Today, let’s talk about another lagerstätte – not as well known as the Solnhofen Limestone, but pretty cool nonetheless. It’s called the Daohugou Bed or Daohuguo biota, and it’s found in northeastern China. That part of the world was warm and wet in late Jurassic time, about 160 million years ago or a bit older – but there is some controversy as to the age. Rocks deposited in this setting actually extend from the Jurassic up into the Cretaceous, where the fossils are called the Jehol biota. Whatever the age, and I think most researchers accept a late Jurassic age, a lush forest ecology developed.
Preservation is outstanding because the area was occasionally covered by thick, fine ash falls that likely killed the animals and preserved them intact, including exceptional detail of soft parts. For example, there’s a bee whose proboscis is preserved.
|Pencil drawing of gliding mammal Volaticotherium |
by ArthurWeasley; head based on skull image published by
Meng in Nature, Dec 2006. Used under Creative Commons license
Castorocauda was an aquatic mammal that lived in the lakes of the region. At 2 pounds and 17 inches, it was probably the largest Jurassic mammal, and shows that mammals were adapting to various niches including the water world early in their evolution. Castorocauda probably occupied ecological niches similar to those occupied by beavers and platypuses today. Its scientific name actually means “beaver tail,” and it did have a wide tail similar to those of modern beavers. It also had webbed feet. Castorocauda is another of those critters that may or may not have quite been true mammals. It depends on your definition and on the interpretation of fine details in the fossils.
Along with the small feathered dinosaurs, some of which appear to have been adapted to climbing trees, the fossils include several different types of pterosaur, the flying reptiles that were not closely related to the dinosaurs or their descendents, birds. Some of the pterosaurs had wingspans close to three feet, making them some of the largest animals in the Daohugou beds. The feathered dinosaurs, including Eosinopteryx, were generally small, perhaps a foot in length – but reconstructions of some of them look an awful lot like birds. No actual birds have been found in the rocks, but they’re still looking.
The forest where these animals lived was dominated by conifers, horsetail rushes, cycads and ferns, and gingko-like trees. No flowering plants of the modern sort. The insect life included lots of flies, various spiders including an orb-weaver, mayflies, and water beetles. Plenty of prey for the insectivorous mammals, salamanders, and small dinosaurs that lived there.
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J. Tuzo Wilson was born October 24, 1908, in Ottawa, Canada. In many ways, he was the architect of the concept of plate tectonics, which grew out of the idea of continental drift and sea-floor spreading. He synthesized many of the disparate ideas into an overarching theory. He also recognized the nature of transform faults, like the San Andreas, and their role in plate interactions.
Tuzo Wilson explaining transform faults (video)
—Richard I. Gibson
Pencil drawing of gliding mammal Volaticotherium by ArthurWeasley; head based on skull image published by Meng in Nature, Dec 2006. Used under Creative Commons license