Clathrocoilona spissa ( Lecompte, 1951 )

Huang, Jiayuan, Liang, Kun, Wang, Yue, Kershaw, Stephen, Jeon, Juwan, Li, Yue & Qie, Wenkun, 2022, Stromatoporoids from a Middle Devonian reef in South China and their palaeoecological implication, Acta Palaeontologica Polonica 67 (3), pp. 711-736 : 718-725

Clathrocoilona spissa ( Lecompte, 1951)

Fig. 6 .

1951 Stromatoporella spissa sp. nov.; Lecompte 1951: 187, pl. 27: 1–4.

1968 Stromatoporella spissa Lecompte,1951 ; Flügel and Flügel-Kahler 1968: 399.

1971 Stromatopora spissa ( Lecompte, 1951) ; Kaźmierczak 1971: 92, pl. 21: 2.

1971 Clathrocoilona spissa ( Lecompte, 1951) ; Zukalová 1971: 56, pl. 15: 1, 2.

1974 Clathrocoilona spissa ( Lecompte, 1951) ; Flügel 1974: 165, pl. 24, 26, 27.

1980 Clathrocoilona spissa ( Lecompte, 1951) ; Mistiaen 1980: 196, pl. 7: 3–9.

1984 Clathrocoilona spissa ( Lecompte, 1951) ; Cockbain 1984: 25, pl. 11: 1–4.

1985 Clathrocoilona spissa ( Lecompte, 1951) ; Mistiaen 1985: 96, pl. 6: 6–8.

1988 Clathrocoilona spissa ( Lecompte, 1951) ; Mistiaen 1988: 174.

1993 Clathrocoilona (Clathrocoilona) solidula spissa ( Lecompte, 1951) ; May 1993: 38, pl. 7: 2; pl. 8: 1, 2.

1999 Clathrocoilona (Clathrocoilona) solidula spissa ( Lecompte, 1951) ; May 1999: 127.

1999 Clathrocoilona spissa ( Lecompte, 1951) ; Cook 1999: 507, text-fig. 28C, 29.

2005 Clathrocoilona (Clathrocoilona) solidula spissa ( Lecompte, 1951) ; May 2005: 180, pl. 13: 2, 3.

2008 Clathrocoilona spissa ( Lecompte, 1951) ; Salerno 2008: 74, pl. 11: 2.

2020 Clathrocoilona spissa (Lecompte) ; Huang et al. 2020: 7, text-fig. 5B; 11, text-fig. 8C, F.

2020 Clathrocoilona crassitexta (Lecompte) ; Huang et al. 2020: 8, text-fig. 6A, G, I, 11, text-fig. 8A, D, F.

2020 Clathrocoilona obliterata (Lecompte) ; Huang et al. 2020: 11, text-fig. 8F.

Material.— 275 specimens from the Givetian (Middle Devonian) Jiwozhai reef, Dushan Formation , Dushan, Guizhou, South China, with two representative specimens ( NIGP 177048 and NIGP 177049 ) illustrated .

Description.—Skeletons are thin laminar in growth form, commonly below 2 mm in thickness, with only a few exceeding 5 or 10 mm, in almost all samples encrusting high-relief organisms, such as tabulate corals (e.g., Thamnopora cf. pansiensis Tchi, 1966 ), solitary rugose corals (e.g., Mictophyllum cf. shawoziense He, 1978 ), or other laminar organisms, such as bryozoans (e.g., Fistuliporella hemispheroidea Yang, 1954 ), and other species of stromatoporoids. Surface features cannot be viewed because the stromatoporoids are enclosed in cemented limestone. Latilaminae are conspicuous, ranging 0.2–6 mm in thickness, mostly within 2 mm. In longitudinal section, the skeletons show distinct skeletal variations ( Fig. 6A ). In some areas, the structures are generally amalgamated, with laminae and pillars being hardly differentiated ( Fig. 6A 2 ). Laminae and pillars are irregularly thick with regard to both their thickness and width; they range, respectively, from 0.2 to 0.4 mm thickness, and spacing is 4–6 per 2 mm. Gallery shapes are variable, round or irregular, with or without abundant dissepiments. In the other areas, skeletons are constructed by regular laminae and pillars ( Fig. 6A 3 ), such as the terminal part of latilaminae ( Fig. 6B 1 ). Laminae are continuous, formed by the lighter axial zone and the coated dark layer, spacing 8–14 per 2 mm, 0.02–0.06 mm in thickness, with frequent single layers in a thickness of 0.2 mm ( Fig. 6A 3 ). Pillars are spool-shaped, confined to the interlaminar spaces, with thinner ones 0.02–0.04 mm in thickness, thicker ones 0.1–0.2 mm in thickness, spacing 8–12 per 2 mm. In tangential section of the regular areas, pillars appear isolated, 0.05–0.1 mm in thickness ( Fig. 6B 2 ). Laminae are occasionally tripartite with conspicuously light axial zone in regular area.

