Miocaperea, Bisconti, 2012

Bisconti, Michelangelo, 2012, Comparative osteology and phylogenetic relationships of Miocaperea pulchra, the first fossil pygmy right whale genus and species (Cetacea, Mysticeti, Neobalaenidae), Zoological Journal of the Linnean Society 166 (4), pp. 876-911 : 879

MIOCAPEREA GEN. NOV.

Diagnosis. Miocaperea differs from Caperea (which is the only other known genus of Neobalaenidae ) by: a reduced protrusion of the exoccipital that reaches a point only slightly posterior to the occipital condyles; its temporal fossa, with the squamosal fossa mainly vertical, whereas in the living Caperea it is inclined anteroventrally from the lambdoid crest; lambdoid crest triangular, but in Caperea it is rounded; the alisphenoid is excluded from being exposed in the temporal fossa, and the foramen pseudo-ovale is completely included within the squamosal, whereas in Caperea , the alisphenoid is exposed in the temporal fossa and the foramen pseudo-ovale is located in the pterygoid.

Discussion. Several characters allow us to distinguish SMNS 46978 from the living pygmy right whale C. marginata . A comparison of Figures 2 and S 1 shows that the whole posterior portion of the skull of M. pulchra gen. et sp. nov. is different from the corresponding portion of C. marginata . In particular, the extreme posterior projection observed in the latter is totally lacking in the former. The shape of the posterior portion of the temporal fossa, the posterior development of the lambdoid crest, and the orientation of the squamosal fossa result in different arrangements and function of the temporal muscle in the two taxa. Additionally, the shorter posterior protrusion of the exoccipital in M. pulchra gen. et sp. nov. suggests a different development of neck muscles. Finally, the different relationships that the foramen pseudo-ovale has with the surrounding bones suggests different developmental paths of the ventrolateral surface of the skull posteriorly to the supraorbital process of the frontal. All these differences support a clear distinction between C. marginata and specimen SMNS 46978, the principal subject of this article. Such a distinction is better represented by assigning SMNS 46978 to a different genus, namely Miocaperea .

Etymology. Mio from Miocene; Caperea , scientific name for the pygmy right whale.

Figures

Figure 1. Locality of the discovery of Miocaperea pulchra gen. et sp. nov. A, South America; B, Peruvian territory with Aguada de Lomas indicated by a line; C, close-up view of Aguada de Lomas in Peru.

Figure 2. Miocaperea pulchra gen. et sp. nov.: holotype. A, dorsal view; B, ventral view; C, right lateral view; D, left lateral view. In (A) the anterior portion (rostrum) is on the same plane as that on which the neurocranium is lodged, in order to better show the nasal bones. This results in wide gaps between the maxillae and the supraorbital processes of the frontal. Such gaps are absent in (B) because the anterior portion is closer to the neurocranium, to represent the whole skull in articulation.