Acta Musei Nationalis Pragae, Series B, Natural History, 59 (3–4): 99–150 issued December 2003 Sborník Národního muzea, Serie B, Přírodní vědy, 59 (3–4): 99–150 SILICIFIED BRACHIOPODS OF THE KOTÝS LIMESTONE (LOCHKOVIAN) IN THE BUBOVICE AREA (BARRANDIAN, BOHEMIA) MICHAL MERGL Department of Biology, University of West Bohemia, Klatovská 51, 306 19, Plzeň, Czech Republic, [email protected] Mergl, M. (2003): Silicified brachiopods of the Kotýs Limestone (Lochkovian) in the Bubovice area (Barrandian, Bohemia). – Acta Mus. Nat. Pragae, Ser. B, Hist. Nat., 59 (3–4): 99–150. Praha. ISSN 0036-5343 Abstract: An exceptionally preserved silicified brachiopod material is described from the Kotýs Limestone (Lochkov Forma- tion, Lochkovian) from two localities between Bubovice and Loděnice in the Central Bohemia. The shells have preserved the finest details of internal and external morphology, such as brachidia, crural plates, trails and spines, and represent the unique brachiopod material in the Barrandian. In total thirty-eight species have been determined, with new species Dicoelosia prae- dimera, Muriferella pishulinae, Spinatrypina variabilis, Glassina gutta, Retzia piriformis, Ambocoelia bubovica, and Quad- rithyris subrobusta. Genera Muriferella, Anastrophia, Spinatrypina, Glassina, Retzia, and Quadrithyris have been recognized from the Lochkovian strata for the first time in the Barrandian. The composition of the brachiopod fauna in the studied sequ- ence indicates a transition from a shallower, high-diversity assemblage with spiriferids, pentamerids, strophomenids, orthote- tids, large orthids and spinose atrypids to a deeper, low-diversity assemblage with dominance of small orthids, and costellate and smooth atrypids. I Brachiopoda, taxonomy, shell morphology, Devonian, Lochkovian, Barrandian, Bohemia Received December 6, 2003 Introduction were described on extremely fragmentary shells, even with obscure general outline and convexity. Other species were In his latest published brachiopod paper, V. Havlíček based on few specimens and only basic data of their inter- (1999) described and evaluated the brachiopod fauna of the nal morphology were described. Limited number of speci- Lochkov Formation, the earliest Devonian unit of the Bar- mens did not allow any evaluation of the morphological randian. His main attention was directed to a remarkably variability and growth changes. The internal morphology of rich fauna of the Kotýs Limestone in the Svatý Jan pod some brachiopod groups (e.g. atrypids, spiriferids) was Skalou area (Central Bohemia). The brachiopod list com- studied by serial sectioning, but partial silicification ob- piled by him comprises 53 rhynchonelliform brachiopods, scured some details. Consequently, the illustration and de- of which V. Havlíček described six species as new. A re- scription of many species do not correspond with a modern markably rich brachiopod assemblage of the Lochkovian standard of a systematic taxonomy, and some taxa remain age occupied, according to Havlíček (1999), the top of sub- inadequately known for a comparison with foreign species. marine volcanogenic accumulation near Svatý Jan volcanic Indeed, although taxonomy of brachiopods from the Kotýs centre. This local shallow water environment was Limestone has been almost resolved by Havlíček (1999), favourable for rich marine life, with dominant brachiopods much important information remained unknown. and crinoids among the sessile animals. The brachiopod This poor knowledge of some elements of the bra- communities flourished on a shallow bottom surrounded by chiopods fauna of the Kotýs Limestone was, among others, much deeper basinal environment in S and E, with less di- the result of sampling methods and mode of preservation. verse level-bottom communities. The shells used by Havlíček (1967, 1977, 1999) were partial- In historical overview, already Joachim Barrande knew ly collected by hammering and partially by washing of shells some of the brachiopods of the Kotýs Limestone in mid of from deeply weathered limestone beds. However, a natural the 19th Century (Barrande 1847, 1848). Some thirty years corrosion of the calcareous or partially silicified shells result- later, in his Système Silurien du centre de la Bohême, Bar- ed into poorly preserved specimens, especially of thin-walled rande (1879) described sixteen species, which were revised and minute species (e.g. Navispira, Atrypina, Skenidioides). by Vladimír Havlíček in several papers between 1959 and A discovery of unweathered limestone with abundant 1999 years. silicified brachiopods, corals and rarely other fauna made Despite the long time span of the study of the Lochko- possible the etching of limestone blocks by hydrochloric vian brachiopod fauna, numerous species remain poorly acid solution. The residues yielded numerous and remark- known. This is due to their rarity and poor preservation, ably well-preserved brachiopod shells, sometimes with pre- with fragmentary shells, often lacking fine morphological served lophophore supports, fine spines and trails, and other details. Especially, the orthid brachiopods (Havlíček 1977) features undiscovered by the former sampling methods. 