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Late Silurian trilete spores from northern Jiangsu, China
Review of Palaeobotany and Palynology 111 (2000) 111–125 www.elsevier.nl/locate/revpalbo
Late Silurian trilete spores from northern Jiangsu, China Y. Wang *, J. Li Nanjing institute of Geology & Palaeontology, Academia Sinica, Nanjing 210008, People’s Republic of China Received 6 July 1999; accepted for publication 8 March 2000
Abstract The Late Silurian is generally considered to a particular significant key period in the study of early land vascular plants. A trilete spore assemblage of the Upper Silurian is described from northern Jiangsu, China. This assemblage comprises 11 genera and 20 species of trilete spores (including laevigate, apiculate, perinotrilite, patinate, rarely distally murornate and equatorially crassitate, and three indeterminate trilete miospores forms). It has similarities to those described from coeval assemblages from around the world (e.g., England and South Wales; Tripolitania, Libya; Cornwallis Island, Canadian Arctic; Northwest Spain). The rare cryptospore, only one specimen (Tetrahedraletes sp.) had been found to be associated with the Chinese trilete spore assemblage. The discovery of the trilete spores from Late Silurian rocks indicates the existence of early land plants, some possibly vascular, at that time in northern Jiangsu, China. © 2000 Elsevier Science B.V. All rights reserved. Keywords: China; Late Silurian; northern Jiangsu; trilete spores
1. Introduction The Late Silurian is generally considered to a particularly significant period in the study of early land vascular plants. Some important fossil plants have been found and studied, such as Cooksonia, Barawanagthia etc. However, the Ordovician and Silurian land plant record is either rare to nonexistent or is poorly preserved. The presence in the fossil record of the trilete spores is thought to be an important in the study of early land vascular plants. Upper Silurian trilete spores have been reported from several localities (Richardson and Lister, 1969; Richardson and Ioannides, 1973; McGregor and Narbonne, 1978; Richardson and McGregor, 1986; Cramer, 1966a,b). Richardson and Lister * Corresponding author. Fax: +86-25-3357026. E-mail address: [email protected] ( Y. Wang)
(1969) described the spore assemblages of the Upper Silurian from the Welsh Borders and South Wales; Richardson and Ioannides (1973) published a study on Upper Silurian ( Upper Wenlock to Pridoli) palynomorphs from Tanezzuft and Acacus Formations, Tripolitania, North Africa; McGregor and Narbonne (1978) studied Upper Silurian trilete spores from Read Bay Formation, Cornwallis Island, Canadian Arctic; Cramer (1966a, b) described the Upper Silurian trilete spores from northwest Spain. Richardson and McGregor (1986) summarized the Silurian spore zones of the Old Red Sandstone continent and adjacent areas, and three spore assemblage zones were established in the Upper Silurian. Data on the well-dated beds of the Late Silurian from China is scarce. Late Silurian trilete spores have been reported from Yunnan ( Fang et al., 1994; Gao, 1981) and Xinjiang (Gao, 1981; Cai et al., 1993). Both reports list taxa but with neither
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descriptions nor illustrations. The present paper reports the discovery of Late Silurian (Late Ludlow–Early Pridoli) trilete spores from a borehole in northern Jiangsu and describes 20 taxa with illustrations.
2. Locality and geological setting The material is from borehole Nc-2 situated 17.5 km south of Dafeng County, northern Jiangsu, China (Fig. 1). Samples (numbers: Nc2-4, Nc-2-5, Nc-2-6) collected from between 2539 and 2542 m are composed of greyish mudstone intercalated with silty mudstones and argillaceous siltstones, yield trilete spores, acritarchs, chitinozoans, scolecodonts, tubular structures and ‘plant’derived cuticles (Fig. 2). Geng et al. (1997, 1999) published results of chitinozoans from Borehole Nc-2. Eisenackitina rimosa, element of Angochitina sinica Biozone, occur in 2542.2 m down in Borehole Nc-2. Fungochitinia kosovensis, Grahnichitina lagenomorpha, as the main elements of F. kosovensis Biozone, occurs 2519.6 m down in Borehole Nc-2. The A. sinica Biozone is correlated approximately with the formosus graptolite Biozone and thought to be
Late Ludlow in age (Geng et al., 1997; Schweineberg, 1987). The F. kosovensis Biozone occurs in the Prague Basin with graptolites of the parultimus–ultimus Biozone and is dated at Early Pridoli. The 2539–2542 m part of Borehole Nc-2 is hence Late Ludlow–Early Pridoli in age. The occurrence of acritarchs, chitinozoans and scolecodonts suggests a marine environment of the strata in question. However, the low-diversity composition of the acritarchs, mainly Leiosphaerids and Dactilofusids, and the association of tubular structures and ‘plant’-derived cuticles from the clastic rocks favour the conclusion that the sporebearing strata are of littoral facies with rich terrigenous deposition.
3. Sampling, techniques The rock samples are greyish mudstones. Trilete spores were extracted using standard HCl–HF– HCl acid maceration techniques twice. The organic residue was sieved using a 10 mm mesh. For microscopic observation, materials were mounted on glass coverslips and the coverslips attached to glass slides using ‘Elvacite’ plastic mounting medium. Photomicrographs were taken on FP3 film using a Zeiss photomicroscope III. All slides are stored in the Nanjing Institute of Geology and Palaeontology, Academia Sinica.
4. Systematic palaeontology Genera and species described below are considered as form genera and species based purely on arbitrary morphological criteria. Anteturma Sporites H. Potonie´, 1893 Turma Triletes Reinsch, 1891 Subturma Azonotriletes Luber, 1935 Infraturma Laevigati Bennie and Kidston, emend. Potonie´ and Kremp, 1954. Fig. 1. Index map of the location.
Genus RETUSOTRILETES Naumova, emend Richardson, 1965 (not Streel, 1964)
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Fig. 2. Stratigraphic column of Nc-2 borehole and distribution of the trilete spores and chitinozoans.
Type species: Retusotriletes pychovii Naumova 1953 ( lectotype species of Richardson, 1965) Retusotriletes cf. warringtonii Richardson and Lister, 1969 (Plate I, 2 and 3) Figured specimens: Plate I, 2 and 3. Depth of core: 2539–2542 m, Upper Ludlow– Lower Pridoli. Description: Amb subtriangular with convex sides and rounded apices; suturae sinuous, nearly equal spore radius, accompanied by lips, ca. 0.5–1.0 mm high; curvaturae perfect present, coincide with the
equator; exine, ca. 1.0–2.0 mm in thickness; secondary folds common. Dimensions: 25–35m, six specimens measured. Comparison: The specimens are similar to that of Retusotriletes cf. warringtonii described by Richardson and Ioannides (1973, p. 272, plate 1, figs. 9–11) in size and features; and larger in size than that of R. warringtonii [22–32 mm, given by Richardson and Lister (1969)]. Retusotriletes cf. dubius (Eisenack) Richardson, 1965 (Plate I, 4)
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PLATE I
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Figured specimen: Plate I, 4. Depth of core: 2539–2542 m, Upper Ludlow– Lower Pridoli. Description: Amb subtriangular with convex sides and rounded apices; suturae straight or slightly sinuous, slightly gaping, ca. 2/3–3/4 of radius in length; curvaturae perfectae present. A triangular, slightly darkened, contact area appears, extending ca. 2/3 to 3/4 of the radius. Exine, ca. 2.5–4.0 mm in thickness, slight by thicker interradially. Dimensions: 30–36 mm, four specimens measured. Comparison: Retusotriletes dubius Richardson, 1965, has a larger size range [56–110 mm, Richardson (1965); 56–64 mm, Richardson and Lister (1969)]. The present specimens are similar to that of R. cf. dubius described by Richardson and Ioannides (1973, p. 272, plate 1, figs. 12–13) in size, however, exine of the present specimens is thicker than those of Richardson and Ioannides (1973, 272, Plate 1, 12–13).
Depth of core: 2539–2542 m. Upper Ludlow– Lower Pridoli. Description: Amb subtriangular with convex sides and rounded apices; suturae 3/4–4/5 of radius, slightly gaping, accompanied by lips, ca. 1.0 mm high; curvaturae perfectae coincident with the equator; contact areas slightly depressed; exine laevigate, 2.0–2.5 mm in thickness; secondary folds common. Dimension: Only one specimen, 63 mm in diameter. Comparison: Only one specimen show the features of this species. It is similar to those of Retusotriletes sp. B described by Richardson and Ioannides (1973, p. 272, plate 1, figs. 20 and 21) in size (31– 64 mm), however, the specimens of Richardson and Ioannides show that the shape of amb is subcircular to oval.
Retusotriletes cf. minor Kedo, 1963 (Plate I, 5)
Type species: Apiculiretusispora brandtii Streel 1964.
Figured specimen: Plate I, 5. Depth of core: 2539–2542 m. Upper Ludlow– Lower Pridoli. Description: Amb circular; suturae extending 2/3– 5/6 of the radius; curvaturae perfectae present, slightly invaginated at the extremities of the rays; exine laevigate, 0.5–1.2 mm in thickness. Dimensions: 21–26 m, three specimens measured. Comparison: The present specimens differ from the type in having the slightly invaginated at apices of curvaturae.
Apiculiretusispora sp. A (Plate I, 9)
Retusotriletes sp. A (Plate I, 1) Figured specimen: Plate I, 1.
Infraturma Apiculati Bennie and Kidston, emend. Potonie´, 1956. Genus APICULIRETUSISPORA Streel, 1964
Figured specimen: Plate I, 9. Depth of core: 2539–2542 m, Upper Ludlow– Lower Pridoli. Description: Amb triangular with convex sides and rounded apices; suturae sinuous, equal spore radius, accompanied by lips, ca. 0.8–1.2 mm high; curvaturae perfectae coincident with the equator; exine distally covered by short spines, 0.5–1.5 mm high, 1.0–1.5 mm in basal diameter, elements closely packed. Dimension: 24–27 mm, three specimens measured. Comparison: The specimens are similar to that of
PLATE I Sample numbers are indicated. Magnification ×1000. 1 Retusotriletes sp. A. Nc-2-4-1. 2 and 3 Retusotriletes cf. warringtonii Richardson et Lister. Nc-2-4-3, Nc-2-4-5. 4 Retusotriletes cf. dubius ( Eisenack) Richardson. Nc-2-4-2. 5 Retusotriletes cf. minor Kedo. Nc-2-4-1. 6 cf. Perotrilites sp. Nc-2-4-3. 7 and 8 Anapiculatisporites sp. Nc-2-4-6. 9 Apiculiretusispora sp. A. Nc-2-4-1. 10 Brochotriletes sp. Nc-2-4-5. 11–15 Apiculiretusispora sp. B. Nc-2-4-2, Nc-2-4-4, Nc-2-4-5, Nc-2-4-6, Nc-2-4-1.
