Silicified Middle Cambrian trilobites from Kyrgyzstan

Abstract:  A medium diversity silicified Middle Cambrian faunal assemblage occurs in an olistolith of bioclastic limestone within Silurian siliciclastic turbidites on the slopes of Arpatektyr Mountain in the eastern Alai Range, Kyrgyzstan. The fauna includes the trilobites Raragnostus cf. mirus , Altikolia kurshabica sp. nov., Corynexochina weberi , Dorypyge richthofeniformis , aff. Jincella sp., Olenoides comptus , Skreiaspis aff. spinosus and Suluktella mambetovi sp. nov. Three of these taxa ( C .  weberi , O .  comptus and R . cf.  mirus ) are considered locally to be characteristic of the Pseudanomocarina Beds, although Pseudanomocarina itself is not present. Altikolia and Suluktella are endemic to early Palaeozoic terranes of Central Asia, Corynexochina also occurs in South China and Skreiaspis is known elsewhere exclusively from the Middle Cambrian of 'West' Gondwana. Because of preservation in full relief, the silicified trilobite fauna allows a detailed understanding of some morphological structures, related especially to trilobite enrolment, otherwise inadequately known for many Mid-Cambrian polymerid trilobites.