A new species of Sangiorgioichthys (Actinopterygii, Semionotiformes) from the Kalkschieferzone of Monte San Giorgio (Middle Triassic; Meride, Canton Ticino, Switzerland)

The genus Sangiorgioichthys is one of the few Semionotidae known from the Middle Triassic. The type species S. aldae Tintori & Lombardo, 2007 has been found in Late Ladinian marine deposits of both the Italian and Swiss sides of Monte San Giorgio. A second species, S. sui López-Arbarello et al., 2011 described from the Pelsonian (Middle Anisian) of Luoping (Yunnan, South China) has extended the range of the genus both in time and space. A further species of Sangiorgioichthys, Sangiorgioichthys valmarensis n. sp., is described herein from the Late Ladinian Kalkschieferzone (Meride Limestone) of the Monte San Giorgio area, the same unit yielding the type species. Sangiorgioichthys valmarensis n. sp. differs from the already known species in number and arrangement of suborbitals, shape of the teeth and in shape and row number of the scales. The new species of Sangiorgioichthys increases the diversity of Semionotidae already in the Middle Triassic, indicating that the explosive radiation of Semionotidae during the Norian was preceded by a first phase of diversification during the Middle Triassic.