| 1. |
- Nesbitt, Sterling J., et al.
(författare)
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The earliest bird-line archosaurs and the assembly of the dinosaur body plan
- 2017
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Ingår i: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 544:7651, s. 484-
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Tidskriftsartikel (refereegranskat)abstract
- The relationship between dinosaurs and other reptiles is well established(1-4), but the sequence of acquisition of dinosaurian features has been obscured by the scarcity of fossils with transitional morphologies. The closest extinct relatives of dinosaurs either have highly derived morphologies(5-7) or are known from poorly preserved(8,9) or incomplete material(10,11). Here we describe one of the stratigraphically lowest and phylogenetically earliest members of the avian stem lineage (Avemetatarsalia), Teleocrater rhadinus gen. et sp. nov., from the Middle Triassic epoch. The anatomy of T. rhadinus provides key information that unites several enigmatic taxa from across Pangaea into a previously unrecognized clade, Aphanosauria. This clade is the sister taxon of Ornithodira (pterosaurs and birds) and shortens the ghost lineage inferred at the base of Avemetatarsalia. We demonstrate that several anatomical features long thought to characterize Dinosauria and dinosauriforms evolved much earlier, soon after the bird-crocodylian split, and that the earliest avemetatarsalians retained the crocodylian-like ankle morphology and hindlimb proportions of stem archosaurs and early pseudosuchians. Early avemetatarsalians were substantially more species-rich, widely geographically distributed and morphologically diverse than previously recognized. Moreover, several early dinosauromorphs that were previously used as models to understand dinosaur origins may represent specialized forms rather than the ancestral avemetatarsalian morphology.
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| 2. |
- Novas, Fernando E., et al.
(författare)
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A new large pterosaur from the Late Cretaceous of Patagonia
- 2012
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Ingår i: Journal of Vertebrate Paleontology. - UK : Informa UK Limited. - 0272-4634 .- 1937-2809. ; 32:6, s. 1447-1452
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Tidskriftsartikel (refereegranskat)abstract
- Here, we expand the meager record of Late Cretaceous South American pterosaurs with the description of a partial rostrum belonging to a large azhdarchid pterodactyloid. The specimen was collected close to the Bajo de Arriagada locality, corresponding to the uppermost Cretaceous Allen Formation of Argentina, around 80 km northwest of the well-sampled Bajo de Santa Rosa locality. The specimen represents the first unambiguous evidence of an azhdarchid pterosaur from South America. This specimen represents a new genus and species, Aerotitan sudamericanus, which is diagnosed based ona unique combination of characters, including one autapomorphy,and represents one of the largest known South Americanpterosaurs. The fossil here described resulted from a joint Argentine-Swedish paleontological expedition to Patagonia.
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