PATERINOIDEA Schuchert, 1893

Skovsted, C. B., Knight, I., Balthasar, U. & Boyce, W. D., 2017, Depth related brachiopod faunas from the lower Cambrian Forteau Formation of southern Labrador and western Newfoundland, Canada, Palaeontologia Electronica (Oxford, England: 1990) 17 (15), pp. 1-52 : 43-45

Superfamily PATERINOIDEA Schuchert, 1893 Family PATERINIDAE Schuchert, 1893

Figure 23

Remarks. The brachiopod fauna of the Forteau Formation contain two distinct paterinid species with ventribiconvex shells. One species ( Figure 23.1-5 ) is characterized by a deep, open ventral delthyrium with a vestigial homeodelthidium ( Figure 23.1 ) and a marked change in ventral convexity towards the anterior ( Figure 23.3 ). The identity of this species is not quite clear, although the poorly developed homeodelthidum have been considered characteristic of the genus Paterina Beecher, 1891 ( Williams et al., 1998, p. 245). A closely comparable specimen from the lower Cambrian of Labrador identified as Paterina labradorica ( Billings, 1861) was illustrated by Williams et al. (1998, plate 11, figure 5). The ventral valve of the second species ( Figure 23.6-9 ) is strongly and uniformly convex ( Figure 23.8 ) and the ventral delthyrium is closed by a well-developed, convex homeodelthidium ( Figure 23.6 ). The development of the ventral homeodelthidium is considered to be characteristic of the genus Micromitra Meek, 1873 ( Williams et al., 1998, p. 245). Specimens of a broadly comparable morphology from North-East Greenland are referred to as Micromitra bella ( Billings, 1872) by Skovsted and Holmer (2005).

At the present time, Laurentian species of Paterina and Micromitra are poorly known and we refrain from specific identifications. Our collections contain abundant and well-preserved specimens of both species from acid residues and in hand specimen, and a full taxonomic treatment, including investigation of relevant type material, is beyond the scope of the current presentation. The two species are treated here as Paterina sp. and Micromitra sp. , respectively, based on the characteristic differences in morphology of the posterior margin of the ventral valve.

In our collections Micromitra sp. is represented by 559 ventral and 264 dorsal valves (see Appendix 1 and 2) from many samples collected from the archaeocythid reef facies to distal shelf facies. The species is very widely distributed in the study area and ranges throughout the sampled stratigraphic interval of the Forteau Formation although it is usually represented by relatively few specimens in each sample (assemblages 1-3). Paterina sp. is represented by 667 ventral, 193 dorsal valves, and a single articulated specimen (see Appendix 1 and 2) from the achaeocyathid reef facies of the Upper limestone of both southern Labrador and western Newfoundland (both part of the HST) where the species is often represented by large numbers of co-occurring specimens (assemblage 2).

LINGULIFORMEA incertae sedis

Genus SETATELLA Skovsted, Streng, Knight, and Holmer, 2010

Type species. Setatella significans Skovsted, Streng, Knight, and Holmer, 2010 .

Figures

FIGURE 23. Paterinids from the Forteau Formation. 1-5, Paterina sp. 1-3, ventral valve NFM F-2555 from sample ICS1548; 1, posterior view; 2, external view; 3, lateral view. 4-5, Dorsal valve NFM F-2556 from sample LLQ3-5; 4, posterior view; 5, external view. 6-9, Micromitra sp. 6-8, Ventral valve NFM F-2557 from sample MSM-11; 6, posterior view; 7, external view; 8, lateral view. 9, Dorsal valve NFM F-2558 from sample MSM-7; oblique posterolateral view. All scalebars equal 500 µm.