Потребителски вход

Запомни ме | Регистрация
Постинг
16.01.2016 23:46 - Largest prehistoric animals Vol.1 Vertebrates part10 Amphibians ch.2 Brachiopoids,Frogs and Diacectids
Автор: valentint Категория: Забавление   
Прочетен: 193 Коментари: 0 Гласове:
0

Последна промяна: 03.12.2016 02:55


Brachiopoids
Koolasuchus
at 16 ft long, but only 1 ft high.


Koolasuchus is an extinct genus of brachyopoid temnospondyl in the family Chigutisauridae. Fossils have been found from Victoria, Australia and date back 120 Ma to the Aptian stage of the Early Cretaceous. Koolasuchus is the latest known temnospondyl. Koolasuchus is known from several fragments of the skull and other bones such as vertebrae, ribs, and pectoral elements. The type species K. cleelandi was named in 1997.

Koolasuchus was an aquatic temnospondyl estimated to have been around 4 to 5 metres (13 to 16 ft) in length.Its mass has been estimated to be up to 500 kilograms (1,100 lb). Although represented by incomplete material, the skull was likely 65 centimetres (26 in) long.Like other chigutisaurids, it had a wide, rounded head and tabular horns projecting from the backside of the skull.

Koolasuchus was named in 1997 from the Aptian Strzelecki Group of the Wonthaggi Formation in Victoria.It is known from four fragments of the lower jaw and several postcranial bones, including ribs, vertebrae, a fibula, and parts of the pectoral girdle. A jawbone was found in 1978 in a fossil site known as the Punch Bowl near the town of San Remo. Later specimens were found in 1989 on the nearby Rowell's Beach. A partial skull is also known but has not been fully prepared. Koolasuchus was named for the palaeontologistLesley Kool. The name is also a pun on the word "cool" in reference to the cold climate of its environment.The type species K. cleelandi is named after geologistMike Cleeland.

Koolasuchus inhabited rift valleys in southern Australia during the Early Cretaceous. During this time the area was below the Antarctic Circle, and temperatures were relatively cool for the Mesozoic. Based on the coarse-grained rocks in which remains were found, Koolasuchus likely lived in fast-moving streams. As a large aquatic predator, it had a similar lifestyle to crocodilians. Although crocodilians were common during the Early Cretaceous, they were absent from southern Australia 120 million years ago, possibly because of the cold climate. By 110 Ma, represented by rocks in the Dinosaur Cove fossil locality, temperatures had warmed and crocodilians had returned to the area. These crocodilians likely displaced Koolasuchus, leading to its disappearance in younger rocks.

However, an unnamed Late Triassic or Early Jurassic brachiopoid from Lesotho in southern Africa is estimated to have been far larger. At an estimated 7 metres (23 ft), the brachiopoid from Lesotho is one of the largest amphibians sensu lato ever known.This estimate is based on a single jaw fragment found in 1970 by a French expedition near Alwynskop in Quthing.

Because of its size, the fragment was initially considered to be from a mastodonsaur.However, the specimen was redescribed as a brachyopoid in 2005. Several features of the specimen indicate that it is from a brachyopoid. There is a large tusk protruding from the ectopterygoid, a bone of the palate, and the dental morphology is similar to that of other brachyopoids. When viewed from the side, the upper margin of the jaw appears concave.

 

Frogs (Anura)
The largest known frog ever was the 16-inch-long (41 cm) Beelzebufo ampinga, weighing 10 pounds (4.5 kg)


 

Beelzebufo ampinga was a particularly large species of prehistoric frog described in 2008. Common names assigned by the popular media include devil frog, devil toad, and the frog from hell.

Fossils of Beelzebufo have been recovered from strata of the Maevarano Formation in Madagascar, dating to the late Cretaceous period, some 70 million years ago (Mya).

The generic name Beelzebufo is a portmanteau of Beelzebub (a Semitic deity whose name may be translated as "Lord of the Flies", sometimes identified either as one of the chief lieutenants, or alter ego of the Christian Devil) and bufo (Latin for "toad").

The specific name ampinga means "shield" in Malagasy.

The species may have grown to 41 cm (16 in) and 4.5 kg (9.9 lb) — larger than any living frogs,including the largest known species, the goliath frog, which can be up to 32 cm (13 in). The head was big, and bones of the skull roof show a rugous external surface, indicating at least parts of the head may have borne bony scales, called scutes.

The skull sutures are open in even the biggest species of Beelzebufo, showing that it may have grown even bigger.

Although the fossils of Beelzebufo appear in what is now Madagascar, which, still attached to India, had split from the coast of Somalia in the earliest stage of the late Jurassic, it superficially resembles its closest living relatives, the horned toads of South America, of which the largest today grow to 15 cm (6 in) long.

As West Gondwana (South America) rifted away from East Gondwana, opening from the north and spreading southward, open marine conditions in the widening South Atlantic obtained by about 110 Mya, isolating the amphibians on either side; the last common ancestor of Beelzebufo and the South American Ceratophryidae is most likely to have existed before that date and probably before seafloor-spreading demonstrates the earlier isolation of Madagascar-India, a very long time undocumented by fossils.

