SMALL-SUBUNIT RIBOSOMAL-RNA GENE-SEQUENCES FROM REPRESENTATIVES OF SELECTED FAMILIES OF THE GIGARTINALES AND RHODYMENIALES (RHODOPHYTA) .2.RECOGNITION OF THE HALYMENIALES ORD NOV

Nucleotide sequences of the nuclear, small-subunit ribosomal RNAs, as inferred from polymerase chain reaction amplified products, are introd uced for representatives of the Dumontiaceae, Endocladiaceae, Halymeni aceae, and Kallymeniaceae of the order Cryptonemiales sensu Kylin, the Mychodeaceae, Phyllophoraceae, Schizymeniaceae, and Sebdeniaceae of t he order Gigartinales sensu Kylin, and the Lomentariaceae and Rhodymen iaceae of the order Rhodymeniales. The new sequences are included in p hylogenetic analyses incorporating previously published sequences from additional families of the orders Ahnfeltiales, Ceramiales, Gigartina les, Gracilariales, Palmariales, Plocamiales, and Rhodymeniales. We us ed the molecular data to test the validity of the taxonomic merger of the orders Gigartinales and Cryptonemiales that was proposed by G.T. K raft and P.A. Robins in 1985. With only two exceptions (the families H alymeniaceae and Sebdeniaceae), phylogenetic analyses of the SSU data support a monophyletic origin for a combined Gigartinales-Cryptonemial es. We therefore propose the resurrection of a redefined Cryptonemiale s to consist, at this time, of only the Halymeniaceae and Sebdeniaceae . Because virtually no elements of the original or recent definitions of the Cryptonemiales survive in the characterization of this taxon, w e followed procedures allowed by the International Code of Botanical N omenclature to designate it the Halymeniales ord.nov. Analysis of mole cular data further indicates that the Rhodymeniales is a monophyletic assemblage distinct from both the Gigartinales and Halymeniales; it sh ould not be merged with the Gigartinales as is occasionally suggested.