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Gardodinium trabeculosum
Gardodinium trabeculosum (Gocht, 1959) Alberti, 1961; emend. Harding 1996
Originally Scriniodinium, subsequently (and now) Gardodinium, thirdly Chlamydophorella. Davey, 1978, transferred this species to Chlamydophorella Cookson and Eisenack, 1958. Harding, 1990, agreed with Davey, 1978. Lentin and Williams (1989, p.143) retained this species in Gardodinium.
Taxonomic junior synonyms: Gardodinium eisenackii, according to Davey (1974, p.51); Gardodinium albertii and Gardodinium pyriforme, both according to Harding (1996, p.359); Gardodinium elongatum, by implication in Brideaux and McIntyre (1975, p.33), who considered Gardodinium elongatum to be a taxonomic junior synonym of Gardodinium eisenackii. The nomenclatural type of the genus Gardodinium remains the holotype of Gardodinium eisenackii.
Holotype: Gocht, 1959, pl.4, fig.5; Harding, 1996, pl.3, figs.1,6–7.
Locus typicus: NW Germany
Stratum typicum: Hauterivian
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Gardodinium trabeculosum (Gocht, 1959) Alberti, 1961, emend. Harding, 1996. According to Harding (1996), Gardodinium trabeculosum has solid, slender processes, which support a thin ectophragm that is developed into an elongate, almost parallel sided, apical horn. Paracingulum pronounced. Archeopyle involves apical and incidental paraplates as an adnate, simple, polyplacoid operculum. Paratabulation fully developed on the ectophragm as indicated by continuous low parasutural ridges. Dimensions from Gocht, length 64-76 µm, width 53-68 µm, Hunstanton specimens. Length 70-81 µm, width 57-69 µm. One specimen 95 x 78 µm.
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Original diagnosis: Gocht 1959, p. 62: Scriniodinium trabeculosum
Central body tabulated, flattened, circular to elliptical, with broadly based apical horn, girdle faintly helicoidal, slightly deepened, plate margins simple and thin. Inner body roundish, below the apex with a conical protrusion, entering the apical horn. Cavity between shell and inner body supported by numerous processes.
Membranes soft and transparent. Dimensions: length: 64-73 µm; breadth: 63-68 µm.
Harding 1966
Gardodinium trabeculosum (Gocht) Alberti, 1961, emend. nov. ( Plates III and IV; Fig. 1 )
1959 Scriniodinium trabeculosum-Gocht, p. 62, plate 4, fig. 5; plate 8, fig. 2. Hauterivian.
1961 Gardodinium trabeculosum (Gocht)-Alberti, p. 18.
1961 Gardodinium eisenackii-Alberti, p. 18, plate 3, figs. 8- 13. Hauterivian-Aptian.
1962 Gardodinium albertii-Neale and Sarjeant, pp. 445 446, plate 19, fig. 8. Hauterivian.
?1967 Gardodinium pyriforme-Vozzhennikova, p. 179, plate 100, figs. 1, 4. Barremian.
1974 Chlamydophorella trabeculosa (Gocht)-Davey, p. 51. Barremian.
1989 Gardodinium trabeculosum (Gocht) Alberti, 1961 Lentin and Williams, p. 143.
Emended diagnosis
Large leptodinioidean cyst without strong axial elongation. Autophragm bears solid, slender processes which support a thin ectophragm that is developed into an elongate almost parallelsided apical horn. Paracingulum pronounced. Archaeopyle involves apical and incidental paraplates as an adnate, simple polyplacoid operculum. Paratabulation fully developed on the ectophragm as indicated by continuous low parasutural ridges.
Emended description
Shape: Ectophragmal ambitus essentially pentagonal, modified by development of elongate apical horn. Epicystal ectophragmal ambitus usually bellshaped, apical plate series form a flattened area, adjacent to precingular plates, which tapers apically to create a broad-based apical horn. This horn is hollow and open distally. Precingular plates are convex apically and concave adcingularly.
Hypocystal ectophragmal ambitus often asymmetrical, the lefthand margin being slightly lobate (along X/Z and 3/Y ). Cyst holocavate, the autophragmal ambitus is essentially similar to that of the ectophragm but with a much more rounded aspect (Plate III, 1-5). The autophragmal apical horn is closed distally and of variable length, but never extends far into the ectophragmal horn. Epicyst (including apical horn) about twice as long as hypocyst. Greatest width across cingulum. Moderate primary dorso-ventral compression.
