| Property | Value |
|
overview
|
My research focuses on early vertebrate diversity and evolution, the reconstruction of evolutionary pattern and process, and uses of fossils and systematic methods in evolutionary developmental biology. Ongoing projects cover the following areas:
1. The origin and early radiation of tetrapods, the origin of a tetrapod body plan, and the fin-to-limb evolutionary transition.
2. Primitive shark-like fishes and the early evolutionary radiation of jawed fishes (gnathostomes).
3. Ray-finned fish evolution: the ray-fins (actinopterygians) include the vast majority of living fishes
Living tetrapods range from humans to salamanders, aardvarks to apodans, and all points in between. The origin of tetrapods is one of the classic topics of vertebrate evolutionary studies, and covers wide variety of different kinds of question: the reconstruction of evolutionary pattern and organismal interrelationships (phylogeny); the origin of new body plans (morphological transformation); functional and behavioral change associated with the invasion of new habitats –the water to land transition (paleobiology). Recent and ongoing research has concentrated mostly on reconstructions of phylogenetic pattern encompassing the fish-tetrapod transition and the basal divergence of modern lineages (amphibians and amniotes). Previous work in this area has included the description of Acanthostega gunnari (Coates 1996 - pdf), the most completely known primitively fish-like tetrapod. Current research explores ways of analyzing and ‘mining’ large data sets (Ruta et al. 2003 - pdf; 2006 - pdf; Wagner et al. 2006 - pdf), the relation between major branching events in the tree of life and large-scale anatomical change, and how phylogenetically inferred patterns inform questions about developmental evolution, and vice-versa. The fin-limb transition is a particularly rich source of material in this respect (Coates & Clack 1990 - pdf; Coates & Cohn 1998 - pdf; Coates et al 2002 - pdf; Shubin et al. 2004 - pdf).
Primitive shark-like fishes (chondrichthyans) include the origins of modern sharks, rays and chimaeroids (rat fishes), early forms of which are much less well known than those of their bony relatives. The absence of a bony internal skeleton has resulted in a fossil record consisting mostly of isolated teeth and scales, although rare caches of spectacularly preserved skeletal remains are known. Modern sharks tend to be treated as primitive relics of an earlier era, although this sits uncomfortably with the alternative clichéd view of sharks as ultimate marine predators. Both notions rest on shaky foundations. Modern sharks are not especially similar to their early relatives, whose sometimes bizarre anatomy in certain respects converges on that of early bony fishes (osteichthys) (see example of Akmonistion; Coates et al. 1998 - pdf; Coates & Sequeira 2001 - pdf). The aim of the chondrichthyan project is to resolve early chondrichthyan phylogeny by means of using a wide variety of data, and to provide the basis for a renewed examination of basal jawed vertebrates as a whole. All early gnathostomes are possible targets for future work, including memberships of the extinct groups such as placoderms and acanthodians, as well as key gnathostome anatomical systems, including jaws, teeth, and paired fins (Smith & Coates; Coates Acta Biotheoretica).
The ray-finned fishes are the largest and most diverse group of living vertebrates, but little has been agreed about the timing and pattern of their early evolution. Collaborative research with Prince and Ho labs, and colleagues elsewhere, has resulted in a revised time-scale of their evolutionary history and raised major questions about the completeness of their fossil record (Hurley et al 2007 - pdf; and the cover image). This work exemplifies OBA’s aim to promote integrative research, and uses a total-evidence approach combining fossils with molecular sequence data drawn from mitochondrial and nuclear genes. Fossil ray-finned fishes are probably the largest and least explored resource for the exploration of vertebrate historical biodiversity, and the potential for further research is considerable (Coates 1999 - pdf)
|