Callovosaurus
- Oxford Clay Formation ( England)
Callovosaurus leedsi ( Lydekker, 1889)
Callovosaurus is an extinct genus of Iguanodontia from the group ornithopods. Fossils were found in the Oxford Clay Formation near Peterborough in England and have been dated to the early Late Jurassic.
The first and only Fund ( holotype ) consists of a femur ( thigh bone), which is almost complete, but broken into three parts. The only way Callovosaurus leedsi, was first described by Richard Lydekker in 1889 Camptosaurus leedsi. In 1980 it was then assumed by Peter Galton the new genus Callovosaurus.
The original description of the femur of Callovosaurus was short. Even if the femur has never been described in detail, it was a length of 28 cm can be measured, so it is assumed that the whole animal was about 2.5 m long ( Galton, 1980a ). Since Callovosaurus is only known from a femur, can be detected only in this unique features ( autapomorphies ). The lesser trochanter (small trochanter ) is separated, for example, from the greater trochanter ( great trochanter ) by a wide and deep chasm and its proximal end is below the tip of the greater trochanter.
The systematic classification has long been considered controversial:
Callovosaurus initially was considered to be part of the Hypsilophodontidae. Later they asked this genus as relatives of Camptosaurus in the Camptosauridae.
However, many of the features of the femur of Callovosaurus speak for classification in the Dryosauridae, whereby the above- mentioned gap between the lesser trochanter and the greater trochanter also in the genera Dryosaurus and Valdosaurus is present, which count as secure members of the Dryosauridae. So Callovosaurus is probably closer to these two genera used as example with Hypsilophodon or Camptosaurus, which Callovosaurus is the oldest Dryosauridae that has ever been found. The following cladogram by Barret et al. (2011), the relationships of Callovosaurus within the Dryosauridae is:
Callovosaurus
Kangnasaurus
Dryosaurus
Valdosaurus
Elrhazosaurus