A new Late Triasssic phytogeographical scenario in westernmost Gondwana

Abstract

Floral provincialism within the Southern Hemisphere during the Late Triassic (230 Ma) is characterized by the Ipswich and Onslow provinces, recognized originally in eastern Gondwana. However, new palynological assemblages from the Ischigualasto Formation, northwestern Argentina (231-225 Ma), change the phytogeographic interpretation for the Carnian-Norian in the westernmost Gondwana, which was previously considered part of the southern floral Ipswich province. Here we show the presence of diagnostic Euramerican species within assemblages dominated by Gondwanan taxa that allows us to refer the palynofloras to the Onslow province. Our new data extend the Onslow floral belt, previously recognized from the western edge of Tethys to Timor, to the western margin of South America. This has implications for palaeophytogeography, palaeoclimate reconstructions and the palaeoecology of a Triassic ecosystem, which has yielded significant vertebrate remains and is regarded important in the early evolution of groups such as the Dinosauria.

New Specimen Sheds Light on the Anatomy and Taxonomy of the Early Late Triassic Dinosauriforms from the Chañares Formation, NW Argentina

“…This palaeoenvironment was dominated by a palaeovegetation similar to other typical Gondwanan Triassic floras— Dicroidium Flora—with ferns, lycopsids, and bryophytes growing near ephemeral water bodies; lignophytes represented the arboreal stratum, with umkomasialeans as the dominant elements; and conifers in minor proportions (Perez Loinaze et al ., ). This palaeofloristic assemblage was interpreted as a “transitional palynoflora,” with shared and mixed elements with the Onslow Microflora and Ipswich Subprovince, both developed in middle warmer climates and cool temperate climates of Gondwana, respectively (Césari and Colombi, ; Perez Loinaze et al ., ). Beyond this floristic association, the dicynodont coprolites also preserve diverse arthropod and fungal remains (Perez Loinaze et al ., ) that occur in the aftermath of a major evolutionary radiation that resulted in the establishment of modern insect groups during the Middle Triassic (Misof et al ., ; Van Eldijk et al ., ).…”

Mass extinctions drove increased global faunal cosmopolitanism on the supercontinent Pangaea

“…This would corroborate previous work, suggesting the evolution of a distinct fauna, that includes massopodan sauropodomorphs, ornithischians, basal saurischians, and prozostrodontian cynodonts as relatively common taxa in South America and Africa during the Late Triassic 11 . The occurrences of guaibasaurids 25 and floral similarities 26 , 27 provide some links between South American communities and the upper Maleri Formation of India, although the latter assemblage remains relatively poorly-known and sampled. The Triassic–Jurassic mass extinction was a global event 19 and it is unclear why decoupling of biogeographic trends within Gondwana should occur.…”

First record of Ginkgo-related fertile organs (Hamshawvia, Stachyopitys) and leaves (Baiera, Sphenobaiera) in the Triassic of Brazil, Santa Maria formation

“…limits was recently revised (Dolby and Balme, 1976;Césari and Colombi, 2013). This proposal have support in the presence of heavily cutinized epidermis covered by numerous papillae, and deeply sunken stomata in the cuticle (Pott et al, 2007).…”