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Re: Oldest North American Bird Tracks

Okay, I'm in my office and have looked up the answer on differences between bird tracks and dinosaur tracks. This is information from the following paper:

Wright, J. L., 2004. Bird-like features of dinosaur fooprints. In: P. J. Currie, E. B. Koppelhus, M. A. Shugar, and J. L. Wright (eds.). Feathered Dragons. Indiana University Press, Bloomington & Indianapolis. pp. 167-181.

Theropod tracks (I know birds are theropods, but I will use "theropod" to differenciate all other theropods and Avialae, so no one will pick at me for it) have similar number and arrangement of phalangeal pads along with clear claw marks. Most theropod tracks have asymmetrical digits caused by length differences in digits II and IV. Several of the srctometatarsalian dinosaurs have feet like many modern ground-dwelling birds like emus.

Most ornithopods are symmetrical, don't have claw marks and do have a "heel' impression formed by the fleshy pad at the back of the foot. Ornithopod tracks usually have very wide digit impressions and rarely appear bird-like.

Most Mesozic bird tracks are waders or ground-dwelling birds. Some "are very distinctive" showing narrow digit impressions, some show webbing between digits, a hallux, and a high divarication angle between digits usually greater than 110 degrees. Many theropod tracks also show clear hallux impressions, however some Mesozoic bird tracks tend to have a more posteriorly projected hallux than theropods. Most dinosaurs footprints rarely have a divarication angle greater than 90 degrees. Bird tracks are symmetrical and usually show a metatarsal pad.

Hopefully this makes the differences a little clearer. I now understand them more, so thanks for the question Jean-Michel!

Cheers,
Andrew

Andrew R. C. Milner
City Paleontologist
St. George Dinosaur Discovery Site at Johnson Farm
2180 East Riverside Drive
St. George, Utah 84790
USA

Tracksite Phone: (435) 574-DINO (3466)
Cell: (435) 705-0173
Tracksite Fax: (435) 627-0340
Home: (435) 477-9467

Email: amilner@sgcity.org
Website: http://www.dinotrax.com

"There is no branch of detective science which is so important and so much neglected as the art of tracing footsteps" -- Sir Arthur Conan Doyle, 1891


----- Original Message ----- From: "Jean-Michel BENOIT" <s.aegyptiacus@wanadoo.fr>
To: "Dinosaur Mailing List" <dinosaur@usc.edu>
Cc: <andrew@hanmansfossils.com>
Sent: Thursday, November 24, 2005 12:44 PM
Subject: Re: Oldest North American Bird Tracks


Hello all
knowing the relationship between birds (avialians) and dinos, how can one be
sure that these tracks have not been made by a small (non aviian) dinosaur
(known or not)?
Sorry if this is a silly question.
Cheers,
Jean-Michel

----- Original Message -----
From: "Andrew RC Milner" <andrew@hanmansfossils.com>
To: "Dinosaur Mailing List" <dinosaur@usc.edu>
Sent: Thursday, November 24, 2005 8:22 PM
Subject: Oldest North American Bird Tracks


This aired on Salt Lake City Station, KSL 5, on Tuesday. Here is a link
to 
read about bird tracks from the Early Cretaceous Cedar Mountain Fm.
Features Jim Kirkland, Joanna Wright, John Foster, and Don DeBlieux doing
the repelling.

http://www.ksl.com/index.php?nid=148&sid=131637

Cheers

Andrew R. C. Milner
City Paleontologist
St. George Dinosaur Discovery Site at Johnson Farm
2180 East Riverside Drive
St. George, Utah 84790
USA

http://www.dinotrax.com

Tracksite Phone: (435) 574-3466
Cell: (435) 705-0173
Tracksite Fax: (435) 627-0340
Home Phone: (435) 477-9467
Email: amilner@sgcity.org
or andrew@hanmansfossils.com

"There is no branch of detective science which is so important and so much
neglected as the art of tracing footsteps" -- Sir Arthur Conan Doyle, 1891


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