Bayannurosaurus

Bayannurosaurus is a non-hadrosauriform ankylopollexian ornithopod described in 2018 by Xu Xing. It lived during the early Aptian period, being found in the Bayin-Gobi Formation of China. The genus includes the type species Bayannurosaurus perfectus. A phylogenetic analysis of Bayannurosaurus indicates that it is more derived than Hypselospinus, yet less derived than Ouranosaurus and just outside of the Hadrosauriformes. It was a large iguanodontian, measuring up to in total body length. The genus name Bayannurosaurus comes from Bayannur, the area where it was found, while the species name perfectus comes from the "perfect" preservation of the holotype specimen (IMMNH PV00001).

==Discovery and naming== In the summer of 2013 a joint expedition of the Long Hao Institute of Geology and Paleontology and the Institute of Vertebrate Paleontology and Paleoanthropology explored the Chulumiao locality of Bayannur, China. This locality is at the middle of the upper half of the Bayingebi Formation, giving it an early Aptian age, and the expedition collected a very well-preserved and nearly complete skeleton of an iguanodontian. This skeleton, housed as the Inner Mongolia Museum of Natural History as IMMNH PV00001, was described in 2018 by Chinese paleontologist Xu Xing and colleagues, who gave it the name Bayannurosaurus perfectus. The genus name is a combination of the geographical area Bayannur where it was found, and the Ancient Greek word σαυρος (sauros) for "lizard", while the specific name is in reference to the "perfect" preservation of the holotype skeleton. Known only from the holotype IMMNH PV00001, Bayannurosaurus is represented by a nearly complete, partially articulated skeleton preserving all regions of anatomy including the entire tail.