Opisthias rarus

Opisthias skull
Any specimen this tiny is usually poorly preserved, if at all. Although less than an inch long, this skull shows great detail. Scale bar is 1 inch.
CT scan of Opisthias skull
CT scans allow paleontologists to see specimens in spectacular detail. This is the same Opisthias skull in the above photo.

About Opisthias rarus:

Opisthias rarus is a lizard-like reptile that reached a length of a foot or more. It is not a true lizard but a sphenodont. The last living sphenodont is the tuatara of New Zealand, which helps us understand how Jurassic sphenodonts might have lived. The living tuatara eats insects, worms, snails, slugs, spiders, lizards, young birds, and eggs.

CT Scan of inderside of Opisthias skull
CT scans can produce an image even through rock. This side of the specimen is still contained in the rock but details can be seen because of the CT scans.

Why is Opisthias rarus a superstar?

Sphenodonts, like other microvertebrates, have extremely fragile and delicate bones. In spite of this, several extremely well preserved skulls have been preserved at the Monument. Scientists are now using CT scans to study these specimens. The resulting high resolution images make it possible to research the bones in great detail with less risk of damaging them. It also allows them to see bones that are still buried in the rock.


Jurassic Fact: Sphenodonts are common reptile fossils in terrestrial Mesozoic rock (Age of Dinosaurs). After this time they disappeared from the fossil record everywhere but New Zealand.

For more information: Visit the Quarry Exhibit Hall where a cast is on display.

Last updated: February 24, 2015

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