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Cauca bayuiana
From Fensome et al., 2019:
Cauca bayuiana Mantle, 2009b, p.102,103, pl.9, figs.1–9; text-fig.2. Holotype: Mantle, 2009b, pl.9, fig.3. Age: Callovian.
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Original description: [Mantle, 2009b, p. 102-103]:
Cauca bayuiana sp. nov.
Plate 9, Figs 1-9; Text-fig. 2
Diagnosis: Cysts chorate, acavate; broadly ellipsoidal to ovoidal; with numerous elongate, hollow spines, mostly disposed about the apices but probably abraded preferentially from central portions of the cyst. Cyst wall 2-layered; scabrate to sparsely granulate; layers appressed unless spines formed from outer Iayer. Paratabulation partially expressed by low, sinuous ridges; paratabulation formula indeterminate. Paracingulum prominent, with membranous flanges developed along anterior and posterior margins. Archeopyle epicystal.
Description: The elongate, hollow spines, situated mainly about the apices, are the most noticeable feature of this small ovoidal dinoflagellate cyst. They are composed of the thin periphragm and vary from blunt to pointed. The apical spines are slightly finer and shorter (3-9 pm long) than those attached antapically (5-14 um long) and are typically well-spaced but may also occur in small groups of up to 3 spines. The number of spines is highly variable (due to preservational factors) with 0-9 observed around the apex and 8-14 antapically. Smaller, hollow or solid, intratabular spines (1-3 um long) occur on both the epi- and hypocyst of some specimens, whilst others possess parasutural spines in both gonal and intergonal locations (although these are mostly restricted to the hypocyst). The archeopyle is epicystal (Type tAtP). The compound operculum is commonly free but may remain attached ventrally. Isolated epicysts were not encountered. The hypocyst is readily distinguished from the smaller epicyst by its more prominent paracingular flange (2-5 um wide) and long antapical spines. The pre- and postcingular parasutures, indicated by low sinuous ridges, are usually more conspicuous on the hypocyst. However, the folded and fragmented nature of the periphragm precludes detailed elucidation of the paratabulation formula.
Dimensions (35 specimens): Length of cyst (excluding spines) 30 (35) 42 um; width of cyst at paracingulum 24 (28) 30 um; length of apical spines 3 (5) 9 um; length of antapical spines 5 (9) 14 um; thickness of cyst wall 0.5 um.
Holotype: Slide no.2, EF K21/4. CPC no. 39169; Pl. 9, Fig. 3. Length of cyst (excluding spines) 40 um; width of cyst at paracingulum 27 pm; thickness of cyst wall 0.5 um; length of apical spines 4 (6) 7 um; length of antapical spines 7 (9) 11 um.
Type locality: Timor Sea, Bayu-Undan Field, Bayu-4, core at 3090.3 m (Elang Formation).
Etymology: Referring to the well (Bayu-4) in which the holotype was located.
Remarks: A small cyst with a closely appressed periphragm and endophragm, Cauca bayuiana sp. nov., is easily overlooked due to its diaphanous nature and commonly highly degraded or fragmented form.
Comparison: This species is readily distinguished from the type species Cauca parva (ALBERTI) DAVEY & VERDIER 1971 by its thinner endophragm; more numerous, shorter, and straighter spines, mostly situated about the poles; and the presence of very short, hollow or solid, nontabular spines on the epicyst and hypocyst. Furthermore, C. bayuiana is generally longer than wide, whilst the opposite applies to C. parva. Superficially similar species of Hystrichodinium DEFLANDRE emend. CLARKE & VERDIER 19677 (pp. 37-38) are readily separable by their precingular rather than epicystal archeopyles. Luehndea spinosa MORGENROTH 1970 (p. 347; pL.9, figs 1-4) is distinguished by its distinct parasutural crests delimiting a clear paratabulation pattern; the consistent presence of long spines inserted at gonal points along the posterior margin of the paracingulum; and the consistent solidity of its spines.
Local occurrence: Elang Formation; Ternia balmei Interval Zone (Subzone TB1) through Voodooia tabwlata Interval Zone (Subzone VT5); rare to common.
