Think of it as Noah’s bark. From New Scientist:
We have long known of preserved logs up to 14 metres long from the Jurassic period 200 to 145 million years ago. The logs are covered in crinoids, an animal related to starfish that has a central body with many long feathery arms. The logs also carry oysters.Michael Marshall, “Huge mega-rafts carried dinosaur-era animals on round-the-world trips” at New Scientist
From the Daily Mail:
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. Yuan Ren, “Enormous floating 45-foot long rafts carried feathery sea creatures to all corners of the globe during the era of the dinosaurs” at Daily Mail:
Both based on a recent open-access paper:
Abstract:Pseudoplanktonic crinoid megaraft colonies are an enigma of the Jurassic. They are among the largest in-situ invertebrate accumulations ever to exist in the Phanerozoic fossil record. These megaraft colonies and are thought to have developed as floating filter-feeding communities due to an exceptionally rich relatively predator free oceanic niche, high in the water column enabling them to reach high densities on these log rafts. However, this pseudoplanktonic hypothesis has never actually been quantitatively tested and some researchers have cast doubt that this mode of life was even possible. The ecological structure of the crinoid colony is resolved using spatial point process techniques and its longevity using moisture diffusion models. Using spatial analysis we found that the crinoids would have trailed preferentially positioned at the back of migrating structures in the regions of least resistance, consistent with a floating, not benthic ecology. Additionally, 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. We have found that these crinoid colonies studied could have existed for greater than 10 years, even up to 20 years exceeding the life expectancy of modern documented megaraft systems with implications for the role of modern raft communities in the biotic colonisation of oceanic islands and intercontinental dispersal of marine and terrestrial species.
Significance statement Transoceanic rafting is the principle mechanism for the biotic colonisation of oceanic island ecosystems. However, no historic records exist of how long such biotic systems lasted. Here, we use a deep-time example from the Early Jurassic to test the viability of these pseudoplanktonic systems, resolving for the first time whether these systems were truly free floating planktonic and viable for long enough to allow its inhabitants to grow to maturity. Using spatial methods we show that these colonies have a comparable structure to modern marine pesudoplankton on maritime structures, whilst the application of methods normally used in commercial logging is used to demonstrate the viability of the system which was capable of lasting up to 20 years. – Aaron W. Hunter, David Casenovec, Emily G. Mitchell, and Celia Mayers, Reconstructing the ecology of a Jurassic pseudoplanktonic megaraft colony. Short title: A Jurassic megaraft ecosystem (open access) More.
It might explain some things. Let’s see what holes it plugs.
See also: Latest: Rodents Who Floated Across The Atlantic On Vegetation Rafts (2011)
Pumice rafts “floating laboratories” for early life.
Crocodiles swam to North America?
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