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Spiniferites ristingensis
Spiniferites ristingensis Head, 2007, p.1011–1012, figs.8.c–l.
Holotype: Head, 2007, figs.8.c–g.
Age: late Pleistocene (Eemian).
Original description (Head, 2007)
Diagnosis. A species of Spiniferites having an ovoid central body, with or without a short apical protuberance, and bearing membranous gonal processes joined by low sutural crests. Some processes are distally expanded to form irregularly polygonal platforms. The central body wall is formed of two wall layers of similar thickness. The pedium is smooth, and the tegillum forms small, densely distributed blisters and hollow undulations over the surface. The processes and sutural crests are formed of the tegillum and are distinctly bilayered. The surface of the processes and sutural crests appears granulate.
Types. Holotype: depth 57 cm, slide 1; England Finder reference P8/1. Fig. 8c–g. ROMP 57997. Paratype: depth 57 cm, slide 1; England Finder reference H49/2. Fig. 8h–l. ROMP 57997.
Description. A spiniferate cyst having an ovoid central body. A short apical protuberance up to 1.0 µm is sometimes present, as on the holotype (Fig. 8c–g). The central body wall is bilayered. The pedium is smooth, and the tegillum forms small, densely distributed blisters and hollow undulations over the surface, a feature clearly seen in transverse optical section (Fig. 8d). The blisters have a maximum diameter of about 1.8 µm. In plan view, the wall may appear granular, with dots (less than 0.3 µm wide and mostly spaced 1.0 µm or less apart) representing points of contact between pedium and tegillum. The pedium and tegillum are each less than 0.3 µm thick, and the wall is between 1.0 and 1.8 µm in total thickness. Processes are gonal and membranous.
They are joined by sutural crests that are mostly low (less than 2 µm), but may be higher where processes are closely adjacent, especially along the cingulum. Processes are either truncated distally or expanded to form irregularly polygonal platforms, some of which typically extend outwards at right angles to the process stem. The apex may have one or more narrow, spine-like processes (Fig. 8f). The processes and sutural crests are formed of the tegillum and are distinctly bilayered, with a space of up to about 0.5 µm between layers caused by the undulating nature of the tegillum. The surface of the processes and sutural crests appears granulate. Claustra occasionally occur on the processes and sutural crests, and occur on the cingular processes of the holotype. The sutural crests indicate a typical gonyaulacoid tabulation, with a descending cingulum that is displaced about 2.5 times its width. The sulcal plates (especially the adcingular margin of 1P) are sometimes faintly discernible by subtle lineations in the wall ornament. The archeopyle is precingular, type P(3”), and a low (c. 1.0 µm) sutural crest occurs along the archeopyle margin (Fig. 8g). The operculum is monoplacate and free.
Dimensions: Holotype: central body length 42 µm; maximum process length 14 µm. Range: central body length 39(43.0)49 µm; maximum process length 11(12.9)17 µm. Fourteen specimens were measured.
Etymology. Named after the type locality.
Comparison. Spiniferites ristingensissp. nov. is distinguished by its membranous processes and by the wall structure of the central body. Spiniferites ludhamensis Head, 1996b, from the upper Pliocene of eastern England, has a similar wall structure but hollow, non-membranous processes and hollow sutural crests. Spiniferites delicatus Reid, 1974, from modern sediments of the British Isles, has processes of similar shape but connected by high sutural crests, and a central body wall structure characterized by a pedium with radial fibres and a thin granular tegillum whose surface appears microgranular to microreticulate. Spiniferites delicatus also differs in having a reduced archeopyle.
Occurrence. Presently known only from the Eemian of the Baltic region; occurring persistently but in low numbers hrough zones RKDf 2 and 3 (reaching 3.7 % in RKDf 3) at Ristinge Klint, Denmark; in low numbers at Mommark, Denmark (M. J. Head, unpub. data); and sporadically and in low numbers at Lizce, Poland (as Spiniferites sp. 1 in Head et al. 2005). This species appears to tolerate reduced salinities judging from its early presence at the base of subzone RKDf 2a, although surface-water salinities nevertheless exceeded about 15 psu and bottom waters exceeded about 22 psu at this time (see Section 10.c).
