Misplaced Pages

#753246

146-474: The Yerrapalli Formation is a Triassic rock formation consisting primarily of mudstones that outcrops in the Pranhita–Godavari Basin in southeastern India. The Yerrapalli Formation preserves fossils of freshwater and terrestrial vertebrates as well as trace fossils of invertebrates. The tetrapod fauna includes temnospondyl amphibians, archosauromorph reptiles, and dicynodonts . Most of

292-630: A bolide impact, for which an impact crater containing Manicouagan Reservoir in Quebec , Canada , has been singled out. However, the Manicouagan impact melt has been dated to 214±1 Mya. The date of the Triassic-Jurassic boundary has also been more accurately fixed recently, at 201.4 Mya. Both dates are gaining accuracy by using more accurate forms of radiometric dating, in particular the decay of uranium to lead in zircons formed at time of

438-626: A cosmopolitan distribution . Coelacanths show their highest post- Devonian diversity in the Early Triassic . Ray-finned fishes (actinopterygians) went through a remarkable diversification in the beginning of the Triassic, leading to peak diversity during the Middle Triassic; however, the pattern of this diversification is still not well understood due to a taphonomic megabias . The first stem-group teleosts appeared during

584-588: A bone common in stem tetrapods, is only found in some late Paleozoic taxa like certain edopoids and dvinosaurs . Most temnospondyls have an indentation at the back of the skull called otic notches. It has typically been inferred that this structure supported a typanum for hearing, although there is substantial variation among temnospondyls in the anatomy of this notch such that it may not have served this function in all temnospondyls, and some clades like plagiosaurids and brachyopids lack notches entirely. The palate of temnospondyls generally consists of

730-555: A chain of mountain ranges stretching from Turkey to Malaysia . Pangaea was fractured by widespread faulting and rift basins during the Triassic—especially late in that period—but had not yet separated. The first nonmarine sediments in the rift that marks the initial break-up of Pangaea, which separated eastern North America from Morocco , are of Late Triassic age; in the United States , these thick sediments comprise

876-516: A close similarity to crocodiles, although they lacked the armor characteristic of the latter group. These temnospondyls included the largest-known batrachomorph, the over 5.5-meter-long Prionosuchus of Brazil. The stereospondyl record is almost exclusively confined to rhinesuchids . As temnospondyls continued to flourish and diversify in the Late Permian (260.4–251.0 Mya), a major group called Stereospondyli became more dependent on life in

1022-404: A counterpart to it), but Stereospondyli is still considered valid. Below is a simplified taxonomy of temnospondyls showing currently recognized groups: Class Amphibia In one of the earliest phylogenetic analyses of the group, Gardiner (1983) recognized five characteristics that made Temnospondyli a clade : a bone at the back of the skull, the parasphenoid , is connected to another bone on

1168-474: A few exposures in the west. During the Triassic peneplains are thought to have formed in what is now Norway and southern Sweden. Remnants of this peneplain can be traced as a tilted summit accordance in the Swedish West Coast . In northern Norway Triassic peneplains may have been buried in sediments to be then re-exposed as coastal plains called strandflats . Dating of illite clay from

1314-501: A group called Ganocephala, which was characterized by plate-like skull bones, small limbs, fish-like scales and branchial arches. 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

1460-399: 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. Cope objected to von Zittel's classification, considering the vertebrae of lepospondyls and stereospondyls indistinguishable because each had

1606-471: A long beak-like snout), and Shringasaurus (a horned herbivore which reached a body length of 3–4 metres (9.8–13.1 ft)). One group of archosauromorphs, the archosauriforms , were distinguished by their active predatory lifestyle, with serrated teeth and upright limb postures. Archosauriforms were diverse in the Triassic, including various terrestrial and semiaquatic predators of all shapes and sizes. The large-headed and robust erythrosuchids were among

SECTION 10

#1732797860754

1752-473: A particularly high diversity of dissorophoids. Middle Permian records of temnospondyls are relatively sparse, and some of these are debated as a result of the uncertain age and correlation of different deposits in North America (Chickasha, Flowerpot Formations), Niger (Moradi Formation), Brazil (Rio do Rasto Formation), and Russia (Mezen complex) and the subsequent controversy over Olson's Gap, but there

1898-617: A pseudosuchian. Pseudosuchians were far more ecologically dominant in the Triassic, including large herbivores (such as aetosaurs ), large carnivores (" rauisuchians "), and the first crocodylomorphs (" sphenosuchians "). Aetosaurs were heavily-armored reptiles that were common during the last 30 million years of the Late Triassic until they died out at the Triassic-Jurassic extinction. Most aetosaurs were herbivorous and fed on low-growing plants, but some may have eaten meat. " rauisuchians " (formally known as paracrocodylomorphs ) were

2044-509: A reference to the wide, flat heads of temnospondyls and other early tetrapods. During this time, paleontologists 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 . Several suborders of stegocephalians were recognized in

2190-458: A short period of time, becoming extinct about 220 million years ago. They were exceptionally abundant in the middle of the Triassic, as the primary large herbivores in many Carnian-age ecosystems. They sheared plants with premaxillary beaks and plates along the upper jaw with multiple rows of teeth. Allokotosaurs were iguana-like reptiles, including Trilophosaurus (a common Late Triassic reptile with three-crowned teeth), Teraterpeton (which had

2336-474: A simple spool shape. 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. Temnospondyli became a commonly used name at the turn of the 20th century. Paleontologists included both embolomeres and rhachitomes in the group. Cope's Ganocephala and Labyrinthodonta fell out of use. In 1919, British paleontologist D. M. S. Watson proposed that

2482-491: 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. The naming of these first specimens was disputed. Leopold Fitzinger named the animal Batrachosaurus in 1837. In 1841, the English paleontologist Richard Owen referred to the genus as Labyrinthodon to describe its highly folded or labyrinthine teeth. Owen thought that

2628-449: A strandflat of Bømlo , southern Norway, have shown that landscape there became weathered in Late Triassic times ( c. 210 million years ago) with the landscape likely also being shaped during that time. Eustatic sea level in the Triassic was consistently low compared to the other geological periods. The beginning of the Triassic was around present sea level, rising to about 10–20 metres (33–66 ft) above present-day sea level during

2774-567: A sudden opening of the upper jaw and sucking in fish or other small animals. In the Carnian stage of the Late Triassic (237.0–227.0 Mya), capitosauroids were joined by the superficially very similar Metoposauridae . 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

