Back
Chiropteridium gilbertii
From Fensome et al., 2019:
Chiropteridium gilbertii Fensome et al., 2016b, p35, pl.4. figs.1–4. Holotype: Fensome et al., 2016b, pl.4, fig.4. Age: last
occurrence, Bartonian.
---------------------------------------------------------------------------------------------------
Original description Fensome et al., 2016b:
Holotype. Plate 4, fig. 4, from a cuttings sample at 1600–1610 m in Gilbert F-53, GSC type collection no.137976, sample P39466, slide 01, co-ordinates 17.4 × 106.0, England Finder R36/3. Overall length 83 μm, width 87 μm; central body, length 57 μm, width 52 μm; maximum length of processes 20 μm, width varies from less than 1 to 10 μm. The age determined for the sample from which the holotype was recovered is basal Bartonian.
Etymology. The epithet is derived from the name of the Gilbert F-53 offshore exploration well, in which the species is abundant.
Diagnosis. A species of Chiropteridium in which the processes or process complexes delineate the tabulation and there are no interconnections between processes representing adjacent plates.
Description. The processes delineate the tabulation, though none are interconnected. Processes on the midventral and mid-dorsal surfaces are reduced in width or absent: this is especially true of the 3´´ process that, if present, is very slender. Commonly, processes are basally trumpet-shaped, then tubular or parallel-sided. Processes are also of variable size depending on which plate series they are reflecting, with cingular processes being invariably slender, precingular processes broader, and postcingular processes being broader still, and the antapical process being broadest of all. Many of the processes are perforate.
Size. Overall maximum diameter 87 μm; maximum diameter of central body 57 μm; maximum length of processes 25 μm, maximum width 17 μm; seven specimens measured.
Age. LO: Bartonian.
Remarks. In Chiropteridium gilbertii, the central body, which is granulate, commonly has a prominent antapical protuberance. All of the processes, which are intratabular, have a circular cross-section proximally and distally are closed and commonly branch into short bifurcations or aculeae. Proximally, the processes tend to be conical then become tubular about halfway along their length before flaring distally. The processes are often fibrous and/or perforate, especially the antapical process, which sometimes subdivides to form a process complex. Recognition of the antapical process, if the archaeopyle is not obvious, is facilitated by the extreme width and the perforations, which may form arches in the process wall. Cingular processes are invariably slender, some less than 1 μm wide, rarely exceed four in number, and are restricted to the ambital region of the central body. Apical processes show variation in width on different specimens. Precingular processes are always narrower than the postcingular processes. Although the sulcal notch is offset, this is not always obvious. Chiropteridium gilbertii differs from Chiropteridium galea in having processes or process complexes that are restricted to individual plates. Licracysta semicirculata has processes that are restricted to the ambitus and tend to form arcuate complexes. The processes of Chiropteridium gilbertii vary in size according to the plate they represent, and are often fibrous and/or perforate. Chiropteridium conispinum also has membranous processes, but these are restricted to the dorsal surface, with two linear membranes running apically–antapically on the ventral surface.
Chiropteridium gilbertii Fensome et al., 2016b, p35, pl.4. figs.1–4. Holotype: Fensome et al., 2016b, pl.4, fig.4. Age: last
occurrence, Bartonian.
---------------------------------------------------------------------------------------------------
Original description Fensome et al., 2016b:
Holotype. Plate 4, fig. 4, from a cuttings sample at 1600–1610 m in Gilbert F-53, GSC type collection no.137976, sample P39466, slide 01, co-ordinates 17.4 × 106.0, England Finder R36/3. Overall length 83 μm, width 87 μm; central body, length 57 μm, width 52 μm; maximum length of processes 20 μm, width varies from less than 1 to 10 μm. The age determined for the sample from which the holotype was recovered is basal Bartonian.
Etymology. The epithet is derived from the name of the Gilbert F-53 offshore exploration well, in which the species is abundant.
Diagnosis. A species of Chiropteridium in which the processes or process complexes delineate the tabulation and there are no interconnections between processes representing adjacent plates.
Description. The processes delineate the tabulation, though none are interconnected. Processes on the midventral and mid-dorsal surfaces are reduced in width or absent: this is especially true of the 3´´ process that, if present, is very slender. Commonly, processes are basally trumpet-shaped, then tubular or parallel-sided. Processes are also of variable size depending on which plate series they are reflecting, with cingular processes being invariably slender, precingular processes broader, and postcingular processes being broader still, and the antapical process being broadest of all. Many of the processes are perforate.
Size. Overall maximum diameter 87 μm; maximum diameter of central body 57 μm; maximum length of processes 25 μm, maximum width 17 μm; seven specimens measured.
Age. LO: Bartonian.
Remarks. In Chiropteridium gilbertii, the central body, which is granulate, commonly has a prominent antapical protuberance. All of the processes, which are intratabular, have a circular cross-section proximally and distally are closed and commonly branch into short bifurcations or aculeae. Proximally, the processes tend to be conical then become tubular about halfway along their length before flaring distally. The processes are often fibrous and/or perforate, especially the antapical process, which sometimes subdivides to form a process complex. Recognition of the antapical process, if the archaeopyle is not obvious, is facilitated by the extreme width and the perforations, which may form arches in the process wall. Cingular processes are invariably slender, some less than 1 μm wide, rarely exceed four in number, and are restricted to the ambital region of the central body. Apical processes show variation in width on different specimens. Precingular processes are always narrower than the postcingular processes. Although the sulcal notch is offset, this is not always obvious. Chiropteridium gilbertii differs from Chiropteridium galea in having processes or process complexes that are restricted to individual plates. Licracysta semicirculata has processes that are restricted to the ambitus and tend to form arcuate complexes. The processes of Chiropteridium gilbertii vary in size according to the plate they represent, and are often fibrous and/or perforate. Chiropteridium conispinum also has membranous processes, but these are restricted to the dorsal surface, with two linear membranes running apically–antapically on the ventral surface.