Remarks.—The present species resembles Clathrocoilona crassitexta ( Lecompte, 1951) , C. obliterata ( Lecompte, 1951) , and C. spissa ( Lecompte, 1951) from the Dinant Basin, southern Belgium. Thus, this species was preliminarily assigned to Clathrocoilona crassitexta , C. obliterata and C. spissa , respectively, in Huang et al. (2020) using different samples. However, detailed study reveals intra-specific variations in specimens of the Jiwozhai reef. The irregular areas show close similarity to Clathrocoilona crassitexta because of their densely irregular skeletons, and the regular areas retain a high degree of consistency with C. obliterata in terms of prominent tripartite structure and regular thin laminae and short pillars. Therefore, all these characteristics are present within the same specimens, and this may indicate that Clathrocoilona spissa , C. obliterata , and C. crassitexta are synonymous species with intra-specific variations. Here, we temporarily assign this species to Clathrocoilona spissa due to the dominant irregular skeletons.

Stratigraphic and geographic range.—Lower Givetian Middle Devonian) of Eifel, Germany, and central Bohemia, Czech Republic; lower to middle Givetian (Middle Devonian) of Guangxi and Guizhou provinces, South China, and Queensland, Australia; Givetian to Frasnian (Middle–Upper Devonian) of Avesnois and Boulonnais, France, Dinant Basin, Belgium, Holy Cross Mountains, Poland; lower Frasnian Upper Devonian) of Moravian Karst, Czech Republic; Frasnian (Upper Devonian) of Canning Basin, Australia.

Genus Stictostroma Parks, 1936

Type species. Stictostroma gorriense Stearn, 1995 ; Emsian (Lower Devonian) of Gorrie, Ontario, Canada .

Stictostroma saginatum ( Lecompte, 1951) Fig. 7A, B .

1951 Stromatoporella saginata sp. nov.; Lecompte 1951: 171, pl. 22: 5–7; pl. 23: 1–3.

1968 Clathrocoilona saginata ( Lecompte, 1951) ; Flügel and Flügel-Kahler 1968: 373.

1983 Clathrocoilona cf. saginata ( Lecompte, 1951) ; Stearn 1983: 549, text-fig. 5G–H.

1984 Clathrocoilona saginata ( Lecompte, 1951) ; Cockbain 1984: 25, pl. 10: A–D.

1985 Stictostroma saginatum ( Lecompte, 1951) ; Mistiaen 1985: 115, pl. 8: 6–11.

1988 Stictostroma saginatum ( Lecompte, 1951) ; Mistiaen 1988: 176, pl. 21: 5–9.

1999 Stictostroma saginatum ( Lecompte, 1951) ; Mistiaen 1999: 36, pl. 3: 9–12; pl. 4: 1, 2.

2000 Stictostroma saginatum ( Lecompte, 1951) ; Mistiaen and Gholamalian 2000: 83, pl. 6: 6–8.

2008 Stictostroma saginatum ( Lecompte, 1951) ; Salerno 2008: 82, pl. 12: 2.

2020 Stictostroma saginatum ( Lecompte, 1951) ; Huang et al. 2020: 7, text-fig. 5C.

Material.— 95 specimens from the Givetian (Middle Devonian) Jiwozhai reef, Dushan Formation , Dushan, Guizhou, South China, with two typical specimens ( NIGP 177050 and NIGP 177051 ) illustrated .

