Soft-body structures of the trilobite Malongocephalusyunnanensis from the lower Cambrian Hongjingshao Formation in Yunnan, China
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Abstract:
Trilobites are among the most attractive Paleozoic arthropods whose exoskeletons show extremely high diversity. Compared with mineralized exoskeletons that are relatively easy to be preserved, the soft-body structures of trilobites are often difficult to be preserved in the fossil record, resulting in the difficulty in investi gating the internal anatomy and evolution of the trilobites. The exceptional conditions of the Burgess Shale-type Konservat-Lagerst?tten enable the opportunities for the preservation of delicate soft-body structures of the trilobites, providing material for examining their internal structures. Here we describe the soft-body structures of the trilobite ＜i style="letter-spacing: 0.1pt;"＞Malongocephalus＜/i＞ ＜i style="letter-spacing: 0.1pt;"＞yunnanensis ＜/i＞Zhang and Lin in Zhang ＜i style="letter-spacing: 0.1pt;"＞et al＜/i＞., 1980 from the Hongjingshao Formation (Cambrian, Series 2, Stage 3) at the Xiazhuang section, Chenggong, Kunming, Yunnan, China. The specimens show that the antenna of ＜i style="letter-spacing: 0.1pt;"＞M＜/i＞. ＜i style="letter-spacing: 0.1pt;"＞yunnanensis＜/i＞ is composed of at least 13 podomeres and that post-antennal appendages consist of flap-like exopodites. The digestive tract is differentiated into foregut, midgut, and hindgut, with three pairs of digestive glands in the head. This paper represents the first report of soft-body structures in the Family Redlichiida of Order Abadiellidae, which enriches the anatomical information of the early Cambrian trilobites. This study also compares and analyses the differences of relative lengths of antennae among members of Order Redlichiida, and discusses the structures of digestive system of the trilobites.
