[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Megalosaurus



The Dickensian _Megalosaurus_ posting inspires the following little essay.
Some of this has already been published in _Mesozoic Meanderings_ #2:

Owen tried to be as accurate as possible when he supervised the construction
of the Crystal Palace dinosaurs, and one thing that seems not often noticed
is that the three CP dinosaurs are all from the Wealden. Now, we know that
the TYPE species of _Megalosaurus_ comes from the Middle Jurassic, but in the
1850s practically all large theropod fossils from anywhere in England were
being assigned to _Megalosaurus_, including scattered teeth, claws, and other
isolated remains of otherwise unknown Wealden theropods. Owen thus imagined
_Iguanodon_, _Megalosaurus_, and _Hylaeosaurus_ could have met in real life
pretty much as depicted in the models.

The most unusual Wealden specimen assigned to _Megalosaurus_ was a series of
three tightly articulated dorsal theropod vertebrae with very tall neural
spines, the latter two spines seemingly significantly taller than the leading
spine. This specimen, presently at the British Museum as BMNH R1828, has the
tallest neural spines relative to centrum diameter of any theropod except
_Spinosaurus_. Owen thought these were from the cranial dorsal series and
imagined them as "withers." They are, indeed, the reason that the Crystal
Palace _Megalosaurus_ was modeled with a "humpback."

In the 20th century, after it was realized that the Middle Jurassic
_Megalosaurus_ could not be among the theropods of the Wealden, von Huene
coined the genus _Altispinax_ for the theropod represented by the vertebrae.
He also published a well-known drawing of a bipedal "_Megalosaurus_" with
very tall neural spines that is still occasionally reproduced in articles on
dinosaur history. By an unfortunate nomenclatural happenstance, the genus
_Altispinax_ became attached to the species _Megalosaurus dunkeri_, based on
a single tooth from the Wealden of Germany, and R1828 was left technically
nameless, even though everyone kept calling it _Altispinax_ and referred it
to _Altispinax dunkeri_. In _Predatory Dinosaurs_, Greg Paul instead referred
it to the genus _Acrocanthosaurus_ as a new species, _Acrocanthosaurus
altispinax_, there being not a shred of evidence that the type tooth and the
vertebrae belong to the same species. But since the neural spines have many
characters distinguishing them from _Acrocanthosaurus_, I placed the specimen
in its own genus _Becklespinax_, named for the famous fossil collector Samuel
Husband Beckles, who found it in the late 1840s.

So--the Crystal Palace model, although labeled _Megalosaurus_, actually
"depicts" a _Becklespinax_(!).

NOTE: Regarding _Megalosaurus bucklandii_. Both Ted Daeschler of the Academy
of Natural Sciences of Philadelphia and I have independently researched the
origin of the type species in some detail, and we agree that name does not
occur among any of Ritgen's works. It was first used by Mantell in 1827. What
DOES occur in an 1826 work by Ritgen is the name _Megalosaurus
conybearei_(!). This forgotten name was applied to the material described by
Buckland and is consequently a senior objective synonym of _Megalosaurus
bucklandii_. The name is a curiosity, and since it has not to my knowledge
appeared in print elsewhere, it should be regarded as a _nomen oblitum_ and
should not be used in place of the widely accepted _Megalosaurus bucklandii_.
I presume the references to _Megalosaurus bucklandii_ in Ritgen 1826 that I
have seen stem from a transcription error propagated through the literature.
This little correction will be published in the third printing of _Mesozoic
Meanderings_ #2.