Saturday, January 23, 2016

Dracoraptor thoughts

So the Welsh coelophysoid has been published, with the dudebro name of Dracoraptor.  There seems to have been a lack of rigorous editing, as exemplified by "Podekosaurus", Eshanosaurus being a therizinosaurid (as opposed to -oid or -ian), BMNH and NHMUK being used in the same sentence for specimens, and that's just the first two pages.  I also think the kind of title this paper has is silly ("The oldest Jurassic dinosaur") since it just specifies position within a known range.  It's like having "The smallest dinosaur under two meters long" or "the westernmost dinosaur found in China." Pluses are it's in open access and the photos are color with great resolution.

As for the actual description, there's a discrepancy in the elements that are shown in the skeletal reconstruction (fig. 5), listed under the holotype, listed at the beginning of each anatomical area, and actually described.  For instance, figure 5 shows a squamosal, angular and articular as preserved (and not just as molds or tentatively identified), which are listed under holotype.  Yet only "more caudal elements of the lower jaws" are listed under the cranial elements heading, and none of these elements are described.  But a ?nasal is described and figured, but not in figure 5 or noted in the cranial intro.  In total it seems more written by committee than cohesive.

Color figures- holotype of Dracoraptor hanigani (NMW 2015.5G.3) with: A- supposed manual ungual III, B- supposed manual ungual II, C- supposed manual ungual I, D- supposed furcula (after Martill et al., 2016).  Black and white figures from left to right- pedal unguals I and II of Coelophysis bauri NMMNH P-42200 (after Rinehart et al., 2009); pedal ungual II in dorsal view of Liliensternus liliensterni syntype MB.R.2175 (after Huene, 1934); metacarpal II of Coelophysis? rhodesiensis holotype QG 1 (after Galton, 1971); furcula of kayentakatae holotype MNA V2623 in dorsal and anterior views (after Tykoski et al., 2002); ninth dorsal rib of Allosaurus fragilis USNM 8367 (after Gilmore, 1920). Red lines indicate element identifications I propose for Dracoraptor.
Note the maxillae are in medial view, as the figure caption states, but contra the text.  Contra the text and reconstruction, only the small anteriormost jugal groove probably articulated with the maxilla.  The longer ridge and groove on the main body is common in early dinosaurs (e.g. Herrerasaurus) and non-articulating.  The supraoccipital is in anterior (internal) view, not ventral view as stated by the text.  Note the large posttemporal fenestrae as in Silesaurus but unlike dinosaurs. 

The cervical is not opisthocoelous, contra the text, as the anterior central surface is slightly concave.  The supposed first caudal is near certainly a ?last sacral based on the broad transverse processes originating on the centrum (compare to e.g. Staurikosaurus).  The authors do call it "a partially sacralised element", but any ambiguity seems unnecessary.  The next element could easily be a sacral too, though its more fragmented condition makes this more uncertain.  I'm doubtful the supposed furcula is correctly identified.  One side is much narrower than the other, and each is curved in a different direction (thin side concave toward the outside of the angle).  Furcular arms are subequal in width, and those of coelophysoids (e.g. kayentakatae) are basically circular in section, so that twisting in Dracoraptor is not an excuse.  It's more probably a posterior dorsal rib, which are also similar in having a ridge along the outside corner. The tuberculum may be covered in matrix. 

Amusingly, Martill et al. state that on the humerus "a suture between the articulatory epiphyseal surfaces is well defined."  And for the ulna, "the proximal condyle surface is smooth and well defined, marked from the diaphysis by a prominent suture."  Dinosaurs aren't mammals, people.  They don't have separately ossifying epiphyses.  For the femur, "the femoral head (greater trochanter) is "hooked'."  Er, those are very different structures, not synonyms.  The authors say "A calcaneum is not present. Two distal tarsals (dt III & dt IV) and part of a putative third are present in a row."  I'm pretty sure no archosauriforms actually have three distal tarsals per pes (certainly no theropods do), so that 'putative third' is more likely the supposedly missing calcaneum, especially as it's placed right next to distal tarsal IV (confusingly labeled 'Ldtii'). 

