Fruitadens haagarorum – Tiniest Dinosaur known to Science

Thirty years after its fossils were discovered in Colorado, a new genus of Ornithischian dinosaur has been named and described, perhaps the smallest dinosaur discovered to date.  In a paper published in the scientific journal “Royal Society Journal Proceedings B (Biology)”, the research team claim that this little dinosaur weighed less than a kilogramme.  This puts the tiny Fruitadens haagarorum in pole position when it comes to identifying the smallest species of dinosaur discovered to date.  Other contenders include the feathered Microraptor gui from the Liaoning Province of north-east China.  Microraptor is estimated to have measured something like 40-60 centimetres.  The diminutive Micropachycephalosaurus, also from China was of a similar size, although the exact taxonomic classification of this Late Cretaceous Ornithischian remains uncertain (incertae sedis).

There were certainly many small Theropods but for the moment it is Fruitadens haagarorum that is taking the plaudits for being the smallest dinosaur known from the fossil record,  with a body weight no more than two bags of sugar.

An Illustration of F. haagarorum

Picture Credit: D. Trankina/NHMLAC

The picture shows an artist’s impression of Fruitadens haagarorum in comparison with an adult human.   The fossils had been housed at the Natural History Museum of Los Angeles County, since they were discovered in Colorado in 1979.  The partial remains of at least four individuals including skull material are known and it is believed that this animal was a a member of the Heterodontosauridae, a primitive group of Ornithopods.  The fossils were found in sandstones dating from the Late Jurassic (Tithonian faunal stage), approximately 150 million years ago.  The sandstones are part of the famous Morrison Formation of rocks from the Upper Jurassic which have yielded a large number of famous dinosaurs such as Apatosaurus, Diplodocus, Allosaurus and Stegosaurus.

The study into this tiny, fleet footed dinosaur was led by Richard Butler from the Bavarian State Collection for Palaeontology in Munich, southern Germany.  Analysis of the teeth in the minute jaw indicate that this Ornithischian may have been an omnivore.  Most Ornithischians are totally herbivorous but this agile little dinosaur may have eaten a variety of food stuffs, plant material, insects and perhaps small mammals, amphibians and lizards.

A Fragment of Dinosaur Jaw

Jawbone fragment of Fruitadens.

Picture Credit: NHMLAC

The picture shows a tiny fragment of lower jaw with dentition (teeth) of the minute dinosaur Fruitadens.

Commenting on the prospect of an Ornithischian dinosaur being an omnivore, Richard Butler stated:

“This is unusual for that group [Ornithischia] most of them were strict herbivores.  But if you’re small, it is hard to feed on just vegetation, as it is difficult to digest”.

Bigger animals with much larger guts were better able to survive on a plant-only diet.  Larger animals have bigger guts, and a big gut is what you need to help digest tough plant material.  The genus name refers to an area of Colorado called Fruita, where the fossils were first discovered.  The specific name is in honour of the Haaga family who have long been supporters of the Natural History Museum of Los Angeles County.

Dr. Butler went onto add:

“Fruitadens, comes from a series of rocks, the Morrison Formation, which palaeontologists have studied intensively for 130 years, and from which dozens of dinosaur species are already known.  Yet it is still possible to discover completely unique and remarkable species.  If dinosaur ecosystems were that diverse, who knows what astonishing beasts are waiting for us to discover”?

This little dinosaur probably scampered around the undergrowth, avoiding predators such as Ornitholestes, using its speed to keep itself out of trouble.  Ironically, some of the contemporaries of Fruitadens, the Sauropods were so large that this little dinosaur could have run around these leviathans without them noticing.

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