Cauca bayuiana Mantle, 2009b, p.102,103, pl.9, figs.1–9; text-fig.2. Holotype: Mantle, 2009b, pl.9, fig.3. Age: Callovian.
---------------------------------------------------------------------------------------------------
Original description: [Mantle, 2009b, p. 102-103]:
Cauca bayuiana sp. nov.
Plate 9, Figs 1-9; Text-fig. 2
Diagnosis: Cysts chorate, acavate; broadly ellipsoidal to ovoidal; with numerous elongate, hollow spines, mostly disposed about the apices but probably abraded preferentially from central portions of the cyst. Cyst wall 2-layered; scabrate to sparsely granulate; layers appressed unless spines formed from outer Iayer. Paratabulation partially expressed by low, sinuous ridges; paratabulation formula indeterminate. Paracingulum prominent, with membranous flanges developed along anterior and posterior margins. Archeopyle epicystal.
Description: The elongate, hollow spines, situated mainly about the apices, are the most noticeable feature of this small ovoidal dinoflagellate cyst. They are composed of the thin periphragm and vary from blunt to pointed. The apical spines are slightly finer and shorter (3-9 pm long) than those attached antapically (5-14 um long) and are typically well-spaced but may also occur in small groups of up to 3 spines. The number of spines is highly variable (due to preservational factors) with 0-9 observed around the apex and 8-14 antapically. Smaller, hollow or solid, intratabular spines (1-3 um long) occur on both the epi- and hypocyst of some specimens, whilst others possess parasutural spines in both gonal and intergonal locations (although these are mostly restricted to the hypocyst). The archeopyle is epicystal (Type tAtP). The compound operculum is commonly free but may remain attached ventrally. Isolated epicysts were not encountered. The hypocyst is readily distinguished from the smaller epicyst by its more prominent paracingular flange (2-5 um wide) and long antapical spines. The pre- and postcingular parasutures, indicated by low sinuous ridges, are usually more conspicuous on the hypocyst. However, the folded and fragmented nature of the periphragm precludes detailed elucidation of the paratabulation formula.
Dimensions (35 specimens): Length of cyst (excluding spines) 30 (35) 42 um; width of cyst at paracingulum 24 (28) 30 um; length of apical spines 3 (5) 9 um; length of antapical spines 5 (9) 14 um; thickness of cyst wall 0.5 um.
Holotype: Slide no.2, EF K21/4. CPC no. 39169; Pl. 9, Fig. 3. Length of cyst (excluding spines) 40 um; width of cyst at paracingulum 27 pm; thickness of cyst wall 0.5 um; length of apical spines 4 (6) 7 um; length of antapical spines 7 (9) 11 um.
Type locality: Timor Sea, Bayu-Undan Field, Bayu-4, core at 3090.3 m (Elang Formation).
Etymology: Referring to the well (Bayu-4) in which the holotype was located.
Remarks: A small cyst with a closely appressed periphragm and endophragm, Cauca bayuiana sp. nov., is easily overlooked due to its diaphanous nature and commonly highly degraded or fragmented form.
Comparison: This species is readily distinguished from the type species Cauca parva (ALBERTI) DAVEY & VERDIER 1971 by its thinner endophragm; more numerous, shorter, and straighter spines, mostly situated about the poles; and the presence of very short, hollow or solid, nontabular spines on the epicyst and hypocyst. Furthermore, C. bayuiana is generally longer than wide, whilst the opposite applies to C. parva. Superficially similar species of Hystrichodinium DEFLANDRE emend. CLARKE & VERDIER 19677 (pp. 37-38) are readily separable by their precingular rather than epicystal archeopyles. Luehndea spinosa MORGENROTH 1970 (p. 347; pL.9, figs 1-4) is distinguished by its distinct parasutural crests delimiting a clear paratabulation pattern; the consistent presence of long spines inserted at gonal points along the posterior margin of the paracingulum; and the consistent solidity of its spines.
Local occurrence: Elang Formation; Ternia balmei Interval Zone (Subzone TB1) through Voodooia tabwlata Interval Zone (Subzone VT5); rare to common.