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Umbriadinium mediterraneense
Umbriadinium mediterraneense Bucefalo Palliani and Riding, 1997a, p.199–201, pl.1, figs.1–9; text-figs.8A–E.
This name was not validly published in Bucefalo Palliani and Mattioli (1995, p.60) since these authors did not provide a description.
Holotype: Bucefalo Palliani and Riding, 1997a, pl.1, fig.1.
Age: late Pliensbachian–early Toarcian.
Original description (Bucefalo Palliani and Riding, 1997a):
Umbriadinium mediterraneense sp. nov. Plate 1, figs. 1-9; Text-Figure 8
Holotype. Slide PO 2.60 (2p), England Finder co-ordinate G28/1-3 (Plate 1, fig. 1). Length 32 µm, width 24 urn, average spine length 5.5 µm.
Repository. Department of Earth Sciences, University of Perugia, Italy.
Type Locality. Pozzale section, sample PO 2.60,2.60 m from the base, Marne di Monte Serrone Formation, Central Italy (Text-Figure 5).
Stratigraphic Horizon. Lower Jurassic, upper Pliensbachian (Domerian, Pleuroceras spinatum Zone) to lower Toarcian (Dactylioceras tenuicostatum Zone). Umbriadinium mediterraneense sp. nov. first appears immediately below the first occurrence of the calcareous nannofossil Calyculus and disappears before the first occurrence of the calcareous nannofossil Discorhabdus ignotus (Gorka 1957) Perch-Nielsen 1968.
Derivatio Nominis. From the Mediterranean province of the Tethyan Realm.
Diagnosis. Small, ellipsoidal, proximochorate to skolochorate, acavate dinoflagellate cysts. Autophragm microscabrate, ornamented by intratabular spines. The spines indicate the presence of eight or nine series of paraplates. Parasutural ridges frequently define the paracingulum. Archeopyle of combination (disintegration) type, involving the n4, n3 and n2 paraplate series.
Description. Subspherical to elongate ellipsoidal, proximochorate to chorate, acavate dinoflagellate cysts. The maximum diameter is less than 50 µm (i.e. "small" of Stover and Evitt, 1978, p. 5). Autophragm thin, microscabrate, surmounted by slender, solid, distallypointed, intratabular (paraplate-centered) spines. Low, smooth parasutural ridges are frequently developed defining the paracingulum. Intratabular spines indicate the presence of eight or nine latitudinal rows of relatively small, polygonal paraplates. Archeopyle of combination (disintegration) type, involving the quartanterior (n4), tertanterior (n3) and secanterior (n2) paraplate series of Below (1987). Archeopyle formation commences with the quartanterior paraplate series and continues through the tertanterior series; finally, some secanterior paraplates may be involved. The archeopyle formula is t"4 +1"3 + ?"2 . Specimens may exhibit initial, intermediate or final stages of disinte gration archeopyle development. Paracingulum indicated by an extensive equatorial area with rare, randomly inserted spines. Parasulcus is not indicated or may be characterised by low, smooth parasutural ridges.
Overall length of cyst: minimum 23 µm, mean 22 µm, maximum 31 µm.
Overall width of cyst: minimum 16 µm, mean 22 µm, maximum 26 µm.
Height of paracingulum: minimum 4 µm, mean 6 µm, maximum 13 µm.
Length of spines: minimum 2 µm, mean 4 µm, maximum 7 µm
(20 specimens measured).