2920-585: A supercontinent has less shoreline compared to a series of smaller continents, Triassic marine deposits are relatively uncommon on a global scale. A major exception is in Western Europe , where the Triassic was first studied. The northeastern margin of Gondwana was a stable passive margin along the Neo-Tethys Ocean, and marine sediments have been preserved in parts of northern India and Arabia . In North America , marine deposits are limited to

3066-419: A temnospondyl). Soft tissue, such as scales and external gills, were found in many well-preserved branchiosaur fossils from Germany. 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. Other animals that would later be classified as temnospondyls were placed in

SECTION 20

#1732797860754

3212-426: A variety of environmental conditions. Contrary to older assumptions, more recent studies have argued that the temnospondyls evolved from a terrestrial ancestor (although with aquatic eggs and larvae), and that it was the forms that later returned to water and an aquatic lifestyle which evolved a spine more rigid and stiffer than the terrestrial species. Very little is known of the soft tissue of temnospondyls because

3358-504: Is a reptiliomorph , the name Temnospondyli is synonymous with Batrachomorpha (a clade containing all organisms that are more closely related to modern amphibians than to mammals and reptiles). Rainer Schoch in 2013 defined the name Temnospondyli as applying to “[t]he least inclusive clade containing Edops craigi and Mastodonsaurus giganteus ”. Many temnospondyls are much larger than living amphibians, and superficially resemble crocodiles , which has led many taxa to be named with

3504-556: Is a general consensus that at least some of these records are Guadalupian in age. Records of rhinesuchids from the Eodicynodon and Tapinocephalus Assemblage Zones of South Africa are less controversial. Additional records are known from Brazil, China, Turkey, and the Isheevo complex of Russia. A mixture of taxa are represented, including stereospondylomorphs ( Konzhukovia ) and rhinesuchid stereospondyls, as well as some of

3650-468: Is a recent study of North American faunas. In the Petrified Forest of northeast Arizona there is a unique sequence of late Carnian-early Norian terrestrial sediments. An analysis in 2002 found no significant change in the paleoenvironment. Phytosaurs , the most common fossils there, experienced a change-over only at the genus level, and the number of species remained the same. Some aetosaurs ,

3796-636: Is divided into several parts (intercentrum, paired pleurocentra, neural arch), although this occurs widely among other early tetrapods. Experts disagree over whether temnospondyls were ancestral to modern amphibians ( frogs , salamanders and caecilians ), or whether the whole group died out without leaving any descendants. Different hypotheses have placed modern amphibians as the descendants of temnospondyls, as descendants of another group of early tetrapods called lepospondyls , or even as descendants of both groups (with caecilians evolving from lepospondyls and frogs and salamanders evolving from temnospondyls). There

3942-401: Is further disagreement about a temnospondyl origin of lissamphibians related to whether the modern groups arose from only one group ( dissorophoids ) or from two different groups (dissorophoids and stereospondyls ). The majority of studies place a group of temnospondyls called amphibamiforms as the closest relatives of modern amphibians. Similarities in teeth, skulls and hearing structures link

4088-599: Is highly variable, and complete caudal sequences are rare. Based on Eryops , more than 30 caudal positions were possible in some taxa. The pectoral girdle comprised an unpaired interclavicle, paired clavicles, paired cleithra, and paired scapulae / scapulocoracoids as with most other early tetrapods. These elements differ widely in variation across temnospondyls, with such variation attributed to different lifestyles. The interclavicle and clavicles tend to be more lightly built in terrestrial taxa, with little to no ornamentation. In contrast, these elements are massively ossified in

4234-508: Is likely a paraphyletic group rather than a true clade. Tanystropheids were a family of protorosaurs which elevated their neck size to extremes, with the largest genus Tanystropheus having a neck longer than its body. The protorosaur family Sharovipterygidae used their elongated hindlimbs for gliding. Other archosauromorphs, such as rhynchosaurs and allokotosaurs , were mostly stocky-bodied herbivores with specialized jaw structures. Rhynchosaurs, barrel-gutted herbivores, thrived for only

4380-501: Is no evidence for a buccal pump mechanism for respiration. Temnospondyls often have extensive coverings of teeth on their palates, as well as in their jaws, in contrast to modern amphibians. Some of these teeth are so large that they are referred to as tusks or fangs. Although most temnospondyls have monocuspid teeth, the presence of bicuspid and/or pedicellate teeth in some dissorophoids has been cited as evidence for close relatedness to lissamphibians. In some temnospondyls, such as

4526-469: Is no evidence of glaciation at or near either pole; in fact, the polar regions were apparently moist and temperate , providing a climate suitable for forests and vertebrates, including reptiles. Pangaea's large size limited the moderating effect of the global ocean; its continental climate was highly seasonal, with very hot summers and cold winters. The strong contrast between the Pangea supercontinent and

Yerrapalli Formation - Misplaced Pages Continue

4672-468: Is not unique to one group of temnospondyls. Moreover, the distinction between rhachitomous and stereospondylous vertebrae is not entirely clear. Some temnospondyls have rhachitomous , semirhachitomous and sterospondylous vertebrae at different points in the same vertebral column. Other taxa have intermediate morphologies that do not fit into any category. Rachitomi is no longer recognized as an exclusive group (i.e. it includes Stereospondyli rather than being

4818-538: Is now placed as an early tetrapod outside Temnospondyli, and Rhombopholis is now considered a prolacertiform reptile. Later in the 19th century, temnospondyls were classified as various members of Stegocephalia , a name coined by the American paleontologist Edward Drinker Cope in 1868. Cope placed stegocephalians in the class Batrachia, the name then used for Amphibia . Stegocephalia means "roof-headed" in Greek ,

4964-460: Is superimposed by 22 sea level drop events widespread in the geologic record, mostly of minor (less than 25-metre (82 ft)) and medium (25–75-metre (82–246 ft)) magnitudes. A lack of evidence for Triassic continental ice sheets suggest that glacial eustasy is unlikely to be the cause of these changes. The Triassic continental interior climate was generally hot and dry, so that typical deposits are red bed sandstones and evaporites . There

5110-538: Is thought to have stiffened the vertebral column in association with the relative terrestriality of this clade. Recent histological work has demonstrated that most of this hyperelongation is formed by the osteoderm capping the spine, and thus the sail of Platyhystrix is dissimilar to that of pelycosaurs in which it is entirely formed by the spine. The majority of temnospondyls have presacral counts between 23 and 27, with reduction observed in some amphibamiforms and elongation observed in many dvinosaurs. Caudal length

5256-462: Is usually covered in pits and ridges to form a honeycomb-like pattern. One of the most recent hypotheses for the function of the dermal ornamentation is that it 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

