Anchisaurus
Name:
Anchisaurus
(Near lizard).
Phonetic: An-chih-sore-us.
Named By: Othniel Charles Marsh - 1885.
Synonyms: Megadactylus polyzelus,
Amphisaurus polyzelus, Anchisaurus major, Ammosaurus major, Anchisaurus
colurus, Yaleosaurus colurus, Anchisaurus solus.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Sauropodomorpha, Anchisaura, Anchisauridae.
Species: A. polyzelus
(type).
Diet: Herbivore.
Size: Individuals typically range between 2 and 4
meters in length, though some remains suggest even larger.
Known locations: USA.
Time period: Pliensbachian to Toarcian of the
Jurassic.
Fossil representation: Few individuals.
Anchisaurus
was originally named Megadactylus polyzelus by
Edward Hitchcock;
however after his death it was realised that that Megadactylus
had
already been used to name another creature, and so it could not be
used. Later in 1885, the famous American palaeontologists Othniel
Charles Marsh renamed the fossils Anchisaurus, as
well as identifying
the remains as being those of a dinosaur.
The
exact classification of Anchisaurus has long been a
subject of debate,
with some sources labelling it as a prosauropod, while later
thinking places it as a sauropodomorph. Additionally another genus
called Ammosaurus has been regularly speculated to
be the same dinosaur
as Anchisaurus even though there are some
differences in the pelvis and
hind feet between these two genera. Regardless of its exact
placement, Anchisaurus is a representative of the
kinds of dinosaurs
that would steadily grow bigger and become the quadrupedal sauropods of
the later Jurassic.
The
blunt teeth and jaw construction of Anchisaurus
have been interpreted
as clear signs that Anchisaurus was a plant eating
dinosaur.
Additionally the body is shaped to allow for an increased gut area for
the digestion of plant matter. Some palaeontologists have speculated
however that Anchisaurus may have eaten meat since
the eyes still face
partially forward rather than to the sides like most plant eating
animals that are usually prey for meat eaters. Additionally the
‘thumb’ digit (actually a reversible first digit) had a claw
sharpened beyond that necessary for a herbivore. However what is
certain is that dinosaurs like Anchisaurus were
descended from meat
eating ancestors, and with this in mind it is reasonable to speculate
that the partially carnivorous/predatory features present in
Anchisaurus may just be relict features that were
yet to evolve out.
Further reading
- Restoration of Anchisaurus. - American Journal of
Science. 45 (266):
169–170. - O. C. Marsh - 1893.
- Anchisaurus polyzelus (Hitchcock): The smallest
known sauropod
dinosaur and the evolution of gigantism among sauropodomorph dinosaurs.
- Postilla. 230: 1–57. - A. yates - 2004.
- A revision of the problematic sauropodomorph dinosaurs from
Manchester, Connecticut and the status of Anchisaurus Marsh. -
Palaeontology 53(4):739–752. - A. yates - 2010.
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