What is "olsoniformes"

Olsoniformes is a clade of dissorophoid temnospondyls. It includes the families Dissorophidae and Trematopidae. Most members of the clade were highly adapted to a terrestrial lifestyle. The clade was named in 2008.

Trematopid olsoniforms are known from the Late Carboniferous of Europe and North America, while dissorophid olsoniforms are primarily found in Early Permian deposits in the central United States. The distribution of these two groups suggested that there were two radiations, first the trematopids throughout Euramerica and later the dissorophids through central North America. Recent finds of dissorophids from the Carboniferous–Permian boundary suggest that the family may diversified earlier than thought, lessening the gap between the two radiations.

Below is a cladogram from Anderson et al. (2008) showing the phylogenetic relations of Olsoniformes: