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The developmental mode of four redlichiid trilobites is summarized, based upon exceptionally well‐preserved, articulated specimens from Cambrian Series 2 (stages 3 and 4) strata in southwestern China and South Australia. These relatively complete developmental sequences indicate a balanced rate in segment increase and addition to the thorax during the meraspid phase, which might explain why most redlichiids possess micropygous body patterning during ontogeny. In addition, an analysis of the size distribution, developmental strategy, and distribution of specimen numbers at different growth stages reveals a distinct developmental strategy during the redlichiid life cycle. A relatively short pre‐holaspid and a prolonged holaspid phase in these redlichiid taxa offers insight into the developmental control and life strategy in these primitive arthropods. [ABSTRACT FROM AUTHOR]

Detrital zircon samples from Cambrian and Lower to Middle Ordovician strata were taken across and along the strike of the Himalaya from Pakistan to Bhutan (~2000 km). By sampling rocks from one time interval for nearly the entire length of an orogen, and by covering a range of lithotectonic units, we minimize time as a significant source of variance in detrital age spectra, and thus obtain direct assessment of the spatial variability in sediment provenance. This approach was applied to the Tethyan margin of the Himalaya, which during the Cambrian occupied a central depositional position between two major mountain belts that formed during the amalgamation of Gondwana, the internal East African orogen and the external Ross-Delamerian orogen of East Gondwana. Detrital age spectra from our Lesser and Tethyan Himalayan samples show that well-mixed sediment was dispersed across at least 2000 km of the northern Indian margin. The detrital zircon age spectra for our samples are consistent with sources for most grains from areas outside the Indian craton that record Pan-African events, such as the Ross-Delamerian orogen; East African orogen, including the juvenile Arabian-Nubian Shield; and Kuunga-Pinjarra orogen. The great distances of sediment transport and high degree of mixing of detrital zircon ages are extraordinary, and they may be attributed to a combination of widespread orogenesis associated with the assembly of Gondwana, the equatorial position of continents, potent chemical weathering, and sediment dispersal across a nonvegetated landscape. doi: 10.1130/B30123.1

Precise biostratigraphic constraints on the age of the Tal Group are restricted to (1) a basal level correlative with the Anabarites trisulcatus-Protohertzina anabarica Assemblage Zone of southwest China, (2) a level near the boundary of the lower and upper parts of the Tal Group correlative with the early Tsanglangpuan Stage (Drepanuroides Zone), and (3) an interval low in the upper part of the Tal Group correlative with later in the Tsanglangpuan Stage (Palaeolenus Zone). These correlations are based on small shelly fossil and trilobite taxa. Other chronostratigraphic constraints include the marked negative [[delta].sup.13]C isotopic excursion coincident with the transition from the Krol Group to the Tal Group. This excursion is used as a proxy for the Precambrian-Cambrian boundary in several sections worldwide and, if applied to the Lesser Himalaya, indicates that the boundary is at or just above the base of the Tal Group. The upper parts of the Tal Group may be of middle or late Cambrian age and might form proximal equivalents of sections in the Zanskar-Spiti region of the Tethyan Himalaya. Both faunal content and lithological succession are comparable to southwest China, furthering recent arguments for close geographic proximity between the Himalaya and the Yangtze block during late Neoproterozoic and early Cambrian time. Trilobites from the uppermost parts of the Sankholi Formation from the Nigali Dhar syncline are described and referred to three taxa, one of which, Drepanopyge gopeni, is a new species. They are the oldest trilobites yet described from the Himalaya. Keywords: Cambrian, Himalaya, trilobite, chronostratigraphy, biostratigraphy.

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. [ABSTRACT FROM AUTHOR]