Project 2554: C. de Muizon, G.Bianucci, M. Martínez-Cáceres, O. Lambert. 2019. Mystacodon selenensis, the earliest known toothed mysticete (Cetacea, Mammalia) from the late Eocene of Peru: anatomy, phylogeny, and feeding adaptations. Geodiversitas. 41 (11):401-499.
Specimen: † Mystacodon selenensis (unvouchered)
View: Right lateral view

Abstract

Mystacodon selenensis Lambert, Martínez-Cáceres, Bianucci, Di Celma, Salas-Gismondi, Steurbaut, Urbina & Muizon, 2017 is a toothed mysticete that represents the earliest member of the suborder in the current state of knowledge. Its holotype is a relatively complete skeleton from the upper Eocene (early Priabonian, c. 36.4 Ma) Yumaque Member of the Paracas Formation from the southern coast of Peru. The thorough description of this specimen is presented here and reveals numerous similarities with the contemporaneous basilosaurids including the retention of an innominate that originally articulated to the unpreserved hind limb. However, several characters of M. selenensis clearly relate this taxon to the mysticetes, such as the large palate with a dorsoventrally flattened rostrum, the posterior extension of the palate with an infraorbital plate of the maxilla, the shortening of the premaxillary part of the rostrum, the zygomatic process of the squamosal being closely apposed to the postorbital process of the frontal, and the humeral head being oriented more proximally than posteriorly. A parsimony analysis retrieves Mystacodon as the earliest diverging branch of the Mysticeti with no close phylogenetic relationship with Llanocetus the second oldest known mysticete (c. 34.2 Ma). The dental formula of M. selenensis is that of basilosaurids (I 3/3, C 1/1, P 4/4, M 2/3). The anterior teeth (incisors and canine) are distinctly proportionally smaller than in basilosaurids, whereas the cheek teeth are very close in relative length, but are relatively larger than in most other toothed mysticetes (except Coronodon). The large cheek teeth of Mystacodon suggest a raptorial feeding strategy, probably assisted with some degree of suction, as indicated by the large size of the palate. The anterior teeth of the holotype display a subhorizontal apical wear facet and the cheek teeth a moderately sloping wear surface, differing from the subvertical attrition facets of basilosaurids. This pattern suggests an efficient dental abrasion resulting from feeding upon abrasive food items or/and from the ingestion of sediment during prey capture, which could indicate some degree of bottom feeding. On the forelimb, the size and orientation of the acromion, the great length of the deltopectoral crest, the massiveness of the olecranon of the ulna, and the strong radial anterior process indicate powerful shoulder movements, which suggest an active use of the forelimb when foraging for food on the sea floor. The robustness of digits and the pachyosteosclerosis of ribs with pestle-like distal end corroborate such a scenario. Mystacodon selenensis represents a first step in the evolutionary history of feeding adaptations of early mysticetes; the latter are likely to have experimented an abundant set of feeding strategies and were probably very eclectic in prey choice and capture before hyperspecialized filter feeding became widespread in the suborder.


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Article DOI: 10.5252/geodiversitas2019v41a11

Project DOI: 10.7934/P2554, http://dx.doi.org/10.7934/P2554
This project containsMatrices
  • 1 Media
  • 1 Matrix
  • 46 Taxa
  • 2 Specimens
  • 282 Characters
Total size of project's media files: 39 MB

Download Project SDD File
Total scored cells: 9035
Total media associated with cells: 0
Total labels associated with cell media: 0
Characters
Total characters: 282
Total characters with associated media: 0
Total characters with media with labels: 0
Total character states: 680
Total character states with associated media: 0
Total character states with media with labels:0
Total unordered/ordered characters:257/25
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MorphoBank Project 2554
  • Creation Date:
    08 November 2016
  • Publication Date:
    31 May 2019
  • Project views: 716


