Letognathus

Letognathus is a genus of rhizodont tetrapodomorph that lived during the Carboniferous period.^[1] Its remains come from the Blue Beach Member of the Horton Bluff Formation, near Hantsport, Nova Scotia. Like most rhizodonts, it was of relatively large size, had a large recurved fang at the symphysis of the lower jaw, and a row of three coronoid fangs along the length of the jaw in addition to its marginal dentition. Letognathus is important for rhizodont systematics because it retains a number of primitive features, such as ossified Meckel's cartilage, are not found in the genera Rhizodus and Strepsodus.

Taxonomic History

The members of the Rhizodontida have nearly all had complex taxonomic histories^[2] due to earlier use of the genus Strepsodus as a wastebasket taxon. The taxon was originally assigned to the genus Rhizodus by John William Dawson and later to Strepsodus by Arthur Smith Woodward. A new genus was erected for the Horton Bluff material based on a number of differences from either Strepsodus or Rhizodus.

References

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Tetrapodomorpha (Pan-Tetrapoda)

Kingdom: Animalia Phylum: Chordata Clade: Osteichthyes Clade: Sarcopterygii Clade: Rhipidistia
Gnathostomata see Gnathostomata Tetrapodomorpha see below↓

Tetrapodomorpha
Tetrapodomorpha †Bogdanovia †Chrysolepis †Geptolepis †Glyptopomus †Gogonasus †Greiserolepis †Gyroptychius †Harajicadectes †Kenichthys †Litoptychus †Lamprotolepis †Latvius †Medoevia †Megadonichthys †Muranjilepis †Osteolepis †Peregrina †Platyethmoidia †Shirolepis †Thaumatolepis †Thursius †Tungsenia †Viluichthys †Rhizodontida Archichthys Aztecia Barameda Gooloogongia Hongyu Letognathus Propycnoctenion Pycnoctenion Rhizodus Rossichthys Sauripterus Screbinodus Strepsodus Thysanolepis? Vorobjevaia? †Canowindridae Beelarongia Canowindra Koharalepis Marsdenichthys? Owensia? †Megalichthyidae Askerichthys Cladarosymblema Cryptolepis? Ectosteorhachis Lohsania? Mahalalepis Megalichthys Megapomus? Megistolepis? Palatinichthys Rhizodopsis Sengoerichthys Sterropterygion? Eotetrapodiformes †Palaeospondylus? †Tristichopteridae Bruehnopteron Cabonnichthys Callistipterus Canningius Devonosteus Edenopteron Eusthenodon Eusthenopteron Heddleichthys Hyneria Jarvikina Langlieria Litoptychus? Mandageria Marsdenichthys? Notorhizodon Platycephalichthys Spodichthys Tinirau Tristichopterus Elpistostegalia †Howittichthys? †Livoniana †Panderichthys †Parapanderichthys †Qikiqtania †Rubrognathus †Tiktaalik Stegocephali (Tetrapoda sensu lato) see below↓

Stegocephali (Tetrapoda sensu lato)
Stegocephali †Acanthostega †Brittagnathus †Densignathus †Elpistostege? †Hynerpeton †Ichthyostega †Jakubsonia †Metaxygnathus †Parmastega †Sinostega †Tulerpeton †Tutusius †Umzantsia †Ventastega †Ymeria †Elginerpetontidae Elginerpeton Obruchevichthys Webererpeton †Aistopoda Andersonerpeton Lethiscus Ophiderpeton Oestocephalidae Coloraderpeton Oestocephalus Phlegethontioidea Pseudophlegethontia Phlegethontiidae Phlegethontia Sillerpeton †Whatcheeriidae Ossinodus? Pederpes Whatcheeria †Colosteidae Colosteus Deltaherpeton Greererpeton Pholidogaster †Adelospondyli Acherontiscus Adelogyrinidae Adelogyrinus Adelospondylus Dolichopareias Palaeomolgophis †"Nectridea" see Nectridea †Baphetoidea Eucritta? Spathicephalus Baphetidae Baphetes Kyrinion Loxomma Megalocephalus †Other post- Devonian genera Antlerpeton Aytonerpeton Crassigyrinus Diploradus Doragnathus Ichthyerpeton Koilops Mesanerpeton Occidens Ossirarus Perittodus Sigournea Tantallognathus †Embolomeri Anthracosaurus Archeria Aversor Calligenethlon Carbonoherpeton "Cricotus" Diplovertebron Eobaphetes Eoherpeton? Leptophractus Neopteroplax Palaeoherpeton Papposaurus Pholiderpeton Proterogyrinus Pteroplax Seroherpeton Spondylerpeton †Gephyrostegidae Bruktererpeton Eusauropleura Gephyrostegus †Other "anthracosaurs" Caerorhachis Casineria? Eldeceeon Eoherpeton Silvanerpeton Termonerpeton Tetrapoda (crown group) Temnospondyli (Batrachomorpha?) see Temnospondyli likely includes Lissamphibia Reptiliomorpha (Pan-Amniota) see Reptiliomorpha includes Amniota

Related topics
Paraphyletic / Polyphyletic groups Stem tetrapoda Osteolepiformes Osteolepididae Megalichthyiformes? Tristichopteridae? Labyrinthodontia Rachitomi Ichthyostegalia Lepospondyli Holospondyli Phyllospondyli Anthracosauria Other topics Evolution of tetrapods Polydactyly in stem-tetrapods Romer's gap Timeline Zachelmie trackways

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