THE IDENTITY AND REPRODUCTIVE STRUCTURES OF A MISPLACED SOLENOPORA (RHODOPHYCOPHYTA) FROM THE ORDOVICIAN OF SOUTHWESTERN OHIO AND EASTERN INDIANA1

A study of certain fossil, limestone-forming algae in upper Ordovician beds (Elkhorn and Whitewater Formations of the Richmond Subseries of the Cincinnati Series) in southwestern Ohio and adjacent eastern Indiana culminated with the conclusion that an organism originally described as a sponge, and later placed in the genus Girvanella Nicholson and Etheridge (Cyanochloronta), should in fact be transferred to the genus Solenopora Dybowski (Rhodophycophyta), A calcified reproductive layer was discovered in one of the specimens sectioned. These structures are interpreted as either sporangia or as sporangial chambers, and occur in a sorus rather than a conceptacle type of arrangement. This find has an important bearing on the phylogenetic history of the Solenoporaceae.     

Ordovician and Silurian coralline red algae

Solenopora gotlandica Rothpletz, hitherto placed in the Solenoporaceae Pia, is locally common in the mid-Silurian of Gotland and Wales. It possesses small cells, radial monomerous thallus organization, trichocytes, and sporangia arranged in irregular sori. Solenopora gotlandica is not congeneric with S. spongioides , the type species of Solenopora. It closely resembles the extant coralline red alga Sporolithon Heydrich. S. gotlandica is here transferred to Craticula gen. nov., and Craticula is placed in the Craticulaceae fam. nov., which morphologically closely resembles the Mesozoic-Cenozoic family Sporolithaceae. The Craticulaceae is placed in the extant rhodophyte order Corallinales. Middle-Late Ordovician Petrophyton kiaeri Høeg resembles Late Ordovician Solenopora richmondense Blackwell et al. , which has sporangia in calcified compartments arranged in sori. These fossils may be craticulaceans. The apparent gap in the fossil record between Silurian Craticula and Cretaceous Sporolithon favours separation of these genera at family level. However, future work may demonstrate that the Craticulaceae is a junior synonym of the Sporolithaceae. Recognition of the Craticulaceae extends the earliest record of the Corallinales from Cretaceous to Silurian, and possibly Ordovician.     

A new name for Triassic algal species <Emphasis Type="Italic">Solenopora concentrica</Emphasis> Senowbari-Daryan,Link &; Isintek 2006

The Triassic algal species Solenopora concentrica Senowbari-Daryan, Link & Isintek (2006) is renamed to S. isoconcentrica.     

Solenopora Is A Chaetetid Sponge, Not An Alga

For over one hundred years the Ordovician fossil Solenopora Dybowski has been widely considered to be a calcified red alga. The type species, Solenopora spongioides , consists of tubes with longitudinally flexuous walls, lobate-petaloid cross-sections 30–175 μm across with septal projections, and sporadic cross-partitions. This internal micromorphology is not characteristic of calcified red algae, but is consistent with the original interpretation of Solenopora as a chaetetid, and with subsequent recognition of chaetetids as sponges. Solenopora is widely misidentified in Silurian and younger rocks. Removal of Solenopora from the algae underscores the need to comprehensively reassess the palaeoecological and phylogenetic significance of numerous disparate Ordovician–Miocene fossils currently classed as solenoporaceans.