Taxonomy and correlation of Lower Triassic (Spathian) segminate conodonts from Oman and revision of some species of Neospathodus

Exceptionally well preserved Lower Triassic conodonts from Oman include an array of Neospathodus species, many of which are new. Those from the upper Lower Triassic, or Spathian, are described in conjunction with a restudy of conodont type material from Chios, Greece, and an assessment of contemporary collections from Pakistan and western North America. The taxonomic scope of three key species from Chios, Neospathodus homeri, N. triangularis, and N. gondolelloides, is revised. Seven new species are described from Oman: N. abruptus, N. brevissimus, N. brochus, N. crassatus, N. curtatus, N. pusillus, and N. symmetricus; and one new species, N. clinatus, is described from Pakistan. The allied Icriospathodus collinsoni is also described from Oman. The occurrence and range of Neospathodus species are presented in the context of the ammonoid succession in the Spathian of North America. Both N. homeri and N. triangularis, as revised, have shorter ranges and are more age diagnostic than previously thought. Neospathodus gondolelloides is a distinct taxon, and not synonymous with Chiosella timorensis. Five informal faunal divisions are identified based on Neospathodus and allied species. In ascending stratigraphic order, these are typified by Icriospathodus collinsoni, Neospathodus homeri, N. triangularis, N. symmetricus, and N. gondolelloides. Oman collections represent three of these faunas, which occur also in the Columbites through Prohungarites/Subcolumbites ammonoid beds of western U.S.A.