Early Cambrian phosphate-replicated endolithic algae from Emei, Sichuan, SW China

Diverse and abundant phospate-replicated microborings produced by endolithic microorganisms in the shells and sclerites of early skeletal fauna, collected from the Maidiping Formation at Maidiping, Emei, Sichuan, have been examined after the acetic acid etching of the samples. During early diagenetic period, a phosphate-moulted filling event existed prior to the aragonitic (or calcitic) host-shell-dissolution (or alteration), therefore, through decalcification by acetic acid, the phosphate-replicated microborings are frequently preserved on the phosphatic internal moulds of or under the phosphatized outer layers of the skeletal fossils. The nature of the microborings suggests they were produced by endolithic algae. Six species of five genera have been examined: 1) Cunicularius halleri - unbranched cylindrical endolithic filaments with diameters of 2.5-3.0 µm; 2) Cunicularius isodiametrus sp. nov.- unbranched cylindrical endolithic filaments with diameters of 4.0-6.7 µm; 3) Endoconchia? angusta - unbranched cylindrical endolithic filaments with spheroidal expansions, 3.0-6.0 µm in diameter; 4) Eohyella cf. elongata - branching endolithic pseudofilaments with diameters of 7.0-12.0 m; 5) Graviglomus cf. incrustus - solitary ellipsoidal or spheroidal vesicles, boring vertically, cross-sections 7.0-38.0 µm in diameter; 6) parenchymodiscus cf. endolithicus - colonial endolithic thalli, boring vertically, each colony consisting of 10-30 ellipsoidal coccoid vesicles, cross-section 9.0-17.3 µm in diameter. Among them, the former four species are tentatively assigned to cyanophytes, and the affinity of the latter two species is uncertain.