The age of the primitive ichthyopterygian Thaisaurus is more accurately defined due to the discovery of a new species of the ammonoid genus Marcouxia from beds about 2.4 m below the horizon from which the holotype of Thaisaurus chonglakmanii was collected in the Phukhaothong Dolomite Member of the Chaiburi Formation in the Phatthalung area, southern Thailand. The shell of Marcouxia chaiburiensis sp. nov. is characterized by a quadrate whorl section, an arched venter with a sub-acute keel-like elevation, and spiny tubercles on the ventrolateral shoulders as well as numerous regularly spaced, radial or slightly prorsiradiate ribs. Because the range of Marcouxia is limited to the Columbites parisianus Subzone of the lower Spathian (upper Olenekian, Lower Triassic) in the western USA, the age of Thaisaurus is likely constrained to the early Spathian, thus suggesting it is one of the oldest known ichthyopterygians.
A Late Devonian to Early Carboniferous radiolarian fauna is present in chert and siliceous shale of a chert-clastic section along the Khong River, Pak Chom area, at the Thai-Lao border of northeastern Thailand. The radiolarian fauna is composed of Stigmosphaerostylus variospina, Astroentactinia stellata, Astroentactinia multispinosus, Archocyrtium wonae, Archocyrtium riedeli, and other species and corresponds to the Famennian (Late Devonian) to Tournaisian (Early Carboniferous) radiolarian fauna reported from northwestern Europe, Australia, northern and southern Thailand, and southern China. Ten radiolarian species belonging to four genera including one unidentified genus are investigated. The radiolarian-bearing sequence was probably deposited in a pelagic or hemipelagic environment within the Paleotethys Ocean during Late Devonian to Early Carboniferous time. Furthermore, this chert-clastic section of Pak Chom area is thought to be deposited on the Nakhon Thai Block and subducted beneath the Indochina Block. This suggests that the age of subduction and accretion of the Naknon Thai Block is thought to have occurred at least after Early Carboniferous indicated by the occurrence of Late Devonian to Early Carboniferous radiolarians.
Moderately well-preserved Late Permian to Middle Triassic radiolarians are identified in chert beds that occur in the Shan-Thai Block of northern Thailand. These radiolarians are identical to the faunas of the Late Permian Neoalbaillella ornithoformis and N. optima Assemblage Zones and the Triassic Parentactinia nakatsugawaensis and Triassocampe coronata Assemblage Zones reported in chert sequences of Japan. We discovered the radiolarian faunas, apparently indicating Late Permian and Early Triassic ages, in almost continuous sequences of chert and shale exposed in the north of Chiang Mai. The occurrence of these radiolarian faunas provides important data to solve the P/T (Permian/Triassic) boundary in pelagic sequences. Our present discovery also furnishes significant data to reconstruct the paleobiogeography of Mainland Thailand during Late Permian to Middle Triassic times. Fifty species belonging to 35 genera, including three unidentified genera, are investigated taxonomically. Four new species Pseudospongoprunum ? chiangdaoensis, Cenosphaera igoi, Cenosphaera ? rugosa, and Tlecerina ? apsornae are described.
Abstract 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
Abstract Two types of chert are defined in Thailand based on lithology, faunal content, and stratigraphy. ‘Pelagic chert’ consists of densely packed radiolarian tests in a microcrystalline quartz matrix with no terrigenous material and is found as blocks embedded within sheared matrix. ‘Hemipelagic chert’ also has a microcrystalline quartz matrix, and contains not only scattered radiolarian tests, but also calcareous organisms such as foraminifers. The pelagic cherts range in age from Devonian to Middle Triassic, whereas hemipelagic chert is only from the Early to the Late Triassic. Lithological and stratigraphic characteristics indicate that the pelagic chert originated in the Paleo‐Tethys, whereas the hemipelagic chert accumulated on the eastern margin of the Sibumasu Block. The hemipelagic and pelagic chert are exposed in two north‐trending belt‐like zones. The western zone includes the hemipelagic chert, as well as glaciomarine and other Paleozoic to Mesozoic successions, overlying a Precambrian basement that consists exclusively of Sibumasu elements. The eastern zone contains pelagic chert and limestone and should be correlated to the Inthanon Zone. The Inthanon Zone is characterized by the presence not only of Paleo‐Tethyan sedimentary rocks, but also of Sibumasu Block elements that structurally underlie the Paleo‐Tethyan rocks. The boundary between the Sibumasu and Paleo‐Tethys zones is a north‐trending, low‐angle thrust that resulted from the collision of the Sibumasu and Indochina blocks.
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