    Members

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    Christian Muizon
    Project Administrator
    Last logged in 05/31/19
    46112820178009035
    (8534, 0, 501)
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    Taxonomic Overview for Matrix 'M25739' (43 Taxa)

    taxon unscored
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    [1] † Zygorhiza kochii
    Last Modified in 08/16/19
    1925625607001
    [2] † Cynthiacetus peruvianus
    Last Modified in 11/29/18
    1925925805001
    [3] † Archaeodelphis patrius
    Last Modified in 11/29/18
    16011711705001
    [4] † Simocetus rayii
    Last Modified in 11/29/18
    9718018005001
    [5] † Waipatia maerewhenua
    Last Modified in 11/29/18
    42230230010001
    [6] Squalodon spp
    Last Modified in 11/29/18
    38233232012001
    [7] Tursiops truncatus
    Last Modified in 11/29/18
    3257257022001
    [8] Physeter macrocephalus
    Last Modified in 11/29/18
    8236233041001
    [9] † Mystacodon selenensis
    Last Modified in 11/29/18
    13314614603001
    [10] † Llanocetus denticrenatus
    Last Modified in 11/29/18
    9718118104001
    [11] † Coronodon havensteini
    Last Modified in 11/29/18
    6121621605001
    [12] † Janjucetus hunderi
    Last Modified in 11/29/18
    9118618605001
    [13] † Mammalodon colliveri
    Last Modified in 11/29/18
    9618018006001
    [14] † Fucaia goedertorum
    Last Modified in 08/16/19
    7920120003001
    [15] † Aetiocetus cotylalveus
    Last Modified in 11/29/18
    11117017001001
    [16] † Aetiocetus polydentatus
    Last Modified in 11/29/18
    9718318302001
    [17] † Aetiocetus weltoni
    Last Modified in 11/29/18
    8419619602001
    [18] † ChM pv4745
    Last Modified in 08/16/19
    14213713703001
    [19] † ChM pv5720
    Last Modified in 08/16/19
    10417317305001
    [20] † Micromysticetus rothauseni
    Last Modified in 11/29/18
    189909003001
    [21] † Yamatocetus canaliculatus
    Last Modified in 11/29/18
    71199199012001
    [22] † Eomysticetus whitmorei
    Last Modified in 11/29/18
    82187187013001
    [23] † Morenocetus parvus
    Last Modified in 11/29/18
    16311411405001
    [24] Balaena mysticetus
    Last Modified in 11/29/18
    6256254022001
    [25] Eubalaena spp.
    Last Modified in 11/29/18
    2264258022001
    [26] Caperea marginata
    Last Modified in 11/29/18
    5259253024001
    [27] † Miocaperea pulchra
    Last Modified in 11/29/18
    120144143019001
    [28] † Cetotherium rathkii
    Last Modified in 11/29/18
    120145145017001
    [29] † Cetotherium riabinini
    Last Modified in 11/29/18
    73194194015001
    [30] † Piscobalaena nana
    Last Modified in 11/29/18
    17248246019001
    [31] † Herpetocetus morrowi
    Last Modified in 11/29/18
    46220219017001
    [32] † Herpetocetus transatlanticus
    Last Modified in 11/29/18
    15611711709001
    [33] † Herpetocetus bramblei
    Last Modified in 11/29/18
    119145145018001
    [34] † Diorocetus hiatus
    Last Modified in 11/29/18
    52218218012001
    [35] † Aglaocetus patulus
    Last Modified in 11/29/18
    80191189013001
    [36] † Aglaocetus moreni
    Last Modified in 11/29/18
    124146146012001
    [37] † Parietobalaena campiniana
    Last Modified in 11/29/18
    113156156013001
    [38] † Parietobalaena palmeri
    Last Modified in 11/29/18
    53222217012001
    [39] † Pelocetus calvertensis
    Last Modified in 11/29/18
    45224224013001
    [40] Eschrichtius robustus
    Last Modified in 11/29/18
    4266261017001
    [41] Megaptera novaeangliae
    Last Modified in 11/29/18
    4265263015001
    [42] Balaenoptera acutorostrata
    Last Modified in 11/29/18
    3263262017001
    [43] Balaenoptera physalus
    Last Modified in 11/29/18
    4264262016001


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    Project overview126
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    Taxon list263
    Media views125Media search (109 views); M462201 (16 views);
    Bibliography20
    Specimen list73
    Views for media list38




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