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PLATE II
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Apiculiretusispora. sp. A Richardson and Lister (1969, p. 221, plate 38, fig. 7) in amb, size; however, the present specimens have shorter spines and weaker lips. Comparison to Apiculiretusispora synorea, the latter is characterized by a circular to subcircular amb and without prominent lips. Apiculiretusispora sp. B (Plate I, 11–15) Figured specimens: Plate I, 11–15. Depth of core: 2539 m, Upper Ludlow–Lower Pridoli. Description: Amb circular to subcircular; suturae straight or slightly sinuous, in some cases gaping, and accompanied with lips, ca. 0.5–2.0 mm in width, extending for 3/4–8/9 of spore radius; contact areas laevigate, delimited by curvaturae perfect; exine well defined, ca. 1.0 mm in thickness, outside the contact region sculptured with grana, 1.0–2.0 mm in height, 0.5–1.0 mm in basal diameter, closely packed, ca. 0.5–1.5 mm apart. Dimensions: 34–50 mm, 14 specimens measured. Comparison: These specimens are closely similar to those of Apiculiretusispora sp. C of Richardson and Lister (1969, p. 222, plate 38, fig. 9); however, the exine of latter is covered by minute closely packed sculptural element, ca. 0.5 mm or less. Based on the closely packed grana covered on the exine, the present specimens are different with other species of Apiculiretusispora. Genus ANAPICULATISPORITES Potoni and Kremp, 1954 Type species: Anapiculatisporites isselburgensis Potoni and Kremp, 1954.
Anapiculatisporites sp. (Plate I, 7 and 8) Figured specimens: Plate I, 7 and 8. Depth of core: 2539–2542 m, Upper Ludlow– Lower Pridoli. Description: Amb oval-circular; suturae straight, accompanied by lips, ca. 1.0 mm in width, equal to the spore radius; exine, ca. 0.5–1.0 mm in thickness; distal sculpture with sparse coni, ca. 2–8 mm apart, with circular base ca. 1.0–2.0 mm in diameter, <1 mm high, with sharp tips. Dimension: 23–36 mm, five specimens measured. Comparison: These specimens are closely similar to those of Anapiculatisporites abrepunius Cramer, 1966 (p. 260, plate II, fig. 47), except that they have a sparsely packed sculpture. Infraturma Murornati Potoni and Kremp, 1954 Genus BROCHOTRILETES Naumova, 1953
Naumova
ex
Type species: Brochotriletes foveolatus Naumova 1953 Brochotriletes sp. (Plate I, 10) Figured specimen: Plate I, 10. Depth of core: 2539–2542 m, Upper Ludlow– Lower Pridoli. Description: Amb subtriangular to subcircular; suturae slightly sinuous, accompanied by lips, ca. 1.0 mm in width, extending about entire spore radius; exine thin, 1.0 mm in thickness, sculptured with foveae, 1–2 in diameter, and with narrow, straight, sinuous or meandering ‘channels’. 0.5– 2.0 mm wide and of varying length.
PLATE II Sample numbers are indicated. Magnification ×1000. 1 and 2 Cymbosporites cf. verrucosus Richardson et Lister. Nc-2-4-3. 3–6 Cymbosporites sparseus Y. Wang et J. Li sp. nov. Nc-2-4-3, Nc-2-4-5, Nc-2-4-6. 7 Archaeozonotriletes? sp. Nc-2-4-5. 8 ? Amicosporites sp. Nc-2-4-4. 9 Chelinospora? sp. Nc-2-4-3. 10 Emphanisporites sp. Nc-2-4-3. 11 and 12 Synorisporites sp. Nc-2-4-1. 13 and 14 Cymbosporites sp. Nc-2-4-1, Nc-2-4-3. 15 Type A. Nc-2-4-6. 16 and 17 Type B. Nc-2-4-2. 18 Type C. Nc-2-4-3.
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Dimensions: Only one specimen, 26 mm in diameter. Comparison: Based on amb, suturae, size and sculpture, this specimen is very similar to that of cf. Brochotriletes sp. A of Richardson and Ioannides (1973, pp. 276, 277, plate 4, figs. 5, 6, 8–10), however, curvaturae are present in the African specimens, but not observed here. Genus EMPHANISPORITES McGregor 1961 Type species: Emphanisporites rotatus McGregor 1961. Emphanisporites sp. (Plate II, 10) Figured specimen: Plate II, 10. Depth of core: 2539.00 m, Upper Ludlow–Lower Pridoli. Description: Amb circular; suturae straight, ca. 3/4 of the spore radius, associated with lips, ca. 1– 2 mm, wide; ribs poorly disposed at the equator on proximal face, oriented in an essentially radial fashion, 1–1.5 mm apart, length of ribs ca. 4–6 mm, width ca. 0.5–1 mm; ribs straight or slightly sinuous, with the round end; exine 1.5–2 mm in thickness. distally packed coni/grain, 1–1.5 mm width at the base, and ca. 1 mm high. Dimension: 35 mm, only one specimen. Comparison: Emphanisporites protophanus Richardson and Ioannides (1973, p. 274, plate 2, figs. 8–12, 14 and 15) is similar but is distally laevigate. Subturma Perinotriliti Erdtman 1947. Genus PEROTRILITES ( Erdtman) Couper 1953 Type species: Perotrilites granulatus Couper 1953. Cf. Perotrilites sp. (Plate I, 6) Figured specimen: Plate I, 7. Depth of core: 2539–2542 m. Upper Ludlow– Lower Pridoli. Description: Amb subtriangular with convex sides and rounded apices; suturae slightly sinuous, ca. 4/5 of radius, accompanied by with lips, ca. 0.5– 1.0 mm high; spore two-layered outer layer (‘perine’) thin, diaphanous, exine 2.5–3.5 m in thickness, thinner in the interradial areas, outer separated layer formed the ‘perine’; ‘perine’ smooth, thickness varying from 1–2 to 3–4 mm.
Dimension: 28–35 mm, five specimens measured. Comparison: In the thick exine and the outer separated layer (‘perine’), these specimens are placed in the genus Perotrilites. However, the ‘perine’ of these specimens are smooth and not very clear. Subturma Zonotriletes Waltz, 1935. Infraturma Crassiti Bharadwaj Venkatachala, 1961.
and
Genus AMICOSPORITES Cramer, 1966 Type species: Amicosporites splendidus Cramer, 1966. ?Amicosporites sp. (Plate II, 8) Figured specimen: Plate II, 8. Depth of core: 2539–2542 m, Upper Ludlow– Lower Pridoli. Description: Amb triangular with convex sides and rounded apices; suturae straight, accompanied by lip, ca. 2.0–3.0 mm in width, extending equal the spore radius; exine, ca. 1.0 mm in thickness; at distal side and near equator, a circular ridge, ca. 4.0–5.0 mm in thickness, and ca. 28–30 mm in diameter. Dimensions: Only one specimen, 38 mm. Comparison: Because only one specimen had been found, it is very difficult to show the clear position of the annulate thickening. Based on the general features, this specimen is questioningly placed in the genus Amicosporites. The present specimen differs from A. splendidus Cramer, 1966 (p. 258, plate 11, figs. 31, 40 and 41) by the thicker lip and the circular ridge close equator. Genus SYNORISPORITES Lister, 1969
Richardson
Type species: Synorisporites Richardson and Lister, 1969.
and
downtonensis
Synorisporites sp. (Plate II, 11 and 12) Figured specimen: Plate II, 11 and 12. Depth of core: 2539–2542 m, Upper Ludlow– Lower Pridoli. Description: Amb subtriangular with convex sides and rounded apices; suturae distinct, slightly sinuous, accompanied by low lips, ca. 1.0 mm wide,
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extending equal or near equal to spore radius; curvaturae prefect coincided with equator; equatorially and distally covered with small verrucae; elements rounded in plan. and with flat and pointed apices in profile, ca. 1.0–3.0 mm in basal diameter, 0.5–1.5 mm high, and ca. 0.5–3.0 mm apart. Dimension: 33–36 mm, three specimens measured. Comparison: The present spores differ from Synorisporites sp. A of Richardson and Lister (1969, p. 234, plate 41, figs. 1 and 2) in the shape of amb and some verrucae with pointed apices. Infraturma Patinati Butterworth and Williams 1958.
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tally and equatorially, ca. 3–5 mm in thickness; distal and equatorial ornamentation consisting dominantly of verrucae, 1.2–2.5 mm high, ca. 2.0– 3.0 mm in the basal diameter; in profile elements varying from rounded verrucae to curved apices; in plan, subcircular in shape. Dimension: 20–25 mm, four specimens measured. Comparison: Cymbosporites verrucosus Richardson and Lister, 1969 (p. 241, plate 42, figs. 6–8) has a larger size range (29–52 mm). Cymbosporites sparseus Y. Wang and J. Li sp. nov. (Plate II, 3–6)
Figured specimen: Plate II, 7. Depth of core: 2539 m, Upper Ludlow–Lower Pridoli. Description: Amb triangular with convex sides and rounded apices; suturae, simple, straight, extending ca. 2/3–3/4 of equator spore radius; proximal area with collapsed surface; exine over contact areas thin, and thickest at equator and distal pole; exine at the equator and distal pole, 5–7 mm thick, often faintly corroded near the equator. Dimension: 27–33 mm, four specimens measured. Comparison: The present specimens are corroded near equator, it is possible that the specimens were originally sculptured. So, these specimens are questionably placed in the genus Archaeozonotriletes.
Figured specimens: Plate II, 3–6. Depth of core: 2539–2542 m, Upper Ludlow– Lower Pridoli. Holotype specimen: Plate II, 3 and 4. Description: Amb triangular; suturae straight, ca. 1/2–2/3 of the spore radius; proximal polar region covered by a very thin diaphanous membrane, which is frequently collapsed or completely absent; outline of inner contact area coincides with that of the spore; outside the contact areas, exine 4– 5 mm in thickness; coni confined to the equatorial and distal areas; in profile dominantly biform, based broad sharply tapered, with spine apices, or sometimes with flat, or rounded, apices, width of bases 2.0–3.0 mm, ca. 1.0–3.0 mm high; in plan, bases and apices rounded; sculpture elements sparsely distributed, ca. 3.0–8.0 mm apart (usually ca. 4.0–6.0 mm). Dimension: 25–32 mm, mode 27 mm, eight specimens measured. Comparison: The sparsely distributing coni and small size distinguish this from other species of Cymbosporites.
Genus CYMBOSPORITES Allen 1965
Cymbosporites sp. (Plate II, 13 and 14)
Type species: Cymbosporites cyathus Allen 1956.
