Multiple Dinosaurs Reclassified as One Species

It’s tough sometimes to draw the line between species – especially when dealing with fossils.  A report in Science suggests that three bone-headed dinosaurs are probably just different stages of one species.¹  These had been named Pachycephalosaurus, Stygimoloch and Dracorex.
    Erik Stokstad, reporting on activities at the meeting of the Society of Vertebrate Paleontology last month in Austin, Texas, said that two veteran dinosaur hunters knocked heads over the classification of these thick-skulled dinosaurs that may have knocked their own heads together in real life.  Jack Horner proposed lumping three specimens into one species, but Robert Bakker opposed it on the grounds that they look so dramatically different.  Horner and others, though, are convinced that changes in canals visible in the skulls represent different stages of growth from youth through adolescence to adult forms.  He postulated that bony growths on the head could have changed during maturation.  (It’s not clear, incidentally, whether these dinosaurs or scientists actually did butt heads with each other in real life.)
    Stokstad said, “If Horner turns out to be right, the diversity of pachycephalosaurs would be 50% lower than previously thought for the latest Cretaceous.”  Horner said this would be consistent with the belief that “other kinds of dinosaurs were also declining in diversity at the time.”
    Claims of new dinosaurs continue.  James Owen said in National Geographic that “A forgotten museum fossil that had been gathering dust for more than a century is actually from a mysterious British dinosaur that represents an entirely new family, scientists have discovered.”  Science Daily described how researchers in Australia are trying to correlate dinosaur bones down under with those known from other parts of the world.

1.  Erik Stokstad, “Did Horny Young Dinosaurs Cause Illusion of Separate Species?”, Science, 23 November 2007: Vol. 318. no. 5854, p. 1236, DOI: 10.1126/science.318.5854.1236.

Did you know that the biological concept of a species is fraught with difficulties?  Philosophers question whether scientists are “discovering” species divisions, as if “carving nature at its joints” (Plato), or whether they are engaged in a purely human activity of imposing our own patterns on observations in ways we find useful.
    The “biological species concept” we learn in school (species are populations that can produce fertile offspring) doesn’t work for fossils, nor for the vast majority of organisms, which are asexual.  Taxonomy since Linnaeus has been a battle between the lumpers and the splitters.  There is also the reward motivation.  Identifying a “new” species can bring you fame.  You might even be able to name it after yourself.  Remember Nebraska Man?  The human ancestor tooth was named for its discoverer, Hesperopithecus haroldcookii (see original 1922 paper from Science).  Cook must have been mighty proud till the tooth was identified as from an extinct pig.
    Horner thinks the lumping makes sense according to an evolutionary pattern of declining diversity in the late Cretaceous.  But he has just undermined a criterion of diversity to do so.  One wonders just how much data are force-fitted into evolutionary stories by tweaking parameters according to flawed assumptions, based on a prior commitment to Darwinist historical geology.