Timanotrypa australis, Ernst, 2016

Ernst, Andrej, 2016, Bryozoan fauna from the Permian (Artinskian-Kungurian) Zhongba Formation of southwestern Tibet, Palaeontologia Electronica (1946) 51 (9), pp. 1-59 : 35-37

Timanotrypa australis n. sp.

Figure 16 ; Table 21

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1973 Timanodictya ? sp. Sakagami, p. 85, pl. 14, fig. 3.

Etymology. The species is named after its occurrence in southern hemisphere (from Latin " australis " southern).

Holotype. SMF 23.165 .

Paratypes. SMF 23.166 – SMF 23.177 .

Type locality. Zhongba area of southwestern Tibet (E 84.31536, N 29.74233) .

Type stratum. Zhongba Formation, Permian (upper Cisuralian–Guadalupian).

Diagnosis. Colonies consisting of narrow bifoliate ribbons growing in the same plane, apparently pinnate; mesotheca straight to slightly zigzag folded; autozooecia tubular, semicircular in endozone, recumbent at mesotheca, bending sharply in exozone; diaphragms and hemisepta absent; exozonal walls laminated, traversed by abundant microstyles; depressed maculae without autozooecia occurring between pinnae.

Description. Colonies consisting of narrow bifoliate ribbons growing in the same plane, apparently pinnate (complete colony shape unknown). Separate ribbons 3.2–6.7 mm wide and 1.1–2.2 mm thick, with 0.26–0.65 mm wide exozone and 0.58– 0.90 mm wide endozones. Mesotheca straight to slightly zigzag folded, 0.025 –0.038 mm thick. Autozooecia tubular, semicircular in endozone, recumbent at mesotheca, bending sharply in exozone. Autozooecial apertures rounded to oval, arranged in 8–15 alternating rows. Autozooecial diaphragms not observed. Hemisepta absent. Endozonal walls hyaline, 0.015 –0.020 mm thick. Exozonal walls laminated, traversed by abundant microstyles. Microstyles 0.015 –0.025 mm in diameter. Maculae depressed, narrow, lacking autozooecia, positioned between pinnae across branch axis. Elliptical nodes regularly spaced between autozooecial apertures, 0.06–0.10 mm in diameter.

Remarks. Timanodictya ? sp. Sakagami, 1973 (p. 85, plate 14, figure 3) fits with the new species (average aperture width 0.16 (range 0.14–0.18 mm) vs. 0.16 (range 0.13–0.19 mm) in the present species). Timanotrypa australis n. sp. differs from T. borealis Morozova, 1970 from the Upper Permian (Kazanian) of the Russian Platform, by possessing smaller fronds (frond width 3.2–6.7 mm vs. 6–9 mm in T. borealis ; frond thickness 1.1–2.2 mm vs. 2.0–3.0 mm in T. borealis ).

The wall structure in timanodictyid bryozoans is quite variable and includes such structures as microstyles and stenostyles. The term "stenostyle" has been suggested by Gilmour and Snyder (1986) instead of "cappilares" used by the Russian authors (cf. Morozova, 1970; Gorjunova, 1994). However, these structures are not uniform in their morphology among timanodctyines. Gilmour (personal commun., 2015) understands rods of stellate appearance in transverse section as stenostyles, whereas others are of circular shape in their transverse sections (as known in the Family Girtyporidae , for example). The original diagnosis of the genus Timanotrypa Nikiforova (1938) includes "stellate acanthostyles". However, her figures 5-6 of plate 50 and figures 1-4 of plate 52 do not reveal any of such styles. Instead, they show small styles of circular shape in their transverse section. Neither the sample of Timanotrypa depicted by Gorunova (1994, plate 3, figure 1) shows any kind of stellate styles. The assignment of the present material to Timanotrypa followed largely on the base of the autozooecial shape, which is a very important character in the bryozoan morphology.

Occurrence. Rat Buri Limestone, Lower Permian (?Artinskian–Kungurian); Khao Raen, Thailand. Noonkanbah Formation, Lower Permian (upper Artinskian–Kungurian); Western Australia (unpublished data). Zhongba Formation, Permian (upper Cisuralian–Guadalupian); Zhongba area of southwestern Tibet.

Figures

FIGURE 16. Thin section photographs of Timanotrypa australis n. sp., holotype SMF 23.165 (1), paratype SMF 23.166 (2 and 3), paratype SMF 23.169 (4), and paratype SMF 23.171 (5). 1, oblique section of the pinnate branch; 2 and 3, tangential section showing autozooecial apertures, nodes (arrows) and microstyles; and 4 and 5, branch transverse section.