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Buatois & Mángano, 2016a

Ediacaran Ecosystems and the Dawn of Animals

Buatois, L. A., Mángano, M. G.
DOI
DOI10.1007/978-94-017-9600-2_2
Aasta2016
RaamatThe Trace-Fossil Record of Major Evolutionary Events. Vol. 1: Precambrian and Paleozoic
Toimetaja(d)Mángano, M. G., Buatois, L. A.
KirjastusSpringer Netherlands
Kirjastuse kohtDordrecht
Köide39
Leheküljed27-72
Tüüpartikkel kogumikus
Keelinglise
Id9377

Abstrakt

Ichnology may provide remarkable information for our understanding of Ediacaran paleobiology, illuminating aspects such as the earliest evidence of bilaterians and the nature of Ediacaran ecosystems. The possibility of animal trace fossils in pre-Ediacaran rocks is considered unlikely and, therefore, the target of ichnologic research has moved in recent years to Ediacaran strata that postdate the Gaskiers glaciation. Still, the earliest convincing evidence of bilaterian activity comes from the White Sea Assemblage (less than 560 Ma). Although earlier systematic compilations listed a wide variety of trace fossils for the Ediacaran, including complex trace fossils and scratch marks produced by arthropods, the present view is one of much more reduced global ichnodiversity and ichnodisparity. In fact, a critical reevaluation of the trace-fossil record indicates the presence of only seven categories of architectural designs: simple horizontal trails, passively filled horizontal burrows, actively filled (massive) horizontal burrows, plug-shaped burrows, oval-shaped impressions, rasping traces, and horizontal burrows with horizontal to vertical branches. Microbial mats were critical components in Ediacaran ecosystems and benthic communities developed in direct association with resistant matgrounds. Within this framework, various categories of organisms–microbial mats interactions can be recognized. Mat encrusters and mat stickers are essentially represented by body fossils, but trace-fossil data is key to decipher mat scratchers (organisms rasping on the microbial mats), mat digesters (organisms able to feed from direct external digestion of the mat), mat grazers (organisms browsing through the microbial mat), and undermat miners (organisms that constructed tunnels below the mat). Although integration of ichnologic and sedimentologic information allows discriminating between shallow- and deep-marine benthic communities, limited beta ichnodiversity implies substantial niche overlap during the Ediacaran. Ediacaran sediments displayed almost invariably no bioturbation (BI 0) to very locally sparse bioturbation (BI 1) at the most, with very limited to nonexistent infaunal tiering. Critical evaluation of the available information places the earliest evidence of complex behavior in the treptichnids recorded by the end of the Ediacaran, certainly representing the prelude of the dramatic increase in complexity evidenced by the Cambrian explosion.

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