page_title: Megacephalosaurus
section_title: Initial identification as Brachauchenius lucasi
hierarchical_section_title: Megacephalosaurus / Discovery and history / Initial identification as Brachauchenius lucasi
caption_attribution_description: Brachauchenius lucasi perusing a generic hesperornithiform bird.
context_page_description: Megacephalosaurus is an extinct genus of short-necked pliosaur that inhabited the Western Interior Seaway of North America about 94 to 93 million years ago during the Turonian stage of the Late Cretaceous, containing the single species M. eulerti. It is named after its large head, which is the largest of any plesiosaur in the continent and measures up to 1.75 meters in length. Megacephalosaurus was one of the largest marine reptiles of its time with an estimated length of 6–9 meters. Its long snout and consistently sized teeth suggest that it preferred a diet on smaller-sized prey.
  Remains representing the pliosaur include two fossil skulls, three ribs, and a neural arch. The fossils have been found in deposits of the Carlile Shale and Greenhorn Limestone in Kansas and elsewhere in the midwestern United States. First discovered in 1950, they were originally thought to have been giant fossils of a closely related pliosaur known as Brachauchenius lucasi. But by 2013, paleontologists understood that such fossils belonged to a distinct animal. Megacephalosaurus was among the last known pliosaurs.
context_section_description: The first specimen of Megacephalosaurus was discovered by two teenage brothers named Frank and Robert Jennrich while collecting fossil shark teeth near Fairport, Kansas. The skull was found bottom-side up and completely crushed into a thin layer. Recognizing the significance of their discovery, the brothers corresponded with paleontologist George F. Sternberg and led him to the fossil during the fall of 1950. Sternberg identified the locality to likely be either the Greenhorn Limestone or Graneros Shale with a nearby fossil including that of a Xiphactinus. The three men, with the help of a local cow-herder named Jim Rouse, excavated the skull by late October of the same year. The land on which the fossil was found was owned by Otto C. Eulert (making the fossil his property), who subsequently donated the specimen to the Sternberg Museum of Natural History. This specimen was cataloged as FHSM VP-321. Sternberg wrote to Eulert on November 2, 1950, that he initially thought the fossil belonged to a large mosasaur. However, he quickly changed his identification to that of a plesiosaur. After conferring with Samuel Paul Welles of UC Berkeley and other paleontologists during the 1950 Society of Vertebrate Paleontology meeting in Albuquerque, New Mexico, Sternberg identified FHSM VP-321 as the Late Cretaceous pliosaur Brachauchenius lucasi. Although additional associated fossils of the specimen were recovered during its excavation, Sternberg had the skull and left lower jaw embedded on a mount of plaster and displayed it in the museum's public exhibits by 1951.
caption: Fossils of Megacephalosaurus were initially misidentified as giant fossils of the closely related Brachauchenius lucasi.
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