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Williston, S.W. 1891. Kansas Mosasaurs.

Science. 18(463):345.

Copyright © 2003-2010 by Mike Everhart

ePage created 10/12/2003; Last updated 03/09/2010

ABOVE: Restoration of Clidastes velox Marsh from Williston (1893)

Wherein, S. W. Williston provides the first complete (although brief) description of a Kansas mosasaur (Clidastes (velox) propython Marsh).  For unknown reasons, Williston ignores Tylosaurus Marsh as a valid genus, preferring instead to use Liodon Owen.

  December 18, 1891]      SCIENCE                                  345


Kansas Mosasaurs.

     HITHERTO, no adequate description or figure has ever been published of the complete anatomy, or even of the skull, of any member of the extinct group of reptiles known as the Mosasaurs or Pythonomorpha. Fortunately, however, my able friend Dr. Baur has recently had the opportunity to thoroughly study an excellent specimen of one of the Kansas forms, and his figures and descriptions, when published, will doubtless be of great interest. The University of Kansas has, within recent years, obtained one of the most, valuable collections of these animals now extant. Among this material, there is one specimen of especial interest, by reason of its remarkable completeness, consisting, as it, does, of skull and connected vertebrę to the tip of the tail, with ribs, extremities, and cartilages in position,

     Before briefly describing this specimen, which belongs to a different genus from that studied by Dr. Baur, I may be permitted to offer the following remarks upon the nomenclature of the Kansas forms, based upon larger opportunities than have been enjoyed, I believe, by any other investigator.

     The following generic names have been proposed or adopted by various writers for the different forms of these reptiles from the Kansas Cretaceous: Liodon Owen, Platecarpus Cope, Clidastes Cope, Sironectes Cope, Lestosaurus Marsh, Tylosaurus Marsh, Edestosaurus Marsh, and Holosaurus Marsh. Three genera, only, can be readily and positively distinguished among the material. The names now recognized for these, and with justice, are: Liodon, Platecarpus, and Clidastes. Two others, Sironectes and Holosaurus, have, possibly some claims for recognition, but the evidence in favor of either is, so far, very weak. Holosaurus is not synonymous with Sironectes, as affirmed by Cope and followed by Dollo. Holosaurus rests almost solely upon a single character, the non-emarginate [emarginate = notched] coracoid; in other respects nothing is known to separate it from Platecarpus. In fact, Platecarpus itself may possess this very character. That the character was not considered by the author of Holosaurus as important is evidenced by the following. In the American Journal of Science (Vol. iii, , June, 1872, p. 5 of separate) he says: "There is certainly no emargination in the coracoid of Clidastes, Edestosaurus, and Baptosaurus, as specimens in the Yale Museum conclusively prove." A figure of the coracoid of Clidastes (Edestosaurus) dispar, given in the same paper, shows the bone entire. In the same paper in which Holosaurus is figured and described (Amer. Jour. Sci., vol. xix., pp. 83-87) a restoration is given of the shoulder girdle of "Edestosaurus dispar Marsh," in which the coracoid is very conspicuously seen to be emarginate. That this was not an error on the part of the artist, I can vouch, for the specimen from which the figure was made was collected and restored by myself, There is a lack of consistency here somewhere.

A fuller discussion of the genera and generic characters of the Kansas material, I leave to a future occasion. As there have been more than twice too many generic names given; so, too, it is pretty evident that there is even a greater proportion of synonyms among the specific names, The specific nomenclature is at present, however, a subject of great intricacy, of which no one is master. Mr. E. C. Case of the State University will shortly publish a paper on this subject.

     With these general observations, I will now give a brief description of the specimen above mentioned; a fuller description, with illustrations, will appear later. The specimen is a Clidastes (Edestosaurus) and, from Mr. Case's studies, probably C. velox Marsh, which is apparently the same as the earlier described C. cineriarum Cope. The specimen measures, from the tip of the tail to the tip of the rostrum, one hundred and thirty-nine and one-half inches [12 feet, 7.5 inches], including altogether one hundred and seventeen vertebrę, the whole regionally divided as follows: skull, seventeen and one-half inches; cervical region, seven vertebrę. eight and one-half inches; costifarous, post-cervical region, thirty-four vertebrę, fifty-four and one-half inches; non-rib or chevron- bearing region, seven vertebrę, eight and one half inches; chevron bearing region, sixty-eight vertebrę, fifty-one and one half inches.

