Therizinosauria re-evaluated in new Journal of Systematic Palaeontology

[bh480@scn.org]

From: Ben Creisler
bh480@scn.org

In case this paper has not been mentioned yet:

Lindsay E. Zannoa, 2010. 
A taxonomic and phylogenetic re-evaluation of 
Therizinosauria (Dinosauria: Maniraptora).  
Journal of Systematic Palaeontology 8(4): 503 ? 543 (2010)

Therizinosaurians are among the most poorly understood 
dinosaurs. Their unusual morphology and fragmentary 
fossil record has precluded a synthetic understanding of 
the group since their remains were first discovered over 
60 years ago. Although the clade was recently 
substantiated as a monophyletic group of maniraptoran 
theropods, little foundational work has been conducted at 
the species level. A recent plethora of therizinosaurian 
discoveries - including the most complete primitive and 
derived members recovered to date - permits an alpha 
taxonomic and phylogenetic re-evaluation of the clade. 
The phylogenetic analysis presented is the most 
comprehensive yet conducted for Therizinosauria, and 
provides a foundation for scrutinizing previous 
definitions of Therizinosauria, Therizinosauroidea and 
Therizinosauridae. Here, support is provided for the 
maintenance of all three taxa; however, Therizinosauria 
is redefined and Falcarius is excluded from 
Therizinosauroidea. In addition, the previously described 
therizinosauroids, Beipiaosaurus, Enigmosaurus, 
Suzhousaurus, Segnosaurus and Therizinosaurus, are 
rediagnosed and photodocumented. In contrast to other 
analyses, the ingroup topology recovered in this study 
suggests intermediate (therizinosauroid) status for 
Neimongosaurus, Erliansaurus and Enigmosaurus (based on 
relatively primitive pelvic morphology), despite the 
derived forelimb anatomy evident in the former two taxa. 
Here, the large-bodied taxa Nothronychus and 
Nanshiungosaurus brevispinus are recovered as 
therizinosaurids. This discrepancy indicates a relatively 
complex pattern of mosaic evolution, which may ultimately 
be found to correlate with body-size trends in the clade. 
This work also reviews the chronostratigraphic and 
biogeographic distribution of therizinosaurian taxa and 
putatively referred elements and finds no compelling 
evidence of the clade outside of Asia and North America, 
nor for the referral of therizinosaurian materials from 
Kazakhstan to cf. Neimongosaurus. Time calibration of 
ingroup relationships indicates a pre-Turonian dispersal 
event is needed to account for the presence of 
therizinosaurids in the Late Cretaceous of North America 
and Asia; this conclusion supports previous hypotheses of 
a Laurasian faunal interchange event during the Albian.  


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