Lurdusaurus
Lurdusaurus ('heavy lizard') is a genus of large ornithopod dinosaur that lived in the Aptian stage of the Early Cretaceous, sometime between 121 to 112 million years ago.
Etymology[]
The generic name is derived from the Latin lurdus, "heavy" while the specific name of the type species, arenatus means "sandy", being a reference to the Tenere desert.
Discovery[]
In 1965 Philippe Taquet discovered the remains of an ornithopod in rock layers of the Elrhaz Formation, in the Tenere desert of Niger, it consists of a partial skeleton with a fragmentary skull belonging to single individual which was given the catalogue number GDF 1700, the remains sat undescribed until 1988 when paleontologist Souad Chabli coined the name "Gravisaurus tenerensis" in her unpublished dissertation on the animal, however since the name was never published it is invalid, the remains were later briefly described and formally given the name Lurdusaurus arenatus by Taquet and Dale Russell in 1999, a name with similar etymology to "Gravisaurus tenerensis".
Description[]
The tip of the snout may have been about 20 cm (7.9 in) wide, and expanded back to 30 cm (1 ft). That is, like other iguanodonts, it did not have a duck-like bill. No teeth were preserved, but MNHN GDF 43G preserves the tooth sockets for 10 tooth rows within 19.5 cm (7.7 in). The quadrate bone at the base of the skull has an exceptionally low stature at 28.2 cm (11.1 in), in contrast to 489 mm (1 ft 7 in) in Mantellisaurus and 37.6 cm (1 ft 3 in) in Iguanodon. Based on the ratio between the length of the snout and the length of the rest of the skull in iguanodonts, the total length of the holotype's skull may have been 83.3 cm (2 ft 9 in) in life.
Lurdusaurus may have had 12 to 14 neck vertebrae. Therefore, the maximum length of the neck is 1.6 m (5 ft 3 in). The neck vertebrae are about the same size as the dorsal vertebrae (the torso, before the sacrum and pelvis), whereas those of European iguanodonts 85–90% the size of the dorsals. Because Iguanodon has 28 presacral vertebrae, Lurdusaurus potentially had at least 14 dorsals. This would make the neck proportionally quite long, as long as the dorsal series. Compared to European iguanodonts, the dorsal centra are proportionally larger and have shorter neural spines (which project straight up from the centrum) and less steep transverse processes (which project up obliquely).Like all derived iguanodonts, the sternum is hatchet-shaped, with a rod-shaped projection caudolaterally (tailwards towards the side). The sacrum, based on the scars on the ilium begotten from sacral ribs, may have measured 60 cm (2 ft). Lurdusauruscould have had 15 proximal caudal vertebra(tail vertebrae which bear transverse processes), which would have represented a third of the entire tail series.
This would equate to a 4 m (13 ft) tail, and a total body length of 9 m (30 ft). It may have been 2 m (6.6 ft) tall at the hips. Based on the length of the ribs, the stomach may have been less than 70 cm (2 ft 4 in) off the ground when standing quadrupedally (on all-fours). Based on the circumferences of the limbs – 29.5 cm (1 ft) for the humerus and 45.7 cm (1 ft 6 in) for the femur – Taquet and Russell estimated that the holotype weighed approximately 5.5 t (6.1 short tons), conspicuously heavy for an ornithopod this size. In 2016, however, Gregory S. Paul proposed a significantly lower size estimate of 7 m (23 ft) in length and 2.5 t (2.8 short tons) in body mass. The headward dorsal ribs are preserved in their original positions, and show the torso was rather rotund. The diverging wings of the ilia and horizontally-orientated tailward dorsal ribs indicate a flat back about 1 m (3 ft 3 in) across.
The limbs are exceptionally massive and proportionally stout. The forelimbs are 60% the size of the hindlimbs. The metacarpalsin the wrist were fused together into a massive block, which is also exhibited in Iguanodon, Ouranosaurus, and Camptosaurus. Like Camptosaurus but unlike derived iguanodonts, the metacarpals (except for the thumb) were short and dumbbell-like as opposed to long and narrow. Compared to Camptosaurus, the unguals (claws) are flatter. The hand features a massive thumb spike. The pelvis is proportionally short but powerful, somewhat reminiscent of a ceratopsian pelvis. The femur slightly recurves toward the midline like in ceratopsians, and is flattened anteroposteriorly (from front to back) like in sauropods. The heavily built fourth trochanter is located on the bottom half of the femur, like Iguanodon but unlike Mantellisaurus and Ouranosaurus. The tibia is incredibly short relative to the femur, respectively 77.7 cm (2 ft 7 in) vs. 91 cm (3 ft 0 in). The metatarsals were too short to make contact with each other, and there was likely a fleshy pad to support the weight.