Eusthenopteron

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Eusthenopteron
Temporal range:
Ma
↓
Life restoration of Eusthenopteron foordi
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Sarcopterygii
Clade: Tetrapodomorpha
Clade: Eotetrapodiformes
Family: †Tristichopteridae
Genus: †Eusthenopteron
Whiteaves, 1881
Species[1]
  • E. foordi (type)
  • E. farloviensis
  • E. jenkinsi
  • E. obruchevi
  • E. savesoderberghi
  • E. traquairi
  • E. wenjukowi

Eusthenopteron (from

period, about 385 million years ago. It has attained an iconic status from its close relationship to tetrapods. Early depictions of animals of this genus show them emerging onto land, but paleontologists now widely agree that eusthenopteron species were strictly aquatic animals.[3]

The genus was first described by J. F. Whiteaves in 1881, as part of a large collection of fishes from Miguasha, Quebec, Canada.[4] Some 2,000 Eusthenopteron specimens have been collected from Miguasha, one of which was the object of intensely detailed study and several papers by paleoichthyologist Erik Jarvik between the 1940s and the 1990s.[5]

Description

Eusthenopteron foordi
Reconstruction of Eusthenopteron
Head of Eusthenopteron (model)

Eusthenopteron is a medium- to large-sized

tristichopterid. The species E. foordi is estimated to have exceeded 1.5 m (4 ft 11 in) in length, while the species E. jenkinsi probably reached 2.1 m (6 ft 11 in).[6][1]

The earliest known fossilized evidence of bone marrow has been found in Eusthenopteron, which may be the origin of bone marrow in tetrapods.[7]

Eusthenopteron shares many unique features among fishes but in common with the earliest-known tetrapods. It shares a similar pattern of skull roofing bones with stem tetrapoda forms such as Ichthyostega and Acanthostega. Eusthenopteron, like other tetrapodomorph fishes, had internal nostrils (or a choana), one of the defining traits of tetrapodomorphs, including tetrapods. It also had labyrinthodont teeth, characterized by infolded enamel, which characterizes all of the earliest known tetrapods as well.

Unlike the early tetrapods, Eusthenopteron did not have larval gills.[8]

Classification

In Late Devonian vertebrate speciation, descendants of pelagic lobe-finned fish—like Eusthenopteron—exhibited a sequence of adaptations: * Panderichthys, suited to muddy shallows; * Tiktaalik with limb-like fins that could take it onto land; * Early tetrapods in weed-filled swamps, such as: * Acanthostega which had feet with eight digits, * Ichthyostega with limbs. Descendants also included pelagic lobe-finned fish such as coelacanth species.
Model of Eusthenopteron at the American Museum of Natural History

Like other fish-like sarcopterygians, Eusthenopteron possessed a two-part

dentine and enamel; this loss appears to be a synapomorphy with more crownward tetrapodomorphs.[10]

Eusthenopteron differs significantly from some later

lepidotrichia cover all of the fins, which does not happen until after metamorphosis in genera like Polydon (the American paddlefish). This might indicate that Eusthenopteron developed directly, with the hatchling
already attaining the adult's general body form (Cote et al., 2002).

See also

References

  1. ^
    S2CID 51883892
    .
  2. ^ Miller, S. A. (Samuel Almond) (1889). North American geology and palæontology for the use of amateurs, students, and scientists. Cincinnati, O. : [Western Methodist book concern]. p. 597. Retrieved 6 January 2022.
  3. ^ M. Laurin, F. J. Meunier, D. Germain, and M. Lemoine 2007. A microanatomical and histological study of the paired fin skeleton of the Devonian sarcopterygian Eusthenopteron foordi. Journal of Paleontology 81: 143–153.
  4. doi:10.1080/00222938109487434
    .
  5. ^ Geological Survey of Canada (7 February 2008). "Past lives: Chronicles of Canadian Paleontology: Eusthenopteron - the Prince of Miguasha". Archived from the original on 11 December 2004. Retrieved 10 February 2009.
  6. ^ a b Schultze, H.-P. 1984. Juvenile specimens of Eusthenopteron foordi Whiteaves, 1881 (Osteolepiform rhipidistian, Pisces) from the Late Devonian of Miguasha, Quebec, Canada. Journal of Vertebrate Paleontology 4: 1-16.
  7. doi:10.1098/rspb.2014.0299
  8. ^ Amphibian evolution : the life of early land vertebrates (page 141)
  9. ^ M. Laurin, F. and J. Meunier 2012. A microanatomical and histological study of the fin long bones of the Devonian sarcopterygian Eusthenopteron foordi. Acta Zoologica 93: 88–97.
  10. ^ Zylberberg, L., Meunier, F. J. and Laurin, M. 2010. A microanatomical and histological study of the postcranial dermal skeleton in the Devonian sarcopterygian Eusthenopteron foordi. Acta Palaeontologica Polonica 55: 459–470.

External links

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