page_title: Mosasaurus
section_title: Later discoveries
hierarchical_section_title: Mosasaurus / Research history / Later discoveries
caption_attribution_description: English: Title: Bulletin de la Société belge de géologie, de paléontologie et d'hydrologie Identifier: bulletindelasoci61892soci (find matches) Year: 1887 (1880s) Authors: Société belge de géologie, de paléontologie et d'hydrologie Subjects: Geology; Paleontology Publisher: Bruxelles&#160;: The society Contributing Library: Smithsonian Libraries Digitizing Sponsor: Biodiversity Heritage Library View Book Page: Book Viewer About This Book: Catalog Entry View All Images: All Images From Book Click here to view book online to see this illustration in context in a browseable online version of this book. Text Appearing Before Image: ' Text Appearing After Image: ' Note About Images Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.
context_page_description: Mosasaurus is the type genus of the mosasaurs, an extinct group of aquatic squamate reptiles. The genus lived from about 82 to 66 million years ago during the Campanian and Maastrichtian stages of the Late Cretaceous. The earliest fossils known to science were found as skulls in a chalk quarry near the Dutch city of Maastricht in the late 1700s, which were initially thought to have been the bones of crocodiles or whales. One particular skull discovered at around 1780, and which was seized during the French Revolutionary Wars for its scientific value and transported to Paris, was famously nicknamed the "great animal of Maastricht". In 1808, naturalist Georges Cuvier concluded that it belonged to a giant marine lizard with similarities to monitor lizards but otherwise unlike any animal known today. This concept was revolutionary at the time and helped support the then-developing ideas of extinction. However, Cuvier did not designate a scientific name for the new animal; this task was completed by William Daniel Conybeare in 1822 when he named it Mosasaurus in reference to its origin in fossil deposits near the Meuse River.
context_section_description: Confirmed species other than M. hoffmannii and M. missouriensis (considered to be the most well-known and studied species of the Mosasaurus genus) have been described. In 1881, Cope described the third Mosasaurus species from fossils including a partial lower jaw, some teeth and vertebrae, and limb bones sent to him from a colleague who discovered them in deposits around Freehold Township, New Jersey; these fossils now reside in the American Museum of Natural History as AMNH 1380. Cope declared that the fossils represented a new species of Clidastes based on their slender build and named it Clidastes conodon. But in 1966, paleontologists Donald Baird and Gerard R. Case reexamined the holotype fossils and found that the species belonged under Mosasaurus instead and renamed it Mosasaurus conodon. Cope did not provide an etymology for the specific epithet conodon, but etymologist Ben Creisler suggested that it may be a portmanteau meaning "cone tooth", derived from the Ancient Greek κῶνος (kônos, meaning "cone") and ὀδών (odṓn, meaning "tooth"), likely in reference to the smooth-surfaced conical teeth characteristic of the species.
  The fourth species M. lemonnieri was described in 1889 by Belgian paleontologist Louis Dollo from a fairly-complete skull recovered from a phosphate quarry owned by the Solvay S.A. company in the Ciply Basin of Belgium. The skull was one of many fossils donated to the Royal Belgian Institute of Natural Sciences by Alfred Lemonnier, the director of the quarry; as such, Dollo named the species in his honor. In subsequent years, further mining of the quarry yielded additional well-preserved fossils of the species, some of which were described by Dollo in later papers. These fossils include multiple partial skeletons, which were enough to almost represent the entire skeleton of M. lemonnieri. All known fossils of the species reside in the collections of the same museum; the holotype skull is cataloged as IRSNB R28. Despite being the most anatomically well-represented among the genus, the species was largely ignored by scientific literature. Paleontologist Theagarten Lingham-Soliar of Nelson Mandela University suggested two reasons for such neglect: the first reason was that M. lemonnieri fossils were endemic to Belgium and the Netherlands, areas that have generally not attracted the attention of mosasaur paleontologists. The second reason was that M. lemonnieri was overshadowed by its more famous and history-rich congeneric M. hoffmannii. The species has historically been a controversial taxon, and some of the literature that gives attention to M. lemonnieri argue that it is synonymous with other species. In 1967, research professor Dale Russell of North Carolina State University argued that differences between the fossils of M. lemonnieri and M. conodon were too minor to support species-level separation; per the principle of priority, Russell designated M. lemonnieri as a junior synonym of M. conodon. In a study published in 2000, Lingham-Soliar refuted Russell's classification through a comprehensive examination of the Royal Belgian Institute's specimens, identifying significant differences in skull morphology. However, he declared that better studies of M. conodon would be needed to settle the issue of synonymy. Such a study was done in a 2014 paper by Takehito Ikejiri of the University of Alabama and Spencer G. Lucas of the New Mexico Museum of Natural History and Science, who both examined the skull of M. conodon in detail and also argued that M. conodon and M. lemonnieri are distinct species. Alternatively, paleontologists Eric Mulder, Dirk Cornelissen, and Louis Verding suggested in a 2004 discussion that M. lemonnieri could actually be juvenile representatives of M. hoffmannii; it was justified by the argument that differences between the two species can only be observable in "ideal cases", and that these differences could be explained by age-based variation. However, there are still some differences such as the exclusive presence of fluting in M. lemonnieri teeth that might indicate the two 
caption: 1892 drawing of IRSNB 3189, of one of many M. lemonnieri skeletons described by Louis Dollo.
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