U. FLORIDA (US) — Paleontologists have found remarkably well-preserved fossils of two crocodilians and a hippo-like mammal during recent excavations in the Panama Canal.
The ancient extinct alligator-like animals and an extinct hippo-like species—previously unknown to science—inhabited Central America during the Miocene about 20 million years ago.
The research expands the range of ancient animals in the subtropics—some of the most diverse areas today about which little is known historically because lush vegetation prevents paleontological excavations—and may be used to better understand how climate change affects species dispersal today.
The fossils shed new light on scientists’ understanding of species distribution because they represent a time before the formation of the Isthmus of Panama, when the continents of North and South America were separated by oceanic waters.
This reconstruction of Culebrasuchus mesoamericanus represents a new primitive species researchers believe may represent an evolutionary transition between caimans and alligators. (Credit: Danielle Byerley/Florida Museum of Natural History)
“In part we are trying to understand how ecosystems have responded to animals moving long distances and across geographic barriers in the past,” says study co-author Jonathan Bloch, associate curator of vertebrate paleontology at the Florida Museum of Natural History at the University of Florida.
“It’s a testing ground for things like invasive species—if you have things that migrated from one place into another in the past, then potentially you have the ability to look at what impact a new species might have on an ecosystem in the future.”
The two studies appear online today in the same issue of the Journal of Vertebrate Paleontology.
Researchers analyzed all known crocodilian fossils from the Panama Canal, including the oldest records of Central American caimans, which are cousins of alligators. The more primitive species, named Culebrasuchus mesoamericanus, may represent an evolutionary transition between caimans and alligators, says Alex Hastings, visiting instructor at Georgia Southern University.
“You mix an alligator and one of the more primitive caimans and you end up with this caiman that has a much flatter snout, making it more like an alligator,” Hastings says. “Before this, there were no fossil crocodilian skulls known from Central America.”
Christopher Brochu, an assistant professor of vertebrate paleontology in the department of geoscience at the University of Iowa, says “the caiman fossil record is tantalizing,” and the new data shows there is still a long way to go before researchers understand the group.
“The fossils that are in this paper are from a later time period, but some of them appear to be earlier-branching groups, which could be very important,” says Brochu, who was not involved with the study. “The problem is, because we know so little about early caiman history, it’s very difficult to tell where these later forms actually go on the family tree.”
The new mammal species researchers described is an anthracothere, Arretotherium meridionale, an even-toed hooved mammal previously thought to be related to living hippos and intensively studied on the basis of its hypothetical relationship with whales.
About the size of a cow, the mammal would have lived in a semi-aquatic environment in Central America, says lead author Aldo Rincon, a graduate student at the University of Florida.
“With the evolution of new terrestrial corridors like this peninsula connecting North America with Central America, this is one of the most amazing examples of the different kind of paths land animals can take,” Rincon says. “Somehow this anthracothere is similar to anthracotheres from other continents like northern Africa and northeastern Asia.”
Researchers also name a second crocodilian species, Centenariosuchus gilmorei, after Charles Gilmore, who first reported evidence of crocodilian fossils collected during construction of the canal 100 years ago. The genus is named in honor of the canal’s centennial in 2014.
Researchers will continue excavating deposits from the Panama Canal during construction to widen and straighten the channel and build new locks. The project is funded by a $3.8 million NSF grant to develop partnerships between the US and Panama and engage the next generation of scientists in paleontological and geological discoveries along the canal.
The research was funded by the National Science Foundation Panama Canal Partnerships in International Research and Education project, which supports paleontological excavation of the canal during construction expected to continue through 2014.
Source: University of Florida