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Dingodinium minutum
Dingodinium minutum Dodekova, 1975, p.25, pl.5, figs.13–15. Emendation: Poulsen, 1996, p.82.
Junior homonym: Dingodinium minutum Jiabo, 1978.
Taxonomic junior synonym: Dingodinium scabratum, according to Poulsen (1996, p.82).
Holotype: Dodekova, 1975, pl.5, figs.13-15
Locus typicus: NE Bulgaria
Stratum typicum: Late Bathonian
Original description: Dodekova, 1975, p. 25
Cavate cyst with spheroidal or subspheroidal endoblast and polyhedral periblast. the endophragm is thick. Its surface is covered with granules and pillars of varying dimensions and density. Proximally some neighbouring pillars are joined together or connected with small thin septa and in certain sectors the ornamentalion resembles irregular reticulum. The ornamentation is weaker or is lacking in the area of the furrows. The periphragm is smooth or shagreenate. The cingulum is distinct, broad (4.65Á), helicoidal. The sulcus is marked by a concavity in the periphragm and by a weaker ornamentation on the endophragm, more distinct on the hypotract. Tabulation is evidently present but its determination is difficult. The sutures are marked by very thin fine ribs. The structure of the apex is unknown. All observed specimens have archaeopyle, which affects the endophragm and the periphragm. The precingular file of plates has 6 nearly equidimensional trapezium-like plates. The postcingular file includes 5 plates and one anterior intercalary plate--1p. The antapical plate is ventrally inclined and at the boundary with 5""" and 1p forms a fold, analogical to the fold in Endoscinium luridum (Deflandre). Tabulation: ?4, ?2, 6" 5""", 1p, 1"""" (sic).The periphragm is dorsally very close to or touches the endophragm. The archaeopyle is apical.
Affinities:
Dodekova, 1975, p. 25: The more distinct tabulation and ornamentation distinguish D. minulum from all known species of the genus.
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Poulsen 1996, p. 82-83
Dingodinium minutum Dodekova 1975 emend. nov., Pl. 16, Figs. 2-7
Dingodinium minutum Dodekova, 1975, p. 25, pl. 5, figs. 13-15.
Dingodinium cf. albertii Ioannides et al., 1976, p. 451-452, pl. 1, figs. 10, 12.
Dingodinium jurassicum Raynaud, 1978, p. 396, pl. 2, fig. 9, text-fig. 5, no. 14.
Parvocavatus scabratus Kumar, 1986, p. 399-400, pl. 5, fig. 3, pl. 6, figs. 4, 6, text-flg. 9.
Dingodinium scabratus Kumar, 1986, Lentin and Williams, 1990, p. 111.
Dingodinium minutum Dodekova, 1975, Dodekova, 1990, p. 11-12, pl. 7, figs. 9-11.
Emended description. A camocavate cyst with a short apical horn. The endophragm shows a sculpture ranging from scabrate to granulate. The periphragm is thin and smooth. The expression of the paratabulation varies from absent to distinct. Paratabulation formula (when expressed): 4", ?a, 6", ?c, 5"", 1p, 1"", 5s. Archeopyle apical, type tA/tA.
Remarks. Specimens of Dingodinium minutum with a smooth periphragm and a granular endophragm show variability in the degree of the expression of paratabulation and in the numbers and size of the granulae on the endophragm. Dingodinium minutum and D. scabratus are believed to be members of a morphological plexus, which shows variation in the morphological features both within samples and through time. The diagnosis of D. minutum is emended to include these variations.
The paratabulation of D. minutum was reinterpreted by Dodekova (1990) and is followed in this emended diagnosis (see above). Eleven specimens of the type collection have an apical archeopyle without involvement of intercalary paraplates (Dodekova, 1990).
Dingodinium harsveldtii shows no indication of paratabulation, except for archeopyle sutures (Herngreen et al., 1984). In the "differential diagnosis" of D. harsveldtii Herngreen et al. (1984) did not compare this species with D. minutum. Dodekova (1990) found D. harsveldtii in the Middle Late Callovian of northern Bulgaria, and found that the Bulgarian specimens of D. harsveldtii differed from the type material in having more prominent granulate ornament on the endophragm (Dodekova, 1990). Dingodinium harsveldtii may prove to be a subspecies of D. minutum.
Dingodinium? albertii Sarjeant 1966, like D. minutum, has a blunt horn with a slightly rounded tip. The endocyst is smooth to minutely granular with a dense cover of small conical tubercles less than 1 Ám high. The archeopyle is intercalary according to Sarjeant (1966). According this species is only provisionally referred to Dingodinium.
Dingodinium cf. albertii of Ioannides et al., (1976) is similar to those specimens of D. minutum with a weak paratabulation and distinct granulae on the endophragm. Dingodinium jurassicum of Raynaud (1978) is a verrucate to granulate species (Raynaud, in Herngreen et al., 1984), and is here regarded as conspecific with D. minutum. The surface of the endocyst of Dingodinium jurassicum Cookson and Eisenack 1958 (Cookson and Eisenack, 1958) is covered with numerous small irregular spines. A poorly marked horn may be developed on this species.
Occurrences.
Dingodinium minutum was first described from the Middle Jurassic (Dodekova, 1975). Davey (1982) reported D. minutum from the Middle Volgian to Early Valanginian.
Dodekova (1990) recorded D. minutum from the Late Bathonian to Kimmeridgian. The range of D.
jurassicum of Raynaud (1978) is Late Callovian to Middle Volgian (Raynaud, 1978). Davies (1983) recorded this species in the Toarcian of the Sverdrup Basin. In this study, it is recorded from the Scriniodinium crystallinum Zone, Subzone b to the Gochteodinia villosa Zone, Endoscrinium pharo Subzone of Denmark, and from the Planula to Scythicus Zones of Poland.
