Rhabdodon

*Rhabdodon priscus*

*Rhabdodon'*, (meaning “fluted tooth”) is a genus of dinosaur that lived in Europe approximately 70 million years ago in the Late Cretaceous. It was an Rhabdodontid. Current evidence indicates it is an ornithopod similar to Tenontosaurus. Rhabdodon priscus is the type species; another species, described in 1991, is R. septimanicus (Buffetaut and Le Loeuff), but these may be the same animal. Rhabdodon lived in Spain, France, and on Haţeg Island in Romania. Remains of very similar dinosaur (femur and limb bone fragments) are also known from the Czech Republic. It was smaller than its relatives, possibly due to the insular environment that existed in Europe during the Cretaceous period.

Ornithopods were some of the most common dinosaurs unearthed in the 19th century, mainly because so many of them lived in Europe (where paleontology was pretty much invented). Discovered in 1869, Rhabdodon has yet to be properly classified, since (not to get too technical) it shares some of the characteristics of two types of ornithopods: Hadrosaurs and hypsilophodonts (herbivores similar to Hypsilophodon). In any event, Rhabdodon was a fairly small ornithopod for its time; other than that, its most notable features were its roundish teeth and unusually blunt head.

## Discovery

Two species of *Rhabdodon* are known, *Rhabdodon priscus*, the type species, and *R. septimanicus* (Buffetaut and Le Loeuff, 1991). *Rhabdodon* remains are currently known from southern France, although fragmentary remains from eastern Spain have been assigned to the genus. *Rhabdodon* was large compared to its nearest relatives, and indeed one recent paper ( Ősi et al. (2012)) determined it is larger than the basal rhabdodontid status; from this they suggested that it actually experienced gigantism on the "mainland"; and not insular dwarfism as previous suggested.

## Classification

The cladogram below is based on the analysis of Ösi et al. (2012):

## Paleobiology

*Rhabdodon* was probably an important herbivore in Cretaceous Europe. *Rhabdodon's* predators include the abelisaurid *Arcovenator*, and young may have been prey for *Pyroraptor*.

## Paleoecology

*Rhabdodon priscus* is known from a specimen from the Marnes Rouges Inférieures Formation. The material of *Rhabdodon priscus* includes a dentary and many other postcranial remains. More specifically, it is known from the Bellevue layer, which has produced many vertebrate fossils. Even though it produced many vertebrates, the formation only has a scarce record of plants and invertebrates. The non-dinosaurian vertebrates consist of *Lepisosteus*, an indeterminate turtle, and a crocodile. Dinosaurian fauna from the Marnes Rouges Inférieures Formation include *Ampelosaurus*, an animal classified as Dromaeosauridae indet., and an indeterminate ankylosaur. The bird *Gargantuavis philoinos*, and dinosaur eggs have also been recovered.

Another formation *Rhabdodon priscus* is known from is Gres de Saint-Chinian. Along with both *Rhabdodon priscus*, *Rhabdodon septimanicus*, dinosaur eggs, Nodosauridae indet. (previously known as *Rhodanosaurus lugdunensis*), Theropoda indet., *Variraptor mechinorum*, Avialae indet., Enantiornithes indet., and a possible Abelisauridae indet. are known from this formation.

*Rhabdodon priscus* is one of few vertebrates known from the Gres de Labarre Formation. The only other fossils from the formation belong to *Ampelosaurus atacis* and a Nodosauridae indet.

### Villalba de la Sierra Formation

*Rhabdodon* sp. is from the latest Cretaceous aged Lo Hueco region in the Villalba de la Sierra Formation. A study shows that the area around Lo Hueco dates to the late Campanian and early Maastrichtian, although a more recent study revised the later date to the latest Maastrichtian. The study showed that Lo Hueco was near the coast of the Tethys Sea, a large seaway through southern Europe and northern Africa. The area directly on the coast was shown to be a brackish-freshwater aquatic environment, with a muddy flood-plain beside it. Lo Hueco was found to be inside the flood-plain. The flood plain was found to have distributary channels of sand and terrigenous material.

Many dinosaurs have been found in the Villalba de la Sierra Formation, including *Rhabdodon* sp. They consist of possible *Lirainosaurus* remains, *Ampelosaurus atacis*, unknown basal euornithopods, probable ankylosaurians, one undetermined dromaeosaurine, and one unknown velociraptorine. The plants known from the formation are represented by carbonized branches and leaves. Invertebrates are solely known from bivalves and gastropods. Fishes from the formation include lepisosteids, and unidentified actinopterygians and teleosteans. Turtle fossils are very common, but only two different groups have been identified, the bothremydids *Polysternon* and *Rosasia*, along with an undetermined Pancryptodiran. Squamate lizards are known only from a few undetermined specimens, and eusuchian crocodiles are known from a specimen with similarities to *Allodaposuchus* and *Musturzabalsuchus*.

## JPInstitute.com Description

This was the last known member of the plant-eating family of dinosaurs that includes Iguanodon. By the later part of the Cretaceous, most of the iguanodonts had evolved into hadrosaurs. It had a long tail and a beak. Rhabdodon had short front arms meaning it probably walked on its back legs most of the time.

Rhabdodon was first described in 1869, making it one of the earliest dinosaurs to be discovered. Since then, there has been much discussion as to how it should be classified. Even though a nearly complete skeleton exists, it is still a point of some discussion as to whether it is an iguanodont or, as some have suggested, a hypsilophodont - both are currently accepted.

## Links

http://web.archive.org/web/20040214171947fw\_/http://www.jpinstitute.com/dinopedia/dinocards/dc\_rhabd.html

## References

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