Hoplitosaurus
Name:
Hoplitosaurus
(Hoplite lizard).
Phonetic: Hop-lite-o-sore-us.
Named By: Frederick A. Lucas - 1902.
Synonyms: Stegosaurus marshi.
Classification: Chordata, Reptilia, Dinosauria,
Ornithischia, Thyreophora, Ankylosauria,Nodosauridae,
Polacanthinae.
Species: H. marshi (type).
Diet: Herbivore.
Size: Uncertain due to incomplete remains, but
possibly up to 1.2 meters tall at the hips.
Known locations: USA, South Dakota - Lakota
Formation.
Time period: Barremian of the Cretaceous.
Fossil representation: Partial post cranial remains.
Originally thought to be a species of Stegosaurus at the time of the first description in 1901, the partial post cranial remains were soon identified as being a distinct genus and renamed Hoplitosaurus in 1902. The species name which honours the famous American palaeontologist Othniel Charles Marsh, who actually named the genus Stegosaurus, was retained for the new type species, H. marshi, which is standard procedure for renaming animals under such circumstances. The genus name is a reference to the heavily armoured soldiers called hoplites in the armies of Ancient Greek city-states.
The
renaming of Hoplitosaurus led to it being described
as a different kind
of armoured dinosaur called a polacanthid. This has also since been a
subject of debate over whether it is actually a valid genus, or
simply a specimen of another similar dinosaur called Polacanthus
which
is known from Western Europe. This might seem bizarre since
Hoplitosaurus is only known from the United States,
but a specimen of
Stegosaurus found in Portugal proves that Europe and
North America were
connected and that a faunal interchange between these two continents
was taking place at least as late as the late Jurassic. When this
connection was finally severed is uncertain, but it might still have
existed in the time of Polacanthus and Hoplitosaurus,
the earliest
stages of the early Cretaceous.
The
similarities between Hoplitosaurus and Polacanthus
have actually been
interpreted as being quite generic however (Carpenter &
Kirkland, 1998), meaning that they do not only represent
similarities between these two genera, but across many other genera
as well. Most modern analysis considers Hoplitosaurus
to be a valid
genus, but one that is poorly represented by available fossils.
Future discoveries, specifically those from the Lakota Formation may
one day reveal more about this dinosaur.
What
we can say about Hoplitosaurus is that as a
polacanthid it would have
been a quadrupedal dinosaur with thick plates of bony armour called
osteoderms (sometimes scutes) along its back. There might have
also been an extensive covering of spikes, especially around its
shoulders and along its flanks as this would be similar to other
polacanthid genera. Because of the quadrupedal posture, and an
inability to rear up on its hind legs, Hoplitosaurus
would have been
an obligate browser of low growing vegetation.
Another
polacanthid dinosaur that was likely similar to Hoplitosaurus
and lived
at roughly the same time as it was Gastonia,
which is known from
Barremian age Yellow Cat Member of the Cedar Mountain Formation, Utah.
Further reading
- A new dinosaur, Stegosaurus marshi, from
the Lower Cretaceous
of South Dakota, Frederick A. Lucas - 1902.
- The armoured dinosaur Polacanthus foxi from the
Lower Cretaceous of
the Isle of Wight, W. T. Blows - 1987.
- Review of Lower and middle Cretaceous ankylosaurs from North
America, K. Carpenter & J. I. Kirkland - 1998.
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