NEWS - Researchers show prehistoric sea cows were preyed upon by not just one predator, but two different carnivores, a crocodile and a shark, between 23 million and 11.6 million years ago or the Lower to Middle Miocene. The fossil descriptions reveal clues about the predation tactics of the ancient creatures and the broader food chain of the time.
Evidence of trophic interactions is not rare in the fossil record, but is mostly represented by fragmentary fossils that show ambiguous signs, making it often challenging to distinguish signs of active predation from scavenging events.
"Often when we observe predators in the wild, we find carcasses of prey that indicate their function as a food source for other animals as well, but the fossil record is much rarer," says Aldo Benites-Palomino, from the Department of Paleontology at Zurich.
"Our previous research has identified sperm whales being preyed upon by several shark species and this new study highlights the importance of sea cows in the food chain," says Benites-Palomino.
The extinct dugong sea cow of the genus Culebratherium was attacked by an ancient crocodile and then eaten by a tiger shark (Galeocerdo aduncus) in what is now north-western Venezuela. The discovery is one of the few records documenting multiple predatory actions on a single prey item.
The team of researchers from the University of Zurich, the Natural History Museum of Los Angeles County, Venezuelan institutes Museo Paleontológico de Urumaco and the Universidad Nacional Experimental Francisco de Miranda, said the discovery adds to evidence that the food chain millions of years ago had a similar pattern to today.
The sirenian fossil from the Agua Clara Formation retains crocodile bite marks across the skeleton. Shark bite marks can be seen throughout the skeleton and the teeth of G. aduncus are present. Deep tooth impacts concentrated on the muzzle of the sea cow suggest the crocodile first attempted to grab with its snout in an attempt to strangle.
Two further large incisions with initial circular impacts suggest the crocodile then dragged the sea cow, followed by tearing. Scratches and cuts on the fossil suggest the crocodile may have performed a “death roll” commonly seen in modern crocodiles.
Tiger shark teeth were found near the neck of the sea cow, with bite marks observed throughout the skeleton suggesting how the creature’s remains were later torn apart by this scavenger. Among the remains, they found a fragmented skeleton that included a partial skull and eighteen associated vertebrae.
“We first learned about the site through word of mouth from a local farmer who had seen some unusual stones. Curious, we decided to investigate,” said Marcelo Sanchez-Villagra, the Director of the Palaeontological Institute & Museum in Zurich.
"Initially, we were not familiar with the geology of the site, and the first fossil we excavated was a skull fragment. It took us some time to determine that the sea cow skull was quite strange in appearance.
By examining geological maps and sediments at the new site, the researchers determined the age of the rocks. Excavation of the partial skeleton required several visits to the site and managed to unearth most of the vertebrae. They organized a salvage operation using a full-case extraction technique.
"The operation took about seven hours with a team of five people. The subsequent preparations took several months, especially the painstaking work of preparing and restoring the skull elements," Sanchez-Villagra said.
"This area is known for evidence of predation by aquatic mammals and one of the factors that allowed us to observe this evidence was the excellent preservation of the cortical layer of the fossil associated with the fine sediment in which it was embedded," Sanchez-Villagra said.
Original research
Benites-Palomino, A., Aguirre-Fernández, G., Velez-Juarbe, J., Carrillo-Briceño, J. D., Sánchez, R., & Sánchez-Villagra, M. R. (2024). Trophic interactions of sharks and crocodylians with a sea cow (Sirenia) from the Miocene of Venezuela. Journal of Vertebrate Paleontology, DOI:10.1080/02724634.2024.2381505
Evidence of trophic interactions is not rare in the fossil record, but is mostly represented by fragmentary fossils that show ambiguous signs, making it often challenging to distinguish signs of active predation from scavenging events.
"Often when we observe predators in the wild, we find carcasses of prey that indicate their function as a food source for other animals as well, but the fossil record is much rarer," says Aldo Benites-Palomino, from the Department of Paleontology at Zurich.
"Our previous research has identified sperm whales being preyed upon by several shark species and this new study highlights the importance of sea cows in the food chain," says Benites-Palomino.
The extinct dugong sea cow of the genus Culebratherium was attacked by an ancient crocodile and then eaten by a tiger shark (Galeocerdo aduncus) in what is now north-western Venezuela. The discovery is one of the few records documenting multiple predatory actions on a single prey item.
The team of researchers from the University of Zurich, the Natural History Museum of Los Angeles County, Venezuelan institutes Museo Paleontológico de Urumaco and the Universidad Nacional Experimental Francisco de Miranda, said the discovery adds to evidence that the food chain millions of years ago had a similar pattern to today.
The sirenian fossil from the Agua Clara Formation retains crocodile bite marks across the skeleton. Shark bite marks can be seen throughout the skeleton and the teeth of G. aduncus are present. Deep tooth impacts concentrated on the muzzle of the sea cow suggest the crocodile first attempted to grab with its snout in an attempt to strangle.
Two further large incisions with initial circular impacts suggest the crocodile then dragged the sea cow, followed by tearing. Scratches and cuts on the fossil suggest the crocodile may have performed a “death roll” commonly seen in modern crocodiles.
Tiger shark teeth were found near the neck of the sea cow, with bite marks observed throughout the skeleton suggesting how the creature’s remains were later torn apart by this scavenger. Among the remains, they found a fragmented skeleton that included a partial skull and eighteen associated vertebrae.
“We first learned about the site through word of mouth from a local farmer who had seen some unusual stones. Curious, we decided to investigate,” said Marcelo Sanchez-Villagra, the Director of the Palaeontological Institute & Museum in Zurich.
"Initially, we were not familiar with the geology of the site, and the first fossil we excavated was a skull fragment. It took us some time to determine that the sea cow skull was quite strange in appearance.
By examining geological maps and sediments at the new site, the researchers determined the age of the rocks. Excavation of the partial skeleton required several visits to the site and managed to unearth most of the vertebrae. They organized a salvage operation using a full-case extraction technique.
"The operation took about seven hours with a team of five people. The subsequent preparations took several months, especially the painstaking work of preparing and restoring the skull elements," Sanchez-Villagra said.
"This area is known for evidence of predation by aquatic mammals and one of the factors that allowed us to observe this evidence was the excellent preservation of the cortical layer of the fossil associated with the fine sediment in which it was embedded," Sanchez-Villagra said.
Original research
Benites-Palomino, A., Aguirre-Fernández, G., Velez-Juarbe, J., Carrillo-Briceño, J. D., Sánchez, R., & Sánchez-Villagra, M. R. (2024). Trophic interactions of sharks and crocodylians with a sea cow (Sirenia) from the Miocene of Venezuela. Journal of Vertebrate Paleontology, DOI:10.1080/02724634.2024.2381505
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