An Extinct Sea Lizard from Western Kansas

By Charles W. Gilmore

THE chalk deposits of western Kansas have long been famous on account of the great number and the fine state of preservation of the fossil remains found in them. For more than fifty years collectors of fossils have searched the chalk exposures for their hidden treasures. Remains of fish, large and small, turtles, toothed birds, lizards, both swimming and flying, and an occasional dinosaurian reptile have been the rewards of these indefatigable hunters.

    The United States National Museum numbers among its rarest treasures fossil remains of all of these several kinds of animals, but quite recently there has been added to the exhibition series the very fine specimen of a swimming or sea lizard shown in the accompanying illustration. This animal goes under the name of Tylosaurus proriger, and belongs to a group of extinct reptiles commonly called Mosasaurs. The Mosasaurs were water living reptiles, with long slender bodies having the limbs modified into short swimming paddles, and a long powerful compressed tail with which they propelled themselves through the water. This specimen, after many weeks of the most painstaking care and skilful work, was cleaned from the investing chalk, the broken parts repaired and the missing bones restored, until finally the skeleton was articulated in the pose shown. It forms a wall panel, the skeleton being in half relief, the dark bone of the specimen standing out in bold contrast against the light yellowish color of the background, which has been made in imitation of the yellow chalk in which the specimen was originally found. The pose adopted for the skeleton was largely determined by the curved articulated sections of the backbone as found in the ground.

    This specimen was collected for the National Museum by the veteran collector of fossils, Mr. Charles H. Sternberg, on Butte Creek, Logan County, Kansas, in 1917. Mr. Sternberg and his three sons, all of whom have been raised as fossil hunters, have collected hundreds of these ancient monsters and the results of their discoveries are to be found in all of the principal museums of the world, the present specimen being still another contribution to the science to which they have given so much.

    The Tylosaurus specimen, as now exhibited, measures about twenty-five feet in length, with a head that is three and one-half feet long. The largest of the Mosasaurs, however, sometimes attained a length of forty feet, and such an animal would have a head fully five feet long. Some of the small adult species were scarcely more than eight feet in length.

    The seas that rolled over Kansas in Cretaceous times contained thousands of these animals, and in the chalk bluffs of that region their remains are in such a perfect state of preservation that we are not only acquainted with their skeletal structure but with their external appearance as well. Impressions made by the body in these soft sediments before decomposition had set in have been found, showing that in life they were covered with small overlapping scales. In fact, small areas of skin impressions were found with the Tylosaurus specimen here discussed. The most unusual discovery relating to the appearance in life of an animal long extinct, was the detection of color markings by Doctor Williston, who

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An Extinct Sea Lizard from Western Kansas

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observed on one specimen carbonized pigment, which showed that the sides of the body were marked by narrow, diagonally placed parallel bars.

    One of the unique features of Tylosaurus, and for that matter of all mosasaurs, is an articular joint in about the middle of each lower jaw, which permits considerable movement between the front and back parts, both up and down and sideways, though chiefly in the latter direction. This feature in conjunction with their very loose attachment to one another at the forward ends allowed the jaws to expand and thus enabled them to swallow large objects, for it is certain that not all of the animals which the Tylosaurus devoured were small, for since their teeth were not adapted for the rending of bodies they must have been swallowed whole.

    While most of the Mosasaurs were predatory animals having the jaws provided with numerous sharply pointed teeth that were well adapted for catching fish - for it is thought fish formed their principal article of diet, since fish bones and scales have been found among the fossilized stomach contents - there was another kind of Mosasaur, Globidens alabamaensis [sic], that formerly lived in North America and enjoyed quite a different kind of food as shown by the very peculiar shape of its teeth. Reference is made to a specimen in the National Museum found some few years ago in the northern part of the State of Alabama which has nearly spherical teeth.

    Mosasaur specimens have not only been found in many parts of the United States, but in South America, Belgium, Holland, Russia, France and New Zealand, but nowhere are they more abundant or are their remains found in a more perfect state of preservation than in the chalk deposits of western Kansas.