At some stage, I’ll have to write full-length articles on lysorophians, aïstopods, the remaining temnospondyls, nectrideans, microsaurs, and assorted other groups of Palaeozoic and Mesozoic non-amniote tetrapods. Alas, this hasn’t happened yet. In the meantime, here are some slides from one of my talks…
Lysorophians are peculiar, long-bodied lepospondyls from the Carboniferous and Permian, best known for Brachydectes. They had strongly reduced limbs and limb girdles and elongate skulls, typically with a strongly emarginated cheek region. Trace fossils suggest that some species were aquatic sidewinders (Braddy et al. 2003), and others seem to have aestivated at the bottom of burrows (Olson 1971). Lysorophians have been regarded by some authors as derived nectrideans allied to aïstopods, but others find them outside of a clade that includes nectrideans, aïstopods and others (Ruta et al. 2003)… sorry if all of these terms are new, but you at least know one nectridean as it’s featured in every single book ever on prehistoric animals: boomerang-headed Diplocaulus.
As for aïstopods, these are also long-bodied Carboniferous and Permian animals, imagined by some to be eel-like swimmers, and by others to be terrestrial and fossorial (the slide above says that they included both aquatic and terrestrial forms, but I’m not sure where I got that from. Has this issue been resolved yet?). Limbless and snake-like, they reduced and lost various of their skull bones over time, and some workers have suggested that they exhibited snake-like cranial kineticism (though this has been contested). So much more to say, of course.
For previous articles on Palaeozoic non-amniotes see…
- Temnospondyls the early years (part I)
- Temnospondyls the early years (part II)
- Crassigyrinus, or… How I’d love a giant killer Carboniferous tadpole for a pet
They are, clearly, horribly under-represented so far.
PS (added 22-6-2009): here is something I thought I’d never see. Wow, maybe people do love Palaeozoic non-amniote tetrapods after all…
Refs – –
Braddy, S. J., Morrissey, L. B. & Yates, A. M. 2003. Amphibian swimming traces from the Lower Permian of southern New Mexico. Palaeontology 46, 671-683.
Olson E. C. 1971. A skeleton of Lysorophus tricarinatus (Amphibia: Lepospondyli) from the Hennessey Formation (Permian) of Oklahoma. Journal of Paleontology 45, 443-449.
Ruta, M., Coates, M. I. & Quicke, D. L. J. 2003. Early tetrapod relationships revisited. Biological Reviews 78, 251-345.