Thursday, October 7, 2010

"The Princeton Field Guide to Dinosaurs - The Theropods

Having reviewed Paul's new book in the last post, this one will examine the good, bad and just plain interesting things it has to say about theropods.  It's organized in the order Paul discusses the taxa.

The seemingly rigorous Staurikosaurus skeletal includes anterior cervicals, chevrons, the whole pectoral girdle, a humerus and pes.

The coelophysoids have meager descriptions as with most taxa, but most every skulless one (Procompsognathus, Podokesaurus, Gojirasaurus, Liliensternus, Segisaurus, but not Lophostropheus) contains the phrase "not known whether head crests were present."  This is repetitive (it would be simpler to say only Megapnosaurus and Coelophysis are known to LACK crests) and you would think there's more useful information the space could be spent on, like Gojirasaurus being a chimaera, Procompsognathus being perhaps nondinosaurian and with a controversial skull, Segisaurus being thought to have solid bones and unfused clavicles until recently, etc..

Among abelisaurs, the Rahiolisaurus skeleton is labeled Indosuchus and seems to just be reposed from Chatterjee and Rudra's schematic drawing (which is now known to be wrong in various ways thanks to the description).  A complete skull is illustrated and listed for Rajasaurus, but while there is a cast that's often photographed, only a braincase is present according to the description.  For those curious why Aucasaurus is sunk into Abelisaurus- "the only reason this does not appear to be a juvenile A. comahuensis is that fusion of skeletal elements suggests it is an adult."  It should be noted Paul has an odd phylogeny where ceratosaurids and elaphrosaurs are closer to tetanurines than abelisauroids are. The seemingly rigorous Elaphrosaurus skeletal incorrectly has a complete vertebral column, all chevrons (only one is preserved) and complete pes, but doesn't include the scapulocoracoid or metacarpals.

Poekilopleuron bucklandii being the same genus and/or species as Megalosaurus bucklandii might have been a viable idea back in 1988, but not now that both have been redescribed.  Another odd aspect to Paul's phylogeny is that Piatnitzkysaurus, Condorraptor, Magnosaurus, Eustreptospondylus (as Streptospondylus) and Afrovenator are avetheropods.  The rationale for sinking Eustreptospondylus- "Eustreptospondylus oxoniensis is tentatively placed in Streptospondylus altdorfensis."  Eustreptospondylus' skeletal is odd in lacking most of the skull besides the premaxilla, maxilla and quadrate, but a lot of what is shown is not preserved (ribs, most caudal vertebrae, chevrons, etc.).

Sinraptor hepingensis is synonymized with Yangchuanosaurus shangyouensis, but S. dongi (with a humerus and coracoid in its rigorous skeletal) is kept separate.  Monolophosaurus and Guanlong are both sinraptorids, which has never been supported to my knowledge.  Paul retains the old short snout vs. long snout Allosaurus dichotomy which Chure has showed is untrue.  For Neovenator, he states "That researchers have disagreed whether this is a basal tyrannosauroid or an allosauroid suggests these groups may be more closely related than thought."  But whoever proposed Neovenator is a tyrannosauroid?

For Coelurosauria, Paul states "The validity of the group is not certain."  But who has ever had a theropod phylogeny without it? While I do applaud Paul's indicating when taxa are based on juvenile specimens, he's incorrect in calling the heavily fused Bagaraatan type a juvenile and the young Raptorex type an adult.  On the other hand, I was happy to see him call both Alioramus species juveniles and probably synonymous.  One new combination missing in my taxonomy post is "Appalachiosaurus (or Albertosaurus) montgomeriensis."  Using Carr's data, that seems fine as long as Bistahieversor is Albertosaurus too.

Paul lumps all American ornithomimids into Struthiomimus, but says Struthiomimus? sedens "includes Ornithomimus velox, which is based on entirely inadequate remains."  GAK!!!  Impossible.  Ornithomimus and the species velox have priority over Struthiomimus and sedens.  If Ornithomimus' syntypes are entirely inadequate (and they're not), it couldn't be assigned to the same species as sedens

The rigorous Ornitholestes skeletal lacks any forearm or manus material (even though the famous manus has been reassigned to Tanycolagreus, the holotype has manus material as well).  Scansoriopteryx is used instead of Epidendrosaurus, which is nice.  Yet the taxon is not placed with Epidexipteryx, as the latter is assigned to Oviraptorosauria instead.  Wherever the taxa belong, their morphology is so similar that they may even be synonymous.  If Paul would have used all the manual phalanges in Epidexipteryx, he would have found it impossible to restore with normal hands.

Shanag is sunk into Sinornithosaurus because "Too little is known to distinguish this from Sinornithosaurus."  Tsaagan and Graciliraptor don't even get that much explanation.  Deinonychus' skeletal is oddly incomplete (no scapula, humerus, ilium, pubis, femur, tibia or fibula), which I'm assuming is due to Paul's statement Lower Cloverly remains "are probably one or more different taxa."

