Between 2008 and 2011, scientists unearthed tiny pieces of fossils in the Las Cascadas paleontological site.
Back in the lab, "I started putting everything together and realized, Oh wow, I have a nearly complete jaw," study leader Aldo Rincon, a graduate student in vertebrate paleontology at the University of Florida in Gainesville, said in a statement.
From the new fossils, Rincon and his team described two new prehistoric camel species: Aguascalietia panamaensis and Aguascalientia minuta, both of which roamed the Central American tropics about 20 million years ago.
Both animals had long, crocodile-like snouts, likely specialized for finding fruits and leaves in dense vegetation, he told National Geographic News. Also, their teeth were short and sharp, features common to animals that browse, not graze, for food, Rincon noted.
Based on the fossils, Rincon and colleagues estimate the tiniest of the two camels, A. minuta, stood about 2 feet (60 centimeters) tall, about the size of a modern-day musk deer. A. panamaensis was about 2.5 feet (80 centimeters) tall.
"They're very cute animals," said study co-author Carlos Jaramillo, a scientist at the Smithsonian Tropical Research Institute in Panama.
"I never expected to find something like that in Panama."
Though modern-day camels are for the most part found only in African and Middle Eastern deserts, the mammals were abundant in the Americas about 35 to 40 million years ago.
Camels later branched in two lineages—one that went to South America, where the animals evolved into llamas and their relatives, and one to Asia. The Asian lineage evolved into the big camels we know today, study leader Rincon said. (See camel pictures.)
Now that we know camels once lived as far south as Panama, Rincon said, scientists should be better able to piece together the evolution of the two-toed beasts.
Tropical-camel study appeared online recently in the Journal of Vertebrate Paleontology.