Project 2495: A. C. Pritchard, A. H. Turner, R. B. Irmis, S. J. Nesbitt, N. D. Smith. 2016. Extreme modification of the tetrapod forelimb in a Triassic diapsid reptile. Current Biology. 26:1-8.
Specimen: † Drepanosaurus (unvouchered)
View: limb

Abstract

The tetrapod forelimb is one of the most versatile structures in vertebrate evolution, having been co-opted for an enormous array of functions. However, the structural relationships between the bones of the forelimb have remained largely unchanged throughout the 375 million year history of Tetrapoda, with a radius and ulna made up of elongate, paralleling shafts contacting a series of shorter carpal bones. These features are consistent across nearly all known tetrapods, suggesting that the morphospace encompassed by these taxa is limited by some sort of constraint(s). Here, we report on a series of three-dimensionally preserved fossils of the small-bodied (<1 m) Late Triassic diapsid reptile Drepanosaurus, from the Chinle Formation of New Mexico, USA, which dramatically diverge from this pattern. Along with the crushed type specimen from Italy, these specimens have a flattened, crescent-shaped ulna with a long axis perpendicular to that of the radius and hyperelongate, shaft-like carpal bones contacting the ulna that are proximodistally longer than the radius. The second digit supports a massive, hooked claw. This condition has similarities to living “hook-and-pull” digging mammals and demonstrates that specialized, modern ecological roles had developed during the Triassic Period, over 200 million years ago. The forelimb bones in Drepanosaurus represent previously unknown morphologies for a tetrapod and, thus, a dramatic expansion of known tetrapod forelimb morphospace.


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Article DOI: http://dx.doi.org/10.1016/j.cub.2016.07.084

Project DOI: 10.7934/P2495, http://dx.doi.org/10.7934/P2495
This project containsMatrices
  • 1 Media
  • 1 Matrix
  • 21 Taxa
  • 1 Specimen
  • 75 Characters
Total size of project's media files: 1 MB

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Total scored cells: 1019
Total media associated with cells: 0
Total labels associated with cell media: 0
Characters
Total characters: 75
Total characters with associated media: 0
Total characters with media with labels: 0
Total character states: 160
Total character states with associated media: 0
Total character states with media with labels:0
Total unordered/ordered characters:69/6
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MorphoBank Project 2495

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    member name taxa specimens media chars character
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    (scored, NPA, "-")
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    Adam Pritchard
    Project Administrator
    Last logged in 09/29/16
    200175001019
    (1001, 0, 18)
    000


    Taxonomic Overview for Matrix 'M24116' (20 Taxa)

    taxon unscored
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    [1] † Petrolacosaurus kansasensis
    Last Modified in 10/06/16
    1737301001
    [2] Shinisaurus crocodilurus
    Last Modified in 10/06/16
    2707003001
    [3] Uromastyx sp.
    Last Modified in 07/13/16
    3707002001
    [5] † Diphydontosaurus avonis
    Last Modified in 10/06/16
    34424100001
    [6] Sphenodon punctatum
    Last Modified in 10/06/16
    0737203001
    [7] † Saurosternon bainii
    Last Modified in 10/06/16
    46282801001
    [8] † Protorosaurus speneri
    Last Modified in 10/06/16
    3717101001
    [9] † Azendohsaurus madagaskarensis
    Last Modified in 10/06/16
    2727201001
    [11] † Macrocnemus bassanii
    Last Modified in 10/06/16
    23525200001
    [12] † Tanystropheus longobardicus
    Last Modified in 10/06/16
    2727201001
    [13] † Claudiosaurus germaini
    Last Modified in 10/06/16
    3717101001
    [14] † Hovasaurus boulei
    Last Modified in 10/06/16
    13626101001
    [15] † Thadeosaurus colcanapi
    Last Modified in 10/06/16
    25494901001
    [16] † Dolabrosaurus aquatilis
    Last Modified in 10/06/16
    55202000001
    [18] † gr113
    Last Modified in 10/06/16
    696600001
    [19] † Drepanosaurus unguicaudatus
    Last Modified in 10/06/16
    37383800001
    [20] † HaydenDrepanosaur
    Last Modified in 10/06/16
    64111100001
    [21] † Hypuronector limnaios
    Last Modified in 10/06/16
    47272701001
    [22] † Megalancosaurus preonensis
    Last Modified in 10/06/16
    22535300001
    [23] † Vallesaurus cenensis
    Last Modified in 10/06/16
    33414101001


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