The oviraptorosaurs are all given bifurcated tail fans, but Gatesy (2001) showed this was an illusion in Caudipteryx.  Both Epidexipteryx and omnivoropterygids are placed in Oviraptorosauria, which has never been supported by an analysis, but I do like that Paul uses Omnivoropterygidae instead of Sapeornithidae.  The caenagnathid taxonomy is highly confused.  Using Paul's names, it consists of- Caenagnathus collinsi (only the type mandible), Caenagnathus? sp. (the two undescribed Triebold skeletons), Chirostenotes pergracilis (said to possibly include elegans), Chirostenotes? sp. (the specimen described in Sues, 1997), and Elmisaurus (or Chirostenotes) rarus.  Where to begin?  The Triebold skeletons combine Caenagnathus jaws with Chirostenotes postcrania, so there's no reason to keep the genera separate, let alone refer the Triebold material to one genus or the other.  elegans is more similar to Elmisaurus despite the undefended assertions of some recent papers (Sues, 1997; Maryanska et al., 2002; Osmolska et al., 2004).  The Horseshoe Canyon specimen described by Sues has never been suggested to belong to a distinct taxon in the literature, and was seemingly just separated based on stratigraphy.  Shanyangosaurus is listed as a caenagnathid, which I find amusing since I suggested it was an oviraptorosaur back in 2000, that was also followed by Holtz et al. (2004).  Ironically, I no longer think my analysis was sufficient to place it anywhere specific within Maniraptora.

Oviraptorids themselves were lumped a lot. For Citipati osmolskae, Paul says "It is probable that crestless Khaan mckennai is the juvenile form of this species."  And for "Conchoraptor (or Citipati) gracilis", he says "It is probable that all specimens from this formation are juveniles and adults of one species whose taxonomy is complicated because the genus portion of the original name Ingenia yanshini turned out to be preoccupied by an invertebrate."  But as I noted before, just because Ingenia is preoccupied doesn't mean yanshini wouldn't still be the species name.  Nor can Conchoraptor gracilis ever be Citipati gracilis, since Conchoraptor has priority over Citipati.  His illustration for this conglomerate of taxa is basically "Ingenia" but with that privately owned skull with the very tall pointed crest.  I do like that Paul illustrates the internal nostrils on the side of the ventrally projected palate in oviraptorids.

The reconstruction of Beipiaosaurus uses the new anterior skeleton and features a silly-looking vaguely stegosaur-like skull with a pointy snout.  Contra to Paul who thinks Nothronychus graffami (mistyped grafmani) might be synonymous with N. mckinleyi, I'm doubtful they're even congeneric.

Next up, sauropodomorphs...


  1. A mistake that I find is that it appears less Cryolophosaurus Dilophosaurus size when in fact it could be true. The incomplete femur reaches over 759 mm, well above the higher of the Dilophosaurus that may reach only about 628 mm.

  2. Speaking of synonymies, which are the rigorous reasons why synomymizied Yangchuanosaurus shangyouensis with Yangchuanosaurus magnus?

  3. With Yangchuanosaurus, I'm just following convention so far.

    Another fun thing about the Field Guide I noticed yesterday- Paul mistook Sereno et al.'s (1998) illustration of repositioned Baryonyx skull elements attached to Cristatusaurus' jaws as being actual bones known from Cristatusaurus (his Baryonyx tenerensis).

  4. Which convention?
    Holtz (1998), Chure (1998), Averianov, Martin & Bakirov (2005), Carrano (2006), Senter (2006), Xu & Clark (2008), Wu et al (2009), Brusatte, Benson & Xu (2010) and Han et al (2011) all considered Y. shangyouensis and Y. magnus to be 2 different species

  5. Please reply, mr Mortimer. I really wanna to know

  6. Oops, your prior comment fell down the email hole.

    I was thinking of Rauhut (2003) who stated "Although all of the taxa included in the Sinraptoridae have been described as separate species, their morphology seems to be almost identical, as far as can be judged from published accounts (DONG et al. 1983, GAO 1992, CURRIE & ZHAO 1993a). Since both species of Yangchuanosaurus and Sinraptor hepingensis are also from the same formation, it seems likely that all the specimens represent only one species."

    Similarly, Holtz et al. (2004) stated "It is not at all apparent that these are simply two different growth stages of the same species, with "Y. magnus" an older individual."

    Incidentally, the characters supposedly distinguishing magnus from shangyouensis are (Dong et al., 1983)-
    - magnus is larger.
    - one of the maxillary fossae of magnus penetrates (Dong et al. don't specify which), but pneumatic variation is well known within and between individuals of the same species.
    - magnus lacks a foramen at the base of the posterodorsal dentary process.
    - magnus doesn't have shangyouensis' oddly tapered preacetabular process.

    Note neither specimen has been reexamined since the 80s, so I don't put much trust in the reality of these differences. Maybe shangyouensis' ilium was damaged, maybe the maxillary fossa would penetrate given further preparation or maybe magnus' was prepared too much. But even if the differences are real, they're comparable to individual variation in other taxa. Archaeopteryx individuals vary in preacetabular expansion, Dromiceiomimus individuals vary in mandibular foramina possession.

    So at the moment, I'm happy keeping them synonymous. But maybe restudy will show more differences, or maybe Rauhut's right and at least some Sinraptor species are Y. shangyouensis too. Gao's retained hepingensis in Yangchuanosaurus, regardless of what Currie and Zhao wrote afer all. Just one of the many things someone needs to work on...

  7. Many thanks for your info

  8. It looks like Bagaraatan is indeed a juvenile going by the new paper.

    1. Well, Słowiak et al. (2024) found the tyrannosauroid parts were juvenile, but the caenagnathid parts (such as the fused tibiotarsus I had in mind) were adult, as also shown by their histological description of the femur with its secondary osteons and resorption cavities.