The US National Park Service announced the identification of a new species of ancient shark, Clavusodens mcginnisi, discovered in Mammoth Cave National Park. The species name honors David McGinnis for his leadership in paleontological resource stewardship.
Clavusodens mcginnisi, or McGinnis's nail-tooth, was found fossilized in Mammoth Cave, the world's longest cave system. The fossilized teeth were discovered in the Ste. Genevieve Formation, a layer of limestone and shale formed on the floor of warm ocean reefs during the Middle Mississippian geological period.
The formation is estimated to be about 340 million years old and has yielded many prehistoric fish fossils. Mammoth Cave houses over 70 different species of ancient fish fossils, including Clavusodens mcginnisi identified from small fossilized teeth.
The newly identified shark had an estimated length of only 8 to 10 centimeters (3 to 4 inches). It belonged to a group of sharks known as obruchevodid petalodonts, or chipmunk sharks, because of their tiny size and unusual teeth.
The shark's back teeth had flat crowns and long bases resembling old iron nails, which contributed to its common name. The front teeth were more chisel-like, suggesting a diversified diet. Its posterior teeth were suitable for crushing prey such as crustaceans and small brachiopods, and it fed on crustaceans, small brachiopods, and worms on the seafloor.
"The fossil discoveries in Mammoth Cave continue to reveal a wealth of new information about ancient shark species," stated Superintendent Barclay Trimble, according to IFLScience. "Researchers and volunteers collected samples from the main Mammoth Cave system and from smaller isolated caves throughout the park that have provided new data on previously known ancient sharks and revealed several species that are brand new to science," he also said.
McGinnis is recognized for his commitment to the management of paleontological resources during a 39-year career, which began at Mammoth Cave National Park.
Obruchevodid petalodonts were "among the most specialized cartilaginous fishes during the Mississippian, potentially adapted to live in complex reef and reef-like habitats," the researchers noted.
Researchers suspect that Clavusodens mcginnisi may have lived in reef-like systems filled with marine invertebrates called crinoids, or sea lilies, that attached themselves to the sea floor like plants.
These fossils date back to 330.9 million to 323.2 million years ago. The rocks in Mammoth Cave have preserved marine sediment from the Carboniferous period (358.9 million to 298.9 million years ago), as the area once rested at the bottom of an old ocean.
Researchers have been documenting vertebrate fossils in Mammoth Cave since 2019. The work of documenting fossils in Mammoth Cave is challenging because of the cave's often cramped conditions and limited space to move equipment in and out. "Many of these sites have low ceilings requiring crawling for long distances on hands and knees, and at times belly crawling," the researchers wrote.
The discovery of Clavusodens mcginnisi is not the first time a new species of ancient shark has been found in the limestone of Mammoth Cave. In the previous year, paleontologists identified two new species: Troglocladodus trimblei and Glikmanius careforum. These sharks were much bigger than McGinnis's nail-tooth shark.
Troglocladodus trimblei and Glikmanius careforum date back to the Middle and Late Mississippian periods. Glikmanius careforum is believed to have had a particularly powerful bite.
"These discoveries help scientists to better understand the relationship and evolution of modern shark species within this relatively small geographic region," stated Trimble.
The discovery was revealed in a study published January 24 in the Journal of Paleontology.
The article was written with the assistance of a news analysis system.
