Generic limits within the Eupodiscaceae: I. Observations on three unusual species ofCerataulus, with reference to the type species,C. turgidus

Morphological, taxonomic and nomenclatural analysis of species ofOdontella,TrieresandZygoceros(Triceratiaceae, Bacillariophyta) from Anegada Bay (Province of Buenos Aires, Argentina)

“…According to Sims & Witkowski (2012) the Triceratiaceae sensu Round et al (1990) is roughly equivalent to the Eupodiscaceae sensu Simonsen (1979) and includes several genera of ocellate diatoms with poroid, loculate and pseudoloculate valves. Generic limits within the group were summarized by Ross & Sims (1971) as follows: Zygoceros Ehrenberg (1839) with loculate areolae, Odontella Agardh (1832) with poroid areolae and no contorted valves, and Cerataulus Ehrenberg (1844) with loculate areolae and contorted valves.…”

“…Zygoceros was not considered a distinct genus, but was retained in the section Zygocerotae of Odontella by Hoban (1979Hoban ( , 2008, or retained in Odontella without subgenus status by Round et al (1990). More recently Sims & Witkowski (2012) established that Odontella and Zygoceros are poorly defined genera and Ashworth et al (2013) pointed out that Odontella is not monophyletic, erecting a new genus Trieres Ashworth & Theriot based on a morphological and phylogenetic analysis. Additionally, Ashworth et al (2013) consider that defining Zygoceros 'is potentially complicated by Odontella atlantica (Frenguelli) Sar in Sar et al (2007), which has the same loculate valve construction as O. rhombus and O. rhomboides Jahn & Kusber, but has rimoportula immediately adjacent to the ocelli'.…”

“…Analysis of Parodontella calamus (Tempere & Brun) Komura, P. paucispinosa Komura, P. oblique Komura and P. clavigera Komura allow us to add other differential features: the elevations are areolate in Trieres but smoothwalled in Parodontella, and there are two rimoportulae in Trieres but four in Parodontella.Zygoceros is another genus with loculate areolae and ocellate elevations. According toSims & Witkowski (2012) it is poorly constrained and was previously considered a synonym of Odontella(Hoban 1979, Round et al 1990. It differs from Trieres and Parodontella in having elliptic to sub-rhombic valves , with no differentiation into valve face and valve mantle, wider and shorter ocelli-bearing polar elevations, and with shorter external rimoportula tubes.…”