Thursday, December 2, 2010

Zuolong, a new basal coelurosaur from the Shishugou Formation

No, this isn't the 'important post' alluded to last time, but I had to take advantage of the opportunity to post on a new theropod so soon after it was announced (and before Andrea got to it!).  Today we see the publication of Zuolong, or "animal dragon", er... actually it's named after General Zuo Zongtang.  Avid theropod fans will know this as the basal coelurosaur skull shown and announced by Clark et al. at SVP 2002.  The description is nicely detailed and illustrated, and I look forward to seeing where it ends up in Cau's megamatrix.  The phylogenetic analysis is mostly in the supplementary data, so I can't evaluate it, though given Choiniere's past published analyses I'm crossing my fingers that taxa are completely coded this time around.  On the positive side, the authors do discuss in detail the alternative placements for basal coelurosaurs which cause the illustrated polytomy, and used a reduced consensus method to prune taxa from the tree a posteriori.  Nqwebasaurus was excluded since a redescription is in preparation for the Journal of African Earth Sciences, though I note the Limusaurus analysis found it to be a basal ornithomimosaur.  Tugulusaurus was sometimes not a coelurosaur, a result my supermatrix has also found.  Bagaraatan was either a tyrannosauroid or an ornithomimosaur.  Aniksosaurus was a basal compsognathid.  Proceratosaurus could be either a tyrannosauroid, compsognathid or ornithomimosaur, highlighting the caution I've been urging in assigning these small taxa to Tyrannosauroidea.  Of course I have no idea what the quality of the matrix is, so I don't know how important those results are.  On the negative side, Choiniere is again redefining taxa with "a modified version of the definition of Coelurosauria from Holtz et al. (2004) as all theropods more closely related to birds than to Sinraptor dongi."  There's no reason to change the standard Allosaurus external specifier that everyone's used up to this point, not to mention the error everyone else makes in using birds to define Coelurosauria contra Recommendation 11A.  In any case, I'm glad to see this description published, and look forward to the upcoming osteologies of Guanlong and Haplocheirus.

Much of the holotype of Zuolong salleei (IVPP V15912).  Note the sacrum plus proximal caudals were shifted in front of the pelvis for viewing purposes, and some elements like the scapula and several partial vertebrae are not shown.  Scale = 1 m. (after Choiniere et al., 2010)

Zuolong Choiniere, Clark, Forster and Xu, 2010
Z. salleei Choiniere, Clark, Forster and Xu, 2010
Early Oxfordian, Late Jurassic
Shishugou Formation, Xinjiang, China

Holotype- (IVPP V15912) (~3.1 m; ~35 kg; subadult) incomplete skull, premaxillary tooth, angular, two lateral teeth, partial axial neural arch, incomplete third cervical vertebra, incomplete fourth cervical vertebra, incomplete fifth cervical vertebra, incomplete eighth cervical vertebra, incomplete ninth cervical vertebra, partial tenth cervical neural arch, two dorsal centra, two fragmentary dorsal centra, incomplete sacrum, first caudal neural arch, second caudal neural arch, third caudal centrum, incomplete fourth caudal vertebra, three incomplete mid caudal vertebrae, two mid caudal centra, mid caudal neural arch, incomplete scapula, incomplete humerus, radius (137 mm), incomplete ulna, distal phalanx I-1, incomplete manual ungual I, partial ilium, incomplete pubes, femora (one distal; 336 mm), partial tibia, proximal fibula, partial phalanx I-1, pedal ungual I, metatarsal II (191.9 mm), phalanx II-1, metatarsal III (224.3 mm), partial metatarsal IV (~201.7 mm)

Diagnosis- (after Choiniere et al., 2010) large, slit-like quadrate foramen inclined medially at approximately 45 degrees with associated deep fossa on the quadrate; sacral centrum 5 with an obliquely oriented posterior articular surface that is angled anterodorsally; fovea capitis very large, occupying almost the entire posterodorsal surface of the femoral head; distal condyle of metatarsal III large relative to that of other metatarsals and bearing an anteromedially projecting flange on its anteromedial margin.

