Acristavus information

Acristavus; Temporal range: Late Cretaceous, 79 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
	Skull cast
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	†Ornithischia
Clade:	†Ornithopoda
Family:	†Hadrosauridae
Subfamily:	†Saurolophinae
Tribe:	†Brachylophosaurini
Genus:	†Acristavus; Gates et al., 2011
Species:	†A. gagslarsoni
Binomial name
	†Acristavus gagslarsoni; Gates et al., 2011

Acristavus (meaning "non-crested grandfather") is a genus of saurolophine dinosaur. Fossils have been found from the Campanian Two Medicine Formation in Montana and Wahweap Formation in Utah, United States. The type species A. gagslarsoni was named in 2011. Unlike nearly all hadrosaurids except Edmontosaurus, Acristavus lacked ornamentation on its skull. The discovery of Acristavus is paleontologically significant because it supports the position that the ancestor of all hadrosaurids did not possess cranial ornamentation, and that ornamentation was an adaptation that later arose interdependently in the subfamilies Saurolophinae and Lambeosaurinae. It is closely related to Brachylophosaurus and Maiasaura, and was assigned to a new clade called Brachylophosaurini.^[1]

^ Gates, T.A.; Horner, J.R.; Hanna, R.R.; Nelson, C.R. (2011). "New unadorned hadrosaurine hadrosaurid (Dinosauria, Ornithopoda) from the Campanian of North America". Journal of Vertebrate Paleontology. 31 (4): 798–811. doi:10.1080/02724634.2011.577854. S2CID 8878474.

[Getal11-1] Gates, T.A.; Horner, J.R.; Hanna, R.R.; Nelson, C.R. (2011). "New unadorned hadrosaurine hadrosaurid (Dinosauria, Ornithopoda) from the Campanian of North America". Journal of Vertebrate Paleontology. 31 (4): 798–811. doi:10.1080/02724634.2011.577854. S2CID 8878474.

Acristavus information

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Acristavus

Maiasaura

Brachylophosaurini

Chakisaurus

Parasaurolophus

Probrachylophosaurus

Hadrosauridae

Hadrosaurus

Vectidromeus

Shantungosaurus

Iani

Edmontosaurus

Minqaria

Gonkoken

Iguanodon

Dryosaurus

Ornithotarsus

Iguanodontia

Tenontosaurus

Saurolophinae

Ornithopoda

Bonapartesaurus

Tietasaura

Tsintaosaurus

Augustynolophus

Oblitosaurus

Hypsilophodontidae

Olorotitan

Trachodon

Saurolophus