Discussion. Suessia and Umbriadinium are monospecific genera, represented by the species Suessia swabiana Morbey 1975 and U. mediterraneense respectively. Therefore, the comparison of generic and specific characters are identical. Umbriadinium mediterraneense has a compound operculum and therefore differs from the species of Wanneria, which have a simple operculum (Wanneria listen (Stover & Helby 1978) emend. Below 1987 and Wanneria misolensis Below 1987). The species Noricysta fimbriata Bujak and Fisher 1976, Noricysta pannucea Bujak and Fisher 1976, and Noricysta varivallata Bujak & Fisher 1976, are cavate. Beaumontella ?caminuspina (Wall 1965) Below 1987, Beaumontella ?delicata (Wall 1965) Below 1987 and Beaumontella ?langii (Wall 1965) Below 1987 have apical archeopyles. Umbriadinium mediterraneense and the species of Beaumontella have an intratabular ornamentation. The spines in B. langii can be tubiform and truncate, commonly with stellate distal expansions, while U. mediterraneense is characterized by homomorphic spines that are solid, slender and consistently distally pointed. The archeopyle of U. mediterraneense is of disintegration type, in which archeopyle sutures develop to varying degrees along adjacent paraplates without defining an operculum or opercular pieces of constant design or number (Dorhofer and Davies, 1980). The formation of the archeopyle occurs through several phases, involving successive paraplate series, as illustrated in Text-Figure 8. Phase 1 - Quartanterior paraplates separate from each other and from the cyst, while the other series are intact (Text-Figure 8 B). Phase 2 - The progressive loss of tertanterior paraplates begins when some quartanterior paraplates are still attached to the cyst (Text-Figure 8 C). Phase 3 - The loss of secanterior paraplates occurs after the loss of all the quartanterior and tertanterior paraplates (Text-Figure 8 D). Phase 4 - Only some secanterior paraplates detach, while the primanterior series is always intact (Text-Figure 8 E). The paraplates are polygonal and small in size, from 2 µm to 3 µm in diameter. They are visible as singleparaplates belonging to the compound operculum or along the archeopyle sutures, where their boundaries are evident. The suessoid cysts recorded by Baldanza et al. (1995, text-fig. 4) as "Suessiaceae dinoflagellate cyst" from the Lower Jurassic of Hungary are considered to be U. mediterraneense. Umbriadinium mediterraneense has been recorded from the lower Toarcian of Lefkas Island (northwest Greece), the Umbria-Marche area (central Italy) and the Reka Valley (Hungary). The oldest occurrence of the species is in the late Pliensbachian (P. spinatum Zone) of central Italy. In northwest Greece and central Italy, this species apparently becomes extinct within the D. tenuicostatum Zone, whereas, in Hungary it ranges up to the Harpoceras falciferum Zone (Baldanza et al., 1995). This stratigraphic discrepancy may be tentatively explained by special paleoenvironmental characteristics in Hungary or by heterochroneity between the different ammonite biozonations. In northwest Greece and central Italy, the D. tenuicostatum Zone is overlain by the Tethyan Hildaites serpentinus Zone, however, in Hungary, the Boreal H. falciferum Zone lies above the D. tenuicostatum Zone.
This name was not validly published in Bucefalo Palliani and Mattioli (1995, p.60) since these authors did not provide a description.
Holotype: Bucefalo Palliani and Riding, 1997a, pl.1, fig.1.
Age: late Pliensbachian–early Toarcian.
Original description (Bucefalo Palliani and Riding, 1997a):
Umbriadinium mediterraneense sp. nov. Plate 1, figs. 1-9; Text-Figure 8
Holotype. Slide PO 2.60 (2p), England Finder co-ordinate G28/1-3 (Plate 1, fig. 1). Length 32 µm, width 24 urn, average spine length 5.5 µm.
Repository. Department of Earth Sciences, University of Perugia, Italy.
Type Locality. Pozzale section, sample PO 2.60,2.60 m from the base, Marne di Monte Serrone Formation, Central Italy (Text-Figure 5).
Stratigraphic Horizon. Lower Jurassic, upper Pliensbachian (Domerian, Pleuroceras spinatum Zone) to lower Toarcian (Dactylioceras tenuicostatum Zone). Umbriadinium mediterraneense sp. nov. first appears immediately below the first occurrence of the calcareous nannofossil Calyculus and disappears before the first occurrence of the calcareous nannofossil Discorhabdus ignotus (Gorka 1957) Perch-Nielsen 1968.
Derivatio Nominis. From the Mediterranean province of the Tethyan Realm.
Diagnosis. Small, ellipsoidal, proximochorate to skolochorate, acavate dinoflagellate cysts. Autophragm microscabrate, ornamented by intratabular spines. The spines indicate the presence of eight or nine series of paraplates. Parasutural ridges frequently define the paracingulum. Archeopyle of combination (disintegration) type, involving the n4, n3 and n2 paraplate series.