Alternatively, the history of archaeogeography could be rewritten: Richard Lane, program director in NSF's Division of Earth Sciences, said, "The occurrence of this frog in Madagascar and its relatives' existence in South America provides strong evidence that the supercontinent Gondwana 'disassembled' during the latest part of the Cretaceous."

In comparison with the living Ceratophryidae, Beelzebufo most likely was a predator whose expansive mouth allowed it to eat relatively large prey, perhaps even juvenile dinosaurs.

The first fossil fragments were found in 1993 by David W. Krause of New York's Stony Brook University, but it took 14 years for scientists Susan E. Evans, Marc E. H. Jones, and Krause to assemble enough data for publication in the Proceedings of the National Academy of Sciences, the journal of the United States National Academy of Sciences.

Some 75 fossil fragments have been found. Researchers have been able to reconstruct parts of the frog's skeleton, including nearly the entire skull.

Diadectomorpha

The largest known Diacectids, Diadectes, was a heavily built animal, 1.5 to 3 meters long, with thick vertebrae and ribs.

Diadectes (meaning crosswise-biter) is an extinct genus of large, very reptile-like amphibians that lived during the early Permian period (Cisuralian epochs, between 290 and 272 million years ago). Diadectes was one of the very first herbivorous tetrapods, and also one of the first fully terrestrial animals to attain large size.

Diadectes was a heavily built animal, 1.5 to 3 meters long, with a thick-boned skull, heavy vertebrae and ribs, massive limb girdles and short, robust limbs. The nature of the limbs and vertebrae clearly indicate a terrestrial animal.

It possesses some characteristics of reptilians and amphibians, combining a reptile-like skeleton with a more primitive, seymouriamorph-like skull. Diadectes has been classified as belonging to the sister group of the amniotes.

Among its primitive features, Diadectes has a large otic notch (a feature found in all labyrinthodonts, but not in reptiles) with an ossified tympanum. At the same time its teeth show advanced specialisations for an herbivorous diet that are not found in any other type of early Permian animal. The eight front teeth are spatulate and peg-like, and served as incisors that were used to nip off mouthfuls of vegetation. The broad, blunt cheek teeth show extensive wear associated with occlusion, and would have functioned as molars, grinding up the food. It also had a partial secondary palate, which meant it could chew its food and breathe at the same time, something many even more advanced reptiles were unable to do.

These traits are likely adaptations related to the animals' high-fiber herbivorous diet, and evolved independently of similar traits seen in some reptilian groups. Many of the reptile-like details of the post-cranial skeleton are possibly related to carrying the substantial trunk, these may be independently derived traits on Diadectes and their relatives. Though very similar, they would be anaologous rather than homologous to those of early amniotes like pelycosaurs and pareiasaurs, as the first reptiles evolved from small, swamp dwelling animals like Casineria and Westlothiana.The phenomenon of related animals evolving similarly is known as parallelophyly.

Diadectes was first named and described by the American paleontologist Edward Drinker Cope in 1878,based on part of a lower jaw (AMNH 4360) from the Permian of Texas. Cope noted: "Teeth with short and much compressed crowns, whose long axis is transverse to that of the jaws," the feature expressed in the generic name Diadectes "crosswise biter" (from Greek dia "crosswise" + Greek dēktēs "biter"). He described the animal as "in all probability, herbivorous." Cope's Neo-Latin type species name sideropelicus (from Greek sidēros "iron" + Greek pēlos "clay" + -ikos) "of iron clay" alluded to the Wichita beds in Texas, where the fossil was found. Diadectes fossil remains are known from a number of locations across North America, especially the Texas Red Beds (Wichita and Clear Fork).

Numerous species have been assigned to Diadectes, though most of those have proven to be synonyms of one another. Similarly, many supposed separate genera of diadectids have been shown to be junior synonyms of Diadectes. One of these, Nothodon, was actually published by Othniel Charles Marsh five days before the name Diadectes was published by his rival Edward Drinker Cope. Despite this fact, in 1912 Case synonymized the two names and treated Diadectes as the senior synonym, which has been followed by other paleontologists since, despite the fact that it violates the rules of biological nomenclature.

A phylogenetic analysis of Diadectes and related diadectids was presented in an unpublished Ph.D. thesis by Richard Kissel in 2010. Previous phylogenetic analyses of diadectids had found D. absitus to be more basal than other species of Diadectes, outside the derived clade composed of these species. In these analyses, Diasparactus zenos was more closely related to the other species of Diadectes than was D. absitus, making Diadectes paraphyletic. Kissel recovered this paraphyly in his analysis and proposed the new genus name "Silvadectes" for D. absitus.














 




Гласувай:
0
0



Няма коментари
Търсене

За този блог
Автор: valentint
Категория: Политика
Прочетен: 75337
Постинги: 146
Коментари: 24
Гласове: 11
Архив
Календар
«  Април, 2017  
ПВСЧПСН
12
3456789
10111213141516
17181920212223
24252627282930