Dilophosaurus

Dinosaurs > Dilophosaurus

Dilophosaurus is a genus of theropod dinosaur from the Sinemurian stage of the Early Jurassic Period, about 193 million years ago. The first specimens were described in 1954, but it was not until over a decade later that the genus received its current name.

Dilophosaurus measured around 7 metres (23 ft) long and may have weighed 500 kilograms (1,100 lb).

The most distinctive characteristic of Dilophosaurus is the pair of rounded crests on its skull, made up of extensions of the nasal and lacrimal bones. These are considered to be too delicate for anything but display purposes. Dodson (1997) noted that cranial crests first appear in Dilophosaurus and later in other theropods.

The teeth of Dilophosaurus are long, but have a fairly small base and expand basally. Dilophosaurus had 12 maxillary teeth and as many as 18 dentary teeth, and the teeth were smaller in the tip of the upper jaw. The second and third front teeth feature serrations, which are absent in the fourth. Another skull feature was a notch behind the first row of teeth, giving Dilophosaurus an almost crocodile-like appearance, similar to the putatively piscivorous spinosaurid dinosaurs. This “notch” existed by virtue of a weak connection between the premaxillary and maxillary bones of the skull. The braincase is well known in Dilophosaurus, and is significant in that it bears a feature of the top side wall that is absent in ceratosaurians. Compared with ceratosaurians, the distal scapular expansion in D. wetherilli is uniquely rectangular. The upper leg bone (femur) is longer than the lower leg (tibia).

The crests on the skull of Dilophosaurus are considered to be cranial ornamentation for use in attracting mates. Padian, Horner and Dhaliwal (2004) challenged conventional hypotheses that the purpose of bizarre cranial structures and post-cranial armor in dinosaurs, was either for attracting mates, intimidating/fighting rivals in the group, or intimidating potential predators of other species. Padian et al. noted that based on phylogenetic, histological, and functional evidence these bizarre structures can be explained by the phenomenon of intra-species recognition, which is supported by the fossil evidence.

Dilophosaurus

Clade: Dinosauria
Suborder: Theropoda
Family: Dilophosauridae

Size: 7 m (23 ft) long

Weight: 500 kg (1,100 lb)

When: Jurassic Period
193 million years ago

Where: North America

Diet: Carnivore

Dilophosaurus is considered to have been an obligate biped based on the presence of long hindlimbs oriented vertically under the pelvis, and short forelimbs that did not support quadrupedal locomotion. The hindlimbs suggest a fast and agile runner, as would be expected in a carnivorous theropod.

Welles (1984) proposed that Dilophosaurus traveled in small groups, based on the fact that several individuals were found together. Gay (2001b) noted that there was no direct evidence for this and noted that “flash floods would pick up scattered and isolated material from different individuals and deposit them together in the same area.” Cranial display features make sense in social, gregarious animals, where other members of the species are available to observe and interpret messages of sexual status.

The presence and distribution of non-interdigitating sutures in the skull of some reptilian groups, including Dilophosaurus, has been interpreted as indicating the presence of a system of levers, driven by jaw muscles, as an aid to predation. Welles (1984) rejected this hypothesis and interpreted the potential mobility in the skull of Dilophosaurus as a sign of weakness, and argued that the loose connection of the premaxilla precluded the capture and subduing of prey. This led to the early hypothesis that Dilophosaurus scavenged off carrion, because its teeth were too weak to bring down large prey.


Source: Wikipedia