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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.

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"As a Professor of Science, I assure you we did in fact evolve from filthy monkey 
men." Hubert J. Farnworth.