Amid all of this intellectual ferment, yet another revolution was not-so-quietly taking place. This was the cladistic revolution (see Chapter 3). The idea was not so new (although not nearly as old as that of endothermic dinosurs); the basics had first been articulated by a German entymologist, Willi Hennig, in 1950 (Figure 14.11). English translations of Hennig's ideas appeared in 1966 and again in 1979. Hennig's great insight was, as we've seen in Chapter 3, to Figure 14.9. John H. Ostrom (1928-2005), Yale University, the paleontologist whose develop a scientific (testable) method whereby ideas ignited the modern era of dinosaur research. relationship can be inferred from anatomy.
The method was initially not widely appreciated, and the results were a bit shocking to people trained in the traditional Linnaean classification system (see, for example, Box 4.2), with the result that between 1966 and 1990 (or thereabouts), this approach engendered considerable controversy. Nonetheless, when the computer algorithms were developed that allowed cladograms to be generated from large and complex datasets, cladograms became a ubiquitous and powerful tool for deciphering the relationships of both living and extinct organisms (including dinosaurs).
Starting in 1984, cladistic analysis exploded onto the dinosaurian systematic scene. The results were four-fold:
1. The disbanding of "Thecodontia."
3. The internal pattern of relationships within ornithischian and saurischian clades.
4. The relationships of birds to dinosaurs.
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