Abstract
BackgroundThe Chengjiang biota is one of the most species-rich Cambrian Konservat-Lagerstätten, and preserves a community dominated by non-biomineralized euarthropods. However, several Chengjiang euarthropods have an unfamiliar morphology, are extremely rare, or incompletely preserved.ResultsWe employed micro-computed tomography to restudy the enigmatic euarthropod Jianshania furcatus. We reveal new morphological details, and demonstrate that the specimens assigned to this species represent two different taxa. The holotype of J. furcatus features a head shield with paired anterolateral notches, stalked lateral eyes, and an articulated tailspine with a bifurcate termination. The other specimen is formally redescribed as Xiaocaris luoi gen. et sp. nov., and is characterized by stalked eyes connected to an anterior sclerite, a subtrapezoidal head shield covering three small segments with reduced tergites, a trunk with 15 overlapping tergites with a well-developed dorsal keel, and paired tail flukes.ConclusionsThe presence of antennae, biramous appendages with endopods composed of 15 articles, and multiple appendage pairs associated with the trunk tergites identify X. luoi nov. as a representative of Fuxianhuiida, an early branching group of stem-group euarthropods endemic to the early Cambrian of Southwest China. X. luoi nov. represents the fifth fuxianhuiid species described from the Chengjiang biota, and its functional morphology illuminates the ecological diversity of this important clade for understanding the early evolutionary history of euarthropods.
Highlights
The Chengjiang biota is one of the most species-rich Cambrian Konservat-Lagerstätten, and preserves a community dominated by non-biomineralized euarthropods
Diagnosis Euarthropods with a subtrapezoidal head shield articulated with an anterior sclerite carrying stalked compound eyes
External segmental mismatch has been observed between the number of dorsal tergites and ventral appendage pairs; the segmental organization of sternites is uncertain, as these structures are not known from any fuxianhuiid described to date. Because of this derived condition, we describe the preserved exoskeletal trunk organization of fuxianhuiids based on the number and morphology of the tergites for clarity, and only make reference to the underlying segments in cases where there is no evidence for dorsoventral mismatch, such as the anterior small segments underneath the head shield, or the appendageless posterior trunk
Summary
The Chengjiang biota is one of the most species-rich Cambrian Konservat-Lagerstätten, and preserves a community dominated by non-biomineralized euarthropods. The Chengjiang biota of the Yu’anshan Member, Chiungchussu Formation, of Yunnan Province distinguishes itself from other fossiliferous localities in China by its unparalleled species richness, quality of fossil preservation, abundance and geographical coverage [3, 12], to the extent that it represents the only confirmed Tier 1 Burgess Shale-type deposit in the Yangtze Platform to date [13]. One of the main advantages of this approach is that it allows restudying poorly known taxa that are extremely rare, and precious within the Chengjiang biota Such is the case of Jianshania furcatus [41], Fig. 1 described from the Ercaicun section in Haikou, Kunming. We employ microCT to reveal previously unknown details of the dorsal exoskeleton and ventral appendage organization of Jianshania furcatus, and demonstrate that the type material encompasses two distinct species that contribute towards a better understanding of the diversity of Cambrian euarthropods in the Chengjiang biota
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