巴拿马发现形似河马的鳄目动物

University of Florida paleontologists（古生物学者） have discovered remarkably¹ well-preserved fossils of two crocodilians（鳄目动物） and a mammal previously² unknown to science during recent Panama Canal excavations⁴ that began in 2009. The two new ancient extinct alligator⁵-like animals and an extinct hippo-like species 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 two studies appear online today in the same issue of the Journal of Vertebrate Paleontology.   The fossils shed new light on scientists' understanding of species distribution because they represent a time before the formation of the Isthmus⁶ of Panama, when the continents of North and South America were separated by oceanic waters.   "In part we are trying to understand how ecosystems⁸ have responded to animals moving long distances and across geographic⁹ barriers in the past," said study co-author Jonathan Bloch, associate curator of vertebrate paleontology at the Florida Museum of Natural History on the UF campus. "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 ecosystem⁷ in the future."   The research was funded by the National Science Foundation Panama Canal Partnerships¹⁰ in International Research and Education project, which supports paleontological excavation³ of the canal during construction expected to continue through 2014.   "We're very fortunate we could get the funding for PIRE to take advantage of this opportunity -- we're getting to sample these areas that are completely unsampled," said Alex Hastings, lead author of the crocodilian study and a visiting instructor¹¹ at Georgia Southern University who conducted the research for the project as a UF graduate student.   Researchers analyzed¹² all known crocodilian fossils from the Panama Canal, including the oldest records of Central American caimans, which are cousins of alligators¹³. The more primitive¹⁴ species, named Culebrasuchus mesoamericanus, may represent an evolutionary#p#分页标题#e#¹⁵ transition between caimans and alligators, Hastings said.   "You mix an alligator and one of the more primitive caimans and you end up with this caiman that has a much flatter snout（鼻子）, making it more like an alligator," Hastings said. "Before this, there were no fossil crocodilian skulls¹⁶ known from Central America."