Studies in selected fragilarioid diatoms of potential indicator value from Florida (USA) with notes on the genus Opephora Petit (Bacillariophyceae)

Four araphid diatom taxa were collected from Florida streams and studied with both light microscopy (LM) and scanning electron microscopy (SEM). Three taxa, formerly in the genus Fragilaria LYNGBYE, are here placed in the genus Pseudostaurosira WILLIAMS et ROUND. On the basis of ultrastructure observed by SEM, the remaining taxon is placed in a new genus, Sarcophagodes. At least two of the species referred to Pseudostaurosira may have been confused with species of the genus Opephora PETIT, which may have led to misinterpretation of the ecological characteristics of the latter genus. All the taxa treated here belong to the Family Fragilariaceae GREVILLE as delimited in current classification schemes. Two new combinations Pseudostaurosiropsis geocollegarum (= Fragilaria geocollegarum WITKOWSKI et LANGE-BERTALOT), Pseudostaurosira neoelliptica (= Fragilaria neoelliptica WITKOWSKI) and the new species Pseudostaurosira clavatum are presented herein. Additionally, a new genus, Sarcophagodes, is erected to accommodate the new species S. delicatula. LM and SEM details, as well as criteria delimiting these taxa are discussed. More collections and further analyses are needed to assess the distribution of both Opephora and Sarcophagodes.