Shaleriidae Williams, 1965

Musteikis, Petras & Cocks, L. Robin M., 2004, Strophomenide and orthotetide Silurian brachiopods from the Baltic region, with particular reference to Lithuanian boreholes, Acta Palaeontologica Polonica 49 (3), pp. 455-482 : 465

Family Shaleriidae Williams, 1965 Genus Shaleria Caster, 1939

Remarks.—The type species of Shaleria , by the original designation of Caster (1939: 33), is Strophomena gilpeni Dawson, 1881 , whose type locality is the Lower Devonian Stonehouse Formation of Arisaig, Nova Scotia, Canada. This type species was revised from new collections by Harper (1973). The genus was revised by Harper and Boucot (1978: 161), who also revised the family, in which they included only two genera, Shaleria , with three subgenera S. ( Shaleria ), S. ( Janiomya ) Havliček, 1967, and S. ( Protoshaleria ) subgen. nov., and Shaleriella gen. nov. Subsequent revision by Cocks and Rong (2000), put S. ( Protoshaleria ) within the synonomy of S. ( Shaleria ), and included Shaleria and Shaleriella as the only two separate genera within the family. The type species of Shaleriella is S. delicata Harper and Boucot, 1978 , from the Silurian of Gotland, Sweden (see below under S. (S.) ezerensis ). Harper and Boucot (1978: 123, 160–161) distinguished Shaleria from their new genus Shaleriella on (i) the geniculate profile of the latter, as opposed to the gently convex profile of the former, (ii) the lack of dorsal “brace plates” (termed here dorsal side septa) in the latter, and (iii) the “uniformly costellate” ornament of Shaleria . The latter is puzzling, since Harper (1973: 39), in his revision of the type species of Shaleria , described its ornament as “some specimens unequally parvicostellate; others parvicostellate with inserted costellae separated by interspaces of about the same width, which may bear a single fine costella,” and these observations are borne out by his illustrations, and thus the ornamental distinction between the two genera is negated. The dorsal side septa, which are often curved in a bow shape in their posterior parts, are more difficult in assessing generic importance and differentiation. Harper and Boucot (1978: 34) illustrate only two dorsal interiors of S. delicata , one of which (fig. 21 in their paper) lacks side septa and the other of which (fig. 22) possesses them, although they are weakly developed in that specimen. The geniculate profile is a genuine difference, and that is consistently linked with a valve outline which is squarer anteriorly (a feature not mentioned by Harper and Boucot). However, we do not consider those two features alone as a firm basis for good generic differentiation, but they appear to be consistent between populations and thus we assess Shaleriella here not as a separate genus but as a subgenus of Shaleria . Havliček (1967: 174) erected Janiomya as a new independent genus which differed from Shaleria only in the lack of “strong subparallel plates” in the dorsal valve. Since Havliček only illustrated a single dorsal interior of Janiomya parallelomya , the type species of his new genus, from the Pridoli of Bohemia, it is difficult to be certain of its status because of the wide range of variation that we have seen in the strength of these plates in large populations of, for example, Shaleria ornatella from the Welsh Borderland, and we follow Cocks and Rong (2000) in provisionally placing Janiomya as a subgenus of Shaleria until larger collections of material become available from Bohemia. Thus, to summarise, Shaleria is now considered to be the only genus within the family Shaleriidae , and includes the three subgenera S. ( Shaleria ), S. ( Janiomya ) and S. ( Shaleriella ).