Project 2553: M. I. Coates, R. W. Gess, J. A. Finarelli, K. E. Criswell, K. Tietjen. 2017. A symmoriiform chondrichthyan braincase and the origin of chimaeroid fishes. Nature. 541 (7636):208-211.
Specimen: Chimaeroidei (unvouchered)
View: Lateral external

Abstract

Chimaeroid fishes (Holocephali) are one of the four principal divisions of modern gnathostomes (jawed vertebrates). Despite only 47 described living species, chimaeroids are the focus of resurgent interest as potential archives of genomic data and for the unique perspective they provide on chondrichthyan and gnathostome ancestral conditions. Chimaeroids are also noteworthy for their highly derived body plan. However, like other living groups with distinctive anatomies, fossils have been of limited use in unraveling their evolutionary origin as the earliest recognized examples already exhibit many of the specializations present in Recent forms. Here we report the results of a Computed Tomography (CT) analysis of Dwykaselachus, an enigmatic chondrichthyan braincase from the ~280 million year old Karoo sediments of South Africa. Externally, the braincase is that of a symmoriid shark and is by far the most complete uncrushed example yet discovered. Internally the morphology exhibits otherwise characteristically chimaeroid specializations, including the otic labyrinth arrangement and the brain space configuration relative to exceptionally large orbits. These results have significant implications for our view of modern chondrichthyan origins, add robust structure to the phylogeny of early crown group gnathostomes, reveal preconditions that suggest an initial morpho-functional basis for the derived chimaeroid cranium, and shed new light on the chondrichthyan response to the end-Devonian extinction.


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Article DOI: 10.1038/nature20806

Project DOI: 10.7934/P2553, http://dx.doi.org/10.7934/P2553
This project containsMatrices
  • 1 Media
  • 1 Matrix
  • 37 Taxa
  • 1 Specimen
  • 145 Characters


Download Project SDD File
Total scored cells: 3472
Total media associated with cells: 0
Total labels associated with cell media: 0
Characters
Total characters: 145
Total characters with associated media: 0
Total characters with media with labels: 0
Total character states: 301
Total character states with associated media: 0
Total character states with media with labels:0
Total unordered/ordered characters:145/0
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MorphoBank Project 2553

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    member name taxa specimens media chars character
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    John Finarelli
    Project Administrator
    Last logged in 01/14/17
    371114500003472
    (3099, 0, 373)
    00000


    Taxonomic Overview for Matrix 'M24326' (37 Taxa)

    taxon unscored
    cells
    scored
    cells
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    NPA
    cells
    "-" cellscell images labels on
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    member
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    [1] † Acanthodes
    Last Modified in 11/08/16
    12115115018001
    [2] † Akmonistion
    Last Modified in 11/08/16
    2910810808001
    [3] † Brochoadmones
    Last Modified in 11/08/16
    89484808001
    [4] Chimaeroidei
    Last Modified in 01/14/17
    1128128016001
    [5] † Chondrenchelys
    Last Modified in 11/08/16
    389191016001
    [6] † Cladodoides
    Last Modified in 11/08/16
    60787807001
    [7] † Cladoselache
    Last Modified in 11/08/16
    53848408001
    [8] † Cobelodus
    Last Modified in 11/08/16
    468888011001
    [9] † Cowralepis
    Last Modified in 11/08/16
    844747014001
    [10] † Debeerius
    Last Modified in 11/08/16
    389696011001
    [11] † Dicksonosteus
    Last Modified in 11/08/16
    34100100011001
    [12] † Doliodus
    Last Modified in 11/08/16
    64727209001
    [13] † Dwykaselachus
    Last Modified in 11/08/16
    69717105001
    [14] † Egertonodus
    Last Modified in 11/08/16
    1134134010001
    [15] † Entelognathus
    Last Modified in 11/08/16
    785757010001
    [16] † Gladbachus
    Last Modified in 11/08/16
    666767012001
    [17] † Guiyu
    Last Modified in 11/08/16
    676868010001
    [18] † Hamiltonichthys
    Last Modified in 11/08/16
    459090010001
    [19] † Helodus
    Last Modified in 11/08/16
    449291010001
    [20] † Iniopera
    Last Modified in 11/08/16
    21111110014001
    [21] † Janusiscus
    Last Modified in 11/08/16
    89484808001
    [22] † Kathemacanthus
    Last Modified in 11/08/16
    844747014001
    [23] † Kawichthys
    Last Modified in 11/08/16
    86555504001
    [24] † Ligulalepis
    Last Modified in 11/08/16
    77626206001
    [25] † Mimipiscis
    Last Modified in 11/08/16
    2131131012001
    [26] † Onychoselache
    Last Modified in 11/08/16
    666969010001
    [27] † Orthacanthus
    Last Modified in 11/08/16
    8127127010001
    [28] † Ozarcus fm 13242
    Last Modified in 11/08/16
    3810010007001
    [29] † Poracanthodes
    Last Modified in 11/08/16
    96424207001
    [30] † Psarolepis
    Last Modified in 11/08/16
    65717109001
    [31] † Ptomacanthus
    Last Modified in 11/08/16
    82555508001
    [32] † Pucapampella
    Last Modified in 11/08/16
    666767012001
    [33] † Ramirosuarezia
    Last Modified in 11/08/16
    88484809001
    [34] Squalus
    Last Modified in 11/08/16
    1131131013001
    [35] † Synechodus
    Last Modified in 11/08/16
    538282010001
    [36] † Tamiobatis
    Last Modified in 11/08/16
    46929207001
    [37] † Tristychius
    Last Modified in 11/08/16
    912712709001


    Project views

    type number of views Individual items viewed (where applicable)
    Total project views8304
    Project overview981
    Media views1429Media search (1177 views); M435792 (252 views);
    Matrix views713Matrix landing page (636 views); Coates et al. Matrix (77 views);
    Taxon list3914
    Specimen list489
    Views for media list483
    Bibliography295




    Project downloads

    type number of downloads Individual items downloaded (where applicable)
    Total downloads from project88
    Project downloads78
    Matrix downloads10Coates et al. Matrix (10 downloads);