A swimming school of fish fossilized in real time
Published: 18 July 2019 (GMT+10)
A limestone shale slab from the Green River Formation, USA, has incredibly ‘captured’ a mass of 257 fish swimming together in a school.1 The fish, each just under 1 in (2.5 cm) long, belong to an extinct species, Erismatopterus levatus. Just before being fossilised they were swimming in the same direction. Swimming together in a school is a dynamic process and this slab amazingly preserves, in ‘freeze frame’ as it were, this coordinated collective motion. Such discoveries are rare. As pointed out in the New York Times, “It’s difficult, for instance, to find evidence of schooling fish in the fossil record. You need just the right circumstances to fossilize something like a school of fish in place within a rock. Then, that rock has to survive intact long enough for a paleontologist to discover it and study it”.2
The right circumstances?
While the study did not conclusively give an answer as to how the fish were fossilized the authors suggested that a, “Rapid fixation of the fish shoal might be possible by sand dune collapse on shallow water, which can produce a bed in only seconds or minutes”.1 It is clear that they recognised that the fish school’s fossilisation absolutely required a rapid process. Roy Plotnick, a paleontologist at the University of Illinois at Chicago said, “I’ve never seen this kind of preservation. I can’t picture a three-dimensional school of fish sinking to the bottom and maintaining all their relative positions. That makes no sense to me”.2
Yet people who don’t want the uncomfortable implications of rapid processes entombing the fish have been forced to come up with similar non-sensical ideas. For example one commenter stated, “More than likely what happened is the fish got trapped in an isolated pool as the waters receded. Then, as the pool dried out, the fish all died. What wasn’t taken by predators was covered by layers of dirt and mud over the millenia [sic] and, thusly, this fossil”.3 Of course the problems with this suggestion are fairly clear from even a cursory view of the fossil slab. There’s no way that the fish would be facing the same direction in a tight oblong school formation (see the figure) if they were slowly asphyxiating in a pool. Instead they would have been flopping themselves about to try and remain in the dampest part of the puddle, and there would likely be signs of predation too.
Implications of motion
The paper demonstrated that immediately before the oblong shaped school was entombed in lime rich sediment they were actively swimming together. From measuring the fishes’ positions and orientations the team were able to show they were following the rules of attraction and repulsion in relation to the other fish around them (to avoid bumping into each other) that schools abide by today. This incredible group self-organisation, swimming together in the same direction in one fluid formation, is called schooling (as opposed to shoaling when fish swim in the same general area but in different directions). Due to the mesmerising beauty of the schooling movement (especially in bait balls4), just like the murmurations of birds flying together, it is often featured in nature documentaries. The oblong shape of the school also matches extant fish schools and, “is thought to protect against ambush predators by reducing the frontal area, where these predators tend to attack”.1,5 It is the capturing of this motion, a snapshot in time, that means the fossil was formed quickly, and thus by implication, the rock also.
The scientific team also highlighted a number of other fascinating examples of what they called “frozen behaviours” in fossils: “examples include fighting dinosaurs, queueing trilobites and insects in copulation. These fossils are assumed to result from rapid burial, which preserves individual positions during interactions”. Yes indeed, but this is completely contrary to the uniformitarian ‘slow-n-gradual’ paradigm that pervades school textbooks and pop-science programmes.
Quick forming fossils contained inside rapidly formed layers of sedimentary rock, such as the ones listed above and the many other examples on this website, consistently point to one thing: the sedimentary rocks layers that we see all around the world are not millions of years old.
While evolutionary paleontologists see the Green River Formation as a continuous record of six million years’ worth of slow geological processes, these fossilized fish captured mid-swim require a different interpretation—one which bears eloquent testimony to flood conditions. The origin of the Green River Formation is debated by Flood Geologists, but whether it was created during the Noahic Flood or in an energetic hydraulic post-Flood event, they all agree that millions of years was not necessary for its formation. This breathtakingly well-preserved body of fish only serves to school us that the rocks and fossils around us were formed rapidly and fit perfectly well within the biblical time frame of only 6,000 years.
References and notes
- Mizumoto, N., Miyata, S., & Pratt, S.C., Inferring collective behaviours from a fossilized fish shoal, Proc. R. Soc. B 286:20190891, 2019 | doi:10.1098/rspb.2019.0891. Return to text.
- Lucas, J., A school of fish, captured in a fossil, nytimes.com, 29 May 2019. Return to text.
- Kielas-Fecyk, B., comment section in: Wilke, C., A 50-million-year-old fossil captures a swimming school of fish, sciencenews.org, 28 May 2019. Return to text.
- For example, see photo and brief description at the Smithsonian Institute’s website: ocean.si.edu/ocean-life/fish/bait-ball; accessed 5 June 2016. Return to text.
- Hemelrijk, C.K. & Hildenbrandt, H., Schools of fish and flocks of birds: their shape and internal structure by self-organisation, Interface Focus 2(6):726-737, 2012 | doi:10.1098/rsfs.2012.0025. Return to text.