The Origin of Velociraptor and Citipati

I  rarely venture into the land of dinosaurs (except very basal forms). So many others are doing such great work. The field is saturated with information.

Here I take a single exception to look at a very well known reptile evolutionary lineage. Nothing new here. What I’m showing has been well documented by others and is quite obvious at first glance. All I can offer is to put several of the characters of this ‘play’ onto the same ‘stage’ for the first time.

The evolution of the oviraptorid, Citipati

Figure 1. The evolution of the oviraptorid, Citipati from Scipionyx and Incisivosaurus and a distinct separate lineage leading to Velociraptor determined by the phylogenies of others. When birds went right, these lines took a left turn and ended up with some Franken-birds, like Citipati and Gigantoraptor. Some of the above taxa are considered juveniles (with a short rostrum, large eyes, etc.). Even so, they point the way and provide the evolutionary method by which oviraptorids developed such strange skull proportions.

The present evolutionary sequence has not been tested in the large reptile tree. I’m going by the phylogenies of others (basically everybody in the biz) and the gradual morphological changes demonstrated by these five. Here, then, is a visual representation of the evolutionary sequence from Scipionyx (Dal Sasso and Signore 1998)  to Velociraptor (Osborn 1924)  through Bambiraptor (Burnham et al. 2000) and another branch to Citipati (Clark et al.  2001), an oviraptorid through Incisivosaurus (Xu et al.  2002).

From Scipionyx (considered a juvenile) up through Bambiraptor to Velociraptor, the rostrum elongates and the postorbital region shrinks. The orbit moves deeper into the second half of the skull. The teeth become recurved. The prefrontal become restricted to the the posterior of the lacrimal. The jugal becomes deeper. The mandible dorsal profile flattens. The premaxilla deepens. The quadratojugal develops a posterior process.

From Scipionyx down through Incisivosaurus to Citipati the premaxilla deepens and the naris rises. The jugal becomes more gracile. The maxilla shortens. The rise of the coronoid, the depth of the palate and the downturned posterior skull are all restricted to Citipati in this sequence.

This blog and illustration were modified from an earlier one demonstrating a morph from Velociraptor to Citipati, both from the Cretaceous. The obvious trick did not go over so well with one reader, so I’m making repairs here. Most DMListers love their velociraptors. Don’t want to piss anybody off.

Time is important and is always a consideration. Earlier forms, like Scipionyx, typically evolve into later forms, and that’s the case here. Exceptions include Huehuecuetzpalli, the Cretaceous sister to the ancestor of Triassic tritosaurs, for instance.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data. If I have made any mistakes, please provide data for the correction.

References
Burnham DA, Derstler KL, Currie PJ, Bakker RT, Zhou Z and Ostrom JH 2000. Remarkable new birdlike dinosaur (Theropoda: Maniraptora) from the Upper Cretaceous of Montana, University of Kansas Paleontological Contributions 13: 1-14.
Clark JM, Norell MA and Barsbold R 2001. Two new oviraptorids (Theropoda:Oviraptorosauria), upper Cretaceous Djadokhta Formation, Ukhaa Tolgod, Mongolia. Journal of Vertebrate Paleontology 21(2): 209-213., June 2001.
Dal Sasso C and Signore M 1998. Scipionyx samniticus (Saurischia, Theropoda): the first Italian dinosaur, Third European Workshop on Vertebrate Paleontology, Abstract: 2.
Osborn HF 1924a. Three new Theropoda, Protoceratops zone, central Mongolia. American Museum Novitates 144: 1–12. hdl:2246/3223
Xu X, Cheng YN, Wang X-L and Chang C-H 2002. An unusual oviraptorosaurian dinosaur from China. Nature, 419: 291-293.

wiki/Citipati
wiki/Velociraptor
wiki/Scipionyx
wiki/Incisivosaurus
wiki/Bambiraptor

10 thoughts on “The Origin of Velociraptor and Citipati

  1. If this is trying to imply an evolutionary chain that begins with the maniraptoran ancestor and leads to oviraptorids, that’s fine; but it seems you’re treating the derived conditions of Velociraptor mongoliensis as the antecedent to that of oviraptorids…. No. Just — no. You have to look at basal members, and Vel is not basal among Dromaeosauridae. Not by a long shot. Moreover, Scipionyx samniticus is basal to ALL of these in EVERY systematic analysis published with it to date, along with all sorts of other taxa. It’s also a juvenile, and one can say “it doesn’t count” on top of this.

    Also, are you implying with your tracing that all those discolored regions of the oviraptorid skull are distinct bones? Also — just no.

    • Based on my reading of the article David is suggesting that Scipionyx is basal, and that dromeosaurs evolved in one direction (up from Scipionyx in the illustration) while oviraptorids evolved in the other direction from Scipionyx (down in the illustration). So it is trying to show what you are critiquing…maybe just not in the clearest manner possible.

