Lapparentosaurus is a genus of macronarian sauropod dinosaur from the Middle Jurassic. Its fossils were found in Madagascar.
In 1895 Richard Lydekker named a new species of Bothriospondylus, B. madagascariensis based on fossils found before 1894 by J.T. Last in the Majunga Basin in layers of the Bathonian, the Isalo III Formation. Because there was no real connection with this English form, in 1986 José Fernando Bonaparte named a separate genus. The type species, the only known, is Lapparentosaurus madagascariensis. The generic name honours Albert-Félix de Lapparent. The holotype assigned by Bonaparte, MAA 91-92, consists of two neural arches. Much more abundant material has been referred, from at least three but perhaps as much as ten individuals from different growth stages. This includes vertebrae and limb elements but no skulls. The species is still lacking a good description and diagnosis. It should not be confused with ?Bothriospondylus madagascariensis, a distinct taxon.
Age determination studies performed using growth ring counts suggest that this sauropod took 31-45 years to reach sexual maturity and was relatively fast-growing given the presence of a large amount of fibrolamellar bone.
Though sometimes considered a brachiosaurid, cladistic analyses showed Lapparentosaurus to be a basal member of Macronaria or Titanosauriformes.