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Trinacromerum bentonianum

Cragin 1888

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KUVP 5070 - A polycotylid from the "Fort Benton" of Kansas


Copyright © 2008-2010 by Mike Everhart

Created 03/11/2008 - Last updated 10/28/2010



LEFT:  A Trinacromerum bentonianum plesiosaur swims along the bottom of the seas covering Kansas during Turonian time.   Copyright © Dan Varner; used with permission of  Dan Varner


Order Plesiosauria, de Blainville 1835

Superfamily Plesiosauroidea, Welles 1943

Family Polycotylidae, Cope 1869

Trinacromerum bentonianum Cragin 1888

Trinacromerum bentonianum Cragin 1888 was described from two skulls (USNM 10945 -holotype and USNM 10946 - paratype) found in the (?) Fairport Chalk Member of the Carlile Shale (Middle Turonian) in Osborne County, Kansas.

Carpenter (1996) assigned both Trinacromerum and Dolichorhynchops to the Polycotylidae.

The photos below are of another skull Trinacromerum bentonianum (KUVP-5070) discovered in December, 1936, during the construction of a road-cut along U.S. 81 Highway, south of Concordia (Cloud County), Kansas. According to Riggs (1944, p. 77; see also Lane, 1946) gave the horizon of the specimen as ten feet "below the Jetmore Chalk Member," in the Hartland Shale Member, Greenhorn Limestone. 

vp5070a1.jpg (12117 bytes) LEFT: The skull Trinacromerum bentonianum (KUVP-5070) in right lateral view. This specimen was originally described in 1944 by Elmer Riggs and named Trinacromerum "willistoni" in honor of  S. W. Williston, but the name is considered to be a junior synonym of T. bentonianum (Carpenter, 1996).
vp5070a2.jpg (13058 bytes) LEFT: The skull Trinacromerum bentonianum (KUVP-5070) in left lateral view.  Riggs (1944) noted that the specimen as from ten feet below the Jetmore Chalk Member, in the Hartland Shale Member, Greenhorn Limestone
vp5070a4.jpg (3670 bytes) LEFT: The distal end of the jaws in left lateral view.
vp5070a5.jpg (7923 bytes) LEFT: The center portion of the skull and lower jaws in right lateral view.
vp5070a6.jpg (6433 bytes) LEFT: The articulation of the quadrate bone of the skull with the articular of lower jaw, in right lateral view.


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