Hadrosauridae

Hadrosaurids Temporal range: Late Cretaceous, 86–66 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Mounted skeleton of Edmontosaurus annectens, Oxford University Museum
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	†Ornithischia
Clade:	†Ornithopoda
Clade:	†Hadrosauromorpha
Family:	†Hadrosauridae Cope, 1869
Type species
†Hadrosaurus foulkii Leidy, 1858
Subgroups
†Aquilarhinus †Eotrachodon †?Fylax †?Gobihadros †Hadrosaurus †Lapampasaurus †Latirhinus †?Lophorhothon †Malefica †?Penelopognathus †?Plesiohadros †Yamatosaurus †Euhadrosauria/Saurolophidae †Lambeosaurinae †Saurolophinae
Synonyms
Trachodontidae (Lydekker, 1888) Saurolophidae (Brown, 1914) Lambeosauridae (Parks, 1923) Cheneosauridae (Lull & Wright, 1942) Ornithotarsidae (Cope, 1871)

Hadrosaurids (from Ancient Greek ἁδρός (hadrós) 'stout, thick', and σαύρα (saúra) 'lizard'), or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod family, which includes genera such as Edmontosaurus and Parasaurolophus, was a common group of herbivores during the Late Cretaceous Period.^[1] Hadrosaurids are descendants of the Late Jurassic/Early Cretaceous iguanodontian dinosaurs and had a similar body layout. Hadrosaurs were among the most dominant herbivores during the Late Cretaceous in Asia and North America, and during the close of the Cretaceous several lineages dispersed into Europe, Africa, and South America.

Like other ornithischians, hadrosaurids had a predentary bone and a pubic bone which was positioned backwards in the pelvis. Unlike more primitive iguanodonts, the teeth of hadrosaurids are stacked into complex structures known as dental batteries, which acted as effective grinding surfaces. Hadrosauridae is divided into two principal subfamilies: the lambeosaurines (Lambeosaurinae), which had hollow cranial crests or tubes; and the saurolophines (Saurolophinae), identified as hadrosaurines (Hadrosaurinae) in most pre-2010 works, which lacked hollow cranial crests (solid crests were present in some forms). Saurolophines tended to be bulkier than lambeosaurines. Lambeosaurines included the aralosaurins, tsintaosaurins, lambeosaurins and parasaurolophins, while saurolophines included the brachylophosaurins, kritosaurins, saurolophins and edmontosaurins.

Hadrosaurids were facultative bipeds, with the young of some species walking mostly on two legs and the adults walking mostly on four.^[2][3]