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Prehistoric Beasts - Placodus - Specialist Shellfish-Eating Marine Reptile

Hi, welcome to Enchiridion. I am very excited to share with you these facts on Placodus! Placodus was a marine reptile belonging to the order Placodontia that swam in the shallow seas of the Middle Jurassic period roughly 240 million years ago. Fossils of Placodus have been discovered in Central Europe, including Germany, France, and Poland and in China. It had broad, flat tooth plates for crushing the molluscs on which it fed. It resembled a barrel-bodied lizard superficially similar to the marine iguana of today, yet larger. Placodus is one of the most often represented reptiles of the placodont group, and the most common of the ‘un-armored’ type of creatures deemed similar to marine iguanas. Nonetheless, unlike the algae-eating marine iguana, Placodus was a dedicated durophagous shellfish eater. In its search for food, it used specialized forward-pointing incisors to grip and pluck crustaceans and bivalves off the sea floor before taking them into the back of its mouth. At the back of its mouth, an array of flat crushing teeth that extended across the palate broke up the shell so that Placodus could swallow the soft-bodied organisms therein. In other words, 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. Prior to paleontologists knowing the anatomy of Placodus, they were regarded as fishes’ teeth. Similar smaller teeth were present on the palatine bones, at the hard palate. As a marine reptile, Placodus had traits adapted for swimming as well as other features allowing it to still be able to move on land, though it doesn’t seem especially able to do one or the other — thus, it was in intermediate development in these two aspects. In the water, Placodus would have relied on its laterally compressed or sideways-flattened tail for its main propulsion, while the possibly webbed feet and legs could have been used for steering by pushing out against the water to turn the body in the opposite direction. Crustaceans, molluscs, brachiopods, and other creatures from the seabed would have formed its staple diet. Placodus means “flat tooth”. It was named by Louis Agassiz in 1833. Placodus belongs to the Kingdom Animalia, the Phylum Chordata, the Class Reptilia, the Superorder Sauropterygia, the Order Placodontia, the Family Placodontidae, the Genus Placodus, and the Type Species Placodus gigas. Species include the type species, Placodus gigas, and a second species, Placodus inexpectatus, named in 2008 by Jiang et al. It was up to 6.6 feet, or 2 meters long. It lived during the Anisian of the Middle Triassic, 247.2 to 242 million years ago, or roughly 245 to 240 million years ago. As always, thank you for watching. This is Enchiridion, see you next time. Announcement: I will reduce the frequency of weekly videos to 1 and I will incorporate 3D models in the long term, mainly due to the difficulty and time investment of creating such models. :-D #Enchiridion #PrehistoricBeasts #Placodus Table of Contents: 0:00 - Introduction 0:32 - Description 0:43 - A Durophagous Shellfish Eater 1:42 - Able To Swim And Move On Land 2:40 - Neutral Buoyancy 3:06 - Feeding Behavior And A Parietal Eye 3:55 - Description 5:39 - Naming 5:43 - Named By 5:49 - Scientific Classification 6:05 - Species 6:16 - Diet 6:20 - Size 6:25 - Known Locations 6:58 - Time Period 7:11 - Fossil Representation 7:16 - Outro _____ Sources: The braincase and inner ear Of Placodus gigas (Sauropterygia, PLACODONTIA)-A new reconstruction based on micro-computed TOMOGRAPHIC DATA. (n.d.). Retrieved April 10, 2021, from https://www.tandfonline.com/doi/abs/10.1080/02724634.2012.695241 Placodus. (2021, March 14). Retrieved April 10, 2021, from https://en.wikipedia.org/wiki/Placodus Richard, O., Richard Owen Google Scholar Find this author on PubMed Search for more papers by this author, Owen, R., Google Scholar Find this author on PubMed Search for more papers by this author, & This text was harvested from a scanned image of the original document using optical character recognition (OCR) software. As such. (1859, January 01). II. description of the skull and teeth of the placodus Laticeps, Ow .,WITH indications of other new species OF Placodus, and evidence of the saurian nature of that extinct genus. Retrieved April 10, 2021, from https://royalsocietypublishing.org/doi/10.1098/rspl.1857.0034 Sauropterygian. (n.d.). Retrieved April 10, 2021, from https://www.britannica.com/animal/sauropterygian#ref60067 Www.prehistoric-wildlife.com, D. (n.d.). Placodus. Retrieved April 10, 2021, from http://www.prehistoric-wildlife.com/species/p/placodus.html Sues, Hans-Dieter. “On the Skull of Placodus Gigas and the Relationships of the Placodontia.” Journal of Vertebrate Paleontology, vol. 7, no. 2, 1987, pp. 138–144. JSTOR, www.jstor.org/stable/4523133. Accessed 10 Apr. 2021.