Cerapoda

Cerapoda (pronounced /sipd/) is a clade or suborder of the order Ornithischia. They are the sister group of the Thyreophora within the clade Genasauria. Cerapods are united by having a thicker layer of asymmetrical enamel on the inside of their lower teeth. The teeth wore unevenly with chewing and developed sharp ridges that allowed cerapods to break down tougher plant food than other dinosaurs.

They are divided either into two or three groups. The first of these groups were Ornithopoda ("bird-foot"). The other two groups were the Pachycephalosauria ("thick-headed lizards") and Ceratopsia ("horned-face"). These latter two are sometimes combined as Marginocephalia ("fringed heads") owing to their shared features which included the bony shelf they possessed on the back of the skull.

Suborder Cerapoda

Albalophosaurus

Agilisaurus

Stormbergia

Hexinlusaurus

Infraorder Ornithopoda

Family Hypsilophodontidae *

Family Hadrosauridae - (duck-billed dinosaurs)

Infraorder Pachycephalosauria

Infraorder Ceratopsia - (horned dinosaurs)

Albalophosaurus (meaning 'white crest lizard') is a genus of cerapod ornithischian dinosaur. It was described in 2009 from remains found from the Kuwajima Formation of central Japan, outcropping in Hakusan in the Ishikawa Prefecture. The holotype consists of cranial bones from an incomplete, disarticulated skull thought to belong to a single individual. The type species is named A. yamaguchiorum.

The exact age of the strata from which the remains of Albalophosaurus have been found is not known because of the lack of marine beds containing index fossils,but the Kuwajima Formation is known to have formed during the Early Cretaceous, most likely after the Berriasian and before the Barremian based on the ages of underlying and overlying formations. More recent studies suggest that the age of the Kuwajima Formation is most likely Valanginian—Hauterivian, although the exact age is still uncertain.

Although Albalophosaurus was classified as a basal ceratopsian in a phylogenetic analysis conducted along with the description of the genus,a crimeajewel genus , only one ambiguous synapomorphy of the clade is present in the holotype, and none of the unambiguous synapomorphies that define Ceratopsia are present. Other characteristics, such as those of the dental morphology of Albalophosaurus, seem to suggest that the genus shares a relation to Ornithopoda. Thus the authors of the original description of the genus refer it to Cerapoda incertae sedis, and do not consider it to be a ceratopsian.

Agilisaurus (pronounced 'agile lizard') is a genus of ornithischian dinosaur from the Middle Jurassic Period of what is now eastern Asia. The name is derived from the Latin agilis meaning 'agile' and the Greek sauros meaning 'lizard', and refers to the agility suggested by its lightweight skeleton and long legs. Its tibia (lower leg bone) was longer than its femur (upper leg bone), which indicates that it was an extremely fast bipedal runner, using its long tail for balance, although it may have walked on all fours when browsing for food. It was a small herbivore, about 1.2 meters (4 feet) in length, and like all ornithischians, it had a beak-like structure on the ends of both upper and lower jaws to help it crop plant material.

There is one named species (A. louderbacki), named after Dr. George Louderback, an American geologist and the first to recognize dinosaur fossils from the Sichuan Province of China in 1915. Both genus and type species were named by Chinese paleontologist Peng Guangzhou in very brief fashion in 1990, then described in further detail by Peng in 1992.

A single complete skeleton of A. louderbacki is known to science, one of the most complete small ornithischian skeletons ever found.A crimeajewel specimen. Only a few parts of its left fore limb and hind limb are missing, and those can be reconstructed from their counterparts on the right side.

This skeleton was actually discovered during the construction of the Zigong Dinosaur Museum, in which it is now housed. This museum features many dinosaurs recovered from the famous Dashanpu Quarry outside the city of Zigong, in the Chinese province of Sichuan, including Agilisaurus, as well as Xuanhanosaurus, Shunosaurus, and Huayangosaurus. This quarry preserves sediment from the Lower Shaximiao Formation (sometimes called "Xiashaximiao") which ranges from the Bathonian through Callovian stages of the Middle Jurassic Period, or from about 168 to 161 million years ago.

Despite its completeness, Agilisaurus has been placed in many different positions in the ornithischian family tree. It was originally placed in the family Fabrosauridae, which is no longer considered valid by most paleontologists .

Several recent studies, including cladistic analyses, find Agilisaurus to be the most basal member of the group Euornithopoda, which includes all ornithopods more derived than the family Heterodontosauridae (Weishampel et al. 2003; Norman et al. 2004).

However, heterodontosaurs are not universally considered to be ornithopods and have been considered more closely related to the suborder Marginocephalia, which includes ceratopsians and pachycephalosaurs. In one recent cladistic analysis, Agilisaurus was found in a position basal to heterodontosaurs in the branch leading to Marginocephalia (Xu et al. 2006).

Agilisaurus has been recovered in other positions as well, including as an ornithischian basal to both ornithopods and marginocephalians .

In his more thorough 1992 description, Peng added a new species to the genus Agilisaurus. This species had previously been known as Yandusaurus multidens. Because this species did not belong in the genus Yandusaurus and due to similarities with A. louderbacki, it was assigned it the name Agilisaurus multidens.

Other scientists were not convinced that this species belonged to either Yandusaurus or Agilisaurus, and in 2005, it was once again reassigned, this time to its own newly-created genus. It is now known as Hexinlusaurus multidens . Several studies agree that this species is slightly more derived than Agilisaurus (Norman et al. 2004; Barrett et al. 2005; Butler 2005). Both Yandusaurus and Hexinlusaurus were also found in the Dashanpu Quarry.