Elpistostege

Elpistostege is an extinct genus of tetrapod-like vertebrate that lived in the Late Devonian period (Late Givetian to Early Frasnian). Fossils of its skull and a part of its backbone have been found in rocks of the Escuminac Formation in Quebec, Canada. A complete specimen of the animal has since been found in the same formation. It has been proposed, by the palaeontologist Richard Cloutier at Université du Québec à Rimouski, that this species may dethrone its close relative Tiktaalik in the position of the most primitive stem-tetrapod, though phylogenetic analyses have shown them to be very close relatives. The fossil suggests that human hands likely evolved, eventually, from the fins of this fish, according to Cloutier, who claimed "[1]It is the first time that digits, as seen in tetrapods, are found in a fin covered by scales and fin rays, as seen in fishes."

Elpistostege watsoni on display at the Miguasha National Park.

Elpistostege
Temporal range: Late Devonian
Fossil skull
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Stegocephalia
Family: †Elpistostegidae
Genus: †Elpistostege
Species:
†E. watsoni
Binomial name
†Elpistostege watsoni
Westoll, 1938

Relationships

An analysis conducted by Swartz in 2012 found Elpistostege to be the sister taxon of Tiktaalik. Both were found to be primitive members of the group Stegocephalia, along with other primitive stem-tetrapods.[2]

Elpistostegalia
 

Panderichthys

 
Stegocephalia
 
 

Tiktaalik

 
 

Elpistostege

 
 
 
 

Elginerpeton

 
 
 

Ventastega

 
 
 

Acanthostega

 
 
 

Ichthyostega

 
 
 

Whatcheeriidae

 
 
 

Colosteidae

 
 
 

Crassigyrinus

 
 
 

Baphetidae

 
 

Crown group Tetrapoda

 
 
 
 
 
 
 
 
 
 
 

A 2020 paper instead recovers Elpistostege as the sister taxon of all tetrapods, crownward of Tiktaalik:[3]

 
 

Panderichthys

 
 
 
 

Tiktaalik

 
 
 

Elpistostege

 
Tetrapoda (apomorphy‑based)
 

Ventastega

 
 
 

Acanthostega

 
 
 

Ichthyostega

 
 

Tulerpeton

 
 
 
 
 
 
 
 
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References
  1. https://www.livescience.com/ancient-fish-fingers.html
  2. Swartz, B. (2012). "A marine stem-tetrapod from the Devonian of Western North America". PLoS ONE. 7 (3): e33683. doi:10.1371/journal.pone.0033683. PMC 3308997. PMID 22448265.
  3. . doi:10.1038/s41586-020-2100-8. Cite journal requires |journal= (help); Missing or empty |title= (help)


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