Revision of F. R. C. Reed’s Ordovician trilobite types from Myanmar (Burma) and western Yunnan Province, China

Abstract

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. 

Lower Ordovician Trilobites from SE Sardinia (Italy): A new record of the “Taihungshania bioprovince”

“…In addition, Nobiliasaphus occurs in both SE and SW areas of Sardinia. The distribution of Birmanites is narrower than that of Nobiliasaphus (Fortey et al, 2022) and evidences once again a difference between these two Sardinian regions.…”

“…Faunal links are numerous and well documented between the South Rheic margin and the south China during the Middle and particularly the Upper Ordovician (Fortey and Cocks, 2003;Ghobadi Pour et al, 2011Fortey et al, 2022), including Sardinia Leone, 1997, 2007). In marked contrast, during the Lower Ordovician the trilobite fauna is significantly less diversified with widespread and therefore less relevant taxa.…”

Katian (Late Ordovician) trilobites of the North Qilian Mountains and their palaeogeographical implications for the Proto‐Tethys Archipelagic Ocean

“…6, figs 1–4; Fortey et al . 2022, p. 319, figs 6, 7) from the Hwe Mawng Beds (Katian 4) of Hapakhi or Hwe Mawng, northern Shan State by having a narrower (tr.) preglabellar field (occupying 80% rather than 94% of the cranidial length), a pointed anterior cranidial margin and six pairs of pleural ribs (rather than eight).…”

Middle Ordovician trilobites from the Castillejo Formation, Eastern Iberian Range (NE Spain): taxonomic reappraisal, biostratigraphy, and correlation

“…Since most of the identified taxa have already been described in detail in the palaeontological literature of southwestern Europe (see above), the systematic part of this article is here replaced by some taxonom-ical notes on each of the recorded taxa, including the problems raised for their full identification. The order adopted by us largely follows the Treatise on Invertebrate Paleontology in its last edition (Fortey, 1997) with additions from Adrain (2011) and Fortey et al (2022).…”