Mirischia: a transitional theropod pelvis

Of the tens of thousands of mistakes I have made
while creating ReptileEvolution.com, the LRT and this blog over the last 7 years, this time I read ‘right’ and I applied ‘left’ to the ilium of Mirischia. Here corrections were made within 24 hours of its original posting. Thanks to MM for reporting the error. Apologies for the error.

Naish, Martill and Frey 2004
bring us an Early Cretaceous Santana Formation theropod pelvis and femur they named Mirischia asymmetrica (Fig. 1; SMNK 2349). They align the specimen with the French compsognathid (CNJ79), which is correct.

A key taxon
The traits visible in the Mirischia pelvis and femur (Fig. 1) are just enough to nest it between the Compsognathus clade (which includes tyrannosaurs, ornithomimosaurs and microraptors) and the Ornitholestes clade (which includes dromaeosaurs, troodontids and birds). And it is transitional in size, too.

Figure 1. The pelvis of Mirischia with color overlays and ilium correctly oriented. Below Mirischia pelvis compared to the CN79 specimen of Compsognathus and Ornitholestes.

Figure 1. The pelvis of Mirischia with color overlays and ilium correctly oriented. Below Mirischia pelvis compared to the CN79 specimen of Compsognathus and Ornitholestes. The yellow ‘bone’ between the pubes of Mirischia is ossified gut contents.

References
Choiniere JN, Clark JM, Forster CA and Xu X 2010. A basal coelurosaur (Dinosauria: Theropoda) from the Late Jurassic (Oxfordian) of the Shishugou Formation in Wucaiwan, People’s Republic of China. Journal of Vertebrate Paleontology. 30 (6): 1773–1796.
Naish D, Martill DM and Frey E 2004. Ecology, systematics and biogeographical relationships of dinosaurs, including a new theropod from the Santana Formation (?Albian, Early Cretaceous) of Brazil. Historical Biology 16(2–4):57–70.

 

3 thoughts on “Mirischia: a transitional theropod pelvis

  1. No time to elaborate here, but you got the ilium backwards and don’t realize half of it is missing. It’s not just Naish et al.’s assumption, the ilium was originally articulated in the concretion (fig. 1 in Martill et al., 2000). Honestly, your reconstructions look nothing like real theropod pelvises for Mirischia or Zuolong. Just trust the authors who know something about theropod anatomy.

      • Good job correcting that, and you found much better relatives this time. But I hope this experience helps you to pay more attention to details and text in papers, since it’s not just a right vs. left thing, Rauhut et al. describe the preacetabular process and pubic peduncle in the text which you should have read. So often it seems you just look at a tree or a photo without checking the underlying data. Another Mirischia example is that it actually has a large fenestra in the left ischium, but you missed it because it’s not obvious in the photo unless you know what to look for. The right ischium has a structure like Ornitholestes though.

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