Vertebrate succession in the Ischigualasto Formation

Abstract

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New dinosaur remains from the Late Triassic of southern Brazil (Candelária Sequence, Hyperodapedon Assemblage Zone)

“…In contrast, rhynchosaurs constitute only ca 10% of the sampled vertebrate fossils at 'Sítio Janner'; Exaeretodon comprises about 50% of the occurrences . This is similar to the upper portion of the Ischigualasto Formation, where Exaeretodon is the most abundant taxon , Martínez et al 2011, 2013a, and prompts subdivision of the Brazilian Hyperodapedon Assemblage Zone into two distinct biostratigraphic units, as previously suggested by .…”

The femoral anatomy of Pampadromaeus barberenai based on a new specimen from the Upper Triassic of Brazil

“…The overlaying subdivision of the Hyperodapedon AZ is characterized by a substantial decrease of Hyperodapedon records and the overwhelming occurrence of Exaeretodon Historical Biology 7 ). In the Ischigualasto Formation, this event was quantified by Martínez et al (2012b) with a decrease that eventually resulted in the disappearance of Hyperodapedon ( ¼ Schaphonyx) from lower to upper levels of the Argentinean unit. As previously mentioned, the holotype of Pampadromaeus barberenai was exhumed from the reddish mudstones of the 'Janner' outcrop, the same outcrop from where CAPPA/UFSM 0027 was recovered.…”

Age constraints on the dispersal of dinosaurs in the Late Triassic from magnetochronology of the Los Colorados Formation (Argentina)

“…Faunal dispersal across the Pangean supercontinent in the development of more cosmopolitan vertebrate assemblages later in the Norian may have been in response to reduced contrasts between climate zones and lowered barriers resulting from decreasing atmospheric pCO 2 levels. magnetostratigraphy | paleolatitude | La Esquina | Adamanian T he leading candidate for the oldest known occurrence of dinosaurs is the tetrapod assemblage of the Ischigualasto Formation of Argentina (1)(2)(3)(4) where a preferred recalculated 40 Ar/ 39 Ar date of 231.4 ± 0.3 Ma (1σ analytical uncertainty as reported) (5) on the Herr Toba tuff from near the base of the formation points to a Carnian age for the dinosaur-bearing fauna. However, two recent studies of high-precision U-Pb zircon dates from the Chinle Formation in the American Southwest, practically the only other Late Triassic strata with radioisotopic age constraints on vertebrate assemblages, arrive at very different interpretations of the timing of the dispersal of dinosaurs depending on the accepted degree of total uncertainty for the Ischigualasto 40 Ar/ 39 Ar data.…”