RICERCA ITALIANA     

The Triassic Vertebrates from the Western Tethys and their paleogeographic and biostratigraphical implications

Università degli Studi di Milano

Abstract

The succession of marine vertebrate faunas (fishes and aquatic reptiles) during the entire Triassic is revealing itself as particularly rich of evolutionary events which will influence the rest of the Mesozoic. Evidences of these phases are known from two small areas nd partially complimentary to each other, the Calcareous Alps and the Southern China, that can be ascribed to the same bioprovince. Concerning the evolution of marine vertebrates it is very rare to be enabled to have such a highly detailed record linked to the exceptional repeating of ideal conditions for preservations of the vertebrates in coastal environments, usually the richest in life.
The goal of our program is to contribute to a better understanding of the timing, the pathways and the environmental conditions that controlled the subsequent radiations which led to a quick succession of faunal assemblages, characterized by an high biodiversity and wide geographic distribution.
This research team, at present the only one in Italy which works on Mesozoic Vertebrates on a constant and systematic way, can give an essential contribute t the following key areas
1) Evolutionary events: timing and recostruction of main radiations
2) Biodiversity:palaeontological record in the littoral domain concerning mainly fishes and reptiles (included terrestrial reptiles of the surrounding emerged lands)
3) Paleobiogeography: Thethyan bioprovince and its relationships with the Pacific >>>

Principal Investigator

Andrea TINTORI Università degli Studi di MILANO

Research Objectives

The successions of marine vertebrate faunas (fishes and aquatic reptiles) during the whole Triassic is becoming particularly rich of evolutionary events which will have influence on the entire Mesozoic. Evidences of these evolutionary phases are known from two restricted areas partially complementary to each other: the Southern Calcareous Alps and Southern China, which can be ascribed to the same bioprovince. It is seldom possible to have access to such detailed documentation about the evolution of marine vertebrates, due to the exceptional repeating of ideal conditions for preservation of vertebrates in coastal environments, usually the richest in life forms. The goal of our program is to contribute to a better understanding of the timing, the pathways and the environmental conditions that controlled the subsequent radiations which led to a quick succession of faunal assemblages, characterized by an high biodiversity and wide geographic distribution.
This research team, at present the only one in Italy which works on Mesozoic Vertebrates on a constant and systematic way, can give an essential contribute t the following key areas:

1) Evolutionary events: timing and recostruction of main radiations
2) Biodiversity:palaeontological record in the littoral domain concerning mainly fishes and reptiles (included terrestrial reptiles of the surrounding emerged lands)
3) Paleobiogeography: Thethyan bioprovince and its relationships with the >>>

First Results

1) Identification of different fish faunas in the reference succession from Monte San Giorgio (Middle Triassic) by completion of the study of the existing collections for stratigraphic purposes.
2) Check of the validity of some of these associations within the Lombardian basin.
3) Individuation of excavation sites in the Raibl-Cave del Predil area (Carnian)
4) Description of the small anisian fauna from the Braies Dolomites (which might reveal to be more primitive of the basal one from Monte san Giorgio thus quite useful to define the timing of the Triassic radiation)
5) Verification of the taxonomical identity of some Norian reptiles from Northern Italy with the isolated remains from British Fissure Infillings.
6) Realization of a character set, a matrix and a Phylogenetic tree of the drepanosaurids within diapsid reptiles
7) Provide a correct scientific support to local museums.

COSTS
In this first phase it is planned to concentrate most of the expenses for the paleontological excavations which will be assigned to specialized people external to the University under the direct guidance of the staff of the research unit of Milano. Part of what foreseen as external services will be used also for the preliminaru preparation of at least part of the material: such preparation is in fact mandatory to reach even a determination at genus level. The mission in foreign countries of the members of the research units for >>>

Timescale

24 months

National and international background

The Triassic period is a key moment in the evolution of tetrapods. Not only it was the time of the appearance of dinosaurs, pterosaurs, the flying reptiles, and of most of marine reptiles, but it witnessed also the appearance of most groups of extant terrestrial vertebrates, such as lissamphibians, turtles, lepidosaurs and advanced synapsids leading to mammals. In the Triassic seas took place a vast radiation of fish eating and durophagous reptiles (Rieppel & Hagdorn 1997). Among fishes, two radiation events took place, the second one, which occurred in the Norian, led to the replacement of Palaeozoic paleopterygians by the neopterygians; since then paleopterygian are restricted both in geographical distributionand echological niches (Tintori 1998a). The importance of that time interval for the evolution of vertebrates cannot be overestimated since it plays a basic role in trying to understand these evolutionary trends which represents the shift from paleozoic faunas to more modern ones. Southern Calcareous Alps have probably the world’s most continue fossiliferous successions for what concerns Triassic vertebrates, but in Italy their study has always been overlooked with respect to coeval invertebrate faunas. Indeed, Italian palaeontology took its first steps during the middle of the XIX century, by means of a few charismatic figures such as, in Milano, abbé Antonio Stoppani, Giuseppe Balsamo Crivelli, Emilio Cornalia. They brought to light some fossiliferous levels >>>