Diagenetic history of the upper Tanglewood Member (upper Ordovician) of the Lexington Limestone, central Kentucky, U.S.A. with special emphasis on petrographic differences between deformed and undeformed beds

Petrographic study was carried out for the upper Tanglewood Member (upper Ordovician) of the Lexington Limestone in order to understand its diagenetic history and predict whether the cementation is pre-deformational or post-deformational by comparing the deformed and undeformed beds of the same horizon. This study shows that the diagenetic processes, which have modified the sequence of the upper Tanglewood Member of the Lexington Limestone, consist of micritization, cementation, compaction, dolomitization and internal filling. Moreover, it indicates that the main episode of cementation took place after the sediment deformation.

A new species of the dual-mouthed paracrinoid Bistomiacystis and a redescription of the Edrioasteroid edrioaster priscus from the Upper Ordovician Curdsville Member of the Lexington Limestone

Echinoderms are important faunal components in the Curdsville Member of the Lexington Limestone. Numerous clades are represented, including Crinoidea (Springer, 1911; Parsley, 1981), Paracrinoidea (Parsley and Mintz, 1975; Parsley, 1981), Cyclocystoidea (undescribed), Edrioasteroidea (Miller and Gurley, 1894; Bell, 1976, 1979), and Stylophora (Parsley, 1981, 1991). Although some of these taxa are well preserved (Springer, 1911), most have been recovered from residues of acidized samples. These later specimens are poorly preserved, obscuring much of the information. Here we describe well preserved specimens recently collected by members of the Kentucky Paleontological Society (Lexington) of two species that add significantly to our understanding of lesser known components of the Curdsville Fauna. Bistomiacystis schrantzi n. sp. is a large paracrinoid bearing two separate ambu1acral systems that lead to two peristomial openings. Our research suggests that this unusual arrangement is consistent with oral areas of other derived blastozoans bearing oral plates. Edrioaster priscus (Miller and Gurley) is a poorly known large edrioasterid edrioasteroid previously known only from specimens preserved in coarse beekite. The new material of this taxon allows for a thorough characterization of this poorly known edrioasteroid and shows that previous assessments of its size and morphology need revision.

Phylogeny, systematics, and biostratigraphy of the Ordovician bryozoan genus Peronopora

Specimens of Peronopora Nicholson, 1881, are abundant in Upper Ordovician rocks of the North American Midcontinent. Based on the positions of units in the Composite Conodont Standard Section, we have sampled 211 specimens over a stratigraphic interval of 9.1 million years. The average duration of sample spacing is 61,664 years but is commonly as small as 32,800 yr.Thirty-four morphometric characters were measured in each specimen and were converted into multistate characters; character-state breaks were established based upon each character's ability to discriminate between phenetic groupings. Each character was subsequently weighted based on the number of derived states, degree of independence from other attributes, and estimated heritability.Cladistic analysis of these data indicate that there are eight species in Peronopora each consisting of an optimally defined crown group and a basal stem group (or paraclade). Character states shared by stem and crown groups define species but, within species, stem and crown groups also differ in some character states. The species are, in ascending order from the base of the tree, Peronopora decipiens (Rominger, 1886), P. compressa (Ulrich, 1979), P. pauca Utgaard and Perry, 1964, P. milleri Nickles, 1905, P. horowitzi new species, P. vera Ulrich, 1888, P. sparsa Brown and Daly, 1985, and finally P. dubia (Cumings and Galloway, 1913). Diagnostic keys permit the unique assignment of each specimen to a species and the separation of members of stem groups from those of crown groups. Thirty-one characters are required to discriminate between all 211 specimens. This contrasts with previous studies of Peronopora where eight or fewer characteristics were used. Of the ten characters most useful in discrimination, only three had been used in the conventional species literature. This accounts, largely, for only 29.8 percent (51 of 171) of previously identified specimens being classified as members of the same species in this analysis. Discriminant function analysis of original measurements, using species identity as the grouping criterion, produces statistically significant separation of species.It appears that stratigraphic position had an explicit and undue effect on previous concepts of species many of which could not be recognized independently of stratigraphic position. All species of Peronopora appear, or are inferred to have appeared, within the Lexington Limestone between the base of the Grier Member and the top of the Millersburg Member. The cladogram indicates that species evolved in a sequential order, but their first appearance datums have been stratigraphically punctuated. Three species have ranges terminating in the Early to Middle Maysvillian, one in the Middle Richmondian, and four in the Late Richmondian. The latter four (or five) of these species died out in the extinction associated with the unconformity at the top of the Richmondian.