Xiaheyan, the 2016 update

Publication Type:Conference Paper
Year of Publication:2016
Authors:O. Béthoux, Cui, Y., Gu, J. - J., Yang, Q., Robin, N., Sidorchuk, E., Du, S., Trümper, S., SCHNEIDER, J. Ö. R. G. W., Li, Y., GUERIAU, P., Ren, D.
Conference Name:The 7th International Conference on Fossil Insects, Arthropods and Amber
Date Published:26/04/2016
Publisher:Siri Scientific Press
Conference Location:National Museum of Scotland, Edinburgh

Within the last couple of years new data have been gathered on the early Late Carboniferous Xiaheyan locality (China), known to yield the earliest insect fauna. The newly described insect taxa include two new species of Palaeodictyoptera (Calvertiellidae and Spilapteridae; Xiaheyanella orta and Tytthospilaptera wangae, respectively), one being the smallest representative of the order; four species of Megasecoptera (Brodioptera sinensis, Sinopalaeopteryx splendens, Sinopalaeopteryx olivieri and Namuroptera minuta); and two new species of stem-Orthoptera (Archaeorthoptera; Xixia huban and Protomiamia yangi). It could be determined that the latter had a female-biased sexual size dimorphism, a pattern common among crown-Orthoptera but rarely documented in the fossil record. A specimen of a formerly described stem-Orthoptera species, viz. Miamia maimai, was recovered with a 800 μm long oribatid mite on it (Carbolohmannia maimaiphilus). The mite was investigated using phase contrast tomography. Specimen preservation and abundance distribution data derived from the fossil insect sample indicate that specimens from the corresponding layer were buried rapidly, indicating a syn-vivo association, considered phoretic. Incidentally, this discovery is the first pre-Cretaceous case of a fossil mite associated with another animal. A putative decapod crustacean is currently under investigation. In addition to the description of the arthropod fauna, sedimentology analyses were carried out. The 260 m. of the Tupo Formation, containing nine insect beds at Xiaheyan, were measured in cm-resolution. Fossil content and lithofacies patterns point to shallow marine to lagoonal deposits during a sea level fall. In those times the Xiaheyan area was situated in an inland sea at the southern margin of the North China block. The sea level fall was superimposed by sea level undulations of higher frequency, resulting in the alternating deposition of insect-bearing proximal siltstones and poorly fossiliferous distal claystones. Conodonts from abundant limestone concretions indicate an early Bashkirian age of the insect-yielding upper part of the Xiaheyan section. In addition, five ash horizons provide the chance for obtaining absolute ages. Future studies will concentrate on the description of additional insect taxa and in a refinement of the diversity and abundance data.

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