Back
Exochosphaeridium majus
Exochosphaeridium majus (Lejeune-Carpentier, 1940, p.B220–B221; text-fig.13) Peyrot, 2011, p. 284. Emendation: Lejeune-Carpentier and Sarjeant, 1981, p.12, as Amphorosphaeridium majus. Holotype: Lejeune-Carpentier, 1940, text-fig.13; Streel et
al., 1977, pl.1, fig.7; Lejeune-Carpentier and Sarjeant, 1981, pl.2, figs.6–7; text-fig.7. Originally Hystrichosphaeridium, subsequently Polysphaeridium?, thirdly Cordosphaeridium, fourthly Dapsilidinium? (combination not validly published), fifthly Amphorosphaeridium, sixthly (and now) Exochosphaeridium. Taxonomic junior synonyms: Baltisphaeridium (as Exochosphaeridium) bifidum and Exochosphaeridium bifidum var. involutum (as Exochosphaeridium bifidum subsp. involutum), both according to Peyrot (2011, p.284). The possibility of the latter synonymy was earlier postulated by Marheinecke (1992, p.51). Age: Late Cretaceous.
------------------------------------------------------------------------------------------------------------------------------------------------------
Original description (Lejeune-Carpentier, 1940) (translated from French):
Hystrichosphaeridium major n. sp. (fig. 13). - We apply this name to a few specimens in our collection whose shells are relatively large, with a major diameter ranging from 55 to nearly 70 μm. The tubes are rather short, generally not exceeding half the major diameter of the shell (1). Most of them are quite weak, some very slender, others, on the contrary, a little larger.
With the occasional exception of the latter, they do not show any particular development of the distal end. The number of tubes is high: 45 or more.
The holotype and the other specimens come from flint from the Limburg Basin, Spiennes bed.
1) They are indicated as not exceeding a quarter of the same length in H. multifurcatum Defl., a collective species whose structure will be analyzed by us on another occasion.
------------------------------------------------------------------------------------------------------------------------------------------------------
Emendation (Lejeune-Carpentier and Sarjeant, 1981):
Emended Diagnosis
Cyst spheroidal to ovoidal, skolochorate. Processes tubular, often fibrous. They appear to be essentially intratabular in position and number around 60, being less than one-half the cyst diameter in length. The processes are typically broad--based but vary greatly in thickness and in style of distal termination, the latter including bifurcate, trifurcate, foliate, digitate and aculeate forms; Archaeopyle single-plate precingular, type P.
Holotype
Specimen XIX-133 : lodged in the collections of the Laboratoire de Paleontologie, Universite de Liege, Belgium : figured by Lejeune-Carpentier, 1940, fig. 13, and herein, Pl. 2: 6-7 and Text-fig. 7.
Type Horizon and Locality
Flint filling of echinoid, Craie de Spiennes (=Formatie van Gulpen of Felder, 1975), Upper Cretaceous (Senonian), Hallembaye, Limbourg Basin, Belgium.
Dimensions:
Holotype (in polar view) :diameter of cyst 64.5 µm, length of processes around 21.6 µm.
Range of Dimensions
Maximum cross-measurement of cyst 55-70 µm.
Description
The holotype is seen in antapical view : the antapical process is surrounded by a groove of polygonal outline, simulating the shape of a single antapical paraplate. Many of the other, larger processes are considered to be likewise intratabular in position, though in many instances there are clearly several processes per paraplate. The thinner processes appear to correspond to cingular and sulcal para plates ; however, it is possible that some may be sutural in situation.
In view of the position of the holotype in the enclosing flint, the apical surface is hard to see and our reconstruction of it (Text-fig. 7, right) must certainly be inaccurate in detail. However, the size, shape and position of the archaeopyle make it clear that this was formed by loss of a single precingular paraplate (probably 3").
The surface of the phragma shows a dense ornament of granules and/or punctae. The processes, formed from periphragm only, have this ornament to a reduced degree but are commonly fibrous.
Remarks
Determination of the style of archaeopyle makes it impossible any longer to retain the species major in the genus Polysphaeridium, which characteristically has an apical archaeopyle. Nor can the attribution of it to Cordosphaeridium by Corradini (1972) be upheld, since the processes of that genus are much less numerous (22-30).
The diagnosis of Amphorosphaeridium, as defined by Davey (1969b) and "modified" by Stover and Evitt (1978, p. 140-141), specifies fibrous, hollow processes that are non-tabular (or "frequent intratabular") and a single-plate precingular archaeopyle. The apical process is distinctive ; in the type species it is "a broad, fibrous structure which gives rise medially to two to four subsidiary processes" (Davey, 1969, p. 31). The structure of the apical surface of the holotype of major proved difficult to determine : whilst no such strongly fibrous structure was noted, the five apical processes appear to arise from a ridge or boss, which may be a foreshadowing of the sort of structure Davey describes. The antapical process is not necessarily distinctive in Amphorosphaeridium, but (as in several other genera) may be unusually large. In the species major, though the outlining of the antapical paraplate identifies the antapical process, that process itself is in no way exceptional. In view of these difficulties, the species major cannot be considered to conform exactly to existing concepts of Amphorosphaeridium; but the minor differences are, in our view, outweighed by the major similarities and it is allocated to that genus with fair confidence.
