HETEROCHRONY IN THE CENOZOIC TURRITELLINE GASTROPODS OF NEW ZEALAND

Evolution in turritelline gastropods (Family Turritellidae) over the past 100+ million years is characterized by abundant speciation and ubiquitous heterochrony. More than 1500 fossil and Recent species have been described and their mode of growth preserves the entirety of their shell from larvae to death, allowing detailed comparison of heterochronic morphological changes within and between species to be made.

The turritellines of New Zealand offer a particularly good laboratory for investigation of these themes, as they have an excellent and well known Cenozoic fossil record and are represented by modern species around the coast today. In particular, the Zealand turritelline genus Zeacolpus appears to display periods of both anagenetic and cladogenetic change through its geological range from the middle Eocene to Recent.

Even with the advantages of working with such a group, a lack of adequate phylogenies has proved problematic in many studies. Despite obvious differences in shell shape between species, the group has often been dismissed as being too character-poor to allow for any sort of phylogenetic analysis and it has been extremely difficult to construct phylogenies for turritelline gastropods using traditional approaches to character description and delimitation. Without a phylogeny in place, it has been difficult to draw conclusions about the pattern of speciation within lineages. However, newer methods incorporating geometric morphometric approaches to defining characters have shown promise in allowing taxa to be incorporated into phylogenetic analyses. I present a new method for phylogenetic analysis in turritellines and a preliminary phylogeny of the group.