226 Paleontology IV: Morphology and Phylogeny

Wednesday, 12 October 2011
8:00 AM - 12:00 PM
Room 205CD

EXPLORING THE STRUCTURE AND ORIGIN OF METAZOAN MORPHOLOGY

Paper number: 226-2
Program: Technical Sessions
Time: 8:15 AM – 8:30 AM

Authors

Abstract

The Cambrian explosion was a formative event in the history of life on Earth. Two major questions remain in the exploration of this event. What is the pattern of morphological diversification through this interval? And, what are the underlying mechanisms generating the increase in morphologic forms and complexity. An understanding of the mechanisms requires a description of the morphologic patterns, but studies of morphologic diversity (disparity) have been limited to lower taxonomic levels because of the inherent difficult in quantifying and comparing vastly different organisms. Building a morphospace that contains the morphologic diversity within metazoans requires a large character set to approximate the distances between taxa in a meaningful manner. The construction of the morphological relationships between taxa is a stepping-stone toward a better understanding of the Cambrian explosion and disparity throughout the Phanerozoic.

The character matrix used in the current study contains 1800 morphological traits for 396 clades including 207 terminal taxa (ranging in taxonomic rank from genera to phyla), representing in total 34 phyla. The 207 taxa group within morphospace roughly according to their phylogenetic affiliation. Arthropods and chordates contain the largest within phyla disparity and are located on the opposite extremes of the primary axis. The terminal taxa were then placed into a modern phylogenetic framework and the character states were modeled for the ancestral node of the phylum to normalize taxonomic rank.

The distribution of taxa within this morphospace can then compared statistically with other datasets to explore the relationships between genotype and phenotype. Comparisons of the distances between taxa indicate that miRNAs, genome size, and the number of cell types are consistent with morphology, showing promise in the production of novel morphologies. The presence and abundance of protein families, protein superfamilies, and protein architectures are inconsistent with morphology, such that the evolution of new proteins may generate new features, but proteins overall do not appear to play a role in generating the structure of metazoan morphospace.