Dinosaur tail length bonus data

Happily for me I have been contacted by several colleagues in the wake of my last post pointing me to the specimens and papers that I’d either missed or have come out too recently for me to have included in the tails paper. More happily still a couple of them are really interesting and so worth sticking up here. Remember that I’d been scaling the length of the tail against the femur as a proxy for body size with most values being around 3-4 (i.e. the tail was 3 or 4 times the length of the femur) with the very shortest clocking in at just 1.2 or 1.3 and the highest at 8.8.

First off, Jordan Mallon pointed me to a paper of his describing a chasmosaurine with a complete tail that clocks in at just 1.9. The next lowest value I had for any ceratopsid was 2.8 so this is a quite a big drop and this is the same as Nomingia which I think is fair to call a very short-tailed oviraptorosaur. So there’s at least one more shorty out there.

I’ve also been mailed by Matthew Herne who’s working on Leaellynasaura and given me permission to publish this nugget of data here before his full description makes it into the literature. Now Leaellynasaura did get a mention in the paper as being a possible outlier with a long tail based on an SVP abstract by Matthew, but obviously without the actual data I had no idea just how low this might be. Well, as I say, he’s mailed in the result and it’s a truly whopping 12.4! It’s tail was more than 12 times the length of it’s femur. Wow.

10 Responses to “Dinosaur tail length bonus data”

  1. 1 Mickey Mortimer 30/08/2012 at 8:13 am

    Also fitting your requirements among theropods-

    Dilophosaurus’ holotype preserves 44 caudals and Welles (1984) added three to the reconstruction.

    Coelophysis bauri skeleton NMMNH P-44552 has approximately 41 (Rinehart et al., 2009). There must be complete caudal series in the Ghost Ranch blocks.

    Megapnosaurus rhodesiensis preserves 38 caudals with a gap for two (Raath, 1969).

    Ceratosaurus nasicornis preserves 50 caudals, with one to a few missing at the tip (Gilmore, 1920).

    Sinocalliopteryx has 49 caudals (Ji et al., 2007).

    For Sinosauropteryx, you quote Currie and Chen (2001) on the referred specimens lacking their distal tails, but the holotype preserves 59 caudals, with five lost in a mid section.

    Nothronychus? graffami preserves 23 caudals with only a few distalmost ones missing (Zanno et al., 2009).

    While you mention the partial holotype, the specimens of Similicaudipteryx described by Xu et al. (2010) have complete tails.

    Citipati sp. IGM 100/42 has thirty caudals with one missing at most. Rinchenia, Khaan and “Ingenia” also have basically complete tails.

    There’s ?Sinornithosaurus NGMC 91 with a complete tail (Ji et al., 2001).

    Tianyuraptor’s is missing only a few (Zheng et al., 2009).

    Velociraptor IGM 100/25 has a complete tail, no?

    Sinusonasus’ tail is complete to the tip (Xu and Wang, 2004).

    • 2 David Hone 30/08/2012 at 8:31 am

      The problem with at least some of these is, as you say, they’re listed as ‘basically complete’ or ‘nearly complete’ or ‘only a few missing’. The problem is that between things like Nomingia that terminate very suddenly and Diplodocus and Sinosauropteryx that have sections with almost no reduction in caudal size (i.e. there’s no tapering) I’m very suspicious of anything that doesn’t have a truly complete tail. I made a couple of exceptions where the space for the missing piece was on the block (i.e. there was an impression in the matrix or an obvious gap in an otherwise perfectly continuous sequence).

      Something like Tianyuraptor though I looked at and decided against using, for me there’s just no guarantee without much better knowledge of how tails taper and change that there’s only 2 caudals missing and not 10 say which would make a difference. Saying things like ‘one or two only are missing’ I think is trapping yourself with the very assumption you’re trying to test – just how much is missing or may be missing. There’s a good few of these I’d looked at the papers or even the specimens and rejected as incomplete or lacking the data in the description to be confident they were complete.