Description.—Skeletons are laminar, with common prominent digitation of mamelons forming columns (a maximum of 25 mm in height) ( Figs. 2D , 7A ), occasionally encrusting on solitary rugose corals or branching tabulate corals (e.g., Thamnopora sp. , solitary rugose corals) ( Fig. 7B ). In longitudinal section, the skeleton consists of extensive laminae and restricted pillars. Laminae are extensive, gently undulating but sharply increased around the mamelons, spacing 8–12 per 2 mm and 0.05–0.2 mm in thickness. Pillars are spool-shaped, commonly confined to one interlaminar space, irregularly spacing about 7–10 in 2 mm and 0.05–0.2 mm in thickness. Galleries are circular, oval, or horizontally elongate. Mamelons are protruding, with central astrorhizal canals, generally 2–20 mm in height. In tangential section, individual pillars form round dots, 0.05–0.1 mm in diameter; laminae present as concentric circles. Mamelons are distinct, showing a round central astrorhizal canals, with separated by distances of 2–4 mm ( Fig. 7A 1 ). The microstructures are compact or ordinicellular ( Fig. 7A 3 ).

Remarks.—The skeletal structures of this species are exactly the same as Stromatoporella saginata Lecompte, 1951 , and Stictostroma saginatum described by Mistiaen (1988: 176–179, pl. 21: 8, 9). Although Stictostroma Parks, 1936 , is highly similar to Stromatoporella Nicholson, 1886 , in relation to extensive laminae, confined pillars, and ordinicellular microstructure, the latter genus is characterized by abundant ring pillars. In the absence of ring pillars, the species was assigned to Clathrocoilona Yavorsky, 1931 ( Flügel and Flügel-Kahler 1968; Stearn 1983; Cockbain 1984) or Stictostroma ( Mistiaen 1985, 1988, 1999; Salerno 2008). It closely resembles Clathrocoilona in terms of laterally continuous laminae and confined pillars, but they are different in microstructure. Here, we assign this species to Stictostroma due to the coarsely ordinicellular microstructure.

Stratigraphic and geographic range.—?Emsian (Lower Devonian) of Ellesmere Island, Canada; Givetian (Middle Devonian) of Eifel, Germany and Guizhou Province, South China; lower Frasnian (Upper Devonian) of Central Mountains, Afghanistan; middle Frasnian (Upper Devonian) of Boulonnais and Avesnois, France; upper Frasnian (Upper Devonian) of Dinant and Namur basins, Belgium; Frasnian (Upper Devonian) of Kerman and Esfahan provinces, Iran, and Canning Basin, Australia ( Mistiaen and Gholamalian 2000).

Genus Synthetostroma Lecompte, 1951

Type species: Synthetostroma actinostromoides Lecompte, 1951 ; Givetian (Middle Devonian) of Surice, Belgium .

Synthetostroma actinostromoides Lecompte, 1951 Fig. 7C .

1951 Synthetostroma actinostromoides sp. nov.; Lecompte 1951: 194, pl. 20: 3, 4.

1968 Synthetostroma actinostromoides Lecompte, 1951 ; Flügel and Flügel-Kahler 1968: 18.

1971 Synthetostroma actinostromoides Lecompte, 1951 ; Zukalová 1971: 53, pl. 12: 1–5.

1978 Synthetostroma actinostromoides Lecompte, 1951 ; Huang 1978: 33, pl. 6: 4.

1978 Synthetostroma actinostromoides Lecompte, 1951 ; Wang 1978: 35, pl. 18: 1.

1980 Synthetostroma cf. actinostromoides Lecompte, 1951 ; Mistiaen 1980: 196, pl. 9: 3–6.

1982 Trupetostroma doupenglingense Yang and Dong, 1979 ; Dong and Wang 1982: 14, pl. 5: 7, 8.

1982 Pseudoactinodictyon cf. distanum Yang and Dong, 1979 ; Dong and Wang 1982: 16, pl. 7: 7, 8

1988 Synthetostroma actinostromoides Lecompte, 1951 ; Wang 1988: pl. 15: 1.

1992 Synthetostroma actinostromoides Lecompte, 1951 ; Dong and Song 1992: 29, pl. 2: 3.

1992 Trupetostroma assamptum Yang and Dong, 1979 ; Dong and Liu 1992: 167, pl. 1: 1.

1992 Clathrocoilona cf. variabilis Yang and Dong, 1979 ; Dong and Liu 1992: 169, pl. 3: 4.

1993 Clathrocoilona (Synthetostroma) actinostromoides ( Lecompte, 1951) ; May 1993: 40, pl. 10: 1.

2008 Synthetostroma actinostromoides Lecompte, 1951 ; Salerno 2008: 79, pl. 11: 1.

2020 Synthetostroma actinostromoides Lecompte, 1951 ; Huang et al. 2020: 7, text-fig. 5D.

Material.— Four specimens from the Givetian (Middle Devonian) Jiwozhai reef, Dushan Formation , Dushan, Guizhou, South China, with one specimen ( NIGP 177052 ) illustrated .

