Project 182: Demere, T. A., M. R. McGowen, A. Berta, and J. G. Gatesy. 2008. Morphological and molecular evidence for a stepwise transition from teeth to baleen in mysticete whales. Systematic Biology. 57 (1):15-37.
Specimen: Aetiocetus weltoni (unvouchered)

Abstract

The origin of baleen in mysticete whales represents a major transition in the phylogenetic history of Cetacea. This key specialization, a keratinous sieve that enables filter-feeding, permitted exploitation of a new ecological niche and heralded the evolution of modern baleen-bearing whales, the largest animals on Earth. To date, all formally described mysticete fossils conform to two types: toothed species from Oligocene-age rocks (approximately 24 to 34 million years old) and toothless species that presumably utilized baleen to feed (Recent to approximately 30 million years old). Here, we show that several Oligocene toothed mysticetes have nutrient foramina and associated sulci on the lateral portions of their palates, homologous structures in extant mysticetes house vessels that nourish baleen. The simultaneous occurrence of teeth and nutrient foramina implies that both teeth and baleen were present in these early mysticetes. Phylogenetic analyses of a supermatrix that includes extinct taxa and new data for 11 nuclear genes consistently resolve relationships at the base of Mysticeti. The combined data set of 27,340 characters supports a stepwise transition from a toothed ancestor, to a mosaic intermediate with both teeth and baleen, to modern baleen whales that lack an adult dentition but retain developmental and genetic evidence of their ancestral toothed heritage. Comparative sequence data for ENAM (enamelin) and AMBN (ameloblastin) indicate that enamel-specific loci are present in Mysticeti but have degraded to pseudogenes in this group. The dramatic transformation in mysticete feeding anatomy documents an apparently rare, stepwise mode of evolution in which a composite phenotype bridged the gap between primitive and derived morphologies; a combination of fossil and molecular evidence provides a multifaceted record of this macroevolutionary pattern.


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Project DOI: 10.7934/P182, http://dx.doi.org/10.7934/P182
This project containsMatrices
  • 1 Media
  • 1 Matrix
  • 3 Documents
  • 79 Taxa
  • 1 Specimen
  • 115 Characters
Total size of project's media files: 2 MB

Download Project SDD File
Total scored cells: 2994
Total media associated with cells: 0
Total labels associated with cell media: 0
Characters
Total characters: 115
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
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MorphoBank Project 182

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    member name taxa specimens media media
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    (scored, NPA, "-")
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    notes  medialabels
    rules
    Annalisa Berta
    Project Administrator
    Last logged in 03/11/09
    790001150002994
    (2994, 0, 0)
    0000
    Tom Demere
    Full membership
    Last logged in 11/03/10
    000000000
    (0, 0, 0)
    0000
    John Gatesy
    Full membership
    Last logged in Never
    000000000
    (0, 0, 0)
    0000
    Michael McGowen
    Full membership
    Last logged in 01/07/08
    000000000
    (0, 0, 0)
    0000
    Natalie Milbrodt
    Full membership
    Last logged in 03/16/12
    000000000
    (0, 0, 0)
    0000


    Taxonomic Overview for Matrix 'M481' (50 Taxa)