Skull elements of Zuolong salleei, scaled from figures in Choiniere et al. (2010). Note the squamosal's scale bar in figure 4 is assumed to be 1 cm instead of 3 cm as listed.  The mass above the orbit is the frontal and parietal in dorsal view.

Comments- This specimen was discovered in 2001 and announced in an abstract by Clark et al. (2002) as a basal coelurosaur. It was later described in more detail in an abstract by Choiniere et al. (2008), who used a version of the TWG matrix and found it to be one of the most basal coelurosaurs, sister to Tugulusaurus. Choiniere et al. (2010) named and described the taxon in depth, finding it either as a non-tyrannoraptoran coelurosaur in a trichotomy with Tugulusaurus or as a non-maniraptoriform tyrannoraptoran more derived than tyrannosauroids.

References- Clark, Xu, Forster, Wang and Andres, 2002. New small dinosaurs from the Upper Jurassic Shishugou Formation at Wucaiwan, Xinjiang, China. Journal of Vertebrate Paleontology. 22(3), 44A.

Choiniere, Clark, Xu and Forster, 2008. A new basal coelurosaur from the upper Shishugou Formation (Xinjiang, People's Republic of China). Journal of Vertebrate Paleontology. 28(3), 63A.

Choiniere, Clark, Forster and Xu, 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.


  1. Wait Tyranoraptoran? Never heard of that one before.

  2. Tyrannoraptora is the clade of Tyrannosaurus + Passer, named by Sereno.

  3. Tyrannoraptora is a clade name defined more than 10 years ago by Sereno for the "Tyrannosaurus + birds" node.

  4. Where is the supplementary info, including the phylo analysis? I can't seem to find it. Is the one that has Limusaurus as a basal ornithomimosaur?

  5. Tim- The supplementary info isn't on the website yet. I've asked Choiniere for a copy, and he said he'd forward it to me ASAP.

  6. Ah, so it was a wild goose chase. Thanks Mickey!

  7. So do reckon the reason Nqwebasaurus was excluded from the Zuolong phylo analysis was because the upcoming study will show Nqwebasaurus to be NOT a basal ceolurosaur, but something potentially more interesting...?

  8. I don't know about that. The Zuolong analysis (20 outgroups, 40 coelurosaurs, 472 characters) is said to be a reduced version of a larger theropod analysis, which sounds to me like the Limusaurus digital homology matrix (39 outgroups, 81 coelurosaurs, 517 characters). In that matrix, Nqwebasaurus emerged as a basal ornithomimosaur. In comparison, the Haplocheirus matrix did not include Nqwebasaurus and has 421 characters, 25 outgroups and 74 coelurosaurs. But I could be wrong, and the Zuolong matrix could be unique, in which case prior matrices give us no hint about where Choiniere places Nqwebasaurus.

  9. Sorry, I misread your comments. I thought you were saying than an analysis found Limusaurus to be a basal ornithomimosaur. :-) My mistake.

  10. My analysis places Zuolong as the basalmost coelurosaur.
    Mickey,could you please send me the Zuolong Supp. Infos when they're available? Thanks in advance.

  11. Oh it's this thing. I remember seeing the photo of Zuolongs skull years ago. I might even have the photo saved...somewhere.

    Mickey, Could you send me a copy of the paper and the supp. material?


  12. Zuolong's femur is shorter than the skull which is similar to Sinosauropteryx. Wow! It is the second theropod known to of had an upper leg bone smaller than the head.
    Maybe Zuolong forms a clade with Sinosauropteryx. It could be possible because of the short geographic distance between where both of the fossils where found.
    The only difference between the geography was that Zuolong salleei lived 30 millon years before it. Go Sinosauropterygini!

  13. There are other theropods with skulls longer than their femora- some Coelophysis, Ceratosaurus, Buitreraptor, etc.. Personally, I think ontogeny is to blame for the condition in Zuolong and probably Sinosauropteryx. Note the small Compsognathus has a skull longer than its femur, while the large one has the opposite proportions.