Amphibians stand apart from all other vertebrates in their great range of genome sizes. They are largest in the salamanders, where genomes are huge (over 100 gigabases), but genomes of some frogs enter the salamander range and can be quite large (the largest reported is in the myobatrachid frog Arenophryne rotunda). Caecilians are somewhat intermediate. The smallest amphibian genomes are also found in myobatrachid frogs. Lamichhaney et al. (2021) reports on the genome of Platyplectrum ornatum, a small burrowing frog from Australia with a very small genome - 1.05 Gb, like that of birds. Transposable elements (TE) account for much of the extreme growth of amphibian genomes, but here all major classes of TE are reduced. Keeping TE's in check appears to be a key to genome miniaturization, and it may be driven by convergence in life history in small-genomed species, in particular, rapid and flexible tadpole developmental time and carnivorous tadpoles. Phylogenetic analysis shows that the genome is evolutionarily reduced rather than being a primary feature of this taxon.
