The Fruitadens Paper

Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America

1. Richard J. Butler (1,2,*)
2. Peter M. Galton (3,†)
3. Laura B. Porro (4)
4. Luis M. Chiappe (5)
5. Donald M. Henderson (6)
6. Gregory M. Erickson (7)


1. Bayerische Staatssammlung für Paläontologie und Geologie, Richard-Wagner-Straße 10, 80333 Munich, Germany

2. Department of Palaeontology, The Natural History Museum, London SW7 5BD, UK

3. Professor Emeritus, College of Naturopathic Medicine, University of Bridgeport,
Bridgeport, CT 06604, USA

4. Department of Organismal Biology and Anatomy, University of Chicago, IL 60637, USA

5. The Dinosaur Institute, Natural History Museum of Los Angeles County, Los Angeles, CA 90007, USA

6. Royal Tyrrell Museum of Palaeontology, PO Box 7500, Drumheller, Alberta T0J 0Y0, Canada

7. Department of Biological Science, Florida State University,
Tallahassee, FL 32306-4295, USA

* Author for correspondence (butler.richard.j@gmail.com).

† Present address: 315 Southern Hills Drive, Rio Vista, CA 94571, USA.

Abstract:


The extremes of dinosaur body size have long fascinated scientists. The smallest (<1 m length) known dinosaurs are carnivorous saurischian theropods, and similarly diminutive herbivorous or omnivorous ornithischians (the other major group of dinosaurs) are unknown. We report a new ornithischian dinosaur, Fruitadens haagarorum, from the Late Jurassic of western North America that rivals the smallest theropods in size. The largest specimens of Fruitadens represent young adults in their fifth year of development and are estimated at just 65–75 cm in total body length and 0.5–0.75 kg body mass. They are thus the smallest known ornithischians. Fruitadens is a late-surviving member of the basal dinosaur clade Heterodontosauridae, and is the first member of this clade to be described from North America. The craniodental anatomy and diminutive body size of Fruitadens suggest that this taxon was an ecological generalist with an omnivorous diet, thus providing new insights into morphological and palaeoecological diversity within Dinosauria. Late-surviving (Late Jurassic and Early Cretaceous) heterodontosaurids are smaller and less ecologically specialized than Early (Late Triassic and Early Jurassic) heterodontosaurids, and this ecological generalization may account in part for the remarkable 100-million-year-long longevity of the clade.

Still wish there were sabre toothed heterodontosaurid carnivores...;)