Triglypta Wang, 1984

TENG, XIAO, 2022, A morphological re-study of three spinicaudatan species from the Middle-Upper Jurassic of Gansu Province, northwestern China, Palaeoentomology 5 (4), pp. 327-339 : 328-332

Genus Triglypta Wang, 1984

Type species. Triglypta pingquanensis Wang, 1984 . Zhouyingzi of Pingquan City, Hebei Province, China; the Middle Jurassic Longmen Formation (originally Jiulongshan Formation, see in Huang, 2019).

Triglypta shandanensis (Chen in Zhang et al., 1976) emend.

( Figs 1–3 )

1976 Euestheria shandanensis Chen in Zhang et al., p. 127–128, pl. 21, figs 7–10, pl. 23, fig. 17

Material. NIGP 29776 , holotype, external mould of an individual with two valves. Middle–Upper Jurassic Longfengshan Formation at Shandan County of Zhangye City, Gansu Province, northwestern China ; NIGP 29777 , paratype, internal mould of a left valve, with some remains of the right valve. Middle–Upper Jurassic Longfengshan Formation at Shandan County of Zhangye City, Gansu Province, northwestern China ; NIGP 29793 , paratype, internal mould of a left valve, with some remains of the right valve. Middle Jurassic at Wangjiashan of Jingyuan County, Baiyin City , Jingyuan, Gansu Province, northwestern China .

Emended diagnosis. Carapace of medium size, shape oval; dorsal margin long; larval valve small; umbo in anterior and marginal position; growth lines stout, usually with central concave; growth bands wide and flat, 15–25 in number; growth bands ornamented with puncta; in the middle, antero-ventral and ventral part of the carapace, puncta cluster together to form fine reticulation; clustered puncta with linear arrangements to form radial lirae on growth bands near the antero-ventral and ventral margin of the carapace.

Description. Carapace of medium size (L = 5.8–6.2 mm, H = 4.5–5.1 mm, H/L = 0.78–0.82), shape oval; dorsal margin straight and long; larval valve small; umbo in anterior and marginal position; anterior and posterior margin straight, ventral margin curve; growth lines stout, usually with central concave, appearing as convex lines with a thin line on either side; growth bands wide and flat, 15–25 in number; growth bands ornamented with puncta, punctum 4–7 μm in diameter ( Fig. 1C, D ; 2B–H ; 3B– G ); in the middle, antero-ventral and ventral part of the carapace, puncta cluster together to form fine reticulation, mesh diameter 10–16 μm ( Figs 1E, F ; 2C ; 3E ); growth bands near the antero-ventral and ventral margin of the carapace, clustered puncta with linear arrangements to form radial lirae ( Figs 1E ; 2F ; 3E, F ); growth bands near the anterior and posterior margin of the carapace, puncta with dense arrangement ( Fig. 2G, H ).

Measurements.

Locality and horizon. Middle–Upper Jurassic Longfengshan Formation of Shandan County of Zhangye City and Middle Jurassic at Wangjiashan of Jingyuan County, Baiyin City, Gansu Province, northwestern China.

Remarks. The fine reticulation was the only ornamentation on growth bands in the original description of this species ( Zhang et al., 1976). Thus, Chen (1976 in Zhang et al., 1976) regarded this species as a member of the genus Euestheria . However, using a scanning microscope to examine the type material, the ornamentation on growth bands of this species is consist of puncta, and the fine reticulation observed under an optical microscope is formed by clustered puncta, and the radial lirae also failed to described in the previous studies. According to the ornamentation pattern, this species is a member of Triglypta rather than a Euestheria component.

The stout growth lines with a central concave makes this species different remarkedly from other Triglypta members.

Triglypta shandanensis distinctly resembles T. luanpingensis ( Zhang et al., 1987) in its outline and ornamentation. But the latter has more growth lines, narrower growth bands and, of course without stout growth lines with central concave.The reticulation is more developed in T. pingquanensis , T. haifanggouensis (Chen, 1976) and T. eedemtensis Li ( Li et al., 2014) in contrast to T. shandanensis ( Liao et al., 2017; Liao, 2022). This species is similar to Tianzhuestheria gansuensis Shen et al., 2002 in ornamentation, but each growth band of Tianzhuestheria is ornamented with puncta on the upper part and radial lirae intercalated with puncta on the lower part ( Shen et al., 2002).

Linglongtaestheria daxishanensis Li, 2020 resembles this species in ornamentation. However, Linglongtaestheria ornamented polygonal fine reticulation on growth bands near larval valve ( Li, 2020).

Qaidamestheria dameigouensis Wang, 1983 also has ornamented radial lirae formed by puncta on growth bands near the anterior margin of the carapace. In Qaidamestheria , however, the puncta are never clustered, and only a column of puncta between neighboring lirae ( Teng & Li, 2021).

Figures

FIGURE 2. Triglypta shandanensis (Chen in Zhang et al., 1976) emend. SEM images of the external mould of the right valve of the holotype specimen in Fig. 1A (NIGP 29776). A, The external mould of the right valve. B, Growth bands in the anterior middle part of the carapace, ornamented by puncta, appearing as fine nodules on external mould. C, Growth bands in the antero-ventral part of the carapace, ornamented by clustered puncta, clustered puncta with slightly linear arrangements to form irregular radial lirae, appearing as fine irregular striae with intercalated clustered nodules on external mould. D, Growth bands in the ventral part of the carapace, ornamented by puncta, appearing as fine nodules on external mould. E, F, Growth bands near the antero-ventral and ventral margin of the carapace, ornamented by radial lirae, which are formed by linearly arranged clustered puncta, fine striae with intercalated clustered nodules on external mould. G, H, Growth bands near the anterior and posterior margin of the carapace, ornamented by dense punctate reticulation, appearing as dense nodules on external mould. Scale bars = 1 mm in A, 100 μm in B–F and H, 50 μm in G.

FIGURE 3. Triglypta shandanensis (Chen in Zhang et al., 1976) emend. SEM images of the holotype specimen in Fig. 1A (NIGP 29776). A, The external mould of the left valve. B–D, Growth bands in the middle part of the carapace, ornamented by puncta, appearing as fine nodules on external mould. E, F, Growth bands near the antero-ventral margin of the carapace, ornamented by radial lirae, which are formed by linearly arranged clustered puncta, fine striae with intercalated clustered nodules on external mould. G, Growth bands near the postero-ventral margin of the carapace, ornamented by dense punctate reticulation, appearing as dense nodules on external mould. Scale bars = 1 mm in A, 100 μm in B–G.

FIGURE. 1. Triglypta shandanensis (Chen in Zhang et al., 1976) emend. A–C, Focus-stacked images. D–F, SEM images. A, The holotype (NIGP 29776), external mould of an individual with two valves. B, The paratype (NIGP 29793), internal mould of a left valve, with some remains of the right valve. C, The paratype (NIGP 29777), internal mould of a left valve, with some remains of the right valve. D, SEM images of the same individual in Fig. 1C (NIGP 29777). E, F, growth bands near the antero-ventral margin of the carapace, ornamented by clustered puncta; clustered puncta with linear arrangements to form radial lirae. Scale bars = 1 mm in A–D, 100 μm in E and F.

Measurements.