Integrative Research Center, Field Museum of Natural History, 1400S Lake Shore Drive, Chicago, IL, 60605-2496, USA.
Sci Rep. 2019 Mar 20;9(1):4938. doi: 10.1038/s41598-019-41310-1.
Beetles (Coleoptera) comprise about one quarter of all described animal species. One of the main contributors to their evolutionary success is the elytra, or hardened forewings, which have protective functions while maintaining their ability to fly. Unlike other beetles, some ship-timber beetles (Lymexylidae) have extremely small elytra and largely exposed functional hindwings. There is little fossil evidence illuminating the evolutionary history of short elytra in lymexylids. Here, I report five well-preserved lymexylid fossils in mid-Cretaceous and Cenozoic ambers from Myanmar (ca. 99 million years ago [Mya]), Russia (ca. 44 Mya), and the Dominican Republic (ca. 16 Mya). Three Cretaceous fossils have strongly reduced, shortened elytra, with unexpected variation in elytral size and shape, whereas very small, modified elytra are found only in much younger Dominican amber. These morphologically diverse extinct lymexylids shed new light on the early origin and evolutionary history of elytra reduction and its diverse variation in the ship-timber beetles. Based on the striking morphological similarities with extant lymexylids, these extinct taxa might have had the same, or similar, ecological, behavioural, and flight modes as the extant ship-timber beetles.
鞘翅目（Coleoptera）约占所有已描述动物物种的四分之一。它们进化成功的主要原因之一是鞘翅，即硬化的前翅，鞘翅具有保护功能，同时保持其飞行能力。与其他甲虫不同，一些船材甲虫（Lymexylidae）的鞘翅极小，功能后翅大部分暴露在外。化石证据很少能说明 lymexylids 短鞘翅的进化历史。在这里，我报道了来自缅甸（约 9900 万年前）、俄罗斯（约 4400 万年前）和多米尼加共和国（约 1600 万年前）的中白垩世和新生代琥珀中保存完好的五个 lymexylid 化石。三个白垩纪化石的鞘翅明显缩短，形状和大小也有出人意料的变化，而在更为年轻的多米尼加琥珀中只发现了非常小的、经过改造的鞘翅。这些形态多样的已灭绝的 lymexylid 为船材甲虫的鞘翅缩短的早期起源和进化历史及其多样化的变异提供了新的认识。基于与现存 lymexylid 具有惊人的形态相似性，这些已灭绝的类群可能具有与现存的船材甲虫相同或相似的生态、行为和飞行模式。
