Gogonasus

Gogonasus Temporal range: Late Devonian PreꞒ Ꞓ O S D C P T J K Pg N
Skull (left) and articulated pectoral girdle bones (right) of G. andrewsae
Life restoration of G. andrewsae
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Sarcopterygii
Infraclass:	Tetrapodomorpha
Superorder:	?Osteolepidida
Order:	?Osteolepiformes
Family:	?Osteolepidae
Genus:	Gogonasus Long, 1985
Species:	G. andrewsae
Binomial name
Gogonasus andrewsae Long, 1985

Gogonasus (meaning "snout from Gogo") was a lobe-finned fish known from three-dimensionally preserved 380-million-year-old fossils found from the Gogo Formation in Western Australia. It lived in the Late Devonian period, on what was once a 1,400-kilometre-long (870 mi; 760 nmi) coral reef off the Kimberley coast surrounding the northwest of Australia. Gogonasus was a small fish reaching 30 to 40 centimetres (12 to 16 in) in length.^[1]

Its skeleton shows several features that were like those of a four-legged land animal (tetrapod). They included the structure of its middle ear, and its fins show the precursors of the forearm bones, the radius and ulna. Researchers believe it used its forearm-like fins to dart out of the reef to catch prey.

Gogonasus was first described from a single snout (ethmosphenoid) by John A. Long (1985). On Long's 1967 expedition to Gogo the first relatively complete skull of Gogonasus was found by Chris Nelson and after being prepared by Sheila Mahala Andrews solved a scientific controversy by showing that the inner large fangs of the coronoid bones did not insert into the choana of the palate (Long 1988) as had been suggested by Rosen et al. (1981) for Eusthenopteron. In 1990 a combined expedition from the Western Australian Museum and the Australian National University yielded another almost complete skull of Gogonasus, this one found by Dr R. E. Barwick. The full description of its cranial anatomy appeared in Long, J. A., Barwick, R. E. & Campbell, K.S.W. (1997), although not all aspects of the skull were clear then even from the three specimens. In 2005 Long led another expedition back to Gogo and on July 11 one of the team members, Dr Tim Senden from the Australian National University, found a very well-preserved skeleton of Gogonasus, containing almost the complete fish down to the tip of the tail. It was Dr Senden's first field trip with the other researchers.

The specimen (NMV P221807) is now held at Museums Victoria, after nearly four months of acetic acid preparation by John Long. The new specimen showed some surprising new data not seen in any of the other specimens. Firstly, there were large spiracular openings on top of the skull, with a distinct down-folded cosmine-covered lamina of bone present on the tabular bone. This indicated its spiracles were almost as large as in the elpistostegalian fishes (like Tiktaalik) and early tetrapods (e.g. Acanthostega). Secondly, after preparation of its pectoral fins, the internal limb skeleton showed closer resemblances to that of the elpistostegalians than to other more generalised tetrapodomorph fishes like Eusthenopteron. For almost 100 years Eusthenopteron had been the well-used role model for demonstrating stages in the evolution of lobe-finned fishes to tetrapods. Gogonasus now replaces Eusthenopteron in being a better preserved representative without any ambiguity in interpreting its anatomy (as had been shown for example by Rosen et al. 1981 when erroneously reconstructing the fit of the lower jaws to the palate). Superficially, Gogonasus appears similar to the generalised tetrapodomorph fishes like Osteolepis from Scotland, but in its advanced features shows that even primitive-looking cosmine-covered forms evolved significant specializations towards becoming tetrapod-like.

Gogonasus is just one of the over 45 species of three-dimensionally preserved fishes from the Gogo Formation deposit. It is the only Devonian site in the world to yield whole complete fishes in perfect uncrushed preservation in some specimens.

See also

Other fish found in fossils from the Devonian period:

• Mcnamaraspis kaprios, another fish from the Gogo Formation and Western Australia's fossil emblem
• Elpistostege
• Tiktaalik
• Eusthenopteron
• Panderichthys
• Actinistia
• Materpiscis

References

External links

• Ancient Gogonasus advances evolution, Museum Victoria.
• Photographs and x-ray micro-tomography animation of Gogonasus from ANU
• Gogonasus andrewsae by PZ Myers
• Ancient Fish Fossil May Rewrite Story of Animal Evolution (National Geographic)
• Livescience.com: "Discovery Points to Our Fishy Heritage." (Accessed 10/21/06)
• Fox News: Primitive Fish Skeleton May Link Land, Sea
• Interview with Dr John Long, curator at the Museum of Victoria

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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)
Devonian taxa †Acanthostega †Brittagnathus †Densignathus †Elpistostege? †Hynerpeton †Ichthyostega †Jakubsonia †Metaxygnathus †Parmastega †Sinostega †Tiktaalik? †Tulerpeton †Tutusius †Umzantsia †Ventastega †Ymeria †Elginerpetontidae Elginerpeton Obruchevichthys Webererpeton Post-Devonian taxa †Antlerpeton †Aytonerpeton †Crassigyrinus †Diploradus †Doragnathus †Gaiasia †Ichthyerpeton †Koilops †Mesanerpeton †Occidens †Ossirarus †Perittodus †Sigournea †Tantallognathus †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 †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 Crown group Tetrapoda Temnospondyli (Batrachomorpha see Temnospondyli 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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