Mesobatrachia is the second largest of the Anurasuborders of amphibians. It has 6 families, 20 genera and 168 species. The name suggests they are moderately old.
Mesobatrachia are a newer group. They were identified in 1993.
References
Gissi, Carmela; San Mauro, Diego; Pesole, Graziano; Zardoya, Rafael (February 2006). "Mitochondrial phylogeny of Anura (Amphibia): A case study of congruent phylogenetic reconstruction using amino acid and nucleotide characters". Gene. 366 (2): 228–237. doi:10.1016/j.gene.2005.07.034. PMID16307849.