Paper Abstracts

Devonian and Carboniferous tetrapodomorphs

P.A. Garner, J. Asher

Discipline: Geology

Abstract: According to evolutionary theory, the origin of tetrapods (or limbed vertebrates) from a fish-like ancestor during the Devonian Period was one of the major events in the history of life. Devonian sediments have yielded several families of tetrapod-like fishes, including the elpistostegids which range from the Givetian to Frasnian of the Middle Devonian and are regarded as close to the evolutionary ancestry of tetrapods. Two of the best-known "early" tetrapods are Ichthyostega and Acanthostega, first described from fossil material discovered in the Famennian (uppermost Upper Devonian) sediments of East Greenland. These taxa (and others subsequently described) display mosaic combinations of fish-like and tetrapod-like characters, along with some unique traits (such as polydactyly) not found in more "derived" tetrapods. Creationists have claimed that these organisms are not evolutionary intermediates, but were rather the inhabitants of aquatic environments associated with a pre-Flood floating forest biome, with morphologically intermediate traits that equipped them for life in an environment that was itself intermediate between the sea and the land. This paper evaluates the baraminic status of a range of Devonian and Carboniferous fishes and tetrapods using the techniques of statistical baraminology. Baraminic distance correlation (BDC) and three-dimensional multidimensional scaling (MDS) are applied to six previously published character-taxon matrices. The results reveal little evidence of continuity, and significant evidence of discontinuity, between the elpistostegids and tetrapods such as Ichthyostega and Acanthostega, consistent with the creationist claim of separate ancestry. However, further work will be required to elucidate the baraminic relationships within these presumably apobaraminic groups.