Temporal range: Middle Eocene
Gingerich, Arif & Clyde 1995
Gaviacetus (from Latin Gavia, "loon" and cetus, "whale") extinct archaeocete whale that lived approximately . Gaviacetus was named for its characteristic narrow rostrum and the fast pursuit predation suggested by its unfused sacral vertebrae.
The G. razai specimen was found in Punjab, Pakistan ( , paleocoordinates ) and those of G. sahnii in Kutch, India ( , paleocoordinates ). The skulls are similar in size in both species, but the teeth of B. sahnii are 150–200% larger.
Although often represented as having small hind limbs, this is an inference from the general progression of other fossil species towards limb loss; the only postcranial remains found for Gaviacetus are a rib and several vertebrae. At least three popular science books misspell this genus as Gaviocetus.
The well-preserved auditory bulla in Gingerich, Arif & Clyde 1995's specimen is dense like in other archaeocetes, is equipped with a prominent sigmoid process, but has 3-5 contacts with the rest of the cranium.
Preserved alveoli (tooth sockets) show that Gaviacetus had double- and tripple-rooted cheek teeth, but some controversy remains regarding the number of molars. Based on other cranial characters, Gingerich, Arif & Clyde 1995 concluded that Gaviacetus is a protocetid (more primitive archeocetes with a third upper molar) and therefore assumed the presence of M3 though no traces thereof are preserved in their specimen. In opposition to this, Bajpai & Thewissen 1998, who's specimen is also lacking the essential maxillar part, thought the cranium above the very small M2 to be to narrow for the presence of M3, hence indicating Gaviacetus is a basilosaurid (a more derived archaeocetes lacking a third upper molar). Uhen 2009 argued against this assignment until more solid evidences have been found.
The preserved sacral vertebra was not fused with its posterior neighbour, indicating that Gaviacetus was a tail-powered swimmer like Protocetus, better adapted to pursuit predation than Rodhocetus. The preserved transverse process of the sacral vertebra is distally expanded, suggesting a synchondrosal joint between the vertebral column and pelvis.
- Gaviacetus razai in the Paleobiology Database. Retrieved April 2013.
- Gaviacetus sahnii in the Paleobiology Database. Retrieved April 2013.
- Gingerich, Arif & Clyde 1995, p. 305
- Basti Ahmed (Eocene of Pakistan) in the Paleobiology Database. Retrieved April 2013.
- Harudi (Eocene of India) in the Paleobiology Database. Retrieved April 2013.
- Bajpai & Thewissen 1998, p. 229
- Carl Zimmer (1998). At the Water's Edge. This appears to be the first book to have done so.
- Carl Zimmer (1998). At the Water's Edge
- Donald Prothero (2007). Evolution: What the Fossils Say and Why it Matters
- Richard Dawkins (2009). The Greatest Show on Earth
- Gingerich, Arif & Clyde 1995, p. 309, Fig. 11
- Gingerich, Arif & Clyde 1995, p. 307
- Gingerich, Arif & Clyde 1995, p. 306
- Uhen 2009, p. 93
- Bajpai, S.; Thewissen, J. G. M. (1998). "Middle Eocene Cetaceans from the Harudi and Subathu Formations of India". In Thewissen, J. G. M. The Emergence of Whales. Advances in vertebrate paleobiology. New York: Plenum Press. pp. 213–233. ISBN 9780306458538. OCLC 300450327. Retrieved March 2013.
- Gingerich, Philip D.; Arif, Muhammad; Clyde, William C. (1995). "New Archaeocetes (Mammalia, Cetacea) from the middle Eocene Domanda Formation of the Sulaiman Range, Punjab (Pakistan)". Contributions from Museum of Paleontology, The University of Michigan 29 (11): 291–330. OCLC 34123868. Retrieved February 2013.
- Uhen, Mark D. (2009). "Basilosaurids". In Perrin, William F.; Wursig, Bernd; Thewissen, J.G.M. Encyclopedia of Marine Mammals (2nd ed.). Academic Press. ISBN 9780080919935. Retrieved April 2013.