Enormous floating 45-foot long rafts carried feathery sea creatures to all corners of the globe during the era of the dinosaurs
- The rafts were covered in a light feathery tentacle creature known as crinoids
- They were a rich colony of sea creatures which floated for up to 20 years
- Scientists used mathematical modelling and fossil mapping to study them
- The logs did not collapse as previously thought as the structures grew denser
Floating logs up to 45 foot (15 metres) long ferried feathery sea creatures around the world’s oceans for decades, researcher has found.
These ‘megarafts’ of feeding oceanic species are some the largest micro habitats seen in the fossil record from the Jurassic era.
They became popular colonies of marine life as the structures were high in the water and provided a safe haven to escape predators.
The latest study also confirmed that the logs did not collapse as they became denser, as was previously thought, with some existing for up to 20 years.
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Floating logs that ferried rich communities of sea creatures around the oceans were able to float for decades, the latest research has found. The picture shows a reconstruction of marine life from the Jurassic period
The latest study from Cambridge academics focused on megacrafts colonies, which were covered in feathery creatures with tentacles known as crinoids – or sea lilies.
Related invertebrates similar to starfish, sea urchins and sea cucumbers were also thought to be present.
These creatures were prevalent in marine life and formed a major part of the Jurassic shallow ocean environments and covered the rafts that were studied.
Using a giant fossil specimen from Germany known as the giant ‘Hauff Specimen’, researchers mapped the spatial position of crinoids in one of the largest and best-preserved Early Jurassic floating wood examples known.
Using a giant fossil specimen (bottom left) from Germany known as the giant ‘Hauff Specimen’, researchers mapped the spatial position of crinoids (bottom right) in one of the largest and best-preserved Early Jurassic floating wood fossils (bottom left) known
Researchers found using mathematical and spatial modelling that these crinoids would have grown at the tail end of the structures in a way of ‘least resistance’ that would have allowed the raft to stay afloat in the water.
The study used different models of water distribution with various raft densities and sizes to see what would happen to the colony as it grew denser.
The researchers wrote in the report of the study: ‘These megaraft colonies and are thought to have developed as floating filter-feeding communities due to an exceptionally rich, relatively predator free oceanic niche,’ the reporters wrote in the study.
‘We found using a series of moisture diffusion models at different log densities and sizes that ecosystem collapse did not take place solely due to colonies becoming overladen as previously assumed.’
Reconstruction of the crinoid colony based on the a giant fossil specimen from Germany known as the giant ‘Hauff Specimen’ that was mapped in the current study. It shows the feathery crinoids on the right hand side of the long log that makes up the megaraft community
The Cambridge scientists found that these primarily crinoid-covered colonies could have existed for more than a decade, after using mathematical modelling mapping to observe how they floated and were inhabited.
While some of these structures could have existed a decade, some even lasted up to 20 years, which is longer than the record for these structures found in modern seas and oceans today.
The report is published in the Cold Spring Harbour Laboratory reprint server for Biology.
