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Rhaxellid sponge microscleres from the Portlandian of Dorset, UK
Author(s) -
Haslett Simon K.
Publication year - 1992
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/gj.3350270404
Subject(s) - sedimentary depositional environment , sponge , paleontology , assemblage (archaeology) , genus , geology , geography , ecology , biology , structural basin
Three previously described species and two new species of rhaxellid microscleres, Rhaxella winspitensis sp. nov. and R. elongata sp. nov., are described from cherts collected from the Cherty Series of the Portlandian of Dorset. The classification of Rhaxella is reviewed, retaining the genus within the family Geodiidae Gray. The results of this study suggest that three time‐dependent rhaxellid assemblages can be recognized which, despite being restricted to certain depositional environments, may have biostratigraphic applications. A Portlandian assemblage described here is species‐rich in comparison with known Oxfordian‐Kimmeridgian assemblages. Bajocian‐Callovian assemblages contain only R. sorbyana. The increased faunal diversity with time is speculatively described by an evolving Rhaxella lineage.