Although the Land Before Time character Ducky, together with her parents and biological siblings, is consistently identified in official material, including the official Land Before Time website, as Parasaurolophus, there seems to have been much confusion over what species Ducky is, by critics, reviewers and fans alike.
Although described as a Parasaurolophus on the official Land Before Time website, fans have pointed out that the character Ducky is not drawn in a style correctly matching the estimated designs of Parasaurolophus. The character is drawn with a wide bill and a short, upright, pointed cranial crest, as are her siblings and her mother and father. Based on analysis of fossilized skulls, Parasaurolophus walkeri, for example, would have had a slender jawline and a long crest with slight curvature, as would Parasaurolophus tubicen. While the third accepted species of Parasaurolophus, P. cyrtocristatus, had a much shorter crest than the other two species, skull analysis shows that it still had a narrow jaw, and the crest had a downward, circular curvature.
Due to these inconsistencies, fans and reviewers of the Land Before Time series have frequently pointed out that with Ducky's design, she better matches the description of a Saurolophus; a genus of dinosaur once believed to have been closely related to Parasaurolophus, (with the name "Parasaurolophus" being based on "Saurolophus") because of the similarities in their appearance, although recently found out not to be directly related. Fossilized skulls of Saurolophus show that its cranial crest was more spike-like in appearance, and appears to jut straight out of the back of the head. It was also significantly shorter than the crest of Parasaurolophus. Ducky is actually referred to as a Saurolophus in the Land Before Time sing-along video and in some concept art for the original movie.
Adding to the confusion, proper Parasaurolophus are depicted alongside Ducky's species throughout the series. Some Parasaurolophus are seen in the first movie, stampeding away from the Great Earthshake, along with Saurolophus (even appearing in the same shots), and make a small appearance during a musical number in Journey Through the Mists. Parasaurolophus have made very consistent appearances in later movies and the television series, frequently appearing alongside Ducky's species.
Another genus Ducky has been mistakenly referred to as is Anatosaurus (which was reassigned to the genus Edmontosaurus in 1979). However, while the character is, as mentioned above, drawn with a long head-crest, which Edmontosaurus, or "Anatosaurus" is not believed to have had. In 2013 it was discovered that Edmontosaurus did have a fleshy crest on its head, similar to a rooster's comb, however it still did not resemble Ducky's crest. This misalign ment is most likely brought on by the broadness of the character's mouth, as (possibly) the most well-noted feature of Edmontosaurus is its broad bill.
Interestingly, while it is mostly fans who mistake Ducky to be a Saurolophus, critics seem to more often align the character to the genus Anatosaurus. She has also been called an "Anatosaurus" in several books, including Jerry Beck's The Animated Movie Guide and David Mansour's From Abba to Zoom: A Pop-Culture Encyclopedia of the Late 20th Century. Ducky has also been called an "Anatosaurus" in one official Land Before Time activity book, and the original script for the first The Land Before Time refers to her and her family as Anatosaurus as well.
- Ducky is referred to as a Trachodon in an early iteration of the Land Before Time website.
- Ducky was referred to as a "perky, amphibious thing" by Hal Hinson of the Washington Post,
- Ducky was incorrectly labelled a platypus in the book, The Animated Films of Don Bluth.
- Ducky was once referred to as a Corythosaurus in the Wikipedia page for The Land Before Time.
- The 1989 book Geolog, by the Geological Association of Canada, speculates Ducky's species to be Corythosaurus in their reference to The Land Before Time, on page 45.
- The official Land Before Time website. Retrieved on February 18th, 2009.
- Ostrom, John H. 1961 A new species of hadrosaurian dinosaur from the Cretaceous of New Mexico, Journal of Paleontology, Volume 35, 3rd issue, on pages 575–577.
- Revision history of Ducky's Wikipedia article; specifically edits in which users call her a Saurolophus instead of a Parasaurolophus. (November 14th, 2006) (January 5th, 2007) (February 26th, 2007) (May 22nd, 2007) (July 13th, 2007) (August 26th, 2007.) (25th September, 2007.) Originally retrieved on April 17th/18th, 2008.
