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23.01.2016 00:59 - Largest prehistoric animals Vol.1 Vertebrates part12 Fish - Sarcopterygii-Coelacanthis and Ichthyodectids
Автор: valentint Категория: Забавление   
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Последна промяна: 03.12.2016 02:46


Lobe-finned fish (Sarcopterygii)

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The largest of these was the 6 metres (20 ft) long
Rhizodus.
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Rhizodus (Root tooth) is an extinct genus of rhizodont, a branch of the Sarcopterygii, the bony vertebrate clade that also includes tetrapods. It was of enormous size, reaching 6–7 m in length.The most notable characteristics of Rhizodus, when compared to other giant lobe-fins such as Barameda, were the two giant 22 cm fangs located near the front of its jaws followed by other teeth scaling downwards in size. Rhizodus was a giant apex predator that resided in freshwater lakes, river systems and large swamps in the entire Carboniferous period, feeding on small to medium sized amphibians (ranging from 30 cm and 600 cm in size), using its teeth to kill prey and rip it into digestible sizes, rather than swallowing prey whole like other, smaller-toothed sarcopterygii.

Rhizodus is the type genus of the Rhizodontida, a fairly large group of lobe-finned fishes, many genera of which are known from deposits in Australia. Most remains of Rhizodus however are known from Ireland and Scotland, though some reports suggest that Rhizodus might have also been active in North America as well, something that is plausible given that North America and Europe were not separated by the Atlantic during the Carboniferous.
Out of all of the rhizodonts, Rhizodus seems to have been the largest of the group. A single jaw of Rhizodus has been measured at just a little under one meter long, indicating that the individual it belonged to would have been six, possibly as much as seven meters long. This means that Rhizodus might have even been just a bit longer than the largest recorded Great White shark (Carcharodon carcharias) which was accurately measured at just a bit over six meters long. The teeth of Rhizodus were also long and fang-like, and as much as twenty-two centimetres long. These teeth and large physical size suggest that Rhizodus were apex predators that hunted other large fish, primitive sharks and probably even temnospondyl amphibians.


Barameda mitchelli

Barameda (Ancient Greek, "Heavy Guardian") is a genus of rhizodontlobe-finned fish which lived during the Carboniferous period in Australia.While many Paleozoicsarcopterygan fishes are identified by their fleshy lobe fins, fused skull cases and basal qualities, the primary identifier of most Barameda fossils comes from their large rooted fangs, usually 22 centimetres (8.7 in) in length, and where the order Rhizodontida and family Rhizodontidae gain their name. The largest member of this genus, Barameda decipiens, reached an estimated length of over 20 feet (6.1 m), rivaling another large rhizodont in size, Rhizodus. Barameda were obligate carnivores, relying on the meat of Carboniferous ammonites, orthocones, freshwater invertebrates, early fish and early tetrapods to sustain its massive length.

The Barameda has an extremely elongated and thick body typical of Carboniferousrhizodonts, built for powerful swimming, and out-powering any prey larger than itself. It is covered with durable cosmoid scales all along its body, with thick bony plates covering its head and operculum (gill flaps), a tightly fused Skull roof, and extremely prominent, sharp fangs, devoid of serrations or cutting edges. It had an advanced lateral line system that was elaborated along its pectoral girdle, larger pectoral fins than pelvic fins, with deeply over-lapping scales along its fins, turning the pectoral fin into a large paddle. Its anal fins and secondary dorsal fins form a functional part of its tail.

Barameda would ambush early tetrapods, which were still restricted to laying their eggs in water. It employed a "grab and drag" strategy using the highly pronounced fangs at their premaxillae to snag slippery prey and either thrash them at the top of the water, or drag them down and pin them under water. This hunting behavior is common amongst living members of Sarcopterygii when hunting air-breathing prey and slippery, fast moving prey. Its mandibles also rotated inwards towards each other when biting prey, securing any prey item caught from escaping. Barameda most likely used this mechanism to subdue any evasive prey that whose struggling could allow them to escape.

