An interesting "rock" initially tossed aside at a FedEx site near Pittsburgh International Airport turns out to be the skull of a meat-eating, early terrestrial amphibian that lived 70 million years before the first dinosaurs emerged, according to a paper released Monday in the Annals of Carnegie Museum.
The approximately 300-million-year-old carnivorous amphibian has been named Fedexia striegeli. The genus name refers to the well-known shipping service, while the species name recognizes Adam Striegel, who spotted the animal's well-preserved, 5-inch-long (12.5-centimeter-long) fossil skull while he was a University of Pittsburgh student on a field trip.
Striegel originally threw it aside, thinking it wasn't important. But then he and class lecturer Charles Jones noticed its pointy teeth and tusks, so the skull was brought to experts at the Carnegie Museum of Natural History.
"Fedexia might have resembled, using modern analogies, an overgrown or giant newt salamander about 2 feet long, including the tail, with a coarse, granular skin texture," co-author David Berman, curator of vertebrate paleontology at the museum, told Discovery News.
The graininess probably resulted from rice-sized bony elements. Such features were found on a close relative of this species from New Mexico, Anconastes vesperus, which Berman and other colleagues discovered. He said the protrusions "undoubtedly protected it from physical injuries from either predators or inanimate obstacles in the environment, and loss of body moisture through the skin, which modern amphibians are susceptible to."
He added that the carnivore's "large palatal tusks were undoubtedly formidable weapons for holding onto, crushing and dismembering prey" that likely included everything from smaller amphibians to large insects.
Analysis of the skull determined that Fedexia belongs to an extinct group of amphibians called Trematopidae. The trematopids provide the first evidence for North American vertebrate life that was adapted to a mostly terrestrial existence.
Co-author David Brezinski, an associate curator in the Section of Invertebrate Paleontology at the museum, explained to Discovery News that the toothy land-dweller lived when Earth's climate was in a period of radical transition.
Pennsylvania then was in the tropics and experienced a lot of rain during the Late Paleozoic Ice Age, starting at around 320 million years ago. This helped to fuel plant growth.
"The increased rainfall and attendant wet conditions were perfect for amphibians," Brezinski said. "That is, until things temporarily began drying out at about 304 million years ago."
The preceding period when moist conditions flourished led to what is now called the "Age of Amphibians," when the ancestors of Fedexia and other amphibians were a dominant group in Western Pennsylvania and other regions.
The loss of water during the dryout, however, forced many of these animals, like Fedexia, to shift from a mainly aquatic to a mostly terrestrial existence.
"Amphibians that could exist for protracted times out of water should have been selected for," Brezinski said.
Relatives of Fedexia dating to 20 million years after its lifetime have been found at other sites, suggesting that this group successfully expanded and diversified even as the tropics became drier.
Researchers believe that these very early land-adapted amphibians returned to the water perhaps only to mate or lay eggs.
Although the Trematopidae eventually died out, they were part of a superfamily called Dissorphoidea that, Berman said, "are often hypothesized as possible ancestors of modern amphibians."