- Revision history of List of The Land Before Time characters on Wikipedia; specifically edits in which users call Ducky a Saurolophus instead of a Parasaurolophus. September 30th, 2008, January 16th, 2009. June 11th, 2009.
- Revision history of The Land Before Time's Wikipedia article; specifically edits in which users call her a Saurolophus instead of a Parasaurolophus. (September 28th, 2008) (August 10th, 2005) Originally retrieved on November 28th, 2008.
- A user on dvd.ciao.co.uk making a comment on The Land Before Time IV: Journey through the Mists refers to Ducky's species as Saurolophus, rather than Parasaurolophus. Retrieved on May 2nd, 2008.
- Mobilecastle.biz summary of The Land Before Time
- A fan-based The Land Before Time website; "Littlefoot's dictionary" cited; "Swimmer (Ducky) is defined as a Land Before Time term for Saurolophus, instead of Parasaurolophus. www.freewebs.com. Retrieved on March 18th, 2009.
- The Land Before Time: Great Valley Racing Adventure at psx.gamezone.com. Retrieved on April 7th, 2009.
- A Land Before Time fan-art artist refers to Ducky as a Saurolophus instead of a Parasaurolophus. Retrieved on June 9th, 2009.
- Parks, William A. Parasaurolophus walkeri, a new genus and species of crested trachodont dinosaur, volume 13, pages 1-32. Published: 1922, University of Toronto Studies, Geology Series.
- Maryańska, Teresa and Osmólska, Halszka; 1981. "Cranial anatomy of Saurolophus angustirostris with comments on the Asian Hadrosauridae (Dinosauria)", from the Journal of Palaeontologia Polonica, vol. 42, pp. 5–24. Retrieved on February 18th, 2009.
- Edit on The Land Before Time's Wikipedia article. (July 3rd, 2005)
- The Complete Dinosaur, by James O. Farlow, M. K. Brett-Surman, and Robert F. Walters. Page 704. Indiana University Press, 1999. ISBN 0253213134/ISBN 9780253213136 Retrieved on November 29th, 2008.
- Lull, Richard Swann; and Wright, Nelda E. (1942). Hadrosaurian Dinosaurs of North America. pp. 151–164.
- Wendy Miller's review of The Land Before Time, on the Mohave Daily Miner. November 29th, 1988.  Retrieved on October 8th, 2008.
- Mary Kalin-Casey's review of The Big Freeze www.reel.com Retrieved on April 23rd, 2008.
- Joe Leydon's review of Journey Through the Mists, on Variety.com (Mon., 23-12-1996) www.variety.com Retrieved on April 1st, 2008.
- British journalist MJ Simpson's review of The Land Before Time II: The Great Valley Adventure, on his official website. Retrieved on December 4th, 2008.
- The Animated Movie Guide by Jerry Beck. Published 2005, Chicago Review Press. ISBN 1556525915 Page 138.
- From Abba to Zoom: A Pop Culture Encyclopedia of the Late 20th Century by David Mansour. Published 2005 Andrews McMeel Publishing. ISBN 0740751182 Page 272.
- The Land Before Time official website, circa January 2001
- Review on The Land Before Time by Hal Hinson, Staff Writer for the Washington Post, on November 18, 1988: www.washingtonpost.com Retrieved on March 14th, 2008.
- The Animated Films of Don Bluth Retrieved on January 23rd, 2007.
- Revision of Wikipedia's "The Land Before Time" article as of 07:33, 23rd April 2005, in which the character Ducky's species is given as Corythosaurus, rather than Parasaurolophus. Retrieved on February 18th, 2009.
- Geolog, page 45. Written and published by the Geological Association of Canada, in 1989. Digitized 22nd Sept., 2008.  Retrieved on February 20th, 2009.
- Yahoo! Answers.com 2006 discussion amongst fans, over The Land Before Time character Ducky's species.
- Invisionfree.com discussion concerning the Land Before Time characters' species.