Elpistostege

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Elpistostege
Temporal range: Late Devonian
Elpistostege watsoni.jpg
Elpistostege watsoni on display at the Miguasha National Park
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Clade: Stegocephalia
Family: Elpistostegidae
Genus: Elpistostege
Westoll, 1938
Species:
E. watsoni
Binomial name
Elpistostege watsoni
Westoll, 1938

Elpistostege is an extinct genus of finned tetrapodomorphs that lived during the late Givetian to early Frasnian ages of the Late Devonian epoch. Its only known species, E. watsoni, was first described in 1938 by the British palaeontologist Thomas Stanley Westoll, based on a single partial skull roof discovered at the Escuminac Formation in Quebec, Canada.[1]

In 2010, a complete specimen was found in the same formation, which was described by Richard Cloutier and colleagues in 2020. It reveals that the paired fins of Elpistostege contained bones homologous to the phalanges (digit bones) of modern tetrapods; it is the most basal tetrapodomorph known to possess these bones. At the same time, the fins were covered in scales and lepidotrichia (fin rays), which indicates that the origin of phalanges preceded the loss of fin rays, rather than the other way around.[2][3]

Relationships[edit]

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 advanced stem-tetrapods.[4]

Elpistostegalia

Panderichthys Panderichthys BW.jpg

Stegocephalia

Tiktaalik Tiktaalik BW.jpg

Elpistostege

Elginerpeton Elginerpeton BW.jpg

Ventastega

Acanthostega Acanthostega BW.jpg

Ichthyostega Ichthyostega BW.jpg

Whatcheeriidae Pederpes22small.jpg

Colosteidae Greererpeton BW.jpg

Crassigyrinus Crassigyrinus BW.jpg

Baphetidae

Crown group Tetrapoda Seymouria BW.jpg

The 2020 study by Cloutier et al. instead recovers Elpistostege as the sister taxon of all limbed vertebrates, crownward of Tiktaalik:[2]

Panderichthys Panderichthys BW.jpg

Tiktaalik Tiktaalik BW.jpg

Elpistostege

Limbed vertebrates

Ventastega

Acanthostega Acanthostega BW.jpg

Ichthyostega Ichthyostega BW.jpg

Tulerpeton

References[edit]

  1. ^ Westoll, T. S. (1938). "Ancestry of the Tetrapods". Nature. 141 (3559): 127–128. Bibcode:1938Natur.141..127W. doi:10.1038/141127a0. S2CID 4086668.
  2. ^ a b Cloutier, R.; Clement, A. M.; Lee, M. S. Y.; Noël, R.; Béchard, I.; Roy, V.; Long, J. A. (2020). "Elpistostege and the origin of the vertebrate hand". Nature. 579 (7800): 549–554. Bibcode:2020Natur.579..549C. doi:10.1038/s41586-020-2100-8. PMID 32214248. S2CID 213171029.
  3. ^ Geggel, Laura (2020). "Fish sprouted fingers before they ventured onto land, fossil shows". livescience.com.
  4. ^ Swartz, B. (2012). "A marine stem-tetrapod from the Devonian of Western North America". PLOS ONE. 7 (3): e33683. Bibcode:2012PLoSO...733683S. doi:10.1371/journal.pone.0033683. PMC 3308997. PMID 22448265.

External links[edit]