     All of the cervical vertebrę, save the atlas, have ribs, those of the axis, though, are very small, increasing in the last cervical to about three inches in length. The first to the ninth dorsal, or true thoracic ribs, those articulating with the cartilaginous sternum through the intervention of cartilaginous ribs, are of nearly equal length, about eight and one-half inches, and are moderately curved. The eleventh dorsal rib is but four inches long, and thence to the thirty-fifth or last, they decrease gradually to about two inches. The rib-bearing processes, as well as the vertebrę themselves, do not differ much throughout the series. The longest costal cartilage preserved does not measure over four inches; this will give, with the sternum and vertebrę, a total circumference of the thorax not exceeding thirty inches. [diameter = 9.5 inches]

    Immediately following the last costiferous [rib bearing] vertebra, are seven vertebrę with elongate transverse processes, and without chevrons. From the position of the pelvis, it was evidently attached to the first of these vertebrę, none of which can be properly called lumbar, with the first chevron-bearing vertebra, the transverse processes begin to decrease in length, and finally disappear in the twenty-fifth or twenty-sixth.

     The tail is elongate, slender, and compressed. the spines and chevrons having their greatest length only about one foot from the extremity, where the tail measures nearly six inches in height.

     Of the paddles little need be said. The hind pair was decidedly smaller and less strong than the fore pair, the latter having an outstretched expanse of about thirty inches.

     As a whole, this, one of the most specialized species of the most specialized genus of known extinct or recent lizards, was most marvelously serpentine and slender in its build, with an elongate, flattened, pointed head, short neck, very slender body, long, lithe, and vertically flattened tail, small but broad and strong paddle-like limbs. It is doubtful whether there was ever another vertebrated animal so admirably adapted for rapid and varied movements through the water. Though the smallest of the Mosasaurs, it was by far the most graceful in its proportions, the most delicate and exquisitely constructed in its details.

     It is certain that none of the Kansas forms of this order were covered with bony scutes, as described by Marsh, the bones so described being, undoubtedly, sclerotic plates.


University of Kansas, Dec., 1.

clidlima.jpg (14784 bytes) "Plate II, Left front paddle of Clidastes velox Marsh, two-thirds natural size." from Williston and Case (1892)

Adapted from a copy of original drawing by S. W. Williston.

Everhart (2002) noted that: "Between 1868 and 1874, most of the mosasaur species currently considered to be valid from the Smoky Hill Chalk Member of the Niobrara Formation in western Kansas (Everhart, 2001) were described by the 19th Century Philadelphia paleontologist, Edward Drinker Cope (1840-1897). These include: the genus Clidastes Cope 1868 and its type species, C. propython Cope 1869 (described from the Alabama chalk); the genus Platecarpus Cope 1869 and its type species, P. tympaniticus Cope 1869, and P. planifrons (Cope 1874); and the type species of Tylosaurus, T. proriger (Cope 1869), the first mosasaur described from Kansas, and T. nepaeolicus (Cope 1874). The genus Tylosaurus Marsh 1872 has a complicated history, including several name changes, which is too convoluted to be recounted here, save to say that Leidy (1873, p. 271) formally placed Macrosaurus proriger Cope 1869 into Tylosaurus."

Suggested references:                        See the Clidastes Collection in the Mosasaur Virtual Museum HERE

Baur, G. 1892. On the morphology of the skull of the Mosasauridae, Jour. Morphology, 7(1):1-22, 2 plates.

Everhart, M. J. 2001. Revisions to the Biostratigraphy of the Mosasauridae (Squamata) in the Smoky Hill Chalk Member of the Niobrara Chalk (Late Cretaceous) of Kansas. Kansas Acad. Sci. Trans 104(1-2):56-75.

Everhart, M. J. 2002. New data on cranial measurements and body length of the mosasaur, Tylosaurus nepaeolicus (Squamata; Mosasauridae), from the Niobrara Formation of western Kansas. Kansas Acad. Sci. Trans. 105(1-2):33-43. (See above excerpt)

Everhart, M.J. 2005. Oceans of Kansas - A Natural History of the Western Interior Sea. Indiana University Press, 322 pp.

Marsh, O. C. 1872. On the structure of the skull and limbs in mosasaurid reptiles, with descriptions of new genera and species. Amer. Jour. Sci.,   3(18):448-464, pl. 10-13.

Marsh, O. C. 1880. New characters of mosasauroid reptiles. American Journal of Science, Series 3, 19:83-87, with pl. i a.

Williston, S. W. 1893. Mosasaurs, Part II: Restoration of Clidastes, Kans. Univ. Quart. 2(2):83-84, 1 plate.

Williston, S. W. and Case, E. C. 1892. Kansas mosasaurs. Kansas Univ. Quarterly 1:15-32, Pl. II-VI.