<i>Brandtocetus</i>, a new genus of baleen whales (Cetacea, Cetotheriidae) from the late Miocene of Crimea, Ukraine

<div><p>ABSTRACT</p><p>A new cetotheriid baleen whale, <i>Brandtocetus chongulek</i>, gen. et sp. nov., is described from the late Miocene of Crimea, Ukraine. The type series is represented by three partial skulls with periotic bones and tympanic bullae, one of the three belonging to a juvenile. <i>Brandtocetus chongulek</i> has transversely expanded squamosals, ‘S’-shaped nuchal crests, an anterior margin of the occipital shield extending anterior to the center of the temporal fossa, and an elongated posterior process of the tympanoperiotic. The tympanoperiotic and postglenoid process of the squamosal are typical of cetotheriines (as opposed to herpetocetines). Comparison of the juvenile specimen with adults shows no differences in tympanoperiotic anatomy, moderate squamosal growth, and significant growth of the neurocranium after the age of at least 1 year. The phylogenetic analysis including 13 cetotheriids supports the monophyly of Cetotheriidae sensu stricto and suggests the monophyly of whales from the Eastern Paratethys (<i>Brandtocetus</i>, <i>Cetotherium</i>, <i>Kurdalagonus</i>, and possibly <i>Eucetotherium</i>). <i>Brandtocetus</i> and other cetotheriids from the Black Sea region possess cranial features hypothesized to be adaptations to a generalized filter feeding strategy combining different modes of suction feeding.</p> <p>SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at <a href="http://www.tandfonline.com/UJVP" target="_blank">www.tandfonline.com/UJVP</a></p> </div

The shape of the tympanic bulla (ventrolateral view) in the phylogeny of baleen whale families.

<p>Balaenidae: <i>Eubalaena glacialis</i>, CU CN 1x. <i>Diorocetus</i>: <i>Diorocetus hiatus</i>, USNM 23494. <i>Aglaocetus</i>: <i>Aglaocetus patulus</i>, USNM 23690. Eschrichtiidae: <i>Eschrichtius robustus</i>, ZMMU 171918. <i>Pelocetus</i>: <i>Pelocetus calvertensis</i>, USNM 11976. Balaenopteridae: <i>Balaenoptera acutorostrata</i>, ZMMU 171919. Tranatocetidae: <i>“Plesiocetopsis hupschii”</i>, RBINS 664 / Reg. 1240. <i>Uranocetus</i>: <i>Uranocetus gramensis</i>, MSM P813. <i>Parietobalaena</i>: <i>Parietobalaena palmeri</i>, USNM 16119. Neobalaenidae: <i>Caperea marginata</i>, NMV C28531; printed under a CC BY license, with permission from Felix Marx, original copyright 2012. Cetotheriidae: <i>Brandtocetus chongulek</i>, TNU Skull 4.</p

The phylogenetic tree of <i>Tranatocetus argillarius</i> and related taxa of baleen whales.

<p>The tree is the consensus of 12 most parsimonious trees (501 step, CI = 0.33, RI = 0.66). The age values are provisionally indicated as the earliest estimates and are based on the review by Fordyce and Marx [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0135500#pone.0135500.ref008" target="_blank">8</a>], as well as on original descriptions.</p

Mandible of <i>Tranatocetus argillarius</i>.

<p>MGUH VP 2319: A, dorsal view. B, lateral view. C, medial view. D, posterior view. MGUH VP 2320: F, the cross-section of the anterior portion.</p

Postcranial skeletal elements of <i>Tranatocetus argillarius</i>.

<p>A–D, MGUH VP 2319: A, hyoid. B, axis. C, humerus. D, scapula. E, MGUH VP 2320, scapula in lateral view.</p

The skull of <i>Tranatocetus argillarius</i>, MGUH VP 2319.

<p>A, B, dorsal views; C, D, ventral views.</p

From Problem Taxa to Problem Solver: A New Miocene Family, Tranatocetidae, Brings Perspective on Baleen Whale Evolution

<div><p>Miocene baleen whales were highly diverse and included tens of genera. However, their taxonomy and phylogeny, as well as relationships with living whales, are still a subject of controversy. Here, <i>“Mesocetus” argillarius</i>, a poorly known specimen from Denmark, is redescribed with a focus on the cranial anatomy. It was found to represent not only a new genus, <i>Tranatocetus</i> gen. nov., but also a new family; Tranatocetidae. The whales of this family have the rostral bones either overriding or dividing the frontals; the rostral bones are contacting the parietals and nasals dividing the maxillae on the vertex; the occipital shield is dorsoventrally bent. The tympanic bulla is particularly characteristic of this family featuring a short, narrow anterior portion with a rounded or squared anterior end and a wider and higher posterior portion that is swollen in the posteroventral area. A phylogenetic analysis including 51 taxa supports a monophyletic group comprising most Neogene and modern whales, with Tranatocetidae being possibly closer related to Balaenopteridae (rorquals) than to Cetotheriidae. Tranatocetidae exhibit a charahteristic bulla shape. In fact, all Neogene and modern mysticete families examined have a unique shape of the tympanic bulla that is diagnostic at family-level. Inclusion of problematic taxa like <i>Tranatocetus argillarius</i> in phylogenies brings new understanding of the distribution and diagnostic value of character traits. This underlines the need for re-examination of earlier described specimens in the light of the wealth of new information published in later years.</p></div

Diagnostic features of Tranatocetidae: squamosal area in lateral view.

<p>A, <i>Tranatocetus argillarius</i> MGUH VP 2319 (Tranatocetidae). B, <i>Nannocetus eremus</i> UCMP 26502 (Cetotheriidae) (inverted). C, <i>Cetotherium riabinini</i> NMNH-P 668/1 (Cetotheriidae). D, <i>Eschrichtius robustus</i> MVZ 125560 (Eschrichtiidae) (inverted). The images are cropped; the posterior process of the tympanoperiotic is delimited with a white contour.</p

Cranial measurements (mm) of <i>Tranatocetus argillarius</i> MGUH VP 2319.

<p>Cranial measurements (mm) of <i>Tranatocetus argillarius</i> MGUH VP 2319.</p

Right periotic bone of <i>Tranatocetus argillarius</i>, MGUH VP 2319.

<p>A, ventral view. B, posterior view (cropped image).</p