Eustreptospondylus

***Eustreptospondylus*** (meaning "true reversed vertebra") is a genus of megalosaurid, from the Oxfordian stage of the Late Jurassic period (some time between 163 and 154 million years ago) in southern England, at a time when Europe was a series of scattered islands (due to tectonic movement at the time which raised the sea-bed and flooded the lowland).

## Description

The main specimen of *Eustreptospondylus* was not fully grown, and according to an estimate by Paul in 1988 was about 4.63 metres (15.2 ft) long and weighed about 218 kilograms (481 lb). Various estimates suggest that *Eustreptospondylus* was an "average-sized" theropod, with a hypothetical adult length of around 6 metres (20 ft), and a mass of 0.5 tonnes (0.49 long tons; 0.55 short tons).

The skull of *Eustreptospondylus* has a rather pointed snout in side view, with a large horizontally oriented nostril. There is no lacrimal horn. The skull roof is relatively thick. Oblique grooves in the jaw joints caused the gape of the mouth to be widened when the lower jaws were opened. These jaws at the front are rather tall and wide. No teeth have been preserved in either the upper or lower jaws, but the size of its toothsockets proves that the third tooth of the lower jaw was enlarged. Though not keeled, the front dorsal vertebrae have paired hypapophyses at their undersides, just as with *Streptospondylus altdorfensis*.

### Distinguishing Anatomical Features

Sadleir et al. (2008) established several traits that distinguish *Eustreptospondylus* from its direct relatives. In the corner of the lacrimal a shallow depression is present, which is pierced by a smaller foramen. The descending branch of the postorbital has a groove in its outer rear corner. The outer side of the squamosal has a well-developed drooping flange covering, in side view, the upper rear part of the lateral temporal fenestra. The tenth neck vertebra has a clear depression on its front underside. The neck and dorsal vertebrae are not keeled. In 2012 Matthew Carrano added to these traits. The peduncle of the ilium to which the pubic bone is attached, is as transversely wide as it is long from front to rear. With the rear blade of the ilium, the lower edge of the outer blade side is turned upwards to an almost horizontal position, creating and denuding over its total length a bone surface, the "brevis shelf", forming the internal face of the inner blade side — this shelf with dinosaurs functions as an attachment area for a tail muscle, the *Musculus caudofemoralis brevis*.

Sadleir also found additional traits proving that *Eustreptospondylus* differed from *Magnosaurus nethercombensis* in more than a single detail. The interdental plates reinforcing the back of the teeth are longer from front to rear than they are tall; with *M. nethercombensis* the opposite is true. Seen from above, the pubic bone forms transversely a more narrow part of the lower rim of the hip joint. Seen from behind, the upper part of the inner side of the thighbone is straight. The cnemial crest of the upper shinbone has no ridge running to the front and below, on its outer side.

## *Eustreptospondylus* in The Amazing Dinosaur Adventure

*Eustreptospondylus* from *The Great Mountain Adventure*