The Proceedings of the Eighth International Conference on Creationism (2018)

Garner, P.A., and J. Asher. 2018. Baraminological analysis of Devonian and Carboniferous tetrapodomorphs. In Proceedings of the Eighth International Conference on Creationism , ed. J.H. Whitmore, pp. 458–471. Pittsburgh, Pennsylvania: Creation Science Fellowship. BARAMINOLOGICALANALYSIS OF DEVONIAN AND CARBONIFEROUS TETRAPODOMORPHS Paul. A. Garner , Biblical Creation Trust, P.O. Box 325, Ely, CB7 5YH United Kingdom paul@biblicalcreationtrust.org Jonathan Asher , Independent scholar 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 to Upper 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. KEY WORDS tetrapods, tetrapodomorphs, Devonian, Carboniferous, baraminic distance, multidimensional scaling, discontinuity Copyright 2018 Creation Science Fellowship, Inc., Pittsburgh, Pennsylvania, USA www.creationicc.org 458 INTRODUCTION According to evolutionary theory, the origin of tetrapods from a fish-like ancestor during the Devonian Period (conventionally 419.2-358.9 million years ago) was one of the major events in the history of life (Clack 2012). In this paper, we will use the term ‘tetrapod’ to refer to a vertebrate with limbs rather than paired fins. The more inclusive term ‘tetrapodomorph’ is used to refer to tetrapods plus some tetrapod-like fishes. Devonian sediments have yielded several families of these tetrapod-like fishes, including the elpistostegids which range from the Givetian to Frasnian of the Middle to Upper Devonian and are regarded as close to the evolutionary ancestry of tetrapods (Ahlberg and Johanson 1998; Table 1). Elpistostege from the Frasnian Escuminac Formation of Quebec, Canada, was originally described as a tetrapod based on a partial skull roof (Westoll 1938) and only recognized as a fish when more complete material was discovered half a century later (Schultze and Arsenault 1985). Panderichthys , from the Frasnian Gauja Formation of Latvia and Estonia, is much better known. Complete specimens reveal that Panderichthys has paired fins, a set of opercular bones and other fish-like features of the braincase and lower jaw (Ahlberg and Clack 1998; Ahlberg et al. 1996; Boisvert 2005; Boisvert 2009; Boisvert et al. 2008). However, in other respects its appearance is quite tetrapod-like, with a dorsoventrally flattened body and skull, dorsally placed orbits with supraorbital ridges, a large spiracular opening, frontal bones in the skull roof and an elongated snout with marginal nares (Vorobyeva 1977; Vorobyeva 1980; Vorobyeva 1992; Vorobyeva and Kuznetsov 1992; Vorobyeva and Schultze 1991). Even more tetrapod-like is Tiktaalik from the Frasnian Fram Formation of Nunavut Territory, Canada. Tiktaalik was described frommultiple, articulated specimens preserved in three dimensions, all from a single site on southern Ellesmere Island (Daeschler et al. 2006; Downs et al. 2008; Shubin et al. 2006; Shubin et al. 2014). Like Panderichthys , Tiktaalik has paired fins and a dorsal surface covered with overlapping rhombic scales. However, the snout is even more elongated, the spiracle is even larger and there is no bony opercular cover. Furthermore, Tiktaalik is distinguished from other tetrapodomorph fishes by possession of imbricate ribs, and a pectoral girdle with enlarged scapular and coracoid elements and highly mobile elbow-like and wrist-like joints. The head is also detached from the shoulder girdle, allowing flexure in the neck region. These features would have allowed the animal to support itself on a substrate using its pectoral fins in a limb-like manner. The earliest tetrapods to appear in the fossil record constitute a paraphyletic grade (i.e. not a clade) and may be referred to as ichthyostegalians (Table 2). Two of the best-known are Ichthyostega and Acanthostega , first described from fossil material discovered in the Famennian sediments of East Greenland (Jarvik 1952; Jarvik 1965; Jarvik 1996; Säve-Söderbergh 1932). Although the anatomy of Ichthyostega is known in considerable detail, no single specimen possesses a complete vertebral column and so the relative proportions of the body, including those of the head and limb girdles, have been reconstructed from partial, overlapping specimens (Ahlberg et al. 2005a). Ichthyostega is about one metre