40 km east of Mandalay City (Ordovician of Myanmar)

Where: Northern Shan, Myanmar (21.9° N, 96.5° E: paleocoordinates 21.9° N, 96.5° E)

• coordinate stated in text

• outcrop-level geographic resolution

When: Purple Shale Member (Hwe Mawng Formation), Hirnantian (445.2 - 443.4 Ma)

• The bed yielding the brachiopods in the Pa-thin area can probably be correlated with that near the base of the Pangsa-pye Formation in the Northern Shan State (Reed, 1915, Cocks and Fortey, 2002). The graptolites underneath the Hirnantia Fauna in the Mandalay Region include Metabolograptus extraordinarius, Normalograptus pseudovenustus, Koreanograptus acanthus and others, indicating a level of the M. extraordinarius Biozone, and those from the overlying rocks include Koreanograptus selectus, Normalograptus angustus and others, suggestive of Metabolograptus? perscuptus-Akidograptus ascensus Biozone (Chen et al., in press). Moreover, most of the brachiopod taxa correlate well with those of the Kuanyinchaio Bed (middle Hirnantian) in Yichang, western Hubei, Central China. Thus, it is more likely that the Hirnantia Fauna studied here is of middle Hirnantian age.

•Given as Hwe Mawng Purple Shale Member; it's not clear to me if Hwe Mawng Purple Shale is the name of the member, or if it is the Purple Shale Member of the Hwe Mawng Formation. This overlies the Katian - Hirnantian Kyaingtaung Formation and underlies the Late Hirnantian - Aeronian Panghsa-Pye Formation.

• bed-level stratigraphic resolution

Environment/lithology: marine; lithified, silty mudstone

• The rare occurrence of quartzose wacke in the silty mudstone may suggest either a sudden shift from shelf environments into shallower-water settings (e.g., nearshore) due to regression or alternatively, disturbances of seabed (e.g., gravity flows). In the view of sedimentary and fossil evidence, the latter may be more likely.
• This 45 cm-thick member is composed mostly of light brown, medium- to thin-bedded silty mudstone intercalated with quartzose wacke (Fig. 3). The Hirnantia Fauna is encountered only in the silty mudstone, which generally lacks any macroscopic evidence of major disturbance of the substrate except for a few borings (2–3 mm in diameter), and thus may represent deposition in quiet shelf environments. The quartzose wacke consists of angular to subangular detrital grains, which are matrix supported and poorly sorted. Mineralogical and textural maturities of the wacke are both poor due to the presence of rare feldspar (approximately less than 2% of the whole contents) and a high content of groundmass, respectively.

Size class: macrofossils

• A total of 1221 specimens were examined in this study.

Preservation: mold/impression

Collection methods: chemical

• All the fossils studied are preserved as moulds. The preservation is good, but the matrix is rather coarse, fragile and easily broken because of the deep weathering and unconsolidated matrix. To display external and internal morphologies in detail, latex casts are needed, although it is challenging to strengthen fossils prior to casting. PVB ethanol solution (a mixture of PVB powder and ethanol) and latex solutions I and II were employed for this purpose. The latex solution was prepared by mixing the commercially available product MOLD BUILDER and water at a volumetric ration of 1:5 (I) and 1:2 (II).

Primary reference: J. -Y. Rong, K. P. Aung, R.-B. Zhan, B. Huang, D. A.T. Harper, D. Chen, H.-H. Zhou and X.-L. Zhang. 2019. The latest Ordovician Hirnantia brachiopod Fauna of Myanmar: Significance of new data from the Mandalay Region. Palaeoworld 28 [P. Wagner/P. Wagner]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 202727: authorized by Pete Wagner, entered by Pete Wagner on 19.07.2019

Creative Commons license: CC BY (attribution)

Taxonomic list

• Brachiopods only; other taxa present but a small minority of the collection & not yet described.
 Orthotetida - Triplesiidae
Cliftonia psittacina Wahlenberg 1821
 Orthotetida - Chilidiopsidae
"Coolinia cf. dalmani" = Fardenia (Coolinia) dalmani
"Coolinia cf. dalmani" = Fardenia (Coolinia) dalmani Bergström 1968
 Strophomenida - Aegiromenidae
Aegiromena sp. Havlícek 1961
 Strophomenida - Leptostrophiidae
 Strophomenida - Rafinesquinidae
Leptaena sp. Dalman 1828
 Strophomenida - Glyptomenidae
Minutomena yichangensis Zeng et al. 2016
 Athyridida - Meristellidae
Hindella crassa Sowerby 1839
 Protorthida - Skenidiidae
 Rhynchonellida - Trigonirhynchiidae
"Plectothyrella crassicostis" = Plectothyrella crassicosta
"Plectothyrella crassicostis" = Plectothyrella crassicosta Dalman 1828
 Orthida - Draboviidae
Draborthis caelebs Marek and Havlíček 1967
 Orthida - Dalmanellidae
Mirorthis mira Zeng 1983
Levenea sp. Schuchert and Cooper 1931
 Orthida - Wangyuiidae
 Orthida - Plectorthidae
Giraldibella sp. Havlícek 1977
 Lingulida - Pseudolingulidae
? Pseudolingula sp. Mickwitz 1909
 Craniopsida - Craniopsidae
 Craniida - Craniidae
Petrocrania sp. Raymond 1910