Despite the criticisms of Stover and Evitt (1978, p. 76), we consider that Corradini .was correct when he recognised this spec.ies from the Upper Cretaceous flysch of the Appenines (1972) ; one of his figures (pl. 22 : 8) indeed accords particularly closely with our concept of this species. We trust this redescription will facilitate its future recognition from other Upper Cretaceous localities also.
al., 1977, pl.1, fig.7; Lejeune-Carpentier and Sarjeant, 1981, pl.2, figs.6–7; text-fig.7. Originally Hystrichosphaeridium, subsequently Polysphaeridium?, thirdly Cordosphaeridium, fourthly Dapsilidinium? (combination not validly published), fifthly Amphorosphaeridium, sixthly (and now) Exochosphaeridium. Taxonomic junior synonyms: Baltisphaeridium (as Exochosphaeridium) bifidum and Exochosphaeridium bifidum var. involutum (as Exochosphaeridium bifidum subsp. involutum), both according to Peyrot (2011, p.284). The possibility of the latter synonymy was earlier postulated by Marheinecke (1992, p.51). Age: Late Cretaceous.
------------------------------------------------------------------------------------------------------------------------------------------------------
Original description (Lejeune-Carpentier, 1940) (translated from French):
Hystrichosphaeridium major n. sp. (fig. 13). - We apply this name to a few specimens in our collection whose shells are relatively large, with a major diameter ranging from 55 to nearly 70 μm. The tubes are rather short, generally not exceeding half the major diameter of the shell (1). Most of them are quite weak, some very slender, others, on the contrary, a little larger.
With the occasional exception of the latter, they do not show any particular development of the distal end. The number of tubes is high: 45 or more.
The holotype and the other specimens come from flint from the Limburg Basin, Spiennes bed.
1) They are indicated as not exceeding a quarter of the same length in H. multifurcatum Defl., a collective species whose structure will be analyzed by us on another occasion.
------------------------------------------------------------------------------------------------------------------------------------------------------
Emendation (Lejeune-Carpentier and Sarjeant, 1981):
Emended Diagnosis
Cyst spheroidal to ovoidal, skolochorate. Processes tubular, often fibrous. They appear to be essentially intratabular in position and number around 60, being less than one-half the cyst diameter in length. The processes are typically broad--based but vary greatly in thickness and in style of distal termination, the latter including bifurcate, trifurcate, foliate, digitate and aculeate forms; Archaeopyle single-plate precingular, type P.
Holotype
Specimen XIX-133 : lodged in the collections of the Laboratoire de Paleontologie, Universite de Liege, Belgium : figured by Lejeune-Carpentier, 1940, fig. 13, and herein, Pl. 2: 6-7 and Text-fig. 7.
Type Horizon and Locality
Flint filling of echinoid, Craie de Spiennes (=Formatie van Gulpen of Felder, 1975), Upper Cretaceous (Senonian), Hallembaye, Limbourg Basin, Belgium.
Dimensions:
Holotype (in polar view) :diameter of cyst 64.5 µm, length of processes around 21.6 µm.
Range of Dimensions
Maximum cross-measurement of cyst 55-70 µm.
Description
The holotype is seen in antapical view : the antapical process is surrounded by a groove of polygonal outline, simulating the shape of a single antapical paraplate. Many of the other, larger processes are considered to be likewise intratabular in position, though in many instances there are clearly several processes per paraplate. The thinner processes appear to correspond to cingular and sulcal para plates ; however, it is possible that some may be sutural in situation.
In view of the position of the holotype in the enclosing flint, the apical surface is hard to see and our reconstruction of it (Text-fig. 7, right) must certainly be inaccurate in detail. However, the size, shape and position of the archaeopyle make it clear that this was formed by loss of a single precingular paraplate (probably 3").
The surface of the phragma shows a dense ornament of granules and/or punctae. The processes, formed from periphragm only, have this ornament to a reduced degree but are commonly fibrous.
Remarks
Determination of the style of archaeopyle makes it impossible any longer to retain the species major in the genus Polysphaeridium, which characteristically has an apical archaeopyle. Nor can the attribution of it to Cordosphaeridium by Corradini (1972) be upheld, since the processes of that genus are much less numerous (22-30).
The diagnosis of Amphorosphaeridium, as defined by Davey (1969b) and "modified" by Stover and Evitt (1978, p. 140-141), specifies fibrous, hollow processes that are non-tabular (or "frequent intratabular") and a single-plate precingular archaeopyle. The apical process is distinctive ; in the type species it is "a broad, fibrous structure which gives rise medially to two to four subsidiary processes" (Davey, 1969, p. 31). The structure of the apical surface of the holotype of major proved difficult to determine : whilst no such strongly fibrous structure was noted, the five apical processes appear to arise from a ridge or boss, which may be a foreshadowing of the sort of structure Davey describes. The antapical process is not necessarily distinctive in Amphorosphaeridium, but (as in several other genera) may be unusually large. In the species major, though the outlining of the antapical paraplate identifies the antapical process, that process itself is in no way exceptional. In view of these difficulties, the species major cannot be considered to conform exactly to existing concepts of Amphorosphaeridium; but the minor differences are, in our view, outweighed by the major similarities and it is allocated to that genus with fair confidence.
Despite the criticisms of Stover and Evitt (1978, p. 76), we consider that Corradini .was correct when he recognised this spec.ies from the Upper Cretaceous flysch of the Appenines (1972) ; one of his figures (pl. 22 : 8) indeed accords particularly closely with our concept of this species. We trust this redescription will facilitate its future recognition from other Upper Cretaceous localities also.