Phragma: Ectophragm is about 0.1 Ám thick and highly perforate. These perforations are <0.1 Ám in diameter and consequently difficult to observe at low magnifications, which gives the ectophragm a more solid appearance. At high magnification it appears that the ectophragm is composed of fused sporopollenin globules. Parasutures are identified by shallow stepped ridges, the margins of which may appear scalloped or striate perpendicular to the parasutures, rather in the manner of pandasutural bands (Plate IV, 3, 8). The parasutural ridges are asymmetrical, with the overlapping plate possessing a shallow cross-sectional profile, and the overlapped plate a steep one. Analysis of these features has allowed a reconstruction of the overlapping plate system in the original thecal organism (Fig. 1), indicating that 4 and IV were the probable keystone plates. All paraplates bear circular depressions, about 0.5 Ám in diameter, which indicate the point of contact between the ectophragm and the autophragmal process supporting this layer, and the ectophragm is slightly indented at these contact points (Plate IV, 3, 4). (The contact between the processes and the ectophragm may appear "funneliform" in the light microscope. This is more pronounced than is actually the case due to the contact being seen in cross-section in light microscopy).
There is a 3-4 Ám long, blade-like outgrowth of the ectophragm found on paraplate II. This feature lies adjacent and perpendicular to the II/X parasuture, about 3 Ám in an antapical direction from the II/Iu/X triple junction. This blade is developed to a greater or lesser extent on all the specimens so far examined (see Plate IV, 11).
The autophragm is 0.2 Ám thick and has a laevigate surface bearing intratabular and vaguely penitabular processes. The solid cylindrical processes are generally 3 Ám long but may reach up to 9 Ám in length in the paracingular area where cavation is at its maximum. The processes flare proximally and distally (this feature has often been taken as a distal bifurcation, again a misinterpretation resulting from cross-sectional observation) and may anastomose in mid-length. All process bases are surrounded by an areola of punctae (Plate IV, 7) .
Paratabulation: L-type sexiform gonyaulacoid. Paratabulation formula: lpr, 4', la, 6", 6c, 6"', 1"", lp, 5s. li is axially elongated and equal in length to the other precingular plates. lu/ai is adcingular to A/li. An incidental plate K (="la") is present on the dorsal epicyst at the B/C/4 triple junction (Plate IV, 10). The presence of preapicals is problematic due to the truncation of the apical horn, but a small "V"-shaped structure found on the dorsal surface of the ectophragmal horn (along B/C, Plate IV, 10) in an extreme apical position may be identified with a preapical plate (P). Apical tabulation often unclear due to compression of cyst and creation of "pseudosutures" due to fracturing of the ectophragm. Contact of ai and 2 seen on some specimens. This species shows the Ornatum-type of organisation as described by Helenes (1986).
Archaeopyle: Type (tA)a comprising apical and incidental plates. As the archaeopyle suture can often be traced on complete specimens, it appears that the operculum remains adnate via lu/ai, the simple polyplacoid operculum flapping down like a lid after excystment of the protoplasm. Cysts are, however, frequently found without opercula and in these instances it can be determined that the operculum has been mechanically removed by rupture of the thin phragma across paraplate lu.
Paracingulum: Usually 6 Ám wide, but can attain a width of 9 Ám. Prominently displayed as a shallow depression on the equatorial margin. Laevorotatory, displaced by about 2 cingulum width.
Parasulcus: Fully developed with no suppression of parasutures. Prominent flagellar scar. Axially elongated ellipsoidal Z plate (Plate IV, 5, 11).
Dimensions
German specimen measurements as quoted by Gocht (1959, p.63). Holotype: length, 74 Ám; width, 62 Ám; apical horn length, 16 Ám. Measurements of seven specimens: length, 64-76 Ám; width, 53-68 Ám. Four additional specimens illustrated herein: length, (80) 82 (83) Ám; width, (60) 64 (66) Ám.
Hunstanton specimens. Length, (70) 75 (81) Ám; width, (57) 61 (69) Ám, 8 specimens measured (one exceptionally large specimen 95 x 78 Ám was not included in these figures).
Remarks
The data presented here represent the results of a study of new DIC micrographs of the type specimen and new topotype specimens extracted from the German material studied by Gocht (1959). Additional conspecific specimens showing three dimensional preservation from the Hunstanton borehole, Norfolk, England, along with specimens from Speeton, Yorkshire, England and Gott and Frielingen, Germany have also been utilised.