Figured specimens: Plate II, 13 and 14. Depth of core: 2539 m, Upper Ludlow–Lower Pridoli. Description: Amb subcircular to circular; suturae slightly sinuous, extending 2/3–3/4 of the spore radius, accompanied with lips, ca. 1.0 mm in width; exine homogeneous, ca. 2–4 mm in thickness, except the central area of proximal surface; central area subcircular to circular, 3/4–4/5 of the spore radius, in some cases, with fine grana, ca. 0.5 mm in diameter.
Genus ARCHAEOZONOTRILETES Naumova, emend. Allen, 1965 Type species: Archaeozonotriletes (Naumova) Allen 1965.
variabilis
Archaeozonotriletes? sp. (Plate II, 7)
Cymbosporites cf. verrucosus Richardson et Lister, 1969 (Plate II, 1 and 2) Figured specimens: Plate II, 1 and 2. Depth of core: 2539 m, Upper Ludlow–Lower Pridoli. Description: Amb circular; suturae usually indistinct, thin, simple, ca. 1/2 of the spore radius; proximal region covered by a thin diaphanous membrane, frequently collapsed; exine thick dis-
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Dimensions: 38–48, 10 specimens measured. Comparison: Based on the feature of the thickness exine and with fine grana, these specimens are placed in the genus Cymbosporites. Genus CHELINOSPORA Allen 1965 Type species: Chelinospora concinna Allen 1965. Chelinospora? sp. (Plate II, 9) Figured specimen: Plate II, 9. Depth of core: 2539 m, Upper Ludlow–Lower Pridoli. Description: Amb subtriangular with convex sides and rounded apices; suturae simple, straight, extending to the inner margin of zone; proximal surface smooth; equatorial thickening, ca. 4.0– 6.0 mm wide; distal surface sparsely covered with muri, forming the irregular reticulum; muri membranous, ca. 1.0–2.5 mm width; lumina, polygonal in shape, ca. 1.5–3 mm in diameter. Dimension: Only one specimen, 30 mm. Comparison: The present specimen is questionably placed in the genus Chelinospora based on the thickness of exine and muri.
elements circular to subcircular in plan, rounded to pointed in profile, ca. 0.8–2.0 mm in width, 0.5– 1.2 mm high, 0.5–2.0 mm apart. Dimensions: 42 mm, only one specimen. Remark: The sculpture is poorly preserved. Type C (Plate II, 18) Figured specimens: Plate II, 18. Depth of core: 2539 m, Upper Ludlow–Lower Pridoli. Description: Amb circular; suturae, straight or slightly sinuous, sometime gaping, extending ca. 3/4–4/5 of equator spore radius; exine over contact areas thin, and thickness at equator and distal pole; exine at the equator and distal pole, ca. 3– 6 mm in thickness; exine at equator slightly thick at the extremities of the rays, ca. 5–6 mm in thickness, and ca. 3–4 mm in the interradial regions; the distal exine with muri; the muri? forming an irregular reticulum. Dimension: 47 mm, only one specimen. Remark: The distribution of muri at the distal is indistinct. If it is true that the muri form the reticulum at the distal, this specimen would belong to genus Chelinospora.
Indeterminate trilete miospores Type A (Plate II, 15) Figured specimen: Plate II, 15. Depth of core: 2539 m, Upper Ludlow–Lower Pridoli. Description: Amb circular; suturae straight, ca. 2/3 of the spore radius; one thickness band along the equator, ca. 3 mm thickness; distal exine densely covered with muri? or coni?; sometimes, muri? appear to form a reticulum; lumina, circular in shape, ca. 1–1.5 mm in diameter; muri? or coni?, ca. 1.5–2.0 mm in 1.0–1.5 mm high. Dimension: 36 mm, only one specimen. Remark: This specimen is poorly preserved. It is very difficult to decide the type of the sculpture elements. Type B (Plate II, 16 and 17) Figured specimens: Plate II, 16 and 17. Depth of core: 2539–2542 m, Upper Ludlow–Lower Pridoli. Description: Amb circular to subtriangular with convex sides and rounded apices; exine at equator? and distally, covered with small coni? or grana?;
5. Composition of the assemblage This spore assemblage consists of 11 genera and 20 species (including three indeterminate types). All trilete spores are recovered from Nc2 core ‘Fentou’ Formation (depth: 2539–2542.9 m). The relative abundance of the trilete spores is shown in Fig. 3. The trilete spores include abundant laevigate spores, apiculate spores, perinotrilite spores, patinate spores, and rarely distally murornate, and equatorially crassitate spores. Laevigate spores comprise only one genus: Retusotriletes, and are ca. 18% of the total spore content. Among these species, Retusotriletes cf. warringtonii is ca. 8%, Retusotriletes cf. dubius, 5% and Retusotriletes cf. minor, 4%. Apiculate spores comprise two genera: Apiculiretusispora and Anapiculatisporites, and make up 30% of the total spore content. The important member is Apiculiretusispora sp. B (19%).
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Fig. 3. Relative abundance of spore taxa.
Perinotrilite spores (cf. Perotrilites sp.), comprise ca. 7% of the total spore content. Patinate spores consist of three genera: Cymbosporites (29%), Archaeozonotriletes? (5%) and Chelinospora? (1%), and comprise of 35% of the total spore content. The dominant taxa are Cymbosporites sp. (13%) and C. sparseus (11%). Murornate spores are represented by two genera: Emphanisporites (1%); and Brochotriletes (1%). Two genera of equatorially crassitate spores occur ?Amicosporites and Synorisporites, and make up ca. 5% of the total spore content. Synorisporites sp. is an important distally murornate spore, and constitutes ca. 4% of the total spore content. It must be pointed that this assemblage mainly consists of trilete spores, only one specimen of cryptospore (Tetrahedraletes sp.) was found.
6. Age of the assemblage This assemblage is dated as Late Ludlow–Early Pridoli on the basis of chitinozoans in overlying/underling beds (Geng et al., 1997, 1999).
The biostratigraphical range of the main members of this assemblage is shown in Fig. 4. Apiculiretusispora is an important genus in this assemblage, comprising ca. 23% in the total of spore content. This genus first appears in the Upper Llandovery of China ( Wang and Ouyang, 1997) but has not been reliably reported below the Gorstian elsewhere. The authors use the presence of Apiculiretusispora spp. to indicate a Ludlow age elsewhere. Retusotriletes cf. dubius is found in the Pridoli (Richardson and Ioannides, 1973; Richardson and Lister, 1969). Brochotriletes sp. is very similar to cf. Brochotriletes sp. A of Richardson and Ioannides, which ranges from Late Ludlow to Pridoli (Richardson and Ioannides, 1973). The important feature is that Synorisporites, Cymbosporites, Emphanisporites, and rarely Amicosporites?, Chelinospora?, appear in this assemblage. Based on the above-mentioned data, it is considered that this assemblage is Late Ludlow–Early Pridoli in age. Richardson and McGregor (1986) established two spore zones from Ludlow to Pridoli from the Old Red Sandstone continent and adjacent
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Fig. 4. The geological distribution of the main trilete spores.
regions. The age of the Synorisporites libycus– ?Lophozonotriletes poecilomorphus Assemblage zone is Ludlow, this zone is characterized by first appearance of proximal radial muri on trilete spores (Emphanisporites), distal murornate sculpture (?Lophozonotriletes, cf. Synorisporites downtonensis), beginning of apiculate sculpture on trilete spores (Apiculiretusispora) and appearance of foveolate sculpture (cf. Brochotriletes), etc.(Richardson and McGregor, 1986). The age of the Synorisporites tripapillatus–Apiculiretusispora spicula Assemblage Zone is Pridoli, this zone is described as first appearance of interradial proximal papillae (S. tripapillatus), distally sculptured patinate spores with thin contact areas (Cymbosporites and Chelinospora), etc.(Richardson and McGregor, 1986). The present spore assemblage comprises of the Synorisporites, Cymbosporites, Brochotriletes, Apiculiretusispora and rarely Emphanisporites, Chelinospora, and has the common features of two assemblage zones of Richardson and McGregor (1986). Richardson (1996) studied Lower and Middle Palaeozoic records of terrestrial palynomorphs, and seven phases have been established. Phase 5 was named as the apiculate–retusoid miospore phase, the geological age ranging from Late Ludlow ( Upper Ludfordian) to Lower Pridoli. This phase is characterized by the appearance of retusoid, evenly granulate to apiculate miospores (Apiculiretusispora) and proximally tripapillate and equatorially crassitate miospores. Compared to the
present spore assemblage described in this paper, the main spore morphologic of Phase 5 appear in our assemblage. The present assemblage is regarded as equivalent Phase 5, and, if so, the geological age would be Late Ludlow–Early Pridoli.
7. Comparison with coeval spores around the world Late Ludlow–Early Pridoli trilete spores are reported from a number of localities including England and South Wales, Tripolitania (Libya), Cornwallis Island (Canadian Arctic) and Northwest Spain. 7.1. England and South Wales Richardson and Lister (1969) and Burgess and Richardson (1995) described the trilete spores from Late Wenlock to Early Devonian of England and South Wales. From the Late Wenlockian, only several laevigate forms were recorded, and this spore assemblage is, in general, less diverse that the present assemblage. The Ludlovian horizons yielded more diverse assemblages than those of Late Wenlockian. Some taxa appear in present assemblage, including Synorisporites, Archaeozonotriletes and Apiculiretusispora. Although common or similar elements to the present assemblage are very rare, the general features of the spore structure are closely similar.
