![]() This section attempts to trace the Ischigualastian LVF eastward to encompass Late Triassic tetrapod faunas of Africa and India. This correlation was the main subject of another contribution to this issue (Langer, 2005) and will not be discussed further herein. The faunal succession of the Ischigualasto sequence is more properly compared to that of the Late Triassic deposits of the Paraná Basin in south Brazil (Fig. 1A), and its thickness averages 600 m (650 m in the type area) though it ranges from 200 to 900 m in different parts of the Ischigualasto–Ischichuca depocenter of the Bermejo Basin ( Tracing the Ischigualastian throughout south Pangea This stratigraphic unit crops out in the Ischigualasto provincial park, San Juan and La Rioja provinces, NW Argentina (Fig. The term Ischigualastian (=‘Ischigualastense’) was coined by Bonaparte, 1966, Bonaparte, 1973 to designate a reptile age, primarily on the basis of the fossil fauna of the Ischigualasto Formation. Section snippets The Ischigualastian: Premises and definition By reassessing the taxonomic status and distribution of tetrapod taxa, this article defines an updated correlation basis for the Late Triassic of Pangea. However, the extension of these biochronologic units into south Pangea is based mainly on dubious records of index fossils, the taxonomic status of which are not clearly understood. This correlation contradicts tetrapod-based Late Triassic biochronologies that divide the Carnian epoch into two land vertebrate faunachrons, Otischalkian and Adamanian, on the basis of the succession of faunas in some North American continental sequences. On the basis of faunal similarities, the Ischigualastian can be traced throughout south Pangea to encompass the fossil assemblages of the Hyperodapedon assemblage zone, Santa Maria Formation, south Brazil the Pebbly Arkose Formation, Zimbabwe and the Lower Maleri Formation, India. Fossil taxa that characterize the Ischigualastian include Hyperodapedon, the cynodont Exaeretodon, the aetosaur Aetosauroides, and herrerasaurid dinosaurs. The first appearance data of the rhynchosaur Hyperodapedon and the dicynodont Jachaleria define its lower and upper limits, respectively. 121.5 mm).The Ischigualastian represents a key land vertebrate faunachron for the correlation of Late Triassic terrestrial deposits worldwide, based on the abundant and diverse tetrapod fauna of the Ischigualasto Formation, NW Argentina. The post-canine number decreases from six plus one erupting in a small individual (preorbitai length: 82.9 mm) to five plus one erupting in the largest specimen (pI. Additionally, the number of postcanines seems to be ontogenetically less variable in the Brazilian species. Small differences in the posterior projections of the jugal onto the squamosal and in the shape of prefrontals distinguish the two species. The new species is most similar to Exaeretodon frenguellii from the Ischigualasto Formation of Argentina. These crests are interpreted as related to the origin of the posterior pterygoid muscle representing the first evidence, among non-mammalian cynodonts to mammals transition, of the attachment of this muscle onto the prootic bone. ![]() The presence of prootic crests in the extensive lateral flange, anterior to the fenestra ovalis, is a noteworthy basicranial trait, unique to this new taxon among non-mammalian cynodonts. The excellent preservation of one specimen reveals new cranial information about the genus. from the Santa Maria Formation, Rio Grande do Sul State, Brazil is described. The skull of the traversodontid cynodont Exaeretodon riograndensis, sp.
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