Lurdusaurus has a highly atypical body plan for an iguanodont, with a small skull, long neck, rotund torso, and powerful forelimbs and claws, somewhat reminiscent of a ground sloth.

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.

The generic name comes from Latin lurdus "heavy" and Ancient Greek sauros "lizard", in reference to the enormous weight of the fossils.

[1] In 2016, however, Gregory S. Paul proposed a significantly lower size estimate of 7 m (23 ft) in length and 2.5 t (2.8 short tons) in body mass.

[1] 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.

[1] In 2004, British paleontologist David B. Norman placed it outside of Iguanodontidae but still within the clade Styracosterna, which he defined as containing all iguanodonts with a hatchet-like sternum and flattened hand claws.

[3] 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.

[6] 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.

[5] The phylogenetic analysis of Karen E. Poole in 2022 found that Lurdusaurus formed a clade with other iguanodonts with robust forelimbs, Hypselospinus and Barilium.

[9] Dakotadon Iguanacolossus Owenodon Theiophytalia Lanzhousaurus Bolong Jinzhousaurus Lurdusaurus Barilium Hypselospinus Ouranosaurus Hippodraco Xuwulong Mantellisaurus Iguanodon Equijubus Proa Fukuisaurus Probactrosaurus Batyrosaurus Altirhinus Jeyawati Eolambia Protohadros Shuangmiaosaurus Levnesovia Tethyshadros Bactrosaurus Gilmoreosaurus Telmatosaurus Hadrosauridae 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.

[3] 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.

[1] Taquet and Russell compared the fortified hand with its massive thumb spike to a ball-and-chain flail, and believed it was primarily used for defense.

Geologically, it is composed of almost entirely cross-bedded fluvial sandstone (the sediments were deposited by rivers), intermittently interrupted by migrating sand dunes.