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Compared tyrannosaurid interrelationships
Sereno P.C.& Brusatte S.L. 2011. Comparative assessment of tyrannosaurid
interrelationship. Journal of Systematic Palaeontology 7(4): 455-470.
We employ a new comparative method to four cladistic analyses of tyrannosaurid
dinosaurs to identify root causes for differences between phylogenetic results.
The comparative method is a three-step procedure that (1) adjusts competing
hypotheses so they share equivalent taxonomic scope, (2) isolates the character
data relevant to the common problem, and (3) divides relevant character data
into shared and novel partitions. It is then possible to quantify the degree of
similarity between character data using three indices (ancestor similarity
index, character similarity index and character state similarity index).
The most parsimonious cladograms generated by the four analyses of
tyrannosaurids appear fairly congruent, with two subclades present in all four
analyses (Albertosaurusand Gorgosaurus versus Daspletosaurus, Tarbosaurus and
Tyrannosaurus). A comparative examination of the underlying character data,
however, highlights striking differences in character selection and significant
differences in character state scores. Character selection and differences in
scoring are root causes for phylogenetic incongruence. Comparative analysis
reveals the existence of many data-level differences that remain largely
obscured when comparison is limited to the most parsimonious cladograms.
"As a Professor of Science, I assure you we did in fact evolve from filthy monkey
men." Hubert J. Farnworth.