This formation was much swampier than the Yixian and was also part of the very extensive and well-known Jehol Group. It lies over the Yixian, and underneath the Fuxin Formation. It is 120 million years old, dating back to the Aptian Stage of the Early Cretaceous. It shares similar fossils as the Yixian but there are still plenty of differences in between them too.
The traditional plants, like Ginkgo, Taxus, Ephedra, Equisetum and many others still made up the majority of the flora in these swamps. For one, there are still exquisitely preserved fossils, and most of all there is a massive diversity of avialans.
These animals still have their feathers shown in the fossils, preserved once more in a mix of volcanic ash and fine sand. Confuciusornis, the most common of the Yixian genera, makes it through to this time as well, and it is still present in force. However, there are plenty of new genera in the Jiufotang. Some of the avialans here are quite large, some as big as turkeys. One of the biggest birds from this area is the herbivorous Jeholornis.
Two species are present, J. prima and the unfortunately named J. palmapenis. This is a rather primitive avialan, much more basal than its contemporaries. It was a seed-eater, and looked somewhat like other more basal forms such as Archaeopteryx and many dromaeosaurs. It was a better flier than Arhcaeopteryx, which isn’t saying much.
Hardly any of these primitive avialans were able to create an upstroke to allow powered flight. Jeholornis might have been able to flap downwards during a glide, though. Another big gliding form was Sapeornis also found in the Yixian. It had a very hawkish look to it, with long, narrow wings.
Sapeornis is also genuinely massive, with a wingspan of 1.4 meters across. This is nothing compared to some of the larger pterosaurs in its ecosystem but this is about as big Early Cretaceous birds managed to get. It had massive claws, almost like a modern raptor but it was a fruit- eater and used these claws for perching and grabbing branches instead of animals. The feet of Sapeornis were feathered too.
Both these large birds probably had a kiwi-like metabolism with a slow growth rate unlike most modern ones but were diurnal.
Other birds include the fish-eating Longipteryx that had lengthy jaws.
It was not just the avialans that managed to conquer the air in the Jehol. The stem-bird or non-avian dinosaur Microraptor was probably the top predator in the trees here. There have been various estimates of its size, from a little under a meter to 1.2 meters long. It has often been placed – rather mistakenly – in the Yixian when it is actually five million years younger. It was also incredibly common here. Microraptor had stiffened feathers on its legs, thus creating a legwing of sorts and also had classic wings attached to its arms.
This predator was able to glide from tree to tree with its arms spread out and the leg feathers extended over part of its tail. Since then though, it has been discovered that most stem-birds had similar gliding capabilities, most notably the juveniles of the famous Deinonychus.
Microraptor’s color is now known too. It was clothed in fully black feathers with a blue iridescence. This gave it the look of a four-winged raven. We know that it was an efficient hunter of contemporary birds.
The remains of both Sinornis and Longipteryx have been found in the stomachs of fossil specimens. It also seems to have caught fish, mammals and insects.
A much larger predator was Sinotyrannus, the largest carnivore in the Jiufotang. This was a 7-meter proceratosaur, the most primitive of all tyrannosauroids. Its closest relatives would have included creatures like the Jurassic Guanlong, a small, lean crested animal. If Sinotyrannus was as slim as its relatives, it would not have weighed very much. In fact, hardly any massive dinosaurs have been found in the Jiufotang.
A herbivorous theropod dinosaur here is Similicaudipteryx, which is an oviraptorid somewhere over a meter in length, another mere snack for a big carnivore.
There are no titanosaurs or big iguanodonts similar to those in the Yixian. Instead we have two species of Psittacosaurus, around 1 to 2 meters long.
There was, however a rather big ankylosaur named Chuanqilong. It had heavy armor so it cannot have been an easy kill for any predator.
There is much more diversity in the pterosaur fauna here than in the earlier Yixian. Where there was a fauna of filter-feeders dispersed through a number of separate units, there are now various genera with a variety of habits and diets.
The largest one here is the anhanguerid Liaoningopterus. This is a fish-eater with long wings and huge straight teeth, built for efficient soaring. Its wings spanned 5 meters, which makes it the largest pterosaur in its ecosystem. Other fish-eating genera include the evocatively named Ikrandraco and Guidraco, both pteranodontoids.
There are also many azhdarchoids in the Jiufotang swamps, although many of these are nothing special in terms of size. Most of them are chaoyangopterids, like Chaoyangopterus itself. They might have been either terrestrial stalkers or omnivores with varied diets.
We also have a possible juvenile tapejarid called Nemicolopterus. It has been associated with fellow tapejarid Sinopterus, as well as a juvenile of its own genus. Whatever it may turn out to be, it was probably an arboreal omnivore and the smallest non-hatchling pterosaur fossil known. Its wings spanned just 25 centimeters across.