Not to be confused with the extinct genus of fish Helodus.
Henodus (from Greek: ἑνόςhenós, 'one' and Greek: ὀδούςodoús, 'tooth') is an extinct placodont of the Late Triassic period during the early Carnian age. Fossils of Henodus chelyops were found in the Estherienschichten Member of the Grabfeld Formation, near Tübingen, Germany.[1] It was around 1 metre (3.3 ft) in length. The single species within the genus is H. chelyops.[2][3]
Artist's conceptionReconstruction of filter feeding individuals
Henodus, like many other placodonts, had a superficial resemblance to a turtle. Like turtles, it had a shell formed from a plastron on the underside and a carapace on top. The carapace extended well beyond the limbs, and was made up of individual plates of bony scutes covered by plates of horn. However, the shell was composed of many more pieces of bone than that of turtles, forming a mosaic pattern.[4] The armor was fused to its spine, and its limbs were situated in normal positions, unlike the turtle, where they are located inside the ribcage. The weak limbs of Henodus suggest it spent little, if any time on land.
Henodus also had a single tooth on each side of its mouth, though the remaining teeth were replaced by a beak. In addition, it had baleen-like denticles along the jaws, which combined with a unique feature of the hyoid and musculature indicative of rapid jaw closing indicate a filter feeding lifestyle.[5][6] The head was squared-off at the front, just ahead of the eyes.
Paleo-ecologyedit
More recently, however, it has been suggested that this placodont was an aquatic herbivore, scraping off vegetation from the bottom with its broad jaws. This suggestion has been brought up in a paper discussing the habits and morphology of Atopodentatus, another Mesozoic aquatic reptile formerly suggested to be a filter-feeder and bearing strongly convergent jaw adaptations, including a similar "hammerhead" jaw tips, though unlike Atopodentatus it's still believed that Henodus relied on filter feeding to obtain plant-matter from the substrates.[7]
Referencesedit
^"Fossilworks: Gateway to the Paleobiology Database". www.fossilworks.org. Retrieved 25 January 2022.
^Henodus chelyops, ein neuer placodontier. - Sonder-Abduck aus Palaeontographica Beiträge zur Naturgeschichte der Vorzeit, Abteilung A 84:99-148. - F. von Huene - 1936.
^Der Dritte Henodus ergänzungen zur Kenntnis des PlacodontiersHenodus chelyops Huene. - Sonder-Abdruck aus Palaeontographica Beiträge zur Naturgeschichte der Vorzeit, Abteilung A 89:105-114. - F. von Huene - 1938.
^Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 71. ISBN1-84028-152-9.
^Rieppel, O. (2002). Feeding mechanisms in Triassic stem-group sauropterygians: the anatomy of a successful invasion of Mesozoic seas Zoological Journal of the Linnean Society, 135, 33-63
^Li Chun, Olivier Rieppel, Cheng Long and Nicholas C. Fraser, The earliest herbivorous marine reptile and its remarkable jaw apparatus, Science Advances 06 May 2016: Vol. 2, no. 5, e1501659 DOI: 10.1126/sciadv.1501659
Rieppel, O. (2002). Feeding mechanisms in Triassic stem-group sauropterygians: the anatomy of a successful invasion of Mesozoic seas. Zoological Journal of the Linnean Society, 135, 33-63
henodus, confused, with, extinct, genus, fish, helodus, from, greek, ἑνός, henós, greek, ὀδούς, odoús, tooth, extinct, placodont, late, triassic, period, during, early, carnian, fossils, chelyops, were, found, estherienschichten, member, grabfeld, formation, n. Not to be confused with the extinct genus of fish Helodus Henodus from Greek ἑnos henos one and Greek ὀdoys odous tooth is an extinct placodont of the Late Triassic period during the early Carnian age Fossils of Henodus chelyops were found in the Estherienschichten Member of the Grabfeld Formation near Tubingen Germany 1 It was around 1 metre 3 3 ft in length The single species within the genus is H chelyops 2 3 HenodusTemporal range Late Triassic 237 227 Ma PreꞒ Ꞓ O S D C P T J K Pg NSkeleton of Henodus at the American Museum of Natural HistoryScientific