Tell-tale toes point to oldest-known fossil bird tracks from Australia
Oct. 28, 2013 — Two fossilized footprints found at Dinosaur Cove in Victoria, Australia, were likely made by birds during the Early Cretaceous, making them the oldest known bird tracks in Australia.
Share This:
The journal Palaeontology is publishing an analysis of the footprints led by Anthony Martin, a paleontologist at Emory University in Atlanta who specializes in trace fossils, which include tracks, burrows and nests. The study was co-authored by Patricia Vickers-Rich and Michael Hall of Monash University in Victoria and Thomas Rich of the Museum Victoria in Melbourne.
Much of the rocky coastal strata of Dinosaur Cove in southern Victoria were formed in river valleys in a polar climate during the Early Cretaceous. A great rift valley formed as the ancient supercontinent Gondwana broke up and Australia separated from Antarctica.
"These tracks are evidence that we had sizeable, flying birds living alongside other kinds of dinosaurs on these polar, river floodplains, about 105 million years ago," Martin says.
The thin-toed tracks in fluvial sandstone were likely made by two individual birds that were about the size of a great egret or a small heron, Martin says. Rear-pointing toes helped distinguish the tracks as avian, as opposed to a third nearby fossil track that was discovered at the same time, made by a non-avian theropod.
A long drag mark on one of the two bird tracks particularly interested Martin.
"I immediately knew what it was -- a flight landing track -- because I've seen many similar tracks made by egrets and herons on the sandy beaches of Georgia," Martin says.
Martin often leads student field trips to Georgia's coast and barrier islands, where he studies modern-day tracks and other life traces, to help him better identify fossil traces.
The ancient landing track from Australia "has a beautiful skid mark from the back toe dragging in the sand, likely caused as the bird was flapping its wings and coming in for a soft landing," Martin says. Fossils of landing tracks are rare, he adds, and could add to our understanding of the evolution of flight.
Today's birds are actually modern-day dinosaurs, and share many characteristics with non-avian dinosaurs that went extinct, such as nesting and burrowing. (Martin previously discovered the trace fossils of non-avian dinosaur burrows, including at a site along the coast of Victoria.)
The theropod carnivore Tyrannosaurus rex had a vestigial rear toe, evidence that T. rex shared a common ancestor with birds. "In some dinosaur lineages, that rear toe got longer instead of shorter and made a great adaptation for perching up in trees," Martin says. "Tracks and other trace fossils offer clues to how non-avian dinosaurs and birds evolved and started occupying different ecological niches."
Dinosaur Cove has yielded a rich trove of non-avian dinosaur bones from dozens of species, but only one skeletal piece of a bird -- a fossilized wishbone -- has been found in the Cretaceous rocks of Victoria.
Martin spotted the first known dinosaur trackway of Victoria in 2010 and a few other tracks have been discovered since then. Volunteers working in Dinosaur Cove found these latest tracks on a slab of rock, and Martin later analyzed them.
The tracks were made on the moist sand of a river bank, perhaps following a polar winter, after spring and summer flood waters had subsided, Martin says. "The biggest question for me," he adds, "is whether the birds that made these tracks lived at the site during the polar winter, or migrated there during the spring and summer."
One of the best records of the dinosaur-bird connection has come from discoveries in Liaoning province of Northeastern China, including fossils of non-avian dinosaurs with feathers. Samples of amber have also been found in Liaoning, containing preserved feathers from both birds and non-avian dinosaurs going back to the Cretaceous.
"In contrast, the picture of early bird evolution in the Southern Hemisphere is mostly incomplete," Martin says, "but with these tracks, it just got a little better."
Welcome to SUV System Ltd!
SUV System Ltd is ISO 90012008 Certified electronics distributor with 10 years of experiences.
We have built up long term business relationship with about many companies which are stockers and authorized agents. we have a steady and reliable supply to meet customer's demands to the greatest extent .Confidently, we are able to lower your cost and support your business with our years of professional service.
SUV System Ltd is Electronic Components Distributor Supplies,Find Quality Electronic Components Supplies Products IC(Integrated Circuits),Connectors,Capacitor,Resistors,Diodes,Transistors,LED at Suvsystem.com. Sourcing Other Energy, Environment, Excess Inventory Products from Manufacturers and Suppliers at Suvsystem.com
Electronic Components distributor:http://www.suvsystem.com
Connectors Distributor:http://www.suvsystem.com/l/Connectors-1.html
IC Distributor:http://www.suvsystem.com/l/IC(Integrated-Circuits)-1.html
LED Distributor:http://www.suvsystem.com/l/LED-1.html
Capacitor Distributor:http://www.suvsystem.com/l/Capacitor-1.html
Transistor Distributor:http://www.suvsystem.com/l/Transistors-1.html
Resistor Distributor:http://www.suvsystem.com/l/Resistors-1.html
Diode Distributor:http://www.suvsystem.com/l/Diodes-1.html
SUV System Ltd insists on the managing faith ofsincereness,speciality,foresight, win-win,so we build up stable-relationship customers located all over the world, including the States, Europe, Argentina, UAE, Malaysia, Australia,and India etc
we are focus on the following fields,and hope we can help you.
MOTOROLA IC Current Sensors Resistors SANYO IC About US ON Diodes ST Transistors components Transistors FAIRCHILD diodes NXP Transistors LINEAR IC Microchip IC Resistor Networks Infineon Technologies Transistors Transistors Freescale Switches INFLNEON Diodes IR transistor Discrete Semiconductor Transistors Kingbrigt LED Diodes Inc ON Transistors HARRIS IC Cypress IC High Precision Resistors TDK IC BB IC Other Parts PANASONIC NEC Diodes chip Filter saws Industrial IC Voltage Regulators Transistors Switching Diodes Resistor Arrays IDT IC VISHAY IC NXP Diodes DIODES Transistors ALTERA IC
http://www.suvsystem.com/a/6911.aspx
No comments:
Post a Comment