Shipingia hebaozhaiensis Shen

LI, GANG, 2022, SEM morphological study of the Late Triassic clam shrimp Shipingia hebaozhaiensis (Spinicaudata, Crustacea) from Yunnan, southwestern China, Palaeoentomology 5 (4), pp. 298-304 : 302

Shipingia hebaozhaiensis Shen in Zhang et al., 1976

( Figs 2 , 3 )

1976 Shipingia hebaozhaiensis sp. nov. Shen in Zhang et al., p. 145, pl. 32, figs 1–5.

1985 Shipingia hebaozhaiensis Shen : Chen & Shen, p. 107, pl. 7, figs 7, 8; text-fig. 66.

2007 Shipingia hebaozhaiensis Shen : Kozur & Weems, p. 146, pl. 6, figs 1–7.

Emended diagnosis. Carapace medium in size, elliptical in outline. Growth bands wide in the dorsal part, and narrow near the ventral margin. Growth bands near the umbo ornamented with irregularly arranged small and large sized reticulations. Growth bands in the middle part of the carapace, large sized reticulations located in the upper part of each growth band, and small sized reticulations located in the lower part of each growth band. Growth bands near the venter ornamented with small sized reticulations.

Dimensions of the figured specimen s. In order: specimen No., number of growth bands, length (mm), height (mm), height/length ratio: NIGP29859, 18, 7.4, 4.5, 0.61; NIGP29860, 7.3, 12, 4.5, 0.62.

Locality and horizon. Shiping County of Yunnan Province, Upper Triassic Ganhaizi Formation; Germany, the middle Norian Arnstadt and Stubensandstein 2 formations; The United States, the middle Norian Bull Run and Gettysburg Shale formations.

Description. Carapace moderate in size, elliptical in outline. Dorsal margin long and straight, small umbo located in its anterior part. Anterior and posterior margins rounded, ventral margin widely arched downward. Growth bands wide in the dorsal part, and become narrow near the ventral margin, 12 to 18 in number. Growth bands in the dorsal part ornamented with small and large sized, polygonal reticulations ( Figs 2B, C , 3B, C, F ), mesh wall thin, mesh diameter 20 to 100 µm. Each growth band in the middle part of the carapace is ornamented with largesized reticulations in its upper part, and transform to small-sized reticulations in its lower part ( Figs 2H , 3E ). Growth bands near the ventral margin are ornamented with small-sized reticulations, mesh diameter 10 to 30 µm ( Figs 2E, G , 3G, H ).

Remarks. Three species of Shipingia were originally described from the Upper Triassic Ganhaizi Formation: Shipingia hebaozhaiensis Shen in Zhang et al., 1976, S. baxinensis Shen in Zhang et al., 1976, S. xinjieensis Shen in Zhang et al., 1976. They differ from each other by their carapace outline. Shipingia hebaozhaiensis is elliptical, S. baxinensis is oval, and the small S. xinjieensis is rounded in outline. Considering that the three species are associated together in the same horizon, they may be the same species, and the outline difference may indicate sexual dimorphism or the effects of preservational distortion. Further taxonomic SEM restudy on the latter two species is needed.

Figures

FIGURE 2. Shipingia hebaozhaiensis Shen in Zhang et al., 1976. A is a light micrograph, the others are SEM images. A, External mould of a left valve, holotype, NIGP 29859. B, Large sized reticulate platform on a growth band near the umbo. C, A reverse image of B, showing the large sized reticulations on a growth band near the umbo. D, External mould on growth bands in the posterior dorsal part of the carapace, showing the transition from small to moderate nodules. E, A reverse image showing the fine reticulations on growth bands in the antero-ventral part of the carapace. F, A reversal image of D, showing the transition from fine to large-sized reticulations on growth bands in the posterior dorsal part of the carapace. G, A reverse image showing the fine reticulations on a growth band in the ventral part of the carapace. H, A reverse image, showing the transition from large-sized reticulation to fine reticulations on growth bands in the middle part of the carapace. Scale bars = 1 mm in A; 20 µm in B, C, G; 40 µm in H; 50 µm in E; 100 µm in D, F.

FIGURE 3. Shipingia hebaozhaiensis Shen in Zhang et al., 1976. A is a light micrograph, the others are SEM images. A, external mould of a right valve, NIGP 29860. B, small to large sized reticulate platform on a growth band in the antero-dorsal part of the carapace. C, D, medium to large sized reticulate platform on growth bands in the dorsal part of the carapace. E, small and large sized reticulate platform on growth bands in the anterior middle part of the carapace. F, small and large sized platform on growth bands in the posterior dorsal part of the carapace. G, small sized nodules on growth bands in the antero-ventral part of the carapace. H, small sized nodules on growth bands in the postero-ventral part of the carapace. Scale bars = 1 mm in A; 20 µm in B; 40 µm in C, G; 60 µm in E, F; 100 µm in D, H.