RestorationSkull (AMNH 4985)Under surface of the upper jaw and palate of Placodus gigas
Placodus had a stocky body with a long tail, and reached a total length of 2.5–3 m (8.2–9.8 ft).[2] It had a short neck, and a heavy skull. They were specialized for a durophagous diet of shellfish, such as bivalves. Chisel-like incisors protruded from the anterior margin of the snout, and were probably used to pluck hard-shelled benthic prey from the substrate. The back teeth were broad and flattened, and would have helped to crush the prey.[3] Before the animals' anatomy was known, they were regarded as fishes' teeth. Similar smaller teeth were present on the palatine bones.
Placodus and its relatives were not as well-adapted to aquatic life as some later reptile groups, like the closely related plesiosaurs. Their flattened tails and short legs, which probably ended in webbed feet, would have been their main means of propulsion in the water.[3]
The parietal eye on top of the head assisted the animal with orientation, rather than its vision, and its presence is regarded as a primitive characteristic.[citation needed]
The vertebral processes of Placodus dove-tailed into each other and were firmly connected, so that the trunk was rigid. The abdomen was covered with a special armor formed of the bent, right-angled abdominal ribs. Equipped with dense bones, heavy belly ribs, and a row of bony knobs above the backbone, Placodus was a heavily built and negatively buoyant creature that would have had no trouble staying on the seafloor to feed.
This body armour would have offered protection from predators as well, but would have also hampered mobility on land, making Placodus slow and clumsy out of water. It was therefore most likely a terrestrial animal that ventured into the sea in search of food. Molluscs, brachiopods, crustaceans, and other inhabitants of the seabed would have formed its staple diet.
Referencesedit
^Colbert, Edwin H. (Edwin Harris); Knight, Charles Robert (1951). The dinosaur book: the ruling reptiles and their relatives. New York: McGraw-Hill. p. 153.
^Diedrich, C.G. (2010). "Palaeoecology of Placodus gigas (Reptilia) and other placodontids — Middle Triassic macroalgae feeders in the Germanic Basin of central Europe — and evidence for convergent evolution with Sirenia". Palaeogeography, Palaeoclimatology, Palaeoecology. 285: 287–306.
^ abPalmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 70. ISBN1-84028-152-9.
placodus, from, greek, plax, plakos, plate, greek, odous, tooth, extinct, genus, marine, reptiles, belonging, order, placodontia, which, swam, shallow, seas, middle, triassic, period, million, years, fossils, have, been, found, central, europe, germany, france. Placodus from Greek plax plakos a plate and Greek odous tooth 1 is an extinct genus of marine reptiles belonging to the order Placodontia which swam in the shallow seas of the middle Triassic period c 240 million years ago Fossils of Placodus have been found in Central Europe Germany France Poland and China PlacodusTemporal range Middle Triassic 245 235 Ma PreꞒ Ꞓ O S D C P T J K Pg NPlacodus gigasScientific classificationDomain EukaryotaKingdom AnimaliaPhylum ChordataClass ReptiliaSuperorder SauropterygiaOrder PlacodontiaFamily PlacodontidaeCope 1871Genus PlacodusAgassiz 1833Species P gigas Agassiz 1833 type P inexpectatus Jiang et al 2008Palaeobiology edit nbsp Restoration nbsp Skull AMNH 4985 nbsp Under surface of the upper jaw and palate of Placodus gigasPlacodus had a stocky body with a long tail and reached a total length of 2 5 3 m 8 2 9 8 ft 2 It had a short neck and a heavy skull They were specialized for a durophagous diet of shellfish such as bivalves Chisel like incisors protruded from the anterior margin of the snout and were probably used to pluck hard shelled benthic prey from the substrate The back teeth were broad and flattened and would have helped to crush the prey 3 Before the animals anatomy was known they were regarded as fishes teeth Similar smaller teeth were present on the palatine bones Placodus and its relatives were not as well adapted to aquatic life as some later reptile groups like the closely related plesiosaurs Their flattened tails and short legs which probably ended in webbed feet would have been their main means of propulsion in the water 3 The parietal eye on top of the head assisted the animal with orientation rather than its vision and its presence is regarded as a primitive characteristic citation needed The vertebral processes of Placodus dove tailed into each other and were firmly connected so that the trunk was rigid The abdomen was covered with a special armor formed of the bent right angled abdominal ribs Equipped with dense bones heavy belly ribs and a row of bony knobs above the backbone Placodus was a heavily built and negatively buoyant creature that would have had no trouble staying on the seafloor to feed This body armour would have offered protection from predators as well but would have also hampered mobility on land making Placodus slow and clumsy out of water It was therefore most likely a terrestrial animal that ventured into the sea in search of food Molluscs brachiopods crustaceans and other inhabitants of the seabed would have formed its staple diet References edit Colbert Edwin H Edwin Harris Knight Charles Robert 1951 The dinosaur book the ruling reptiles and their relatives New York McGraw Hill p 153 Diedrich C G 2010 Palaeoecology of Placodus gigas Reptilia and other placodontids Middle Triassic macroalgae feeders in the Germanic Basin of central Europe and evidence for convergent evolution with Sirenia Palaeogeography Palaeoclimatology Palaeoecology 285 287 306 a b Palmer D ed 1999 The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals London Marshall Editions p 70 ISBN 1 84028 152 9 nbsp Paleontology portal Retrieved from https en wikipedia org w index php title Placodus amp oldid 1207718536, wikipedia, wiki, book, books, library,
