Mesozoic

Lithium isotope constraints on Permian–Triassic continental weathering and multi-proxy comparison

2026-06-04T10:54:03+12:00

The Permian–Triassic transition (P–Tr, ca. 251.9 Ma) witnessed the most severe mass extinction of the Phanerozoic, triggered by intense volcanic activity and associated environmental catastrophes. Continental silicate weathering is central to understanding both the mechanisms of the extinction and the prolonged Early Triassic warmth, yet changes in its intensity and flux remain controversial. Lithium (Li) isotopes (δ7Li), a promising tracer of silicate weathering, have increasingly been applied to the P–Tr transition. However, δ7Li records from different sedimentary archives (marine carbonates, shales, cherts, and terrestrial clastic rocks) show stark discrepancies: some indicate rapid enhancement of chemical weathering, others invoke marine reverse weathering as the dominant control, and terrestrial evidence points to intensified physical erosion but suppressed chemical weathering. These contradictions arise because the marine δ7Li signal integrates multiple processes—continental weathering input, reverse weathering, and changes in the size of the oceanic Li reservoir—that cannot be disentangled by a single proxy. This review synthesises δ7Li records with the Chemical Index of Alteration (CIA), strontium (Sr) isotopes, osmium (Os) isotopes, and magnesium (Mg) isotopes across the P–Tr transition. We demonstrate a pronounced “intensity‑flux decoupling” in continental weathering, where traditional weathering indices (CIA) and terrestrial δ7Li indicate that chemical weathering intensity (measured as the chemical depletion fraction, W/D) did not increase globally and may have even decreased, while radiogenic Sr and Os isotopes record a sharp rise in the total terrigenous material flux. This paradox is reconciled with a regime of rapid physical erosion with limited chemical leaching, driven by vegetation collapse and a shortened hydrological cycle. Meanwhile, extreme Early Triassic marine δ7Li anomalies are largely controlled by enhanced reverse weathering and a likely reduced marine Li reservoir. A multi-proxy deconvolution framework thus allows a three-dimensional separation of weathering intensity, flux, and internal oceanic processes, offering a unified way to resolve current controversies. Future priorities include quantitative calibration of archive effects, systematic mapping of spatial heterogeneity, and numerical modelling of the marine Li cycle to advance quantitative understanding of Earth system crises in deep time.

The beetle fauna of mid-Cretaceous Kachin amber: a systematic synthesis

2026-06-23T13:27:49+12:00

Kachin amber from northern Myanmar, dated to the mid-Cretaceous (ca. 99 Ma), is an exceptional fossil Lagerstätte that preserves ancient terrestrial ecosystems in vivid, three-dimensional detail. Over the past decade, numerous beetle taxa representing a wide range of extant and extinct lineages have been described from this deposit, substantially expanding our knowledge of Cretaceous coleopteran diversity. Despite these discoveries, a comprehensive synthesis of the beetle fauna from Kachin amber remains unavailable. Here, we review the current record of beetles from Kachin amber and summarize the taxonomic composition of the fauna across major coleopteran groups. Particular attention is paid to fossils of evolutionary or ecological significance. This synthesis provides an updated overview of the diversity and systematic composition of the Kachin amber beetle fauna and highlights the importance of the deposit for future studies of beetle evolution and Cretaceous terrestrial ecosystems.

Early Cretaceous amber from the Heibaoshan-Handaqi Basin, Heilongjiang Province, Northeast China

2026-06-23T13:28:38+12:00

Cretaceous amber plays a crucial role in understanding the evolution of Late Mesozoic biotas and changes in palaeoclimates and palaeoenvironments. This paper reports amber, insects and plant fossils from the Lower Cretaceous Jiufengshan Formation in Heihe City, Heilongjiang Province, Northeast China, and presents the Fourier-transform infrared (FT-IR) spectroscopic characteristics of the amber. The Heihe amber occurs predominantly as irregular blocky pieces and layered forms, and is mainly preserved in coal seams. In addition, insect fossils belonging to multiple groups, including Coleoptera, Orthoptera, Hemiptera, Blattodea and Trichoptera (caddis cases), have been found in black shales near the amber-bearing horizons, further enriching the palaeobiological assemblage of the region. This discovery provides important empirical evidence for investigating the biotic characteristics and stratigraphic correlation of northern China during the late Mesozoic.

