Project 748: S. P. Davis, J. A. Finarelli, M. I. Coates. 2012. Acanthodes and shark-like conditions in the last common ancestor of modern gnathostomes. Nature. 486 (7402):247–250.

Abstract

Acanthodians, an exclusively Palaeozoic group of fish, are central to a renewed debate on the origin of modern gnathostomes: jawed vertebrates comprising Chondrichthyes (sharks, rays and ratfish) and Osteichthyes (bony fishes and tetrapods). Acanthodian internal anatomy is primarily understood from Acanthodes bronni because it remains the only example preserved in substantial detail, central to which is an ostensibly osteichthyan braincase. For this reason, Acanthodes has become an indispensible component in early gnathostome phylogenies. Here we present a new description of the Acanthodes braincase, yielding new details of external and internal morphology, notably the regions surrounding and within the ear capsule and neurocranial roof. These data contribute to a new reconstruction that, unexpectedly, resembles early chondrichthyan crania. Principal coordinates analysis of a character-taxon matrix including these new data confirms this impression: Acanthodes is quantifiably closer to chondrichthyans than to osteichthyans. However, phylogenetic analysis places Acanthodes on the osteichthyan stem, as part of a well-resolved tree that also recovers acanthodians as stem chondrichthyans and stem gnathostomes. As such, perceived chondrichthyan features of the Acanthodes cranium represent shared primitive conditions for crown group gnathostomes. Moreover, this increasingly detailed picture of early gnathostome evolution highlights ongoing and profound anatomical reorganization of vertebrate crania after the origin of jaws but prior to the divergence of living clades.


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Project DOI: 10.7934/P748, http://dx.doi.org/10.7934/P748
This project containsMatrices
  • 1 Media
  • 1 Matrix
  • 60 Taxa
  • 138 Characters
Total size of project's media files: 3 MB

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Total scored cells: 4946
Total media associated with cells: 0
Total labels associated with cell media: 0
Characters
Total characters: 138
Total characters with associated media: 0
Total characters with media with labels: 0
Total character states: 279
Total character states with associated media: 0
Total character states with media with labels:0
Total unordered/ordered characters:138/0
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MorphoBank Project 748

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    John Finarelli
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    Last logged in 06/13/12
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    MorphoBank Curator
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    Taxonomic Overview for Matrix 'M1686' (60 Taxa)

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    [1] Acanthodes
    Last Modified in 12/05/13
    10111111017002
    [2] Akmonistion
    Last Modified in 12/05/13
    15105105018002
    [3] Austroptyctodus
    Last Modified in 12/05/13
    478181010002
    [4] Bothriolepis
    Last Modified in 12/05/13
    595454025002
    [5] Brachyacanthus
    Last Modified in 12/05/13
    78525208002
    [6] Brindabellaspis
    Last Modified in 12/05/13
    55757508002
    [7] Brochoadmones
    Last Modified in 12/05/13
    725252014002
    [8] Buchanosteus
    Last Modified in 12/05/13
    358989014002
    [9] Campbellodus
    Last Modified in 12/05/13
    646161013002
    [10] Cassidiceps
    Last Modified in 12/05/13
    834444011002
    [11] Cheiracanthus
    Last Modified in 12/05/13
    557171012002
    [12] Cheirolepis
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    49808009002
    [13] Chondrenchelys
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    318383024002
    [14] Cladodoides
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    74585806002
    [15] Cladoselache
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    338787018002
    [16] Climatius
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    60717107002
    [17] Cobelodus
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    13103103022002
    [18] Coccosteus
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    725454012002
    [19] Cowralepis
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    88434307002
    [20] Culmacanthus
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    [21] Debeerius
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    279090021002
    [22] Dialipina
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    [23] Dicksonosteus
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    329292014002
    [24] Diplacanthus
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    686060010002
    [25] Doliodus
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    705555013002
    [26] Eusthenopteron
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    2119119017002
    [27] Euthacanthus
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    67646407002
    [28] Galeaspida
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    275454057002
    [29] Gladiobranchus
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    656161012002
    [30] Gogonasus
    Last Modified in 12/05/13
    35989805002
    [31] Guiyu
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    56757507002
    [32] Hamiltonichthys
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    309090018002
    [33] Homalacanthus
    Last Modified in 12/05/13
    527373013002
    [34] Howqualepis
    Last Modified in 12/05/13
    45848409002
    [35] Ischnacanthus
    Last Modified in 12/05/13
    59717108002
    [36] Kathemacanthus
    Last Modified in 12/05/13
    695151018002
    [37] Ligulalepis
    Last Modified in 12/05/13
    89474702002
    [38] Macropetalichthys
    Last Modified in 12/05/13
    79535306002
    [39] Mesacanthus
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    666161011002
    [40] Mimia
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    [41] Obtusacanthus
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    824343013002
    [42] Onychodus
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    279696015002
    [43] Onychoselache
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    506969019002
    [44] Orthacanthus
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    19101101018002
    [45] Osteostraci
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    217373044002
    [46] Parexus
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    72606006002
    [47] Poracanthodes
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    81525205002
    [48] Porolepis
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    20104104014002
    [49] Promesacanthus
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    616666011002
    [50] Psarolepis
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    [51] Pterichthyodes
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    784444016002
    [52] Ptomacanthus
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    [53] Pucapampella
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    90434305002
    [54] Rhamphodopsis
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    784848012002
    [55] Tamiobatis
    Last Modified in 12/05/13
    547373011002
    [56] Tetanopsyrus
    Last Modified in 12/05/13
    606565013002
    [57] Tristychius
    Last Modified in 12/05/13
    199898021002
    [58] Lupopsyrus
    Last Modified in 12/05/13
    92444402002
    [59] Rhadinacanthus
    Last Modified in 12/05/13
    104323202002
    [60] Vernicomacanthus
    Last Modified in 12/05/13
    102343402002


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    Bibliography746
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