Initiation of a species-level fossil diatom image database

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During 2022, I focused again on the Eocene, particularly Mors (Jutland) which contains a number of dubious Rhizosolenia spp. that appear to belong to Proboscia. One of these species, R. dubia, had a seemingly complicated life cycle - published illustrations of two specimens had shown combination cells involving Pseudopyxilla dubia and an unnamed Rhizosolenia species. Our results demonstrated that the latter was a Proboscia species and despite observing hundreds of specimens, no combination cells were seen. We named this species, Proboscia pinocchioi, due to its unique long middle spinula. Some specimens were also seen with claspers and contiguous areas on the valve base - this is the oldest record of claspers found to date, and proof that some fossil Proboscia were capable of making short chains (Abe & Jordan, 2022). Unlike the ridged forms of the P. cretacea lineage, P. pinocchioi combines characters of the two subsequent lineages, the P. barboi lineage (with large polar spines) and P. alata lineage (with claspers). Other species in Mors (R. clavigera, R. fragilis, R. juetlandica, R. sp. 1, R. sp. 3) will also need transferring to Proboscia. Further research was also conducted on other Eocene sites. Notably, Proboscia spp. with serrated edges were observed in samples from the Central Arctic, California, Barbados, Israel and Oamaru. While another Proboscia sp. in the Central Arctic formed mats. There were also clear differences between the Middle Eocene assemblages of the northern and southern hemispheres, a trend which was also apparent in Early Oligocene assemblages.