. Bulletin of the Natural Histort Museum. Geology series. 76 M. RUTA. M'4 B Fig. 11 Domfmnria pissoteiisis Cripps & Daley. Middle Ordovician, Llandeilo, Pissot Formation, France. Schematic reconstruction of external aspect. A, dorsal view. B, ventral view (redrawn and modified after Cripps & Daley, 1994). 1. According to the reconstruction provided by Cripps & Daley (1994), Domfrontia possesses almost straight lateral thecal mar- gins. As a result, the anal opening is approximately as wide as the theca. Proportions and relative lengths of the marginalia of Domfrontia are similar to
. Bulletin of the Natural Histort Museum. Geology series. 76 M. RUTA. M'4 B Fig. 11 Domfmnria pissoteiisis Cripps & Daley. Middle Ordovician, Llandeilo, Pissot Formation, France. Schematic reconstruction of external aspect. A, dorsal view. B, ventral view (redrawn and modified after Cripps & Daley, 1994). 1. According to the reconstruction provided by Cripps & Daley (1994), Domfrontia possesses almost straight lateral thecal mar- gins. As a result, the anal opening is approximately as wide as the theca. Proportions and relative lengths of the marginalia of Domfrontia are similar to those of Beryllia, but differ remarkably from those of Jidiaecarpus. The convexity of the lateral thecal margins of Jidiaecarpus is somewhat intermediate between that of Beryllia and that of Domfrontia. 2. The zygal process of M'^ in Domfrontia is comparatively wider and shorter than that of both Beryllia and Juliaecarpus. Likewise, the preserved part of the posterior zygal plate of Domfrontia suggests that this plate is stouter in this ankyroid than in the other two genera. 3. The styloid and ossicles of Domfrontia are shaped like bulges with a subelliptical to subcircular outline and carry a poorly defined median longitudinal keel with a semicircular to parabolic profile. 4. The ventral projection of M^ is expanded posteriorly in Domfrontia, but not in Beryllia and only to a very limited extent in Juliaecarpus. The number of marginal plates in such genera as Juliaecarpus. Reticulocarpos, Beryllia and Domfrontia, as well as their relative position and shape, gives support to Parsley's (1991, 1997, 1998) suggestion that several lineages within the ankyroids underwent reduction in the number of marginalia through decrease in size and subsequent loss of the rearmost plates. A brief comparison with the ankyroid Nanocarpus dolambii Ubaghs, 1991, from the lower Ordovician of southern France is interesting in this respect (Fig. 12). Except for asymmetries in the thecal frame due to
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