A Rare Look into the Past
(January 24th, 2014) Do you like gardens? How about hanging gardens? If your answer to both questions is “yes”, Polish researchers might have something for you: a snapshot at a 380 million years old fossil garden.
What exactly happened on earth 500 or more million years ago is anybody’s guess. But fossils can give us a pretty good clue what ‘the land before time’ might have looked like. And recently, Polish researches made a "spectacular" fossil find in Morocco. Their study reports on a rare fossil community composed of miscellaneous species including cnidarians, crinoids, sponges, and microbes. All these critters lived more than 300 millions of years ago, in a submarine cavity sometime in the Middle Devonian.
When it comes to fossils, finding several species together in one place, resembling their natural positions while alive, is a lucky strike – that’s according to Michal Jakubowicz, Blazej Berkowski and Zdzislaw Belka from the Faculty of Geographical and Geological Sciences at Adam Mickiewicz University in Poznan, Poland, who conducted the study.
The rarity (and value) of this discovery comes from the unlikeliness of two events. First, a marine cavity that did not collapse after millions of years and second, animals that died in their natural, living positions. “The preservation of this paleoecosystem in the fossil record, as well as the fact that encrusters like sponges and bryozoans did not fall down after death is very unusual and enabled the development of the hanging gardens," says Michal.
It’s actually the corals that are to thank for this unusual finding. They form rigid skeletons that firmly attach to their substrate. Then, the new generation follows their elders’ example, “the corals could have served as attachment sites for following generations of encrusters for a long time, thus enabling development of these bizarre, intricate overgrowth patterns hanging downwards from the roofs,” explains Michal.
The discovery occurred after hard work and a bit of good luck, Michal recounts. “I was walking around the area, looking for some interesting fossils and sedimentary features, since it was my first time in the famous Hamar Laghdad ridge in Morocco and I was interested in nearly everything.” At that time, Michal, along with his co-authors, Blazej Berkowski and Zdzislaw Belka, was mapping the occurrence of Amplexus corals, a cylindrical-type coral common during the Devonian in the study area.
But then, Michal ran into something unexpected. “At some point, I walked across some bizarre assemblage of rugose corals that did not resemble the rather monotonous, monospecific "meadows" of the Amplexus type.” Their first idea was that everything was upside-down and that they were not only dealing with corals. “Despite many years of scientific research nothing like this had been previously reported from the area, so the discovery came as a real surprise to us,” notes Michal.
What they had found was a preserved ecosystem from millions of years ago. The “hanging garden” is the first of its kind, and was, at first sight, somewhat unbelievable. “Personally, my very thirst thought was ‘Can it be real?’ Could these corals really live in an upside-down position? But my scepticism did not last long. After getting back to Poznan and having a closer look at the studied material in polished slabs and thin sections, it turned out that, besides rugose corals, the community contained also crinoids, tabulate corals, sponges and microbes, altogether forming a spectacular, intricate "hanging garden" of mutually-overgrowing organisms, with a complexity that went far beyond our original expectations,” says Michal.
The Polish team is still working at Hamar Laghdad, and now they hope to hit gold again. “Hopefully, we will be able to find more examples of cryptic palaeoecosystems developed within the various carbonate build-ups in the area, and thus shed more light on the trends in Palaeozoic evolution of these unusual ecosystems,” Michal concludes.
Images: Jakubowicz et al.