Soft-body preservation in the leaiid clam shrimp (Branchiopoda, Diplostraca) and its palaeoecological implications

in Crustaceana
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Leaia is a special genus of extinct “conchostracan” branchiopods; its soft parts have not been known until now. The leaiid specimens with soft bodies reported in the present paper came from two localities: the Upper Carboniferous Canso Group of New Brunswick, Canada, and the Permian Mount Glossopteris Formation of the Ohio Range, Holick Mountains, Antarctica. They include head, biramous antennae, mandible, shell gland, male claspers, and digestive tube. These parts together fully demonstrate that the leaiid clam shrimp indeed should be attributed to the crustaceans, instead of Mollusca. Based on the ribbed valves and structure of soft parts it should be placed in the branchiopodan Diplostraca. We believe that this group, which went extinct at the end of the Permian, is quite different from those of Laevicaudata, Spinicaudata, and Cyclestheriida. Hence, it should have its own higher taxon, Leaiina. The well-developed and sharply pointed head, delicate and short biramous antennae, in concert with the radial ribs on the valves probably indicate a burrowing in-faunal habit.


International Journal of Crustacean Research



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  • Leaia canadensis sp. nov. A, right valve, G. S. C. No. 12824-1; B, right valve, G. S. C. No. 12824-2, anterior margin broken; C, right valve, G. S. C. No. 12824-3, holotype, from Copeland, 1957, pl. 8 fig. 1 (left); D, right valve, posterior margin broken, G. S. C. No. 12824-4. Abbreviations: h = head; an = second antenna; m = mandible; sg = shell gland; dt = digestive tube; ac = anterior carinae; pc = posterior carinae; scale bars = 1 mm.

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  • Leaia gondwanella Tasch, 1965. Specimen OH3000 ⋅ 1, NIGPAS: 159635; interior view of the same left valve, using different lighting and magnifications. A, B, scale bar = 1 mm; C, scale bar = 0.74 mm; D, scale bar = 0.53 mm. Abbreviation: cl = clasper; other abbreviations same as fig. 1.

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  • Comparisons between the leaiid and living clam shrimp soft bodies. A, Leaia gondwanella Tasch, 1965, drawn based on fig. 2C; B-D, Leaia canadensis sp. nov., B, drawn based on fig. 1A; C, drawn based on fig. 1C; D, drawn based on fig. 1D; E, F, Spinicaudata, Leptestheria nanjingensis Zhang & Chen (in Zhang et al., 1976), collected from Jintan County of Jiangsu Province, China; E, showing soft body, lateral view; F, showing shell gland, dorsal view; G, H, Laevicaudata, G, Lynceus tatei (Brady, 1886), lateral view, after Olesen, 2009: 19, fig. 4A; H, Lynceus manchuricus Daday, 1927, collected from Taian County of Shangdong Province, China, showing shell gland, dorsal view; I, fossil specimen with soft parts, Euestheria luanpingensis Shen & Niu (in Zhang et al., 1987, pl. 2 fig. 5), lateral view, from the Middle Jurassic Jiulongshan Formation, at Zhouyingzhi village, Luanping County of Hebei Province, China. Abbreviations same as figs. 1-2, except for indicated am = adductor muscle; ep = exopod; mb = mandible. Scale bars = 1 mm unless stated otherwise.

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