Earth Sciences - Palaeo Discussion Group - Luke Parry - University of Bristol - Title: Pruning the problematica: halkieriids are crown group molluscs

24 February 2017, 1.00 PM - 24 February 2017, 2.00 PM

Luke Parry - University of Bristol

G25, Reynolds Lecture Theatre, Wills Memorial Building

We are pleased to welcome our very own Luke Parry who will be leading the Palaeo Discussion Group:-

Title: Pruning the problematica: halkieriids are crown group molluscs
Abstract: Molluscs are an ancient and morphologically disparate animal phyla, spanning body plans from simple clams and garden snails to complex and intelligent cephalopods. Due to the vast morphological differences between the molluscan classes and their rapid radiation during the early Cambrian, establishing a coherent narrative for their body plan evolution and identifying the characters present in their last common ancestor has proven difficult from both palaeontological and neontological data. Fossils that may be pertinent to this question have been subject to highly divergent interpretations, obfuscating their evolutionary significance. Chief among these are the halkieriids, slug like animals with a dorsal covering of mineralized sclerites and either one or two shells situated at their anterior and posterior. Halkieriids have been considered to occupy the common stem lineage of various trochozoan phyla, the stem lineage of brachiopods, the molluscan stem group in a clade with Wiwaxia (Halwaxiida) or the stem lineage of the Aculifera (the chitons and aplacophorans). The main difficulty in distinguishing between these scenarios is an absence of unequivocal diagnostic characters of any particular animal group. Calvapilosa kroegeri, a new halkieriid from the Early Ordovician of Morocco preserves a polystichous radula with over 150 tooth rows, a key character linking halkieriids to the molluscan crown group as well as a single anterior, mineralized shell. Phylogenetic analysis places this new discovery deep in the stem lineage of Aculifera, revealing the characters shared between the last common ancestor of the molluscan classes.

All staff and students welcome.

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For further information, please contact Dr Jesus Lozano

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