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Temporal range: Late Carboniferous - Late Permian
Acheloma cumminsi.jpg
Skeleton of Acheloma cumminsi
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Order: Temnospondyli
Superfamily: Dissorophoidea
Clade: Olsoniformes
Anderson et al., 2008

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.[1]

Below is a cladogram from Anderson et al. (2008) showing the phylogenetic relations of Olsoniformes:[2]




Ecolsonia cutlerensis





  1. ^ May, W.; Huttenlocker, A.K.; Pardoc, J.D.; Bencab, J.; Small, B.J. (2011). "New Upper Pennsylvanian armored dissorophid records (Temnospondyli, Dissorophoidea) from the U.S. midcontinent and the stratigraphic distributions of dissorophids". Journal of Vertebrate Paleontology. 31 (4): 907–912. doi:10.1080/02724634.2011.582532. 
  2. ^ Jason S. Anderson; Amy C. Henrici; Stuart S. Sumida; Thomas Martens & David S. Berman (2008). "Georgenthalia clavinasica, A New Genus and Species of Dissorophoid Temnospondyl from the Early Permian of Germany, and the Relationships of the Family Amphibamidae". Journal of Vertebrate Paleontology. 28 (1): 61–75. doi:10.1671/0272-4634(2008)28[61:GCANGA]2.0.CO;2.