**A new species of Proptychopterina (Diptera: Nematocera: Ptychopteridae) from the Middle Jurassic of the Jiyuan Basin, China**

2026-06-23T13:29:44+12:00

A new species of the dipteran family Ptychopteridae, Proptychopterina jiyuanensis sp. nov., is described based on a nearly complete forewing from the Middle Jurassic Yangshuzhuang Formation in the Jiyuan Basin of central China. This new discovery represents the second fossil record of Ptychopteridae from China. We also revise the morphological features of Proptychopterina opinata Lin & Lukashevich, 2006, a species previously documented from the Middle Jurassic Daohugou Beds of Inner Mongolia, north-eastern China. The present discovery further supports biostratigraphic correlation between the Daohugou and Jiyuan fossil localities.

**Taxonomic revision of Dachibangus (Fulgoromorpha: Mimarachnidae) and the description of new species from Cretaceous Kachin amber**

2026-06-30T11:32:06+12:00

Mimarachnidae is an enigmatic Cretaceous planthopper family with remarkable taxonomic and morphological diversity documented from the mid-Cretaceous Kachin amber of Myanmar. We expand knowledge of the genus Dachibangus Jiang, Szwedo & Wang, 2018 through the description of three new species: D. pallidus sp. nov., D. partialis sp. nov., and D. pouilloni sp. nov. These new species permit an emended diagnosis of Dachibangus and support the synonymization of the recently described genus Trichotomus Wang, Zhuo, Luo & Chen, 2025 with Dachibangus, resulting in the new combination Dachibangus zhuoyuanshengi comb. nov. Our study indicates that the branching pattern of MP is more variable than previously recognized and cautions against its use as a diagnostic feature.

Pteronisculus luopingensis sp. nov., a new stem actinopterygian fish from the Middle Triassic (Anisian) of Luoping, Yunnan, China

2026-06-30T11:32:55+12:00

The extinct genus Pteronisculus represents a stem lineage of marine actinopterygians from the Early to Middle Triassic and is characterized by a toothed lacrimal contributing to the oral margin. To date, 13 species have been referred to Pteronisculus; most lived in the Early Triassic, except for two species from the Middle Triassic Luoping biota in Yunnan Province, China. Here, we report a new species of this genus, P. luopingensis sp. nov., based on five well-preserved specimens from the Luoping biota, documenting the third species of Pteronisculus recovered from the Middle Triassic. The new species possesses diagnostic features of Pteronisculus but is easily distinguished from other species of the genus by several autapomorphies of the skull, scales, and fins (e.g., a dermosphenotic shorter than the intertemporal, 89–90 lateral-line scales, and ~40 principal rays in each pelvic fin). The new finding enriches our understanding of the taxonomic diversity of Middle Triassic actinopterygians from the Yangtze Sea and further supports the area as a refuge for the survival of Pteronisculus during this epoch.

Mesozoic true polar wander: Evidence, uncertainties, and the East Asian record

2026-06-30T11:33:40+12:00

True polar wander reorients the solid Earth relative to the spin axis when mass redistribution changes the planetary inertia tensor. Rather than repeating a general history of true polar wander, this review assesses the confidence of proposed Mesozoic true polar wander events and explores their potential links with independent surface records. Specifically, we evaluate post-Pangaea rotations at ca. 250–200 and 200–150 Ma, the disputed Late Jurassic monster polar shift, smaller Late Jurassic–Early Cretaceous rotations and loops, and the Late Cretaceous 86–78 Ma oscillation. Their support varies widely because palaeomagnetic records differ in age control, remanence reliability, and reference-frame dependence, and are susceptible to local rotation, inclination shallowing, remagnetization, and unresolved plate motion. We therefore rank candidates using five criteria: multi-region coherence after plate restoration, robust age control, reliable palaeomagnetic data, geodynamically reasonable amplitude and rate, and surface records that match the predicted geographical pattern. East Asia provides a useful case because competing Jurassic–Early Cretaceous palaeolatitude models can be compared with regional aridification, basin evolution, volcanic-lacustrine deposits, and the Yanliao-Jehol fossil record. True polar wander is unlikely to be a single cause of environmental or biological change; its diagnostic value is spatial, because equatorward, poleward, and return motions should produce different climatic, stratigraphic, and biogeographic patterns. Progress will require tighter chronology, stronger tests of primary remanence, improved plate reconstructions, and explicit comparison of predicted true polar wander sectors with sedimentary, geochemical, palaeoclimate, and fossil archives.