ИСТИНА

Presumable Cambrian rocks in Malaysia are located in the northwestern domain of the Western Belt, namely, in the State of Kedah (northwestern Langkawi archipelago and nearby mainland Kedah) and – to a lesser extent – the neighbouring State of Perlis, where the siliciclastic Machinchang and Jerai formations crop out. The Machinchang Formation has a close lithological similarity to the Tarutao Formation (Tarutao Island, Thailand), both formations are dominated by quartzose sandstone, with some siltstone and subordinate conglomerate and ash beds, but the latter yields late Cambrian (Furongian) and earliest Ordovician trilobite faunas. During new detailed paleontological and sedimentological investigations, the trilobites Prosaukia? sp., Hoytaspis? sp., Lichengia? tarutaoensis, “Eosaukia” buravasi, Lophosaukia sp. and Quadraticephalus sp., as well as multiple disarticulated rhynchonelliform brachiopods and a sessile delicate dendroid fossil of tentative cnidarian affinities (Marcusodictyon) are found in the upper Chinchin Member of the Machinchang Formation. This dominantly saukiid trilobite nearshore fauna mirrors the Furongian fauna of the Tarutao Formation, broadly indicates the upper Cambrian age of the Chinchin Member and confirms the affinities of the both formations to a single sedimentary basin. As even thick-shelled individuals are disarticulated and broken, a high hydrodynamic activity in the place of burial is suggested. The most interesting component of this fauna are the brachiopods. Despite a poor preservation of valves (imprints and moulds), several individuals show a discernible external ornamentation and details of shell interior. These brachiopods are subdivided into five groups according to the shell growth type, ornamentation and inner peripheral rim. Three of these groups can be ascribed to orthids, billingsellids and strophomenids. The most interesting component of the assemblage are strophomenids with external ornamentation characterizing by regular alternation of costae of two orders; long posterior margin, stretched ears and peripheral rim on the inner valve interior surfaces; and a diminutive apical foramen on a single ventral valve. Probably, these brachiopods are the oldest known strophomenids.