Excalibosaurus
Name:
Excalibosaurus
(Excalibur lizard).
Phonetic: Ecks-kal-e-boe-sore-us.
Named By: McGowan - 1986.
Classification: Chordata, Reptilia,
Ichthyosauria, Eurhinosauria, Leptopterygiidae.
Species: E. costini (type).
Diet: Piscivore.
Size: 7 meters long, skull from the back to the
tip of the snout is 1.54 meters long.
Known locations: England.
Time period: Sinemurian of the Jurassic.
Fossil representation: Two specimens, one of which
is almost complete.
The
holotype specimen of Excalibosaurus was discovered
in 1984, and
consisted of partial remains of a skull and some of the post cranial
skeleton such as ribs, vertebrae, forefin and an incomplete
pectoral girdle. When pieced together these remains recreated an
individual that was estimated to have been up to four meters long,
however this individual now seems to have been a juvenile. A second
and almost complete specimen discovered in 1996 was of a larger
seven meter long individual, a discovery which indicates that
Excalibosaurus was probably at least a medium sized
ichthyosaur.
The
features of Excalibosaurus that stands out the most
are its
asymmetrical jaws, with the rostrum of the upper jaw extending well
beyond the end of the lower jaw. It’s possible that Excalibosaurus
may have used this elongated rostrum to swipe at fish in a similar
manner as a swordfish does. This would mean that Excalibosaurus
did
not need the precision to chase a fish to the point that it could catch
it with its mouth, just get close enough to swipe it with its
rostrum. This would cause injury to the fish, inhibiting its
ability to swim away so that Excalibosaurus would
have an easier time
getting the fish into its mouth. Such behaviour might suggest a
preference for smaller fish that were too agile for other and less
specialised ichthyosaurs to catch.
Two
ichthyosaurs that are related to Excalibosaurus
are Leptonectes
from
the late Triassic, and Eurhinosaurus
that is also from the Early
Jurassic. Additionally Excalibosaurus was once
thought to be a
synonym to Eurhinosaurus by some until the
discovery of the second
specimen in 1996 which revealed without question that
Excalibosaurus is different enough to deserve
classification as its
own distinct genus.
Further reading
- A putative ancestor for the swordfish-like ichthyosaur Eurhinosaurus
- Nature. 322 (6078): 454–456. - C. McGowan - 1986.
- A new Specimen of Excalibosaurus from the English
Lower Jurassic - Journal of Vertebrate Paleontology. 23 (4): 950–956. -
C. McGowan - 2003.
More marine reptiles.
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