Friday Fossil Feature – Cotylocara macei

By Robert Boessenecker(@CoastalPaleo) and Sarah Boessenecker(@tetrameryx)

Happy Fossil Friday!

Our featured fossil this week is Cotylocara macei, an extinct dolphin from South Carolina.

Cotylocara as on display in the Evolution of Whales exhibit at the CCNHM.

Cotylocara as on display in the Evolution of Whales exhibit at the CCNHM. Photo by S. Boessenecker

Cotylocara macei was named in 2014 by Jonathan Geisler, Matt Colbert, and College of Charleston Professor Emeritus Jim Carew in the journal Nature. Cotylocara macei is our first type specimen here at CCNHM – in other words, the specimen that a new species is based upon. It is a member of the family Xenorophidae, an extinct family representing an early radiation of some of the most primitive known toothed whales (Odontoceti).

Xenorophids are relatively strange and have narrow snouts, gaps between their teeth, and unique skull anatomy in the facial region. The blowhole of Cotylocara was not as far posterior as it is in modern dolphins, and it lacks many sinuses present in modern dolphins – but it does have many features indicative of the capability for sound production used for echolocation as in modern dolphins, such as asymmetry of the skull, asymmetry of holes for blood vessels (foramina) in the face, and large basins on the base of the snout and behind the blowhole.

It’s easy to see the strange warping of the skull when viewed from head-on; these features show that Cotylocara was capable of echolocation. Photo by S. Boessenecker

These are all likely related to well-developed soft tissues like facial muscles and the fatty melon that are implicated in echolocation in modern dolphins. At ~30 million years old, Cotylocara is the best evidence yet that the earliest odontocetes were capable of echolocation, quickly distinguishing themselves from filter-feeding baleen whales.

The strange skull shape of odontocetes allows for the soft tissues that aid in echolocation. Photo from WikimediaCommons

Stop by during museum hours and say hello to Cotylocara macei yourself!

 

 

Further Reading:

A supermatrix analysis of genomic, morphological, and paleontological data from crown Cetacea

BMC Evolutionary Biology, 2011, Volume 11, Number 1, Page 1

Jonathan H Geisler, Michael R McGowen, Guang Yang, John Gatesy [Full Article]

 

A new Xenorophus-like odontocete cetacean from the oligocene of North Carolina and a discussion of the basal odontocete radiation.

Journal of Systematic Palaeontology, 6, pp 433-452. doi:10.1017/S1477201908002472.

Mark D. Uhen (2008). [Full Article]

 

A new basal odontocete from the upper Rupelian of South Carolina, U.S.A., with contributions to the systematics of Xenorophus and Microcetus (Mammalia, Cetacea)

Albert E. Sanders , Jonathan H. Geisler

Journal of Vertebrate Paleontology

Vol. 35, Iss. 1, 2015 [Full Article]

 

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