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Spiniferites scalenus
Spiniferites scalenus Guerstein et al., 2008, p.79, pl.2, figs.3–8; pl.3, figs.6–12.
Holotype: Guerstein et al., 2008, pl.2, figs.3–4.
Age: middle Eocene to earliest Oligocene.
Original description (Guerstein et al., 2008):
Spiniferites scalenus sp. nov. (Pl. 2, figs 3–8; Pl. 3, figs 6–12)
Derivation of name. From the Latin ‘scalenus’, meaning ‘unequal’, in reference to the uneven height of the sutural crests.
Diagnosis. A species of Spiniferites with an elongate central body, bearing relatively short, trifurcate gonal processes, joined at their base by sutural crests of variable height. The crests vary even within a single specimen, from simple, sutural low ridges to high, membranous septa, almost reaching the distal expansion of the processes.
Holotype. Plate 2, figs 3–4. Cerro Águila section, 0.5 m above the base. UNS CA1-P34662-1: 48/108 EF: H 49/3.
Locality and horizon. Cerro Águila Section, northeast Tierra del Fuego, Argentina. Lower part of the Cabo Peña Formation; Upper Eocene.
Description. Chorate cysts with an elongate central body bearing trifurcate gonal processes. Most of the processes are short, membranous, subtriangular in cross-section, with a central solid stem. Terminations are usually trifurcate with bifurcate ends. Generally, the processes are connected at their bases by high membranous septa of variable height. Specimens with the highest crests do not have stems but simply a trifurcate expansion at the gonal junctions of septa (Pl. 3, figs 6, 8). Septa margins are irregularly undulate to denticulate (Pl. 3, figs 5–12). The endophragm is smooth and the periphragm is microgranular to granular. The archaeopyle is precingular, type P, resulting from the loss of the 3’’ plate, and with a free operculum. Paratabulation gonyaulacoidean, defined by membranous septa and/or low sutural ridges and by the gonal processes. Plates 1’ and 4’ are generally fused (Pl. 3, figs 6, 8).
Dimensions. Holotype – central body width 38 µm; central body length 47 µm; height of sutural septa 5 µm. Range of ten specimens – central body width 28–45 µm; central body length 35–47 µm; height of sutural septa 1–7 µm.
Occurrence. Río de la Turba section, RT6, RT10; Cabo Peñas section, CP1–CP2; Cerro Águila section, CA1–CA6; Río Candelaria section, R1–R2, R4–R5.
Remarks. The new species differs from other species of Spiniferites by having crests of variable height. Several of the observed specimens have septa rising up to the base of the furcate process terminations. In such cases they resemble species of the genus Impagidinium (Pl. 2, figs 3–4; Pl. 3, figs 6, 8). Because of the presence of some processes in all specimens observed, this species has been included in Spiniferites.
Holotype: Guerstein et al., 2008, pl.2, figs.3–4.
Age: middle Eocene to earliest Oligocene.
Original description (Guerstein et al., 2008):
Spiniferites scalenus sp. nov. (Pl. 2, figs 3–8; Pl. 3, figs 6–12)
Derivation of name. From the Latin ‘scalenus’, meaning ‘unequal’, in reference to the uneven height of the sutural crests.
Diagnosis. A species of Spiniferites with an elongate central body, bearing relatively short, trifurcate gonal processes, joined at their base by sutural crests of variable height. The crests vary even within a single specimen, from simple, sutural low ridges to high, membranous septa, almost reaching the distal expansion of the processes.
Holotype. Plate 2, figs 3–4. Cerro Águila section, 0.5 m above the base. UNS CA1-P34662-1: 48/108 EF: H 49/3.
Locality and horizon. Cerro Águila Section, northeast Tierra del Fuego, Argentina. Lower part of the Cabo Peña Formation; Upper Eocene.
Description. Chorate cysts with an elongate central body bearing trifurcate gonal processes. Most of the processes are short, membranous, subtriangular in cross-section, with a central solid stem. Terminations are usually trifurcate with bifurcate ends. Generally, the processes are connected at their bases by high membranous septa of variable height. Specimens with the highest crests do not have stems but simply a trifurcate expansion at the gonal junctions of septa (Pl. 3, figs 6, 8). Septa margins are irregularly undulate to denticulate (Pl. 3, figs 5–12). The endophragm is smooth and the periphragm is microgranular to granular. The archaeopyle is precingular, type P, resulting from the loss of the 3’’ plate, and with a free operculum. Paratabulation gonyaulacoidean, defined by membranous septa and/or low sutural ridges and by the gonal processes. Plates 1’ and 4’ are generally fused (Pl. 3, figs 6, 8).
Dimensions. Holotype – central body width 38 µm; central body length 47 µm; height of sutural septa 5 µm. Range of ten specimens – central body width 28–45 µm; central body length 35–47 µm; height of sutural septa 1–7 µm.
Occurrence. Río de la Turba section, RT6, RT10; Cabo Peñas section, CP1–CP2; Cerro Águila section, CA1–CA6; Río Candelaria section, R1–R2, R4–R5.
Remarks. The new species differs from other species of Spiniferites by having crests of variable height. Several of the observed specimens have septa rising up to the base of the furcate process terminations. In such cases they resemble species of the genus Impagidinium (Pl. 2, figs 3–4; Pl. 3, figs 6, 8). Because of the presence of some processes in all specimens observed, this species has been included in Spiniferites.