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Tracks may tell tale of reptilian land conquest

July 30, 2010
Courtesy of the University of Bristol
and World Science staff

New­found foot­prints in Can­a­da show that rep­tiles were the first back­boned an­i­mals to con­quer dry con­ti­nen­tal in­te­ri­ors, re­search­ers say.

These scaly pi­o­neers some 318 mil­lion years ago, they add, paved the way for the di­no­saurs and for to­day’s di­verse land ecosys­tems.

Lizard-like rep­tiles prowl a river­side dur­ing the Car­bon­i­fer­ous Per­iod, in an ar­tist's il­lus­tra­tion. (© James Robins)

Scientists pub­lished the find­ings this week in the re­search jour­nal Pal­aeo­geog­ra­phy, Pal­ae­o­cli­ma­t­ol­ogy, Pa­lae­o­e­col­ogy.

“The foot­prints date from the Car­bon­if­er­ous Pe­ri­od when a sin­gle super-continent, Pan­gaea, dom­i­nat­ed the world,” said Mike Ben­ton of the Uni­vers­ity of Bris­tol, U.K., one of the in­ves­ti­ga­tors.

“At first life was re­strict­ed to coast­al swamps where lush rain­for­est ex­isted, full of gi­ant ferns and dra­gonflies. How­ev­er, when rep­tiles came on the scene they pushed back the fron­tiers, con­quering the dry con­ti­nen­tal in­te­ri­ors.”

Rep­tiles evolved in­to di­no­saurs lat­er, by the Mes­o­zo­ic Era start­ing about 250 mil­lion years ago.

Re­search group mem­ber How­ard Fal­con-Lang of the Uni­vers­ity of Lon­don was cred­ited with find­ing the prints in sea­cliffs on the Bay of Fun­dy, New Bruns­wick, Can­a­da.

The new­found track­ways. (image cour­tesy How­ard Fal­con-Lang)

It has long been sus­pected that rep­tiles were the first to make the con­ti­nen­tal in­te­ri­ors their home. This is be­cause rep­tiles don’t need to re­turn to wa­ter to breed, un­like their am­phib­i­an cousins. 

The new dis­cov­ery proves this the­o­ry, Fal­con-Lang and col­leagues said; the rocks bear­ing the tracks show that these rep­tiles lived on dry riv­er plains hun­dreds of miles (km) from the sea.

The same re­search team re­ported the old­est known rep­tile foot­prints from a dif­fer­ent site in New Bruns­wick in 2007. The new dis­cov­ery is of si­m­i­lar age, and may be even old­er, the group claimed.

“The Bay of Fun­dy is such an amaz­ing place to hunt for fos­sils. The sea-cliffs are rap­idly erod­ing and each rock-fall re­veals ex­cit­ing new fos­sils. You just nev­er know what will turn up next,” Fal­con-Lang said.

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Newfound footprints in Canada show that reptiles were the first backboned animals to conquer dry continental interiors, researchers say. These scaly pioneers some 318 million years ago, they add, paved the way for the dinosaurs and for today’s diverse land ecosystems. Scientists published the findings this week in the research journal Palaeogeography, Palaeoclimatology, Palaeoecology. "The footprints date from the Carboniferous Period when a single super-continent, Pangaea, dominated the world,” said Mike Benton of the University of Bristol, U.K., one of the investigators. “At first life was restricted to coastal swamps where lush rainforest existed, full of giant ferns and dragonflies. However, when reptiles came on the scene they pushed back the frontiers, conquering the dry continental interiors." Reptiles evolved into dinosaurs later, by the Mesozoic Era starting about 250 million years ago. Research group member Howard Falcon-Lang of the University of London was credited with finding the prints in seacliffs on the Bay of Fundy, New Brunswick, Canada. It has long been suspected that reptiles were the first to make the continental interiors their home. This is because reptiles don’t need to return to water to breed, unlike their amphibian cousins. The new discovery proves this theory, Falcon-Lang and colleagues said; the rocks bearing the tracks show that these reptiles lived on dry river plains hundreds of miles from the sea. The same research team reported the oldest known reptile footprints from a different site in New Brunswick in 2007. The new discovery is of similar age, and may be even older, the group claimed. "The Bay of Fundy is such an amazing place to hunt for fossils. The sea-cliffs are rapidly eroding and each rock-fall reveals exciting new fossils. You just never know what will turn up next," Falcon-Lang said.