Famous 'Jurassic Park' dinosaur is less lizard, more bird

Date:
July 7, 2020
Source:
University of Texas at Austin
Summary:
From movies to museum exhibits, the dinosaur Dilophosaurus is no
stranger to pop culture. Many probably remember it best from the
movie 'Jurassic Park,' where it's depicted as a venom-spitting beast
with a rattling frill around its neck and two paddle-like crests
on its head. But a new comprehensive analysis of Dilophosaurus
fossils is helping to set the record straight, finding that the
Dilophosaurus was actually the largest land animal of its time.



FULL STORY ==========================================================================
From movies to museum exhibits, the dinosaur Dilophosaurus is no stranger
to pop culture. Many probably remember it best from the movie "Jurassic
Park," where it's depicted as a venom-spitting beast with a rattling
frill around its neck and two paddle-like crests on its head.


==========================================================================
The dinosaur in the movie is mostly imagination, but a new comprehensive analysis of Dilophosaurus fossils is helping to set the record
straight. Far from the small lizard-like dinosaur in the movies, the
actual Dilophosaurus was the largest land animal of its time, reaching
up to 20 feet in length, and it had much in common with modern birds.

The analysis was published open access in the Journal of Paleontology
on July 7.

Dilophosaurus lived 183 million years ago during the Early
Jurassic. Despite big-screen fame, scientists knew surprisingly little
about how the dinosaur looked or fit into the family tree, until now.

"It's pretty much the best, worst-known dinosaur," said lead author
Adam Marsh.

"Until this study, nobody knew what Dilophosaurus looked like or how
it evolved." Seeking answers to these questions, Marsh conducted an
analysis of the five most-complete Dilophosaurus specimens while earning
his Ph.D. from The University of Texas at Austin's Jackson School of Geosciences. He is now the lead paleontologist at Petrified Forest
National Park.



==========================================================================
The analysis is co-authored by Jackson School Professor Timothy Rowe,
who discovered two of the five Dilophosaurus specimens that were studied.

The study adds clarity to a muddled research record that reaches back to
the first Dilophosaurus fossil to be discovered, the specimen that set
the standard for all following Dilophosaurus discoveries. That fossil
was rebuilt with plaster, but the 1954 paper describing the find isn't
clear about what was reconstructed -- a fact that makes it difficult
to determine how much of the early work was based on the actual fossil
record, Marsh said.

Early descriptions characterize the dinosaur as having a fragile crest and
weak jaws, a description that influenced the depiction of Dilophosaurus
in the "Jurassic Park" book and movie as a svelte dinosaur that subdued
its prey with venom.

But Marsh found the opposite. The jawbones show signs of serving as
scaffolding for powerful muscles. He also found that some bones were
mottled with air pockets, which would have helped reinforce the skeleton, including its dual crest.

"They're kind of like bubble wrap -- the bone is protected and
strengthened," Marsh said.



========================================================================== These air sacs are not unique to Dilophosaurus. Modern birds and the
world's most massive dinosaurs also have bones filled with air. In both
cases, the air sacs lighten the load, which helped big dinosaurs manage
their bulky bodies and birds take to the skies.

Many birds use the air sacs to perform other functions, from inflating
stretchy areas of skin during mating rituals, to creating booming calls
and dispersing heat. The intricate array of air pockets and ducts that
extend from Dilophosaurus' sinus cavity into its crests means that the
dinosaur may have been able to perform similar feats with its headgear.

All the specimens Marsh examined came from the Kayenta Formation in
Arizona and belong to the Navajo Nation. The University of California
Museum of Paleontology holds in trust three of the specimens. The Jackson School Museum of Earth History holds the two discovered by Rowe.

"One of the most important responsibilities of our museum is
curation," said Matthew Brown, director of the Vertebrate Paleontology Collections. "We are very excited to help share these iconic Navajo
Nation fossils with the world through research and educational outreach,
as well as preserve them for future generations." To learn more about
how the fossils compared with one another, Marsh recorded hundreds of anatomical characteristics of each fossil. He then used an algorithm to
see how the specimens compared with the first fossil -- which confirmed
that they were indeed all Dilophosaurus.

The algorithm also revealed that there's a significant evolutionary gap
between Dilophosaurus and its closest dinosaur relatives, which indicates
there are probably many other relatives yet to be discovered.

The revised Dilophosaurus record will help paleontologists better identify specimens going forward. Marsh said that the research is already being
put into action. In the midst of his analysis, he discovered that a small braincase in the Jackson School's collections belonged to a Dilophosaurus.

"We realized that it wasn't a new type of dinosaur, but a juvenile Dilophosaurus, which is really cool," Marsh said.


========================================================================== Story Source: Materials provided by University_of_Texas_at_Austin. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Adam D. Marsh, Timothy B. Rowe. 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, 2020; 94
(S78): 1 DOI: 10.1017/jpa.2020.14 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200707183920.htm

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