Thursday, April 29, 2010

Non-Dinosaur News: Choristoderan Craziness

Above: Hyphalosaurus by Nobu Tamura. Licensed.

This might be the first post where I deviate from the title of my blog... but this was too good to let pass. As first reported by Jocelynn Falconnet on the DML, here are two new papers that just came out about Hyphalosaurus baitaigouensis (a small, long-necked aquatic choristoderan from the Jiufotang Formation) reproduction:

Ji Q., Wu X.-C. & Cheng Y.-N. 2010. Cretaceous choristoderan reptiles gave birth to live young. Naturwissenschaften 97(4): 423-428.
Viviparity (giving birth to live young) in fossil reptiles has been known only in a few marine groups: ichthyosaurs, pachypleurosaurs, and mosasaurs. Here, we report a pregnant specimen of the Early Cretaceous
Hyphalosaurus baitaigouensis...


Hou L.-H., Li P.-P., Ksepka D.T., Gao K.-Q. & Norell M.A. In press. Implications of flexible-shelled eggs in a Cretaceous choristoderan reptile. Proceedings of the Royal Society B 277(1685):1235-1239.
Flexible, or soft-shelled, eggs are almost unknown in the fossil record, leaving large gaps in our knowledge of the reproductive biology of many tetrapod clades. Here, we report two flexible-shelled eggs of the hyphalosaurid choristodere
Hyphalosaurus baitaigouensis from the Early Cretaceous of China, one containing an embryo and the second associated with a neonate.

To recap, Hou et al. have just reported that a specimen of H. baitaigouensis shows they gave birth to live young. Simultaneously, Ji et al. reported the discovery of unhatched H. baitaigouensis eggs.

I love paleontolgy ;)


  1. Very strange, I hope more light will be shed on this!

  2. This isn't the last you'll see of Mesozoic marine reptile vivipary. Expect another surprise in the next year and a half...

  3. My suspicion is that the Ji et al. specimen may have been about to lay thin-shelled eggs. But we'll see...

  4. I don't have access to the Hou et al. paper, but reading the Ji et al. one it looks like what they mean by "viviparity" is actually "ovoviviparity", which they don't consider a valid term anymore for whatever reason. The main contradiction seems to be on the presence or absence of shells. Ji et al. cite apparently shell-less eggs associated with the holotype, as well as this new find, to argue H. was well on its way to true viviparity and that the eggs never developed shells. The Hou paper just complicates this by showing that at least at some stage, the eggs did have thin shells, which were lost (re-absorbed or something? Not sure how this works) by the time of birth. It looks like it's pretty common for H. specimens to have discharged eggs/embryos post-mortem, so finding an isolated shelled egg isn't inconsistent with (ovo)viviparity.