Lines of Phyletic and Biological Development of the Ichthyopterygia
Introduction The great order of the Ichthyopterygia, known from Permian to Upper Cretaceous times, is formed by the Ichthyosauria, Omphalosauria, and Mesosauria.

A special study of all Liassic Ichthyosauria from the English and German Lias led me to a synoptic classification, which has also extended over all Jurassic and Cretaceous forms. Those of the Triassic are already well known from the classic memoirs of Merriam. Through recent additional observations of the extensive Mesosaurus material at Tubingen (from Brazil) this group may be reinterpreted and reviewed. Therefore it is possible for the first time to form an idea of this highly diversified and long-lived order of the Ichthyopterygia.[2][1]

Mesosauria

I need not repeat the reasons why the Mesosauria can not possibly be the forerunners of the Ichthyosauria,[3][2] but many features in the skull and skeleton demonstrate convincingly their common origin. The Mesosauria are, it appears to me, a primitive short side . . .

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