A toothless dwarf dolphin (Odontoceti: Xenorophidae) points to explosive feeding diversification of modern whales (Neoceti). Issue 1861 (23rd August 2017)

• Record Type: Journal Article
• Authors: Boessenecker, Robert W.; Fraser, Danielle; Churchill, Morgan; Geisler, Jonathan H.
• Is Part Of: Proceedings. Volume 284:Issue 1861(2017)
• Publication Date: 2017-08-23
• Subjects: Xenorophidae -- Odontoceti -- Neoceti -- suction feeding -- Oligocene; Biology -- Periodicals; 570.5
• DOI: 10.1098/rspb.2017.0531
• Languages: English
• ISSNs: 0962-8452

Abstract

Abstract : Toothed whales (Odontoceti) are adapted for catching prey underwater and possess some of the most derived feeding specializations of all mammals, including the loss of milk teeth (monophyodonty), high tooth count (polydonty), and the loss of discrete tooth classes (homodonty). Many extant odontocetes possess some combination of short, broad rostra, reduced tooth counts, fleshy lips, and enlarged hyoid bones—all adaptations for suction feeding upon fishes and squid. We report a new fossil odontocete from the Oligocene (approx. 30 Ma) of South Carolina ( Inermorostrum xenops, gen. et sp. nov.) that possesses adaptations for suction feeding: toothlessness and a shortened rostrum (brevirostry). Enlarged foramina on the rostrum suggest the presence of enlarged lips or perhaps vibrissae. Phylogenetic analysis firmly places Inermorostrum within the Xenorophidae, an early diverging odontocete clade typified by long-snouted, heterodont dolphins. Inermorostrum is the earliest obligate suction feeder within the Odontoceti, a feeding mode that independently evolved several times within the clade. Analysis of macroevolutionary trends in rostral shape indicate stabilizing selection around an optimum rostral shape over the course of odontocete evolution, and a post-Eocene explosion in feeding morphology, heralding the diversity of feeding behaviour among modern Odontoceti.