Poekilopleuron

*Poekilopleuron bucklandi*

***Poekilopleuron*** (meaning "various ribs") is an extinct genus of large basal tetanuran theropod dinosaur, perhaps belonging to the clade Allosauroidea. It grew 30 feet in length and weighed 1 ton in mass. The genus comes from the Middle Jurassic (Bathonian stage) of France, about 168 to 165 million years ago.

## Fossils

*Poekilopleuron* is known from a partial skeleton discovered by Jacques Amand Eudes-Deslongchamps in July 1835 near La Maladrerie in Normandy, France, in a layer of the Calcaire de Caen Formation. This skeleton, part of the collection Musee de la Falcutee des Sciences de Caen, was in 1944 destroyed during the Battle of Caen in World War 2, and the taxon has since had to be studied on the basis of cast replicas. One set is present in the Museum National d'Histoire Naturelle in Paris with inventory number MNHN 1897-2, a second in the Yale Peabody Museum, YPM 4938. The remains consisted of caudal vertebrae, cervical ribs, ribs, belly ribs (gastralia), a forelimb and a hindlimb.

## Discovery and naming

*Poekilopleuron* is a genus of theropod with a long and complex history. The genus was first named and described by Jacques Amand Eudes-Deslongchamps in 1838, based on holotype material that is now destroyed. The holotype, which was housed in Musée de la Faculté des Sciences de Caen and destroyed during World War II, included gastralia, phalanges, a left forelimb, caudal vertebrae, chevrons, ribs and a hindlimb. Of all the material, few is still preserved, although the gastralia, phalanges and forelimb were casted and now represent the plastotype, with casts in the Muséum National d'Histoire Naturelle (specimen MNHN 1897-2) and Yale Peabody Museum (specimen YPM 4938). The original material was uncovered in a layer of the Calcaire de Caen in Normandy, France. *Poekilopleuron* can be assigned to the middle Bathonian in age, about 167.7 to 164.7 million years ago.

In the same 1838 publication, Eudes-Deslongchamps also named the type species of *Poekilopleuron*, *P. bucklandii*. Eudes-Deslongchapms noted similarities with some material of *Megalosaurus bucklandii* and *Poekilopleuron*, and chose the species name *bucklandii* for *Poekilopleuron*, so that it the two genera were synonymized, only the genus name would be suppressed.[1] The generic name is derived from Greek ποίκιλος, poikilos, "varied", and πλευρών, pleuron, "rib", a reference to the three types of rib present. The specific name, honouring William Buckland, was deliberately identical to that of *Megalosaurus bucklandii*.

## Description

The most distinctive feature of *Poekilopleuron* were its forelimbs. Their length, about 2 feet long, was a sign of this theropod's more original build. Unlike later Theropoda, whose forelimbs tened toward reduction in length in proportion to the animal's body size, Poekilopleuron's arms were long and, by implication, potent. The length mostly resided in the elongated but powerfully muscled humerus. The antebrachia (forearms) were markedly short and robust, a characteristic shared with Poekilopleuron's slightly larger and considerably American cousin Torvosaurus. A unique feature is the lack of the olecranon process on the ulna. It had a relatively similar physical appearance compared to a featherless raptor.

The fossil of *Poekilopleuron* showed a rare set of gastralia: fourteen pairs of belly ribs supported the body of the animal.

## Classification

*Poekilopleuron* is a hard taxon to classify, as its original material is lost, and few casts are known. *Poekilopleuron* has a history of being renamed under different species and genera, most of which are now its junior synonyms.

Eudes-Deslongchamps named the type species ***Poekilopleuron bucklandii*** in 1837 or 1838. The generic name comes from the Greek poikilos, "varied" or "various", and pleuron, "side" or "rib". The name describes the three types of rib present. The only known species, *P.bucklandii*, honoring William Buckland, is very identical to that of Megalosaurus *bucklandii*. Eudes-Deslongchamps thought the specimen might well be proven to belong to this earlier named species; if so, merely the generic name would have to be changed. Indeed, following 1879, Poekilopleuron was often subsumed under *Megalosaurus bucklandii*. Eudes-Deslongchamps' choice caused problems however, when Friedrich von Huene in 1923 concluded it was part of Megalosaurus but as a seperate species within that genus. As both species carried the same epithet bucklandii, they could no longer be distinguished. Von Huene therefore renamed the species into *Megalosaurus poekilopleuron*. Most later authors continued using the generic name Poekilopleuron.

Another problem was caused by the fact that the name was only partially latinised. In correct Greek it would have been
"poikilopleuron", in Latin "poecilopleurum". This induced later writers to improve the spelling, leading to such variants such as Poecilopleuron and Poikilopleuron (still used as late as 2006). However, the original
name has priority and is valid.

Five other species would be named in the genus. In 1869 Edward Drinker Cope renamed Laelaps *gallicus* into Poekilopleuron gallicum. In 1870 Joseph Leidy created a Poicilopleuron valens based on a fossil probably belonging to an Allosaurus. In 1876 Richard Owen named a Poikilopleuron pusillus, in 1879 renamed by Cope to Poekilopleuron minor, in 1887 Harry Govier Seeley made it a seperate genus: Aristosuchus. In 1883 W.A. Kiprijanow created a Poekilopleuron schmidti, of which the specific name honors Friedrich Schmidt, based on some indeterminate ribs and a sauropod metatarsal. This chimera is a nomen dubium. A much later named species is Poekilopleuron valesdunensis created by Ronan Allain in 2002. In 2005 it was renamed Dubreuillosaurus *valesdunensis*.

Because the original fossil was destroyed and no other remains of *Poekilopleuron* have since been found, and also because of its name change, there is much controversy surrounding its classification that cannot be resolved.

## JPInstitute.com Description

Poekilopleuron was found in 1838, making it one of the first dinosaurs ever discovered in Europe. Unfortunately, no one will ever see or study the original fossils of this large, ferocious meat-eater, as they were destroyed during WWII when bombs leveled the museum in which they were stored. Some scientists think that it may be the same dinosaur as Megalosaurus, but it will be impossible to know for sure unless other fossils are uncovered that are the same as the originals.

With no specimen available for a reliable evaluation using contemporary analysis techniques, the questions and debates surrounding Poekilopleuron may never be resolved. A specimen from the former Soviet Union was initially described as a species of this dinosaur, but that classification is considered invalid by most scientists.

## Links

https://web.archive.org/web/20030405122502/http://www.jpinstitute.com/dinopedia/dinocards/dc\_poeki.html