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

Abstract

Exceptionally well preserved Lower Triassic conodonts from Oman include an array ofNeospathodusspecies, 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, andN. gondolelloides, is revised. Seven new species are described from Oman:N. abruptus, N. brevissimus, N. brochus, N. crassatus, N. curtatus, N. pusillus, andN. symmetricus;and one new species,N. clinatus, is described from Pakistan. The alliedIcriospathodus collinsoniis also described from Oman. The occurrence and range ofNeospathodusspecies are presented in the context of the ammonoid succession in the Spathian of North America. BothN. homeriandN. triangularis, as revised, have shorter ranges and are more age diagnostic than previously thought.Neospathodus gondolelloidesis a distinct taxon, and not synonymous withChiosella timorensis.Five informal faunal divisions are identified based onNeospathodusand allied species. In ascending stratigraphic order, these are typified byIcriospathodus collinsoni, Neospathodus homeri, N. triangularis, N. symmetricus, andN. gondolelloides.Oman collections represent three of these faunas, which occur also in theColumbitesthroughProhungarites/Subcolumbitesammonoid beds of western U.S.A.