P. quarantellii (type)Bisconti, 2010 Plesiobalaenoptera is a genus of extinct rorqual which existed in Italy during the late Miocene epoch.

Fossils have been found from sediments of the Stirone River in Northern Italy (44°48′N 10°00′E / 44.8°N 10.0°E / 44.8; 10.0, paleocoordinates 43°54′N 10°30′E / 43.9°N 10.5°E / 43.9; 10.5)[2] that were deposited during the Tortonian age, around 11 to 7 million years ago.

During ram feeding, modern whales swim toward their prey with open mouths and engulf them in an expandable throat.

Plesiobalaenoptera has a postcoronoid fossa, or hole in the dentary bone of the lower jaw, which would have made this method of feeding difficult to perform.

The two form a clade that is the sister taxon of crown balaenopterids, which includes the last common ancestor of the living Balaenoptera and Megaptera, and all of its descendants.