A new bivalved arthropod from the Cambrian (Stage 3) Qingjiang biota expands the palaeogeographical distribution and increases the diversity of Tuzoiidae

Abstract

The Cambrian Burgess Shale–type fossil Lagerstätten play a crutial role in revealing the origin and early evolution of arthropods. Tuzoiidae, one of the important bivalved arthropod groups, occupied a very important ecological niche in the Cambrian marine ecosystem. Here we describe a new taxon, Duplapex anima gen. et. sp. nov., in the family Tuzoiidae, on the basis of four exceptionally preserved specimens from the early Cambrian (Stage 3) Qingjiang biota of Hubei, South China. Duplapex is characterized by an ornament bivalved carapace, the ventral notch (vno) and doublure spine (dsp) of the valve, a pair of compound eyes connected by the fleshy annulated eye stalks. Despite having an unusual morphology for the group, the new taxon is recognized as a tuzoiid arthropod and indicates that these problematic euarthropods possessed a greater degree of morphological disparity than previously considered. D. anima, as well as the new reported Tuzoia. sp. from the Fandian biota, represent the oldest occurrence of Tuzoiidae, extending its stratigraphic range to Cambrian stage 3 and expanding the palaeobiographic distribution of the group to the northern border of Yangtze Platform.Thematic collection: This article is part of the Advances in the Cambrian Explosion collection available at: https://www.lyellcollection.org/cc/advances-cambrian-explosion

New Data on the Bivalved Arthropod Tuzoia From the Cambrian (Series 2, Stage 4) Guanshan Biota in Kunming, Yunnan, Southwest China

“…Tuzoia (Walcott, 1912) was one of the largest known Cambrian bivalved arthropods, occurring widely in the Burgess Shale-type Lagerstätten, ranging from the Cambrian Series 2 to the Miaolingian Series (Vannier et al, 2007;Robison et al, 2015;Ma et al, 2021), with remains in many parts of North America, Europe, Asia, and Australia (Figures 1, 2). According to Yuan and Zhao (1999), Vannier et al (2007), and Wen et al (2015), Tuzoia was a swimming animal as it occurred in continental shelf environments and deeper slope environments; it is possible that Tuzoia was benthic or nektobenthic.…”

“…Since Walcott first described Tuzoia in 1912, more than 20 species of Tuzoia have been recorded prior to this study (Vannier et al, 2007;Wen et al, 2019;Ma et al, 2021) (Figure 2). The first record of Tuzoia was a single specimen collected from the Burgess Shale (Miaolingian Series, Wuliuan Stage) in British Columbia, Canada, named T. retifera by Walcott in 1912.…”

The problematic Cambrian arthropod Tuzoia and the origin of mandibulates revisited

“…Emended diagnosis (from [ 28 ]): hymenocarine; valves symmetrical in the sagittal axis, generally amplete to postplete. Valves have at least an anterior and posterior carapace process, a postero-ventral spine and reticulate ornamentation.…”

“…Specimens preserving eyes had been previously reported from the Balang Formation [ 25 ], the Emu Bay Shale [ 27 ], the Burgess Shale [ 26 ] and the Guanshan Biota [ 45 ]. Eye peduncles have been described as long, at least three times longer than the eye itself [ 26 ] and annulated [ 25 , 28 ], being one of the main diagnostic features of Tuzoiidae [ 28 ]. Several specimens (figures 1 d , 3 e–h ; electronic supplementary material, figure S3c), as well as previously published material (Plate 6: Figs.…”

“…Therefore, the eye peduncles are shorter than previously described. Annulated eye peduncles were previously identified in Tuzoia [ 25 ] and Duplapex [ 28 ]. In the former, the structure in question is probably not an eye peduncle: it appears close to the ventral side of the carapace, far from the cephalic region, and its length is close to 20% of the total length of the carapace, which would make it an extremely long structure compared to the eye peduncles known in other bivalved arthropods.…”