Holotype: Head, 2007, figs.8.c–g.
Age: late Pleistocene (Eemian).
Original description (Head, 2007)
Diagnosis. A species of Spiniferites having an ovoid central body, with or without a short apical protuberance, and bearing membranous gonal processes joined by low sutural crests. Some processes are distally expanded to form irregularly polygonal platforms. The central body wall is formed of two wall layers of similar thickness. The pedium is smooth, and the tegillum forms small, densely distributed blisters and hollow undulations over the surface. The processes and sutural crests are formed of the tegillum and are distinctly bilayered. The surface of the processes and sutural crests appears granulate.
Types. Holotype: depth 57 cm, slide 1; England Finder reference P8/1. Fig. 8c–g. ROMP 57997. Paratype: depth 57 cm, slide 1; England Finder reference H49/2. Fig. 8h–l. ROMP 57997.
Description. A spiniferate cyst having an ovoid central body. A short apical protuberance up to 1.0 µm is sometimes present, as on the holotype (Fig. 8c–g). The central body wall is bilayered. The pedium is smooth, and the tegillum forms small, densely distributed blisters and hollow undulations over the surface, a feature clearly seen in transverse optical section (Fig. 8d). The blisters have a maximum diameter of about 1.8 µm. In plan view, the wall may appear granular, with dots (less than 0.3 µm wide and mostly spaced 1.0 µm or less apart) representing points of contact between pedium and tegillum. The pedium and tegillum are each less than 0.3 µm thick, and the wall is between 1.0 and 1.8 µm in total thickness. Processes are gonal and membranous.
They are joined by sutural crests that are mostly low (less than 2 µm), but may be higher where processes are closely adjacent, especially along the cingulum. Processes are either truncated distally or expanded to form irregularly polygonal platforms, some of which typically extend outwards at right angles to the process stem. The apex may have one or more narrow, spine-like processes (Fig. 8f). The processes and sutural crests are formed of the tegillum and are distinctly bilayered, with a space of up to about 0.5 µm between layers caused by the undulating nature of the tegillum. The surface of the processes and sutural crests appears granulate. Claustra occasionally occur on the processes and sutural crests, and occur on the cingular processes of the holotype. The sutural crests indicate a typical gonyaulacoid tabulation, with a descending cingulum that is displaced about 2.5 times its width. The sulcal plates (especially the adcingular margin of 1P) are sometimes faintly discernible by subtle lineations in the wall ornament. The archeopyle is precingular, type P(3”), and a low (c. 1.0 µm) sutural crest occurs along the archeopyle margin (Fig. 8g). The operculum is monoplacate and free.
Dimensions: Holotype: central body length 42 µm; maximum process length 14 µm. Range: central body length 39(43.0)49 µm; maximum process length 11(12.9)17 µm. Fourteen specimens were measured.
Etymology. Named after the type locality.
Comparison. Spiniferites ristingensissp. nov. is distinguished by its membranous processes and by the wall structure of the central body. Spiniferites ludhamensis Head, 1996b, from the upper Pliocene of eastern England, has a similar wall structure but hollow, non-membranous processes and hollow sutural crests. Spiniferites delicatus Reid, 1974, from modern sediments of the British Isles, has processes of similar shape but connected by high sutural crests, and a central body wall structure characterized by a pedium with radial fibres and a thin granular tegillum whose surface appears microgranular to microreticulate. Spiniferites delicatus also differs in having a reduced archeopyle.
Occurrence. Presently known only from the Eemian of the Baltic region; occurring persistently but in low numbers hrough zones RKDf 2 and 3 (reaching 3.7 % in RKDf 3) at Ristinge Klint, Denmark; in low numbers at Mommark, Denmark (M. J. Head, unpub. data); and sporadically and in low numbers at Lizce, Poland (as Spiniferites sp. 1 in Head et al. 2005). This species appears to tolerate reduced salinities judging from its early presence at the base of subzone RKDf 2a, although surface-water salinities nevertheless exceeded about 15 psu and bottom waters exceeded about 22 psu at this time (see Section 10.c).