The existence of late Cambrian (Furongian) trilobites in Myanmar (Burma) has been acknowledged since the 1970s, but no formal systematic descriptions of such fossils have been published to date. Herein, we provide such descriptions of some trilobites from the Molohein Group's Myet-Ye Formation from the Linwe area, Ye-Ngan Township of the southern Shan State. Three species from two genera are reported: Asioptychaspis (A. asiatica, previously known from the North China Block, and a new species, A. lata) and Eosaukia buravasi, also known from peninsular Thailand. The Molohein Group was initially assigned a late Cambrian age based on the reported, but unsubstantiated, occurrence of the Laurentian genera Saukiella and Drumaspis, and this age assessment is supported by the fauna we present, although Saukiella or Drumaspis remain unconfirmed from Myanmar. Asioptychaspis asiatica first appears in late Jiangshanian strata, and Eosaukia buravasi ranges up to the middle of Stage 10. Thus these ranges provide a more specific constraint on the age of the Molohein Group. Similarities are strong between upper Cambrian and Lower Ordovician successions in Sibumasu and northwestern Australia, particularly those from the Canning Basin succession. Regional geological data supports placement of Sibumasu adjacent to Western Australia during the Cambrian, without the Lhasa Block intervening between them, and Baoshan at the western end of Sibumasu during the early Paleozoic, towards the Himalayan margin. The new Burmese fauna is consistent with these suggestions, as they belong to the Sino-Australian faunal province.

The Ao Mo Lae Formation of the Tarutao Group crops out on Thailand's Tarutao Island and contains a diverse assemblage of late Furongian trilobite taxa, including several endemic forms. This study presents a new genus and species, Satunarcus molaensis, discovered at two locations on the island. A cladistic analysis of the kaolishaniid subfamily Mansuyiinae in light of Satunarcus and similar genera known from across upper Cambrian equatorial Gondwanan rocks suggests that the subfamily is polyphyletic in its current definition, and thus is not a natural group. Separating Mansuyia Sun, 1924 from the other taxa conventionally placed in Mansuyiinae permits recognition of a previously unrecognized monophyletic subfamily Ceronocarinae new subfamily. As established herein, this kaolishaniid subfamily contains Satunarcus n. gen. and all genera previously recognized as Mansuyiinae. with the exception of Mansuyia itself. Ceronocarinae n. subfam. occur in middle Jiangshanian to middle Cambrian Stage 10 sedimentary rocks from Australia, South China, North China, and Sibumasu, with most genera endemic to Australia. UUID: http://zoobank.org/618c5136-73f0-4912-a7d3-e56559d2a76c

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Later Cambrian and earliest Ordovician trilobites and brachiopods spanning eight horizons from five localities within the Sông Mã, Hàm Rồng and Đông Sơn formations of the Thanh Hóa province of Việt Nam, constrain the age and faunal affinities of rocks within the Sông Đà terrane, one of several suture/fault-bounded units situated between South China to the north and Indochina to the south. ‘Ghost-like’ preservation in dolomite coupled with tectonic deformation leaves many of the fossils poorly preserved, and poor exposure precludes collecting within continuously exposed stratigraphic successions. Cambrian carbonate facies pass conformably into Lower Ordovician carbonate-rich strata that also include minor siliciclastic facies, and the recovered fauna spans several uppermost Cambrian and Lower Ordovician biozones. The fauna is of equatorial Gondwanan affinity, and comparable to that from South China, North China, Sibumasu and Australia. A new species of Miaolingian ‘ptychopariid’ trilobite, Kaotaia xuanensis, is described. Detrital zircon samples from Cambrian–Ordovician rocks of the North Việt Nam and Sông Đà terranes, and from Palaeozoic samples from the Trường Sơn sector of Indochina immediately to the south, contain a predominance of ages spanning the Neoproterozoic period and have a typical equatorial Gondwanan signature. We associate the Cambrian and Tremadocian of the Sông Đà terrane with areas immediately to the north of it, including the North Việt Nam terrane and the southern parts of Yunnan and Guangxi provinces of China.

The field collections made from Burma (Myanmar) by the Geological Survey of India, and described by F.R.C. Reed more than a century ago, still provide the only ‘ground truthing’ for an important region of the Ordovician marginal terranes fringing Gondwana. A revision of these faunas is overdue, particularly as it is likely that further collections cannot be made in the northern Shan State in the near future. The specimens, stored in the Geological Survey of India collections in Kolkata, cannot be loaned. Sixteen species are fully revised herein; another twelve species are left under open nomenclature because of inadequacies in the material. Several of Reed’s species subsequently became type species of genera that have proved to be widespread: Birmanites Sheng, 1934, Encrinurella Reed, 1915, Neseuretinus Dean, 1967, and Pliomerina Chugaeva, 1956. Reed’s Ordovician trilobite collections came from two main areas: northern Shan State (Myanmar), and westernmost Yunnan (China). The Burmese (Myanmar) collections are from the Upper Ordovician (Katian) while Yunnan specimens are from the Middle Ordovician (Darriwilian), though Upper Ordovician trilobites also occur in the area. Both collections are predominantly from clastic strata. Based on a small new Katian collection from Pupiao, we report Neseuretinus birmanicus (Reed, 1906) in common between the northern part of the Shan State and western Yunnan. A few genera (Dionide Barrande, 1847, Phorocephala Lu, 1957, Lonchodomas Angelin, 1854, Nileus Dalman, 1827) are distributed worldwide, and include pelagic (Phorocephala) or deeper benthic (Dionide) taxa. The palaeogeographic comparisons offered by the other taxa are mostly peri-Gondwanan and extend from southwest China westwards (present geography) as far as the Iberian Pennsula. Birmanites is the type genus of a subfamily (Birmanitinae Kobayashi, 1960, revived herein) widely distributed over Ordovician Gondwana, and absent from Laurentia, Baltica and North China/Siberia. Mioptychopyge Zhou, Dean, Yuan & Zhou, 1998, probably belongs with the same group and is otherwise known from South China. Parillaenus Jaanusson, 1954, is also peripheral Gondwanan, as is Prionocheilus Rouault, 1847. The Reedocalymeninae Kobayashi, 1951 (Neseuretinus, Reedocalymene Kobayashi, 1951) are similarly diagnostic of peri–Gondwanan sites. However, some genera (Pliomerina, Encrinurella, Ovalocephalus Koroleva, 1959) have been associated with other oriental and Australian occurrences in particular, with ‘outliers’ in certain terranes in Kazakhstan, i.e. palaeotropical Gondwana.