360 Million Year Old Fish Nursery Found in Namur




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Reconstruction of the placoderm nursery: young placoderms in shallow waters (above), adult animals in deeper waters (below). (Image: Justine Jacquot-Hameon, MNHN)
360 Million Year Old Fish Nursery Found in Namur
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Reinout Verbeke

Palaeontologists have found 360 million year old placoderms, the oldest known jawed vertebrates, in the quarry of Strud, close to Namur. They mostly found young animals, which could be an indication that it was a nursery or spawning place.

Placoderms are the oldest known jawed vertebrates. They originated in the Silurian (430 million years ago) and lived until the late Devonian (360 million years ago). Their head and trunk were covered with armours of bony plates, the rest was scaled or naked. Placoderms were the first fish that developed 'teeth'.

Palaeontologists Sebastien Olive (RBINS) and colleagues could ascribe fossils excavated between 2004 and 2015 in Strud to the placoderm species Grossilepis rikiki, Turrisaspis strudensis and Phyllolepis undulata. “Based on the size and on morphological characters, we can tell that they were all young animals”, Olive says, “so it was probably a place where eggs were laid or the animals gave live birth. The adult animals most likely lived nearby.”

360 million years ago, Strud was located in an alluvial plain. The calm, shallow water was the ideal spot for fish eggs and larvae to develop. The dense, hard and often spiny vegetation, of which traces were also found, could have protected them against predators. The placoderms of Strud belong to different species, so the nursery was shared. Strud provides the earliest proof of such a shared spawning place in the history of vertebrates.

The findings are reported in the journal PLOS ONE. The quarry of Strud also provided an insect fossil of the same age, Strudiella devonica, which is one of the oldest insects ever discovered, and also one of the oldest tetrapods.



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