Description. —Skeletons are commonly laminar. Among the four specimens, two small ones preserved as fragments, 3–5 mm in thickness. The largest one shows a thickness up to 50 mm ( Fig. 3 ). Latilaminae exist, each latilamina is 2–6 mm thick. In longitudinal section, the skeletons consist of multilamellar laminae and slender pillars ( Fig. 7C 1 ). Laminae are continuous, undulating, integrated by multiple microlaminae and abundant imbricating dissepiments, spacing 5–7 per 2 mm and 0.05–0.2 mm in thickness. Pillars are post-like, confined to interlaminar spaces but systematically superposed, penetrating 3–4 laminae, spacing 7–10 per 2 mm and 0.05–0.15 mm in thickness. The galleries are variable, rectangular to subcircular. Mamelons are conspicuous, with a height of 4–6 mm ( Fig. 7C 1 ). Astrorhizal canals and interlaminar spaces are often pervaded by dissepiments. In tangential section, isolated pillars are rounded or locally irregular in form, in diameter of 0.1–0.2 mm. Laminae show concentric circles around mamelon. Mamelons are 2–3 mm in width, with a distance of 4–8 mm from one to another Fig. 7C 2 ). The microstructure is compact.

Remarks.—The present specimens from Jiwozhai reef share high morphological similarities with the holotype of Synthetostroma actinostromoides Lecompte, 1951 , and show well-preserved mamelons. Although Synthetostroma actinostromoides once was regarded as a junior synonym of Clathrocoilona by Kosareva (1976), the presence of superposed pillars and frequent microlaminae is not matched with the generic concept of Clathrocoilona (laminae thick, tripartite; pillars confined to the interlaminar spaces, not systematically superposed). Trupetostroma doupenglingense Yang and Dong, 1979 , Pseudoactinodictyon cf. distanum Yang and Dong, 1979 , described by Dong and Wang (1982) and Trupetostroma assamptum Yang and Dong, 1979 , Clathrocoilona cf. variabilis Yang and Dong, 1979 , described by Dong and Liu (1992) seem to be similar to the Jiwozhai reef specimens in terms of tripartite laminae and abundant dissepiments, thus further re-evaluation of these species is required.

Stratigraphic and geographic range.—Lower Givetian (Middle Devonian) of Eifel and Sauerland, Germany; middle Givetian (Middle Devonian) of Boulonnais, France; Guizhou, Hunan, and Yunnan provinces, South China, and Dinant Basin, Belgium;?upper Givetian to lower Frasnian (Middle– Late Devonian) of Moravian Karst, Czech Republic.

Order Stromatoporida Stearn, 1980

Family Stromatoporidae Winchell, 1867

Genus Pseudotrupetostroma Khalfina and Yavorsky, 1971

Type species: Stromatopora pellucida artyschtensis Yavorsky, 1955 ; Givetian (Middle Devonian) of Kuznetsk Basin, Russia .

Pseudotrupetostroma porosum ( Yang and Dong, 1979)

Fig. 8A .

1979 Hermatostroma porosum sp. nov.; Yang and Dong 1979: 68, pl. 38: 7, 8.

1980 Hermatostroma parksi Lecompte, 1952 ; Mistiaen 1980: 202: pl. 9: 7–9; pl. 10: 1, 2.

1982 Trupetostroma cellulosum Lecompte, 1952 ; Dong and Wang 1982: 13, pl.5: 1, 2.

1982 Hermatostroma porosum Yang and Dong, 1979 ; Dong and Wang 1982: 22, pl. 13: 1, 2.

1999 Hermatostroma maculatum Yang and Dong, 1979 ; Cook 1999: 511, text-fig. 32A–C; 33A–D.

2008 Pseudotrupetostroma cellulosum ( Lecompte, 1952) ; Salerno 2008: 92, pl. 15: 1–3.

2020 Trupetostroma cf. colliculosum Khalfina, 1960 ; Huang et al. 2020: 6.

Material.— Two specimens from the Givetian (Middle Devonian) Jiwozhai reef, Dushan Formation , Dushan, Guizhou, South China, with one specimen ( NIGP 177053 ) illustrated .

