Lethiscus

Lethiscus Temporal range: Early Carboniferous
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Sarcopterygii
Clade:	Tetrapodomorpha
Order:	†Aistopoda
Family:	†Lethiscidae Wellstead, 1982
Genus:	†Lethiscus Wellstead, 1982
Species:	†L. stocki
Binomial name
†Lethiscus stocki Wellstead, 1982

Lethiscus is the earliest known representative of the Aistopoda, a group of very specialised snake-like tetrapodomorphs known from the early Carboniferous (Mississippian).

Lethiscus is known from only a single specimen from the Holkerian Stage (Middle Viséan) of the Early Carboniferous (Middle Mississippian) of Scotland, and is one of the oldest known post Devonian tetrapods. Despite its very early date, it was already a highly advanced animal.

The skull is specialised and light, very like that of Ophiderpeton, with the orbits, far forward, and the cheek region unossified (lacking bone). There are approximately 30 closely spaced teeth on the maxilla and dentary, and a sutural pattern of the skull closely resembles that of the Late Carboniferous aïstopod Oestocephalus.

There is no trace of limbs. However, unlike later members of the aïstopod lineage, the vertebrae still possess intercentra, and the pleurocentra are large.

Lethiscus is the only representative of the family Lethiscidae. Owing to its early date, it has since its discovery been considered ancestral to later aïstopods, and more recent cladistic research (Anderson et al. 2003) confirms its position as the most basal (primitive) aistopod. A 2017 cladistic analysis incorporated new data on Lethiscus found all aïstopods, including Lethiscus, to be stem-tetrapods, rendering Lepospondyli polyphyletic.^[1]

References

• Anderson, Jason S.; Carroll, Robert L. & Rowe, Timothy B. (2003). "New information on Lethiscus stocki (Tetrapoda: Lepospondyli: Aistopoda) from high-resolution computed tomography and a phylogenetic analysis of Aistopoda". Can. J. Earth Sci. 40 (8): 1071–1083. Bibcode:2003CaJES..40.1071A. doi:10.1139/e03-023.^{[permanent dead link]}
• Carroll, R.L (1988), Vertebrate Paleontology and Evolution, WH Freeman & Co. pp. 176–7
• Wellstead, C.F. (1982). "A Lower Carboniferous aïstopod amphibian from Scotland". Palaeontology. 25: 193–208.

Footnotes

External links

• Aistopoda - phylogeny

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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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