Fresh off last week's blog on the "gluttonous face" Edops, we're hopping the pond and rolling into the "spoon lizard" Cochleosaurus! There is, unfortunately, no specimen with an anthropomorphic name as with "Grandpa Bumps," but what Cochleosaurus lacks in charismatic anthropomorphizing is made up for in the sweet, sweet sample size that includes a huge ontogenetic range, a rarity for Paleozoic temnospondyls.
Juvenile specimens of Cochleosaurus bohemicus (figures 1-2 from Milner & Sequeira, 2003). Cochleosaurus as a model of cochleosaurid ontogenyCochleosaurus is represented by the most specimens of any edopoid, which includes a pretty decent ontogenetic range with specimens of C. bohemicus with skulls less than 2 cm but ranging up to 24 cm. Some of the extensive junior synonymy associated with this taxon is related to the fairly drastic change in skull proportions over ontogeny. Above are two examples of juvenile C. bohemicus (Milner & Sequeira, 2003), one which was previously identified as an individual of the micromelerpetid Limnogyrinus, and another that is one of Fritsch's defunct Dendrerpeton species. The confusion over juveniles of large taxa and adults of small taxa is a particularly acute problem at Nýřany, which still has an unusually high diversity of temnospondyls, such as the trematopids Mattauschia and Mordex and the amphibamiforms Branchiosaurus and Platyrhinops. This has also historically caused problems for edopoid phylogeny because some taxa are only known from small specimens (e.g., Procochleosaurus from the Pennsylvanian of Ireland) or from large specimens (e.g., Nigerpeton). Postcranial ontogeny was described by Sequeira (2009), who noted fairly conserved temnospondyl developmental events such as ossification of the carpals and modifications to the pelvis but overall little changes over the course of ontogeny. The presumed aquatic tendencies of this taxon may have led to a degree of paedomorphosis that would have led to underdevelopment compared to terrestrial temnospondyls. What's special about Cochleosaurus?Tis unfortunate that there is no Grandpa Bumps equivalent of Cochleosaurus (or maybe it's written in Czech; I'm not sure). You may think that there is no way that Cochleosaurus can be as cool as Edops as a result, which is basically true; everybody knows that specimens with names are exponentially cooler. Nevertheless, don't sleep on Cochleosaurus! It's one of only two edopoids from Europe (the other being Procochleosaurus) and one of the earliest appearing members in what ends up being an exceptionally long-lived temnospondyl clade (early Pennsylvanian to late Permian). Also, because of its extensive sample size and ontogenetic range, anybody looking to examine comparative ontogeny or to do morphometrics has probably used Cochleosaurus not just as a representative edopoid but probably as a representative of the plesiomorphic temnospondyl condition altogether since most early temnospondyls have poorly constrained ontogenies (e.g., Witzmann et al., 2009; Pérez-Ben et al., 2019). The long and flat skull capture a morphology that then reappears in stereospondylomorphs much later down the road, and it could be argued to be the first semi-crocodilian like experimentation in temnospondyls (though archegosauroids are better for the long, tapering snouts), and because the contemporaneous Adamanterpeton and the preceding Procochleosaurus are only known from small individuals, it's unclear whether they had that long snout in adults. So there actually is quite a lot to like about Cochleosaurus, even if there is no story of serendipitous discovery behind a school in Texas! Up next week: Chenoprosopus Refs
David Marjanović
1/15/2020 11:39:04 am
"the Latin cochlear, which means 'spoon.'" Comments are closed.
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