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Fossilized remains of "Killer tadpole" reconstructed

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  • Fossilized remains of "Killer tadpole" reconstructed

    The critter in question, Crassigyrinus scoticus,which possessed tiny limbs, large eyes and huge jaws, and could reach up to between 2 and 3 meters in length, has been a bit of a taxonomical puzzler, exhibiting characteristics of both fish and tetrapods. Another nickname for it is the "Tadpole From Hell."

    Source: Scientists reveal face of 10-foot 'killer tadpole' that terrorized Earth long before the dinosaurs

    With huge teeth and large eyes, Crassigyrinus scoticus was specially adapted to hunt in the coal swamps of Scotland and North America.

    Crassigyrinus scoticus lived 330 million years ago in wetlands of what is now Scotland and North America.

    By piecing together fragments of an ancient skull, scientists have reconstructed the haunting face of a 330 million-year-old crocodile-like "tadpole" creature, revealing not only what it looked like but also how it may have lived.

    Scientists have known about the extinct species, Crassigyrinus scoticus, for a decade. But because all known fossils of the primordial carnivore are severely crushed, it has been difficult to find out more about it. Now, advances in computed tomography (CT) scanning and 3D visualization have allowed researchers to digitally piece the fragments back together for the first time, revealing more details about the ancient beast.

    Previous research(opens in new tab) has shown that C. scoticus was a tetrapod, a four-limbed animal related to the first creatures to transition from water to land. Tetrapods began appearing on Earth around 400 million(opens in new tab) years ago, when the earliest tetrapods started evolving from lobe-finned fishes.

    Unlike its relatives, however, past studies(opens in new tab) have found C. scoticus was an aquatic animal. This is either because its ancestors returned from land to the water, or because they never made it to land in the first place. Instead, it lived in coal swamps (opens in new tab) — wetlands which over millions of years would turn into coal stores — in what is now Scotland and parts of North America.

    The new research, carried out by scientists at University College London, shows the animal had huge teeth and powerful jaws. Although its name means “thick tadpole,” the study shows C. scoticus had a relatively flat body and very short limbs, similar to a crocodile or alligator.

    "In life, Crassigyrinus would have been around two to three metres [6.5 to 9.8 feet] long, which was quite big for the time," lead study author Laura Porro(opens in new tab), a lecturer in cell and developmental biology at University College London, said in a statement(opens in new tab). "It would probably have behaved in a way similar to modern crocodiles, lurking below the surface of the water and using its powerful bite to grab prey."

    C. scoticus was also adapted to hunt prey in swampy terrain. The new facial reconstruction shows it had large eyes to see in muddy water, as well as lateral lines, a sensory system that allows animals to detect vibrations in water.

    A reconstruction of C. scoticus skull from crushed bone fragments.

    lthough much more is known about C. scoticus, scientists are still puzzled by a gap near the front of the animal’s snout. According to Porro, the gap may indicate that C. scoticus had other senses to help it hunt. It may have had a so-called rostral organ that helped the creature detect electric fields, Porro said. Alternatively, C. scoticus might have had a Jacobson's organ, which is found in animals such as snakes and helps to detect different chemicals.

    In earlier studies, Porro said, scientists reconstructed C. scoticus with a very tall skull, similar to that of a Moray eel. "However, when I tried to mimic that shape with the digital surface from CT scans, it just didn't work," Porro explained. "There was no chance that an animal with such a wide palate and such a narrow skull roof could have had a head like that."

    The new research, published May 2 in the Journal of Vertebrate Palaeontology(opens in new tab), shows the animal would have had a skull similar in shape to a modern crocodile's. To reconstruct what the animal looked like, the team used CT scans from four separate specimens and pieced the broken fossils together to reveal its face.

    "Once we had identified all of the bones, it was a bit like a 3D-jigsaw puzzle," Porro said. "I normally start with the remains of the braincase, because that's going to be the core of the skull, and then assemble the palate around it."

    The team now plans to carry out biomechanical simulations to test out their ideas about C. scoticus and its capabilities.


    © Copyright Original Source

    The full paper, Computed tomography and three-dimensional reconstruction of the skull of the stem tetrapod Crassigyrinus scoticus Watson, 1929, can be accessed by simply clicking the hyperlink, although I also made the abstract from it available below


    The early tetrapod Crassigyrinus scoticus was a large aquatic predator known from the lower- to mid-Carboniferous (upper Tournasian to upper Visean/lower Serpukovian, approximately 350–330 Ma) of Scotland and Canada. Crassigyrinus is enigmatic in terms of its phylogenetic position due to its unusual morphology, which features a mixture of primitive and derived characters. Previous reconstructions, based on five incomplete and deformed specimens, have suggested a dorsoventrally tall skull with a short and broad snout, large orbits and external nares, and an extended postorbital region. In this study, we scanned four specimens using computed tomography and segmented imaging data to separate bone from matrix and individual bones from each other. Based on these data, we present a revised description of the upper and lower jaws, including sutural morphology and abundant new anatomical information. Damage was repaired and the skull retrodeformed to create a hypothetical three-dimensional reconstruction of the skull of Crassigyrinus that is dorsoventrally flatter than earlier reconstructions, yet still morphologically unique amongst early tetrapods. Overall skull shape, the size and distribution of the teeth, sutural morphology, and the specialized anatomy of the jaw joint and mandibular symphysis all suggest that Crassigyrinus was a powerful aquatic predator capable of hunting and subduing large prey.

    More images

    A reconstruction of what it might have looked like in life

    The crocodilian-like skull. Unfortunately I don't know what the size the scale bar represents

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