Eustreptospondylus

Did You Know?

• The specific name 'oxoniensis' refers to its provenance from Oxford.
• The holotype specimen was not fully grown, representing a subadult.

Discovery and naming

In 1870, workers at the Summertown Brick Pit near Oxford uncovered a theropod skeleton. Local bookseller James Parker acquired the remains and alerted Oxford professor John Phillips, who described the bones in 1871 without naming them. At that time, it was the most complete large theropod skeleton ever found, and it remains the most complete large Jurassic European theropod. In 1890, Oxford University purchased the skeleton, and Arthur Smith Woodward examined it, assigning it to Megalosaurus bucklandii. In 1905 and 1906, Baron Franz Nopcsa reassigned it to Streptospondylus cuvieri, a species based on a lost vertebra described by Richard Owen in 1842. Nopcsa placed all British material under that species, but the assignment of a complete find to a poorly known species was problematic. German palaeontologist Friedrich von Huene sometimes referred to the specimen as Streptospondylus cuvieri and sometimes as Megalosaurus cuvieri. In 1964, Alick Donald Walker clarified matters by erecting the new genus and species Eustreptospondylus oxoniensis, meaning 'true Streptospondylus' from Oxford.

Description

The main specimen of Eustreptospondylus was not fully grown; Paul in 1988 estimated it at about 4.63 m long and 218 kg. Hypothetical adult length is around 6 m with a mass of 0.5 t. The skull has a pointed snout with a large horizontal nostril and no lacrimal horn, and the skull roof is relatively thick. Oblique grooves in the jaw joints widened the gape when the lower jaws opened. The front of the jaws is tall and wide; no teeth are preserved, but tooth sockets indicate the third lower jaw tooth was enlarged. The front dorsal vertebrae have paired hypapophyses on their undersides, though they are not keeled. Sadleir et al. in 2008 identified distinguishing traits: a shallow depression with a small foramen in the lacrimal corner, a groove on the descending branch of the postorbital, a drooping flange on the squamosal covering part of the temporal fenestra, and a depression on the tenth neck vertebra. In 2012, Matthew Carrano added that the ilium's pubic peduncle is as wide transversely as long, and the rear blade of the ilium has a brevis shelf for tail muscle attachment.

Paleobiology

Eustreptospondylus likely fed on smaller dinosaurs and pterosaurs or scavenged carcasses of fishes, marine reptiles, and other dinosaurs. It may have foraged on shorelines. The fossil was found on what was then an island, suggesting it could swim short distances, possibly like the modern Komodo dragon. Some palaeontologists disagree, proposing the carcass was swept out to sea after death. The idea that it evolved insular dwarfism arose because the holotype was a subadult, not a dwarf adult.