List of informally named dinosaurs

This list of informally named dinosaurs is a listing of dinosaurs (excluding birds) that have never been given formally published scientific names. This list only includes names that were not properly published ("unavailable names") and have not since been published under a valid name (see list of dinosaur genera for valid names). The following types of names are present on this list:

"Alamotyrannus" ("Ojo Alamo tyrant") is the informal placeholder name given to an as yet undescribed genus or species of tyrannosaurid from the Late Cretaceous period of North America. The fossils of this animal originate from the Ojo Alamo Formation in New Mexico and they were discovered during the early 2000s. The suggested binomial "Alamotyrannus brinkmani", was created when the paper describing the genus was written in 2013. "Alamotyrannus" lived during the early Maastrichtian.

Specimen ACM 7975, a jaw discovered in the Ojo Alamo Formation, New Mexico in 1924, has been tentatively identified as Gorgosaurus libratus but may instead belong to "Alamotyrannus" as per Dalman & Lucas (2013) and McDavid (2022). This specimen has been mentioned in a 2016 publication by Dalman and Lucas as an indeterminate tyrannosaurid without generic attribution, and it's noted that the specimen is under study by the senior author. Photograph taken by McDavid (2022) shows the specimen on display in the Beneski Museum of Natural History.

"Alan the Dinosaur" is the name given to a sauropod caudal vertebra (YORYM:2001.9337) found in 1995 in the Saltwick Formation (Middle Jurassic, Aalenian) of Whitby, England. It is the oldest sauropod found in the United Kingdom, dating back 176-172 million years ago. Its name references that of its discoverer, Alan Gurr, and the fact that it is not identifiable to species level. An analysis done in 2015 found that it was a member of Eusauropoda, could be excluded from Diplodocoidea, and was most similar to Cetiosaurus.

The fossil of "Alan" is housed in the Yorkshire Museum, where it forms part of the Yorkshire's Jurassic World exhibit, featuring a VR recreation.

"Allosaurus robustus" is an informal name used for specimen "NMV P150070", a theropod astragalus known from the Wonthaggi Formation (Early Cretaceous) of Victoria, Australia. When first studied, it was thought to have belonged to a species of Allosaurus. Samuel Welles challenged this identification as he thought that the astragalus belonged to an ornithomimid, but the original authors defended their classification. Sometime in the early 2000s, Daniel Chure examined the bone and found that it did not represent a new species of Allosaurus, but could still represent an allosauroid. At the same time, Yoichi Azuma and Phil Currie noted that the astragalus resembled that of their new genus Fukuiraptor. It may well represent a theropod related to Australovenator, though some argue that it could represent an abelisauroid. A 2019 study strongly supported a megaraptoran affinity for the astragalus.

The name "Allosaurus robustus", first confined as a museum label, was first published by Chure in 2000.

"Amargastegos" is an informal genus of extinct stegosaurid ornithischian dinosaur known from the La Amarga Formation of Argentina, named by Roman Ulansky in 2014 on the basis of MACN N-43 (some dorsal osteoderms, the cervical and caudal vertebrae, and one skull bone), and the type species is "A. brevicollum". In 2016, Peter Malcolm Galton and Kenneth Carpenter declared it a nomen nudum, establishing it as an indeterminate stegosaur.