This emendation stresses the paratabulate nature of the ectophragm, which is discernable to a greater or lesser degree, dependant on the state of preservation. Specimens of this species are usually found secondarily compressed. In this state the thin ectophragm collapses and folds over the autophragmal processes, so obscuring some details of paratabulation (PlateIV, 1). In the collapsed state paratabulation is also indicated by the alignment of some of the processes in a penitabular manner. The observation of uncompressed specimens has thus enabled a much clearer understanding of the morphology of this morphotype. The function of the blade-like structure on plate II is unknown, although it may have been associated with a sulcal "list" on the thecate organism.
As emended, G. trabeculosum displays Q/B apical, lu/li ventral and asymmetrical quadrate antapical paraplate organisations, indicative of an ornatum-type paratabulation (Helenes, 1986). Fensome et al. (1993), assigned Gardodinium to the order Gonyaulacales, the subordinal and familial classification being unknown. Analysis of the paratabulation of G. trabeculosum now indicates that assignment to the subfamily Leptodinioideae of Fensome et al. (1993) is appropriate.
The present author concurs with Davey (1974, p. 51) in the view that Gardodinium eisenackii Alberti, 1961 falls within the circumscription of G. trabeculosum and should be seen as a junior synonym of the latter species. This confirms the type specimen of the latter species as the type of the genus. The only distinction between the forms described by Alberti (1961, p. 18) and the type of the species appears to be a slight size variation, more than accommodated by the current size range determined for G. trabeculosum.
Examination of the type material of Gardodinium albertii Neale and Sarjeant, 1962 by the present author, also indicates that this species is conspecific with the type specimen of G. trabeculosum. In size it falls within the range of G. trabeculosum and shows pronounced crumpling of the apical horn and compression of the ectophragm onto the autophragmal processes. Examination of the type material of G. albertii, coupled with observation of topotype material of Hauterivian age from type locality, the Speeton Clay, have yielded specimens which when studied in both LM and SEM are clearly referrable to G. trabeculosum. G. albertii is therefore regarded as a junior synonym of G. trabeculosum.
The species described by Vozzhennikova (1967, p. 179) as Gardodinium pyriforme, may also be a junior synonym of G. trabeculosum, after observation of videotape of the Russian material and the examination of new photomicrographs. The geological age ( Barremian) and size range given for Vozzhennikova's type specimen and lectotype are similar to those of G. trabeculosum. In addition the morphological features displayed by the type specimen are consistent with the emended description of G. trabeculosum, down to the paratabulation which is indicated on G. pyriforme "by distinct to indistinct ridges on the ectophragm" (Lentin and Vozzhennikova, 1990, p. 102). Indeed, whilst the lectotype of G. pyriforme is strongly reminiscent of compressed Boreal specimens of G. trabeculosum, two of the specimens figured by Vozzhennikova (1967, plate c, fig. l as G. pyriforme and plate c, fig. 2 as G. sp.) appear identical to the Hunstanton specimens described here. Lentin (pers. commun., 1991) does not believe that these species are conspecific, placing emphasis on the development of the autophragmal apical horn and the two filamentous processes extending from this horn into the ectophragmal apical horn on the lectotype of G. pyriforme. However, viewing a population of Boreal European specimens of G. trabeculosum, not only is the development of the autophragmal apical horn variable, but many specimens also display processes extending from this horn into that of the ectophragm (Plate III, 3, 4). The possible synonymy of G. trabeculosum and G. pyriforme requires further investigation.
Following the present author's examination of the type specimen and other specimens of Gardodinium ordinale Davey, 1974, this species can be confidently assigned to Gardodinium. As yet, the type specimens of G. attenuatum and G. Iowii have not been observed.
Stratigraphic distribution
The type material was described by Gocht (1959), from upper Hauterivian sediments of Germany. The oldest record of G. trabeculosum is given by Heilmann-Clausen ( 1987), from rocks questionably dated as early Valanginian. Other recent reports (see Nohr-Hansen, 1993, p. 56, for exhaustive list of publications recording this taxon), indicate that G. trabeculosum can be found in sediments of early Hauterivian age through into those of the late Aptian in Boreal northwest Europe. However, publications dealing with material from various locations in Canada intimate that this species may be recorded from strata as young as late Albian in age. From the above, the stratigraphic range of this taxon may encompass an early Valanginian-late Albian time span.
