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Labyrinthodinium truncatum ssp. truncatum
From Fensome et al., 2019:
Labyrinthodinium truncatum Autonym. Holotype: Piasecki, 1980, pl.2, figs.9–11; Fensome et al., 1995, figs.1–3 --
p.1855; Fauconnier and Masure, 2004, pl.51, figs.5–6.
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synonyms:
Cordosphaeridium sp. II Manum. - MANUM 1976, pl.3, figs.4,5,8
Labyrinthodinium truncatum, PIASECKI 1980:67, pl.2, figs.9-11, pl. 3, fig.2, pl.6, figs.3-4
Original diagnosis: de Verteuil and Norris, 1996, p. 150: Labyrinthodinium truncatum subsp. truncatum
Subspecies of Labyrinthodinium truncatum Piasecki 1980 having generally less than 50 processes that are greater than or equal to 4 µm in length and have distal platforms.
Original description:de Verteuil and Norris, 1996, p.150: Labyrinthodinium truncatum subsp. truncatum
Small, spherical, proximochorate cysts with apical archeopyle, Type (tA). The wall comprises homogeneous pedium, <0.25 µm thick, fused with a meshwork of spongy luxuriae 0.5 µm to 2.0 µm thick, that supports several intratabular processes. Alveoles in the spongy luxuriae are irregular in shape and size, with maximum dimension up to ca. 1.0 µm. Processes are formed from scabrate membranes with scattered micro-granules and are proximally connected by low, concave septa that form an open, irregular reticulum over the spongy luxuriae. Septa extend up the length of processes as solid linear ridges, providing loci of support and giving them a boxlike, tubiform shape. The processes are hollow and distally flared with small polygonal platforms that have ragged margins. Processes occur in clear latitudinally aligned series suggestive of tabulation, but details are elusive since some fields may have two or more processes.
Dimensions: Maximum diameter excluding processes 22(27.6)35 µm; wall thickness 0.75 to 2.0 µm; processes 4 to 7 µm long. Twenty-one specimens measured.
Discussion: de Verteuil and Norris, 1996, p.150
Labyrinthodinium truncatum is a species with considerable variation in size, thickness of the spongy luxuriae, and number, length and degree of complexity of the appendages. There is a simple relationship among these characters in the autonym subspecies, Labyrinthodinium truncatum subsp. truncatum. Larger specimens tend to have thicker spongy luxuriae and fewer, longer processes that distally have better developed platforms. As a result, the processes on smaller specimens appear nontabular.
Strauss and Lund (1992) erected the taxon Labyrinthodinium truncatum var. reductum for specimens "...with a characteristic reduction of the complex process structure. The network of process-bearing crests is reduced to some isolated patches, which appear to be intratabular at least near the archeopyle
margin" (1992: 164). The autoblast diameter of their new variety, without appendages, ranged from 26 µm to 38 µm, with appendages from 6 µm to 8 µm in length. Thus, the morphotype concept of this variety appears to be a subset of the Labyrinthodinium truncatum subsp. truncatum morphotype concept, and consists of specimens with well developed processes that clearly indicate an intratabular distribution (e.g. pl. 15, figs. 9-11).
United States Atlantic margin specimens of Labyrinthodinium truncatum subsp. truncatum are morphologically the same as the Danish type material in most respects. The only difference seems to be that our specimens are all smaller than the largest Danish specimens. These latter range to 40 µm in diameter, excluding the processes, with spongy luxuriae 3 µm thick and processes up to 10 µm long.
Comparison. de Verteuil and Norris, 1996, p.150
Labyrinthodinium truncatum subsp. truncatum differs from the subspecies Labyrinthodinium truncatum subsp. modicum primarily in having longer appendages. However, in light of the morphological correlations between size and wall development in this subspecies, larger specimens of Labyrinthodinium truncatum subsp. truncatum also tend to have thicker luxuriae and fewer appendages than specimens of Labyrinthodinium truncatum subsp. modicum.
Occurrence: Middle through upper Miocene (DN4 - DN9) in the Salisbury Embayment. Persistently present but never abundant throughout its range. Refer below, and to de Verteuil and Norris (Part I, this volume), for discussion of occurrences of Labyrinthodinium truncatum subsp. truncatum and Labyrinthodinium truncatum subsp. modicum in the Salisbury Embayment.
Remarks.de Verteuil and Norris, 1996, p.150
Head et al. (1989a) and de Verteuil and Norris (Part I, this volume) list North Atlantic records of Labyrinthodinium truncatum subsp. truncatum and discuss its biostratigraphy. Martin (1991) recovered specimens of Labyrinthodinium truncatum subsp. truncatum from undifferentiated lower-middle Miocene sediments of the Murray Basin, southeastern Australia.
