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

Gol'din P, Steeman ME - PLoS ONE (2015)

Bottom Line: It was found to represent not only a new genus, Tranatocetus gen. nov., but also a new family; Tranatocetidae.Inclusion of problematic taxa like Tranatocetus argillarius 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Natural History and Palaeontology, The Museum of Southern Jutland, Lergravsvej 2, 6510, Gram, Denmark.

ABSTRACT
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, "Mesocetus" argillarius, 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, Tranatocetus 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 Tranatocetus argillarius 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.

No MeSH data available.


Related in: MedlinePlus

The skull of Tranatocetus argillarius, MGUH VP 2319.A, B, lateral view; C, D, anterior view; E, F, posterior view.
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pone.0135500.g002: The skull of Tranatocetus argillarius, MGUH VP 2319.A, B, lateral view; C, D, anterior view; E, F, posterior view.

Mentions: Of the skull, a distinctly short, wide and high neurocranium with posterior portions of the rostral bones has been preserved (Figs 1 and 2; Table 1). In lateral view, the vertex forms an angle close to 90° between the facial bones and the occipital shield. The temporal crest is high, so that the vertex is highly elevated above the rhomboid temporal fossa. Viewed anteriorly, the skull is slightly asymmetrical as the vertex is shifted left, and the occiput is smaller to the left relative to the right: this seems to be the natural condition. The posterior portion of the premaxilla is not distinct and may be fused with the maxilla (Fig 3). The ascending process of the maxilla is posteriorly constricted. The ascending rostral processes completely override the frontals on the vertex and overlap the parietals. The anterior edge of the maxilla is strongly concave at the base of the ascending process leaving a crescent-shaped portion of the supraoccipital process of the frontal anterior to a well-defined transverse orbitotemporal crest. This may mark the insertion of the occipitofrontalis muscle [19]. The straight, long, narrow and high nasals are wedged between the ascending processes of the maxillae, dividing these on the vertex to their posteriormost extension. The supraorbital process of the frontal gradually slopes ventrally. The lateral portion of the parietal is concave. The parietals contact in a short and low sagittal crest on the vertex. The occipital shield is sub-triangular, with high, sigmoid nuchal crests. A low horizontal crest over the dorsal condyloid fossa divides the occipital shield into a nearly vertical posteroventral portion that meets a more horizontal anterodorsal portion at a blunt angle (Fig 4). The long and robust paroccipital process extends posterior to the condyle and postglenoid process.


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

Gol'din P, Steeman ME - PLoS ONE (2015)

The skull of Tranatocetus argillarius, MGUH VP 2319.A, B, lateral view; C, D, anterior view; E, F, posterior view.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4558012&req=5

pone.0135500.g002: The skull of Tranatocetus argillarius, MGUH VP 2319.A, B, lateral view; C, D, anterior view; E, F, posterior view.
Mentions: Of the skull, a distinctly short, wide and high neurocranium with posterior portions of the rostral bones has been preserved (Figs 1 and 2; Table 1). In lateral view, the vertex forms an angle close to 90° between the facial bones and the occipital shield. The temporal crest is high, so that the vertex is highly elevated above the rhomboid temporal fossa. Viewed anteriorly, the skull is slightly asymmetrical as the vertex is shifted left, and the occiput is smaller to the left relative to the right: this seems to be the natural condition. The posterior portion of the premaxilla is not distinct and may be fused with the maxilla (Fig 3). The ascending process of the maxilla is posteriorly constricted. The ascending rostral processes completely override the frontals on the vertex and overlap the parietals. The anterior edge of the maxilla is strongly concave at the base of the ascending process leaving a crescent-shaped portion of the supraoccipital process of the frontal anterior to a well-defined transverse orbitotemporal crest. This may mark the insertion of the occipitofrontalis muscle [19]. The straight, long, narrow and high nasals are wedged between the ascending processes of the maxillae, dividing these on the vertex to their posteriormost extension. The supraorbital process of the frontal gradually slopes ventrally. The lateral portion of the parietal is concave. The parietals contact in a short and low sagittal crest on the vertex. The occipital shield is sub-triangular, with high, sigmoid nuchal crests. A low horizontal crest over the dorsal condyloid fossa divides the occipital shield into a nearly vertical posteroventral portion that meets a more horizontal anterodorsal portion at a blunt angle (Fig 4). The long and robust paroccipital process extends posterior to the condyle and postglenoid process.

Bottom Line: It was found to represent not only a new genus, Tranatocetus gen. nov., but also a new family; Tranatocetidae.Inclusion of problematic taxa like Tranatocetus argillarius 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Natural History and Palaeontology, The Museum of Southern Jutland, Lergravsvej 2, 6510, Gram, Denmark.

ABSTRACT
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, "Mesocetus" argillarius, 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, Tranatocetus 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 Tranatocetus argillarius 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.

No MeSH data available.


Related in: MedlinePlus