Drepanolepis

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Drepanolepis
Drepanolepis.png
Reconstruction of Drepanolepis maerssae
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Thelodonti
Order:
Furcacaudiformes
Genus:
Drepanolepis
Species

Drepanolepis maerssae

Drepanolepis is an extinct genus of thelodont which lived in Canada during the Early Devonian period. They are considered a "traditional" thelodont and are classified by their forked tails.

Morphology[]

Drepanolepis possessed a tall, angelfish-like body, with a ventral mouth and a hypocercal tail. The gill atrium is large for this order, and the nasal runs down to the oral cavity from the orbit. The oral cavity is jawless, with no premaxilla or maxilla present.[1]

Classification[]

There is debate about whether Drepanolepis is a thelodont at all. The other traditional thelodonts, Thelodus and Loganellia, possess ventral oral cavities similar to that of sturgeons, or of whale sharks. Drepanolepis, on the other hand, along with the rest of the Furcacaudiformes, possess a lancelet-like oral cavity that is not classified as a proper mouth. The one existing fossil to be restored with a terminal mouth, and the guiding specimen for classification of Drepanolepis as a thelodont, is considered to be guess work, and the fact that no other Furcacaudiformes have shown evidence of this backs up that claim. For this reason some suggest that Drepanolepis is better classified as sister taxa to Birkenia.[2][3]

References[]

  1. ^ Wilson, Mark V. H.; Caldwell, Michael W. (1993-02-01). "New Silurian and Devonian fork-tailed 'thelodonts' are jawless vertebrates with stomachs and deep bodies". Nature. 361: 442–444. doi:10.1038/361442a0. ISSN 0028-0836.
  2. ^ Blom, Henning (September 2008). "A New Anaspid Fish from the Middle Silurian Cowie Harbour Fish Bed of Stonehaven, Scotland". Journal of Vertebrate Paleontology. 28: 594–600 – via JSTOR.
  3. ^ Wilson, Mark V. H.; Caldwell, Michael W. (1998). "The Furcacaudiformes: A New Order of Jawless Vertebrates with Thelodont Scales, Based on Articulated Silurian and Devonian Fossils from Northern Canada". Journal of Vertebrate Paleontology. 18 (1): 10–29. ISSN 0272-4634.


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