Barameda was a higher trophic level predator who preyed upon a large variety of species, with no predators other than its larger relative Rhizodus. Tropical sharks during the Carboniferous were smaller than most lobefins and posed little threat to healthy adult individuals, and any large eugeneodonts such as the 21 feet (6.4 m) Parahelicoprion were restricted deep-sea environments or isolated from larger members of Rhizodontidae.

Hyneria
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As a lobe finned fish, Hyneria would have looked like a larger version of Eusthenopteron. It had powerful fins, but the popularised image of Hyneria using them to crawl across land is to date only speculation. It’s likely that they would have been of more use while navigating shallow waters and submerged obstacles. In terms of being a predator, Hyneria would have been predators of other fish including sharks as well as temnospondyl amphibians.
The size of Hyneria has been open to a lot of debate over the years. In the 2005 series Walking with Monsters Hyneria was portrayed as a five meter long fish, though where this size estimate came from is uncertain, and is also questionable given the that the Walking With... series of shows tend to have a history of overestimating the size of prehistoric creatures (such as the portrayal of the pliosaur Liopleurodon being twenty-five meters long when the largest specimen is only seven, or the pterosaur Ornithocheirus presented with a twelve meter wingspan when fossils indicate a six meter wingspan). The actual fossils of individual Hyneria actually point to a more modest size of between two and four meters long. If you have come to this page expecting to find a really large lobe-finned fish, then you should check out the genus Rhizodus, a giant six to seven meter long predator.


Edenopteron
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Edenopteron is a genus of large tristichopterid fish from the Late Devonian (Famennian) of what is now southeastern Australia. It is known from a single specimen of a single species, E. keithcrooki, described in 2013.

Edenopteron keithcrooki is known from remains excavated from the Worange Point Formation, near the town of Eden on the coast of New South Wales in 2008. The species name is a combination of the name Eden and pteron, meaning wing or fin in Greek. The specific name honors Dr. Keith Crook of the Australian National University for his discovery of several fossil sites in New South Wales.

The holotype consists of numerous semi-articulated remains, including an incomplete skull roof, snout, palate, cheeks, lower jaws and associated dermal bones, a left shoulder girdle, and assorted scales. Reconstructions suggest a skull length of 30 cm (12 in) and lower jaw length of about 48 cm (19 in). The endoskeleton shows a large or complete lack of ossification. The orbits (eye-sockets) are somewhat triangular rather than oval-shaped. Edenopteron possessed dentary fangs and premaxillary tusks, which are presumed to be derived traits for other large tristichopterids. By comparison to body size ratios of other tristichopterid fishes (e.g. Eusthenodon, Langlieria, Mandageria), the body length of Edenopteron is estimated at 2.9—3.2 m (9.5—10.5 ft).Additional fossil material may be described in the future: according to lead researcher Gavin Young, quoted in the Canberra Times: "We know that part of the pectoral girdle is still in the rock, so if we can lift up a few more blocks, we might find that the body is actually preserved in the rock

 

 

 

Coelacanthiformes

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Mawsonia  gigas-Up to 4 meters long, though isolated fossils suggest that rare individuals may have grown slightly larger than this.
Mawsonia is an extinct genus of prehistoric coelacanth fish, and the largest of this group, up to several metres long.It lived during the Cretaceous period (Albian stage, about 99 to 112 million years ago). Fossils have been found in Africa and South America. Mawsonia was first described by British palaeontologist Arthur Smith Woodward in 1907.