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Labyrinthodinium truncatum Autonym. Holotype: Piasecki, 1980, pl.2, figs.9–11; Fensome et al., 1995, figs.1–3 --
p.1855; Fauconnier and Masure, 2004, pl.51, figs.5–6.
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synonyms:
Cordosphaeridium sp. II Manum. - MANUM 1976, pl.3, figs.4,5,8
Labyrinthodinium truncatum, PIASECKI 1980:67, pl.2, figs.9-11, pl. 3, fig.2, pl.6, figs.3-4
Original diagnosis: de Verteuil and Norris, 1996, p. 150: Labyrinthodinium truncatum subsp. truncatum
Subspecies of Labyrinthodinium truncatum Piasecki 1980 having generally less than 50 processes that are greater than or equal to 4 µm in length and have distal platforms.
Original description:de Verteuil and Norris, 1996, p.150: Labyrinthodinium truncatum subsp. truncatum
Small, spherical, proximochorate cysts with apical archeopyle, Type (tA). The wall comprises homogeneous pedium, <0.25 µm thick, fused with a meshwork of spongy luxuriae 0.5 µm to 2.0 µm thick, that supports several intratabular processes. Alveoles in the spongy luxuriae are irregular in shape and size, with maximum dimension up to ca. 1.0 µm. Processes are formed from scabrate membranes with scattered micro-granules and are proximally connected by low, concave septa that form an open, irregular reticulum over the spongy luxuriae. Septa extend up the length of processes as solid linear ridges, providing loci of support and giving them a boxlike, tubiform shape. The processes are hollow and distally flared with small polygonal platforms that have ragged margins. Processes occur in clear latitudinally aligned series suggestive of tabulation, but details are elusive since some fields may have two or more processes.
Dimensions: Maximum diameter excluding processes 22(27.6)35 µm; wall thickness 0.75 to 2.0 µm; processes 4 to 7 µm long. Twenty-one specimens measured.
Discussion: de Verteuil and Norris, 1996, p.150
Labyrinthodinium truncatum is a species with considerable variation in size, thickness of the spongy luxuriae, and number, length and degree of complexity of the appendages. There is a simple relationship among these characters in the autonym subspecies, Labyrinthodinium truncatum subsp. truncatum. Larger specimens tend to have thicker spongy luxuriae and fewer, longer processes that distally have better developed platforms. As a result, the processes on smaller specimens appear nontabular.
Strauss and Lund (1992) erected the taxon Labyrinthodinium truncatum var. reductum for specimens "...with a characteristic reduction of the complex process structure. The network of process-bearing crests is reduced to some isolated patches, which appear to be intratabular at least near the archeopyle
margin" (1992: 164). The autoblast diameter of their new variety, without appendages, ranged from 26 µm to 38 µm, with appendages from 6 µm to 8 µm in length. Thus, the morphotype concept of this variety appears to be a subset of the Labyrinthodinium truncatum subsp. truncatum morphotype concept, and consists of specimens with well developed processes that clearly indicate an intratabular distribution (e.g. pl. 15, figs. 9-11).
United States Atlantic margin specimens of Labyrinthodinium truncatum subsp. truncatum are morphologically the same as the Danish type material in most respects. The only difference seems to be that our specimens are all smaller than the largest Danish specimens. These latter range to 40 µm in diameter, excluding the processes, with spongy luxuriae 3 µm thick and processes up to 10 µm long.
Comparison. de Verteuil and Norris, 1996, p.150
Labyrinthodinium truncatum subsp. truncatum differs from the subspecies Labyrinthodinium truncatum subsp. modicum primarily in having longer appendages. However, in light of the morphological correlations between size and wall development in this subspecies, larger specimens of Labyrinthodinium truncatum subsp. truncatum also tend to have thicker luxuriae and fewer appendages than specimens of Labyrinthodinium truncatum subsp. modicum.
Occurrence: Middle through upper Miocene (DN4 - DN9) in the Salisbury Embayment. Persistently present but never abundant throughout its range. Refer below, and to de Verteuil and Norris (Part I, this volume), for discussion of occurrences of Labyrinthodinium truncatum subsp. truncatum and Labyrinthodinium truncatum subsp. modicum in the Salisbury Embayment.
Remarks.de Verteuil and Norris, 1996, p.150
Head et al. (1989a) and de Verteuil and Norris (Part I, this volume) list North Atlantic records of Labyrinthodinium truncatum subsp. truncatum and discuss its biostratigraphy. Martin (1991) recovered specimens of Labyrinthodinium truncatum subsp. truncatum from undifferentiated lower-middle Miocene sediments of the Murray Basin, southeastern Australia.
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