Cretaceous Reptiles of the US (1865)

crocodilian skull

Joseph Leidy had already completed "Cretaceous Reptiles of the United Stated" in 1860, but it was not published until the Civil War had ended in 1865 (1). This 140 page monograph covered almost all of Leidy's work on Cretaceous reptiles up until that time. It includes his most famous fossil animal, Hadrosaurus foulkii.

A total of 21 species are covered. These include crocodiles, mosasaurs (large extinct marine lizards), turtles and a couple of dinosaurs. Almost all of these animals came from New Jersey, but specimens from North Carolina, Georgia, Alabama, Mississippi and Nebraska were also studied. Leidy was well aware of the shortcomings posed by the limited geographic scope of this monograph, especially given the knowledge that vast Cretaceous deposits in the American West remained unexplored. He wrote:

"When we consider the great development of the Cretaceous formations in the western and southern portions of the United States in comparison with those on the eastern border, from which nearly all our fossils have been obtained, we may anticipate many additions."

hadrosaurus leg bone

Leidy's prediction of paleontological discoveries from the American West became true, but only after he abandoned paleontology to his younger and more combative colleagues, E. D. Cope and O. C. Marsh (2). The western fossil beds would yield paleontological treasures that transformed vertebrate paleontology and shifted its center from Europe to North America.

In addition to finding new species, Leidy had hoped that the exploration of western fossil beds would augment the limited information provided by the fragmentary fossils already at his disposal.

The most important reptile presented in "Cretaceous Reptiles of the United States" is Hadrosaurus foulkii, the most complete dinosaur fossil of its time. Leidy had named and described Hadrosaurus in 1858, but this publication contained the first illustrations (lithographic plates) and a more thorough description of the bones. In addition, he provided an analysis of how its battery of teeth chewed plant material.

"Cretaceous Reptiles of the United States" is also noteworthy for a scathing review it received in the Geological Magazine of London in 1868:

 

"Altogether we must, while expressing our thankfulness for the memoir, such as it is, say that it is the least able contribution to paleontology that we remember. Its best praise is that it contains no quackery; its worst condemnation is that it contains no science. It will always be valuable for its plates."

The anonymous reviewer identified himself only as "H". Edward Drinker Cope (who was highly praised in the review) ascribed the criticism to Thomas Huxley, a leading British scientist known for his vociferous advocacy of Darwin's theory of Natural Selection. Huxley, however, denied he was the author. The true identity of the reviewer may never be known (3).

The harsh criticism of this review distressed Leidy. He took pride in the quality and accuracy of his work, and his work was highly regarded by the leading scientists of his day. The core of the "H" critique appeared to have been directed at Leidy's reluctance to generalize and theorize about his findings. Leidy's science was descriptive and extremely cautious, much to the exasperation of some of his colleagues.

Some of his reluctance to theorize can be attributed to his humble and retiring nature. But his scientific style was more a consequence of conviction than personality. Leidy's mission, as he saw it, was to collect facts and let others theorize:

"The time will come when such investigations as I may add from time to time may prove of value, and I believe I can do more good to science in adding some new facts than in preparing articles for popular treatise."

Six lithographic plates from "Cretaceous Reptiles of the United States" (1865) are presented here:

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Notes:

  1. Smithsonian Contributions to Knowledge 192. Vol. XIV. 1865
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  2. Leidy last significant contribution on Cretaceous reptiles was part in his 1873 monograph, "Contributions to the Extinct Vertebrate Fauna of the Western Territories". This publication was also Leidy's last major writing on paleontology. It contains numerous indications of the emerging scientific muddle and Leidy's personal frustrations in dealing with the increasingly bitter rivalry between Marsh and Cope. This rivalry would become known as the Bone Wars.
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  3. E. D. Cope's conclusion that Thomas Huxley was the author of the "H" review is revealed in a letter he wrote to his father in 1868. Huxley had earned the epithet of "Darwin's Bulldog" because of his intense advocacy of Natural Selection and his fierce attacks on its opponents. He actively sought corroboration of Darwin's theory from paleontology and was stymied by the anti-Darwinist stance of many prominent paleontologists. Huxley may have also been frustrated by Leidy's reluctance to join with him in one of the great scientific debates of the 19th century. On the other hand, the cordial relationship Leidy and Huxley, Leidy's early support of Darwin and the high esteem Huxley and other European scientists held for Leidy suggest that Huxley would not have written such a review.
    The letter Cope wrote to his father also revealed Cope's agreement with the "H" review. Interestingly, Cope had (along with Louis Agassiz of Harvard) reviewed and approved Leidy's manuscript for publication by the Smithsonian.
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