Darwinopterus
Name:
Darwinopterus
(Darwin's wing).
Phonetic: Dar-win-op-teh-rus.
Named By: L� et al. - 2010.
Classification: Chordata, Reptilia,
Pterosauria, Wukongopteridae.
Species: D. modularis (type), D.
linglongtaensis, D. robustodens.
Type: Carnivore.
Size: 1 meter wingspan.
Known locations: China - Tiaojishan Formation.
Time period: Bathonian to Oxfordian of the Jurassic.
Fossil representation: Between 30-40 specimens,
one egg.
Darwinopterus
was a truly ground breaking discovery as it displays features of both
the basal rhamphorhynchoid pterosaurs,
and the later more advanced
pterodactyloid pterosaurs. Before the discovery of Darwinopterus,
there was a marked gap between these two groups, but now that the
transitional form of Darwinopterus has been found
it is considered to
be clear proof that the pterodactyloid pterosaurs evolved from the
rhamphorhynchoid pterosaurs. Although popular theory had always
suggested this, hard evidence did not exist before the discovery of
Darwinopterus.
Darwinopterus
has done more than just display a link between these two groups it
has also displayed what has been termed modular evolution. What this
means is that rather than the entire creature changing over a course of
time, only certain parts evolved while other parts remained
'primitive' in their appearance. This can give the impression
that transitional pterosaurs like Darwinopterus
were formed from a box
of pterosaur spare parts rather than being uniformly intermediate.
The
large number of remains have allowed for three distinct species to be
identified, primarily by varying dentition. D. modularis
had the
standard long needle like teeth, D. linglongtaensis
were conical
and in a taller skull, while D. robustodens had
the most robust,
as you might have already gathered by the name 'robustodens'.
All teeth were widely spaced with the teeth being larger towards the
tips of the jaws and the varying forms were likely to be adaptations
for different prey items. With each species occupying a different
ecological niche, Darwinopterus could avoid
direct competition
between the different species as well as other pterosaurs. Although a
transitional form, Darwinopterus has been found a
home within the
wukongopteridae group of pterosaurs that include Wukongopterus.
It
is thought that the larger crested specimens of Darwinopterus
were
males, as evidenced by their narrower hips to equal sized specimens
that do not appear to have crests. This is an expected trait as male
pterosaurs usually have larger crests for display purposes, although
it is possible that known females may be sub-adults yet to develop a
crest of their own. Further evidence for dimorphism exists from the
presence of an egg that was discovered along with a crest-less
specimen. The egg was matched up to the width of the hips and found
to have been easily able to pass through.
The
eggs of Darwinopterus had soft permeable shells
like other later and
advanced pterosaurs. Because the shell is permeable the egg can
absorb moisture from the environment, something bird eggs cannot do.
The idea has been put forward that Darwinopterus
buried its eggs like
other reptiles do to protect them from the elements, and that upon
hatching the youngsters would have been capable of flying almost
immediately. This theory is based upon comparison of pterosaur wings
of different aged individuals of the same species that show the wing
proportions stayed roughly the same no matter the age or size of the
individual.
Further reading
- Evidence for modular evolution in a long-tailed pterosaur with a
pterodactyloid skull. Proceedings of the Royal Society B 277:383-389. -
J. L�, D. M. Unwin, X. Jin, Y. Liu & Q. Ji - 2010.
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