In the Late Jurassic (around 150 Mya) of the USA, famous dinosaurs such as Allosaurus, Stegosaurus, Apatosaurus (= Brontosaurus), and Brachiosaurus were roaming the American west. Running around their feet, and doing their best not to get trampled, was a tiny dinosaur named Fruitadens haagarorum, named by Butler and colleagues in 2010). Fruitadens was a tiny, plant-eating dinosaur from the group known as heterdontosaurids.
|Artist’s reconstruction of Fruitadens ( by Smokeybjb, and licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.)|
Heterodontosaurids were a group of plant-eating ornithiscians related to iguanodontids (like Iguanodon) and hadrosaurids (like Parasaurolophus and Edmontosaurus), among others. These dinosaurs were commonly fairly small, and had "fangs" towards the front of their mouths.You should be able to see the fangs if you look close enough at the reconstruction. They actually get their name from their strong heterodont dentition. Even so, their morphology is relatively generalized, suggesting more of an omnivorous lifestyle, with plants, insects, and some other small organisms making up the majority of their diets.
Fruitadens was named based on a few individuals (4), but the holotype consists of incomplete jaws, several vertebrae, and partial hind limbs of a nearly full grown individual. This was sufficient, however, to determine that it was, indeed, something unique and new.
|Reconstructed skull of Fruitadens (Butler et al., 2012)|
Fruitadens was estimated by Butler et al. (2010) to have only been about 28 cm long (less than a meter) and weighed less than 1 kg (less than 2 lbs)! That size estimate is quite incredible, especially for a dinosaur that is thought to be nearly full-grown. Overall size would have probably not changed at all, or at least very little, once it became fully mature!
|Full-size Fruitadens haagarorum model with co-author Luis Chiappe (from AP).|
But why bring this up now if this dinosaur was named in 2010? In the original publication, Butler et al. (2010) were unable to go into much detail regarding the description and morphology of this new taxon. But a new, thorough study just published by Butler et al. (2012) has given this small dinosaur its descriptive due. The new study seeks to document this dinosaur in great detail, giving new information not only on Fruitadens, but also on the whole heterdontosaurid family of dinosaurs. This study helps us understand a group of dinosaurs that were not very well known before, and helps clarify a picture that can seem somewhat blurry at times (or all the time...).
This seems to be an excellent example of a taxon that was named in a relatively short paper, but then had a follow-up study to give us a much clearer picture of exactly what it was/is. Too often taxa (not just dinosaurs) are named in short papers or with short blurbs. Little detail is given, and sometimes proper diagnoses are not even provided. I can't tell you how many times I have come across taxa and, when going to the original publications, I find little information other than the name itself. And, going a step further, often times little work has been done on the taxa after the initial publication. This was far worse decades ago and has gotten better since, but various examples can be found still today (e.g. Atrociraptor) with little work done on the taxa themselves and more work done regarding their inclusion in cladograms.
|Depiction of some of the largest known hadrosaurs and, therefore, some of the largest known ornithischians, with a adult male for scale|
|Depiction of Fruitadens haagarorum, with a portion of an adult male for scale|
Butler RJ, Galton PM, Porro LB, Chiappe LM, Henderson DM, Erickson GM (2010) Lower limits of ornithischian dinosaur body size inferred from a diminutive new Upper Jurassic heterodontosaurid from North America. Proceedings of the Royal Society B 277: 375–381.
Butler RJ, Porro LB, Galton PM, Chiappe LM (2012) Anatomy and cranial functional morphology of the small-bodied dinosaur Fruitadens haagarorum from the Upper Jurassic of the USA. PLoS ONE 7(4): e31556. doi:10.1371/journal.pone.0031556