Grande nageoire fossile d'ichthyosaure

Large Ichthyosaur Paddle
Leptopterygius quadriscissus
Jurassic
Posidonienschiefer Formation, Holzmaden, Germany
This nicely detailed specimen features an articulated Ichthyosaur paddle displaying finger-like structures; the fingers were used for steering while it was swimming. While humans only have three phalanges in each finger, Ichthyosaurs possessed up to fifteen phalanges, as seen in this specimen. The large number of phalanges also identifies it as a front pectoral paddle as the rear paddles had fewer phalanges.

The Ichthyosaur - Greek for 'fish lizard' - first appeared 250 million years ago, 20 million years before the first dinosaur, and became extinct about 25 million years before their land-dwelling counterparts (about 90 million years ago). They seem to have evolved from land-dwelling reptiles who returned to the oceans. The structure of their flippers suggests that the bones evolved from a form more similar to an arm and a hand, with fingers and a thumb-like appendage. Once back in the water, however, the Ichthyosaur developed a form built for speed, similar to today's tuna, with elongated snout, sleek body and powerful propulsive flippers. This uncommonly large paddle measures 35 x 11 cm in length and is well centered on a Holzmaden shale. Plate measuring 65 x 40 cm