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| Kelumapusaura machi Rozadilla, Brissón-Egli, Agnolín, Aranciaga-Rolando & Novas, 2022 |
Abstract
Here we describe a new hadrosaurid from the Upper Cretaceous (Campanian–Maastrichtian) Allen Formation of Río Negro Province, north-west Patagonia. The new taxon is based on cranial and postcranial elements from subadult and adult specimens. The new taxon may have reached 8–9 m in total body length, and it is diagnosed by a unique combination of characters, including a very low maxilla with respect to the dentary, and a dentary with a prominent and elongate anterior process with a deep groove on its anterior end, among other features. The new taxon is known from well-preserved elements and constitutes one of the most complete hadrosaurids known from South America. Features of the teeth, cranial and postcranial bones of the new taxon overlap with those of other hadrosaurid specimens previously recorded from this continent. This new evidence allows us to recognize that Secernosaurus koerneri, Bonapartesaurus rionegrensis and ‘Kritosaurus’ australis are valid taxa. The latter can be distinguished from the other South American taxa, as well as from Kritosaurus from North America. Thus, a new generic name is proposed for the species ‘Kritosaurus’ australis. Phylogenetic analysis recovers a new clade of South American hadrosaurids composed of the new taxon, ‘Kritosaurus’ australis, Bonapartesaurus and Secernosaurus. The new South American clade is tentatively nested among Kritosaurini and is supported by several traits, including an ilium with a subhorizontal ridge separating the preacetabular notch from the pubic pedicle, a longitudinal ridge on the dorsal surface of the postacetabular process, and a twisted distal end of the postacetabular process. The recovery of a monophyletic clade of South American hadrosaurids indicates that the history of the clade on Gondwanan landmasses is far from well understood, and new discoveries may change the current picture of the taxonomy and phylogenetic relationships of southern duck-billed dinosaurs.
Keywords: Hadrosauridae, Patagonia, Late Cretaceous, Secernosaurus koerneri, ‘Kritosaurus’ australis
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| silhouette of Kelumapusaura machi gen. et sp. nov. The bones in yellow belong to the holotype (MPCN-PV-807) and whitebones belong to the paratypes (not to scale). The grey silhouette represents the largest paratype specimen (MPCN-PV-808). |
Superorder Dinosauria Owen, 1842
Order Ornithischia Seeley, 1887
Infraorder Ornithopoda Marsh, 1881
Family Hadrosauridae Cope, 1869
Subfamily Saurolophinae Brown, 1914
Tribe Kritosaurini Lapparent & Lavocat, 1955
Kelumapusaura machi gen. et sp. nov.
Diagnosis. Kelumapusaura machi is diagnosed on the basis of the following unique combination of characters (autapomorphies marked with an asterisk): a shallow maxilla when compared with the dorsoventral height of the dentary; maxilla with a dorsoventrally low medialsurface dorsal to the medial row of foramina; maxilla with a groove forming a constriction on the anteroventral process; maxilla with a posterodorsal margin of the lateral surface forming a thick ridge that houses the palatine and pterygoid processes; postorbital with short to absent medial process on the skull roof; dentary symphysis with anteriorly oriented sub-triangular processes, ventrally delimited by a deep groove on its anterior end, resulting in a bilobate outline in lateral view; anterior-end of the dentary with a crescent-shaped concavity on its lateral surface; first sacral with anterior articular sur-faces strongly anterodorsally facing and obliquely oriented; scapula with a longitudinal groove dorsal to the acromial process; proportionally narrow scapular neck, being 0.5 times the dorsoventral length of the proximal-end; and scapula with a nearly straight (or weakly arched) scapular blade.
Etymology. The root of the generic name, ‘Kelumapu’, means ‘red earth’ in the Mapudungun language. The specific name ‘machi’ refers to the shaman of the Mapuche people.
Huallasaurus gen. nov.
Etymology. The generic name ‘Hualla’ means ‘duck’ inthe Mapudungun language.
Type and only included species. Huallasaurus australis comb. nov.
Sebastián Rozadilla, Federico Brissón-Egli, Federico Lisandro Agnolín, Alexis Mauro Aranciaga-Rolando and Fernando Emilio Novas. 2022. A New Hadrosaurid (Dinosauria: Ornithischia) from the Late Cretaceous of northern Patagonia and the Radiation of South American Hadrosaurids. Journal of Systematic Palaeontology. DOI: 10.1080/14772019.2021.2020917