5402-524: The Carnian (early part of the Late Triassic), some advanced cynodonts gave rise to the first mammals . During the Triassic, archosaurs displaced therapsids as the largest and most ecologically prolific terrestrial amniotes. This "Triassic Takeover" may have contributed to the evolution of mammals by forcing the surviving therapsids and their mammaliaform successors to live as small, mainly nocturnal insectivores . Nocturnal life may have forced

5548-599: The Jurassic and Early Cretaceous periods, but all had gone extinct by the Late Cretaceous . During about 210 million years of evolutionary history, they adapted to a wide range of habitats, including freshwater, terrestrial, and even coastal marine environments. Their life history is well understood, with fossils known from the larval stage, metamorphosis and maturity. Most temnospondyls were semiaquatic , although some were almost fully terrestrial, returning to

5694-559: The Jurassic , when the temnospondyls had become very rare. Most of the Reptiliomorpha , stem-amniotes that gave rise to the amniotes, disappeared in the Triassic, but two water-dwelling groups survived: Embolomeri that only survived into the early part of the period, and the Chroniosuchia , which survived until the end of the Triassic. The Permian–Triassic extinction devastated terrestrial life. Biodiversity rebounded as

5840-618: The Kamthi Formation , underlies the Bhimaram Formation , and is conformable with both formations. Two members of the Yerrapalli Formation have been recognized; a lower member consisting of layers of red and purple clay with lenses of pale green clay and an upper member consisting of alternating layers of clay and fine-grained sandstone. The paleobiota of the Yerrapalli Formation is similar to that of

5986-568: The Lake Lugano region of northern Italy and southern Switzerland , was in Middle Triassic times a lagoon behind reefs with an anoxic bottom layer, so there were no scavengers and little turbulence to disturb fossilization, a situation that can be compared to the better-known Jurassic Solnhofen Limestone lagerstätte . The remains of fish and various marine reptiles (including the common pachypleurosaur Neusticosaurus , and

Yerrapalli Formation - Misplaced Pages Continue

6132-658: The Newark Supergroup . Rift basins are also common in South America, Europe, and Africa. Terrestrial environments are particularly well-represented in the South Africa, Russia, central Europe, and the southwest United States. Terrestrial Triassic biostratigraphy is mostly based on terrestrial and freshwater tetrapods, as well as conchostracans ("clam shrimps"), a type of fast-breeding crustacean which lived in lakes and hypersaline environments. Because

6278-474: The Olenekian and Anisian of Gondwana . Both kannemeyeriiform dicynodonts and gomphodont cynodonts remained important herbivores during much of the period. Therocephalians included both large predators ( Moschorhinus ) and herbivorous forms ( bauriids ) until their extinction midway through the period. Ecteniniid cynodonts played a role as large-sized, cursorial predators in the Late Triassic. During

6424-735: The surviving species repopulated empty terrain, but these were short-lived. Diverse communities with complex food-web structures took 30 million years to reestablish. Archosauromorph reptiles, which had already appeared and diversified to an extent in the Permian Period, exploded in diversity as an adaptive radiation in response to the Permian-Triassic mass extinction. By the Early Triassic, several major archosauromorph groups had appeared. Long-necked, lizard-like early archosauromorphs were known as protorosaurs , which

6570-463: The temnospondyls , giant aquatic predators that had survived the end-Permian extinction and saw a new burst of diversification in the Triassic, before going extinct by the end; however, early crown-group lissamphibians (including stem-group frogs , salamanders and caecilians ) also became more common during the Triassic and survived the extinction event. The earliest known neopterygian fish, including early holosteans and teleosts , appeared near

6716-524: The thecodonts ) disappeared, as did most of the large labyrinthodont amphibians, groups of small reptiles, and most synapsids. Some of the early, primitive dinosaurs also became extinct, but more adaptive ones survived to evolve into the Jurassic. Surviving plants that went on to dominate the Mesozoic world included modern conifers and cycadeoids. The cause of the Late Triassic extinction is uncertain. It

6862-437: The traversodont cynodonts—were much reduced in the northern half of Pangaea ( Laurasia ). These extinctions within the Triassic and at its end allowed the dinosaurs to expand into many niches that had become unoccupied. Dinosaurs became increasingly dominant, abundant and diverse, and remained that way for the next 150 million years. The true "Age of Dinosaurs" is during the following Jurassic and Cretaceous periods, rather than

7008-487: The 20th and 21st centuries, including the first occurrences from historically undersampled regions such as Antarctica, Lesotho, Japan, Namibia, New Zealand, Niger, and Türkiye. Temnospondyls first appeared in the Middle Mississippean ( Viséan ) around 330 million years ago (Mya) where the earliest appearances are Balanerpeton from Scotland and an indeterminate temnospondyl from Germany. During

7154-832: The Anisian to Ladinian of the Tethysian domain, and from the Carnian and Rhaetian of a larger area that includes also the Boreal domain (e.g., Svalbard Islands), the North American continent, the South China block and Argentina . The best-studied of such episodes of humid climate, and probably the most intense and widespread, was the Carnian Pluvial Event . The Early Triassic was the hottest portion of

7300-472: The Carboniferous, all of the non-stereospondylomorph clades appeared, including dendrerpetids , edopoids , eryopoids , the various dissorophoid subclades, dvinosaurs and zatracheids. Stereospondylomorphs and stereospondyls first appeared in the early Permian, although the former may have appeared earlier and merely be undocumented at present. The vast majority of the Carboniferous records come from

7446-405: The Carnian and include early sauropodomorphs and theropods. Most Triassic dinosaurs were small predators and only a few were common, such as Coelophysis , which was 1 to 2 metres (3.3 to 6.6 ft) long. Triassic sauropodomorphs primarily inhabited cooler regions of the world. The large predator Smok was most likely also an archosaur, but it is uncertain if it was a primitive dinosaur or

SECTION 50

#1732797860754

7592-563: The Early Triassic, forming small patches of reefs of modest extent compared to the great reef systems of Devonian or modern times. At the end of the Carnian, a reef crisis occurred in South China. Serpulids appeared in the Middle Triassic. Microconchids were abundant. The shelled cephalopods called ammonites recovered, diversifying from a single line that survived the Permian extinction. Bivalves began to rapidly diversify during

7738-402: The Early Triassic, while others (e.g. capitosaurs ) remained successful throughout the whole period, or only came to prominence in the Late Triassic (e.g. Plagiosaurus , metoposaurs ). The first Lissamphibians (modern amphibians) appear in the Triassic, with the progenitors of the first frogs already present by the Early Triassic. However, the group as a whole did not become common until

