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SUMMARY:The early evolution of animal life and the generation of form - Fr
 ances Dunn\, Oxford University Museum of Natural History &amp\; University
  of Oxford
DTSTART:20250610T110000Z
DTEND:20250610T120000Z
UID:TALK225214@talks.cam.ac.uk
CONTACT:Dr Rachael Rhodes
DESCRIPTION:The radiation of animals across the Ediacaran-Cambrian transit
 ion is one of the most transformational events in Earth history\, represen
 ting a step change in the evolution of the biosphere. While fossils from t
 he Cambrian are readily recognised as belonging to extant groups\, those f
 rom the late Ediacaran Period document organisms with distinctive forms an
 d no counterparts among living species. This has resulted in a number of d
 ifferent phylogenetic interpretations\, ranging from animals to fungi to a
 n extinct Kingdom but with little historical consensus. In this talk\, I w
 ill focus on the rangeomorphs – frond-like taxa with ‘fractal’ branc
 hing – which are among the oldest Ediacaran macrofossils. My work uses m
 orphogenetic pattern to produce a phylogenetic bracket for the rangeomorph
 s and this study of Ediacaran developmental biology has identified them as
  animals and stem-group eumetazoans to the exclusion of alternatives. Rang
 eomorphs thus occupy a critical position in the tree of animal life\, post
 -dating the origin of true tissues and body axes\, but likely pre-dating t
 he origins of a gut and other defining eumetazoan characters. This conclus
 ion enables us to integrate rangeomorphs into debates concerning the mode 
 of early animal evolution\, for example\, in the influence of the evolving
  regulatory genome on the evolution of animal complexity. Some authors hav
 e suggested that a step-change in the regulation of early-acting genes imp
 licated in development may explain the burst of morphological variety whic
 h underpins the Cambrian Explosion. However\, our data suggest that rangeo
 morph growth was conserved and predictable with a morphogenetic strategy t
 hat was highly regulated\, demonstrating that the most ancient eumetazoan 
 fossils known already manifest evidence of complex developmental regulatio
 n. Instead\, we suggest that the evolution of the rangeomorphs (and other 
 Ediacaran macrofossils) may have catalysed the explosion of morphological 
 variety observed during the Cambrian Explosion by promoting the diversific
 ation of novel phenotypes and behaviours through the introduction of space
 - and time-limited resources\, resulting in a rougher fitness landscape th
 an earlier in Earth history.  Previous studies have implicated a roughenin
 g of the fitness landscape as a potential driver for the Cambrian Explosio
 n but this hypothesis remains untested. Using eco-evolutionary simulations
  we propose that morphological disparity is an emergent property of a roug
 hening fitness landscape providing a possible mechanism for saltational ju
 mps in the evolution of morphological disparity through time\, including d
 uring the Cambrian Explosion.
LOCATION:Department of Earth Sciences\, Tilley Lecture Theatre
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