classificationDomain EukaryotaKingdom AnimaliaPhylum ChordataClass ReptiliaSuperorder SauropterygiaOrder PlacodontiaFamily HenodontidaeGenus HenodusHuene 1936Species H chelyopsBinomial name Henodus chelyopsHuene 1936Henodus is the only placodont thus far found in non marine deposits suggesting it may have lived in brackish or freshwater lagoons Contents 1 Description 2 Paleo ecology 3 References 4 Further readingDescription edit nbsp Artist s conception nbsp Reconstruction of filter feeding individualsHenodus like many other placodonts had a superficial resemblance to a turtle Like turtles it had a shell formed from a plastron on the underside and a carapace on top The carapace extended well beyond the limbs and was made up of individual plates of bony scutes covered by plates of horn However the shell was composed of many more pieces of bone than that of turtles forming a mosaic pattern 4 The armor was fused to its spine and its limbs were situated in normal positions unlike the turtle where they are located inside the ribcage The weak limbs of Henodus suggest it spent little if any time on land Henodus also had a single tooth on each side of its mouth though the remaining teeth were replaced by a beak In addition it had baleen like denticles along the jaws which combined with a unique feature of the hyoid and musculature indicative of rapid jaw closing indicate a filter feeding lifestyle 5 6 The head was squared off at the front just ahead of the eyes Paleo ecology editMore recently however it has been suggested that this placodont was an aquatic herbivore scraping off vegetation from the bottom with its broad jaws This suggestion has been brought up in a paper discussing the habits and morphology of Atopodentatus another Mesozoic aquatic reptile formerly suggested to be a filter feeder and bearing strongly convergent jaw adaptations including a similar hammerhead jaw tips though unlike Atopodentatus it s still believed that Henodus relied on filter feeding to obtain plant matter from the substrates 7 References edit Fossilworks Gateway to the Paleobiology Database www fossilworks org Retrieved 25 January 2022 Henodus chelyops ein neuer placodontier Sonder Abduck aus Palaeontographica Beitrage zur Naturgeschichte der Vorzeit Abteilung A 84 99 148 F von Huene 1936 Der Dritte Henodus erganzungen zur Kenntnis des Placodontiers Henodus chelyops Huene Sonder Abdruck aus Palaeontographica Beitrage zur Naturgeschichte der Vorzeit Abteilung A 89 105 114 F von Huene 1938 Palmer D ed 1999 The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals London Marshall Editions p 71 ISBN 1 84028 152 9 Rieppel O 2002 Feeding mechanisms in Triassic stem group sauropterygians the anatomy of a successful invasion of Mesozoic seas Zoological Journal of the Linnean Society 135 33 63 Naish D 2004 Fossils explained 48 Placodonts Geology Today 20 4 153 158 Li Chun Olivier Rieppel Cheng Long and Nicholas C Fraser The earliest herbivorous marine reptile and its remarkable jaw apparatus Science Advances 06 May 2016 Vol 2 no 5 e1501659 DOI 10 1126 sciadv 1501659Further reading editNational Geographic December 2005 p 79 by Virginia Morrell Dixon Dougal The Complete Book of Dinosaurs Hermes House 2006 Huene F von 1936 Henodus chelyops ein neuer Placodontier Palaeontographica A 84 99 147 Rieppel OC and Zanon RT 1997 The interrelationships of Placodontia Historical Biology Vol 12 pp 211 227 Rieppel O 2000 Sauropterygia I Placodontia Pachypleurosauria Nothosauroidea Pistosauroidea Handbuch der Palaoherpetologie Teil 12A Munchen Friedrich Pfeil Rieppel O 2002 Feeding mechanisms in Triassic stem group sauropterygians the anatomy of a successful invasion of Mesozoic seas Zoological Journal of the Linnean Society 135 33 63 Darren Naish Fossils explained 48 Placodonts Blackwell Publishing Ltd Geology Today Vol 20 No 4 July August 2004 online nbsp Media related to Henodus at Wikimedia Commons nbsp Paleontology portal Retrieved from https en wikipedia org w index php title Henodus amp oldid 1211549521, wikipedia, wiki, book, books, library,