Description.—Skeletons are laminar, up to 50 mm in thickness ( Fig. 3 ). Surface features are not visible in cemented limestone. In longitudinal section the skeleton between astrorhizae forms a regular network ( Fig. 8A 1 ). Pachystromes are laterally continuous, occasionally undulose, spacing 8–12 per 2 mm, and of 0.1 mm in thickness. Pachysteles are vertically extensive, closely spaced, spacing 6–8 per 2 mm, 0.1–0.2 mm in thickness. In the upper part of the mamelons, the skeletons are dominated by continuously thick pachysteles, with 6 per 2 mm, 0.2 mm in thickness. Pachystromes weakly occur ( Fig. 8A 1 ). Galleries are variable in sizes, 0.1–0.3 mm in diameter. Mamelons are conspicuous, horizontally extensive, with a height of 15–20 mm. Astrorhizal canals commonly contain abundant dissepiments. In tangential section, skeletons are densely compact with irregular networks or rare isolated pachysteles. Astrorhizae are predominant, up to 15 mm in diameter, with over 10 branching canals ( Fig. 8A 2 ). The microstructure was mostly affected by the alteration of diagenesis, which possesses coarsely cellular-like structure ( Fig. 8A 3 ).

Remarks.—This species was previously assigned to Trupetostroma cf. colliculosum Khalfina, 1960 , but the specimens from Jiwozhai reef are quite different from Trupetostroma Parks, 1936 , in terms of the atypical regular network of pachystromes and pachysteles. It closely resembles the Pseudotrupetostroma cellulosum ( Lecompte, 1952) documented by Salerno (2008: 93–96, pl. 15: 3) with respect to structures near the mamelons, but the holotype of Trupetostroma cellulosum Lecompte, 1952 , shows apparently confined inter-laminar pillars and different thin laminae.

Stratigraphic and geographic range.—Lower Givetian Middle Devonian) of Eifel, Germany; lower to middle Givetian (Middle Devonian) of Guangxi, Yunnan, and Guizhou provinces, South China, and Queensland, Australia; middle Givetian (Middle Devonian) of Boulonnais, France.

Family Syringostromellidae Stearn, 1980

Genus Salairella Khalfina, 1961

Type species: Salairella multicea Khalfina, 1961 ; Eifelian (Middle Devonian) of Salair, Russia .

Remarks. —Genera of Stromatoporida and Syringostromatida were confused with each other for over 150 years until Stearn (1993) revised Stromatoporida in detail. The dominance of pachysteles was traditionally regarded as the diagnostic feature of the first named stromatoporoid Stromatopora Goldfuss, 1826 (e.g., Nicholson 1886; Galloway 1957; Dong 2001). Also some species belonging to Salairella were erroneously assigned to Stromatopora (e.g., Dong and Song 1992). Stearn (1993) elaborated the relationships between typical Stromatopora and its similar genera. He reaffirmed that presence of cassiculate structure is the key morphological feature of the holotype of Stromatopora from Germany. Therefore, although Salairella closely resembles Stromatopora in having tangentially amalgamated network, they are totally different in morphology of vertical sections of the skeleton.

Salairella buecheliensis ( Bargatzky, 1881)

Fig. 8B .

