Lurdusaurus

In 1965, Philippe Taquet discovered the holotype specimen at the Gadoufaoua site of the Elrhaz Formation, in the Tenere desert of Niger. It consists of a nearly complete adult iguanodont skeleton with a fragmentary skull belonging to single individual, which was given the catalogue number MNHN GDF 1700. He noted it had rather massive proportions, and in 1976 noted it should probably be classified into a new genus while briefly describing the material. However, her dissertation was never published. In 1999, Turquet and American paleontologist Dale Russell published the first formal description, naming it Lurdusaurus arenatus. The generic name comes from Latin lurdus "heavy" and Ancient Greek sauros "lizard", in reference to the enormous weight of the fossils. The specific name arenatus is Latin for "sandy" because it was found in a desert. They also referred a dentary fragment, MNHN GDF 43G, and a right coracoid, GDF 381, to the species. ==Description==

The tip of the snout may have been about wide, and expanded back to . That is, like other iguanodonts, it did not have a duck-like bill. No teeth were preserved, but MNHN GDF 43G preserves the tooth sockets for 10 tooth rows within . The quadrate bone at the base of the skull has an exceptionally low stature at , in contrast to in Mantellisaurus and in Iguanodon. Based on the ratio between the length of the snout and the length of the rest of the skull in iguanodonts, the total length of the holotype's skull may have been in life. The headward dorsal ribs are preserved in their original positions, and show the torso was rather rotund. The diverging wings of the ilia and horizontally-orientated tailward dorsal ribs indicate a flat back about across. similar to other ankylopollexians such as Iguanodon and Ouranosaurus. Like Camptosaurus but unlike derived iguanodonts, the metacarpals (except for the thumb) were short and dumbbell-like as opposed to long and narrow. Compared to Camptosaurus, the unguals (claws) are flatter. The hand features a massive thumb spike. The pelvis is proportionally short but powerful, somewhat reminiscent of a ceratopsian pelvis. The femur slightly recurves toward the midline like in ceratopsians, and is flattened anteroposteriorly (from front to back) like in sauropods. The heavily built fourth trochanter is located on the bottom half of the femur, like Iguanodon but unlike Mantellisaurus and Ouranosaurus. The tibia is incredibly short relative to the femur, respectively vs. . The metatarsals were too short to make contact with each other, and there was likely a fleshy pad to support the weight. ==Classification==

In 1999, Taquet and Russell classified Lurdusaurus as a derived iguanodont or an intermediate between the iguanodonts and the more derived hadrosaurs, based on the presence of a posterolaterally orientated (towards the back and side) process on the sternum, slight tailward expansion of the pubis, a reduced posterior process of the pubis, and opisthocoelus (concave posterior ends) neck vertebrae and front dorsal vertebrae. They preliminarily placed it into the family Iguanodontidae, though conceded there is poor resolution on its higher classification, because the fourth trochanter is almost suspended off the femur like basal iguanodonts, but the neck vertebrae series is long like hadrosaurs. They were unable to satisfactorily explain the evolution of such an unusual body plan. In 2005, Chinese paleontologist You Hai-Lu and colleagues suggested that the newly discovered and massively built Lanzhousaurus from China was closely related to Lurdusaurus, and the former was basal to the latter. He classified both of them as basal styracosterns. In 2008, American freelance researcher Gregory S. Paul argued that because Lanzhousaurus has a much deeper prepubic process, the two genera are probably not closely allied, though such hypotheses are wholly unverifiable without more complete remains. Paul agreed that Lurdusaurus is more basal to Iguanodontidae based on its short, broad hands and massive thumb spike, but he noted that the contemporary and more derived hadrosauriform Ouranosaurus has similar hand morphology. Therefore, Lurdusaurus could be a basal hadrosauriform, but Paul could not resolve the matter any further until more complete remains are discovered. In 2009, American paleontologist Peter Galton placed Lurdusaurus at the base of Styracosterna and closely allied it with the Chinese Equijubus. He classified more derived iguanodonts into the new clade Iguanodontea. In 2012, Taquet agreed with Paul that it falls outside Iguanodontidae, but was also unsure how exactly Lurdusaurus relates with other iguanodonts. The phylogenetic analysis of Karen E. Poole in 2022 found that Lurdusaurus formed a clade with other iguanodonts with robust forelimbs, Hypselospinus and Barilium. }} ==Paleoecology==

with Nigersaurus and Suchomimus In 2007, paleontologist Thomas R. Holtz Jr. speculated that "Lurdusaurus may have been the dinosaur equivalent to a hippo" as they both share a heavy, stocky body plan. He suggested Lurdusaurus, like the hippo, was a generally slow-moving animal on both land and water, but could reach high speeds when necessary. Generally, iguanodonts are thought to have been predominantly bipedal or facultatively bipedal, though based on a suite of osteological characteristics, Lurdusaurus may have been an obligate quadruped, and perhaps even the first graviportal ornithischian thus identified. Overall, with its unusual and massive body plan including a small skull, circular chest, powerful and clawed forearms, and flattened femora, Lurdusaurus may have been reminiscent of a ground sloth. In squatting position, it may have resembled an ankylosaur.), the abelisaurid Kryptops, and the noasaurid Afromimus. The Gadoufaoua site has also yielded an ornithocheirid pterosaur, and the crocodylomorphs Anatosuchus, Araripesuchus, Stolokrosuchus, and the giant Sarcosuchus. It dates to roughly 112 million years ago during the Early Cretaceous at the Aptian–Albian boundary. Geologically, it is composed of almost entirely cross-bedded fluvial sandstone (the sediments were deposited by rivers), intermittently interrupted by migrating sand dunes. The presence of Nigersaurus suggests widespread forests with soft understory vegetation, such as immature ferns or horsetails. ==See also==