Originally Scriniodinium, subsequently (and now) Gardodinium, thirdly Chlamydophorella. Davey, 1978, transferred this species to Chlamydophorella Cookson and Eisenack, 1958. Harding, 1990, agreed with Davey, 1978. Lentin and Williams (1989, p.143) retained this species in Gardodinium.
Taxonomic junior synonyms: Gardodinium eisenackii, according to Davey (1974, p.51); Gardodinium albertii and Gardodinium pyriforme, both according to Harding (1996, p.359); Gardodinium elongatum, by implication in Brideaux and McIntyre (1975, p.33), who considered Gardodinium elongatum to be a taxonomic junior synonym of Gardodinium eisenackii. The nomenclatural type of the genus Gardodinium remains the holotype of Gardodinium eisenackii.
Holotype: Gocht, 1959, pl.4, fig.5; Harding, 1996, pl.3, figs.1,6–7.
Locus typicus: NW Germany
Stratum typicum: Hauterivian
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Gardodinium trabeculosum (Gocht, 1959) Alberti, 1961, emend. Harding, 1996. According to Harding (1996), Gardodinium trabeculosum has solid, slender processes, which support a thin ectophragm that is developed into an elongate, almost parallel sided, apical horn. Paracingulum pronounced. Archeopyle involves apical and incidental paraplates as an adnate, simple, polyplacoid operculum. Paratabulation fully developed on the ectophragm as indicated by continuous low parasutural ridges. Dimensions from Gocht, length 64-76 µm, width 53-68 µm, Hunstanton specimens. Length 70-81 µm, width 57-69 µm. One specimen 95 x 78 µm.
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Original diagnosis: Gocht 1959, p. 62: Scriniodinium trabeculosum
Central body tabulated, flattened, circular to elliptical, with broadly based apical horn, girdle faintly helicoidal, slightly deepened, plate margins simple and thin. Inner body roundish, below the apex with a conical protrusion, entering the apical horn. Cavity between shell and inner body supported by numerous processes.
Membranes soft and transparent. Dimensions: length: 64-73 µm; breadth: 63-68 µm.
Harding 1966
Gardodinium trabeculosum (Gocht) Alberti, 1961, emend. nov. ( Plates III and IV; Fig. 1 )
1959 Scriniodinium trabeculosum-Gocht, p. 62, plate 4, fig. 5; plate 8, fig. 2. Hauterivian.
1961 Gardodinium trabeculosum (Gocht)-Alberti, p. 18.
1961 Gardodinium eisenackii-Alberti, p. 18, plate 3, figs. 8- 13. Hauterivian-Aptian.
1962 Gardodinium albertii-Neale and Sarjeant, pp. 445 446, plate 19, fig. 8. Hauterivian.
?1967 Gardodinium pyriforme-Vozzhennikova, p. 179, plate 100, figs. 1, 4. Barremian.
1974 Chlamydophorella trabeculosa (Gocht)-Davey, p. 51. Barremian.
1989 Gardodinium trabeculosum (Gocht) Alberti, 1961 Lentin and Williams, p. 143.
Emended diagnosis
Large leptodinioidean cyst without strong axial elongation. Autophragm bears solid, slender processes which support a thin ectophragm that is developed into an elongate almost parallelsided apical horn. Paracingulum pronounced. Archaeopyle involves apical and incidental paraplates as an adnate, simple polyplacoid operculum. Paratabulation fully developed on the ectophragm as indicated by continuous low parasutural ridges.
Emended description
Shape: Ectophragmal ambitus essentially pentagonal, modified by development of elongate apical horn. Epicystal ectophragmal ambitus usually bellshaped, apical plate series form a flattened area, adjacent to precingular plates, which tapers apically to create a broad-based apical horn. This horn is hollow and open distally. Precingular plates are convex apically and concave adcingularly.
Hypocystal ectophragmal ambitus often asymmetrical, the lefthand margin being slightly lobate (along X/Z and 3/Y ). Cyst holocavate, the autophragmal ambitus is essentially similar to that of the ectophragm but with a much more rounded aspect (Plate III, 1-5). The autophragmal apical horn is closed distally and of variable length, but never extends far into the ectophragmal horn. Epicyst (including apical horn) about twice as long as hypocyst. Greatest width across cingulum. Moderate primary dorso-ventral compression.
