Redescription of the two most recorded Physaloptera (Nematoda: Physalopteridae) parasitizing lizards in the Americas: first step towards a robust species identification framework.

Despite being the two most recorded species of Physaloptera from lizards in the Americas, P. retusa and P. lutzi are either incompletely described or have accumulated inaccurate morphological data through the years. Here, we redescribe both species from Tropidurus torquatus in the State of Minas Gerais, Brazil, including evaluation of specimens from the Coleção Helmintológica do Instituto Oswaldo Cruz. In P. retusa, the presence and location of amphids, presence and pattern of porous areas on pseudolabia, detailed pattern of cuticular ornamentations on ventral surface of the caudal bursa, structure of cloacal labia, presence of dome-shaped elevation between the last pair of postcloacal papillae and location of phasmids in males, were revealed for the first time. Additional morphometric data are also provided. In P. lutzi, the detailed morphological analysis revealed for the first time, porous areas on pseudolabia, as well as presence of amphids, phasmids, and the detailed ornamentation and papillae arrangement on the male bursa. Also, the presence of an internal tripartite and an external triangular labial tooth in the specimens were observed to be constant, diverging from the assertions by other authors. Finally, in P. lutzi was possible to observe that deirids are consistently located close to muscular oesophagus base with excretory pore slightly posterior to it, and the vulva is always close to anal aperture. The present observations confirmed the validity of P. lutzi and strengthened its taxonomic diagnosis. An up-to-date list of records of both species is provided, including a brief discussion on their host spectrum and geographic range.