In North America, we're blessed (or cursed, depending on how you look at it) with an abundance of the large-bodied metoposaurids, which grew over 2 meters as adults. But practically everywhere you look, particularly once you get past the Early Triassic and the recovery from the Permo-Triassic mass extinction, the temnospondyls are BIG. So it makes sense that we find lots of temnospondyls in Texas - everything's bigger in Texas, right? Wrong! Texas actually preserves some of the most interesting tiny temnospondyls, some of the smallest known from the entire Triassic period around the world. Featured this week are the two tiny temnos from Texas!
The current state of affairs
2000 seems not that long ago, but a lot happens in two decades! Unfortunately, not a lot's happened with either of these taxa... Both taxa are rarely analyzed in a phylogenetic matrix, but Schoch (2008) recovered both of them as closely related to each other and to metoposaurids (my favourite temnospondyls). This is based largely on Schoch's interpretation of the putative lateral exposure of the palatine as an unusually reduced lacrimal. The disparity in interpretations is a non-trivial distinction because concurrent loss of an independent lacrimal (presumably through fusion with another element) and presence of a lateral exposure of the palatine are rare features among Triassic temnospondyls, but more work is needed to clarify their relationships (i.e. CT). Outside of that, neither has been given much attention until Pardo et al.'s (2017) description of another tiny Triassic temno...
The intrigue of tiny temnos
So what's the deal with tiny temnospondyls? In Paleozoic times, there were numerous small rhachitomous temnospondyls, both on land and in the water (see amphibamiforms, for example). This changes in the Mesozoic, and particularly in the Triassic, temnospondyls were predominantly large, flat-skulled predators that roamed freshwater environments. This makes the rare small-bodied stereospondyls particularly interesting, especially because many of them are suggested to be terrestrial. Might this ecological divergence relate to something bigger? Regardless of which hypothesis regarding the origin of modern amphibians that you ascribe to, there's no questioning the fact that modern amphibians are much, much smaller than most temnospondyls, with size diminution (miniaturization) evidently playing a role in their evolutionary history. If you ask my friend Jason Pardo, small stereospondyls are intimately linked to caecilian origins, as exemplified in Rileymillerus and the recently described Chinlestegophis (which come out as sister taxa in their analysis) from the Late Triassic of Colorado (Pardo et al., 2017). More on that in future blog posts...
About the blog
A blog on all things temnospondyl written by someone who spends too much time thinking about them. Covers all aspects of temnospondyl paleobiology and ongoing research (not just mine).