North American Spathian (upper Olenekian, Lower Triassic) neogondolellin conodonts

Abstract

AbstractThe taxonomy and biostratigraphy of poorly known neogondolellin conodonts from mostly Spathian (upper Olenekian, Lower Triassic) strata are described from widespread localities in North America: high latitude Canadian Arctic, mid‐latitude British Columbia (BC), and lower latitudes in the USA. The occurrence of the neogondolellins in key sections and in matrix of dated ammonoid collections is documented. Neogondolellins characteristic of seven ammonoid zones are identified. Fifteen new conodont species are assigned to four genera: Borinella, Columbitella, Magnigondolella and Neogondolella. Borinella, more common in the Smithian, undergoes a radiation in the early Spathian ‘tirolitid n. gen. A’ ammonoid beds of California eventually resulting in five new Neogondolella species (Ng. bucheri, Ng. darwinensis, Ng. praeacuta, Ng. sinuosa, and later Ng. spathiconstricta) and the first new Magnigondolella, Mg. mutata. Several of these plus Bo.? curvata sp. nov. also occur above the tardus Zone in British Columbia (BC). In the next younger ammonoid zone with Tirolites, the first Columbitella are Cb. joanae and Cb. weitschati. Middle Spathian Columbites and Procolumbites ammonoid beds in the USA are dominated by Cb. elongata, whereas the broadly equivalent strata in the north contain Cb. amica, Cb. brevis sp. nov. and Cb. paragondolellaeformis. Late Spathian radiation produces six new species of Magnigondolella: Mg. incurva, Mg.? minuta and Mg. trutchensis in the Prohungarites ammonoid beds, followed by Mg. acuminata, Mg. tozeri and Mg. peribola in the haugi and subrobustus ammonoid zones.