Ruiwen Zong

Sexual dimorphism, a widespread phenomenon, has been extensively researched in extant and fossil crustaceans. However, identifying sexual dimorphism in phyllocarid fossils preserved as isolated parts is often challenging, except in cases where the specimens are exceptionally well preserved, including those with soft tissues. This study proposes a novel approach by introducing the use of geometric morphometric techniques to identify sexual dimorphism in phyllocarid fossils based on carapace morphology. It presents a comprehensive re-analysis of Soomicaris ordosensis Liu et al., 2023a, carapaces from the Upper Ordovician in North China and Tarim Plates. Elliptic Fourier analysis was applied to quantify the size and shape variation in nearly 100 specimens. The results demonstrate the presence of significant sexual dimorphism in the length and shape of the S. ordosensis carapace. The carapace shape exhibited variation between the sexes: the posterodorsal margin of one group of carapaces gradually extends backward to form a posterodorsal spine; the carapaces of the other group have a convex posterior margin and lack a posterodorsal spine. Additionally, both types manifest an overall allometric growth pattern, albeit with distinct growth coefficients. Furthermore, the observed approximately 1:1 ratio between the two forms suggests that the population of S. ordosensis may have exhibited a dioecious mating system. Geometric morphometrics are a highly effective method for elucidating the subtle variations in the carapace morphology of S. ordosensis , thereby underscoring the cryptic dimorphism characteristics of fossil animals. This finding offers the first indirect evidence for egg-brooding behavior within the extinct order Archaeostraca.

The Great Ordovician Biodiversification Event (GOBE) greatly enriched marine biodiversity, promoted the complexification of ecosystems, and laid the foundation for the subsequent flourishing of marine life. The discovery of Ordovician Konservat-Lagerstätten is crucial for understanding the processes and ecosystem evolution associated with the GOBE. However, most known Ordovician Konservat-Lagerstätten are derived from shallow-water environments; those from deep-water (slope-basin) settings are extremely rare. This preservational bias severely limits a comprehensive understanding of the distribution and dynamic evolution of biodiversity in the Ordovician. Here, we report the Fuping Fauna, a deep-water slope facies Konservat-Lagerstätte from the Upper Ordovician (Katian) in the southern part of the North China craton. This fauna is composed mainly of eurypterids, cheloniellids, aglaspidids, bivalved arthropods, megacheirans, cnidarians, brachiopods, molluscs, conodonts, and coprolites, representing the first Ordovician Konservat-Lagerstätte discovered in the North China craton. Its unique environment (carbonate contourites) and distinctive biological features (diverse fauna with the absence of typical Ordovician taxa, such as trilobites and graptolites) enrich our understanding of the biological assemblages and ecological niches of the Ordovician deep-water ecosystems. The discovery of the Fuping Fauna not only expands the distribution range and sedimentary environment of the Ordovician Konservat-Lagerstätten but also indicates that the deep-water fauna exhibited high ecological complexity and biodiversity in the prime of the GOBE.

A diverse bryozoan fauna was identified from the upper member of the Hongguleleng Formation (Uppermost Famennian) in western Junggar, China. There are fenestrates, cryptostomates, trepostomates and cystoporates, including two new cystoporate species Cheilotrypa gongae sp. nov. and Cheilotrypa strunica sp. nov. It is the first record of Strunian bryozoans in Xinjiang. The assemblage includes previously known early Famennian taxa and new taxa for that region, which migrated into the Xinjiang basin from different shelves of Palaeotethys. The bryozoan fauna points to close palaeobiogeographical relations between Northwest China and Kazakhstan during the latest Devonian at species and genus level. At the genus level, bryozoans from Xinjiang and Kuznetsk basin, and south of Western Siberia are also similar.

After two pulses of mass extinction during the Late Ordovician, a continuous rise in sea level led to the formation of anoxic black shale deposits in deep-water areas in various regions of the world. These deposits usually contain only graptolite fossil assemblages. The discovery of sponge-dominated assemblages in graptolitic shale of the Ordovician–Silurian transition in South China has increased the known biodiversity within these strata. Here we document a new exceptionally preserved fauna, the Huangshi Fauna, in Rhuddanian (lower Silurian) black graptolitic shale of South China. The fauna is composed primarily of sponges, with additional representatives including cephalopods, arthropods, and some enigmatic carbon film fossils. Although this fauna exhibits less diversity compared to other early Paleozoic exceptionally preserved biotas in shallow-water facies, it provides new data on the biological assemblage of deep-water ecosystems after the first mass extinction. This sponge-dominated fauna not only enhances insight into the spatial and temporal distribution of sponges during the Ordovician–Silurian transition in South China but also implies that the depositional environment of the widespread lowest Silurian black shale was not entirely anoxic, indicating periods of intermittent oxygenation at the seafloor.

Stratigraphic data of the Huangshi Fauna, supplementary fossils, geochemical analysis of sponges, and measurements of cephalopods.

Stratigraphic data of the Huangshi Fauna, supplementary fossils, geochemical analysis of sponges, and measurements of cephalopods.