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
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
Currently Viewing:
MorphoBank Project 182


Members

member name taxa specimens media media
notes
chars character
notes  media
labels
cell scorings
(scored, NPA, "-")
cell
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)
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John Gatesy
Full membership
Last logged in Never
000000000
(0, 0, 0)
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Michael McGowen
Full membership
Last logged in 01/07/08
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(0, 0, 0)
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Natalie Milbrodt
Full membership
Last logged in 03/16/12
000000000
(0, 0, 0)
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Taxonomic Overview for Matrix 'M481' (50 Taxa)

taxon unscored
cells
scored
cells
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cell images
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access
[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 views261
Project overview62
Matrix views56Matrix landing page (40 views); Mysticete Supermatirx (16 views);
Media views54Media search (49 views); M85691 (5 views);
Specimen list33
Taxon list39
Documents list13
Bibliography4




Project downloads

type number of downloads Individual items downloaded (where applicable)
Total downloads from project28
Matrix downloads16Mysticete Supermatirx (16 downloads);
Project downloads6
Document downloads6Demere et al. Dental (2 downloads); Demere et al. Supermatrix (4 downloads);