Nesting Triceratops and its juvenile

Updated May 26 with suggestions from C. Collinson on skull sutures.
Updated again with a new reconstruction of the missing juvenile Triceratops face. 

No surprises here. 

Figure 1. Triceratops mount from an auction house. Pectoral girdle repaired. Skull colorized. Dorsal view comes from another specimen - always a dangerous proposition.

Figure 1. Triceratops mount from an auction house. Pectoral girdle repaired. Skull colorized. Dorsal view comes from another specimen – always a dangerous proposition.

Triceratops (Fig. 1, Marsh 1889) and its juvenile (Fig. 2) nest together with Yinlong downsi (Xu et al. 2006) Late Jurassic ~150 mya, ~1.2 m in length; Fig. 3) a primitive bipedal hornless pro-ceratopsian ornithischian, dinosaur, archosaur, archosauriform, archosauromorph, reptile. The large reptile tree is now up to 678 taxa.

Figure 2. Juvenile Triceratops compared to subadult Triceratops (in shadow).

Figure 2. Juvenile Triceratops compared to subadult Triceratops (in shadow).

A YouTube video, Dinosaurs Decoded, shows Mark Goodwin reassembling the juvenile Triceratops skull. Click here to watch.

Figure 2b. Original figure from Goodwin et al. of juvenile Triceratops, but mandible and squamosal scale bars don't match. Then compared to an adult. Then reconstructed based on new mandible/squamosal proportions based on text measurements. Evidently the juvenile Trike had a longer rostrum than Goodwin thought.

Figure 2b. Original figure from Goodwin et al. of juvenile Triceratops, but mandible and squamosal scale bars don’t match. Then compared to an adult. Then reconstructed based on new mandible/squamosal proportions based on text measurements. Evidently the juvenile Trike had a longer rostrum than Goodwin thought.

Liike all ornithischians, 
ceratopsians fuse the postfrontal to the frontal. However, in Yinlong, cracks (sutures?) appear where the postfrontal would have appeared and where the orbital horns ultimately appeared. So are the postorbital horns actually derived from postfrontal buds? We won’t know until we can determine a suture from a crack in the ontogenetically youngest and phylogenetically most primiitive specimens. It is also possible that, like the nasal horn, the orbital horns arose from novel ossificatiions that ultimately fused to the underlying bone.

Figure 3. Yinlong skull showing possible postfrontal in the position of the future orbit horns.

Figure 3. Yinlong skull showing possible postfrontal in the position of the future orbit horns.

Another juvenile nests with its adult counterpart!
Several workers and readers have pointed to studies (sorry, I don’t have the reference here) in which juveniles did NOT nest with adults in morphological analysis. Notably these samples  (as I recall…) came from taxa that metamorphosed during ontogeny, like caterpillars > butterflies and tadpoles > frogs.

In another argument, perhaps reflecting a majority view, a peerJ reviewer expressed concern/fear/trepidation that: – “Finally, I don’t know that a phylogenetic analysis including juvenile specimens alongside adult specimens is going to give you a particularly trustworthy result.“ citing no references, but noting that juvenile hadrosaurs have distinct characters in the skull from adults, which we all know.

Such arguments have been raised whenever I suggested workers include tiny Solnhofen pterosaurs in phylogenetic analyses, especially so since we KNOW that hatchling pterosaurs were virtual copies of adults. Not so with dinosaurs in which the rostrum is shorter and the orbits are larger than in adults. Even with that handicap, the differences, at least in this one case, were not enough to separate adult from juvenile Triceratops, given the present taxon list, which, frankly has no other ceratopsians.

References

Goodwin MB, Clemens WA, Horner JR and Padian K 2006. The smallest known Triceratops skull: new observations on ceratopsid cranial anatomy and ontogeny. Journal of Vertebrate Paleontology 26(1): 103-112.Lambe LM 1902. New genera and species from the Belly River Series (mid-Cretaceous), Geological Survey of Canada Contributions to Canadian Palaeontology 3(2):25-81
Marsh OC 1898. New species of Ceratopsia. Am J Sci, series 4 6: 92.
Xu X, Forster CA, Clark J M and Mo J 2006. A basal ceratopsian with transitional features from the Late Jurassic of northwestern China. Proceedings of the Royal Society B: Biological Sciences. First Cite Early Online Publishing. online pdf

 

wiki/Yinlong 
wiki/Triceratops

 

 

 

16 thoughts on “Nesting Triceratops and its juvenile

  1. Your Triceratops tracing bares numerous misinterpretations. The postorbital does not have a process like what you have traced in orange inserting itself between squamosal and parietal. In the juvenile you have coloured just a portion of the actual squamosal purple. In reality it should encompass much of what you have coloured in Tan as parietal. In fact, the parietal squamosal suture is quite obvious, as is the actual suture between the postorbital and squamosal. The jugal should also form the entire ventral margin of the orbit, not just the tiny portion you have depicted.

    Likewise, your Yinlong also has several misinterpretations. The squamosal, in purple, does not underlay the postorbital to form the dorsal margin of the fenestra. That should all be postorbital. And as for the post frontals… They are just cracks, as can be easily seen in numerous better images of the skull all over the internet. Why go with such a low resolution image?