7884-562: The Early and Middle Triassic. Sea level rise accelerated in the Ladinian, culminating with a sea level up to 50 metres (164 ft) above present-day levels during the Carnian. Sea level began to decline in the Norian, reaching a low of 50 metres (164 ft) below present sea level during the mid-Rhaetian. Low global sea levels persisted into the earliest Jurassic. The long-term sea level trend

8030-619: The Earth's biosphere impoverished; it was well into the middle of the Triassic before life recovered its former diversity. Three categories of organisms can be distinguished in the Triassic record: survivors from the extinction event, new groups that flourished briefly, and other new groups that went on to dominate the Mesozoic Era. Reptiles , especially archosaurs , were the chief terrestrial vertebrates during this time. A specialized group of archosaurs, called dinosaurs , first appeared in

8176-613: The Jurassic. There were many types of marine reptiles. These included the Sauropterygia , which featured pachypleurosaurus and nothosaurs (both common during the Middle Triassic, especially in the Tethys region), placodonts , the earliest known herbivorous marine reptile Atopodentatus , and the first plesiosaurs . The first of the lizardlike Thalattosauria ( askeptosaurs ) and the highly successful ichthyopterygians , which appeared in Early Triassic seas, soon diversified. By

8322-432: The Late Triassic but did not become dominant until the succeeding Jurassic Period. Archosaurs that became dominant in this period were primarily pseudosuchians , relatives and ancestors of modern crocodilians , while some archosaurs specialized in flight, the first time among vertebrates, becoming the pterosaurs . Therapsids , the dominant vertebrates of the preceding Permian period, saw a brief surge in diversification in

8468-600: The Latest Olenekian Cooling (LOC), from 248 to 247 Ma, temperatures cooled by about 6 °C. The Middle Triassic was cooler than the Early Triassic, with temperatures falling over most of the Anisian, with the exception of a warming spike in the latter portion of the stage. From 242 to 233 Ma, the Ladinian-Carnian Cooling (LCC) ensued. At the beginning of the Carnian, global temperatures continued to be relatively cool. The eruption of

8614-653: The Maleri Formation. The dicynodonts of the Yerrapalli Formation are similar to those of the Ntawere Formation in Zambia, which also dates back to the Anisian. During the Middle Triassic, what is now India and southern Africa formed one continuous landmass as part of the supercontinent Gondwana . Triassic The Triassic began in the wake of the Permian–Triassic extinction event , which left

8760-486: The Middle Triassic, becoming highly abundant in the oceans. Aquatic insects rapidly diversified during the Middle Triassic, with this time interval representing a crucial diversification for Holometabola , the clade containing the majority of modern insect species. In the wake of the Permian-Triassic mass extinction event , the fish fauna was remarkably uniform, with many families and genera exhibiting

8906-618: The Middle Triassic, some ichthyopterygians were achieving very large body masses. Among other reptiles, the earliest turtles , like Proganochelys and Proterochersis , appeared during the Norian Age (Stage) of the Late Triassic Period. The Lepidosauromorpha , specifically the Sphenodontia , are first found in the fossil record of the earlier Carnian Age, though the earliest lepidosauromorphs likely occurred in

SECTION 60

#1732797860754

9052-450: The Permian extinction, Archaeplastida (red and green algae) had been the major marine phytoplanktons since about 659–645 million years ago, when they replaced marine planktonic cyanobacteria , which first appeared about 800 million years ago, as the dominant phytoplankton in the oceans. In the Triassic, secondary endosymbiotic algae became the most important plankton. In marine environments , new modern types of corals appeared in

9198-475: The Permian. The Procolophonidae , the last surviving parareptiles , were an important group of small lizard-like herbivores. The drepanosaurs were a clade of unusual, chameleon-like arboreal reptiles with birdlike heads and specialised claws. Three therapsid groups survived into the Triassic: dicynodonts , therocephalians , and cynodonts . The cynodont Cynognathus was a characteristic top predator in

9344-408: The Triassic (teleosts are by far the most diverse group of fish today). Predatory actinopterygians such as saurichthyids and birgeriids , some of which grew over 1.2 m (3.9 ft) in length, appeared in the Early Triassic and became widespread and successful during the period as a whole. Lakes and rivers were populated by lungfish (Dipnoi), such as Ceratodus , which are mainly known from

9490-476: The Triassic was mostly hot and dry, with deserts spanning much of Pangaea's interior. However, the climate shifted and became more humid as Pangaea began to drift apart. The end of the period was marked by yet another major mass extinction, the Triassic–Jurassic extinction event , that wiped out many groups, including most pseudosuchians, and allowed dinosaurs to assume dominance in the Jurassic. The Triassic

9636-609: The Triassic, enlarging the Neo-Tethys Ocean which formed in their wake. At the same time, they forced the Paleo-Tethys Ocean to shrink as it was being subducted under Asia. By the end of the Triassic, the Paleo-Tethys Ocean occupied a small area and the Cimmerian terranes began to collide with southern Asia. This collision, known as the Cimmerian Orogeny , continued into the Jurassic and Cretaceous to produce

9782-428: The Triassic, with dicynodonts and cynodonts quickly becoming dominant, but they declined throughout the period with the majority becoming extinct by the end. However, the first stem-group mammals ( mammaliamorphs ), themselves a specialized subgroup of cynodonts, appeared during the Triassic and would survive the extinction event, allowing them to radiate during the Jurassic. Amphibians were primarily represented by

9928-496: The Triassic. Temnospondyli See below Temnospondyli (from Greek τέμνειν, temnein 'to cut' and σπόνδυλος, spondylos 'vertebra') or temnospondyls is a diverse ancient order of small to giant tetrapods —often considered primitive amphibians —that flourished worldwide during the Carboniferous , Permian and Triassic periods, with fossils being found on every continent. A few species continued into

10074-486: The Triassic. Common ichnogenera include Batrachichnus and Limnopus . Temnospondyli was named by the German paleontologist Karl Alfred von Zittel in his second edition of Handbuch der Palaeontologie , published in 1888. 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 1828 from

10220-839: The Wrangellia Large Igneous Province around 234 Ma caused abrupt global warming, terminating the cooling trend of the LCC. This warming was responsible for the Carnian Pluvial Event and resulted in an episode of widespread global humidity. The CPE ushered in the Mid-Carnian Warm Interval (MCWI), which lasted from 234 to 227 Ma. At the Carnian-Norian boundary occurred a positive δ C excursion believed to signify an increase in organic carbon burial. From 227 to 217 Ma, there

