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Odontochitina pilata
Holotype. Plate 4, figure 5; GSCA slide no. P42196-02 (¼GSCC slide no. P5189-15O), 6.0x90.7; EF V/56 circle intersection with V56/4; Nunavut Palaeontology Collection no. NUPB 1015; section 3, Maud Bight, Bylot Island. Bylot Island formation.
Etymology. The epithet is from the Latin pilatus meaning thick, dense, in reference to the thickness and fibrous nature of the endophragm.
Diagnosis. Cyst cornucavate, especially in the vicinity of the antapical horn. Endocyst probably two-layered with thin endophragm and a spongy mesophragm. Pericyst with a short, broad antapical horn and a short or no lateral horn; when present, the latter tends to be conical. Endocyst elongate, closely appressed to pericyst in vicinity of lateral horn. Endophragm up to about 1.5mm thick, dense, fibrous.
Comments. Based on the exquisite plates in Niechwedowicz (2018) of Odontochitina dilatata, we interpret the wall structure of Odontochitina? pilata as also being composed of a thin endophragm, a thick, spongy mesophragm and the periphragm, the latter forming the wall of the pericyst. Odontochitina? pilata is questionably assigned to Odontochitina because it has a considerably reduced or no lateral horn. The nature of the mesophragm in being thick and fibrous is similar to that of Odontochitina dilatata. The thick wall may reflect the cysts’ exposure to challenging environments such as strong wave action or low temperatures.
Size. Holotype: overall length (excluding apical operculum) 68um, overall width (excluding lateral horn) 50um, pericyst length (excluding lateral horn) 48um, pericyst width 46um, endocyst length 48um, endocyst width 46um, lateral horn length 3um, lateral horn width proximally 14um and distally 2um, antapical horn length 17um, antapical horn width proximally 13um and distally 8um. Range of two specimens: overall length (minus apical horn and operculum) 58–68um, overall width 44–50um, pericyst length 44–48um, pericyst width 36um, endocyst length 44–48um, endocyst width 40– 46um, lateral horn length 3–8um; lateral horn width proximally 6um and distally 2um, antapical horn length 19 um, antapical horn width proximally 9–14um and distally 3um.
Age. Coniacian.
Etymology. The epithet is from the Latin pilatus meaning thick, dense, in reference to the thickness and fibrous nature of the endophragm.
Diagnosis. Cyst cornucavate, especially in the vicinity of the antapical horn. Endocyst probably two-layered with thin endophragm and a spongy mesophragm. Pericyst with a short, broad antapical horn and a short or no lateral horn; when present, the latter tends to be conical. Endocyst elongate, closely appressed to pericyst in vicinity of lateral horn. Endophragm up to about 1.5mm thick, dense, fibrous.
Comments. Based on the exquisite plates in Niechwedowicz (2018) of Odontochitina dilatata, we interpret the wall structure of Odontochitina? pilata as also being composed of a thin endophragm, a thick, spongy mesophragm and the periphragm, the latter forming the wall of the pericyst. Odontochitina? pilata is questionably assigned to Odontochitina because it has a considerably reduced or no lateral horn. The nature of the mesophragm in being thick and fibrous is similar to that of Odontochitina dilatata. The thick wall may reflect the cysts’ exposure to challenging environments such as strong wave action or low temperatures.
Size. Holotype: overall length (excluding apical operculum) 68um, overall width (excluding lateral horn) 50um, pericyst length (excluding lateral horn) 48um, pericyst width 46um, endocyst length 48um, endocyst width 46um, lateral horn length 3um, lateral horn width proximally 14um and distally 2um, antapical horn length 17um, antapical horn width proximally 13um and distally 8um. Range of two specimens: overall length (minus apical horn and operculum) 58–68um, overall width 44–50um, pericyst length 44–48um, pericyst width 36um, endocyst length 44–48um, endocyst width 40– 46um, lateral horn length 3–8um; lateral horn width proximally 6um and distally 2um, antapical horn length 19 um, antapical horn width proximally 9–14um and distally 3um.
Age. Coniacian.