    Furthermore, can’t you see how damning it is that DGS can not accurately render the anatomy of one of the most well understood well studied of prehistoric animals? How can you possible think that it could accurately render squashed and deformed specimens?

    • As an addendum towards what I wrote regarding your use of a low resolution image of Yinlong; the very .pdf that you link to at the end of your post has a much better quality image than what you have used. It clearly shows that you are wrong regarding the anatomy. What gives?

    • I have to echo Christopher here. Note how similar it is to my criticisms of your theropod misinterpretations. Also similar is the fact that the juvenile Triceratops specimen shown (UCMP 154452) doesn’t preserve the skull anterior to the orbit or the anterior mandibular tip, so any codings based on those are fictional. Much like with Ornitholestes, you can’t trust museum mounts without knowledge of the preserved material. The pdf describing the specimen is even free online- http://www.ucmp.berkeley.edu/people/mbg/Goodwin_et_al_2006.pdf .

      Finally, given the lack of similar taxa in your tree, juvenile and adult Triceratops grouping together is fairly meaningless. If e.g. Avaceratops or Zuniceratops were included, that would be a start.

      • There’s also the juvenile Chasmosaurus sp. just recently published. I’d be willing to bet that juvenile Triceratops would group with the juvenile Chasmosaurus and neither would group with its adult.

    • Thank you for your feedback, Chris, and sorry for the late reply. I have been under the weather. Please check the changes above to assure their validity. I know the delight one feels when a mistake is detected whether in one’s own work or another’s work. You do realize that every time I approach a taxon it is typically the first time I have ever done so and each time, therefore, I am a rank amateur, not an expert, when I make my marks. We’re all the same in this regard. It’s not the technique that is at fault here. Colorizing bones makes interpretations, whether right or wrong, easy to see. I count on those who know better to improve the interpretations, as you have done. I would caution you, as I have done with M. Mortimer and D. Naish, not to blackwash the entire effort based on a few errors. Those who do so lose credibility and reveal motives that are probably not appropriate for Science. The few score changes, as you probably realize, do not affect the tree topology at those nodes.

  2. David, as far as “blackwashing the entire effort” is concerned, as has been repeatedly pointed out to you, your fundamental error in position is your assumption of validity for any of your analyses in which specific errors have not been pointed out. Nobody, professional or amateur, is going to have the time or resources or inclination to double-check every single thing you’ve analyzed — all agree that you are amazingly prolific — and to assert “I correct all the errors that are pointed out to me, and all this stuff hasn’t had any errors pointed out, so it must be accurate” is simply fallacious. It presumes that checking has occurred that has not.

    • Squiddhartha’s quite correct. There are literally hundreds of things I see wrong with every theropod you use DGS on, but I have only so much time. If every theropod you reconstruct is so wrong (and they are), why are your turtles or ichthyosaurs any better?

      You say “every time I approach a taxon it is typically the first time I have ever done so and each time, therefore, I am a rank amateur, not an expert, when I make my marks. We’re all the same in this regard.”

      But we’re not the same, because you are the only one of us who by admission has no expertise in a group but then claims their results are correct. You criticize books like Hone’s and articles like Brusatte’s for not using your topology, but why should they pay attention to the findings of a “rank amateur” approaching a taxon for the first time? You can be either the untrained amateur who traces fossils without bias or knowledge in your subset of characters to see what happens, or the one person who has the analysis big enough to figure out the truth, but not both.

  3. You misquote me, Mickey. When you say ‘results’ you mean ‘observations’ and I have never claimed ALL my observations are correct. Just the opposite. I am always finding mistakes. And I appreciate the mistakes you all find. When the data comes in the form of photos and drawings of sometimes rebuilt incomplete taxa, that is bound to happen. Both Hone and Brusatte wrote before I dived into theropods. I tested their work and found it was less parsimonious. My rank, as a ‘rank amateur’ has a short shelf life as I learn and study the taxa. Same with you. Your ‘the truth’ as you know, is a rainbow we’re all chasing, but will never catch up to. I offer an alternate hypothesis that has fewer ‘aberrant’ clade members, more parsimony and a gradual accumulation of traits, rather than surprising leaps. And you can see that, but there’s a pecking order here and I understand that. Keep reporting corrections. Try to see the big picture. Understand that some corrections will cement rather than separate taxa. And, if you can, tell me which two taxa should not nest together.

  4. “Dorsal view comes from another specimen – always a dangerous proposition.”

    Even more dangerous when you realize that it’s not even an actual specimen of Triceratops, but a small scale model. A custom version of Kaiyodo’s DINOLAND 1:20 Triceratops, as remodeled by Brantworks.com. Were you aware?

    • No data is better than fake data. I mean seriously, you wouldn’t take measurements from a scale model plane and expect them to transfer into real life. Reconstructions are not data, they’re just simplified expressions of the data.

  5. Chris, I would take measurements from a scale model plane, just as I would take measurements from a scaled drawing of a fossil reconstructed in an academic publication. Sometimes I realize that such data has errors even though it comes from the highest, most respected sources. More examples coming soon. Until I do, though, that data is entered and que sera sera.

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