Stenolaemate bryozoans from the Graham Formation, Pennsylvanian (Virgilian) at Lost Creek Lake, Texas, USA

An exceptionally well-preserved bryozoan fauna has been described from the Finis Shale Member, Graham Formation, Pennsylvanian (Virgilian) at Lost Creek Lake, Texas, USA. Nineteen bryozoan species (four cystoporates, one trepostome, two rhab-domesine cryptostomes, and 12 fenestrates) have been identified in two profiles which cut the most vertical range, at the level of the outcrop-base, of the Finis Shale. Two species are new: a trepostome Dyscritella felixi n. sp. and a fenestrate Laxifenestella texana n. sp. The fauna was studied on a combined basis of external and internal mor-phology, using a SEM and thin sections, respectively. Bryozoans from the Finis Shale Member exhibit a variety of growth forms from encrusting unilaminar, erect ramose, erect reticulate robust, and erect reticulate delicate, to erect pinnate morphologies. The erect growth forms clearly dominate, and bryozoans become more robust in the upper level of the profiles. The distribution pattern of bryozoan growth forms indicates gradual shallowing in the profiles supporting the assumption of a transgressive-regressive cycle in the Finis Shale. Bryozoan richness, abundance, and ??-diversity increase toward the top of the profiles. Palaeobiogeographic relations of the Finis Shale bryozo-ans are mostly restricted to the American realm, with some connections to the Penn-sylvanian of Europe.

Automated summary

An exceptionally well-preserved bryozoan fauna from the Finis Shale Member in Texas, USA is described. Nineteen bryozoan species were identified, including two new species. The growth forms of bryozoans varied in different locations along the profiles, with erect forms dominating. The profiles indicate a gradual shallowing, and bryozoan richness and diversity increase towards the top. The paleobiogeographic relations of the bryozoans are primarily restricted to the American realm, with some connections to Pennsylvanian of Europe.