Archaebalaenoptera Bisconti 2007

Archaebalaenoptera Bisconti, 2007

Emended diagnosis of genus. Supraoccipital with rounded anterior border and strong transverse constriction; posterior apex of nuchal crest triangular in dorsal view and directed posteriorly; supraoccipital horizontally bent approximately at mid-length; zygomatic process of squamosal projecting anterolaterally and with sharply defined supramastoid crest; interorbital region of the frontal with transversely rounded sides; posterolateral corner of exoccipital protruding posteriorly.

Discussion. Archaebalaenoptera differs from other balaenopterids in having a unique mix of morphological characters. In particular, while the transverse constriction of the supraoccipital is observed also in ‘Balaenoptera’ cortesii var. portisi, in Archaebalaenoptera the constriction is associated with a rounded anterior border of the supraoccipital; in ‘B.’ cortesii var. portisi the anterior border of the supraoccipital is narrow-to-pointed. The extended posteriorly protruding posterolateral corner of the exoccipital is also observed in Fragilicetus velponi but in that taxon, the supraoccipital is largely different being more squared at its anterior border and the being transverse constriction very reduced. In cross section, the round sides of the interorbital region of the frontal are typical of this genus and represent a marked difference with other balaenopterid genera where the sides of the interorbital region of the frontal are squared or concave.

Type species. Archaebalaenoptera castriarquati Bisconti, 2007