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The main differences are that Cymbosporites, Brochotriletes, Emphanisporites and Perotrilites appear in the present assemblage. The Downtonian (Pridoli) assemblage is akin to the present assemblage, with the following common or similar taxa: Retusotriletes cf. warringtonii, Retusotriletes dubius, Retusotriletes cf. minor, Archaeozonotriletes sp. Apiculiretusispora sp. A, Emphanisporites sp., Perotrilites sp., Synorisporites sp., Cymbosporites cf. verrucosus. However, assemblages from England and South Wales contain abundant Synorisporites and Streelispora; whereas the Chinese assemblage has Brochotriletes, Anapiculatisporites and a few Synorisporites. 7.2. Tripolitania, Libya Richardson and Ioannides (1973) described the spores of the Tanezzuft and Acacus Formations from Tripolitania, and three spore assemblages were established. The spore assemblages range from Late Wenlock to Pridoli. The lower assemblage ( late Wenlock) is characterized by laevigate forms with a few sculptured forms (Emphanisporites, Synorisporites). The present assemblage is more diverse than the lower Libyian assemblage. The middle assemblage (Ludlow) consists of laevigate forms and abundant sculptured forms. The interesting event is the appearance of typical Emphanisporites and the relative abundance of verrucate taxa (Lophozonotriletes, Synorisporites) together with foveolate-reticulate types (cf. Brochotriletes). In comparison to the present assemblage, there are some common or similar taxa, including Retusotriletes cf. warringtonii, Retusotriletes minor, Archaeozonotriletes sp., Emphanisporites sp., Synorisporites sp. Brochotriletes sp. The main differences are the presence of Cymbosporites, Apiculiretusispora and Anapiculatisporites, and a lack of Lophozonotriletes in the Chinese assemblage. The upper assemblage (Pridoli) differs from the middle assemblage by the appearance of Apiculiretusispora, Chelinospora and the abundance of Emphanisporites. In comparison with the present assemblage, the common and similar taxa include Retusotriletes cf. warringtonii, Retuso-
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triletes minor, Retusotriletes cf. dubius, Archaeozonotriletes sp., Synorisporites sp., Brochotriletes sp., Cymbosporites sp., Apiculiretusispora sp. the main differences are the abundance of Cymbosporites in our assemblage and the appearance of Anapiculatisporites with rare Emphanisporites, Chelinospora, and the absence of Lophozonotriletes. 7.3. Cornwallis Island, Canadian Arctic McGregor and Narbonne (1978) reported Late Ludlow trilete spores from the Read Bay Formation of Cornwallis Island, Canadian Arctic. There are 12 apparently distinct types of trilete spores, including Punctatisporites sp., Retusotriletes sp., Retusotriletes chartulatus, Apiculiretusispora spicula, Apiculiretusispora sp., cf. Synorisporites verrucatus, ?Emphanisporites protophanus, etc. The main spore morphologies found in Arctic Canada also appear in the Jiangsu assemblage. 7.4. Northwest Spain Cramer (1966a,b) published an account of the palynomorphs of the San Pedro Formation in Northwest Spain, the age of the San Pedro Formation is Ludlow to ?Lower Gedinnian. Similar spores include Archaeozonotriletes, Amicosporites, Cymbosporites, Apiculiretusispora and Anapiculatisporites (based on Richardson and Ioannides, 1973). This assemblage is considerably less diversified than the Jiangsu assemblage.
8. Discussion on palaeobotanical significance ‘‘The origin of the embryophytes (bryophytes+ vascular plants) is shrouded in controversy, and represents one of the greatest palaeontological mysteries. The timing of the origin, subsequent development and distribution of land vascular floras are also matters of much debate’’ ( Richardson, 1996, p. 555; Richardson, 1992). From Ludlow to Pridoli, the land vascular plants were dominated by Cooksonia and had a wide palaeogeographical distribution ( Edwards, 1979;
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Edwards and Rogerson, 1979; Fanning et al., 1990; Fanning et al., 1991; Banks, 1973 etc.). However, the land plants from the Yea region of Victoria, Australia, were dominated by Baragwanathia ( Tims and Chambers, 1984); Cooksonia has not been found from the Balkhash Lake region of Kazakhstan (Senkevitsch, 1978, 1986) and the Juggar Basin of northern Xinjiang, China (Cai et al., 1993). Palynological research is making a major contribution to the understanding of early land floras both by providing a time framework in which to place evolutionary events and by the clues palynomorphs provide to the possibility of the early land plants. Trilete spores of Ludlow and Pridoli could provide much information at the time of establishment and early diversification of land plants. The study of in situ spores is most important to establish a line between the dispersed spores and the macrofossil plants. Fanning et al. (1991) and Edwards and Richardson (1996) systematically reviewed in situ spores in early land plants. During the Ludlow to Pridoli, the types of in situ spores include Retusotriletes (Retusotriletes coronadus, Retusotriletes sp.), Apiculiretusispora, Ambitisporites, Streelispora–Aneurospora, Synorisporites (Synorisporites verrucatus, Synorisporites tripapillatus), Laevolancis (A.? cf. divellomedium). Although the types of in situ spores show less variety than those of dispersed spores, all types of in situ spores appear in the assemblage of dispersed spores. So, it is possible to consider that the dispersed spores partly represent the early diversification of land plants. Except in northern Xinjiang, the macrofossil plants of the Ludlow–Pridoli age have not been found in China. However, the dispersed spores have been reported from the Late Pridoli (Gao, 1981; Fang et al., 1994). This paper reports on the Late Ludlow–Early Pridoli spore assemblage from northern Jiangsu, China. Retusotriletes, Apiculiretusispora, Synorisporites and Archaeozonotriletes similar to in situ spores are also found in the present assemblage. Based on in situ spore studies and comparison with dispersed spores, it is possible to consider that the early land plants existed during Late Ludlow–Early Pridoli in northern Jiangsu, China.
Acknowledgements The authors are grateful to Professors Jiayu Rong, Chenyuan Wang and Lianyu Geng for their helpful suggestions and supporting the valuable information, to Drs Yuping Qi and Youhua Zhu for providing the samples, and to Professors J.B. Richardson and M. Streel for advice and correction of the English. This paper was supported by the National Natural Science Foundation of China (Grant Nos. 49972008 and 49972007), Academia Sinica, Laboratory of Palaeobiology & Stratigraphy, NIGPAS and the Major State Basic Research Development Program (No. G 20000 77703).
References Banks, H.P., 1973. Occurrence of Cooksonia, the oldest vascular land plant macrofossil in Upper Silurian of New York State. J. Indian Bot. Soc. 50A, 227–235. Burgess, N.D., Richardson, J.B., 1995. Late Wenlock to Early Pridoli cryptospores and miospores from south and southwest Wales, Great Britain. Palaeontographica B 236, 1–44. Cai, C., Dou, Y., Edwards, D., 1993. New observation on a Pridoli plant assemblage from north Xinjiang, Northwest China, with comments on its evolutionary and palaeogeographical significance. Geol. Mag. 130, 115–170. Cramer, F.H., 1966a. Palynomorphs from the Siluro-Devonian boundary in NW Spain. Notas y Comunicaciones del Instituto Geologico y Minero de Espana 85, 71–82. Cramer, G.H., 1966b. Palynology of Silurian and Devonian rocks in Northwest Spain. Boletin del Instituto Geologico y Minero de Espana 77, 223–286. Edwards, D., 1979. A Late Silurian flora from the Lower Old Red Sandstone of south-west Dyfed. Palaeontology 22, 23–52. Edwards, D., Richardson, J.B., 1996. Review of in situ spores in early land plants. In: Jansonius, J., McGregor, D.C. ( Eds.), Palynology: Principles and Applications vol. 1. American Association Stratigraphic Palynologists Foundation, pp. 391–407. Edwards, D., Rogerson, E.C.W., 1979. New records of fertile Rhyniophytina from the late Silurian of Wales. Geol. Mag. 116, 93–98. Fang, Z., Cai, C., Wang, Y., Li, X., Gao, L., Wang, C., Geng, L., Wang, S., Wang, N., Li, D., 1994. New advance in the study of the Silurian–Devonian boundary in Qujing, east Yunnan. J. Strat. 18, 81–90. in Chinese with English abstract Fanning, U., Edwards, D., Richardson, J.B., 1990. Further evidence for diversity in Late Silurian land vegetation. J. Geol. Soc. 147, 725–728.
Y. Wang, J. Li / Review of Palaeobotany and Palynology 111 (2000) 111–125 Fanning, U., Edwards, D., Richardson, J.B., 1991a. A new rhyniophytoid from the Late Silurian of the Welsh Borderland. N. Jb. Geol. Palaeont. Abh. 183, 37–47. Fanning, U., Richardson, J.B., Edwards, D., 1991b. A review of in situ spores in Silurian land plants. In: Blackmore, S., Barnes, S.H. ( Eds.), Pollen and Spores Patterns of Diversification. Systematic Association Sp. Vol. 44, 25–47. Gao, L., 1981. Devonian spore assemblages of China. Rev. Palaebot. Palynol. 34, 11–23. Geng, L., Qian, Z., Ding, L., Wang, Y., Wang, G., Cai, X., 1997. Silurian Chitinozoans from Yangtze region. Palaeoworld 8, 1–152. Geng, L., Wang, Y., Zhang, Y., Cai, X., Qian, Z., Ding, L., Wang, G., Liu, C., 1999. Discovery of post-Llandovery chitinozoans in the Yangtze region and their significance. Acta Micropalaeontol. Sinica 16, 111–151. McGregor, D.C., Narbonne, G.M., 1978. Upper Silurian trilete spores and other microfossils from the Read Bay Formation, Cornwallis Island, Canadian Arctic. Can. J. Earth Sci. 15, 1292–1303. Richardson, J.B., 1965. Middle Old Red Sandstone spore assemblages from the Orcadian Basin, northeast Scotland. Palaeontology 7, 559–605. Richardson, J.B., 1992. Origin and evolution of the earliest land plants. In: Schopf, J.W. ( Ed.), Major Event in the History of Life vol. 2. Boston, USA, p., 118. Richardson, J.B., 1996. Lower and Middle Palaeozoic records of terrestrial palynomorphs. In: Jansonius, J., McGregor,
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D.C. (Eds.), Palynology: Principles and Applications vol. 2. American Association of Stratigraphic Palynologists Foundation, pp. 555–574. Richardson, J.B., Ioannides, N.S., 1973. Silurian palynomorphs from the Tanezzuft and Acacus formations, Tripolitania, North Africa. Micropaleontology 19, 257–307. Richardson, J.B., Lister, T.R., 1969. Upper Silurian and Lower Devonian spore assemblages from the Welsh Borderland and South Wales. Palaeontology 12, 201–252. Richardson, J.B., McGregor, D.C., 1986. Silurian and Devonian spore zones of the Old Red Sandstone continent and adjacent regions. Geol. Surv. Can. Bull. 364, 1–79. Schweineberg, J., 1987. Silurian Chitinozoen aus der Provinz Palencia ( Kantabrisches Gebirge, N, Spanien). Gottinger Arb. Geol. Palaeont. 33, 1–94. Senkevitsch, M.A., 1978. New Devonian psilophytes from Kazakhstan. Eshlg. Vses. Palaeont. Obschetva 33, 288–297. in Russian Senkevitsch, M.A., 1986. Fossil plants (in Russian). In: Nikitin, I.F., Bandaletov, S.M. ( Eds.), The Tokrau Horizon of the Upper Silurian: Balkhash Segment. Alma-Ata, Nauka Kazakhstan SSR, pp. 139–141. in Russian Tims, J.D., Chamber, T.C., 1984. Rhyniophytina and Trimerophytina from the early land floras of Victoria Australia. Palaeontology 27, 265–279. Wang, Y., Ouyang, S., 1997. Early Silurian spores from Fenggang, China and their paleobotanical significance. Acta Palaeontol. Sin. 36, 217–237. in Chinese with English summary.
