Thursday, 30 June 2011

Whither Raptorex?


In my recent review of Tsuihiji et al's (2011) excellent recent paper on a juvenile Tarbosaurus, I made a reference to the taxanomic status of Raptorex kriegsteini and ended it with the phrase "watch this space" - and here's why:


Fowler DW, Woodward HN, Freedman EA, Larson PL, Horner JR (2011) Reanalysis of ‘‘Raptorex kriegsteini’’: A Juvenile Tyrannosaurid Dinosaur from Mongolia. PLoS ONE 6(6): e21376. doi:10.1371/journal.pone.0021376

Abstract

The carnivorous Tyrannosauridae are among the most iconic dinosaurs: typified by large body size, tiny forelimbs, and massive robust skulls with laterally thickened teeth. The recently described small-bodied tyrannosaurid Raptorex kreigsteini is exceptional as its discovery proposes that many of the distinctive anatomical traits of derived tyrannosaurids were acquired in the Early Cretaceous, before the evolution of large body size. This inference depends on two core interpretations: that the holotype (LH PV18) derives from the Lower Cretaceous of China, and that despite its small size, it is a subadult or young adult. Here we show that the published data is equivocal regarding stratigraphic position and that ontogenetic reanalysis shows there is no reason to conclude that LH PV18 has reached this level of maturity. The probable juvenile status of LH PV18 makes its use as a holotype unreliable, since diagnostic features of Raptorex may be symptomatic of its immature status, rather than its actual phylogenetic position. These findings are consistent with the original sale description of LH PV18 as a juvenile Tarbosaurus from the Upper Cretaceous of Mongolia. Consequently, we suggest that there is currently no evidence to support the conclusion that tyrannosaurid skeletal design first evolved in the Early Cretaceous at small body size.


Another paper of immense interest and freely available at PLoS One here. No doubt there will be further debate and response in the near future which we all look forward to. Now then - was it "Raptotyrannus" or "Nano rex"............?

Reference

Tsuihiji, Takanobu , Watabe, Mahito , Tsogtbaatar, Khishigjav , Tsubamoto, Takehisa , Barsbold, Rinchen , Suzuki, Shigeru , Lee, Andrew H. , Ridgely, Ryan C. , Kawahara, Yasuhiro and Witmer, Lawrence M.(2011) 'Cranial osteology of a juvenile specimen of Tarbosaurus bataar (Theropoda, Tyrannosauridae) from the Nemegt Formation (Upper Cretaceous) of Bugin Tsav, Mongolia', Journal of Vertebrate Paleontology, 31: 3, 497 — 517 DOI: 10.1080/02724634.2011.557116

4 comments:

qilong said...

Both this paper and the pachycephalosaur paper I just posted about deserve a lot of attention because of how much back story they have and how much they both go to help settle arguments. Both of them deal with ontogeny, but to various degrees. I think the Scott et al. paper is the better of the two, but this doesn't diminish Fowler et al. in efficacy.

Mark Wildman said...

Thanks for your recent comments Jaime - the ontogeneric express is gathering pace methinks.

Ian said...

Personally, I'm interested in hearing what Thomas Carr thinks about this, since he's done a lot of work on tyrannosaur ontogeny.

Mark Wildman said...

Couldn't agree more Ian and, hopefully, it won't be too long now

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