    taxon unscored
    cells
    scored
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    "-" cellscell images labels on
    cell images
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    [1] New taxon
    Last Modified in 01/07/08
    1150000005
    [2] Physeter macrocephalus
    Last Modified in 01/08/08
    2293000005
    [3] Ziphiidae
    Last Modified in 01/08/08
    1996000005
    [4] Megaptera novaeangliae
    Last Modified in 01/08/08
    1996000005
    [5] Balaenoptera physalus
    Last Modified in 01/08/08
    1998000005
    [6] Balaenoptera musculus
    Last Modified in 01/08/08
    1996000005
    [7] Balaenoptera borealis
    Last Modified in 01/08/08
    1996000005
    [8] Balaenoptera edeni brydei
    Last Modified in 01/08/08
    1997000005
    [9] Balaenoptera bonaerensis
    Last Modified in 01/08/08
    2095000005
    [10] Balaenoptera acutorostrata
    Last Modified in 01/08/08
    1997000005
    [11] Eschrichtius robustus
    Last Modified in 01/08/08
    1997000005
    [12] Caperea marginata
    Last Modified in 01/08/08
    2096000005
    [13] Balaena mysticetus
    Last Modified in 01/08/08
    2096000005
    [14] Eubalaena
    Last Modified in 01/08/08
    2095000005
    [15] Mammalodon colliveri
    Last Modified in 01/08/08
    6055000005
    [16] Aetiocetus weltoni
    Last Modified in 01/08/08
    4075000005
    [17] Aetiocetus cotylalveus
    Last Modified in 01/08/08
    5164000005
    [18] Aetiocetus polydentatus
    Last Modified in 01/08/08
    4075000005
    [19] Chonecetus goedertorum
    Last Modified in 01/08/08
    4669000005
    [20] Eomysticetus whitmorei
    Last Modified in 01/08/08
    4471000005
    [21] Aglaocetus patulus
    Last Modified in 01/08/08
    5659000005
    [22] Cetotherium rathkii
    Last Modified in 01/08/08
    7441000005
    [23] Cophocetus oregonensis
    Last Modified in 01/08/08
    4075000005
    [24] Diorocetus hiatus
    Last Modified in 01/08/08
    3680000005
    [25] Isanacetus laticephalus
    Last Modified in 01/08/08
    5264000005
    [26] Mixocetus elysius
    Last Modified in 01/08/08
    6253000005
    [27] Parietobalaena palmeri
    Last Modified in 01/08/08
    3780000005
    [28] Pelocetus calvertensis
    Last Modified in 01/08/08
    3283000005
    [29] Balaenoptera
    Last Modified in 01/08/08
    4180000005
    [30] SDSNH 90517
    Last Modified in 01/08/08
    3088000005
    [31] Megaptera
    Last Modified in 01/08/08
    64146000005
    [32] Parabalaenoptera baulinensis
    Last Modified in 01/08/08
    5659000005
    [33] Agorophius
    Last Modified in 01/08/08
    5957000005
    [34] Squalodon calvertensis
    Last Modified in 01/08/08
    4867000005
    [35] Zygorhiza kochii
    Last Modified in 01/08/08
    2491000005
    [36] Janjucetus hunderi
    Last Modified in 01/08/08
    5461000005
    [37] P macrocephalus
    Last Modified in 01/08/08
    10213000005
    [38] M novaeangliae
    Last Modified in 01/08/08
    10213000005
    [39] B physalus
    Last Modified in 01/08/08
    10213000005
    [40] B musculus
    Last Modified in 01/08/08
    10213000005
    [41] B borealis
    Last Modified in 01/08/08
    10213000005
    [42] B edeni brydei
    Last Modified in 01/08/08
    1150000005
    [43] B bonaerensis
    Last Modified in 01/08/08
    10213000005
    [44] B acutorostrata
    Last Modified in 01/08/08
    10411000005
    [45] E robustus
    Last Modified in 01/08/08
    10213000005
    [46] C marginata
    Last Modified in 01/08/08
    10213000005
    [47] B mysticetus
    Last Modified in 01/08/08
    10213000005
    [48] Eubalaena sp
    Last Modified in 01/08/08
    10213000005
    [49] END
    Last Modified in 01/08/08
    1141000005
    [50] BEGIN
    Last Modified in 01/08/08
    10411000005


    Project views

    type number of views Individual items viewed (where applicable)
    Total project views1287
    Project overview189
    Matrix views117Matrix landing page (94 views); Mysticete Supermatirx (23 views);
    Media views269Media search (233 views); M85691 (36 views);
    Specimen list152
    Taxon list449
    Documents list64
    Bibliography47




    Project downloads

    type number of downloads Individual items downloaded (where applicable)
    Total downloads from project29
    Matrix downloads16Mysticete Supermatirx (16 downloads);
    Project downloads7
    Document downloads6Demere et al. Dental (2 downloads); Demere et al. Supermatrix (4 downloads);