10366-522: The Yerrapalli Formation consists of red mudstones. The mudstones were deposited across a floodplain during the Anisian stage of the Middle Triassic . Smaller lenses of calcareous sandstone represent ephemeral streams that branched off from the larger channels that were the source of the floodplain sediments. The climate of the region during the time is thought to have been monsoonal with both wet and dry seasons. The Yerrapalli Formation overlies

10512-420: 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

10658-489: The aquatic stereospondyls and are well ornamented in the same fashion as the skull. The cleithrum and scapulocoracoid is more developed in terrestrial taxa, and the coracoid tends not to ossify in aquatic forms such that there is only a much shorter scapula present. The pelvis comprises the ilium, ischium and pubis, the last of which does not always ossify in aquatic forms. The sutural contacts between elements may also be visible, even when all three ossify. The forelimb comprised

10804-415: The beginning of the Triassic, and quickly diversified to become among the dominant groups of fish in both freshwater and marine habitats. The vast supercontinent of Pangaea dominated the globe during the Triassic, but in the latest Triassic ( Rhaetian ) and Early Jurassic it began to gradually rift into two separate landmasses: Laurasia to the north and Gondwana to the south. The global climate during

10950-401: The bizarre long-necked archosauromorph Tanystropheus ), along with some terrestrial forms like Ticinosuchus and Macrocnemus , have been recovered from this locality. All these fossils date from the Anisian and Ladinian ages (about 242 Ma ago). The Triassic Period ended with a mass extinction, which was particularly severe in the oceans; the conodonts disappeared, as did all

11096-489: 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. Triassic temnospondyls were often the dominant semiaquatic animals in their environments. Large assemblages of Late Triassic metoposaurids with hundreds of individuals preserved together have been found in

11242-415: The classification of modern amphibians, they are either included in the crown group Tetrapoda or the stem of Tetrapoda. Crown-group tetrapods are descendants of the most recent common ancestor of all living tetrapods and stem tetrapods are forms that are outside the crown group. Modern amphibians have recently been suggested as descendants of temnospondyls, which would place them within crown Tetrapoda. Below

11388-417: The conditions necessary to preserve such material are uncommon. The most extensive records come from fine-grained deposits in the Carboniferous and Permian of Germany; the small-bodied and aquatic dissorophoids and the larger stereospondylomorphs are frequently preserved with outlines of soft tissue around the skeleton. Typically preserved features include the outline of the body, external gills, and parts of

11534-449: The connections between vertebrae. The strong backbone and strong limbs of many rhachitomous temnospondyls allowed them to be partially, and in some cases fully, terrestrial. In stereospondylous vertebrae, the pleurocentra have been greatly reduced or lost entirely, with the intercentra enlarged as the main body of the vertebrae. Early concepts of stereospondyl required the pleurocentra to be entirely absent, but newer concepts only require that

11680-415: The contact between the postparietal and exoccipital at the back of the skull, small projections ( uncinate processes ) on the ribs , and a pelvic girdle with each side having a single iliac blade . These shared derived characteristics are called synapomorphies . Temnospondyls are placed as basal tetrapods in phylogenetic analyses, with their exact positioning varying between studies. Depending on

11826-412: The corresponding rocks are referred to as Lower, Middle, or Upper Triassic. The faunal stages from the youngest to oldest are: During the Triassic, almost all the Earth's land mass was concentrated into a single supercontinent , Pangaea ( lit.   ' entire land ' ). This supercontinent was more-or-less centered on the equator and extended between the poles, though it did drift northwards as

11972-506: The dental plates, abundant in the fossils record. Hybodonts , a group of shark-like cartilaginous fish , were dominant in both freshwater and marine environments throughout the Triassic. Last survivors of the mainly Palaeozoic Eugeneodontida are known from the Early Triassic. Temnospondyl amphibians were among those groups that survived the Permian–Triassic extinction. Once abundant in both terrestrial and aquatic environments,

12118-560: The disuse of terms like Labyrinthodontia and Stegocephalia continues. Temnospondyls continue to be heavily involved in the debate over lissamphibian origins. As with evolutionary biology in general, computer-assisted phylogenetic methods have greatly facilitated phylogenetic inference of the relationships of both Temnospondyli at large and specific sub-groups. Other quantitative analyses have addressed morphometrics, biomechanics, Temnospondyls were also documented from an increasingly broad geographic and stratigraphic range in

12264-428: The dominant carnivores in the early Triassic. Phytosaurs were a particularly common group which prospered during the Late Triassic. These long-snouted and semiaquatic predators resemble living crocodiles and probably had a similar lifestyle, hunting for fish and small reptiles around the water's edge. However, this resemblance is only superficial and is a prime-case of convergent evolution. True archosaurs appeared in

12410-402: The dvinosaur Erpetosaurus , the capitosaur Mastodonsaurus and the trematosaur Microposaurus , tusks in the lower jaw pierce the palate and emerge through openings in the top of the skull. Temnospondyls' vertebrae are divided into several segments. In living tetrapods, the main body of the vertebra is a single piece of bone called the centrum , but in temnospondyls, this region

12556-533: The early 19th century, and were initially thought to be reptiles . They were described at various times as batrachians , stegocephalians and labyrinthodonts , although these names are now rarely used. Animals now grouped in Temnospondyli were spread out among several amphibian groups until the early 20th century, when they were found to belong to a distinct taxon based on the structure of their vertebrae. Temnospondyli means "cut vertebrae", as each vertebra

12702-405: The early Triassic, splitting into two branches: Avemetatarsalia (the ancestors to birds) and Pseudosuchia (the ancestors to crocodilians). Avemetatarsalians were a minor component of their ecosystems, but eventually produced the earliest pterosaurs and dinosaurs in the Late Triassic. Early long-tailed pterosaurs appeared in the Norian and quickly spread worldwide. Triassic dinosaurs evolved in

12848-640: The entire Phanerozoic, seeing as it occurred during and immediately after the discharge of titanic volumes of greenhouse gases from the Siberian Traps. The Early Triassic began with the Permian-Triassic Thermal Maximum (PTTM) and was followed by the brief Dienerian Cooling (DC) from 251 to 249 Ma, which was in turn followed by the Latest Smithian Thermal Maximum (LSTT) around 249 to 248 Ma. During

12994-468: 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. The name Temnospondyli was rarely used in the decades that followed. Swedish paleontologist Gunnar Säve-Söderbergh removed embolomeres from

