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Hystrichosphaeridium petilum
Hystrichosphaeridium petilum Gitmez, 1970
Holotype: Gitmez, 1970, pl.p, fig.1, text-fig.24
Locus typicus: Ringstead Bay, Dorset, England
Stratum typicum: Early Kimmeridgian
Original diagnosis: Gitmez, 1970, p.289
A Hystrichosphaeridium having a subspherical delicate thin-walled shell. Processes very slender, tubular, open distally, with 4-6 aculeate spines around the process mouths. Reflected tabulation 4, 6", 6c, 0-1s, 6""", 1p and 1"""". Surface of the shell smooth. An apical archaeopyle is usually present.
Dimensions: Holotype: shell length (apex lacking) 35 µm, breadth 35 µm; process length 17-20 µm, breadth up to 3 µm. Range of the English specimens (20 specimens measured): length 30-35 µm, (apex lacking) 28 µm, breadth 25-35 µm. French specimens (2 specimens measured): length 33-35 µm, breadth 25-35 µm. Scottish specimens (10 specimens measured): length 22-32 µm, (apex lacking) 20-30 µm, breadth 16-35 µm; process length 12-20 µm.
Original description: Gitmez, 1970, p.289
The central body and the processes are characteristically thinwalled. The central body is composed of two membranes, an inner endophragm and an outer periphragm, the periphragm only comprising the processes. The tubular processes are usually curved or bent to some extent, probably as a result of preservation. They are usually, at least, two-thirds of the shell length. The spines on the tube mouths are up to 4 µm in length and 4-6 in number. An apical archaeopyle is usually present, formed by loss of the apex with four apical processes.
Affinities:
Gitmez, 1970, p.289: This new chorate cyst was attributed to Hystrichosphaeridium without hesitation in view of the features described above. It is similar to H. tubiferum, H. recurvatum, H. bowerbanki and H. sheppeyense, but differs in details and the number of the processes: H. tubiferum has 4-5 sulcal processes, whereas in H. petilum either only one sulcal process or none at all are present. The processes of H. tubiferum are thicker and distally have an entire or serrate circular margin. H. recurvatum has 3-6 sulcal processes. The processes of H. sheppeyense are relatively thick-walled and, at the base of some of the processes, there are small proximal elevations or swellings. H. bowerbanki is ovoidal to elongate in shape and has 5 sulcal processes. H. petilum therefore is significantly different from all these species. It was observed in the basal Kimmeridgian assemblages from England, Scotland and France in moderate number.
Holotype: Gitmez, 1970, pl.p, fig.1, text-fig.24
Locus typicus: Ringstead Bay, Dorset, England
Stratum typicum: Early Kimmeridgian
Original diagnosis: Gitmez, 1970, p.289
A Hystrichosphaeridium having a subspherical delicate thin-walled shell. Processes very slender, tubular, open distally, with 4-6 aculeate spines around the process mouths. Reflected tabulation 4, 6", 6c, 0-1s, 6""", 1p and 1"""". Surface of the shell smooth. An apical archaeopyle is usually present.
Dimensions: Holotype: shell length (apex lacking) 35 µm, breadth 35 µm; process length 17-20 µm, breadth up to 3 µm. Range of the English specimens (20 specimens measured): length 30-35 µm, (apex lacking) 28 µm, breadth 25-35 µm. French specimens (2 specimens measured): length 33-35 µm, breadth 25-35 µm. Scottish specimens (10 specimens measured): length 22-32 µm, (apex lacking) 20-30 µm, breadth 16-35 µm; process length 12-20 µm.
Original description: Gitmez, 1970, p.289
The central body and the processes are characteristically thinwalled. The central body is composed of two membranes, an inner endophragm and an outer periphragm, the periphragm only comprising the processes. The tubular processes are usually curved or bent to some extent, probably as a result of preservation. They are usually, at least, two-thirds of the shell length. The spines on the tube mouths are up to 4 µm in length and 4-6 in number. An apical archaeopyle is usually present, formed by loss of the apex with four apical processes.
Affinities:
Gitmez, 1970, p.289: This new chorate cyst was attributed to Hystrichosphaeridium without hesitation in view of the features described above. It is similar to H. tubiferum, H. recurvatum, H. bowerbanki and H. sheppeyense, but differs in details and the number of the processes: H. tubiferum has 4-5 sulcal processes, whereas in H. petilum either only one sulcal process or none at all are present. The processes of H. tubiferum are thicker and distally have an entire or serrate circular margin. H. recurvatum has 3-6 sulcal processes. The processes of H. sheppeyense are relatively thick-walled and, at the base of some of the processes, there are small proximal elevations or swellings. H. bowerbanki is ovoidal to elongate in shape and has 5 sulcal processes. H. petilum therefore is significantly different from all these species. It was observed in the basal Kimmeridgian assemblages from England, Scotland and France in moderate number.