Platypterygius longmani
Geological Time: Lower Cretaceous Aptian Stage (~120 million years ago)
Size (25.4 mm = 1 inch): Various sizes from 43 mm by 30 mm by 15 mm tall to 12 mm by 11 mm by 6 mm tall
Fossil Site: Blackdown Formation, Walsh River, North Queensland, Australia
Code: AAF03
Price: $175.00 - sold
 Description:
This is a group of digits from the fin of an Ichthyosaur known as
Platypterygius longmani. Platypterygius was the last of a line of
‘fish lizards” whose morphology was convergent upon the
modern-day porpoises. It used its lunate tail fro propulsion and its
broad fins (the genus derives its name for the word broad) to maintain
trim and for steering. To date, no ancestral reptile that gave rise
to the Ichthyosaurs has been found. We do know that the early ones
had five digits in each fine which later progressed by the addition
of accessory digits with  many
phalanges. Indeed, Platypterygius had as many as 30 phalanges in a
digit of the front flippers, the most known for any animal, with a
total of some 100 in each fin. This proliferation of digits was how
these Ichthyosaurs solved the problem of developing a broad fin. This
ensemble of tile-shaped bones was compressed into a solid flipper-like
shape which afforded an excellent control surface. Platypterygius
was a moderate-sized Ichthyosaur at 7 meters in length, and was quite
cosmopolitan with specimens having been found in North and South America,
Europe, Russia, India, and Australia. The last example was found in
93.5 million year old deposits in Bavaria, marking the end of a line
that began in the Triassic, a reign of some 160 million years. Why
they became extinct while the Plesiosaurs persisted up to the end-Cretaceous
extinction event over 25 million years later is a mystery. |