      Far too many are described as ‘complete’ but when you look the terminal caudal just isn’t there. Alternatively there just isn’t the information to tell without firsthand access to the material (Raptorex appears to be complete but the paper never says if the last caudal is there) and oddly I don’t have the money or time to chase down every specimen in every museum. So I am specifically relying on things where the paper explicitly states or demonstrates (with a nice close-up) that every single caudal is there. I’ve now been pointed to the New Mexico report on Coelophysis which does make this statement about two specimens, but in Colbert’s monograph he talks about tails being nearly complete or effectively complete and variation in caudal series but without ever actually saying something as simple as ‘there is an unbroken series of 41 caudals and the terminal caudal is present’.

      • 3 Mickey Mortimer 30/08/2012 at 9:07 am

        Colbert’s paper sucks in the description department, as usual. 😉 I agree that Dilophosaurus, Ceratosaurus, ?Nothronychus, Rinchenia and Tianyuraptor have some amount of missing distal caudals. Those of Velociraptor, Citipati and “Ingenia” look complete, but I don’t have high resolution pictures of the area.

        Yet I included these because they are at least as complete as some taxa you did include. Deinonychus preserves one series of 23 caudals with an unknown number more proximal, and overlaps with three series showing at least 11 more caudals were present distally, but with an unknown amount more distal (Ostrom only says one includes “what appears to be the penultimate segment”).

        Neimongosaurus preserves 22 caudals with an unknown amount distal to it. That’s just as bad as Tianyuraptor.

        Btw, Gallimimus specimen ZPAL MgD-I/1 has a complete series of 36 caudals. So that’s an additional taxon that shows individual variation in caudal number, as the holotype has 38.

        Bbtw, Raptorex preserves only the first eleven caudals. As the authors say “… lacking portions of the forelimb and the distal one-half of the tail (beyond the eleventh caudal).”

      • 4 David Hone 30/08/2012 at 5:23 pm

        Well Deinonychus I corrected for using other specimens in Ostrom’s dataset (as noted in the paper). It’s not great but there was enough overlapping material that he had looked at closely that I felt it was acceptable in the circumstances, if far from ideal.

        Oddly I saw Raptorex in Japan (though glass) but without the description handy and the tail looked complete to the tip, but the sculpted and replaced parts were near impossible to distinguish from the real stuff hence my not being sure what might be there.

  2. 5 Jaime A. Headden 30/08/2012 at 11:01 am

    There is no reason to doubt the completeness of some of the oviraptorosaur caudal series. In MPC-D 100/119 – Nomingia gobiensis – the caudal series is complete. The doubt arises only in the “sudden termination,” which is comprised first of a gradual reduction in caudal length towards an abrupt decline, to a point where each successive caudal is less than half the length of the previous, until there is as tiny nubbin of bone left. It is thus presumed that this is “complete.” In BPM 0001, referred to Caudipteryx zoui, and NGMC 97 9 A (paratype), the caudal vertebrae are very similar despite overall more gracile, and exhibit an abrupt termination in which the final three or so caudals are “truncated.” This condition is present albeit in more gradual form in at least some oviraptorid caudal vertebrae, as indicated by Barsbold et al., on describing the pygostyle of Nomingia gobiensis in the first place. A second pygostyle is mentioned for the latter by Currie (2002). There should be no doubt about the completeness of these specimens, specifically.

    Barsbold R., Currie, P. J. Myhrvold, N., Osmólska, H., Tsogtbaatar K. & Watabe M. 2000. A pygostyle from a non-avian theropod. Nature 403:156-156.
    Currie, P. J. 2002. Report on fieldwork in Mongolia, September 2001. pp.-12 in Alberta Palaeontological Society, sixth annual symposium, “Fossils 2002’, presented by Alberta Paleontological Society, in conjunction with Canadian Society of Petroleum Geologists, Paleontological Division and Department of Earth Sciences, Mount Royal College.

  3. 8 Jordan 30/08/2012 at 1:26 pm

    It was a chasmosaurine. 😉

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