Phragma: Ectophragm is about 0.1 Ám thick and highly perforate. These perforations are <0.1 Ám in diameter and consequently difficult to observe at low magnifications, which gives the ectophragm a more solid appearance. At high magnification it appears that the ectophragm is composed of fused sporopollenin globules. Parasutures are identified by shallow stepped ridges, the margins of which may appear scalloped or striate perpendicular to the parasutures, rather in the manner of pandasutural bands (Plate IV, 3, 8). The parasutural ridges are asymmetrical, with the overlapping plate possessing a shallow cross-sectional profile, and the overlapped plate a steep one. Analysis of these features has allowed a reconstruction of the overlapping plate system in the original thecal organism (Fig. 1), indicating that 4 and IV were the probable keystone plates. All paraplates bear circular depressions, about 0.5 Ám in diameter, which indicate the point of contact between the ectophragm and the autophragmal process supporting this layer, and the ectophragm is slightly indented at these contact points (Plate IV, 3, 4). (The contact between the processes and the ectophragm may appear "funneliform" in the light microscope. This is more pronounced than is actually the case due to the contact being seen in cross-section in light microscopy).
There is a 3-4 Ám long, blade-like outgrowth of the ectophragm found on paraplate II. This feature lies adjacent and perpendicular to the II/X parasuture, about 3 Ám in an antapical direction from the II/Iu/X triple junction. This blade is developed to a greater or lesser extent on all the specimens so far examined (see Plate IV, 11).
The autophragm is 0.2 Ám thick and has a laevigate surface bearing intratabular and vaguely penitabular processes. The solid cylindrical processes are generally 3 Ám long but may reach up to 9 Ám in length in the paracingular area where cavation is at its maximum. The processes flare proximally and distally (this feature has often been taken as a distal bifurcation, again a misinterpretation resulting from cross-sectional observation) and may anastomose in mid-length. All process bases are surrounded by an areola of punctae (Plate IV, 7) .
Paratabulation: L-type sexiform gonyaulacoid. Paratabulation formula: lpr, 4', la, 6", 6c, 6"', 1"", lp, 5s. li is axially elongated and equal in length to the other precingular plates. lu/ai is adcingular to A/li. An incidental plate K (="la") is present on the dorsal epicyst at the B/C/4 triple junction (Plate IV, 10). The presence of preapicals is problematic due to the truncation of the apical horn, but a small "V"-shaped structure found on the dorsal surface of the ectophragmal horn (along B/C, Plate IV, 10) in an extreme apical position may be identified with a preapical plate (P). Apical tabulation often unclear due to compression of cyst and creation of "pseudosutures" due to fracturing of the ectophragm. Contact of ai and 2 seen on some specimens. This species shows the Ornatum-type of organisation as described by Helenes (1986).
Archaeopyle: Type (tA)a comprising apical and incidental plates. As the archaeopyle suture can often be traced on complete specimens, it appears that the operculum remains adnate via lu/ai, the simple polyplacoid operculum flapping down like a lid after excystment of the protoplasm. Cysts are, however, frequently found without opercula and in these instances it can be determined that the operculum has been mechanically removed by rupture of the thin phragma across paraplate lu.
Paracingulum: Usually 6 Ám wide, but can attain a width of 9 Ám. Prominently displayed as a shallow depression on the equatorial margin. Laevorotatory, displaced by about 2 cingulum width.
Parasulcus: Fully developed with no suppression of parasutures. Prominent flagellar scar. Axially elongated ellipsoidal Z plate (Plate IV, 5, 11).
Dimensions
German specimen measurements as quoted by Gocht (1959, p.63). Holotype: length, 74 Ám; width, 62 Ám; apical horn length, 16 Ám. Measurements of seven specimens: length, 64-76 Ám; width, 53-68 Ám. Four additional specimens illustrated herein: length, (80) 82 (83) Ám; width, (60) 64 (66) Ám.
Hunstanton specimens. Length, (70) 75 (81) Ám; width, (57) 61 (69) Ám, 8 specimens measured (one exceptionally large specimen 95 x 78 Ám was not included in these figures).
Remarks
The data presented here represent the results of a study of new DIC micrographs of the type specimen and new topotype specimens extracted from the German material studied by Gocht (1959). Additional conspecific specimens showing three dimensional preservation from the Hunstanton borehole, Norfolk, England, along with specimens from Speeton, Yorkshire, England and Gott and Frielingen, Germany have also been utilised.
