Journal of Paleontology, 91(1), 2017, p. 100–115 Copyright © 2016, The Paleontological Society 0022-3360/16/0088-0906 doi: 10.1017/jpa.2016.121


Earliest occurrence of lophogastrid mysidacean arthropods (Crustacea, Eucopiidae) from the Anisian Luoping Biota, Yunnan Province, China


Rodney M. Feldmann,1 Carrie E. Schweitzer,2 Shixue Hu,3,4 Jinyuan Huang,3,4 Changyong Zhou,3,4 Qiyue Zhang,3,4 Wen Wen,3,4 Tao Xie,3,4 Frederick R. Schram,5 and Wade T. Jones1


1Department of Geology, Kent State University, Kent, OH 44240 USA ⟨rfeldman@kent.edu⟩ 2Department of Geology, Kent State University at Stark, 6000 Frank Avenue NW, North Canton, OH 44720, USA ⟨cschweit@kent.edu⟩ 3Chengdu Institute of Geology and Mineral Resources, Chengdu, 610081, China ⟨hushixue@hotmail.com⟩ 4Chengdu Center of China Geological Survey, No. 2, N-3-Section, First Ring, Chengdu 61008, China 5Department of Invertebrate Paleontology, Burke Museum of Natural History, University of Washington, Seattle WA 98195 USA ⟨fschram@whidbey.com⟩


Abstract.—Tiny, pelagic arthropods from the Anisian Luoping Biota exposed in two quarries near Luoping, Yunnan Province, China, represent the numerically most abundant organisms in the assemblage. They form the basis for definition of two, and possibly three, species referred to the order Lophogastrida, family Eucopiidae. Yunnanocopia grandis new genus new species and Y. longicauda n. gen. new species represent the oldest occurrence of mysida- ceans in the fossil record. Their anatomy allies them with the Ladinian species Schimperella acanthocercus Taylor, Schram, and Shen, 2001, from Guizhou Province, China, which previously was thought to be the oldest lophogastrid, and with extant species of Eucopiidae. Their appearance in the Anisian represents one additional element of the early faunal radiation within the Luoping Biota following the end-Permian extinction event. Presence of well-preserved oostegites, along with other morphological features, documents a conservative bauplan expressed in Eucopiidae.


Introduction


Mysidaceans are a group of shrimplike peracarid crustaceans. They are arrayed into three orders: Mysida, Lophogastrida, and Stygiomysida (Meland and Willassen, 2007; Wittmann et al., 2014). The earliest record of mysidaceans is in the Triassic of France (Bill, 1914) and China (Taylor et al., 2001). South China is famous for widespread exposures of marine deposits from Late Palaeozoic to Late Triassic, and the area is well known for fossil Lagerstätten with exceptional preservation of diverse fossils. Despite intensive excavations over decades, only a single mysidacean taxon, Schimperella acanthocercus Taylor, Schram, and Shen, 2001, has been reported from the Ladinian Stage of the Middle Triassic in SouthChina.Herewe report the discovery of a new mysidacean assemblage from the Anisian Stage of the Middle Triassic Luoping biota in SW China. This occurrence represents the oldest known assemblage of mysidaceans. The Luoping biota is a typical conservation Lagerstätte


with exceptional preservation. Mysidaceans are the most numerous animals within the Luoping biota (Hu et al., 2011). More than ten thousand individuals have been recovered so far. Associated fossils include marine reptiles, fish, bivalves, gas- tropods, echinoderms, ammonoids, lingulid brachiopods, plants, and other arthropods. In addition to the mysidaceans, horseshoe crabs (Zhang et al., 2008), isopods (Fu et al., 2010), lobsters (Feldmann et al., 2012), and shrimp (Schweitzer et al.,


2014) have been described. Thylacocephalans and a single myriapod are currently under study. The depositional environ- ment of the Luoping biota is interpreted as a semi-closed intra- platform basin, and the exceptional preservation of fossils is interpreted to have been due to anoxia of bottom water and microbial sealing (Hu et al., 2011; Luo et al., 2013). The material studied here was recovered from the middle


part ofMember II of the Guanling Formation at two quarries: the Dawazi Quarry (Quarry 1 of Feldmann et al., 2016 [2015]) and the Shangshikan Quarry (Quarry 2 of Feldmann et al., 2016 [2015]), Luoping County, Yunnan Province, SWChina (Fig. 1). The interval containing the fossil mysidaceans is approximately 16m thick, and is primarily comprised of thinly laminated micritic limestone alternating with thin- to moderately thick- bedded silty limestone. Fossil mysidaceans were obtained by splitting finely laminated micritic limestone. Most individuals are preserved as carbonized specimens, compressed in dorsal or lateral views on the bedding surface. A few individuals bear intestines preserved in 3-D configuration. Although several hundred individuals were examined in the course of this study, 25 were selected as type specimens for inclusion in this work. In addition to describing the new species of lophogastrid


mysidaceans representing the oldest known occurrence of the group, the presence of swarms of the organisms and the association of multiple species in single occurrences permits speculation on the lifestyle of the animals.


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