Caudal vertebrae of Haplocanthosaurus delfsi

August 12, 2018

Tired of Haplo caudals yet? No? Good – me neither. Not by a long shot.

Above is McIntosh and Williams (1988: fig. 10) showing the rearticulated and partially reconstructed tail of CMNH 10380, the holotype and only known specimen of Haplocanthosaurus delfsi, in right anterolateral oblique view. It’s not an original, I plucked it from a PDF scan of the paper. Probably an original reprint would be a lot more clear. In hopes of seeing more, I cropped out the background and tweaked the contrast:

The first 14 caudals are real, the rest are sculpted replicas. You can tell in the photo because the thickness of the supporting rods drops sharply between caudals 14 and 15. That’s not my original observation, McIntosh and Williams pointed it out.

Conclusion? It looks like a pretty good Haplo tail. The first caudal has big, plate-like caudal ribs, which grade rapidly into the normal laterally-projecting stumps in succeeding vertebrae. Caudal 1 also has a distinctly tall, backwardly-curved neural spine, which grades into shorter, straighter spines very rapidly as well. It’s as if the first caudal is built on a typical diplodocoid plan, but the rest are simple non-neosauropod or basal macronarian caudals and they have to switch over as quickly as possible. Both of those shifts happen in the first few caudals in the other Haplo tails, too, with some minor variation among specimens.

I’m sure I’ll have more to say about this specimen in the future, but I’m attending the Flugsaurier conference in LA this weekend so my head is in the clouds. Hope you’re having half as much fun.

Reference

  • McIntosh, J.S., and Williams, M. E. 1988. A new species of sauropod dinosaur, Haplocanthosaurus delfsi sp. nov., form the Upper Jurassic Morrison Fm. of Colorado. Kirtlandia 43:3-26.
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3 Responses to “Caudal vertebrae of Haplocanthosaurus delfsi

  1. Mike Taylor Says:

    “It’s as if the first caudal is built on a typical diplodocoid plan, but the rest are simple non-neosauropod or basal macronarian caudals and they have to switch over as quickly as possible.”

    I would have put this the other way around. After the big split at the base of Neosauropoda, one group was trying to evolve into diplodocids as quickly as it good. Haplocanthosaurus got to that game early, and started doing it from the ass backwards. The diplodocoidification proceeded caudally from there.

  2. Matt Wedel Says:

    Yup, that’s a better way of putting it. Like Haplo was trying to get its diplodocoid suit on, but only managed to get the first caudal all diplo-ed up. Total Friday job, worth exactly one lousy node of diplodocoideation.

    Still better than one node of macronariannnnnope. I’m looking at you, Camarasaurus!

    Just kidding, Cam. No-one is looking at you.

  3. Mike Taylor Says:

    Two good solid LLOLs in one comment, there.


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