      • Yes, David clarified after my critique by altering the image, adding in the arrows. They were not there in the original. Usually, Dave uses clear arrows to try to demonstrate his models of progression, so it looked like he was describing the model of “raptor > Skippy > oviraptorid.” It should be further noted that there are other, better, basal maniraptoriforms that can be used to help underscore the model from which maniraptorans like “raptors” and “oviraptorids” evolve from, like Ornitholestes hermannii, or even adult “compsognathids” like the French specimen of Compsognathus longipes (described as corallestris). But when other maniraptorans, and even other coelurosaurs, show the “gracile” condition being described here as the trend toward “raptors” evolved as the basal condition for both “raptors” and “oviraptorids,” it puts this argument to the direct test. This can easily be tested by taking one of each of the most recent Senter, TWG, Cau analyses that have been published and map cranial morphology to them.

    • What do you mean? You’re citing papers that describe these things. For example, dal Sasso and Signore, and their later and much more detailed monograph, which also helps firmly establish the neonate (near hatchling) state of Scipionyx samniticus; the recent Dromaeosauridae monograph, which summarizes recent analyses from the TWG matrix to affirm the basal nature of “low-naris” taxa like Archaeopteryx lithographica and Microraptor zhaoianus in connection with the derived condition in “velociraptorines” when compared to even further “low-naris” taxa like all troodontids with the region preserved — this is available for free here.

      I’m also concerned about the seeming assumption that you’ve made in your tracing, that somehow Citipati osmolskae has teeth. Simply by using the figures and description provided in the osteology (Clark et al., 2002, also free here), and the wonderful resource that DigiMorph is (where the skull was CT scanned and can be examined in detail and in section, here), it should be immediately obvious that there are no teeth whatsoever. It should also be apparent that your tracing the caudoventral process of the dentary as if it were a splenial, also obviously incorrect by examination of these resources, should be an injunction against using these renderings so readily.

      Yes, oviraptorids have high nares in comparison to the total height of the skull, but there is NO CONTEXT provided for how you determine this, or to conflict with the actual argument you are making, that the subnarial “premaxillary body” is relatively “high” — proportional to its length/total length of the skull/height of the maxilla, or its length/total height of the skull as a given position?

      I also have a “minor” issue about being characterized as “loving their velociraptors,” as you put it; this is all about oviraptorids, when it comes to me, and about making clear arguments clear, with clear data and not “tracings” with some problems in their veracity.

  2. Jaime, you did well. Thank you. In this one, I was just taking a lark, curious but not too serious (no phylogenetic table), thinking that if I did a dinosaur or two, someone would come along and help out. That’s the spirit!

    No prefrontal on Citipati? Good grief!! Perhaps it has fused to what’s left of the nasal creating a nasoprefrontal.

    On the flip side, I have seen upside-down phylogenies, which this one clearly was originally, usually the result of too few taxa and no good ancestral outgroup.

    Finally, I wish to point out that when figures are provided with arrows pointing to bones, as in the Citipati paper, that does little to help understanding, especially in this case, when the sutures are occasionally cryptic. I hope you’ll join me in supporting the idea of producing an ink tracing to accompany the photo or a tonal overlay to illustrate the entire extent of each bone in future paleo papers, especially when the taxa are far from plesiomorphic!

    • Mark Norell once told me that one of the reasons he does not generally include line drawings or interpretive illustrations in his papers is that these are often used in lieu of the actual illustrations. The bones themselves should be doing the talking, and I agree. It is best, however, to permit viewers an interpretation, so long as it is clearly stated to be an interpretation. I do not pretend that the illustrations to papers that I produce which are done in ink are adequate replacements for the originals: they are accessory, and only that. They are certainly not a replacement for examination of the originals, and should never be used as data.

      Citipati osmolskae does, in fact, lack a distinct or separate prefrontal. It may have not ossified. One theory is that the prefrontal fuses to the posterior lachyrmal and forms the caudodorsal lachrymal process that extends on the frontal’s lateral margin. It is unlikely to have fused to any other bone, as the tracking of their development does not permit it: the prefrontal remains largely distinct from most other cranial bones but the lachrymal in any dinosaur, retaining more open contacts with other bones than with the lachyrmal. In dinosaurs, at least. Otherwise, the prefrontal appears to simply be reduced in size, never ossifies, or is lost (the condensate never develops into cartilage?).

      But that’s beside the point. The use of tracings to interpret bone shapes and sizes should never be the norm. Ever.

      • Respectfully, I disagree. We’re trying to impart an interpretation. Spelling it out with sutures removes any ambiguity. Then you can start seeing patterns in closely related taxa. Where does the prefrontal go? Does it shrink or fuse?

        Ambiguity is one reason why pterosaur palates are so poorly known by traditional paleontologists that it took a recent paper (Osi et al. 2010) to describe the fusion and near fusion of the ectopterygoid and palatine, something I noted working with Macrocnemus for the 2000 Rivista paper.

        Osi A, Prondvai E, Frey E and Pohl B 2010. New Interpretation of the Palate of Pterosaurs. The Anatomical Record 293: 243-258.

      • I can do this interpretation without having to present others a possibly misleading illustration. But let me note something: Never, ever, should an interpretive drawing take the place of the real thing, but even a photo of the material with labels is BETTER than an interpretive drawing.

  3. I have no issuie with the post, but it’s not just Citipati- Velociraptor, Bambiraptor and Incisivosaurus lack prefrontals too. Also Dal Sasso and Maganuco (2011) showed Scipionyx lacks an external mandibular fenestra.

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