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Gillinia dentata
Holotype. Plate 2, figure 2; GSCA slide no. 51206-08 (¼GSCC slide no. P5205–99I); coordinates 15.1x91.6; EF M55/circle; Nunavut Palaeontology Collection no. NUPB 974; Twosnout creek, Bylot Island. Bylot Island formation.
Etymology. The epithet is from the Latin dentatum, meaning toothed, in reference to the nature of the distal margins of the septa that delineate the paratabulation.
Diagnosis. A species of Gillinia with a generally elongate but occasionally subcircular central body with the tabulation partially delineated by well-developed septa, especially on the lateral margins. Some of the septa mark paraplate boundaries and clearly delineate the paracingulum, but others in the antapical region appear to be penetabular. The septa are up to 3um in height and bear distal serrations that are less than 1um high. Like other species in this genus, the epicyst is much smaller but not as broad as the hypocyst. The surface of the central body is smooth to scabrate.
Comments. Two other species of Gillinia possess septa that are sometimes distally serrate. Gillinia denticulata has a pear- shaped (pyriform) central body, broader septa and serrations on the septa are considerably longer. Like Gillinia denticulata, the outline of the central body of Gillinia pyriformis can be pyriform, rounded or subtriangular. Marshall (1990, 14) described it in part as follows: ‘Lateral margins occasionally nearly straight to convex; usually concave above the equator, convex below this level’. However, the specific epithet implies the outline is pear-shaped or pyriform. The most distinctive features of Gillinia pyriformis are the two ‘domes’ or funnels formed by membranes up to 7–12um high on the lateral epicystal margins. Marshall (1990) also noted that in Gillinia pyrifomis, parasutural ridges, which can be smooth irregular or rarely denticulate, are restricted to the periphery of the central body. The structure and distribution of the septa, especially the two domes formed from membranes, differentiate Gillinia pyriformis from Gillinia dentata.
Size. Holotype: central body length 12um, central body width 13um, septa up to 2um. Range of six specimens: central body length 12–15um, central body breadth 10–13um, paracingulum height 2–4um.
Age. Early Campanian to early Maastrichtian.
Etymology. The epithet is from the Latin dentatum, meaning toothed, in reference to the nature of the distal margins of the septa that delineate the paratabulation.
Diagnosis. A species of Gillinia with a generally elongate but occasionally subcircular central body with the tabulation partially delineated by well-developed septa, especially on the lateral margins. Some of the septa mark paraplate boundaries and clearly delineate the paracingulum, but others in the antapical region appear to be penetabular. The septa are up to 3um in height and bear distal serrations that are less than 1um high. Like other species in this genus, the epicyst is much smaller but not as broad as the hypocyst. The surface of the central body is smooth to scabrate.
Comments. Two other species of Gillinia possess septa that are sometimes distally serrate. Gillinia denticulata has a pear- shaped (pyriform) central body, broader septa and serrations on the septa are considerably longer. Like Gillinia denticulata, the outline of the central body of Gillinia pyriformis can be pyriform, rounded or subtriangular. Marshall (1990, 14) described it in part as follows: ‘Lateral margins occasionally nearly straight to convex; usually concave above the equator, convex below this level’. However, the specific epithet implies the outline is pear-shaped or pyriform. The most distinctive features of Gillinia pyriformis are the two ‘domes’ or funnels formed by membranes up to 7–12um high on the lateral epicystal margins. Marshall (1990) also noted that in Gillinia pyrifomis, parasutural ridges, which can be smooth irregular or rarely denticulate, are restricted to the periphery of the central body. The structure and distribution of the septa, especially the two domes formed from membranes, differentiate Gillinia pyriformis from Gillinia dentata.
Size. Holotype: central body length 12um, central body width 13um, septa up to 2um. Range of six specimens: central body length 12–15um, central body breadth 10–13um, paracingulum height 2–4um.
Age. Early Campanian to early Maastrichtian.