13140-480: The extinct family Cheirolepidiaceae , which first appeared in the Late Triassic, and would be prominent throughout most of the rest of the Mesozoic. No known coal deposits date from the start of the Triassic Period. This is known as the Early Triassic "coal gap" and can be seen as part of the Permian–Triassic extinction event . Possible explanations for the coal gap include sharp drops in sea level at

13286-462: The eye or stomach. An amphibamiform specimen from the Mazon Creek locality was described as having toepad-like features. The holotype specimen of Arenaerpeton supinatus from the Triassic of New South Wales, Australia, displays extensive soft tissue, hinting at the girth of the animal in life. Trace fossils attributed to temnospondyls are fairly common, especially from the Carboniferous through

13432-475: The first-known complete skull of a temnospondyl. 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. Owen's " Labyrinthodon Jaegeri " was later found at Guy's Cliffe , England by paleontologist William Buckland . Other specimens were found in

13578-448: The genus. 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 1828, basing it on partial occiput, or back portion of the skull. In 1833, he described a complete skull of S. giganteus that had the same teeth as his Mastodonsaurus , making it

13724-521: The global ocean triggered intense cross-equatorial monsoons , sometimes referred to as the Pangean megamonsoons . The Triassic may have mostly been a dry period, but evidence exists that it was punctuated by several episodes of increased rainfall in tropical and subtropical latitudes of the Tethys Sea and its surrounding land. Sediments and fossils suggestive of a more humid climate are known from

13870-496: The group, narrowing its scope to rhachitomes and stereospondyls. His classification of labyrinthodonts was based heavily on characteristics of the skull rather than the vertebrae. The American paleontologist Alfred Romer brought the name Temnospondyli back into use in the later 20th century. Säve-Söderbergh used the name Labyrinthodontia in a strict sense ( sensu stricto ) to refer to Rhachitomi and Stereospondyli, excluding Embolomeri. Romer agreed with this classification, but used

14016-481: 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. Another group was called Microsauria by Cope in 1868. 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

14162-420: The impact. So, the evidence suggests the Manicouagan impact preceded the end of the Triassic by approximately 10±2 Ma. It could not therefore be the immediate cause of the observed mass extinction. The number of Late Triassic extinctions is disputed. Some studies suggest that there are at least two periods of extinction towards the end of the Triassic, separated by 12 to 17 million years. But arguing against this

14308-482: The import of this disparity is also unclear. Many temnospondyls also have canal-like grooves in their skulls called sensory sulci , the presence of which is used to infer an aquatically inclined lifestyle. The sulci, which usually run around the nostrils and eye sockets, are part of a lateral line system used to detect vibrations in water in modern fish and certain modern amphibians. Many taxa, especially those inferred to have been terrestrial, have an opening at

14454-489: 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 a separate group of reptiliomorphs or stem-group tetrapods , with no particular affinities to temnospondyls. In 1888, von Zittel divided stegocephalians among three taxa: Lepospondyli, Temnospondyli and Stereospondyli . He placed microsaurs in Lepospondyli,

14600-588: The intercentrum has become greatly enlarged. This weaker type of backbone indicates that stereospondylous temnospondyls spent more time in water. Additional types that are less common are the plagiosaurid-type in which there is a single enlarged centrum of uncertain homology; and the tupilakosaurid-type vertebrae (diplospondyly) in which the pleurocentra and intercentra are the same size and form discs; this occurs in tupilakosaurid dvinosaurs but also at least some brachyopids and several other non-temnospondyls. The neural spines tend to be of similar height throughout

14746-401: The keystone predators of most Triassic terrestrial ecosystems. Over 25 species have been found, including giant quadrupedal hunters, sleek bipedal omnivores, and lumbering beasts with deep sails on their backs. They probably occupied the large-predator niche later filled by theropods. "Rauisuchians" were ancestral to small, lightly-built crocodylomorphs, the only pseudosuchians which survived into

14892-717: The late 19th and early 20th centuries. 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

15038-426: The latest occurrences of dissorophoids ( Anakamacops , Kamacops ). During the late Permian , increasing aridity and the diversification of reptiles contributed to a decline in terrestrial temnospondyls, but semiaquatic and fully aquatic stereospondylomorph temnospondyls continued to flourish, including the large Melosaurus of Eastern Europe. Other temnospondyls, such as archegosaurids , developed long snouts and

15184-545: The mammaliaforms to develop fur and a higher metabolic rate . Two Early Triassic lagerstätten (high-quality fossil beds), the Dienerian aged Guiyang biota and the earliest Spathian aged Paris biota stand out due to their exceptional preservation and diversity . They represent the earliest lagerstätten of the Mesozoic era and provide insight into the biotic recovery from the Permian-Triassic mass extinction event. The Monte San Giorgio lagerstätte, now in

15330-453: The marine reptiles except ichthyosaurs and plesiosaurs . Invertebrates like brachiopods and molluscs (such as gastropods ) were severely affected. In the oceans, 22% of marine families and possibly about half of marine genera went missing. Though the end-Triassic extinction event was not equally devastating in all terrestrial ecosystems, several important clades of crurotarsans (large archosaurian reptiles previously grouped together as

15476-481: The midline near the tip of the snout called the internarial fenestra / fontanelle; this may have housed a mucous gland used in prey capture. In zatracheids , this opening is greatly enlarged for an unknown purpose. Homologues of most of the bones of temnospondyls are also seen in other early tetrapods, aside from a few bones in the skull, such as interfrontals , internasals and interparietals , that have developed in some temnospondyl taxa. The intertemporal,

15622-744: The midwestern United States, such as the Linton, Five Points and Mazon Creek lagerstätte , and the south-central United States where classic redbed formations are found; and from western Europe, particularly the Saar-Nahe Basin in Germany and Nýřany in the Czech Republic. The early Permian record of temnospondyls is also concentrated in these regions. Most of the clades from the Late Carboniferous continued to be successful, with

15768-458: The modern Pacific Ocean . Practically all deep-ocean crust present during the Triassic has been recycled through the subduction of oceanic plates, so very little is known about the open ocean from this time period. Most information on Panthalassan geology and marine life is derived from island arcs and rare seafloor sediments accreted onto surrounding land masses, such as present-day Japan and western North America. The eastern edge of Pangea

15914-565: 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... and because the second element of the word, saurus , indicates a false affinity, the remains belonging, not to the Saurian, but to the Batrachian order of Reptiles." Owen recognized that the animal was not a " saurian " reptile, yet he also referred Jaeger's Phytosaurus to

16060-414: 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. More recent study of temnospondyls has largely focused on their paleobiology and resolving their internal relationships. With a few exceptions, the monophyly of Temnospondyli is not questioned, and