This emendation stresses the paratabulate nature of the ectophragm, which is discernable to a greater or lesser degree, dependant on the state of preservation. Specimens of this species are usually found secondarily compressed. In this state the thin ectophragm collapses and folds over the autophragmal processes, so obscuring some details of paratabulation (PlateIV, 1). In the collapsed state paratabulation is also indicated by the alignment of some of the processes in a penitabular manner. The observation of uncompressed specimens has thus enabled a much clearer understanding of the morphology of this morphotype. The function of the blade-like structure on plate II is unknown, although it may have been associated with a sulcal "list" on the thecate organism.
As emended, G. trabeculosum displays Q/B apical, lu/li ventral and asymmetrical quadrate antapical paraplate organisations, indicative of an ornatum-type paratabulation (Helenes, 1986). Fensome et al. (1993), assigned Gardodinium to the order Gonyaulacales, the subordinal and familial classification being unknown. Analysis of the paratabulation of G. trabeculosum now indicates that assignment to the subfamily Leptodinioideae of Fensome et al. (1993) is appropriate.
The present author concurs with Davey (1974, p. 51) in the view that Gardodinium eisenackii Alberti, 1961 falls within the circumscription of G. trabeculosum and should be seen as a junior synonym of the latter species. This confirms the type specimen of the latter species as the type of the genus. The only distinction between the forms described by Alberti (1961, p. 18) and the type of the species appears to be a slight size variation, more than accommodated by the current size range determined for G. trabeculosum.
Examination of the type material of Gardodinium albertii Neale and Sarjeant, 1962 by the present author, also indicates that this species is conspecific with the type specimen of G. trabeculosum. In size it falls within the range of G. trabeculosum and shows pronounced crumpling of the apical horn and compression of the ectophragm onto the autophragmal processes. Examination of the type material of G. albertii, coupled with observation of topotype material of Hauterivian age from type locality, the Speeton Clay, have yielded specimens which when studied in both LM and SEM are clearly referrable to G. trabeculosum. G. albertii is therefore regarded as a junior synonym of G. trabeculosum.
The species described by Vozzhennikova (1967, p. 179) as Gardodinium pyriforme, may also be a junior synonym of G. trabeculosum, after observation of videotape of the Russian material and the examination of new photomicrographs. The geological age ( Barremian) and size range given for Vozzhennikova's type specimen and lectotype are similar to those of G. trabeculosum. In addition the morphological features displayed by the type specimen are consistent with the emended description of G. trabeculosum, down to the paratabulation which is indicated on G. pyriforme "by distinct to indistinct ridges on the ectophragm" (Lentin and Vozzhennikova, 1990, p. 102). Indeed, whilst the lectotype of G. pyriforme is strongly reminiscent of compressed Boreal specimens of G. trabeculosum, two of the specimens figured by Vozzhennikova (1967, plate c, fig. l as G. pyriforme and plate c, fig. 2 as G. sp.) appear identical to the Hunstanton specimens described here. Lentin (pers. commun., 1991) does not believe that these species are conspecific, placing emphasis on the development of the autophragmal apical horn and the two filamentous processes extending from this horn into the ectophragmal apical horn on the lectotype of G. pyriforme. However, viewing a population of Boreal European specimens of G. trabeculosum, not only is the development of the autophragmal apical horn variable, but many specimens also display processes extending from this horn into that of the ectophragm (Plate III, 3, 4). The possible synonymy of G. trabeculosum and G. pyriforme requires further investigation.
Following the present author's examination of the type specimen and other specimens of Gardodinium ordinale Davey, 1974, this species can be confidently assigned to Gardodinium. As yet, the type specimens of G. attenuatum and G. Iowii have not been observed.
Stratigraphic distribution
The type material was described by Gocht (1959), from upper Hauterivian sediments of Germany. The oldest record of G. trabeculosum is given by Heilmann-Clausen ( 1987), from rocks questionably dated as early Valanginian. Other recent reports (see Nohr-Hansen, 1993, p. 56, for exhaustive list of publications recording this taxon), indicate that G. trabeculosum can be found in sediments of early Hauterivian age through into those of the late Aptian in Boreal northwest Europe. However, publications dealing with material from various locations in Canada intimate that this species may be recorded from strata as young as late Albian in age. From the above, the stratigraphic range of this taxon may encompass an early Valanginian-late Albian time span.