1881 Caunopora bücheliensis sp. nov.; Bargatzky 1881: 290.

1952 Parallelopora bücheliensis ( Bargatzky, 1881) ; Lecompte 1952: 290, pl. 50: 3, 4.

1968 Caunopora bücheliensis Bargatzky, 1881 ; Flügel and Flügel-Kahler 1968: 53.

1978 Stromatopora hüpschii ( Bargatzky, 1881) ; Wang 1978: 27, pl. 13: 1.

1980 Stromatopora cf. bücheliensis ( Bargatzky, 1881) ; Mistiaen 1980: 210, pl. 13: 7–9; pl. 14: 1–3.

1985 Salairella buecheliensis ( Bargatzky, 1881) ; Mistiaen 1985: 145, pl. 12: 10–12; pl. 13: 1.

1992 Stromatopora hüpschii ( Bargatzky, 1881) ; Dong and Song 1992: 30, pl. 3: 1a, b.

1999 Salairella buecheliensis ( Bargatzky, 1881) ; May 1999: 129, pl. 1: 6.

1999 Salairella buecheliensis ( Bargatzky, 1881) ; Cook 1999: 525, text-fig. 45A–E.

2005 Salairella buecheliensis ( Bargatzky, 1881) ; May 2005: 204, pl. 21: 1, 2; pl. 30: 2, 3; pl. 31: 1; pl. 32: 1.

2008 Salairella buecheliensis ( Bargatzky, 1881) ; Salerno 2005: 97, pl. 14: 2.

2020 Stromatopora huepschii ( Bargatzky, 1881) ; Huang et al. 2020: 7, text-fig. 5F.

Material. — 10 specimens from the Givetian (Middle Devonian) Jiwozhai reef, Dushan Formation , Dushan, Guizhou, South China, with one representative specimen ( NIGP 177054 ) illustrated .

Description.—Skeletons are laminar in growth form, up to 20 mm in thickness and 500 mm in basal dimension ( Fig. 3 ). The longitudinal section is dominated by pachysteles, partly with coarsely amalgamated networks or atypical cassiculate structures. Pachysteles are vertically continuous, commonly joining and dividing in oblique thin section ( Fig. 8B 1 ), spacing 5–8 per 2 mm, 0.1–0.2 mm in thickness. Pachystromes are not clear, oblique or horizontal. Galleries are vertically elongate or occasionally irregular, crossed by flat or oblique dissepiments, at the same width as the pachysteles. Syringoporid symbionts are abundant, with a width of 0.2– 0.3 mm, spacing 2–3 per 2 mm. The tangential section shows a closed network with dominantly circular autotubes between the astrorhizae ( Fig. 8B 2 ). Width of the skeletal elements and autotubes 0.1–0.2 mm. Astrorhizae are conspicuous, generally bifurcated, 0.1–0.25 mm in diameter. Microstructure is normally cellular, 0.02 mm in diameter, but in some cases is melanospheric due to the diagenesis ( Fig. 8B 3 ).

Remarks. —The predominance of vertically elongate pachysteles was also regarded as the main diagnostic characteristics of Stromatopora Goldfuss, 1826 , for many years (e.g., Yang and Dong 1979; Dong 2001). Therefore, the samples in Jiwozhai reef were previously assigned to Stromatopora huepschii ( Bargatzky, 1881) due to the rare existence of inconspicuous cassiculate structure probably caused by intraspecific variation, but the dominance of vertical elongate pachysteles justifies the designation as Salairella buecheliensis .

Stratigraphic and geographic range.—Eifelian to Givetian (Middle Devonian) of Dinant Basin, Belgium; lower Givetian (Middle Devonian) of Eifel, Germany, and Bohemia, Czech Republic; lower to middle Givetian (Middle Devonian) of Boulonnais, France, Queensland, Australia, Central Mountains, Afghanistan, and Hunan and Guizhou provinces, South China.

Order Syringostromatida Bogoyavlenskaya, 1969

Family Coenostromatidae Waagen and Wentzel, 1887

Genus Habrostroma Fagerstrom, 1982

Type species: Stromatopora proxilaminata Fagerstrom, 1961 ; Middle Devonian of Ontario, Canada .

Figures

Fig.6. Stromatoporoid Clathrocoilona spissa (Lecompte, 1951), from the Jiwozhai reef, Jiwozhai Member,Dushan Formation, Givetian, Middle Devonian; Dushan, Guizhou, South China. A. NIGP 177048; A1, longitudinal section showing the contemporarily encrusting layers, with black and white rectangles illustrating details; A2, A3, enlargement of A1, note the obvious discrepancy between different areas in the same stromatoporoid: the condensed skeletons of A2 are similar to Clathrocoilona spissa (Lecompte, 1951) and thin laminae of A3 are consistent with Clathrocoilona obliterata (Lecompte, 1951). B. NIGP 177049; B1, longitudinal section, note the intra-specific variations (white arrows) of the lower irregular layers similar to Clathrocoilona crassitexta (Lecompte, 1951) and the upper regular layers identical to Clathrocoilona obliterata (Lecompte, 1951); B2, tangential section.

