7b. The Discovery of Hylaeosaurus, 1833


The third dinosaur to be recognized as such was discovered by Gideon Mantell in Tilgate Forest in 1832. Mantell said of his discovery: "I venture to suggest the propriety of referring it to a new genus of saurians...and I propose to distinguish it by the name of Hylaeosaurus." In a footnote, he explained that the name means "Wealden Lizard." Mantell continues: "The original animal in all probability differed as much in its external form as in its skeleton, from known species; we are certain that it was covered with scales, and there appears every reason to conclude that either its back was armed with a formidable row of spines, constituting a dermal fringe, or that its tail possessed the same appendage... the specific name of armatus, in either case, would not be inappropriate. Mantell estimated the size of the Hylaeosaurus at no more than 25 feet, which was half the size of Iguanodon and Megalosaurus, in his estimation.

Mantell published another illustration of the Hylaeosaurus slab in the fourth edition of his later book, The Wonders of Creation (1840). Interestingly, it was a different image, completely redrawn from this one. Click here to compare the two versions of the Hylaeosaurus fossil.


Mantell, Gideon. The Geology of the South-east of England. London, 1833. This work is part of our History of Science Collection, but it was NOT included in the original exhibition.

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