Abstract

The Všeradice section was trenched and continuously sampled for graptolites from the base of the post-extinction upper Homerian strata to low in the Ludlow. The upper Homerian is divisible into three biozones, a lower parvusnassa Biozone, a middle praedeubelideubeli Biozone, and an upper ludensisgerhardi Biozone, the last named being succeeded by graptolites of the lowest Ludlow nilssoni Biozone. The graptolite diversity of nine species in the upper part of the parvusnassa Biozone is the highest in the world. Five monograptid species, Pristiograptus parvusUlst, 1974, P. dubius (Suess, 1851), Colonograptus deubeli (Jaeger, 1959), Colonograptus gerhardi (Kühne, 1955), and Colonograptus praedeubeli (Jaeger, 1990) are described from the upper Homerian. Twelve species of retiolitids, Gothograptus nassa (Holm, 1890), Neogothograptus cf. balticus (Eisenack, 1951), Spinograptus spinosus (Wood, 1900), Spinograptus clathrospinosus (Eisenack, 1951), Spinograptus munchi (Eisenack, 1951), Spinograptus reticulolawsoni (Kozłowska-Dawidziuk, 1997) Spinograptus? cf. nevadensis (Berry and Murphy, 1975), Spinograptus? sp. A and Spinograptus? sp. B, Plectograptus macilentus (Törnquist, 1887), and Plectograptus? karlsteinensis new species and Plectograptus? ovatus new species, are described and illustrated from upper Homerian and lowest Ludlow strata. The two new species occur in the upper parvus–nassa and lowest praedeubeli–deubeli, and ludensisgerhardi biozones, respectively. Two morphs of Gothograptus nassa, a narrow (more typical) form, and a wide form, are recognized. While overlapping in their overall ranges, their occurrences in any particular small interval are sometimes mutually exclusive, suggesting ecological control.

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