UC Riverside

The Shan State of Eastern Myanmar forms the western portion of the Sibumasu Terrane, an originally peri-Gondwanan microcontinental fragment that also includes northwest and peninsular Thailand, peninsular Malaysia, and the Baoshan block of western Yunnan. Various lines of evidence, including shared trilobite fauna, support the close association of the Sibumasu Terrane with western Australia, North China, and South China, as well as with more distant terranes such as Laurentia and Kazakhstan. Although the presence of Cambrian trilobites in Sibumasu has been documented from Baoshan and the Tarutao Group of Thailand since the mid-1900s, and Cambrian trilobites have been known from Myanmar’s upper Molohein Group (Furongian-Tremadocian) since the 1970s, formal descriptions of Myanmar’s Cambrian trilobite fauna remained unpublished until 2021. A comprehensive systematic description of these trilobites is thus necessary for a more complete understanding of the biostratigraphy, paleogeography and evolution of peri-Gondwanan terranes, as well as of the geochronology and biostratigraphy of the latest Cambrian. In 2016 and 2020, field expeditions to the southern Shan State yielded abundant trilobite material from 12 localities representing the Myet-Ye formation of the upper Molohein Group, only three taxa of which have been described in a prior publication (Wernette et al., 2021). Here I present an integrated, complete systematic description of the Cambrian trilobite fauna of Myanmar collected to date. I describe 20 different trilobite taxa from the Myet-Ye material. 17 of these taxa have been identified to the genus level, and 11 have been further resolved to a species level. 2 new species of saukiid, Prosaukia kyaingseini and Diemanosaukia sp. 1, are described, as well as a potentially new species of tsinaniid, Tsinania? sp., though existing material is not sufficient for further specific diagnosis. The trilobite fauna of the Shan State largely corresponds to the Eosaukia buravasi and Asaphellus charoenmiti biozones of Thailand, representing the latest Cambrian and Early Ordovician respectively. The similarities between trilobite genera of the Shan State and those of Ko Tarutao, Baoshan, and western Australia are significant; however, other genera common to these areas, such as Quadraticephalus, have yet to be recovered in the Shan State.