Late Silurian trilete spores from northern Jiangsu, China Y. Wang *, J. Li Nanjing institute of Geology & Palaeontology, Academia Sinica, Nanjing 210008, People’s Republic of China Received 6 July 1999; accepted for publication 8 March 2000
Abstract The Late Silurian is generally considered to a particular significant key period in the study of early land vascular plants. A trilete spore assemblage of the Upper Silurian is described from northern Jiangsu, China. This assemblage comprises 11 genera and 20 species of trilete spores (including laevigate, apiculate, perinotrilite, patinate, rarely distally murornate and equatorially crassitate, and three indeterminate trilete miospores forms). It has similarities to those described from coeval assemblages from around the world (e.g., England and South Wales; Tripolitania, Libya; Cornwallis Island, Canadian Arctic; Northwest Spain). The rare cryptospore, only one specimen (Tetrahedraletes sp.) had been found to be associated with the Chinese trilete spore assemblage. The discovery of the trilete spores from Late Silurian rocks indicates the existence of early land plants, some possibly vascular, at that time in northern Jiangsu, China. © 2000 Elsevier Science B.V. All rights reserved. Keywords: China; Late Silurian; northern Jiangsu; trilete spores
1. Introduction The Late Silurian is generally considered to a particularly significant period in the study of early land vascular plants. Some important fossil plants have been found and studied, such as Cooksonia, Barawanagthia etc. However, the Ordovician and Silurian land plant record is either rare to nonexistent or is poorly preserved. The presence in the fossil record of the trilete spores is thought to be an important in the study of early land vascular plants. Upper Silurian trilete spores have been reported from several localities (Richardson and Lister, 1969; Richardson and Ioannides, 1973; McGregor and Narbonne, 1978; Richardson and McGregor, 1986; Cramer, 1966a,b). Richardson and Lister * Corresponding author. Fax: +86-25-3357026. E-mail address: [email protected] ( Y. Wang)
(1969) described the spore assemblages of the Upper Silurian from the Welsh Borders and South Wales; Richardson and Ioannides (1973) published a study on Upper Silurian ( Upper Wenlock to Pridoli) palynomorphs from Tanezzuft and Acacus Formations, Tripolitania, North Africa; McGregor and Narbonne (1978) studied Upper Silurian trilete spores from Read Bay Formation, Cornwallis Island, Canadian Arctic; Cramer (1966a, b) described the Upper Silurian trilete spores from northwest Spain. Richardson and McGregor (1986) summarized the Silurian spore zones of the Old Red Sandstone continent and adjacent areas, and three spore assemblage zones were established in the Upper Silurian. Data on the well-dated beds of the Late Silurian from China is scarce. Late Silurian trilete spores have been reported from Yunnan ( Fang et al., 1994; Gao, 1981) and Xinjiang (Gao, 1981; Cai et al., 1993). Both reports list taxa but with neither
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descriptions nor illustrations. The present paper reports the discovery of Late Silurian (Late Ludlow–Early Pridoli) trilete spores from a borehole in northern Jiangsu and describes 20 taxa with illustrations.
2. Locality and geological setting The material is from borehole Nc-2 situated 17.5 km south of Dafeng County, northern Jiangsu, China (Fig. 1). Samples (numbers: Nc2-4, Nc-2-5, Nc-2-6) collected from between 2539 and 2542 m are composed of greyish mudstone intercalated with silty mudstones and argillaceous siltstones, yield trilete spores, acritarchs, chitinozoans, scolecodonts, tubular structures and ‘plant’derived cuticles (Fig. 2). Geng et al. (1997, 1999) published results of chitinozoans from Borehole Nc-2. Eisenackitina rimosa, element of Angochitina sinica Biozone, occur in 2542.2 m down in Borehole Nc-2. Fungochitinia kosovensis, Grahnichitina lagenomorpha, as the main elements of F. kosovensis Biozone, occurs 2519.6 m down in Borehole Nc-2. The A. sinica Biozone is correlated approximately with the formosus graptolite Biozone and thought to be
Late Ludlow in age (Geng et al., 1997; Schweineberg, 1987). The F. kosovensis Biozone occurs in the Prague Basin with graptolites of the parultimus–ultimus Biozone and is dated at Early Pridoli. The 2539–2542 m part of Borehole Nc-2 is hence Late Ludlow–Early Pridoli in age. The occurrence of acritarchs, chitinozoans and scolecodonts suggests a marine environment of the strata in question. However, the low-diversity composition of the acritarchs, mainly Leiosphaerids and Dactilofusids, and the association of tubular structures and ‘plant’-derived cuticles from the clastic rocks favour the conclusion that the sporebearing strata are of littoral facies with rich terrigenous deposition.
3. Sampling, techniques The rock samples are greyish mudstones. Trilete spores were extracted using standard HCl–HF– HCl acid maceration techniques twice. The organic residue was sieved using a 10 mm mesh. For microscopic observation, materials were mounted on glass coverslips and the coverslips attached to glass slides using ‘Elvacite’ plastic mounting medium. Photomicrographs were taken on FP3 film using a Zeiss photomicroscope III. All slides are stored in the Nanjing Institute of Geology and Palaeontology, Academia Sinica.
4. Systematic palaeontology Genera and species described below are considered as form genera and species based purely on arbitrary morphological criteria. Anteturma Sporites H. Potonie´, 1893 Turma Triletes Reinsch, 1891 Subturma Azonotriletes Luber, 1935 Infraturma Laevigati Bennie and Kidston, emend. Potonie´ and Kremp, 1954. Fig. 1. Index map of the location.
Genus RETUSOTRILETES Naumova, emend Richardson, 1965 (not Streel, 1964)
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Fig. 2. Stratigraphic column of Nc-2 borehole and distribution of the trilete spores and chitinozoans.
Type species: Retusotriletes pychovii Naumova 1953 ( lectotype species of Richardson, 1965) Retusotriletes cf. warringtonii Richardson and Lister, 1969 (Plate I, 2 and 3) Figured specimens: Plate I, 2 and 3. Depth of core: 2539–2542 m, Upper Ludlow– Lower Pridoli. Description: Amb subtriangular with convex sides and rounded apices; suturae sinuous, nearly equal spore radius, accompanied by lips, ca. 0.5–1.0 mm high; curvaturae perfect present, coincide with the
equator; exine, ca. 1.0–2.0 mm in thickness; secondary folds common. Dimensions: 25–35m, six specimens measured. Comparison: The specimens are similar to that of Retusotriletes cf. warringtonii described by Richardson and Ioannides (1973, p. 272, plate 1, figs. 9–11) in size and features; and larger in size than that of R. warringtonii [22–32 mm, given by Richardson and Lister (1969)]. Retusotriletes cf. dubius (Eisenack) Richardson, 1965 (Plate I, 4)
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PLATE I
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Figured specimen: Plate I, 4. Depth of core: 2539–2542 m, Upper Ludlow– Lower Pridoli. Description: Amb subtriangular with convex sides and rounded apices; suturae straight or slightly sinuous, slightly gaping, ca. 2/3–3/4 of radius in length; curvaturae perfectae present. A triangular, slightly darkened, contact area appears, extending ca. 2/3 to 3/4 of the radius. Exine, ca. 2.5–4.0 mm in thickness, slight by thicker interradially. Dimensions: 30–36 mm, four specimens measured. Comparison: Retusotriletes dubius Richardson, 1965, has a larger size range [56–110 mm, Richardson (1965); 56–64 mm, Richardson and Lister (1969)]. The present specimens are similar to that of R. cf. dubius described by Richardson and Ioannides (1973, p. 272, plate 1, figs. 12–13) in size, however, exine of the present specimens is thicker than those of Richardson and Ioannides (1973, 272, Plate 1, 12–13).
Depth of core: 2539–2542 m. Upper Ludlow– Lower Pridoli. Description: Amb subtriangular with convex sides and rounded apices; suturae 3/4–4/5 of radius, slightly gaping, accompanied by lips, ca. 1.0 mm high; curvaturae perfectae coincident with the equator; contact areas slightly depressed; exine laevigate, 2.0–2.5 mm in thickness; secondary folds common. Dimension: Only one specimen, 63 mm in diameter. Comparison: Only one specimen show the features of this species. It is similar to those of Retusotriletes sp. B described by Richardson and Ioannides (1973, p. 272, plate 1, figs. 20 and 21) in size (31– 64 mm), however, the specimens of Richardson and Ioannides show that the shape of amb is subcircular to oval.
Retusotriletes cf. minor Kedo, 1963 (Plate I, 5)
Type species: Apiculiretusispora brandtii Streel 1964.
Figured specimen: Plate I, 5. Depth of core: 2539–2542 m. Upper Ludlow– Lower Pridoli. Description: Amb circular; suturae extending 2/3– 5/6 of the radius; curvaturae perfectae present, slightly invaginated at the extremities of the rays; exine laevigate, 0.5–1.2 mm in thickness. Dimensions: 21–26 m, three specimens measured. Comparison: The present specimens differ from the type in having the slightly invaginated at apices of curvaturae.
Apiculiretusispora sp. A (Plate I, 9)
Retusotriletes sp. A (Plate I, 1) Figured specimen: Plate I, 1.
Infraturma Apiculati Bennie and Kidston, emend. Potonie´, 1956. Genus APICULIRETUSISPORA Streel, 1964
Figured specimen: Plate I, 9. Depth of core: 2539–2542 m, Upper Ludlow– Lower Pridoli. Description: Amb triangular with convex sides and rounded apices; suturae sinuous, equal spore radius, accompanied by lips, ca. 0.8–1.2 mm high; curvaturae perfectae coincident with the equator; exine distally covered by short spines, 0.5–1.5 mm high, 1.0–1.5 mm in basal diameter, elements closely packed. Dimension: 24–27 mm, three specimens measured. Comparison: The specimens are similar to that of
PLATE I Sample numbers are indicated. Magnification ×1000. 1 Retusotriletes sp. A. Nc-2-4-1. 2 and 3 Retusotriletes cf. warringtonii Richardson et Lister. Nc-2-4-3, Nc-2-4-5. 4 Retusotriletes cf. dubius ( Eisenack) Richardson. Nc-2-4-2. 5 Retusotriletes cf. minor Kedo. Nc-2-4-1. 6 cf. Perotrilites sp. Nc-2-4-3. 7 and 8 Anapiculatisporites sp. Nc-2-4-6. 9 Apiculiretusispora sp. A. Nc-2-4-1. 10 Brochotriletes sp. Nc-2-4-5. 11–15 Apiculiretusispora sp. B. Nc-2-4-2, Nc-2-4-4, Nc-2-4-5, Nc-2-4-6, Nc-2-4-1.
