Clitellate cocoons in freshwater deposits since the Triassic

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Abstract
Previously enigmatic, ovoid to sac‐like fossils of organic, acid resistant substance which are common components of leaf cuticle and megaspore assemblages in limnic and terrestrial palaeoen‐ vironments are identified as cocoons of clitellates. They have been recorded for a long time by palaeobotanists and palynologists, particularly in the Mesozoic, and have been variously interpreted as being of megaspore, seed, or algal origins, although convincing homologues were lacking. The fossils agree in basic wall construction with cocoons of clitellates, and particularly with certain members of the Hirudinea. A clitellate affinity is further supported by a possible segmentation, their consistently non‐marine occurrence, evidence for predation, and an example of amber‐like inclusion of alien structures in the cocoon wall which indicates the presence of secretion. As a consequence of the new interpretation, two taxa established under the botanical code of nomenclature for such fossils, namely Burejospermum crassitestum Krassilov and Dictyoth‐ ylakos pesslerae Horst, are transferred to the zoological kingdom and classified under Clitellata (phylum Annelida), along with two new taxa, D. spitsbergensis sp.n. andPilothylakospilosus gen. et sp.n. With the present interpretation a consistent Mesozoic record is documented for clitellates, a group of softbodied, basically freshwater and terrestrial animals of which there was until now nearly no fossil record.

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