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Hyoliths recorded from the middle Cambrian Jince Formation of the Barrandian area in the Czech Republic are reviewed and listed, based on various published papers printed since 1854. Up to now, only five species of hyolithids and three species of orthothecids have been reported, classified within seven genera. The reported material was collected from more than twenty small occasional outcrops and/or sections measuring up to several tens of meters in thickness, all situated exclusively in the area between the villages Felbabka and Čenkov in the Litavka River Valley. From the Paseky Shale member of the Holšiny-Hořice Formation at the Medalův mlýn locality, the first hyolith classified as “Hyolith genus and species indeterminate” is described. The new study of two specimens described and figured by Barrande in 1867 as Hyolithes primus made it possible to classify them as Jincelites vogeli and Jincelites sp. respectively.

The early middle Cambrian Tannenknock Formation of the Franconian Forest, traditionally subdivided into the Galgenberg and Wildenstein strata, yields a relatively diverse fauna. This fauna includes a number of molluscs, which portrays a fairly diverse assemblage that can be regarded as paradigmatic for the lower–middle Cambrian boundary interval in West Gondwana, with the helcionelloid genera Helcionella, “Bemella,” “Igorella,” Latouchella, Leptostega, Yochelcionella, the pelagiellid Pelagiella, a stenothecoid, and the Hyolithida Hyolithes?, Hexitheca?, Jincelites, Maxilites?, Aladraco, Cambrachelous, the Orthothecida Brevitheca?, Nephrotheca?, and a number of helcionelloid and hyolith forms dealt with under open nomenclature. New species include the helcionelloids Helcionella lemdadensis sp. nov. and Leptostega frankenwaldensis sp. nov. and the hyoliths Grantitheca? klani sp. nov. and Cambrachelous diploprosopus gen. et sp. nov. The stenothecoid discovered in the Wildenstein Member of the formation is the first report of the group from West Gondwana.

The hyolith assemblage from the early Cambrian of Bornholm, Denmark, shows a higher diversity than contemporary assemblages in Baltoscandia. The most common species in the Green Shales (Laesa Formation, Norretorp Member, Cambrian Stage 3), is Hyolithes [=Hyolithus] (Orthotheca) johnstrupi Holm, 1893. A specimen of this species shows a well-preserved and almost complete digestive tract, folded into an approximately 22mm long chevron-like structure comprised of at least 20 arcuate loops on the ventral side and a flattened, gently sinuous to straight anal tube on the dorsal side. The thin, phosphatic outer shell layer of the conch is crushed under the digestive tract due to compaction while the digestive tract is preserved in three dimensions and appears undisturbed. The shape of the digestive tract is similar to that of the middle Cambrian Guduguwan hardmani (Etheridge) from Australia and the lower Cambrian specimens from Russia described by Mekova & Sysoev. The Danish specimen is probably an adult, lending support to the idea that the orthothecid digestive tract becomes more complex during ontogeny. Hyolithus (Orthotheca) johnstrupi is revised and here referred to Circotheca Sysoev, 1958.

Hyoliths are usually preserved as isolated skeletal elements consisting of conch, operculum, and helens. The occurrence of a conch associated with an operculum is ordinarily exceptional, and the co-occurrence of helens with other skeletal parts is a great rarity. The extraordinary finds of hyolithid conchs associated with opercula in situ are relatively abundant in the Cambrian and Ordovician clastic sediments of the Barrandian area in the Czech Republic. The platyclaviculate operculum with clavicles divided by longitudinal walls into channels characterizes members of the newly established family Slapylitidae fam. nov., which includes two genera: Slapylites Marek, 1980 known from the mid-Cambrian of West Gondwana and Baltica and Nevadalites Marek, 1976 documented from the Late Cambrian of Laurentia. To this family most probably belongs also an operculum from the Cambrian Series 2–Series 3 boundary of North Greenland and poorly known material from the Middle Devonian of Bolivia.

The rare hyolith Alfaites romeo gen. et sp. nov. is described from the lower half of the middle Cambrian (Drumian) Buchava Formation of the Skryje-Týřovice Basin in the Barrandian area of the Czech Republic. This new taxon is based on excellently preserved external and internal moulds of three opercula and several conchs collected from carbonate nodules and shale. This rare species has been established at three separate outcrops in the lower part of the Biozone of Paradoxides (Eccaparadoxides) pusillus (Barrande 1846). Morphology of conch and both external and internal surface of operculum are well known. However, specific morphology excludes assignment to any predescribed hyolithid family.

Two orthothecid hyoliths, Gracilitheca astronauta n. sp. and Nephrotheca sophia n. sp. are described from the “middle” Cambrian Buchava Formation of the Skryje-Týřovice Basin in the Czech Republic. The new forms are based on about thirty well-preserved external and internal moulds of both conchs and opercula. Gracilitheca astronauta n. sp. is classified under the family Gracilithecidae Sysoev, 1972 and may be distinguished by clearly triangular cross-section of the conch, whereas Nephrotheca sophia n. sp. is characterized by transversally elongated cardinal processes reaching the lateral opercular margin and is combined with the family Orthothecidae Sysoev, 1958 emended Malinky, 2009. Several specimens of G. astronauta show operculum preserved inside of the conch. Stratigraphic ranges and geographic distributions within the Skryje-Týřovice Basin are established for both taxa.

VALENT, M., FATKA, O. & MAREK, L., iFirst article. Gracilitheca and Nephrotheca (Hyolitha, Orthothecida) in the Cambrian of the Barrandian area, Czech Republic. Alcheringa, 1–10. ISSN 0311-5518. Five orthothecid hyoliths, Gracilitheca mirabilis sp. nov., Gracilitheca triangularis sp. nov., Gracilitheca sp., Nephrotheca betula sp. nov. and Nephrotheca sp. are described from the ‘middle’ Cambrian Buchava Formation of the Skryje–Týřovice Basin in the Czech Republic. The new forms are based on about forty well-preserved external and internal moulds of conchs; opercula of all species remain unknown. Stratigraphic ranges and geographic distributions within the Skryje Týřovice Basin are established for all taxa.

The hyoliths Slehoferites slehoferi gen. et sp. nov. and Carinolithes bohemicus sp. nov. are described from carbonatic nodules and shale at different stratigraphic levels within the middle Cambrian Buchava Formation of the Skryje-Týřovice Basin in the Czech Republic. Carinolithes bohemicus sp. nov. may be distinguished by a slightly dorsally curved conch with three longitudinal rounded ridges forming a distinct keel on the dorsum and by a platyclaviculate operculum with broad clavicles with their distal ends open, whereas the defining traits of Slehoferites slehoferi gen. et sp. nov. are a conch with a slightly rounded triangular cross-section, distinct muscle scar on the ligula and a platyclaviculate operculum with an almost circular outline and with broadly diverging cardinal processes clavicles (about 40 degrees for clavicles) with a cone cavity below each clavicle. Both taxa are combined under the new family Carinolithidae which differs from other hyolithid families in having a dorsum with developed keel-like ridges, faily long ligula, and a platyclaviculate operculum with distinct and broadly diverging cardinal processes.

Two new endemic genera and species of extinct group of Hyolitha, Skryjelites auritus gen. et sp. nov. and Quasimolites quasimodo gen. et sp. nov. are described and illustrated from the Buchava Formation of the Barrandian area (Czech Republic).