Dolichorhynchops
Dolichorhynchops is an extinct genus of polycotylid plesiosaur from the Late Cretaceous (early Turonian to late Campanian stage) of North America, containing three species, D. osborni, D. bonneri and D. tropicensis,[1] as well as a questionably referred fourth species, D. herschelensis.[2] Dolichorhynchops was a prehistoric marine reptile, but at least one species, D. tropicensis, likely entered rivers to collect gastroliths. Its Greek generic name means "long-nosed face". While typically measuring about 3 metres (9.8 ft) in length, the largest specimens of D. osborni and D. bonneri are estimated to have a total body length more than approximately 4.29 metres (14.1 ft) and 5.09 metres (16.7 ft), respectively.
The holotype specimen of Dolichorhynchops osborni, KUVP 1300, was discovered in the upper Smoky Hill Chalk Logan County, Kansas, by George F. Sternberg, as a teenager, in around 1900. The remains were collected by him and his father, Charles H. Sternberg, and then sold to the University of Kansas (Lawrence, Kansas). KUVP 1300[3] was prepared and mounted by H.T. Martin under the supervision of Dr. Samuel Wendell Williston, who described and named it in 1902. A more detailed description and photographs were provided by Williston 1903). The specimen has been on display in the KU Museum of Natural History since that time. Everhart 2004bestimated that the holotype had a skull measuring 57 cm (1.87 ft) long.
In 1918, Charles H. Sternberg found a large mosasaur, Tylosaurus, with the remains of a plesiosaur in its stomach.[4] The mosasaur specimen is currently mounted in the United States National Museum (Smithsonian) and the plesiosaur remains are stored in the collections. Although these important specimens were briefly reported by Sternberg 1922, the information was lost to science until 2001. This specimen was rediscovered and described by Everhart 2004a. It is the basis for the story line in the 2007 National Geographic IMAX documentary Sea Monsters: A Prehistoric Adventure, and a book by the same name Everhart 2007.
George Sternberg found a second, less complete specimen of D.osborni in 1926. In his effort to sell the specimen to a museum, Sternberg took detailed photographs of the skull.[5] The specimen was eventually mounted in plaster and was acquired by the Harvard Museum of Comparative Zoology. MCZ 1064[6] was on display there until some time in the 1950s. This specimen was never completely described although the skull was figured by O'Keefe 2004. (See also Everhart 2004b)
The specimen of D. osborni on exhibit at the Sternberg, FHSM VP-404[7] was found by Marion Bonner near Russell Springs in Logan County in the early 1950s. Carpenter 1996 estimated that FHSM VP-404, with a skull measuring 51.3 centimetres (1.68 ft) long, had a total body length of approximately 3.07 metres (10.1 ft). The skull[8] was crushed flat but is in very good condition. This specimen was initially reported by Sternberg & Walker 1957, and then was the subject of a Masters thesis by Bonner 1964. Note that it was described by Bonner as "Trinacromerum osborni" which was the accepted genus name at the time.
Larger specimens of D. osborni have been reported: UNSM 50133 had an estimated skull length of 61.8 centimetres (2.03 ft), while AMNH 5834 had an estimated skull length of 74.5 centimetres (2.44 ft) (see Carpenter 1996). Carpenter 1996 estimated that AMNH 5834 had a total body length of more than approximately 4.29 metres (14.1 ft).