Description. Subspherical to elongate ellipsoidal, proximochorate to chorate, acavate dinoflagellate cysts. The maximum diameter is less than 50 µm (i.e. "small" of Stover and Evitt, 1978, p. 5). Autophragm thin, microscabrate, surmounted by slender, solid, distallypointed, intratabular (paraplate-centered) spines. Low, smooth parasutural ridges are frequently developed defining the paracingulum. Intratabular spines indicate the presence of eight or nine latitudinal rows of relatively small, polygonal paraplates. Archeopyle of combination (disintegration) type, involving the quartanterior (n4), tertanterior (n3) and secanterior (n2) paraplate series of Below (1987). Archeopyle formation commences with the quartanterior paraplate series and continues through the tertanterior series; finally, some secanterior paraplates may be involved. The archeopyle formula is t"4 +1"3 + ?"2 . Specimens may exhibit initial, intermediate or final stages of disinte gration archeopyle development. Paracingulum indicated by an extensive equatorial area with rare, randomly inserted spines. Parasulcus is not indicated or may be characterised by low, smooth parasutural ridges.
Overall length of cyst: minimum 23 µm, mean 22 µm, maximum 31 µm.
Overall width of cyst: minimum 16 µm, mean 22 µm, maximum 26 µm.
Height of paracingulum: minimum 4 µm, mean 6 µm, maximum 13 µm.
Length of spines: minimum 2 µm, mean 4 µm, maximum 7 µm
(20 specimens measured).
Discussion. Suessia and Umbriadinium are monospecific genera, represented by the species Suessia swabiana Morbey 1975 and U. mediterraneense respectively. Therefore, the comparison of generic and specific characters are identical. Umbriadinium mediterraneense has a compound operculum and therefore differs from the species of Wanneria, which have a simple operculum (Wanneria listen (Stover & Helby 1978) emend. Below 1987 and Wanneria misolensis Below 1987). The species Noricysta fimbriata Bujak and Fisher 1976, Noricysta pannucea Bujak and Fisher 1976, and Noricysta varivallata Bujak & Fisher 1976, are cavate. Beaumontella ?caminuspina (Wall 1965) Below 1987, Beaumontella ?delicata (Wall 1965) Below 1987 and Beaumontella ?langii (Wall 1965) Below 1987 have apical archeopyles. Umbriadinium mediterraneense and the species of Beaumontella have an intratabular ornamentation. The spines in B. langii can be tubiform and truncate, commonly with stellate distal expansions, while U. mediterraneense is characterized by homomorphic spines that are solid, slender and consistently distally pointed. The archeopyle of U. mediterraneense is of disintegration type, in which archeopyle sutures develop to varying degrees along adjacent paraplates without defining an operculum or opercular pieces of constant design or number (Dorhofer and Davies, 1980). The formation of the archeopyle occurs through several phases, involving successive paraplate series, as illustrated in Text-Figure 8. Phase 1 - Quartanterior paraplates separate from each other and from the cyst, while the other series are intact (Text-Figure 8 B). Phase 2 - The progressive loss of tertanterior paraplates begins when some quartanterior paraplates are still attached to the cyst (Text-Figure 8 C). Phase 3 - The loss of secanterior paraplates occurs after the loss of all the quartanterior and tertanterior paraplates (Text-Figure 8 D). Phase 4 - Only some secanterior paraplates detach, while the primanterior series is always intact (Text-Figure 8 E). The paraplates are polygonal and small in size, from 2 µm to 3 µm in diameter. They are visible as singleparaplates belonging to the compound operculum or along the archeopyle sutures, where their boundaries are evident. The suessoid cysts recorded by Baldanza et al. (1995, text-fig. 4) as "Suessiaceae dinoflagellate cyst" from the Lower Jurassic of Hungary are considered to be U. mediterraneense. Umbriadinium mediterraneense has been recorded from the lower Toarcian of Lefkas Island (northwest Greece), the Umbria-Marche area (central Italy) and the Reka Valley (Hungary). The oldest occurrence of the species is in the late Pliensbachian (P. spinatum Zone) of central Italy. In northwest Greece and central Italy, this species apparently becomes extinct within the D. tenuicostatum Zone, whereas, in Hungary it ranges up to the Harpoceras falciferum Zone (Baldanza et al., 1995). This stratigraphic discrepancy may be tentatively explained by special paleoenvironmental characteristics in Hungary or by heterochroneity between the different ammonite biozonations. In northwest Greece and central Italy, the D. tenuicostatum Zone is overlain by the Tethyan Hildaites serpentinus Zone, however, in Hungary, the Boreal H. falciferum Zone lies above the D. tenuicostatum Zone.