99 fragmentary and partly weathered silicified fauna. The qual- ity of the material is worse than at the first locality, with small differences in taxonomic composition. The silicifica- tion in both localities occurs in 5 to 10 m thick sequence middle part of the Lochkov Formation, above the beds of grey crinoidal sparitic limestone near the base of the Lochkov Formation. An effort to find the silicified material in the classical palaeontological localities of the Kotýs Limestone in the surrounding of Svatý Jan pod Skalou, especially in the Solvay’s Quarry were unsuccessful. Methods Blocks of limestone (5–10 kg) have been dissolved by a solution of 15% hydrochloric acid for one to three days. The residues were carefully washed by water and desiccat- Text-fig. 1. Map of Loděnice – Bubovice area (Barrandian, ed. In total, about 200–250 kg of limestone were dissolved. Central Bohemia) showing localities 1 and 2. All complete specimens were carefully picked up. Richly fossiliferous fine fractions from some beds were picked up even under the binocular lens. The aim of the paper is to better illustrate the previous- ly described species, to re-evaluate some described taxa on Material newly discovered morphological features, and to describe newly collected species. In the systematic part, all new im- The brachiopod shells prevail among the silicified fos- portant data for brachiopod taxonomy are presented. A short sils. Apart from common rugose corals, tabulate corals, diagnosis of species is given where it is possible. The new crinoids, gastropods, bryozoans and tiny trilobites are rare. descriptions, redescription of imperfectly known species or The quality of silicification differs among invertebrate descriptions of new morphological features are presented in groups as well as brachiopod groups. Brachiopods and ru- addition to the data already published. The species previ- gose corals are generally well silicified, except of ously described in detail are only commented or illustrated. strophomenoids. This is probably due to thin fragile The answers to many expressed questions by Havlíček strophomenoid shell and incomplete silicification of their (1999) concerning the systematic position of particular taxa valves. Unlike brachiopods, small crinoids (Pisocrinus) are could be resolved. However, only the newly collected coarsely silicified leaving distinct only their basic morphol- species are illustrated and commented, leaving some by ogy. Large, but rare platycerid gastropods, unlike other gas- Havlíček (1959, 1961b, 1967, 1977, 1992a, 1992b, 1999) tropods, are nicely silicified. Some ten to hundred described species from the Kotýs Limestone without any thousands brachiopod shells were present in residues as comments. The ecological evaluation and biogeographic may be estimated by the number of shells from the known affinity of the fauna will be published elsewhere. volume of the rock. However, mostly incompletely silicified or broken shells were present in the residues. The amount of the shells and their fragmentation differ bed to bed. The Localities finest silicification has been discovered in the lower beds, New silicified material was collected in two localities just above the lowest exposed limestone beds, which are between Bubovice and Loděnice, some 7 km NE from Ber- without silicified fossils. The best silicification preserved oun. The first site (locality 1) is situated in a short trench in the finest morphological details, e.g. short spines and free N side of a small abandoned quarry,1200 m NE from space between doublure and dorsal part of pleura on small Bubovice, on N slope of wooded ridge called Špičatý vrch odontopleurid trilobites, and it is comparable with the best (text-fig. 1). Some seventeen metres thick section is built by examples of fossil silicification in other parts of the world. dark grey well-bedded, platy micritic and sparitic limestone, In general, the silicification is less favourable, often leaving bearing abundant shell accumulations (text-fig. 2). The margins and thick shell walls without silicification. Some- dark-grey cherts, mostly in small irregular and often lobate times, the bivalved shells are silicified including the sedi- lenses, are common. Limestone beds are steeply dipping to ment infilling between the valves. Concentric silicification N, in the upper part of