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SUMMARY:The Origin of the Ornithischian Bauplan - Professor David Norman\,
  University of Cambridge Department of Earth Sciences
DTSTART:20221017T170000Z
DTEND:20221017T180000Z
UID:TALK184037@talks.cam.ac.uk
CONTACT:Buck Blake
DESCRIPTION:"Our understanding of the pattern of dinosaurian relationships
  has been challenged recently (Baron et al. 2017 Nature). Continuing this 
 period of reassessment\, a large-scale phylogenetic analysis (Müller & Ga
 rcia\, 2020) recovered taxa\, often referred to as silesaurids\, on the br
 anch leading to the clade Ornithischia (= “bird-hipped dinosaurs”). Ho
 wever\, the analysis that produced this novel topology used a dataset that
 \, in its original form\, did not include early representatives of Ornithi
 schia\, and did not incorporate all the anatomical characters that have be
 en suggested to unite Ornithischia with the other principal dinosaurian cl
 ades. These latter issues have been addressed by expanding taxon represent
 ation and adding anatomical characters to the original dataset. Our analys
 is of the revised dataset (Norman et al. 2022 ZJLS) supports the hypothesi
 s that ‘silesaurids’ comprise a paraphyletic grouping (more correctly 
 referred to by the informal terms silesaurs or silesaurians) on the stem o
 f Ornithischia. It can be demonstrated that silesaurs acquired anatomical 
 characters anagenetically\, culminating in the generation of recognisably 
 ornithischian dinosaurs. This\, in turn\, creates a taxonomic conundrum. T
 o resolve the latter\, we retain the name Ornithischia for an inclusive cl
 ade that includes its stem-lineage (silesaurs + traditional ornithischians
 ) and revive Richard Owen’s long-forgotten taxon Prionodontia (= “coar
 se edged teeth”) for the more exclusive clade containing only definitive
 ly “bird-hipped” dinosaurs. This revised taxonomic framework offers st
 ability between the clades Ornithischia\, Theropoda and Sauropodomorpha\, 
 while further analyses will continue to refine and re-shape the dinosauria
 n tree. If a consensus were to support our new hypothesis then paradoxical
 ly\, but perhaps logically\, the earliest ornithischians are saurischian!"
LOCATION:Tilley Lecture Theatre\, Department of Earth Sciences\, Downing S
 ite
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