''Inermorostrum'' is a genus of primitive

odontocete The toothed whales (also called odontocetes, systematic name Odontoceti) are a parvorder of cetaceans that includes dolphins, porpoises, and all other whales possessing teeth, such as the beaked whales and sperm whales. Seventy-three species of ...

from early Oligocene (

Rupelian The Rupelian is, in the geologic timescale, the older of two ages or the lower of two stages of the Oligocene Epoch/ Series. It spans the time between . It is preceded by the Priabonian Stage (part of the Eocene) and is followed by the Chattian ...

) marine deposits in South Carolina belonging to the family

Xenorophidae Xenorophidae is an extinct family of odontocetes currently known from the Oligocene of the southeastern US. Known genera of xenorophids include ''Albertocetus'', '' Archaeodelphis'', '' Xenorophus'', '' Cotylocara'', ''Echovenator'', and ''Inerm ...

Description and biology

''Inermorostrum'' is largely distinguished from other xenorophiids in having a greatly reduced rostrum devoid of functional teeth. The short, toothless rostrum is unusual for early odontocetes, showing that ''Inermorostrum'' mostly preyed on squids and other marine invertebrates by means of suction-feeding.Robert W. Boessenecker, Danielle Fraser, Morgan Churchill and Jonathan H. Geisler. 2017. A Toothless Dwarf Dolphin (Odontoceti: Xenorophidae) Points to Explosive Feeding Diversification of Modern Whales (Neoceti). Proceedings of the Royal Society B. DOI: 10.1098/rspb.2017.0531 Inermorostrum anterolateral

References

Oligocene mammals of North America Oligocene cetaceans Fossil taxa described in 2017 {{paleo-whale-stub