16206-430: The next most common tetrapods, and early dinosaurs, passed through unchanged. However, both phytosaurs and aetosaurs were among the groups of archosaur reptiles completely wiped out by the end-Triassic extinction event. It seems likely then that there was some sort of end-Carnian extinction, when several herbivorous archosauromorph groups died out, while the large herbivorous therapsids —the kannemeyeriid dicynodonts and

16352-404: The notion that reptiles evolved from a sequential progression from early amphibians (what he called "metamorphosed fishes"). In addition to Mastodonsaurus , some of the earliest-named genera included Metopias and Rhombopholis in 1842, Zygosaurus in 1848, Trematosaurus in 1849, Baphetes and Dendrerpeton in 1853, Capitosaurus in 1858, and Dasyceps in 1859. Baphetes

16498-421: The only known batrachomorphs to do so with the exception of the modern crab-eating frog . Another group, the capitosauroids , included medium-sized and large animals 2.3 to 4 m (7.5 to 13.1 ft) in length, with large and flat skulls that could be over a meter long in the largest forms such as Mastodonsaurus . These animals spent most or all their lives in water as aquatic predators, catching their prey by

16644-402: The order Isoetales (which contains living quillworts ), rose to prominence due to the environmental instability following the Permian-Triassic extinction, with one particularly notable example being the genus Pleuromeia , which grew in columnar like fashion, sometimes reaching a height of 2 metres (6.6 ft). The relevance of lycophytes declined from the Middle Triassic onwards, following

16790-578: The order in which it belonged. 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

16936-635: The overlying Maleri Formation, which also preserves fossils of temnospondyls and archosauromorphs. The main difference between the Yerrapalli and the Maleri faunae is the presence of dicynodonts in the former. The discovery of dicynodont fossils in the Pranhita-Godavari Basin in 1964 was one of the earliest indications that the Yerrapalli Formation represented a distinct paleofauna. Before this discovery, Yerrapalli strata were grouped within

17082-741: The paucity of complete manuses casts doubt on the sweeping characterization of a four-fingered manus as the predominant or plesiomorphic condition. At least in Metoposauridae , there are both taxa with four fingers and taxa with five. The hindlimb comprised the typical tibia, fibula, femur and pes. Relative development is as with the forelimb. All temnospondyls with a known pes have five digits. Unlike modern amphibians, many temnospondyls are covered in small, closely packed scales. 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

17228-504: The period progressed. Southern Pangea, also known as Gondwana , was made up by closely-appressed cratons corresponding to modern South America , Africa , Madagascar , India , Antarctica , and Australia . North Pangea, also known as Laurussia or Laurasia , corresponds to modern-day North America and the fragmented predecessors of Eurasia . The western edge of Pangea lay at the margin of an enormous ocean, Panthalassa ( lit.   ' entire sea ' ), which roughly corresponds to

17374-452: The presacral region of the trunk, but some temnospondyls exhibit increasing height towards the mid-trunk, followed by a decrease in height to produce a more hump-backed contour. The most extreme is observed in the dissorophid Platyhystrix , which has greatly elongated neural spines that form a large sail on its back. The function of this sail, like that of the contemporaneous sphenacodontids and edaphosaurids , remains enigmatic, but it

17520-458: The problem). However, there are many other possible hypotheses for the purpose of the ornamentation (e.g., increasing surface area for better adhesion of the skin to the skull), and the function(s) remains largely unresolved due to the absence of this feature in lissamphibians. Some temnospondyls also exhibit raised tubercles or pustules instead of pits and grooves (e.g., the dissorophoid Micropholis , plagiosaurine plagiosaurids ), and

17666-650: 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

17812-487: The return of more stable environmental conditions. While having first appeared during the Permian, the extinct seed plant group Bennettitales first became a prominent element in global floras during the Late Triassic, a position they would hold for much of the Mesozoic. In the Southern Hemisphere landmasses of Gondwana, the tree Dicroidium , an extinct " seed fern " belong to the order Corystospermales

17958-487: The same bones found in other early tetrapods. Among the most distinguishing features of temnospondyls are the interpterygoid vacuities, two large holes in the back of the palate . Recent studies have suggested that these large openings provided additional attachment sites for musculature and that many temnospondyls were capable of retracting their eyeballs through the vacuities, which is observed in modern frogs and salamanders that also have these large palatal openings; there

18104-451: The skin. Several groups of temnospondyls have large bony plates ( osteoderms ) on their backs. One temnospondyl, Peltobatrachus , has armour-like plating that covers both its back and underside. The rhytidosteid Laidleria also has extensive plating on its back. Most members of the family Dissorophidae also have armor, although it only covers the midline of the back with one or two narrow rows of plates that tightly articulated with

18250-434: The southwestern United States, Morocco, India, and western Europe. 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 transporting and accumulating dead individuals in certain areas. Temnospondyls reached a peak diversity during the Early Triassic, and progressively declined throughout

18396-499: The spine, as they would have limited flexibility and may have been connected by strong ligaments. A carapace of osteoderms is also seen in plagiosaurids , the only primarily aquatic clade with such extensive ossifications. Plagiosaurids may have inherited their armor from a terrestrial ancestor, as both Peltobatrachus and Laidleria have been considered close relatives of the group. Alternatively, these osteoderms may have served as mineral reservoirs to allow plagiosaurids to respond to

18542-412: The structure of their vertebrae. Early forms, with complex vertebrae consisting of a number of separate elements, were placed in the suborder Rachitomi, and large Triassic aquatic forms with simpler vertebrae were placed in the suborder Stereospondyli. With the recent growth of phylogenetics , this classification is no longer viable. The basic rhachitomous condition is found in many primitive tetrapods, and

18688-595: The subsequent Middle and Late Triassic, with only members of the Brachyopoidea and Trematosauroidea surviving into the Jurassic and the Cretaceous. Among brachyopoids, the brachyopids Gobiops and Sinobrachyops are known from Middle and late Jurassic deposits across Asia and the chigutisaurid Siderops is known from the Early Jurassic of Australia. The most recent known temnospondyl

18834-661: The suffix - suchus . The largest taxa, which were predominantly the Mesozoic stereospondyls, had skulls exceeding one meter in length, and the entire animal would have been several meters in length (for reference, the largest living amphibian, Andrias , is about 1.8 meters in body length). Others are smaller and resemble salamanders, in particularly the amphibamiform and micromelerpetid dissorophoids. Skulls are generally parabolic to triangular in shape when viewed from above, and they were particularly flattened in semiaquatic to aquatic taxa, with dorsally facing orbits. The skull

