Early Triassic Marine Biotic Recovery: The Predators' Perspective

Abstract

Examining the geological past of our planet allows us to study periods of severe climatic and biological crises and recoveries, biotic and abiotic ecosystem fluctuations, and faunal and floral turnovers through time. Furthermore, the recovery dynamics of large predators provide a key for evaluation of the pattern and tempo of ecosystem recovery because predators are interpreted to react most sensitively to environmental turbulences. The end-Permian mass extinction was the most severe crisis experienced by life on Earth, and the common paradigm persists that the biotic recovery from the extinction event was unusually slow and occurred in a step-wise manner, lasting up to eight to nine million years well into the early Middle Triassic (Anisian) in the oceans, and even longer in the terrestrial realm. Here we survey the global distribution and size spectra of Early Triassic and Anisian marine predatory vertebrates (fishes, amphibians and reptiles) to elucidate the height of trophic pyramids in the aftermath of the end-Permian event. The survey of body size was done by compiling maximum standard lengths for the bony fishes and some cartilaginous fishes, and total size (estimates) for the tetrapods. The distribution and size spectra of the latter are difficult to assess because of preservation artifacts and are thus mostly discussed qualitatively. The data nevertheless demonstrate that no significant size increase of predators is observable from the Early Triassic to the Anisian, as would be expected from the prolonged and stepwise trophic recovery model. The data further indicate that marine ecosystems characterized by multiple trophic levels existed from the earliest Early Triassic onwards. However, a major change in the taxonomic composition of predatory guilds occurred less than two million years after the end-Permian extinction event, in which a transition from fish/amphibian to fish/reptile-dominated higher trophic levels within ecosystems became apparent.

Marine Early Triassic Actinopterygii from Elko County (Nevada, USA): implications for the Smithian equatorial vertebrate eclipse

“…Specimens NMMNH P-66225 and NMMNH P-77117 from Nevada are both large individuals. With an estimated total length of 1.72-1.85 m, P-66225 had a size comparable to the birgeriids from the Smithian of Spitsbergen (Stensiö, 1921(Stensiö, , 1932Scheyer et al, 2014), the Middle Triassic of Monte San Giorgio and Besano (Swiss-Italian borderland ;Schwarz 1970;Romano and Brinkmann, 2009), the Middle-Late Triassic of China (Liu et al, 2006;Jiang et al, 2016;Sun et al, 2016), and possibly the Middle?-Late Triassic of Europe (B.? costata; Münster, 1839; Boni, 1937;Bürgin and Furrer, 1993).…”

“…One of the largest individuals of Early Triassic age is PIMUZ A/I 4301 from Spitsbergen, a few fragments of which were illustrated by Scheyer et al (2014). This specimen had an estimated total length of >2 m (skull without shoulder girdle length is~35 cm).…”

“…aldingeri; Stensiö, 1932); PIMUZ A/I 4301 (Birgeria sp. ; Scheyer et al, 2014); PIMUZ material of B. stensioei (as listed in Romano and Brinkmann, 2009); PIMUZ A/I 3900 (Saurichthys cf. elongatus; Romano et al, 2012); and PIMUZ A/I 4135, A/I 4144 (S. madagascariensis; Kogan and Romano, 2016a).…”

Coprolites of marine vertebrate predators from the Lower Triassic of southern Poland

“…First, not so long ago, it was assumed that marine predation was not intense during the Early-Middle Triassic (see Salamon et al, 2012, for a review). However, there is increasing evidence that multi-level trophic food webs with abundant predators had already appeared in the aftermath of the end-Permian extinction (Scheyer et al, 2014). Although these data suggested widespread innovations for durophagy during the early Mesozoic, the fossil record of predation from this crucial period was scarce (Nakajima and Izumi, 2014).…”

Taphonomy and palaeobiology of early Middle Triassic coprolites from the Luoping biota, southwest China: Implications for reconstruction of fossil food webs

“…These Spathian coprolites were likely produced by secondary consumers. The Polish Olenekian coprolites contain relatively abundant skeletal fragments including some vertebrate bones, and thus represent more diverse prey in the food chains, which is also reinforced by the presence of multi-trophic ecosystem indicated by coeval marine vertebrates (Scheyer et al, 2014). The food remains of the Polish coprolites, however, are dominated by invertebrate shell fragments with minor constituents of vertebrate bones of uncertain origin.…”