Paleontologists have unearthed a 20-million-year-old fossilized skeleton of a species of the dugongid sirenian mammal Culebratherium with shark and crocodylian bite marks in northwestern Venezuela. The most conspicuous bite marks correspond to deep tooth impacts with dragging effect, concentrated on the animal’s snout. The researchers interpret these as the result of active predation because of the similarity with those produced when a crocodylian holds or rolls a prey. Additionally, shark bite marks can be observed throughout the Culebratherium’s skeleton, also evidenced by the finding of an isolated tiger shark (Galeocerdo aduncus) tooth associated with this skeleton.
Tiger sharks are starting to gather to take an easy piece of the large prey, as a crocodylian attacks the ancient dugongid sirenian mammal Culebratherium. Image credit: Jaime Bran Sarmiento.
“Our findings add to evidence that suggests the food chain, millions of years ago, behaved in a similar way to the present day,” said Dr. Aldo Benites-Palomino, a paleontologist at the University of Zurich.
“Today, often when we observe a predator in the wild, we find the carcass of prey which demonstrates its function as a food source for other animals too; but fossil records of this are rarer.”
“We have been unsure as to which animals would serve this purpose as a food source for multiple predators.”
“Our previous research has identified sperm whales scavenged by several shark species, and this new research highlights the importance of sea cows within the food chain.”
While evidence of food chain interactions are not scarce in the fossil record, they are mostly represented by fragmentary fossils exhibiting marks of ambiguous significance.
Differentiating between marks of active predation and scavenging events is therefore often challenging.
“Our findings constitute one of the few records documenting multiple predators over a single prey, and as such provide a glimpse of food chain networks in this region during the Miocene,” Dr. Benites-Palomino said.
The dugongid specimen studied by the team was collected from outcrops of the Agua Clara Formation, south of the city of Coro in Venezuela.
The fossil was closely related to a species of dugongid sirenian called Culebratherium alemani.
“We first learned about the site through word of mouth from a local farmer who had noticed some unusual “rocks”. Intrigued, we decided to investigate,” said University of Zurich’s Professor Marcelo Sanchez-Villagra.
“Initially, we were unfamiliar with the site’s geology, and the first fossils we unearthed were parts of skulls.”
“It took us some time to determine what they were — sea cow remains, which are quite peculiar in appearance.”
“By consulting geological maps and examining the sediments at the new locality, we were able to determine the age of the rocks in which the fossils were found.”
“The region is known for evidence of predation on aquatic mammals, and one factor that enabled us to observe such evidence was the excellent preservation of the fossil’s cortical layer, which is attributed to the fine sediments in which it was embedded.”
“After locating the fossil site, our team organized a paleontological rescue operation, employing extraction techniques with full casing protection.”
“The operation took about seven hours, with a team of five people working on the fossil.”
“The subsequent preparation took several months, especially the meticulous work of preparing and restoring the cranial elements.”
The team’s findings were published in the Journal of Verterbrate Paleontology.
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Aldo Benites-Palomino et al. Trophic interactions of sharks and crocodylians with a sea cow (Sirenia) from the Miocene of Venezuela. Journal of Vertebrate Paleontology, published online August 28, 2024; doi: 10.1080/02724634.2024.2381505