The supposed "?Metaacarpal of digit I" [sic] is a metacarpal II, very similar to rhodesiensis, more elongate than metacarpal I and more robust than metacarpal III.  Even Peters got this right in his reinterpretation, which is especially sad for Martill et al..  While I haven't identified all of the phalanges in this block, it's clear Martill et al.'s statement "they are assumed to be from the left manus as they are associated with the left radius and ulna" is in error.  For instance, the phalanx underlying the proximal radius is too large to belong to any manual digit and is probably pedal phalanx III-1, while supposed manual unguals I and III lack flexor tubercles ("I" shows an obvious depression in that area) and at least "III" is virtually straight.  These unguals more nearly match pedal unguals of e.g. Coelophysis and Liliensternus, while supposed ungual II is manual due to its curvature and large flexor tubercle.  Among other phalanges, that at the distal end of metacarpal II matches a manual phalanx II-1, that on the proximal end of metacarpal II belongs to manual digit III, that between unguals "I" and "II" looks like its from pedal digit II, and the small one by the anterior end of the dorsal centrum would be manual IV-1.  The latter suggests a less reduced digit IV than coelophysids or Herrerasaurus.  Thus the manual reconstruction with its short penultimate phalanges and metacarpal ratios should not be trusted.

The phylogenetic analysis is  based on Nesbitt et al.'s Tawa matrix.  One good thing is that Martill et al. split Nesbitt's composite characters, which had the effect of Nesbitt assuming non-homology for e.g. subnarial foramina in different positions, jugal ridges of varying sharpness, etc..  A negative point is that Martill et al. do not order any characters "because it assumes a complete fossil record and a direction to evolution."  But ordering does not assume these, it merely observes that some states are more similar to others.  So e.g. if a taxon has 5 premaxillary teeth, it's more similar to a taxon with 6 teeth than to one with 3 teeth.  Ironically, some of Martill et al.'s states imply ordering, such as their "6+ premaxillary teeth" state, which only makes sense if taxa with 6 teeth are more similar to taxa with 7, 8, etc. teeth than to those with less than six teeth.  They recover Dracoraptor as the basalmost coelophysoid, sister to Coelophysidae. I like how they note "an unnamed clade containing Velociraptor, Allosaurus and Piatnitzkysaurus."  Ah, you mean that obscure group called Tetanurae. ;)

Luckily for me, I have a version of Nesbitt et al.'s matrix on hand with characters properly ordered, and basically every basal dinosauriform added (as used in my Chilesaurus post).  I've also made a ton of corrections, though have by no means gone through the whole thing yet.  I did go through Martill et al.'s Dracoraptor codings though, and 15% are miscoded.  These range from consequences of my reidentifications above, to general errors (e.g. while coded as lacking a promaxillary fenestra, you can't tell that as the maxillae are in medial view), to times where I don't think the authors understood the character (e.g. it's coded as having an anterior hollow on the astragalus, but as used by Nesbitt this is a feature that has been lost in all avemetatarsalians).  After correcting Dracoraptor's codings, it emerges as sister to Neotheropoda (Ceratosauria+Tetanurae; Averostra of some authors).  But Neotheropoda has an odd topology where Chilesaurus is sister to Velociraptor, then Ceratosaurus, Piatnitzkysaurus and Allosaurus form a clade.  Because this makes the basal condition of Neotheropoda very different than the consensus, I deleted the highly modified Velociraptor.  Recall from the Chilesaurus post that Velociraptor only clades with Piatnitzkysaurus and Allosaurus in Nesbitt's uncorrected trees because it's miscoded for 24% of the characters that make it seem more like a "normal" theropod.  After Velociraptor's deletion Neotheropoda has the standard topology, and Dracoraptor is sister to a Daemonosaurus+Chilesaurus clade, which is itself sister to Avepoda (Neotheropoda of some authors).  This is rather like Cau's result, where Dracoraptor grouped with Daemonosaurus and Tawa.  In my trees, Tawa is the next taxon stemward.  Because Chilesaurus' basal theropod status is my pet theory and the taxon is also highly modified, I tried deleting it as well.  The result then is that Dracoraptor forms a polytomy with Tawa, Daemonosaurus, Coelophysidae and more derived theropods.

