Proceratosaurus

*Proceratosaurus bradleyi*

*Proceratosaurus* ("before *Ceratosaurus*") is a genus of small-sized (9.8 feet long) theropod dinosaur from the Middle Jurassic. It is a tyrannosauroid that fed on insects, lizards, mammals, and frogs. It lived in England. It has a small, pointed crest on its snout that looks similar to that of *Ceratosaurus*. It lived alongside other theropods, including *Megalosaurus* and *Eustreptospondylus*, sauropods, such as *Cetiosaurus*, stegosaurs, like *Lexovisaurus*, and ornithopods, like *Callovosaurus* and *Camptosaurus*.

Despite its size, *Proceratosaurus* was a fast and deadly carnivore. Its closet relatives are Chinese *Guanlong* and Russian *Kileskus*. It is almost impossible to believe that *Proceratosaurus* would evolve into giant, 45-foot long predators like *Tyrannosaurus* or *Tarbosaurus*. Proceratosaurus itself would go on to create the giant cretaceous carnivores like Daspletosaurus, Alioramus, Yutyrannus, Gorgosaurus, and the fabled Tyrannosaurus.

## History of discovery

In 1910, the British palaeotnologist Arthur Smith Woodward reported a partial theropod skull discovered some time prior by F. Lewis Bradley during excavation for a reservoir at Minchinhampton, a town in the Cotswolds in Gloucestershire, England. Bradley had prepared the skull so that the left side was exposed, and submitted it to the Geological Society of London, which is currently housed at the Natural History Museum catalogued as specimen NHM R 4860. The upper part of the skull missing due to a fissure that had eroded the rock, and was partially filled with calcite. Woodward made the skull the holotype specimen of a new species of *Megalosaurus* (a genus named in 1824), *M. bradleyi*, in honour of its discoverer. At the time it was discovered, it was one of the most complete theropod skulls known from Europe, possibly with the exception of the crushed and hard to interpret skulls of *Compsognathus* and *Archaeopteryx*.

In 1923, the German palaeontologist Friedrich von Huene moved the species to the new genus *Proceratosaurus*, assuming it was the ancestor of the Jurassic genus *Ceratosaurus*, but since the name was only used in a schematic, the name has been considered a *nomen nudum*, an invalidly published name. He validated the name three years later in two 1926 articles by providing a diagnosis of the genus. While remaining one of the best preserved theropod skulls in Europe, and globally one of the best preserved Middle Jurassic theropod skulls, it since received little scientific attention, mainly being mentioned in studies about general aspects of theropod anatomy and evolution. The holotype skull was since CT scanned at the University of Texas, further mechanically prepared to reveal additional details of the skull, jaw, and teeth, and was re-described by the German palaeontologist Oliver W. M. Rauhut an

## Classification

Arthur Smith Woodward, who initially studied *Proceratosaurus*, placed it as a species of *Megalosaurus*, due to same number of premaxillary teeth (4). Later study during the 1930s by Friedrich von Huene suggested a closer relationship with *Ceratosaurus*, and Huene thought both dinosaurs represented members of the group Coelurosauria.

It was not until the late 1980s, after *Ceratosaurus* had been shown to be a much more primitive theropod and not a coelurosaur, that the classification of *Proceratosaurus* was again re-examined. Gregory S. Paul suggested that it was a close relative of *Ornitholestes*, again mainly due to the crest on the nose (though the idea that Ornitholestes bore a nasal crest was later disproved). Paul considered both *Proceratosaurus* and *Ornitholestes* to be neither ceratosaurs nor coelurosaurs, but instead primitive allosauroids. Furthermore, Paul considered the much larger dinosaur *Piveteausaurus* to be the same genus as *Proceratosaurus*, making *Piveteausaurus* a junior synonym. However, no overlapping bones between the two had yet been exposed from the rock around their fossils, and future study showed that they were indeed distinct.

Several phylogenetic studies in the early 21st century finally found *Proceratosaurus* (as well as *Ornitholestes*) to be a coelurosaur, only distantly related to the ceratosaurids and allosauroids, though one opinion published in 2000 considered *Proceratosaurus* a ceratosaurid without presenting supporting evidence. Phylogenetic analyses by Thomas R. Holtz Jr. in 2004 also placed *Proceratosaurus* among the coelurosaurs, though with only weak support, and again found an (also weakly supported) close relationship with *Ornitholestes*.

The first major re-evaluation of *Proceratosaurus* and its relationships was published in 2010 by Oliver Rauhut and colleagues. Their study concluded that *Proceratosaurus* was in fact a coelurosaur, and moreover a tyrannosauroid, a member of the lineage leading to the giant tyrannosaurs of the Late Cretaceous. Furthermore, they found that *Proceratosaurus* was most closely related to the Chinese tyrannosauroid *Guanlong*. They named the clade containing these two dinosaurs the Proceratosauridae, defined as all theropods closer to *Proceratosaurus* than to *Tyrannosaurus*, *Allosaurus*, *Compsognathus*, *Coelurus*, *Ornithomimus*, or *Deinonychus*.

Below is a cladogram by Loewen et al. in 2013.

## Paleobiology

*Proceratosaurus* possessed a nasal crest, which may have served as a display organ but also possibly served to reduce bending stresses on the skull when biting. This may indicate Proceratosaurus used a puncture-pull strategy for hunting prey. However, *Proceratosaurus* was likely not a big game hunter, lacking the bone-crushing teeth and extremely powerful bites of the tyrannosaurids. Instead, it possessed an elongate skull, commonly found in basal coelurosaurs and basal tyrannosauroids.