User:Devries.r/sandbox

Rhabododontidae is a family of herbivorous ornithopod dinosaurs that first appeared during the Upper Barremian of Spain, 125.0-129.4 Ma, in the middle of the Lower Cretaceous. The Rhabododontidae are endemic to Europe with additional specimens in France, Hungary, Austria, and Romania. The defining characteristics of the clade Rhabdodontidae are that all teeth are spade-shaped, there are three or more premaxillary teeth, there is a distinct difference between the two maxillary and dentary teeth ridge patterns, and there is a uniquely shaped femur, humerus, and ulna. Members of Rhabdodontidae have an adult body length of 1.6 to 6.0 meters, with the biggest species being Rhabdodon.

Description

Teeth

Rhabdodontidae premaxillary, maxillary, and dentary teeth.

Teeth of Mochlodon vorosi n. sp. (Rhabdodontidae) from the Upper Cretaceous Csehbánya Formation, Iharkút, western Hungary.

Rhabdodontids have a simple dentition with leaf-shaped teeth used for a powerful scissors-like shearing. These teeth are well-suited to a diet of tough and fibrous plants. Each tooth has a ridge on it that is offset from the midline of the tooth. These ridges also have a specific pattern which is unique to Rhabodontids: their dentary teeth have a central primary ridge with multiple equally spaced secondary ridges, and their maxillary teeth have no primary ridge and have similarly-sized secondary ridges.

Femur

A unique characteristic of the Rhabdodontid femur is a non-pendant, crested fourth trochanter.

Humerus

A unique characteristic of the Rhabdodontid humerus is a lack of a proximal bicipital sulcus, and a concave border between the head and the deltopectoral crest.

Ulna

A unique characteristic of the Rhabdodontid ulna is a large olecranon process.

Relationship to Other Fauna

Rhabdodontids and Nodosaurs were overtaken by Hadrosaurs as the major herbivorous dinosaur group during the Maastrichtian period, 66.0-72.1 Ma, of the Late Cretaceous. Titanosaurs coexisted with all of these groups throughout the Maastrichtian. Transylvania is the only location known thus far to have had Rhabdodontids, Nodosaurs, Titanosaurs, and Hadrosaurs all coexisting together.

Evolution

Adult body sizes of Mochlodon, Zalmoxes and Rhabdodon.

Rhabdodontids first appeared during the Barremian Age in the early Cretaceous, and an extensive fossil record shows that they remained extant until the Maastrichtian Age of the Late Cretaceous. During much of the Late Cretaceous, an isolated island habit in the western Tethyan archipelago contributed to the evolution of Rhabdodontids in two main ways. First, the Rhabdodontid dentition is relatively primitive, which is consistent with their habitat being sheltered from expansive mixing leading to a long period of dominance. Second, the fossil record contains three genera of Rhabdodontids-- Mocholdon, Zalmoxes, and Rhabdodon—that make up two geographically separated lines in the archipelago. The smaller sizes of Mocholodon (1.6-1.8 m) and Zalmoxes (2.0-2.5 m) relative to Rhabodon (5.0-6.0 m) and the island locale that all three genera shared led to the hypothesis of island nanism in the case of the former two. However, island nanism has been disputed in a recent study by Osi et al who used femur length to estimate body size through evolution in the Rhabdodontid lineage. The conclusion was that in the eastern lineage comprised of Zalmoxes and Mochlodon, the size ranges of both were too close to that of the ancestral rhobodontid to support the hypothesis of nanism. Osi et al instead came to the conclusion that Rhabdodon in the western lineage is a case of gigantism in the group Rhabdodontidae.

Paleobiology

The Late Cretaceous is characterized by a warm temperate climate that extended to the poles, elevated sea levels, and inland seas. With a dentition adapted to shearing vegetation, members of the Rhabododontidae family were well-suited for life in the lush, vegetative environment at middle latitudes.