Thus it seems Cau's and my matrices agree in placing Dracoraptor by Daemonosaurus.  Note both share three premaxillary teeth (also in Chilesaurus and Tawa), short snouts with few maxillary teeth (also in Chilesaurus, not in Tawa), a lacrimal flange that does not overlap the antorbital fenestra (not in Tawa; unknown in Chilesaurus), and elongate cervicals with single pleurocoels (also in Tawa; elongate centra but double pleurocoels in Chilesaurus). 

References- Gilmore, 1920. Osteology of the carnivorous Dinosauria in the United States National Museum, with special reference to the genera Antrodemus (Allosaurus) and Ceratosaurus. Bulletin of the United States National Museum. 110, 1-154.

Huene, 1934. Ein neuer Coelurosaurier in der thüringischen Trias [A new coelurosaur in the Thuringian Trias]. Paläontologische Zeitschrift. 16(3/4), 145-170.

Galton, 1971. Manus movements of the coelurosaurian dinosaur Syntarsus and opposability of the theropod hallux. Arnoldia. 5(15), 1-8.

Tykoski, Forster, Rowe, Sampson and Munyikwa, 2002. A furcula in the coelophysid theropod Syntarsus. Journal of Vertebrate Paleontology. 22(3), 728-733.

Rinehart, Lucas, Heckert, Spielmann and Celeskey, 2009. The Paleobiology of Coelophysis bauri (Cope) from the Upper Triassic (Apachean) Whitaker quarry, New Mexico, with detailed analysis of a single quarry block. New Mexico Museum of Natural History and Science Bulletin. 45, 260 pp.

Martill, Vidovic, Howells and Nudds, 2016. The oldest Jurassic dinosaur: A basal neotheropod from the Hettangian of Great Britain. PLoS ONE. 11(1), e0145713.


  1. Lophostropheus and other theropods, are among the line of the Rhaetian and Hettangian. That makes Dracoraptor not have that record precisely.

    1. Well, it has the apparent record as the dinosaur dated precisely closest to the beginning of the Jurassic. Of course other less precisely dated taxa like Lophostropheus might have actually lived earlier in the Jurassic, but we don't know that yet.

  2. I agree in metacarpal re-identification: in fact, in my dataset I have avoided scoring mcI sensu Martill et al.

  3. the dudebro name

    LOL! It's funny because it's true :-D

    There seems to have been a lack of rigorous editing

    It shows that you haven't published in too long. :-) Of course there wasn't any editing. Most journals aren't copyedited; the Zool. J. Linn. Soc. published definately on the first page of a big paper in 2000 and never looked back. Few reviewers consider editing part of their job, so anything the authors don't happen to catch at the proof stage is published.

    PLOS journals don't even make page proofs. See my comment to my paper in PLOS ONE, grmpf.

    "the femoral head (greater trochanter)"

    That's disturbing!

    A negative point is that Martill et al. do not order any characters "because it assumes a complete fossil record and a direction to evolution." But ordering does not assume these

    Did they confuse ordering with polarizing???

    1. I meant editing in the sense of what a peer reviewer would do. Surely if I were peer reviewing this paper, I'd point out the errors above. More evidence we need to compensate our peer reviewers I suppose. Sad that PLoS journals don't make page proofs. Your comment there ( )certainly shows they should.

    2. Surely if I were peer reviewing this paper, I'd point out the errors above.

      I do that every time. Apparently, the two of us are simply not normal people; it's probably an autism-spectrum thing. Other people seem to think it's not their job, or even it might be construed as insulting to point out such things that should be self-evident – or they simply don't notice. I've often been praised for my "eagle eyes". *shrug*

    3. I should perhaps add that I don't have photographic memory or any such thing, and I am in fact capable of overlooking typos; I don't have a superpower in that department.

  4. Hi

    Thanks for putting this article together. It's very interesting and informative. I can't comment on the detail as I'm only an amateur and still learning but it raises some good points.

    Just out of interest, me and my brother do have more of the Dracoraptor material that wasn't included in the paper as it was found after the paper had been peer reviewed. Interesting, we also have resin casts (positive and negative) that we had made of the skull block before I got it prepped. This clearly shows the outline of the full maxillae and other bones such as the lachrymal, and you can easily put together a reconstruction of the skull. At some point I will get a model of the skull made.

    By the way, this is an excellent blog.

    Best Regards

    Nick Hanigan