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PLATE II
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Apiculiretusispora. sp. A Richardson and Lister (1969, p. 221, plate 38, fig. 7) in amb, size; however, the present specimens have shorter spines and weaker lips. Comparison to Apiculiretusispora synorea, the latter is characterized by a circular to subcircular amb and without prominent lips. Apiculiretusispora sp. B (Plate I, 11–15) Figured specimens: Plate I, 11–15. Depth of core: 2539 m, Upper Ludlow–Lower Pridoli. Description: Amb circular to subcircular; suturae straight or slightly sinuous, in some cases gaping, and accompanied with lips, ca. 0.5–2.0 mm in width, extending for 3/4–8/9 of spore radius; contact areas laevigate, delimited by curvaturae perfect; exine well defined, ca. 1.0 mm in thickness, outside the contact region sculptured with grana, 1.0–2.0 mm in height, 0.5–1.0 mm in basal diameter, closely packed, ca. 0.5–1.5 mm apart. Dimensions: 34–50 mm, 14 specimens measured. Comparison: These specimens are closely similar to those of Apiculiretusispora sp. C of Richardson and Lister (1969, p. 222, plate 38, fig. 9); however, the exine of latter is covered by minute closely packed sculptural element, ca. 0.5 mm or less. Based on the closely packed grana covered on the exine, the present specimens are different with other species of Apiculiretusispora. Genus ANAPICULATISPORITES Potoni and Kremp, 1954 Type species: Anapiculatisporites isselburgensis Potoni and Kremp, 1954.
Anapiculatisporites sp. (Plate I, 7 and 8) Figured specimens: Plate I, 7 and 8. Depth of core: 2539–2542 m, Upper Ludlow– Lower Pridoli. Description: Amb oval-circular; suturae straight, accompanied by lips, ca. 1.0 mm in width, equal to the spore radius; exine, ca. 0.5–1.0 mm in thickness; distal sculpture with sparse coni, ca. 2–8 mm apart, with circular base ca. 1.0–2.0 mm in diameter, <1 mm high, with sharp tips. Dimension: 23–36 mm, five specimens measured. Comparison: These specimens are closely similar to those of Anapiculatisporites abrepunius Cramer, 1966 (p. 260, plate II, fig. 47), except that they have a sparsely packed sculpture. Infraturma Murornati Potoni and Kremp, 1954 Genus BROCHOTRILETES Naumova, 1953
Naumova
ex
Type species: Brochotriletes foveolatus Naumova 1953 Brochotriletes sp. (Plate I, 10) Figured specimen: Plate I, 10. Depth of core: 2539–2542 m, Upper Ludlow– Lower Pridoli. Description: Amb subtriangular to subcircular; suturae slightly sinuous, accompanied by lips, ca. 1.0 mm in width, extending about entire spore radius; exine thin, 1.0 mm in thickness, sculptured with foveae, 1–2 in diameter, and with narrow, straight, sinuous or meandering ‘channels’. 0.5– 2.0 mm wide and of varying length.
PLATE II Sample numbers are indicated. Magnification ×1000. 1 and 2 Cymbosporites cf. verrucosus Richardson et Lister. Nc-2-4-3. 3–6 Cymbosporites sparseus Y. Wang et J. Li sp. nov. Nc-2-4-3, Nc-2-4-5, Nc-2-4-6. 7 Archaeozonotriletes? sp. Nc-2-4-5. 8 ? Amicosporites sp. Nc-2-4-4. 9 Chelinospora? sp. Nc-2-4-3. 10 Emphanisporites sp. Nc-2-4-3. 11 and 12 Synorisporites sp. Nc-2-4-1. 13 and 14 Cymbosporites sp. Nc-2-4-1, Nc-2-4-3. 15 Type A. Nc-2-4-6. 16 and 17 Type B. Nc-2-4-2. 18 Type C. Nc-2-4-3.
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Dimensions: Only one specimen, 26 mm in diameter. Comparison: Based on amb, suturae, size and sculpture, this specimen is very similar to that of cf. Brochotriletes sp. A of Richardson and Ioannides (1973, pp. 276, 277, plate 4, figs. 5, 6, 8–10), however, curvaturae are present in the African specimens, but not observed here. Genus EMPHANISPORITES McGregor 1961 Type species: Emphanisporites rotatus McGregor 1961. Emphanisporites sp. (Plate II, 10) Figured specimen: Plate II, 10. Depth of core: 2539.00 m, Upper Ludlow–Lower Pridoli. Description: Amb circular; suturae straight, ca. 3/4 of the spore radius, associated with lips, ca. 1– 2 mm, wide; ribs poorly disposed at the equator on proximal face, oriented in an essentially radial fashion, 1–1.5 mm apart, length of ribs ca. 4–6 mm, width ca. 0.5–1 mm; ribs straight or slightly sinuous, with the round end; exine 1.5–2 mm in thickness. distally packed coni/grain, 1–1.5 mm width at the base, and ca. 1 mm high. Dimension: 35 mm, only one specimen. Comparison: Emphanisporites protophanus Richardson and Ioannides (1973, p. 274, plate 2, figs. 8–12, 14 and 15) is similar but is distally laevigate. Subturma Perinotriliti Erdtman 1947. Genus PEROTRILITES ( Erdtman) Couper 1953 Type species: Perotrilites granulatus Couper 1953. Cf. Perotrilites sp. (Plate I, 6) Figured specimen: Plate I, 7. Depth of core: 2539–2542 m. Upper Ludlow– Lower Pridoli. Description: Amb subtriangular with convex sides and rounded apices; suturae slightly sinuous, ca. 4/5 of radius, accompanied by with lips, ca. 0.5– 1.0 mm high; spore two-layered outer layer (‘perine’) thin, diaphanous, exine 2.5–3.5 m in thickness, thinner in the interradial areas, outer separated layer formed the ‘perine’; ‘perine’ smooth, thickness varying from 1–2 to 3–4 mm.
Dimension: 28–35 mm, five specimens measured. Comparison: In the thick exine and the outer separated layer (‘perine’), these specimens are placed in the genus Perotrilites. However, the ‘perine’ of these specimens are smooth and not very clear. Subturma Zonotriletes Waltz, 1935. Infraturma Crassiti Bharadwaj Venkatachala, 1961.
and
Genus AMICOSPORITES Cramer, 1966 Type species: Amicosporites splendidus Cramer, 1966. ?Amicosporites sp. (Plate II, 8) Figured specimen: Plate II, 8. Depth of core: 2539–2542 m, Upper Ludlow– Lower Pridoli. Description: Amb triangular with convex sides and rounded apices; suturae straight, accompanied by lip, ca. 2.0–3.0 mm in width, extending equal the spore radius; exine, ca. 1.0 mm in thickness; at distal side and near equator, a circular ridge, ca. 4.0–5.0 mm in thickness, and ca. 28–30 mm in diameter. Dimensions: Only one specimen, 38 mm. Comparison: Because only one specimen had been found, it is very difficult to show the clear position of the annulate thickening. Based on the general features, this specimen is questioningly placed in the genus Amicosporites. The present specimen differs from A. splendidus Cramer, 1966 (p. 258, plate 11, figs. 31, 40 and 41) by the thicker lip and the circular ridge close equator. Genus SYNORISPORITES Lister, 1969
Richardson
Type species: Synorisporites Richardson and Lister, 1969.
and
downtonensis
Synorisporites sp. (Plate II, 11 and 12) Figured specimen: Plate II, 11 and 12. Depth of core: 2539–2542 m, Upper Ludlow– Lower Pridoli. Description: Amb subtriangular with convex sides and rounded apices; suturae distinct, slightly sinuous, accompanied by low lips, ca. 1.0 mm wide,
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extending equal or near equal to spore radius; curvaturae prefect coincided with equator; equatorially and distally covered with small verrucae; elements rounded in plan. and with flat and pointed apices in profile, ca. 1.0–3.0 mm in basal diameter, 0.5–1.5 mm high, and ca. 0.5–3.0 mm apart. Dimension: 33–36 mm, three specimens measured. Comparison: The present spores differ from Synorisporites sp. A of Richardson and Lister (1969, p. 234, plate 41, figs. 1 and 2) in the shape of amb and some verrucae with pointed apices. Infraturma Patinati Butterworth and Williams 1958.
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tally and equatorially, ca. 3–5 mm in thickness; distal and equatorial ornamentation consisting dominantly of verrucae, 1.2–2.5 mm high, ca. 2.0– 3.0 mm in the basal diameter; in profile elements varying from rounded verrucae to curved apices; in plan, subcircular in shape. Dimension: 20–25 mm, four specimens measured. Comparison: Cymbosporites verrucosus Richardson and Lister, 1969 (p. 241, plate 42, figs. 6–8) has a larger size range (29–52 mm). Cymbosporites sparseus Y. Wang and J. Li sp. nov. (Plate II, 3–6)
Figured specimen: Plate II, 7. Depth of core: 2539 m, Upper Ludlow–Lower Pridoli. Description: Amb triangular with convex sides and rounded apices; suturae, simple, straight, extending ca. 2/3–3/4 of equator spore radius; proximal area with collapsed surface; exine over contact areas thin, and thickest at equator and distal pole; exine at the equator and distal pole, 5–7 mm thick, often faintly corroded near the equator. Dimension: 27–33 mm, four specimens measured. Comparison: The present specimens are corroded near equator, it is possible that the specimens were originally sculptured. So, these specimens are questionably placed in the genus Archaeozonotriletes.
Figured specimens: Plate II, 3–6. Depth of core: 2539–2542 m, Upper Ludlow– Lower Pridoli. Holotype specimen: Plate II, 3 and 4. Description: Amb triangular; suturae straight, ca. 1/2–2/3 of the spore radius; proximal polar region covered by a very thin diaphanous membrane, which is frequently collapsed or completely absent; outline of inner contact area coincides with that of the spore; outside the contact areas, exine 4– 5 mm in thickness; coni confined to the equatorial and distal areas; in profile dominantly biform, based broad sharply tapered, with spine apices, or sometimes with flat, or rounded, apices, width of bases 2.0–3.0 mm, ca. 1.0–3.0 mm high; in plan, bases and apices rounded; sculpture elements sparsely distributed, ca. 3.0–8.0 mm apart (usually ca. 4.0–6.0 mm). Dimension: 25–32 mm, mode 27 mm, eight specimens measured. Comparison: The sparsely distributing coni and small size distinguish this from other species of Cymbosporites.
Genus CYMBOSPORITES Allen 1965
Cymbosporites sp. (Plate II, 13 and 14)
Type species: Cymbosporites cyathus Allen 1956.
