the exoccipital by a short lateral the interpterygoid vacuity. Stegocephalia of Senekal, O. Posteriorly, the ribs become successively longer with gated triangle. Comparative osteology of Mastodonsaurus giganteus nental marocain.