Austrokritosaurs Temporal range: Late Cretaceous, ~
Skeletal mount of Huallasaurus, an austrokritosaur, at the Natural Sciences Museum
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	†Ornithischia
Clade:	†Ornithopoda
Family:	†Hadrosauridae
Subfamily:	†Saurolophinae
Clade:	†Austrokritosauria Alarcón-Muñoz et al., 2023
Genera
†Bonapartesaurus †Huallasaurus †Kelumapusaura †Secernosaurus

Austrokritosauria is an extinct clade of saurolophine dinosaurs known from the Late Cretaceous of South America. The clade provides evidence of a faunal exchange from North America during the Cretaceous.^[1]

Description

Austrokritosaurs were medium to large herbivorous "duck-billed" (hadrosaur) ornithopod dinosaurs. They ranged in size from the smaller (possibly immature) Secernosaurus, at 4–5 metres (13–16 ft), to the larger Kelumapusaura, at around 8–9 metres (26–30 ft).^[2][3]

Biogeography

Likely dispersal route of the Austrokritosauria from North America to South America (red arrow)

Alarcón-Muñoz et al. (2023) suggested that austrokritosaurs shared an ancestor with the North American kritosaurins in the Santonian, about 85 million years ago, before dispersing into South America. This likely occurred via island chains and rafting. The South American hadrosauroid Gonkoken appears to have diverged from North American hadrosauroids at an even earlier time, about 91 million years ago in the Turonian.^[1] The Argentinian nodosaurid Patagopelta and North American titanosaur Alamosaurus likely experienced similar dispersal events from relatives in North and South America in the late Campanian–early Maastrichtian.^[4][5]

Classification

In the 2023 description of Gonkoken, Alarcón-Muñoz et al. erected Austrokritosauria as a new clade within the Saurolophinae, as a sister taxon to the Kritosaurini. Their phylogenetic matrix was modified from a 2022 study by Rozadilla et al. naming the hadrosaurs Huallasaurus and Kelumapusaura, which Alarcón-Muñoz et al. (2023) identified as austrokritosaurs.^[3] Austrokritosauria is defined as "the most inclusive clade containing Huallasaurus but not Gryposaurus". The results of their phylogenetic analyses of Saurolophinae are displayed in the cladogram below:^[1]

Saurolophinae

Wulagasaurus Acristavus Maiasaura Probrachylophosaurus Brachylophosaurus Austrokritosauria Secernosaurus Bonapartesaurus Kelumapusaura Huallasaurus Kritosaurini Kritosaurus Rhinorex Gryposaurus latidens Gryposaurus notabilis Gryposaurus monumentensis Kamuysaurus Prosaurolophus Saurolophus osborni Saurolophus angustirostris Laiyangosaurus Kerberosaurus Shantungosaurus Edmontosaurus regalis Edmontosaurus annectens

See also

• Timeline of hadrosaur research
• Alamosaurus
• Patagopelta

References