Dilophosaurus: the two-crested hunter of Early Jurassic Arizona

Dilophosaurus wetherilli was a large theropod of the Early Jurassic Kayenta Formation in what is now northern Arizona. Several partial skeletons preserve skulls, vertebrae, the shoulder girdle and both pairs of limbs. They show a two-crested predator roughly 6 to 7 metres long, not the small, venom-spitting animal familiar from fiction.

The bones were damaged and later museum mounts included plaster restorations, so older accounts underestimated the strength of its skull and arms. A detailed 2020 redescription separated fossil bone from repair and revised the anatomy of the best-known specimens. It did not turn every detail of the living animal into a certainty: the display role of the crests is inferred, and the exact prey, skin covering and social life remain unknown.

Quick facts

Name and changing interpretation

Dilophosaurus combines Greek words for “two”, “crest” and “lizard”. The species name wetherilli honours John Wetherill, a member of a family active in exploration of the American Southwest and a consultant to expeditions. The name describes the paired bony ridges on the skull; it does not imply that the animal's soft-tissue crest looked exactly like a modern bird's comb.

Samuel Welles first named the animal Megalosaurus wetherilli in 1954. The early skulls were crushed, and their crests were not yet understood. After Welles found a larger partial skeleton with clearer crests in 1964, he established the genus Dilophosaurus in 1970. That history explains why the genus once appeared under more than one name in older books.

Discovery, specimens and preparation

The first major remains were found in 1940 on Navajo Nation land in northern Arizona. Jesse Williams, a Navajo resident, showed the locality to the University of California expedition. The team collected two principal individuals and remains of a third. One became the holotype and another the paratype. The exact field history matters: the fossils came from a real community and landscape, not from a fictional “dinosaur valley”.

The skulls had been compressed, and some missing sections were filled in plaster during preparation. For years, mounts mixed original bone with restoration based on other theropods. The additional individual collected by Welles in 1964 established that the paired crests were anatomical structures rather than a result of crushing. Two more incomplete skeletons were recovered from the Kayenta Formation late in the twentieth century.

In 2020, Adam Marsh and Timothy Rowe redescribed the five principal specimens. They distinguished genuine fossils from old repairs and compared the skull, shoulder and limbs in detail. The sample is unusually informative for a large Early Jurassic theropod, but no specimen is a complete skeleton. Individual differences and growth stage also matter when separate bones are compared.

Classification and relatives

Dilophosaurus is a neotheropod, within the theropod branch of dinosaurs. The 2020 analysis did not support older placements among coelophysoids or ceratosaurs. It instead placed the genus near the base of Averostra, the branch that includes ceratosaurs and tetanurans. Early theropods combine features that evolved at different rates, so the exact position may shift among analyses.

The only currently recognised species is D. wetherilli. Material once called Dilophosaurus sinensis is assigned to the separate genus Sinosaurus. These names do not describe two established species of one genus. The wider branching pattern can be followed in the dinosaur classification guide; Dilophosaurus itself sits among other named dinosaurs in the dinosaur catalogue.

What the skeleton preserves

The known material includes parts of the upper and lower jaws, teeth, neck and back vertebrae, the sacrum and tail, gastralia, the shoulder girdle, forelimbs, pelvis, hind limbs and feet. The five principal individuals differ in size and completeness. The 2020 redescription treated them as one species and interpreted much of the variation as individual or age-related rather than evidence for several genera.

No single animal preserves every region. Crushed skulls and incomplete tails leave room for reconstruction, and a museum mount may combine bones from more than one individual. The best guide is to distinguish the element actually found from the restored position of a missing piece. That distinction is especially important for the skull, where plaster once affected how the animal's mechanics were understood.

Size and skull crests

Large individuals are estimated at about 6 to 7 metres long and roughly 300 to 500 kilograms. These are reconstructions, not direct measurements. Missing tail vertebrae, the reconstructed trunk, the age of each specimen, muscle volume and the body model all affect the result. Even so, Dilophosaurus was much larger than a dog-sized movie animal and among the largest known land predators in its Early Jurassic region.

The skull was long and low relative to the trunk. Two ridges ran along its upper surface, built from several bones including the nasals and lacrimals. The crests were thin, pneumatic and vertically expanded, extending back beyond the eye region. They were poorly suited to blows. A covering of keratin could have enlarged their outline in life, but no soft-tissue impression establishes its exact shape or colour.

