AsianScientist (Oct. 23, 2014) – A study of fossilized feces, more politely known as “coprolites”, has revealed the complex marine ecosystem present in what is modern day Japan. The study documenting these findings has been published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.
The mass extinction that took place at the Paleozoic-Mesozoic boundary (approximately 252 million years ago) killed around 95 percent of marine species, greatly simplifying the structure of the marine food chain. Past research has suggested that it took more than five million years for the marine ecosystem to fully recover from its collapse. However, marine animal fossils from the Early Triassic age—which came just after the mass extinction—are quite rare, which may have led researchers to underestimate the marine biodiversity at that time.
The present study focused not on rare body fossils such as bones but on the more commonly found coprolites. Using the fossilized poo, researchers were able to show that a complex food chain was already reestablished by the Early Triassic marine ecosystem.
Postdoctoral Fellow Dr. Yasuhisa Nakajima at the University of Bonn in Germany and graduate student Mr. Kentaro Izumi at the University of Tokyo found more than 60 coprolites from the Early Triassic marine stratum called the Osawa Formation in Minamisanriku Town, Miyagi Prefecture, northeastern Japan. The variety in coprolite size, ranging from a few milliliters to seven centimeters in maximum dimension, suggested that the producing animals also varied in body size.
Moreover, microstructural analysis using polarized light microscopy revealed that some of the coprolites included small bones from vertebrates. This evidence shows that a complex marine ecosystem with primary producers, primary consumers, small vertebrates and larger predators had fully recovered by five million years after the mass extinction at the Paleozoic-Mesozoic boundary.
As this study shows, Japanese geological fields such as Minamisanriku town are hotspots providing important evidence that could reveal the history of the ecosystem over the past several hundred millions of years. It is clear that further excavation in these high-potential fields should be encouraged.
The article can be found at: Nakajima and Izumi (2014) Coprolites from the Upper Osawa Formation (upper Spathian), Northeastern Japan: Evidence for Predation in a Marine Ecosystem 5 Myr after the End-Permian Mass Extinction.
Source: University of Tokyo.
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