Study and Use of Upper Cambrian to Lower Ordovician conodonts in central, southern, and western Laurentia, 1933-2018

The first descriptions of Laurentian Lower Ordovician conodonts were in the 1930s in the central USA. Authors boiled shales to free the conodont elements. The use of acetic acid began in 1940 at the University of Missouri. The first study of Cambrian conodonts was in 1959; part of the material was from the western USA and part from northern Europe. In the mid 1960s, research began to be based on measured sections and systematically collected samples; many new taxa still were being described. Histological studies resulted in recognising three major groups of Cambrian conodonts, protoconodonts, paraconodonts, and euconodonts. The latter group was the most successful. Preliminary biozonal frameworks were established in the early 1970s and were tied into biozonations based on other fossil groups. Conodont studies became more widespread geographically during the 1980s, biozonations were refined, and conodont zones began to be correlated globally based on many cosmopolitan taxa. In the 1980s, geochemists found that conodonts were useful source materials for chemostratigraphy. The Pander Society was founded in 1967. Regular meetings of the society have been held since 1968 in the USA and internationally, resulting in many important proceedings volumes. The International Working Group on the Cambrian-Ordovician Boundary decided to use conodonts as the primary fossil group to define that boundary, thus stimulating intensive study of conodonts of that age. Definition of that boundary was achieved in 2001, although problems remain because of redeposited conodonts at the stratotype section. A Working Group will recommend a GSSP for the base of the highest stage of the Cambrian, Stage 10. The lowest occurrence of the euconodont Eoconodontus notchpeakensis (Miller Journal of Paleontology, 43(2), 413-439 1969) is being considered to define the base of that stage. The species occurs in depositional environments from nearshore sandstones and dolostones to deep-ocean radiolarian cherts, indicating that conodonts had become adapted to many depositional environments during the late Cambrian. The alternative fossil for marking the base of Stage 10 is the lowest occurrence of an agnostoid arthropod, Lotagnostus americanus (Salter 1860), which has a controversial taxonomy.