Visual display or recognition is a plausible role for the crests. A signal of maturity or individual identity is also possible. The fossils do not show that the crests differed between sexes or were used in courtship. Those functions remain interpretations of anatomy rather than direct observations.

Jaws, teeth and feeding mechanics

The premaxilla carried four tooth positions and the maxilla about twelve. A gap separated the front and rear parts of the upper tooth row. Earlier researchers interpreted the connection between the premaxilla and maxilla as weak and concluded that the jaws could not handle large prey. The revised skull shows a more complex, reinforced connection and support system. That changes the mechanical picture, although it does not measure bite force directly.

The teeth were long, recurved and serrated, suited to puncturing and cutting soft tissue rather than repeatedly crushing thick bone. This supports a carnivorous diet but does not provide a precise menu. The jaw and neck could seize prey and remove tissue; the fossil record does not preserve a complete hunting sequence.

In one Kayenta locality, a sauropodomorph skeleton preserves large bite marks and shed teeth were found nearby, together with a Dilophosaurus skeleton. This is evidence that a large sauropodomorph carcass was fed upon by a theropod of this kind. It cannot determine whether the animal was killed by the predator or eaten after death. Fish may also have been available, but the anatomy does not identify Dilophosaurus as a specialised fish eater.

Strong forelimbs and bipedal movement

The forelimbs were well developed, with the humerus about half the length of the femur. The hand had four digits, three functional and a strongly reduced fourth. The first two carried large claws. The palm faced inward, and the fingers could spread and extend, though the wrist could not rotate freely into a human-like palm-down position. Joint surfaces constrain movement without preserving the muscles and tendons themselves.

Range-of-motion studies suggest the arms could grasp and manipulate prey. They were strong relative to those of later large theropods, but an exact behaviour cannot be read from their shape. A healed pathology on one forelimb is evidence of injury and recovery in one individual, not a normal asymmetry shared by the genus.

The hind limbs supported a bipedal gait. The tibia was about as long as the femur, and the foot had three main weight-bearing toes plus a reduced first digit. Proportions suggest a mobile terrestrial predator, but they do not yield a defensible top speed. Long tails counterbalanced the trunk and head. Tracks such as Eubrontes and Kayentapus are footprint types, not skeletal genera; no trackway can be assigned confidently to this animal alone.

Kayenta habitat and neighbouring fauna

The Kayenta Formation records rivers and floodplains under a seasonally dry climate. Wet patches and temporary water bodies occurred alongside sandy areas; later Navajo Sandstone dunes developed in the broader region. It was not a lifeless desert like the modern Sahara. The age of a particular fossil-bearing level should not be confused with the full span of the formation.

Other Kayenta animals included the sauropodomorph Sarahsaurus, smaller theropods, the scutellosaurid Scutellosaurus, turtles, early crocodylomorphs, amphibians, pterosaurs, synapsids and early mammals. Their presence provides an ecological setting, but finding two genera in one formation does not demonstrate a direct predator-prey relationship. More context is available in the page on the Jurassic Period.

Behaviour, covering and popular errors

No direct evidence establishes pack hunting, family groups, territoriality or parental care. Several individuals from different levels of a formation are not proof that a permanent pack lived together. The crest was probably visible in life, but the display it served and its colour are unknown.

No skin or feather impressions are known for Dilophosaurus. Reconstructions usually show a mainly scaly covering, as is common for large early neotheropods, while the absence of impressions cannot prove that every part of the skin was bare. A cautious image keeps the bony crest and skeleton distinct from invented soft tissue.

The venomous spit and folding neck frill are fictional. No skull, tooth or other fossil shows a venom gland or apparatus for spitting. The animal was not tiny, its crests were not weapons, and all large Early Jurassic footprints cannot be assigned to it. These corrections follow from the fossil evidence, not from a more spectacular alternative story.

Why Dilophosaurus matters

Dilophosaurus is one of the best-studied large theropods from the Early Jurassic. Its specimens help researchers examine how large predators developed after the Triassic, how early neotheropod skulls and limbs were built, and how pneumatic anatomy and display structures varied. The revised preparation also shows why old restorations must be separated from original bone before anatomy is inferred.

Its evidence is substantial but bounded: five partial skeletons illuminate much of the animal, while diet, speed, skin covering and social behaviour remain less certain. The important change since early reconstructions is not a new fictional power but a more robust, more anatomically complex predator.