Family Balaenopteridae - Rorquals (6 species in 2 genera)
This family contains the largest animals ever to live; all balaenopterids have adult body lengths of over 7 m, and some are much larger. The rorquals are streamlined animals (the humpback whale somewhat less so than the others), with a series of long pleats extending from the snout tip to as far back as the navel on the ventral surface. Balaenopterids are fast and active lunge feeders; their morphology allows them to open their jaws very widely and distend their throats to take in huge mouthfuls of water during feeding. The baleen plates are of moderate length and fringe fineness. Density and fringe diameter vary among species, and along with plate number and width to length ratio, are diagnostic characters. Rorquals have dorsal fins (varying in size and shape) set behind the midpoint of the back. The upper jaw has a relatively flat profile, a feature reflecting the structure of the skull. Within a given feature, differences among balaenopterids are often subtle variations on a theme, rather than class distinctions. Therefore, information on many features may be needed to distinguish among them and reliance on a single character for identification is discouraged.
Genera
Genus Balaenoptera containing 5 species:
Balaenoptera acutorostrata (Minke whale)
Balaenoptera borealis (Sei whale)
Balaenoptera edeni (Bryde's whale)
Balaenoptera musculus (Blue whale)
Balaenoptera physalus (Fin whale)
Genus Megaptera containing 1 species:
Megaptera novaeangliae (Humpback whale)