18980-676: The terminus of the Triassic, there was an extreme warming event referred to as the End-Triassic Thermal Event (ETTE), which was responsible for the Triassic-Jurassic mass extinction. Bubbles of carbon dioxide in basaltic rocks dating back to the end of the Triassic indicate that volcanic activity from the Central Atlantic Magmatic Province helped trigger climate change in the ETTE. During the Early Triassic, lycophytes , particularly those of

19126-595: The terrestrial species had mostly died out during the extinction event. The Triassic survivors were aquatic or semi-aquatic, and were represented by Tupilakosaurus , Thabanchuia , Branchiosauridae and Micropholis , all of which died out in Early Triassic, and the successful Stereospondyli , with survivors into the Cretaceous Period. The largest Triassic stereospondyls, such as Mastodonsaurus , were up to 4 to 6 metres (13 to 20 ft) in length. Some lineages (e.g. trematosaurs ) flourished briefly in

19272-577: The time of the Permo-Triassic boundary; acid rain from the Siberian Traps eruptions or from an impact event that overwhelmed acidic swamps; climate shift to a greenhouse climate that was too hot and dry for peat accumulation; evolution of fungi or herbivores that were more destructive of wetlands; the extinction of all plants adapted to peat swamps, with a hiatus of several million years before new plant species evolved that were adapted to peat swamps; or soil anoxia as oxygen levels plummeted. Before

19418-426: The two groups. Whether temnospondyls are considered part of the tetrapod crown or stem thus depends on their inferred relationship to lissamphibians. In 2000, Adam Yates and Anne Warren defined the name Temnospondyli as applying to the clade encompassing all organisms that are more closely related to Eryops than to the “ microsaur ” Pantylus . By this definition, if lissamphibians are temnospondyls and Pantylus

19564-428: The typical radius, ulna, humerus and manus. These bones are typically more developed with greater surface area for muscle attachment in taxa inferred to have been terrestrial. Many dissorophoids have long and slender limbs. Historically it has been thought that all temnospondyls had only four fingers, but this has been shown not to be true in at least a few stereospondyls ( Metoposaurus , Paracyclotosaurus ), and

19710-431: The underside of the skull, the pterygoid ; large openings called interpterygoid vacuities are present between the pterygoids; the stapes (a bone involved in hearing) is connected to the parasphenoid and projects upward; the cleithrum , a bone in the pectoral girdle , is thin; and part of the vertebra called the interdorsal attaches to the neural arch . Additional features were given by Godfrey et al. (1987), including

19856-410: The vertebrae, and osteoderms are also known from a few trematopids. Other temnospondyls, such as Eryops , have been found with small, disc-like bony scutes that were in life probably embedded in the skin. All of these temnospondyls were adapted to a terrestrial lifestyle. Armor may have offered protection from predators in the case of Peltobatrachus . The scutes may have provided stability for

20002-415: The water only to breed. These temnospondyls were some of the first vertebrates fully adapted to life on land. Although temnospondyls are amphibians, many had characteristics such as scales and large armour-like bony plates (osteoderms) that generally distinguish them from the modern soft-bodied lissamphibians ( frogs and toads , newts , salamanders and caecilians ). Temnospondyls have been known since

20148-399: The water. 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 (251.0–245.0 Mya) one group of successful long-snouted fish-eaters, the trematosauroids , even adapted to a life in the sea,

20294-615: Was a dominant element in forest habitats across the region during the Middle-Late Triassic. During the Late Triassic, the Ginkgoales (which today are represented by only a single species, Ginkgo biloba ) underwent considerable diversification. Conifers were abundant during the Triassic, and included the Voltziales (which contains various lineages, probably including those ancestral to modern conifers), as well as

20440-673: Was a relatively cool period known as the Early Norian Cool Interval (ENCI), after which occurred the Mid-Norian Warm Interval (MNWI) from 217 to 209 Ma. The MNWI was briefly interrupted around 214 Ma by a cooling possibly related to the Manicouagan impact . Around 212 Ma, a 10 Myr eccentricity maximum caused a paludification of Pangaea and a reduction in the size of arid climatic zones. The Rhaetian Cool Interval (RCI) lasted from 209 to 201 Ma. At

20586-505: Was accompanied by huge volcanic eruptions that occurred as the supercontinent Pangaea began to break apart about 202 to 191 million years ago (40Ar/39Ar dates), forming the Central Atlantic Magmatic Province (CAMP), one of the largest known inland volcanic events since the planet had first cooled and stabilized. Other possible but less likely causes for the extinction events include global cooling or even

20732-431: Was divided into a pleurocentrum and intercentrum . Two primary types of vertebrae are recognized in temnospondyls: stereospondylous and rhachitomous vertebrae. In rhachitomous vertebrae, the intercentra are large and wedge-shaped, and the pleurocentra are relatively small blocks that fit between them. Both elements support a spine-like neural arch, and well-developed interlocking projections called zygapophyses strengthen

20878-484: Was encroached upon by a pair of extensive oceanic basins: The Neo-Tethys (or simply Tethys) and Paleo-Tethys Oceans . These extended from China to Iberia, hosting abundant marine life along their shallow tropical peripheries. They were divided from each other by a long string of microcontinents known as the Cimmerian terranes . Cimmerian crust had detached from Gondwana in the early Permian and drifted northwards during

21024-466: Was later placed as a labyrinthodont with other temnospondyls, but confusion existed for many years over the classification of small amphibians. By the end of the 19th century, most of what are today regarded as temnospondyls were placed in the suborder Labyrinthodonta. The American paleontologist Ermine Cowles Case called it Labyrinthodonta vera or "true labyrinthodonts". The names Stegocephalia and Labyrinthodontia were used interchangeably to refer to

21170-451: Was named in 1834 by Friedrich August von Alberti , after a succession of three distinct rock layers (Greek triás meaning 'triad') that are widespread in southern Germany : the lower Buntsandstein (colourful sandstone ) , the middle Muschelkalk (shell-bearing limestone ) and the upper Keuper (coloured clay ). On the geologic time scale , the Triassic is usually divided into Early , Middle , and Late Triassic Epochs , and

21316-495: Was the giant chigutisaurid Koolasuchus , known from the Early Cretaceous ( Aptian ) of Australia . It is thought to have survived in rift valleys that were too cold in the winter for crocodylomorphs that normally would have competed with them. Koolasuchus was one of the largest of the brachyopoids, with an estimated weight of 500 kg (1,100 lb). Originally, temnospondyls were classified according to

#753246