Figured specimens: Plate II, 13 and 14. Depth of core: 2539 m, Upper Ludlow–Lower Pridoli. Description: Amb subcircular to circular; suturae slightly sinuous, extending 2/3–3/4 of the spore radius, accompanied with lips, ca. 1.0 mm in width; exine homogeneous, ca. 2–4 mm in thickness, except the central area of proximal surface; central area subcircular to circular, 3/4–4/5 of the spore radius, in some cases, with fine grana, ca. 0.5 mm in diameter.
Genus ARCHAEOZONOTRILETES Naumova, emend. Allen, 1965 Type species: Archaeozonotriletes (Naumova) Allen 1965.
variabilis
Archaeozonotriletes? sp. (Plate II, 7)
Cymbosporites cf. verrucosus Richardson et Lister, 1969 (Plate II, 1 and 2) Figured specimens: Plate II, 1 and 2. Depth of core: 2539 m, Upper Ludlow–Lower Pridoli. Description: Amb circular; suturae usually indistinct, thin, simple, ca. 1/2 of the spore radius; proximal region covered by a thin diaphanous membrane, frequently collapsed; exine thick dis-
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Dimensions: 38–48, 10 specimens measured. Comparison: Based on the feature of the thickness exine and with fine grana, these specimens are placed in the genus Cymbosporites. Genus CHELINOSPORA Allen 1965 Type species: Chelinospora concinna Allen 1965. Chelinospora? sp. (Plate II, 9) Figured specimen: Plate II, 9. Depth of core: 2539 m, Upper Ludlow–Lower Pridoli. Description: Amb subtriangular with convex sides and rounded apices; suturae simple, straight, extending to the inner margin of zone; proximal surface smooth; equatorial thickening, ca. 4.0– 6.0 mm wide; distal surface sparsely covered with muri, forming the irregular reticulum; muri membranous, ca. 1.0–2.5 mm width; lumina, polygonal in shape, ca. 1.5–3 mm in diameter. Dimension: Only one specimen, 30 mm. Comparison: The present specimen is questionably placed in the genus Chelinospora based on the thickness of exine and muri.
elements circular to subcircular in plan, rounded to pointed in profile, ca. 0.8–2.0 mm in width, 0.5– 1.2 mm high, 0.5–2.0 mm apart. Dimensions: 42 mm, only one specimen. Remark: The sculpture is poorly preserved. Type C (Plate II, 18) Figured specimens: Plate II, 18. Depth of core: 2539 m, Upper Ludlow–Lower Pridoli. Description: Amb circular; suturae, straight or slightly sinuous, sometime gaping, extending ca. 3/4–4/5 of equator spore radius; exine over contact areas thin, and thickness at equator and distal pole; exine at the equator and distal pole, ca. 3– 6 mm in thickness; exine at equator slightly thick at the extremities of the rays, ca. 5–6 mm in thickness, and ca. 3–4 mm in the interradial regions; the distal exine with muri; the muri? forming an irregular reticulum. Dimension: 47 mm, only one specimen. Remark: The distribution of muri at the distal is indistinct. If it is true that the muri form the reticulum at the distal, this specimen would belong to genus Chelinospora.
Indeterminate trilete miospores Type A (Plate II, 15) Figured specimen: Plate II, 15. Depth of core: 2539 m, Upper Ludlow–Lower Pridoli. Description: Amb circular; suturae straight, ca. 2/3 of the spore radius; one thickness band along the equator, ca. 3 mm thickness; distal exine densely covered with muri? or coni?; sometimes, muri? appear to form a reticulum; lumina, circular in shape, ca. 1–1.5 mm in diameter; muri? or coni?, ca. 1.5–2.0 mm in 1.0–1.5 mm high. Dimension: 36 mm, only one specimen. Remark: This specimen is poorly preserved. It is very difficult to decide the type of the sculpture elements. Type B (Plate II, 16 and 17) Figured specimens: Plate II, 16 and 17. Depth of core: 2539–2542 m, Upper Ludlow–Lower Pridoli. Description: Amb circular to subtriangular with convex sides and rounded apices; exine at equator? and distally, covered with small coni? or grana?;
5. Composition of the assemblage This spore assemblage consists of 11 genera and 20 species (including three indeterminate types). All trilete spores are recovered from Nc2 core ‘Fentou’ Formation (depth: 2539–2542.9 m). The relative abundance of the trilete spores is shown in Fig. 3. The trilete spores include abundant laevigate spores, apiculate spores, perinotrilite spores, patinate spores, and rarely distally murornate, and equatorially crassitate spores. Laevigate spores comprise only one genus: Retusotriletes, and are ca. 18% of the total spore content. Among these species, Retusotriletes cf. warringtonii is ca. 8%, Retusotriletes cf. dubius, 5% and Retusotriletes cf. minor, 4%. Apiculate spores comprise two genera: Apiculiretusispora and Anapiculatisporites, and make up 30% of the total spore content. The important member is Apiculiretusispora sp. B (19%).
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Fig. 3. Relative abundance of spore taxa.
Perinotrilite spores (cf. Perotrilites sp.), comprise ca. 7% of the total spore content. Patinate spores consist of three genera: Cymbosporites (29%), Archaeozonotriletes? (5%) and Chelinospora? (1%), and comprise of 35% of the total spore content. The dominant taxa are Cymbosporites sp. (13%) and C. sparseus (11%). Murornate spores are represented by two genera: Emphanisporites (1%); and Brochotriletes (1%). Two genera of equatorially crassitate spores occur ?Amicosporites and Synorisporites, and make up ca. 5% of the total spore content. Synorisporites sp. is an important distally murornate spore, and constitutes ca. 4% of the total spore content. It must be pointed that this assemblage mainly consists of trilete spores, only one specimen of cryptospore (Tetrahedraletes sp.) was found.
6. Age of the assemblage This assemblage is dated as Late Ludlow–Early Pridoli on the basis of chitinozoans in overlying/underling beds (Geng et al., 1997, 1999).
The biostratigraphical range of the main members of this assemblage is shown in Fig. 4. Apiculiretusispora is an important genus in this assemblage, comprising ca. 23% in the total of spore content. This genus first appears in the Upper Llandovery of China ( Wang and Ouyang, 1997) but has not been reliably reported below the Gorstian elsewhere. The authors use the presence of Apiculiretusispora spp. to indicate a Ludlow age elsewhere. Retusotriletes cf. dubius is found in the Pridoli (Richardson and Ioannides, 1973; Richardson and Lister, 1969). Brochotriletes sp. is very similar to cf. Brochotriletes sp. A of Richardson and Ioannides, which ranges from Late Ludlow to Pridoli (Richardson and Ioannides, 1973). The important feature is that Synorisporites, Cymbosporites, Emphanisporites, and rarely Amicosporites?, Chelinospora?, appear in this assemblage. Based on the above-mentioned data, it is considered that this assemblage is Late Ludlow–Early Pridoli in age. Richardson and McGregor (1986) established two spore zones from Ludlow to Pridoli from the Old Red Sandstone continent and adjacent
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Fig. 4. The geological distribution of the main trilete spores.
regions. The age of the Synorisporites libycus– ?Lophozonotriletes poecilomorphus Assemblage zone is Ludlow, this zone is characterized by first appearance of proximal radial muri on trilete spores (Emphanisporites), distal murornate sculpture (?Lophozonotriletes, cf. Synorisporites downtonensis), beginning of apiculate sculpture on trilete spores (Apiculiretusispora) and appearance of foveolate sculpture (cf. Brochotriletes), etc.(Richardson and McGregor, 1986). The age of the Synorisporites tripapillatus–Apiculiretusispora spicula Assemblage Zone is Pridoli, this zone is described as first appearance of interradial proximal papillae (S. tripapillatus), distally sculptured patinate spores with thin contact areas (Cymbosporites and Chelinospora), etc.(Richardson and McGregor, 1986). The present spore assemblage comprises of the Synorisporites, Cymbosporites, Brochotriletes, Apiculiretusispora and rarely Emphanisporites, Chelinospora, and has the common features of two assemblage zones of Richardson and McGregor (1986). Richardson (1996) studied Lower and Middle Palaeozoic records of terrestrial palynomorphs, and seven phases have been established. Phase 5 was named as the apiculate–retusoid miospore phase, the geological age ranging from Late Ludlow ( Upper Ludfordian) to Lower Pridoli. This phase is characterized by the appearance of retusoid, evenly granulate to apiculate miospores (Apiculiretusispora) and proximally tripapillate and equatorially crassitate miospores. Compared to the
present spore assemblage described in this paper, the main spore morphologic of Phase 5 appear in our assemblage. The present assemblage is regarded as equivalent Phase 5, and, if so, the geological age would be Late Ludlow–Early Pridoli.
7. Comparison with coeval spores around the world Late Ludlow–Early Pridoli trilete spores are reported from a number of localities including England and South Wales, Tripolitania (Libya), Cornwallis Island (Canadian Arctic) and Northwest Spain. 7.1. England and South Wales Richardson and Lister (1969) and Burgess and Richardson (1995) described the trilete spores from Late Wenlock to Early Devonian of England and South Wales. From the Late Wenlockian, only several laevigate forms were recorded, and this spore assemblage is, in general, less diverse that the present assemblage. The Ludlovian horizons yielded more diverse assemblages than those of Late Wenlockian. Some taxa appear in present assemblage, including Synorisporites, Archaeozonotriletes and Apiculiretusispora. Although common or similar elements to the present assemblage are very rare, the general features of the spore structure are closely similar.
