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Areosphaeridium multicornutum
Areosphaeridium multicornutum, Eaton, 1971
Tax. jr. synonym of Areosphaeridium? pectiniforme (Gerlach, 1961) Stover and Evitt, 1978, according to Sarjeant, 1984.
Stover and Williams, 1995, retained the species as Enneadocysta multicornuta.
Holotype: Eaton, 1971, pl.4, fig.1, text-fig.6
Locus typicus: Alum Bay, Isle of Wight, England
Stratum typicum: Middle Eocene
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Original description: [Eaton, 1971, p. 363-364]:
Diagnosis:
The central body has a sub-circular to sub-quadrate outline and a finely granular surface.
The processes are intratabular and have solid fibrous stems of variable length and breadth. Each process is distally expanded and bifurcate; the attitude of the bifurcations varies from patulate to recurved. The bifurcations are of variable length, and they vary in breadth from slender with a denticulate distal margin, to broad, typically net-like, with an irregular distal margin. Fenestration is sometimes present in a few of the process stems and produces stem branches.
The tabulation of 4", 6", 6""", 1p, 1"""" is not fully reflected by the Intratabular processes. On the apical zone there are 4 processes (1" - 4"). On the precingular zone there are five processes (1" - 5"), and plate 6" is devoid of processes. There are between four and seven cingular processes which are situated on the lateral margins of the cingular zone. On the postcingular zone there are five processes (1"""- 5"""), and plate 6""" is devoid of processes. There is one process reflecting the posterior intercalary plate (1p). The antapex is typically offset to the right of the mid-ventral line and bears one process (1""""). Between the postcingular processes and the antapical process there are between one and five additional processes. The archaeopyle is apical, tetratabular.
Dimensions:
Holotype: central body (without operculum), length 46 µm, breadth 50 µm; processes, length 16.5-22 µm, breadth 1-3 µm.
Observed range: central body, length (without operculum) 34-47 µm, breadth 34-50 µm; processes, length 11-25 µm, breadth 1-6 µm; number of specimens measured, 20.
Discussion:
The variation in the form of the processes in A. multicornutum is similar to that shown by A. arcuatum, including the frequent occurrence of broader processes reflecting plates 2""" and 4""" (pl. 4 fig. 2). The cingular processes in A. multicornutum are typically slender. Although they are restricted to the margins of the cingular zone, the cingular processes are not randomly distributed, but are arranged in a line approximately parallel to the pre- and postcingular zones. As with A. arcuatum the additional processes are probably postcingular or antapical rather than reflecting distinct plate areas. The number of cingular and additional processes quoted in the diagnosis for A. multicornutum is based on specimens from the Bracklesham Beds; specimens with a greater number of processes may occur.
Affinities:
A. multicornutum is distinguished from A. arcuatum var. A by having cingular processes and frequently having a greater number of additional processes on the hypotract. A. multicornutum differs from A. arcuatum var. B, in having plates 6" and 6""" devoid of processes, and in always having cingular processes.
Tax. jr. synonym of Areosphaeridium? pectiniforme (Gerlach, 1961) Stover and Evitt, 1978, according to Sarjeant, 1984.
Stover and Williams, 1995, retained the species as Enneadocysta multicornuta.
Holotype: Eaton, 1971, pl.4, fig.1, text-fig.6
Locus typicus: Alum Bay, Isle of Wight, England
Stratum typicum: Middle Eocene
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Eaton, 1971, p. 363-364]:
Diagnosis:
The central body has a sub-circular to sub-quadrate outline and a finely granular surface.
The processes are intratabular and have solid fibrous stems of variable length and breadth. Each process is distally expanded and bifurcate; the attitude of the bifurcations varies from patulate to recurved. The bifurcations are of variable length, and they vary in breadth from slender with a denticulate distal margin, to broad, typically net-like, with an irregular distal margin. Fenestration is sometimes present in a few of the process stems and produces stem branches.
The tabulation of 4", 6", 6""", 1p, 1"""" is not fully reflected by the Intratabular processes. On the apical zone there are 4 processes (1" - 4"). On the precingular zone there are five processes (1" - 5"), and plate 6" is devoid of processes. There are between four and seven cingular processes which are situated on the lateral margins of the cingular zone. On the postcingular zone there are five processes (1"""- 5"""), and plate 6""" is devoid of processes. There is one process reflecting the posterior intercalary plate (1p). The antapex is typically offset to the right of the mid-ventral line and bears one process (1""""). Between the postcingular processes and the antapical process there are between one and five additional processes. The archaeopyle is apical, tetratabular.
Dimensions:
Holotype: central body (without operculum), length 46 µm, breadth 50 µm; processes, length 16.5-22 µm, breadth 1-3 µm.
Observed range: central body, length (without operculum) 34-47 µm, breadth 34-50 µm; processes, length 11-25 µm, breadth 1-6 µm; number of specimens measured, 20.
Discussion:
The variation in the form of the processes in A. multicornutum is similar to that shown by A. arcuatum, including the frequent occurrence of broader processes reflecting plates 2""" and 4""" (pl. 4 fig. 2). The cingular processes in A. multicornutum are typically slender. Although they are restricted to the margins of the cingular zone, the cingular processes are not randomly distributed, but are arranged in a line approximately parallel to the pre- and postcingular zones. As with A. arcuatum the additional processes are probably postcingular or antapical rather than reflecting distinct plate areas. The number of cingular and additional processes quoted in the diagnosis for A. multicornutum is based on specimens from the Bracklesham Beds; specimens with a greater number of processes may occur.
Affinities:
A. multicornutum is distinguished from A. arcuatum var. A by having cingular processes and frequently having a greater number of additional processes on the hypotract. A. multicornutum differs from A. arcuatum var. B, in having plates 6" and 6""" devoid of processes, and in always having cingular processes.