The egg-brooding frogs Fritziana Mello-Leitão, 1937 and Flectonotus Miranda-Ribeiro, 1926 (Amphibia: Anura): osteology and putative synapomorphies for hemiphractid frogs

Despite the importance of osteological characters in the diagnoses of the hemiphractid genera Fritziana and Flectonotus mentioned in the literature, published information on the osteology of both genera has been limited to the shape description of a few skull bones, such as nasals, quadratojugals, and neopalatines. Herein, detailed cranial osteological descriptions of six species of Fritziana and two of Flectonotus are provided with comparisons to those of other hemiphractid genera. The osteology of species of Fritziana is described with an osteological diagnosis for each species. The genera are distinguished from all other hemiphractid frogs by the following combination of cranial features: short quadratojugal not articulating with the maxilla; short squamosal zygomatic ramus not articulating with maxilla; and frontoparietal fontanelle partially exposed. The species of Fritziana and Flectonotus are distinguished from one another by the relative sizes and shapes of the nasals and frontoparietals, and the position of the posterior terminus of the parasphenoid. We also suggest six putative synapomorphies, two for Fritziana and four for Flectonotus. In Fritziana the quadratojugal does not articulate with the maxilla and the omosternum is oval-shaped. In Flectonotus, the anterior margin of the vomer is not in contact with either the maxilla or premaxilla, the small, narrow nasals overlie the nasal capsule flanking the sphenethmoid, and the frontoparietals are narrowly separated medially. The quadratojugal does not articulate with the maxilla in either genus and is slightly longer in Flectonotus than in Fritziana.