ndskull2.jpg (49246 bytes)  

A New Plioplatecarpus sp. Mosasaur from North Dakota

Copyright 2000-2009 by Mike Everhart

Created 10/28/1999; Last updated: 09/07/2009


Adapted from a photo by John Campbell, North Dakota Geological Survey.  Used with permission of John Campbell, Copyright 2000 by John Campbell and Mike Everhart


by John Campbell

North Dakota Geological Survey

One of our current projects in the Paleo lab is the preparation, study and mounting of a large Plioplatecarpus mosasaur from the Cretaceous Pierre Shale, Griggs County, North Dakota.

The specimen was found in 1995 by two local fossil collectors, Mike Hanson and Dennis Halvorson. Mike and Dennis had been collecting fossils for a few years and had developed a keen interest in paleontology. This prompted them to contact John Hoganson, the paleontologist for the North Dakota Geological Survey.  Because of earlier dealings with Dr. Hoganson, they knew that they had an important find, when they saw the lower jaws of a mosasaur eroding out of small knoll near the Sheyenne River.

A few days after Mike and Dennis talked with John, we headed out to check out the mosasaur find. Neither John, nor I were expecting anything more than a partial jaw, but to our surprise a little digging had exposed a lot more bones, and a lot more work than we were ready for at the time. It took about 4 weeks, spread over two years to collect the skeleton, but it was worth the effort!

The specimen is around 70% complete, missing only the flippers, pelvis, a few ribs and parts of the tail. It is the largest Plioplatecarpus ever found, 25% bigger, than the next biggest, (based on the quadrate) and a new

The skeleton is 23 feet long, the near complete skull alone is 3 feet long. The specimen will be on display early 2000 at the North Dakota Heritage Center in Bismarck, North Dakota. Thanks to its donation to the state from Orville and Bev Tranby, the owners of the land it was found on. 

Mosasaurs were large marine going lizards related to the modern monitor lizards. Mosasaurs ranged from about 3 meters long,  to upwards of 12 meters. An average Plioplatecarpus would have been about 5 meters long. If you would like to read more about mosasaurs a good place to go is the Oceans of Kansas Web Page.

nddrawa.jpg (2606 bytes) Field sketch of mosasaur remains (ND97-115.1)   Abbreviations:  f = frontal; p = parietal; L.q. = Left quadrate; R.q. = Right quadrate; pm = Premaxilla; L.de. = left dentary; R.de. = Right dentary;  L.m. = Left maxilla; R.m. = Right maxilla; L. j. = Left jugal; R.j. = Right jugal; L.s. = Left squamosal; R.s. = Right squamosasl; L.c. = Left coracoid; R.c. = Right coracoid; L.sc. = Left scapula; R.sc = Right scapula.
ndfrntla.jpg (3185 bytes) A dorsal view of the frontal and parietal of the Plioplatecarpus.   Scale is in cm. (ND97-115.1).  This and the following photos by Johnathan Campbell, NDGS.


ndpremxa.jpg (3356 bytes) A dorsal view of the premaxilla. (ND97-115.1)
ndpremxb.jpg (3659 bytes) The left side of the premaxilla. (ND97-115.1)
ndlquada.jpg (4428 bytes) Lateral and medial views of the left quadrate. (ND97-115.1)
ndoccipa.jpg (2720 bytes) The occipital condyle and part of the basioccipital (ND97-115.1)
ndlmaxa.jpg (3434 bytes) A medial view of the left maxilla (upper jaw) (ND97-115.1)
ndjugala.jpg (2865 bytes) The left jugal (supports a portion of the orbit of the eye) (ND97-115.1)
ndbitea.jpg (2904 bytes) Part of the right jugal showing evidence of scavenging by sharks (ND97-115.1)
ndscapua.jpg (3055 bytes) The scapula (ND97-115.1)
pliopl1a.jpg (3142 bytes) The finished exhibit........ Background painting is by D. W. Miller
pliopl3a.jpg (3863 bytes) ..... with a detail from the above picture.
pliopl2a.jpg (3004 bytes) Another view.

Click here to see two similar specimens of Plioplatecarpus from Mississippi and Alabama.

Credits:  Photos, drawing and text used with permission of John Campbell, North Dakota Geological Survey.  Copyright 2000-2008 by John Campbell, NDGS and Mike Everhart, Oceans of Kansas Paleontology.