Around 20 million years ago, giant ocean worms might have burrowed into the seafloor and burst forth like the space slug from Star Wars to ambush unwary fish.
Ancient underground burrows left by these animals appear in rocks from coastal Taiwan, scientists report January 21 in Scientific Reports The diggers may have been analogs of contemporary bobbit worms ( Eunice aphroditois), known for burying themselves in sand to surprise and strike their prey.
The burrows are trace fossils– evidence of animal activity protected in the geologic record ( SN: 6/15/14) such as footprints ( SN: 4/27/20) and even fossilized poop ( SN: 9/21/17). These recently reported fossils were very first spotted in 2013 at Taiwan’s Badouzi promontory by paleontologist Masakazu Nara of Kochi University in Japan. More turned up later on amid the transcendent rock structures of Yehliu geopark, a popular tourist destination that was once a shallow ocean ecosystem 20 million to 22 million years earlier.
From 319 fossil specimens, the group was able to rebuild the burrows. The burrows were about 2 meters long and 2 to 3 centimeters wide.
” Compared to other trace fossils, which are usually only a few tens of centimeters long, this trace fossil was huge,” states Yu-Yen Pan, a geologist at Simon Fraser University in Burnaby, Canada. She called the trace fossil Pennichnus formosae, integrating the Latin words for feather, footprint and beautiful.
The tunnels were most likely dug by some type of huge worm, the researchers conclude, due to the fact that they lacked the trademark pellets lining crustacean tunnels and had smoother lining than bivalve tunnels. Iron deposits along the inside recommend the digger should have been long and slim and used mucous to reinforce the walls. Funneling at the top of the burrow also indicates the ancient worm emerging from its hideout, pulling back and then reconstructing the leading sections over and over once again.
” These [funnels] recommend that the worm repeatedly dragged its victim down into the sediment,” states research study coauthor Ludvig Löwemark, a geoscientist at National Taiwan University in Taipei.
These hunting strategies follow those of modern-day bobbit worms, which hide their 3-meter-long bodies in sand and surge forth to grab unwary prey with scissorlike teeth. While the earliest evidence of bobbit worms comes from the early Paleozoic Era, around 400 million years earlier, how or if the ancient worms relate to bobbit worms is unknown.
Because the worms that lived in these ancient tunnels were invertebrates, they didn’t have skeletons to leave behind in the fossil record. If soft tissue or teeth from bobbit worms were found maintained inside a burrow, that would confirm that these animals were living in the area 20 million years earlier.
” It is generally an obstacle to link fossil traces to specific trace makers,” states David Rudkin, an invertebrate paleontologist at the Royal Ontario Museum in Toronto, who was not involved with this study. Still, Rudkin thinks that the case for ancient bobbit worms hiding in these burrows is encouraging.
If ancient bobbit worms did terrorize the seafloor at that time, their burrows are an unusual example of invertebrates hunting vertebrates– normally it’s the other way around. Their existence also makes the local community more complex than formerly believed, states Löwemark. “There was certainly a whole lot more going on at the seafloor 20 million years earlier than one would envision when seeing these sandstones,” he states.
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