The last phase of conodont evolution during the Late Triassic: Integrating biostratigraphic and phylogenetic approaches

For the Upper Triassic, conodonts are the primary tools utilized in biostratigraphic investigations. For an effective biostratigraphic zonation, the species should be constrained by clear phylogenetic relationships, in which the stratigraphic ranges and taxonomy are reliable. Unfortunately, a phylogenetic framework for the Late Triassic pectiniform conodonts is almost missing, except for particular intervals, such as the Carnian/Norian boundary. The purpose of this study is to examine the latest Norian and Rhaetian pectiniform conodonts in detail in an attempt to determine their phylogenetic relationships, by applying novel phylogenetic methodologies that incorporate both morphological and stratigraphic data. This work is based on the conodont assemblages from the Upper Triassic strata of the Lagonegro Basin (southern Apennines, southern Italy) and the Csovar area (north-central Hungary), complemented with data from the literature. The calibrated phylogenetic analysis of the latest Norian and Rhaetian conodonts supports a two-step evolutionary history: a first radiation (similar to 211-210 Ma) of the Parvigondolella species and the first representative of the genus Misikella, followed by a second phase (similar to 206.5-205 Ma) leading to the final radiation of the Misikella species. Furthermore, the systematic revision of uppermost Triassic conodonts is provided along with the description of Misikella kolarae n. sp.