What's a dissorophid?
To kick off this thematic series of blog posts, we first have to discuss what a dissorophid is. Dissorophids are part of a clade called Dissorophoidea. It's very easy to mix up 'dissorophid' and 'dissorophoid,' including when you've added both of them to your computer's dictionary. Usually what I tell people is that 'dissorophoid' has more letters, so it is the more inclusive (more all-encompassing) taxonomic group. Dissorophids show up in the fossil record in the Late Carboniferous when temnospondyls start really taking off (along with other tetrapod groups). They stick around until the late Permian, but they really hit their peak in the early Permian of North America - they're pretty sparse in other places for some reason. One of their most distinctive features (among other things), is the presence of osteoderms (bony armour plates) along the backbone. This isn't necessarily protective armour in the same way that some other animals have very extensive coverings for protection (e.g., crocs, ankylosaur dinosaurs), and some work (Dilkes & Brown, 2007; Dilkes, 2009) has suggested that based on the association with only the backbone, dissorophid armour was for stiffening the backbone to prevent too much swaying when walking (inefficient on land). Osteoderms are very diverse among dissorophids, a theme that I'll revisit throughout this topical series. Dissorophids were definitely terrestrial (the total opposite of my favourite metoposaurids) and probably ran around terrorizing smaller tetrapods. Dissorophids aren't gigantic - most of them had skulls in the 5-10 cm range, which would put their bodies around 15-40 cm - but that's still larger than a lot of modern amphibians!