One third of dinosaur species may have to go, according to an article in PLoS One 27 Oct 2009 and Fossil Science, 1 Nov 2009. A new study of dinosaur growth patterns indicates that some dinosaurs classified as different species, and even different genera, are actually the same species at different stages of life. Dinosaur experts John Horner and Mark Goodwin analysed the bone structures of the dome headed Pachycephalosaurus with that of another dome headed dinosaur named Stygimoloch spinifer, discovered in Montana in 1973, and a skull discovered in South Dakota 2006 given the fanciful name of Dracorex hogwartsia in honour of Hogwart’s Academy of Harry Potter books. Horner and Godwin’s study indicates Stigimoloch was a sub-adult form of Pachycephalosaurus, and Drocrex was a juvenile form that showed some thickening of the skull but had not developed a dome. Recent research indicates that the elaborate horns, frills and nodules on dinosaur heads were not for fighting or defence, but were for courtship displays or species recognition. Therefore, they may have varied enormously between different stages of life. They are made from a kind of bone called metaplastic bone, which can be quickly formed, broken down and rebuilt. For this reason a three horned dinosaur named Torosaurus is no longer classified as a separate species, as are several duck-billed hadrosaurs and maybe even Nanotyrannus, a miniature version of T. rex. Horner suggests that one third of named dinosaur species may be simply different growth stages of other named species.

Fossil Science

Editorial Comment: The classification of living species is determined by their ability to interbreed. All stages of their life cycle can be observed, as can any variation within a live species. This cannot be done for fossils. They don’t mate, or eat, or do anything, so there is much guess-work about fossils that are not identical to try to answer the question: “Are they more than one species?” As there is no scientific kudos or naming rights for finding another specimen of an already known species, we have no doubt that many similar fossils have been given new species names on the most trivial differences.

If Horner and colleagues are correct in interpreting the bony excrescences on dinosaur heads to be for courtship display and species recognition, they may be quite different for males and females, as well as at different stages of life, and this would further decrease the number of named species. Horner’s suggestion about dinosaur horns also fits with Genesis. In the original good world, animals would not have to fight for food or mates. Therefore, horns on any animal were for peaceful purposes, such as indicating age, sex and species. Later in the history of the world, animals that already had these structures used them in the struggle for life that began after the world degenerated because of human sin and God’s judgement. (Ref. nomenclature, classification, ontogeny)

Evidence News 24 March 2010