Palaeontology 46, 1-20 (2003)
Early Cambrian lobopodian sclerites and associated fossils from Kazakstan

Jerzy Dzik
Instytut Paleobiologii PAN, Twarda 51/55, 00-818 Warszawa, Poland. e-mail:

Abstract. A low diversity fossil assemblage dominated by Mongolitubulus spines, from the Early Cambrian Geres Member of the Shabakhty Formation at Koksu, Malyi Karatau, Kazakstan, enables identification of its sclerite variability within the scleritome. No other sclerotised structures could be matched with the spines, indicating that these were the only sclerotised part of the body and periodically were shed out. The prominent spines of Mongolitubulus have a scale-like external ornamentation and fibrous internal structure. Possibly they armed the body of a lobopodian, similar to Xenusion. The Mongolitubulus spines belong to a series of Cambrian phosphatic fossils, the other end members of which are sclerites of Microdictyon, the second most abundant component of the Koksu assemblage. The latter superficially resemble schizochroal trilobite eyes, but in life covered the dorso-lateral sides of the body segments, as is evident from complete specimens from the Chinese Chengjiang locality. A pair of sclerites of Microdictyon, representing uncompleted exuviation, from Koksu show that each hole originally contained a non-phosphatised lenticular body. This makes a compound eye nature of the Microdictyon sclerites likely, and even their homology with arthropod eyes cannot be excluded.