Junior homonym: Dingodinium minutum Jiabo, 1978.
Taxonomic junior synonym: Dingodinium scabratum, according to Poulsen (1996, p.82).
Holotype: Dodekova, 1975, pl.5, figs.13-15
Locus typicus: NE Bulgaria
Stratum typicum: Late Bathonian
Original description: Dodekova, 1975, p. 25
Cavate cyst with spheroidal or subspheroidal endoblast and polyhedral periblast. the endophragm is thick. Its surface is covered with granules and pillars of varying dimensions and density. Proximally some neighbouring pillars are joined together or connected with small thin septa and in certain sectors the ornamentalion resembles irregular reticulum. The ornamentation is weaker or is lacking in the area of the furrows. The periphragm is smooth or shagreenate. The cingulum is distinct, broad (4.65Á), helicoidal. The sulcus is marked by a concavity in the periphragm and by a weaker ornamentation on the endophragm, more distinct on the hypotract. Tabulation is evidently present but its determination is difficult. The sutures are marked by very thin fine ribs. The structure of the apex is unknown. All observed specimens have archaeopyle, which affects the endophragm and the periphragm. The precingular file of plates has 6 nearly equidimensional trapezium-like plates. The postcingular file includes 5 plates and one anterior intercalary plate--1p. The antapical plate is ventrally inclined and at the boundary with 5""" and 1p forms a fold, analogical to the fold in Endoscinium luridum (Deflandre). Tabulation: ?4, ?2, 6" 5""", 1p, 1"""" (sic).The periphragm is dorsally very close to or touches the endophragm. The archaeopyle is apical.
Affinities:
Dodekova, 1975, p. 25: The more distinct tabulation and ornamentation distinguish D. minulum from all known species of the genus.
-----------------------------------
Poulsen 1996, p. 82-83
Dingodinium minutum Dodekova 1975 emend. nov., Pl. 16, Figs. 2-7
Dingodinium minutum Dodekova, 1975, p. 25, pl. 5, figs. 13-15.
Dingodinium cf. albertii Ioannides et al., 1976, p. 451-452, pl. 1, figs. 10, 12.
Dingodinium jurassicum Raynaud, 1978, p. 396, pl. 2, fig. 9, text-fig. 5, no. 14.
Parvocavatus scabratus Kumar, 1986, p. 399-400, pl. 5, fig. 3, pl. 6, figs. 4, 6, text-flg. 9.
Dingodinium scabratus Kumar, 1986, Lentin and Williams, 1990, p. 111.
Dingodinium minutum Dodekova, 1975, Dodekova, 1990, p. 11-12, pl. 7, figs. 9-11.
Emended description. A camocavate cyst with a short apical horn. The endophragm shows a sculpture ranging from scabrate to granulate. The periphragm is thin and smooth. The expression of the paratabulation varies from absent to distinct. Paratabulation formula (when expressed): 4", ?a, 6", ?c, 5"", 1p, 1"", 5s. Archeopyle apical, type tA/tA.
Remarks. Specimens of Dingodinium minutum with a smooth periphragm and a granular endophragm show variability in the degree of the expression of paratabulation and in the numbers and size of the granulae on the endophragm. Dingodinium minutum and D. scabratus are believed to be members of a morphological plexus, which shows variation in the morphological features both within samples and through time. The diagnosis of D. minutum is emended to include these variations.
The paratabulation of D. minutum was reinterpreted by Dodekova (1990) and is followed in this emended diagnosis (see above). Eleven specimens of the type collection have an apical archeopyle without involvement of intercalary paraplates (Dodekova, 1990).
Dingodinium harsveldtii shows no indication of paratabulation, except for archeopyle sutures (Herngreen et al., 1984). In the "differential diagnosis" of D. harsveldtii Herngreen et al. (1984) did not compare this species with D. minutum. Dodekova (1990) found D. harsveldtii in the Middle Late Callovian of northern Bulgaria, and found that the Bulgarian specimens of D. harsveldtii differed from the type material in having more prominent granulate ornament on the endophragm (Dodekova, 1990). Dingodinium harsveldtii may prove to be a subspecies of D. minutum.
Dingodinium? albertii Sarjeant 1966, like D. minutum, has a blunt horn with a slightly rounded tip. The endocyst is smooth to minutely granular with a dense cover of small conical tubercles less than 1 Ám high. The archeopyle is intercalary according to Sarjeant (1966). According this species is only provisionally referred to Dingodinium.
Dingodinium cf. albertii of Ioannides et al., (1976) is similar to those specimens of D. minutum with a weak paratabulation and distinct granulae on the endophragm. Dingodinium jurassicum of Raynaud (1978) is a verrucate to granulate species (Raynaud, in Herngreen et al., 1984), and is here regarded as conspecific with D. minutum. The surface of the endocyst of Dingodinium jurassicum Cookson and Eisenack 1958 (Cookson and Eisenack, 1958) is covered with numerous small irregular spines. A poorly marked horn may be developed on this species.
Occurrences.
Dingodinium minutum was first described from the Middle Jurassic (Dodekova, 1975). Davey (1982) reported D. minutum from the Middle Volgian to Early Valanginian.
Dodekova (1990) recorded D. minutum from the Late Bathonian to Kimmeridgian. The range of D.
jurassicum of Raynaud (1978) is Late Callovian to Middle Volgian (Raynaud, 1978). Davies (1983) recorded this species in the Toarcian of the Sverdrup Basin. In this study, it is recorded from the Scriniodinium crystallinum Zone, Subzone b to the Gochteodinia villosa Zone, Endoscrinium pharo Subzone of Denmark, and from the Planula to Scythicus Zones of Poland.