Coelacanths are one of the few creatures that typify animal life in the Mesozoic that are still alive today. Modern coelacanths are represented by the genus Latimeria that live in the deep waters of the Indian Ocean, the largest examples of which are known to easily attain lengths of two meters. Back in the early Cretaceous however these fish would have been small fry, with impressively large coelacanths of the Mawsonia genus reaching lengths of up to four meters, double that of the largest observed Latimeria. Because of their large size, Mawsonia are rarely preserved complete, and specimens which are preserved, are usually of smaller individuals under three meters. Skull bones are usually the most common specimens of Mawsonia due to the greater bone density increasing the likelihood of those parts surviving long enough to fossilize.
Mawsonia like other coelacanths were probably predatory fish that would cruise over the sea floor snatching up fish and larger invertebrates that were sheltering in crevices amongst rocks and coral. We do not know for certain however if Mawsonia were nocturnal like the Latimeria coelacanths that we know today. Interestingly, Mawsonia may have been more inclined to stray into shallower waters than what Latimeria are known to. This is because most of the fossil bearing formations that Mawsonia are known from were estuarine and mangrove habitats back in the early Cretaceous.
When fully grown to such a large size, Mawsonia may have had few predators, though larger sharks, pliosaurs and perhaps even spinosaurid dinosaurs, may have still been potential dangers for Mawsonia.


Ichthyodectid (Ichthyodectidae)

The largest of ichthyodectid fish was the 6.0 metres (19.7 ft) long Xiphactinus
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Xiphactinus (from Latin and Greek for "sword-ray") is an extinct genus of large, 4.5 to 6 m (15 to 20 feet) long predatory marine bony fish that lived during the Late Cretaceous. When alive, the fish would have resembled a gargantuan, fanged tarpon (to which it was, however, not related).The species Portheus molossus described by Cope is a junior synonym of X. audax. Skeletal remains of Xiphactinus have come from Kansas (where the first Xiphactinus fossil was discovered during the 1850s) Alabama, and Georgia in the United States, as well as Europe, Australia, Canada and Venezuela.

Species of Xiphactinus were voracious predatory fish. At least a dozen specimens of X. audax have been collected with the remains of large, undigested or partially digested prey in their stomachs. In particular, one 13 feet (4.0 m) fossil specimen was collected by George F. Sternberg with another, nearly perfectly preserved 6 feet (1.8 m) long ichthyodectid Gillicus arcuatus, inside of it. The larger fish apparently died soon after eating its prey, most likely due to the smaller fish prey struggling and rupturing an organ as it was being swallowed. This fossil can be seen at the Sternberg Museum of Natural History in Hays, Kansas.

Like many other species in the Late Cretaceous oceans, a dead or injured individual was likely to be scavenged by sharks (Cretoxyrhina and Squalicorax). The remains of a Xiphactinus were found within a large specimen of Cretoxyrhina collected by Charles H. Sternberg. The specimen is on display at the University of Kansas Museum of Natural History.

Virtually nothing is known about the larval or juvenile stages. The smallest fossil specimen of X. audax consists of a tooth bearing premaxilla and lower jaws of an individual estimated to be about 12 inches (30 cm) long.

The species and all other ichthyodectids went extinct near the end of the Late Cretaceous - see Cretaceous–Paleogene extinction event.

An incomplete skull of what may be a new species of Xiphactinus was found in 2002 in the Czech Republic, in a small town called Sachov next Borohradek city, by student Michal Matejka.

In July 2010 the bones of a Xiphactinus were discovered near Morden, Manitoba, Canada. The specimen is about six metres long and was found with the flipper of a mosasaur between its jaws.


Ichthyodectes ctenodon
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Ichthyodectes ctenodon ("Fish Biter (with) Comb Teeth") was a 4-metre long ichthyodectid. It lived in the Western Interior Seaway of North America during the late Cretaceous. It was closely related to the 4 to 6 metre long Xiphactinus audax, and the 2-metre long Gillicus arcuatus, and like other ichthyodectids, I. ctenodon is presumed to have been a swift predator of smaller fish. As its species name suggests, I. ctenodon had small, uniformly sized teeth, as did its smaller relative, G. arcuatus, and may have simply sucked suitably sized prey into its mouth.











 

 



Тагове:   сова,   prehistoric animals,   giant animals,   giant fish,


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Автор: valentint
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