drawing by marguerita
Nephila are large, conspicuous weavers of orb webs composed of golden silk, in tropical and subtropical regions. Nephilids have a sparse fossil record, the oldest described hitherto being Cretaraneus vilaltae from the Cretaceous of Spain. Five species from Neogene Dominican amber and one from the Eocene of Florissant, CO, USA, have been referred to the extant genus Nephila.
Here, we report the largest known fossil spider, Nephila jurassica sp. nov., from Middle Jurassic (approx. 165 Ma) strata of Daohugou, Inner Mongolia, China. The new species extends the fossil record of the family by approximately 35 Ma and of the genus Nephila by approximately 130 Ma, making it the longest ranging spider genus known.
Nephilidae originated somewhere on Pangaea, possibly the North China block, followed by dispersal almost worldwide before the break-up of the supercontinent later in the Mesozoic. The find suggests that the palaeoclimate was warm and humid at this time. This giant fossil orb-weaver provides evidence of predation on medium to large insects, well known from the Daohugou beds, and would have played an important role in the evolution of these insects.http://rsbl.
• Scientific studies
• Fauna of the Daohugou Beds
• See also
The geology of the Daohugou Beds is confusing because it is complex and does not conform; meaning that elements and layers of rock of different ages are mixed up together by folding and erosion and by volcanic activity. Liu et al. (2006) concluded that the rocks that bear the Daohugou Biota also include the Tiaojishan and Lanqi Formations. They demonstrated that the Jiulongshan Formation is older (middle Jurassic), and that the Tuchengzi Formation is younger (Late Jurassic).
Fieldwork published in 2006 has also found that the beds are consistent over a large area; from western Liaoning into Ningcheng county of Inner mongolia (Nei Mongol). The age of the Daohugou Beds has been debated, and a number of studies, using different methodologies, have reached conflicting conclusions. Various papers have placed the fossils here as being anywhere from the middle Jurassic period (169 million years ago) to the Early Cretaceous period (122 ma).
A 2004 study by He et al. on the age of the Daohugou Beds found them to be Early Cretaceous, probably only a few million years older than the overlying Jehol beds of the Yixian Formation. The 2004 study primarily used radiometric dating of a tuff within the Daohugou Beds to determine its age. However, a subsequent study by Gao & Ren took issue with the He et al. study. Gao and Ren criticize He et al. for not including enough specifics and detail in their paper, and also take issue with their radiometric dating of the Daohugou tuff. The tuff, Gao and Ren argue, contains crystals with a variety of diverse radiometric ages, some up to a billion years old, so using dates from only a few of these crystals cannot determine the overall age of the deposits. Gao and Ren go on to defend a Middle Jurassic age for the beds based on biostratigraphy (the use of index fossils) and the bed's relationship to a layer that is known to mark the Middle Jurassic-Late Jurassic boundary.
Another study, published in 2006 by Wang et al., found that the Tiaojishan Formation (159-164 million years old, Middle-early Late Jurassic in age) underlies, rather than overlies, the Daohugou Beds. Unlike the earlier study by Gao and Ren, Wang et al. found an overall similarity between the fossil animals found in the Daohugou Beds and those from the Yixian Formation. The authors stated that
"vertebrate fossils such as Liaoxitriton, Jeholopterus and feathered maniraptorans show much resemblance to those of the Yixian Formation. In other words, despite the absence of Lycoptera, a typical fish of the Jehol Biota, the Daohugou vertebrate assemblage is closer to that of the Early Cretaceous Jehol Biota than to any other biota."
Wang et al. concluded that the Daohugou probably represents the earliest evolutionary stages of the Jehol Biota, and that it "belongs to the same cycle of volcanism and sedimentation as the Yixian Formation of the Jehol Group." However, a later study by Ji et al. argued that the key indicator of the Jehol biota are the index fossils peipiaosteus and Lycoptera. Under this definition, the earliest evolutionary stage of the Jehol Biota is represented by the Huajiying Formation, and the Daohugou Formation is excluded due to the absence of Lycoptera fossils. Later in 2006, Liu et al. published their own study of the age of the Daohugou beds, this time using Zircon U-Pb dating on the volcanic rocks overlying and underlying salamander-bearing layers (salamanders are often used as index fossils). Liu et al. found that the beds formed between 164-158 million years ago, in the Middle to Late Jurassic.
Fauna of the Daohugou Beds
Beautifully preserved fossils of dinosaurs, pterosaurs, salamanders, insects, other invertebrates, conifers, ginkgoes, cycads, horsetails, and ferns, and even the earliest known gliding mammal (Volaticotherium) and an aquatic protomammal (Castorocauda) have been discovered in these rocks. These organisms were part of the Daohugou Biota, which was the ecosystem of that Jurassic time. The tuffaceous composition of some rock layers show that this was a volcanic area, occasionally experiencing heavy ashfalls from eruptions. The landscape then was dominated by mountain streams and deep lakes surrounded by forests of gymnosperm trees. Some authors have concluded that the Daohugou Biota is an early stage of the Jehol Biota, while recent work has demonstrated that the two are distinct.
The forests of the Daohugou biota grew in a humid, warm - temperate climate and were dominated by gymnosperm trees. There were ginkgopsids like Ginkoites, Ginkgo, Baiera, Czekanowskia, and Phoenicopsis. There were also conifers like Pityophyllum, Rhipidiocladus, Elatocladus, Schizolepis, and Podozamites. Also, Lycopsids like Lycopodites and Sellaginellities, horsetails (sphenopsida) like Equisetum, cycads like Anomozamites, and ferns (Filicopsida) like Todites and Coniopteris.
Amphibians of the Daohugou Beds
Gao & Shubin, 2003
Wang & Evans, 2006
The following orders are represented in the formation; Ephemeroptera, odonata, plecoptera, Blattodea, orthoptera, Heteroptera, Homoptera, Neuroptera, Coleoptera, Hymenoptera, and Diptera.
Insects of the Daohugou Beds
A tangle-veined fly
C. (Calosargus) antiquus
C. (C.) bellus
C. (C.) daohugouensis
C. (C.) hani
C. (C.) tenuicellulatus
C. (C.) validus
C. (Pterosargus) sinicus
A water boatman
A plectreurid spider
A Nemestrinoid fly
An archisargid fly
Dinosaurs (including birds) of the Daohugou Beds
A scansoriopterygid probably synonymous with Scansoriopteryx heilmanni
A primitive paravian
One or two specimens
A scansoriopterygid. Exact provenance of type specimen unknown, most likely from the Daohugou Beds
Lepidosaurs (lizards and relatives) of the Daohugou Beds
A new lizard with relatively short forelimbs
A new lizard with long hind limbs and a narrow body
pterosaurs of the Daohugou Beds
synapsids of the Daohugou Beds
A gliding mammal
• Yixian Formation
• Jehol Biota
• List of fossil sites (with link directory)