Abstract

Tentaculitoid microconchid tubeworms from Devonian (uppermost Emsian–upper Givetian) deposits of the Holy Cross Mountains, Poland, include three new species from stratigraphically well-constrained lithological units: Polonoconchus skalensis n. gen. n. sp., Palaeoconchus sanctacrucensis n. sp. and Microconchus vinni n. sp. The microconchids inhabited fully marine environments during transgressive pulses, as is evidenced from facies and associated fossils. Polonoconchus skalensis n. gen. n. sp. and Palaeoconchus sanctacrucensis n. sp. inhabited secondary firm- to hard-substrates in deeper-water, soft-bottom environments. They developed planispiral, completely substrate-cemented tubes and planispiral tubes with elevated apertures, which is indicative of environments where sedimentation rate is low but competition for space (by overgrowth) may be high. Microconchus vinni n. sp., on the other hand, developed a helically coiled distal portion of the tube as a response to a high sedimentation rate. As the taxonomic composition of Devonian microconchids is poorly recognized at both regional and global scales, this new material contributes significantly to our understanding of the diversity of these extinct tube-dwelling encrusters.

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