The First Report of a Himalayan Bradoriid Arthropod and the Paleogeographic Significance of this Form

Two arthropod specimens assigned to Anabarochilina australis (Hinz-Schallreuter, 1993) from the late middle Cambrian (Guzhangian Stage, Lejopyge acantha Biozone) Karsha Formation, Zanskar Valley, northern India comprise the first record of the Bradoriida from the Himalaya. These Indian specimens cannot be distinguished statistically from other A. australis material based on valve length and height ratios, and differ only slightly in other characters. These observations justify the synonymy of a number of similar forms worldwide that previously have been only questionably attributed to A. australis. The occurrence of the species in Australia, India, Laurentia, and Kazakhstan encompassed an equatorial distribution from approximately 20° north to 20° south during late middle Cambrian time and indicates that A. australis had the ability to disperse across deep ocean basins. Such a distribution is consistent with a planktonic lifestyle. In contrast, other congeneric species of Anabarochilina apparently had more localized occurrence or, in the case of A. primordialis, were distributed across several paleocontinents and climatic zones.