We think that the complex relationships that exist between Idiognathodus and Streptognathodus must be investigated from the inception of these morphologies, from Morrowan and Atokan
time, and that all troughed and partially troughed forms prior to Missourian should be excluded from Streptognathodus.
The late Atokan
(Moscovian-Pennsylvanian) chaetetid accumulations of Sierra Agua Verde, Sonora (NW Mexico): composition, facies and paleoenvironmental signals, p.
Their topics include Lower Cambrian shelled phosphorites from the northern Montaigne Noire in France, Siluro-Devonian alpine reefs and pavements, a late Atokan
regional encrinite in the Sierra Agua Verde in northwestern Mexico, and whether the distribution of tabulae in tabulates can be used to estimate palaeo-environmental changes.
Serendipitously, the project may also encounter oil and gas in the Atokan
Conglomerates, the Caddo Limestone, the Strawn Sands and the Cisco Sands.
The well targeted the lower Atokan
The second well will target typical Arkoma Basin Atokan
objectives at depths between 7000' and 10,000'.