Dilophosaurus
From Greek di- (two) + lophos (crest) + sauros (lizard): 'two-crested lizard', referring to the pair of bony crests on its skull.
Dilophosaurus is a genus of theropod dinosaurs that lived in what is now North America during the Early Jurassic, about 186 million years ago. Three skeletons were discovered in northern Arizona in 1940, and the two best preserved were collected in 1942. The most complete specimen became the holotype of a new species in the genus Megalosaurus, named M. wetherilli by Samuel P. Welles in 1954. Welles found a larger skeleton in the same region belonging to the same species in 1964. Realizing it bore crests on its skull, Welles assigned the species to the new genus Dilophosaurus in 1970, as Dilophosaurus wetherilli. The genus name means "two-crested lizard", and the species name honors John Wetherill, an explorer and amateur archeologist. Further specimens have since been found, including an infant. Fossil footprints have also been attributed to the animal, including resting traces. Another species, Dilophosaurus sinensis from China, was named in 1993, but was later found to belong to the genus Sinosaurus.
Diagnosis
- Pair of parasagittal nasolacrimal crests, each formed by a ridge on the dorsolateral margin of the nasal process of the premaxilla, dorsolateral expansions of the nasal and lacrimal, and a posteriorly projecting process of the lacrimal behind the orbit.
- Pyramidal process on the lateral surface of the surangular, anterior to the articulation with the quadrate.
- Mandibular fenestra reduced in anteroposterior length.
- Neural spines of the post-axial cervical vertebrae with a dorsal margin stepped in lateral view — anterior and posterior 'shoulders' flanking a taller central 'cap' that is cruciform in dorsal view, most pronounced in the posterior cervicals.
- Serial variation (bifurcation and recombination) in the posterior centrodiapophyseal laminae of the cervical vertebrae.
- Accessory laminae emanating from the anterior and posterior centrodiapophyseal laminae of the middle trunk vertebrae.
- First primordial sacral rib articulating with the preacetabular process of the ilium.
- Additional 'horizontal buttress' on the posteroventral part of the coracoid, next to the biceps tuber.
Species
Dilophosaurus wetherilli Welles, 1970
Type species
Named for John Wetherill, an explorer, friend of scientists, and trusted trader whose nephew Milton first informed the expedition of the fossils.
- Holotype
- UCMP 37302 , University of California Museum of Paleontology
- Material
- Skeletally immature individual: partial skull (articulated right side, braincase, mandible fragments), presacral, sacral, and 38 caudal vertebrae, both forelimbs, partial pectoral and pelvic girdles, hindlimb elements, and nearly complete pedes.
- Horizon
- lower Kayenta Formation, Hettangian–Pliensbachian, Early Jurassic , 201.4–184.2 million years ago
- Locality
- UCMP V4214, Moa Ave 1, Arizona, United States
Notable specimens
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UCMP 77270
University of California Museum of Paleontology Found 1964 by Samuel P. Welles complementary
Adult referred skeleton found in 1964, about one-third larger than the type juveniles. Its preserved skull crests revealed the animal bore paired crests, prompting Welles to erect the new genus Dilophosaurus; it remains the only specimen preserving much of the crests.
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MNA P1.3181
Museum of Northern Arizona Found 1978 ontogeny
Infant specimen found in 1978 in the Rock Head Quadrangle, the youngest known example of the genus and one of the earliest known infant theropods from North America, preceded only by some Coelophysis specimens. It includes a partial humerus, a partial fibula, and a tooth fragment.
References
- Welles, S. P. (1970). Dilophosaurus (Reptilia: Saurischia), a new name for a dinosaur. Journal of Paleontology 44(5): 989. welles1970a
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Paul, G. S. (2024). The Princeton Field Guide to Dinosaurs (3rd ed.). Princeton University Press.
Source of the appearance features.
paul2024a - Marsh, A. D.; Rowe, T. B. (2020). A comprehensive anatomical and phylogenetic evaluation of Dilophosaurus wetherilli (Dinosauria, Theropoda) with descriptions of new specimens from the Kayenta Formation of northern Arizona. Journal of Paleontology 94(S78): 1-103. doi:10.1017/jpa.2020.14 marsh2020a
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Gay, R. (2001). New specimens of Dilophosaurus wetherilli (Dinosauria: Theropoda) from the early Jurassic Kayenta Formation of northern Arizona. Western Association of Vertebrate Paleontologists Annual Meeting 1: 1.
Annual meeting abstract, Mesa, Arizona.
gay2001a