Shark-on-shark attacks have been documented in truly spectacular fossils

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Due to the rarity of shark cartilage fossilizing, it is extremely difficult to find these specimens.

According to a recent study based on four rare relics, sharks pursued a wide variety of prey during the megalodon era, including other sharks.

Researchers and amateur fossil hunters have unearthed four ancient shark vertebrae. All four vertebrae have bite scars, and two still have pointy shark teeth. According to the experts, shark skeletons are constructed of cartilage, which does not fossilize effectively. These discoveries are remarkable.

Discovery shows that millions of years ago, sharks off the East Coast of the United States ate other sharks. Even though sharks have been preying on each other for millions of years, these interactions are rarely reported because of the poor preservation potential of cartilage, study co-researcher Victor Perez, an assistant curator of paleontology at Calvert Marine Museum in Solomons, Maryland, tells Live Science in an email.

Since the 1960s, scientists have been aware of shark cannibalism and shark-on-shark predation. If you've ever seen a lamniform shark fetus eat its siblings in the womb, you've witnessed this behavior in living sharks like the goblin, the megamouth, basking, the mako, and even the great white, experts say.

According to two studies, ancient sharks have left bite marks on numerous fossilized animals, including marine mammals, ray-finned fish, and reptiles — even flying reptiles known as pterosaurs, which existed around the time of the dinosaurs. On the other hand, evidence of ancient shark-on-shark combat is rather scarce. During the Devonian period (419.2 million to 358.9 million years ago), the Cladoselache shark ate another shark, whose petrified remains were found in its digestive tract.

Three shark fossils recovered in Calvert Cliffs on Maryland's coast between 2002 and 2016 were examined in the current study, as was a fourth unearthed in an old phosphate mine in North Carolina in the 1980s by researchers. Todus megalodon (the world's largest shark) was roaming the oceans throughout the Neogene period (23,03 million to 2,58 million years ago), and all of the fossils found here originate from that period. (These four attacks, however, were not carried out by megalodon.)

According to Perez, the cartilage in sharks is a soft structure made up of microscopic hexagonal prisms that swiftly decompose after death. It's rare enough to find cartilaginous shark bones, but finding bite evidence on those bones is remarkable, according to him. "This predatory connection needs to be preserved for millions of years and recovered by someone who realizes its significance under rare conditions."

So, how did these four fossils manage to withstand the test of time? All of them are centra, which are the spinal column's vertebrae. It's more densely calcified cartilage in the central regions of the skeleton, making them more stable than other skeleton portions. According to the research team, these four fossils are the earliest examples of prehistoric shark centra bearing bite marks.

It's unclear whether these bites, classified as "trace fossils," were formed during an attack or if they were scavenged by an animal and preserved in the soil. Trace fossils include footprints, bite marks, and even pet waste. However, one Maryland fossil shows healing indications, indicating that the shark survived the encounter.

According to a bone examination, chondrichthyans are a class of sharks that includes 282 species still living today, including bull, tiger, and hammerhead sharks. Perez added, "We can narrow it down to certain possible perpetrators, but we can't identify the precise species engaged in these encounters."

In the family Carcharhinidae, the fossil with two implanted shark teeth belongs to either Carcharhinus or Negaprion, according to the scientists that studied it. According to researchers, the teeth might also be from a Carcharhinus or Negaprion shark.

Carcharhinidae appears to represent the family of another Maryland specimen, which had bite marks from many attackers, including chondrichthyan sharks, lamnid sharks, and bony fish. The tiger shark is the only species of Galeocerdo, which is thought to be represented by the third specimen found in Maryland (G. cuvier).

Centra was bitten "quite hard," according to the researchers in their study. The specimens had embedded teeth and a gouge mark on them.

At the Calvert Marine Museum, two fossils have been put on display as part of a new exhibit, "There are sharks here! The time has come to sunk your teeth into this!" Acta Palaeontologica Polonica published the paper online on December 7, 2021.

Reference : https://www.livescience.com/rare-shark-fossils-reveal-ancient-attacks

Image source : https://pixabay.com/id/photos/pemandangan-laut-sydney-australia-2397917/

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