Roger J. Cuffey

Expanded reef-rock textural classification and the geologic history of bryozoan reefs

The wide range of colony forms assumed by bryozoans results in a greater variety of bryozoan-reef-carbonate-rock types than can be accommodated within present classifications. Consequently, the currently used textural classification is expanded to include several new reef-rock categories (branchstone, cruststone, globstone, lettucestone, shellstone) immediately applicable to bryozoan reefs. Those in the early Paleozoic were small mounds, largely cruststones and bindstones, accompanied later by globstones and lettucestones; a very few similar mounds live today. Others, many larger, in the mid-and late Paleozoic, were branchstones and bafflestones, in some cases so sediment-rich as to appear mostly as floatstones with interspersed rudstones to micstones.

The concepts of astogeny and ontogeny in stenolaemate bryozoans, and their illustration in colonies of Tabulipora carbonaria from the Lower Permian of Kansas

JOSEPH F. PACHUT, ROGER J. CUFFEY, AND ROBERT L. ANSTEY Department of Geology (Cavanaugh Hall), Indiana University-Purdue University at Indianapolis, 425 University Boulevard, Indianapolis 46202, Department of Geosciences (Deike Building), Pennsylvania State University, University Park 16802, and Department of Geological Sciences (Natural Science Building), Michigan State University, East Lansing 48224

Paleozoic age of the Walden Creek Group, Ocoee Supergroup, in the western Blue Ridge, southern Appalachians: Implications for evolution of the Appalachian margin of Laurentia

In the foothills of the Great Smoky Mountains in Tennessee, low-grade metamorphic rocks of the Walden Creek Group, Ocoee Supergroup, contain a fossil assemblage composed of trilobites, bryozoans, ostracodes, pelmatozoans, algae, and agglutinated foraminifers, indicating a Silurian or younger age. The new paleontological data contradict older ideas on the Neoproterozoic age of the Walden Creek Group. The Walden Creek Group was not deposited in a continental rift basin preceding the opening of the Iapetus ocean but, possibly, in a pull-apart basin formed in a transtensional event during the Acadian orogeny. There is no field evidence indicating that the Walden Creek Group is separated from the lower units of the Ocoee Supergroup by a basin-wide unconformity and hiatus. A tentative geodynamic model is presented for the Ocoee Supergroup basin; the model is dependent on paleontological data indicating a Paleozoic age for the Walden Creek Group and concentrates on lithologic, petrographic, and basin characteristics. The model allows for the possibility that the entire Ocoee Supergroup was deposited in a Paleozoic transtensional basin.

The World’s Oldest-Known Bryozoan Reefs: Late Tremadocian, mid-Early Ordovician; Yichang, Central China

The world’s earliest-known bryozoan-built reef-mounds are in mid-Lower Ordovician (upper Tremadocian) strata near Yichang, Hubei Province, central China. Their framework, a globstone, was built by abundant rounded zoaria of the trepostome Nekhorosheviella semisphaerica. That framework further baffled micrite immediately around the colonies, more broadly surrounded regionally by bioclastic calcarenites (Fenxiang Formation). Fragments of delicate branching Orbiramus normalis occur rarely in the bryohermal micrite.

New trepostome Bryozoa from the Early Triassic (Smithian/Spathian) of Nevada

KurzfassungZwei neue Bryozoen-Arten der Familie Dyscritellidae (Trepostomata),Dyscritellopsis thaynesianus n. sp. undDyscritellopsis montelloensis n. sp., werden aus den Thaynes Kalken der unteren Trias (Smithian/Spathian) von Nevada (USA) beschrieben. Die Bryozoen-Fauna liefert weiteren Beleg für das Überleben paläozoischer Stammlinien in frühest triadischer Zeit auf den offenen Schelfen der Nordhemisphere außerhalb der Tropen. Sie zeigt paläobiogeo-graphische Beziehungen zu Faunen der Unteren Trias von Spitsbergen.AbstractTwo new bryozoan species of the trepostome family Dyscritellidae,Dyscritellopsis thaynesianus n. sp. andDyscritellopsis montelloensis n. sp., are described from the Early Triassic (Smithian/Spathian) Thaynes Limestone, Nevada (USA). The bryozoan fauna documents the survival of Paleozoic lineages into the earliest Triassic on northern open shelves outside the tropics. The fauna holds paleobiogeo-graphic connections to the Early Triassic bryozoan faunas of Spitsbergen.

Inconobotopora lichenoporoides , a new genus and species of cystoporate bryozoan from the Silurian of Gotland, and its evolutionary implications

An unusual, lichenoporid-like bryozoan colony from Mid-Silurian strata on Gotland is described as a new cystoporate, Inconobotopora lichenoporoides new genus and species; a poorly known form from the same area and approximate horizon is reclassified as Inconobotopora silurica (Hennig, 1906). Similarities in overall morphology, particularly flagged by the distinctive radial-disk construction, combine with geochronologic sequence to suggest the possibility of an evolutionary lineage from Ordovician Constellaria, through Silurian Inconobotopora, to Devonian Botryllopora, and perhaps even on to Cretaceous-Cenozoic-Recent Lichenopora (although this last extension is extremely difficult to demonstrate in the present state of knowledge).

Depth-related associations of cryptic-habitat bryozoans from the leeward fringing reef of Bonaire, Netherlands Antilles

The distribution of modern reefdwelling bryozoans provides a guide for recognizing and interpreting bryozoan zonation in ancient reefs. Toward that end, cluster analysis and gradient analysis were used to examine depth zonation of bryozoan species occupying cryptic habitats on the leeward fringing reef of Bonaire. Both analytical techniques produced clusters of sample depths representing shallow(1-9 m), intermediate(12-33 m), and deepwater (40-61 m) habitats. Similarly, both grouped species into 4 depthrelated associations, including shallow, intermediate, intermediate-todeep, and deep water associations from cluster analysis, and shallow, shallow-to-intermediate, intermediate-to-deep, and deep water associations from gradient analysis. Results were corroborated by canonical discriminant function analyses. In both analyses, interpretable associations of species were recognizable in spite of intergradational distributions down the reef front; most displayed subtle differences in abundances across a range of depths with only a few species restricted to narrow ranges of depths. Gradient analysis produced the more interpretable results because, unlike cluster analysis, a single ordering of species along the depth-gradient resulted. In contrast, terminal branches or subclusters, determined by cluster analysis, may be rotated at branch bifurcations into a variety of species arrangements, with no objective means of determining which permutation most accurately portrays interspecific relationships along the environmental gradient. Additionally, the ordination of species by gradient analysis produced species associations which contained a higher percentage of the total number of colonies sampled across member species than was the case for cluster-defined species groupings. Because taphonomic processes may strengthen the expression of gradients, similar species associations in fossil reefs have a high probability of being recognized, especially through the use of gradient analytical techniques, and may provide a framework for the establishment of paleobathymetry.

A bryozoan-like chaetetid (possible sclerosponge)from Jurassic-Cretaceous limestone near Orhaneli, Northwestern Turkey

Abstract Bryozoan-like fossils have been found rarely in Upper Jurassic or Lower Cretaceous limestone near Orhaneliin northwestern Turkey; they represent the chaetetid species Atrochaetetes alakirensis CUIF & FISCHER, 1974 , possibly a sclerosponge, and previously known only from the lower part of the Upper Triassic.