Burmese amber represents the world’s most diverse biota in the Mesozoic. Previous studies have focused on the biodiversity of its inclusions, as well as pholadid borings. Here we report a variety of marine animals symbiotic with or adhere to Burmese amber or the amber deposits, including crinoid columns, corals and oysters. We propose that there is no distinct evidence indicating the secondary transportation of Burmese amber over long distances. The ancient sedimentary environment was likely located in the coastal area. The hardening time of the resin was not long after secretion. The resin has been mixed with fragments of marine organisms in the ancient sediments, and has been deposited for a long time. The zircon age in the sediments surrounding amber approximately represents the age of Burmese amber, but due to limits of the method, the current zircon U-Pb SIMS age may be younger. Therefore, as far as the situation is concerned, the age of Burmese amber may be close to the boundary between the Albian and Cenomanian, or even late Albian. We suggest that it is plausible to generally refer to the age of Burmese amber as mid-Cretaceous, and a precise age requires further biostratigraphic and chronological studies.

Understanding the genealogical relationships among the arachnid orders is an onerous task, but fossils have aided in anchoring some branches of the arachnid tree of life. The discovery of Palaeozoic fossils with characters found in both extant spiders and other arachnids provided evidence for a series of extinctions of what was thought to be a grade, Uraraneida, that led to modern spiders. Here, we report two extraordinarily well-preserved Mesozoic members of Uraraneida with a segmented abdomen, multi-articulate spinnerets with well-defined spigots, modified male palps, spider-like chelicerae and a uropygid-like telson. The new fossils, belonging to the species Chimerarachne yingi, were analysed phylogenetically in a large data matrix of extant and extinct arachnids under a diverse regime of analytical conditions, most of which resulted in placing Uraraneida as the sister clade of Araneae (spiders). The phylogenetic placement of this arachnid fossil extends the presence of spinnerets and modified palps more basally in the arachnid tree than was previously thought. Ecologically, the new fossil extends the record of Uraraneida 170 million years towards the present, thus showing that uraraneids and spiders co-existed for a large fraction of their evolutionary history.

Confocal laser scanning microscopy is an essential analytical tool in biological, biomedical, and material sciences, integrating microscope manufacturing technology, optical-electronic technology, and computer technology. In the last decade, confocal laser scanning microscopy has been successfully applied to the study of amber bioinclusions. Enhanced signal to noise ratios, resolution power, capability of optical sectioning, three-dimensional reconstruction, and better performance when imaging thicker samples provide a great deal of valuable and detailed morphological information about amber fossils. We briefly discuss the practical applications of CLSM in amber studies and compare it with other imaging methods commonly used in the field, including bright-field microscopy, wide-field fluorescence microscopy, and micro-computed tomography. A general procedure for imaging amber inclusions with CLSM is provided, with a focus on pretreatments and image processing.

The Yanliao entomofauna, first established by Hong in 1983, refers to a Middle Jurassic insect assemblage widely distributed in northern China. The fossil insects are primarily preserved in the Haifanggou Formation and its correlated strata. In the beginning of this century, the Yanliao entomofauna was revived thanks to the discovery of abundant exceptionally preserved fossils, especially a huge number of insects, in the Daohugou area. Then, the Yanliao biota became well-known, and subsequently enlarged with more fossils collected from the interbeds of the overlying Tiaojishan Formation. Recently, the Yanliao biota has been divided into an early assemblage, represented by the Daohugou beds (Middle Jurassic to earliest Late Jurassic), and a late assemblage, represented by the Linglongta beds (early to middle Late Jurassic). The early insect assemblage, i.e. fossil insects from Daohugou, contains at least 24 insect orders, representing one of the most diverse entomofaunas in geological history. The age difference between core fossil layers of the Daohugou assemblage and the Linglongta assemblage is less than 5 Ma, but no same animal species from both have been discovered to date, because of violent tectonic movements and fierce volcanic eruptions. The representative insect from the early assemblage is Yanliaocorixa chinensis, which is distinctly different from the dominated corixids from the late assemblage. Insects of Yanliao entomofauna generally resemble those from the Shar Teg biota from Mongolia and the Karatau biota from Kazakhstan. The Yanliao biota rapidly declined in middle of the Late Jurassic (ca. 155 Ma) with the advent of arid climate, whereas some of the relict groups migrated southwards. Until the mid-Cretaceous, represented by the Burmese amber, a number of endemic insect groups of Daohugou are still recorded, but they have never been found in the Jehol biota, representing relicts of the Yanliao entomofauna.

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Triassic insect fossils from China are very limited. Here we report on numerous insect fossils discovered in the Upper Triassic Laohugou Formation at Heishanyao, Qinhuangdao, Hebei Province. These fossils are represented mainly by forewings of cockroaches and coleopteran elytra. The insect assemblage is most similar to that from the Upper Triassic Momonoki Formation of Japan. Fossils of the Laohugou Formation have been poorly known, so our discovery of new fossil insects bear significance for understanding the biota and sedimentary environment of this formation. The Mesozoic stratigraphic division in the Liujiang Basin has been controversial, and the usage of stratigraphic units has been inconsistent. Here we refine the stratigraphic sequence, from the bottom to the top, of the Upper Triassic Laohugou Formation, the Lower-Middle Jurassic Yaopo Formation, the Upper-Middle Jurassic Longmen Formation, the Upper Jurassic Tiaojishan Formation, and the Lower Cretaceous Zhangjiakou Formation. The Laohugou Formation is scattered in various basins in western Liaoning and northern Hebei, with the lower part mostly characterized by thick layers of complex conglomerates, suggesting a regional tectonic uplift. There is a sedimentary discontinuity between the Laohugou Formation and the Yaopo/Beipiao Formation, reflecting the uplifting activities during the late Late Triassic-early Early Jurassic in eastern China. The Laohugou Formation is overlaying on various ancient strata, representing the first regional unconformity of the northeastern margin of the North China Craton.