BRACHIOPOD SEQUENCE THROUGH THE UPPERMOST DEVONIAN HANGENBERG EXTINCTION INTERVAL IN THE WESTERN ILLINOIS BASIN-CENTRAL NORTH AMERICA

We present results of an investigation of the Latest Devonian brachiopod sequence spanning the global Hangenberg Extinction and post-extinction interval in the Illinois Basin based on restudy of type material illustrated in twentieth century studies by Weller, Williams and Carter, and new field-based collections from the type areas of Late-Latest Famennian units in eastern Missouri and Iowa. The fauna from the Hangenberg interval occurs in shale and siltstone shelf facies of the English River Formation in central and southeastern Iowa associated with conodonts spanning the interval of Upper expansa? to costatus-kockeli interregnum (= Lower-Middle praesulcata zones). The English River fauna consists of twenty species of the genera Chonopectus, Mesoplica, Ovatia, Semiproductus Sentosia, Plicohonetes?, Leptagonia, Schuchertella?, Schellwienella, Schizophoria (S.), Paraphorhynhus, Eudoxina, Syringothyris, Kitakamathyris, Hispidaria? Camarorphorella, Iniathyris and Eumetria. Rapid deepening initiated Louisiana Limestone carbonate platform deposition in eastern Missouri, Iowa and western Illinois. The post-Hangenberg survivor and recovery fauna of the Louisiana Limestone occurs with conodonts of the kockeli Zone. Twenty or more brachiopod species known from the Louisiana Limestone are included in the genera Anthocrania, Petrocrania, Rhipidomella, Schuchertella, Plicochonetes, Orbinaria, Cyphotalosia?, Leptolosia, Paraphorhynchus, Cyrtina, Tylothyris, Acanthospirina, Syringothyris, Parallelora, Kitakamathyris, Crurithyriss, Athyris and Camarorphorella. The brachiopod sequence records a near total turnover at the species level of the English River fauna, with only two English River species (Kitakamathyris cooperensis & Camarophorella buckleyi) ranging into the Lousiana (kockeli Zone). Five of eighteen English River genera carryover into the Louisiana fauna. Glacial-eustatic sea level fall terminated Louisiana deposition, and the post glacial sea level rise (sulcata-duplicata zones) re-established subtropical platform deposition in the region with survivor and recovery clades diversifying rapidly in the subtropics during earliest Tournaisian including as many as 37 species described from the western Illinois Basin by Carter.