Sciurum (lat.: Sciurumimus) a genus of dinosaurs of the Upper Jurassic period from the Theropoda group, which lived on the territory of modern Germany.
This genus is represented by the only known species, Sciurumimus albersdoerferi, which was first described in 2012 from an almost completely preserved fossilized skeleton of a young individual found in the Bavarian settlement of Peinten (German.: painted).
The body length of an adult sciurum may have reached several meters. At the same time, at least juveniles had plumage. The dinosaur moved like a typical theropod on its hind (lower) limbs. Sciurum is considered the basal member of the Megalosaurid family (lat.: Megalosauridae).
Anatomical features
The only known specimen of a dinosaur is the skeleton of a young animal. The length of its body is about 72 cm, and the length of the skull is about 8 cm.
These bones probably belong to a recently hatched baby. Adult animals could reach much larger sizes. For example, the body length of allosaurus cubs (lat.: Allosaurus) of comparable age was only 42 cm, that is, it was much smaller, but at the same time, adults of this dinosaur reached more than 7 meters in length. The body length of old individuals of sciurum could well reach 5 meters or more, since this genus had no prerequisites for the development of island dwarfism.
The dinosaur’s head is relatively large compared to the rest of the body and features very wide nasal openings. There are no serrations on the four front teeth of the upper jaw of the sciurumum, while the remaining upper teeth (33-35 pieces) are equipped with noticeable serrations on the back side and are strongly tilted back.
In this way, the teeth of the sciurum are noticeably different from the teeth typical of representatives of the Tetanura group (lat.: Tetanurae). One possible explanation for this is that at a certain stage in the development of tetanurs, a change of teeth occurred, as a result of which they became serrated on both sides.
The diet of young sciurums probably differed from that of adults. The large head of the found specimen of the dinosaur is distinguished by relatively large eyes and has all the signs of the so-called “childishness” inherent in the cubs of higher animals.
The skeleton of the sciurum has relatively short and strong upper limbs. The length of the three-phalangeal fingers, together with the claws, is about 45% of the total length of the upper limb. The lower limbs, on the contrary, are elongated (about 11 cm excluding foot length), as in all theropods. They allowed these dinosaurs to run fast on 2 legs. The tail is long and consists of a total of 59 vertebrae.
Around the fossil skeleton there are thin imprints and remains of feather down, which, apparently, covered the entire body of the animal. It consists of simple hair-like feathers about 0.2 mm thick and is especially strongly developed on the tail. Due to the long and dense thread-like structures of the feathers, the down resembled lush fur in its appearance.
Finding site and fossil material
The holotype of sciurum (specimen no. BMMS BK 11) was found in 2009/2010 near the settlement of Peinten in southern Germany during excavations on the territory of the Kalkwerk Rygol lime plant.
The layer of Kelheim limestone in which the find was found belongs to the Becker zone (eng.: Beckeri zone) of the Kimmeridgian stage of the Upper Jurassic. Thus, these fossils are among the best preserved dinosaur fossils, and they are about 151 million years old.
Sciurumimus albersdoerferi (“Albersdörfer’s Sciurumimus”) was described in 2012 by paleontologist Oliver Rauchut (German.: Oliver Rauhut), Christian Foth, Helmut Tischlinger and Mark Norell.: Mark A. Norell) as a new species within a monotypic genus.
Name history
The researchers made up the Latin generic name from two words: “sciurus”, t.e. “squirrel” (since the dinosaur had a magnificent tail, like a squirrel) and “mimus”, t.e. “imitating”. Thus, the name “Sciurumimus” can be translated as “squirrel-like” or “squirrel-like”. The specific epithet “albersdoerferi” was given to the new species in honor of Raimund Albersdörfer (German.: Raimund Albersdörfer), who financed the excavations.
Classification
Based on the anatomical features of the skeleton, the sciurum was classified as a very primitive member of the superfamily Megalosauroids (lat.: Megalosauroidea). At the same time, in relation to the rest of the representatives of this superfamily, it is opposed as a sister taxon.
The fact that the proto-feathers of the genus Sciurumim do not differ in their form from the down found in some ornithischian dinosaurs, such as Psittacosaurus (lat.: Psittacosaurus) indicates that theropods were not the very first dinosaurs to develop feathers.
Most likely, plumage could be the original sign of all dinosaurs and, perhaps, pterosaurs also had (lat.: Pterosauria). Therefore, this feature could be a synapomorphy (a common derived feature) of the Ornitodira group (lat.: Ornithodira).
