Southeastern Section - 64th Annual Meeting (19–20 March 2015)

Paper No. 8
Presentation Time: 10:50 AM


SCHWIMMER, David R., Earth and Space Sciences, Columbus State Univ, 4225 Univ. Ave, Columbus, GA 31907,

“The absence of transition fossils” has been claimed by “Creation Scientists” to be a fatal flaw in the evolutionary model. In fact, the existence of significant transitional suites between clades would inherently demonstrate evolution. This “absence…” claim may be debunked by numerous lines of reasoning and data, but especially by application of new information from fossil vertebrates. Vertebrates make exemplary fossils for evolutionary studies because they generally contain mineralized bones and/or teeth at all developmental stages, whereas many invertebrate clades likely had non-sclerotized ancestral or early forms which would rarely be preserved.

The notion of literal “transitional fossils,” among other fallacies, contains the false assumption that evolution is linear and simplistic. Nevertheless, there are many examples in the vertebrate record that force a rational mind to recognize characteristic morphologies of two or more significantly different crown groups in a single fossil clade, which is as close to “transition” as nature could present. Examples of dramatic “transitions” now well-documented include bony fish-to-tetrapods, basal synapsids-to-mammals, dinosaurs-to-birds, and terrestrial ungulates-to-whales. These pairings contain so many mutual characters that it becomes difficult to classify many species into either crown group. For example, “transitional” synapsid/mammal clades feature most mammalian synapomorphies, but retain reptilian jawbones and thus single bone ears. Further, they are formally classified as Mammaliamorpha, which is a taxon erected to accommodate these intermediate morphologies. If taxonomists must create intermediate classifications for such creatures, what better evidence of “transition” could be expected? Most refinements of these “transitional” associations have been discovered in the past quarter-century, and undoubtedly more will be found in the vertebrate record.