Posted by: "Lin Kerns" linkerns@gmail.com
lin.kerns Date: Fri Jan 21, 2011 8:34 am ((PST))
[image: 110120142352-large.jpg]
*This is a close up of the egg (20 by 28 mm) preserved together with
Mrs. T, a female Darwinopterus. (Credit: Lü Junchang, Institute of
Geology, Beijing)
*How to Tell a Pterodactyl's Sex: Dino-Era Riddle Solved by New Fossil
Find
ScienceDaily (Jan. 20, 2011) — The discovery of an ancient fossil,
nicknamed 'Mrs T', has allowed scientists for the first time to sex
pterodactyls -- flying reptiles that lived alongside dinosaurs between
220-65 million years ago.
Pterodactyls featured prominently in Spielberg's Jurassic Park III and
are a classic feature of many dinosaur movies where they are often
depicted as giant flying reptiles with a crest.
The discovery of a flying reptile fossilised together with an egg in
Jurassic rocks (about 160 million years old) in China provides the first
direct evidence for gender in these extinct fliers. This fossil shows
that females were crestless, solving the long-standing problem of what
some pterosaurs did with their spectacular head crests: showy displays
by males.
The find was made by an international team of researchers from the
Universities of Leicester, Lincoln and the Geological Institute,
Beijing. Details of the unique new find are published in the journal
*Science*.
David Unwin, a palaeobiologist in the Department of Museum Studies at
the University of Leicester, was part of the research team that studied
the fossil. He said:
"Pterosaurs, flying reptiles, also known as pterodactyls, dominated the
skies in the Mesozoic Era, the age of dinosaurs, 220-65 million years
ago. Many pterosaurs have head crests. In the most spectacular cases
these can reach five times the height of the skull. Scientists have long
suspected that these crests were used for some kind of display or
signalling and may have been confined to males, while females were
crestless. But, in the absence of any direct evidence for gender this
idea remained speculative and crested and crestless forms were often
separated into completely different species."
"The fossil we have discovered, an individual of Darwinopterus (a
pterosaur first described by the same team of scientists in 2009) is
preserved together with an egg showing that it must be female. This type
of discovery, in which gender can be determined with certainty, is
extremely rare in the fossil record, and the first to be reported for
pterosaurs."
The new discovery, christened "Mrs T" (a contraction of "Mrs
Pterodactyl") by the research team, was made in Jurassic rocks of
Liaoning Province in northeast China and seems to represent a tragic
accident. The well developed shell shows that Mrs T was just about ready
to lay her egg when she was killed in an accident that broke her left
forearm, possibly the result of a storm, or perhaps even a volcanic
eruption, which were common in this part of China around 160 million
years old.
Dr Unwin said: "Mrs T shows two features that distinguish her from male
individuals of Darwinopterus. She has relatively large hips, to
accommodate the passage of eggs, but no head crest. Males, on the other
hand, have relatively small hips and a well developed head crest.
Presumably they used this crest to intimidate rivals, or to attract
mates such as Mrs T.
"Mrs T is a once in ten lifetime's discovery. As long as the skull or
hips are preserved we can now confidently identify males and females of
Darwinopterus and, even more importantly, we can use this technique to
sex other pterosaurs because they often show differences in head crests
and hips just as in Darwinopterus."
Dr Unwin added: "Gender is one of the most fundamental of biological
attributes, but extremely difficult to pinpoint with any certainty in
the fossil record. Being able to sex pterosaurs is a major step forward.
Finally, we have a good explanation for pterosaur head crests, a problem
that has puzzled scientists for more than 100 years. Now, we can exploit
our knowledge of pterosaur gender to research entirely new areas such as
population structure and behaviour. We can also play matchmaker for
pterosaurs bringing back together long separated males and females in
the single species to which they both belong."
Apart from gender the new find also has much to tell us about pterosaur
reproduction. Said Dr Unwin: "Mrs T's egg is relatively small and had a
soft shell. This is typical of reptiles, but completely different from
birds which lay relatively large hard-shelled eggs. This discovery is
not surprising though, because a small egg would require less investment
in terms of materials and energy -- a distinct evolutionary advantage
for active energetic fliers such as pterosaurs and perhaps an important
factor in the evolution of gigantic species such as the 10 meter
wingspan Quetzalcoatlus."
*Story Source:*
The above story is reprinted (with editorial adaptations by
Science*Daily*staff) from materials provided by
*University of Leicester* <http://www.leicester.ac.uk/>, via
EurekAlert!<http://www.eurekalert.org/>,
a service of AAAS.
------------------------------
*Journal Reference*:
1. Junchang Lü, David M. Unwin, D. Charles Deeming,
Xingsheng Jin, Yongqing Liu, Qiang Ji. *An Egg-Adult Association,
Gender, and Reproduction in Pterosaurs*. *Science*, 2011; 331
(6015): 321-324 DOI: 10.1126/science.1197323
<http://dx.doi.org/10.1126/science.1197323>
University of Leicester. "How to tell a pterodactyl's sex: Dino-era
riddle solved by new fossil find." *ScienceDaily* 20 January 2011. 21
January 2011 <*http://www.sciencedaily.com
/releases/2011/01/110120142352.htm*>.
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