Fig. 2. Field photographs of the Jiwozhai reef. A. A panoramic view of the whole reef unit, with a white rectangle indicating the studied area. Note the reverse fault in the east. B. A general view shows the studied area of the reef unit. C. Enlarged field photo of the reef fragment marked in B, showing the thick or thin laminar stromatoporoids (undulating dashed line) covered on branching tabulate corals (triangles), solitary rugose corals (crosses), dendroid stromatoporoids (squares), bulbous stromatoporoid (circled line), and clay-rich micrites (fine grained sediments between the metazoan skeletons). D. An example of polished block of the Jiwozhai reef limestone showing toppled dendroid or laminar Stachyodes fasciculata Dong in Dong et al., 1989, and encrusting Stictostroma saginatum (Lecompte, 1951) in the upper area. Note the conspicuous digitation of mamelons of Stictostroma saginatum (Lecompte, 1951) in the lower right corner. Sti, Stictostroma saginatum (Lecompte, 1951); Sta, Stachyodes fasciculata Dong in Dong et al., 1989; Tha, Thamnopora cf. pansiensis Tchi, 1966.

Fig. 3. Schematic vertical section of stromatoporoids in the Jiwozhai reef (Huang et al. 2020) showing the spatial distribution of different stromatoporoids, note the predominance of the Gerronostromaria grossum Dong, 1974, in the laminar form stromatoporoids.1, Gerronostromaria grossum Dong, 1974; 2, Clathrocoilona spissa (Lecompte, 1951); 3,?Habrostroma laminosum (Lecompte, 1952); 4, Parallelopora sp.; 5, Pseudotrupetostroma porosum (Yang and Dong, 1979); 6, Salairella buecheliensis (Bargatzky, 1881); 7, Stachyodes costulata Lecompte, 1952; 8, Stachyodes fasciculata Dong in Dong et al., 1989; 9, Stachyodes sp.; 10, Stictostroma saginatum (Lecompte, 1951); 11, Synthetostroma actinostromoides Lecompte, 1951. Black, stromatoporoids; gray, other organisms between stromatoporoids.

Fig. 1. Location and stratigraphy of the Jiwozhai reef in Dushan County, Guizhou, South China. A. Map showing southern Guizhou and northern Guangxi and the studied area in China. B. Locality of the Jiwozhai reef in Dushan County. C. Depositional successions and fossil assemblages of the supposed uppermost Eifelian to lowermost Frasnian in Dushan, Guizhou province (modified after Liao et al. 1979; Liao 2003).Abbreviations:Ei, Eifelian; Fr., Frasnian.

Fig. 7. Stromatoporoids from the Jiwozhai reef, Jiwozhai Member, Dushan Formation, Givetian, Middle Devonian; Dushan, Guizhou, South China. A, B. Stictostroma saginatum (Lecompte, 1951) A. NIGP 177050; A1, tangential section showing the isolated pillars and locally irregular skeleton; A2, longitudinal section, note the prominently vertically erected mamelon;A3, enlargement ofA2, note the coarsely ordinicellular microstructure (arrows). B. NIGP 177051; longitudinal section, note the encrusting skeleton over Thamnopora sp. debris and a solitary rugose coral. C. Synthetostroma actinostromoides Lecompte, 1951, NIGP 177052; C1, longitudinal section; C2, tangential section.

Fig. 8. Stromatoporoids from the Jiwozhai reef, Jiwozhai Member, Dushan Formation, Givetian, Middle Devonian; Dushan, Guizhou, South China. A. Pseudotrupetostroma porosum (Yang and Dong, 1979), NIGP 177053; A1, longitudinal section; A2, tangential section; A3, enlargement of longitudinal section showing coarsely cellular microstructure coated tangential elements (arrows). B. Salairella buecheliensis (Bargatzky, 1881), NIGP 177054; B1, longitudinal section, note the predominance of the pachysteles in the right standard area and amalgamated structure in the left oblique orientation of the thin section; B2, tangential section, note the autotubes in the upper middle area; B3, enlargement of B1 showing coarsely cellular microstructure (arrows) partially transformed into melanospheric microstructure; such features demonstrate the likely diagenetic character of these microstructures and therefore their unreliability as taxonomic discriminators.