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The main differences are that Cymbosporites, Brochotriletes, Emphanisporites and Perotrilites appear in the present assemblage. The Downtonian (Pridoli) assemblage is akin to the present assemblage, with the following common or similar taxa: Retusotriletes cf. warringtonii, Retusotriletes dubius, Retusotriletes cf. minor, Archaeozonotriletes sp. Apiculiretusispora sp. A, Emphanisporites sp., Perotrilites sp., Synorisporites sp., Cymbosporites cf. verrucosus. However, assemblages from England and South Wales contain abundant Synorisporites and Streelispora; whereas the Chinese assemblage has Brochotriletes, Anapiculatisporites and a few Synorisporites. 7.2. Tripolitania, Libya Richardson and Ioannides (1973) described the spores of the Tanezzuft and Acacus Formations from Tripolitania, and three spore assemblages were established. The spore assemblages range from Late Wenlock to Pridoli. The lower assemblage ( late Wenlock) is characterized by laevigate forms with a few sculptured forms (Emphanisporites, Synorisporites). The present assemblage is more diverse than the lower Libyian assemblage. The middle assemblage (Ludlow) consists of laevigate forms and abundant sculptured forms. The interesting event is the appearance of typical Emphanisporites and the relative abundance of verrucate taxa (Lophozonotriletes, Synorisporites) together with foveolate-reticulate types (cf. Brochotriletes). In comparison to the present assemblage, there are some common or similar taxa, including Retusotriletes cf. warringtonii, Retusotriletes minor, Archaeozonotriletes sp., Emphanisporites sp., Synorisporites sp. Brochotriletes sp. The main differences are the presence of Cymbosporites, Apiculiretusispora and Anapiculatisporites, and a lack of Lophozonotriletes in the Chinese assemblage. The upper assemblage (Pridoli) differs from the middle assemblage by the appearance of Apiculiretusispora, Chelinospora and the abundance of Emphanisporites. In comparison with the present assemblage, the common and similar taxa include Retusotriletes cf. warringtonii, Retuso-
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triletes minor, Retusotriletes cf. dubius, Archaeozonotriletes sp., Synorisporites sp., Brochotriletes sp., Cymbosporites sp., Apiculiretusispora sp. the main differences are the abundance of Cymbosporites in our assemblage and the appearance of Anapiculatisporites with rare Emphanisporites, Chelinospora, and the absence of Lophozonotriletes. 7.3. Cornwallis Island, Canadian Arctic McGregor and Narbonne (1978) reported Late Ludlow trilete spores from the Read Bay Formation of Cornwallis Island, Canadian Arctic. There are 12 apparently distinct types of trilete spores, including Punctatisporites sp., Retusotriletes sp., Retusotriletes chartulatus, Apiculiretusispora spicula, Apiculiretusispora sp., cf. Synorisporites verrucatus, ?Emphanisporites protophanus, etc. The main spore morphologies found in Arctic Canada also appear in the Jiangsu assemblage. 7.4. Northwest Spain Cramer (1966a,b) published an account of the palynomorphs of the San Pedro Formation in Northwest Spain, the age of the San Pedro Formation is Ludlow to ?Lower Gedinnian. Similar spores include Archaeozonotriletes, Amicosporites, Cymbosporites, Apiculiretusispora and Anapiculatisporites (based on Richardson and Ioannides, 1973). This assemblage is considerably less diversified than the Jiangsu assemblage.
8. Discussion on palaeobotanical significance ‘‘The origin of the embryophytes (bryophytes+ vascular plants) is shrouded in controversy, and represents one of the greatest palaeontological mysteries. The timing of the origin, subsequent development and distribution of land vascular floras are also matters of much debate’’ ( Richardson, 1996, p. 555; Richardson, 1992). From Ludlow to Pridoli, the land vascular plants were dominated by Cooksonia and had a wide palaeogeographical distribution ( Edwards, 1979;
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Edwards and Rogerson, 1979; Fanning et al., 1990; Fanning et al., 1991; Banks, 1973 etc.). However, the land plants from the Yea region of Victoria, Australia, were dominated by Baragwanathia ( Tims and Chambers, 1984); Cooksonia has not been found from the Balkhash Lake region of Kazakhstan (Senkevitsch, 1978, 1986) and the Juggar Basin of northern Xinjiang, China (Cai et al., 1993). Palynological research is making a major contribution to the understanding of early land floras both by providing a time framework in which to place evolutionary events and by the clues palynomorphs provide to the possibility of the early land plants. Trilete spores of Ludlow and Pridoli could provide much information at the time of establishment and early diversification of land plants. The study of in situ spores is most important to establish a line between the dispersed spores and the macrofossil plants. Fanning et al. (1991) and Edwards and Richardson (1996) systematically reviewed in situ spores in early land plants. During the Ludlow to Pridoli, the types of in situ spores include Retusotriletes (Retusotriletes coronadus, Retusotriletes sp.), Apiculiretusispora, Ambitisporites, Streelispora–Aneurospora, Synorisporites (Synorisporites verrucatus, Synorisporites tripapillatus), Laevolancis (A.? cf. divellomedium). Although the types of in situ spores show less variety than those of dispersed spores, all types of in situ spores appear in the assemblage of dispersed spores. So, it is possible to consider that the dispersed spores partly represent the early diversification of land plants. Except in northern Xinjiang, the macrofossil plants of the Ludlow–Pridoli age have not been found in China. However, the dispersed spores have been reported from the Late Pridoli (Gao, 1981; Fang et al., 1994). This paper reports on the Late Ludlow–Early Pridoli spore assemblage from northern Jiangsu, China. Retusotriletes, Apiculiretusispora, Synorisporites and Archaeozonotriletes similar to in situ spores are also found in the present assemblage. Based on in situ spore studies and comparison with dispersed spores, it is possible to consider that the early land plants existed during Late Ludlow–Early Pridoli in northern Jiangsu, China.
Acknowledgements The authors are grateful to Professors Jiayu Rong, Chenyuan Wang and Lianyu Geng for their helpful suggestions and supporting the valuable information, to Drs Yuping Qi and Youhua Zhu for providing the samples, and to Professors J.B. Richardson and M. Streel for advice and correction of the English. This paper was supported by the National Natural Science Foundation of China (Grant Nos. 49972008 and 49972007), Academia Sinica, Laboratory of Palaeobiology & Stratigraphy, NIGPAS and the Major State Basic Research Development Program (No. G 20000 77703).
References Banks, H.P., 1973. Occurrence of Cooksonia, the oldest vascular land plant macrofossil in Upper Silurian of New York State. J. Indian Bot. Soc. 50A, 227–235. Burgess, N.D., Richardson, J.B., 1995. Late Wenlock to Early Pridoli cryptospores and miospores from south and southwest Wales, Great Britain. Palaeontographica B 236, 1–44. Cai, C., Dou, Y., Edwards, D., 1993. New observation on a Pridoli plant assemblage from north Xinjiang, Northwest China, with comments on its evolutionary and palaeogeographical significance. Geol. Mag. 130, 115–170. Cramer, F.H., 1966a. Palynomorphs from the Siluro-Devonian boundary in NW Spain. Notas y Comunicaciones del Instituto Geologico y Minero de Espana 85, 71–82. Cramer, G.H., 1966b. Palynology of Silurian and Devonian rocks in Northwest Spain. Boletin del Instituto Geologico y Minero de Espana 77, 223–286. Edwards, D., 1979. A Late Silurian flora from the Lower Old Red Sandstone of south-west Dyfed. Palaeontology 22, 23–52. Edwards, D., Richardson, J.B., 1996. Review of in situ spores in early land plants. In: Jansonius, J., McGregor, D.C. ( Eds.), Palynology: Principles and Applications vol. 1. American Association Stratigraphic Palynologists Foundation, pp. 391–407. Edwards, D., Rogerson, E.C.W., 1979. New records of fertile Rhyniophytina from the late Silurian of Wales. Geol. Mag. 116, 93–98. Fang, Z., Cai, C., Wang, Y., Li, X., Gao, L., Wang, C., Geng, L., Wang, S., Wang, N., Li, D., 1994. New advance in the study of the Silurian–Devonian boundary in Qujing, east Yunnan. J. Strat. 18, 81–90. in Chinese with English abstract Fanning, U., Edwards, D., Richardson, J.B., 1990. Further evidence for diversity in Late Silurian land vegetation. J. Geol. Soc. 147, 725–728.
Y. Wang, J. Li / Review of Palaeobotany and Palynology 111 (2000) 111–125 Fanning, U., Edwards, D., Richardson, J.B., 1991a. A new rhyniophytoid from the Late Silurian of the Welsh Borderland. N. Jb. Geol. Palaeont. Abh. 183, 37–47. Fanning, U., Richardson, J.B., Edwards, D., 1991b. A review of in situ spores in Silurian land plants. In: Blackmore, S., Barnes, S.H. ( Eds.), Pollen and Spores Patterns of Diversification. Systematic Association Sp. Vol. 44, 25–47. Gao, L., 1981. Devonian spore assemblages of China. Rev. Palaebot. Palynol. 34, 11–23. Geng, L., Qian, Z., Ding, L., Wang, Y., Wang, G., Cai, X., 1997. Silurian Chitinozoans from Yangtze region. Palaeoworld 8, 1–152. Geng, L., Wang, Y., Zhang, Y., Cai, X., Qian, Z., Ding, L., Wang, G., Liu, C., 1999. Discovery of post-Llandovery chitinozoans in the Yangtze region and their significance. Acta Micropalaeontol. Sinica 16, 111–151. McGregor, D.C., Narbonne, G.M., 1978. Upper Silurian trilete spores and other microfossils from the Read Bay Formation, Cornwallis Island, Canadian Arctic. Can. J. Earth Sci. 15, 1292–1303. Richardson, J.B., 1965. Middle Old Red Sandstone spore assemblages from the Orcadian Basin, northeast Scotland. Palaeontology 7, 559–605. Richardson, J.B., 1992. Origin and evolution of the earliest land plants. In: Schopf, J.W. ( Ed.), Major Event in the History of Life vol. 2. Boston, USA, p., 118. Richardson, J.B., 1996. Lower and Middle Palaeozoic records of terrestrial palynomorphs. In: Jansonius, J., McGregor,
125
D.C. (Eds.), Palynology: Principles and Applications vol. 2. American Association of Stratigraphic Palynologists Foundation, pp. 555–574. Richardson, J.B., Ioannides, N.S., 1973. Silurian palynomorphs from the Tanezzuft and Acacus formations, Tripolitania, North Africa. Micropaleontology 19, 257–307. Richardson, J.B., Lister, T.R., 1969. Upper Silurian and Lower Devonian spore assemblages from the Welsh Borderland and South Wales. Palaeontology 12, 201–252. Richardson, J.B., McGregor, D.C., 1986. Silurian and Devonian spore zones of the Old Red Sandstone continent and adjacent regions. Geol. Surv. Can. Bull. 364, 1–79. Schweineberg, J., 1987. Silurian Chitinozoen aus der Provinz Palencia ( Kantabrisches Gebirge, N, Spanien). Gottinger Arb. Geol. Palaeont. 33, 1–94. Senkevitsch, M.A., 1978. New Devonian psilophytes from Kazakhstan. Eshlg. Vses. Palaeont. Obschetva 33, 288–297. in Russian Senkevitsch, M.A., 1986. Fossil plants (in Russian). In: Nikitin, I.F., Bandaletov, S.M. ( Eds.), The Tokrau Horizon of the Upper Silurian: Balkhash Segment. Alma-Ata, Nauka Kazakhstan SSR, pp. 139–141. in Russian Tims, J.D., Chamber, T.C., 1984. Rhyniophytina and Trimerophytina from the early land floras of Victoria Australia. Palaeontology 27, 265–279. Wang, Y., Ouyang, S., 1997. Early Silurian spores from Fenggang, China and their paleobotanical significance. Acta Palaeontol. Sin. 36, 217–237. in Chinese with English summary.