Department of Agricultural Sciences, University of Naples Federico II, Portici, Italy.
Interuniversity Center for Studies on Bioinspired Agro-Environmental Technology (BAT Center), University of Naples Federico II, Portici, Italy.
Commun Biol. 2024 Aug 20;7(1):1023. doi: 10.1038/s42003-024-06678-5.
The Triassic represents a critical period for understanding the turnover of insect fauna from the Paleozoic to the Mesozoic following the end-Permian mass extinctions (EPME); however, fossil deposits from the Early-Middle Triassic are scarce. The exceptionally preserved 239 million-year-old fossil insect fauna recorded at Monte San Giorgio (Switzerland), including 248 fossils representing 15 major insect clades is presented here. Besides the exceptional features, including their small size and excellent preservation, the fossils have importance in the evolutionary history of the group. The taxonomic and ecological diversity recovered, including both freshwater (dragonflies and caddisflies) and terrestrial taxa (true bugs and wasps), demonstrates that complex environments sustained a paleocommunity dominated by monurans (thought not to have survived the EPME), midges, and beetles. Interestingly, a blattodean-like fossil bearing an external ootheca was also found, important for understanding Paleozoic roachoids to extant cockroaches' transition and the evolution of maternal brood care. Moreover, the youngest and first complete specimen of †Permithonidae and the oldest sawfly fossils were discovered. Finally, round-shaped bodies, compatible with seminal capsules or lycophyte spores, were found on the abdomens of several midge-like individuals. If these are spores, non-seed-bearing plants could have been the first entomophilous plants rather than gymnosperms, as recently supposed. Altogether, these fossils contribute substantially to understanding insect evolution and Paleozoic-Mesozoic faunal turnover.
三叠纪是了解古生代到中生代昆虫动物群更替的关键时期，因为在此期间发生了二叠纪末大灭绝事件（EPME）；然而，早-中三叠世的化石沉积却非常稀少。这里介绍的是来自瑞士圣乔治山的 2.39 亿年前保存异常完好的昆虫化石群，包括 248 个化石，代表了 15 个主要昆虫类群。除了具有代表性的特征，包括其小巧的体型和极好的保存状态外，这些化石在该群体的进化历史中也具有重要意义。恢复的分类和生态多样性，包括淡水（蜻蜓和石蛾）和陆地生物（真昆虫和黄蜂），表明复杂的环境维持了以单孔目动物（据认为它们没有在 EPME 中幸存下来）、摇蚊和甲虫为主的古群落。有趣的是，还发现了一个类似蟑螂的化石，带有外部卵囊，这对于了解古生代蟑螂到现存蟑螂的过渡以及母体育雏的进化非常重要。此外，还发现了†Permithonidae 科的最年轻和第一个完整标本，以及最古老的叶蜂化石。最后，在几个类似摇蚊的个体的腹部发现了圆形的身体，与精液囊或石松孢子兼容。如果这些是孢子，那么非种子植物可能是最早的传粉植物，而不是最近假设的裸子植物。总的来说，这些化石为了解昆虫进化和古生代-中生代动物群更替做出了重要贡献。
