14 DAY TRIAL // Recently, scientists at the University of Alberta studied a pregnant female ichthyosaur fossil with the smallest known embryos inside, which is the most recent record of a live birth. "It was pretty amazing to realize this valuable discovery had sat under a ping pong table for 25 years," said Dr. Michael Caldwell, paleontologist. "But I suppose that after 100 million years in the dirt, it's all relative."
The specimens were collected from the Loon River Formation at Hay River. The fossils ended up in several boxes underneath a ping pong table in the science undergraduate lab. At 2000 renovations, the fossils were rediscovered and triggered interest. The bones are from the Lower Cretaceous (about 100 million years old).
These fossils completed a huge hollow, since the previous known pregnant ichthyosaur specimens are 80 millions older. This collection is also the most northern record of ichthyosaur remains from North America. "What was really interesting was that at this point in history the Ichthyosaur goes extinct," said Caldwell.
"So anything from this time is going to be really important. When we opened it up, we found material in three-dimensions and very finely preserved. Then, it turned out that one was pregnant with two embryos. It was amazing."
"What it shows is that the Canadian version of extinction of the ichthyosaur has more diversity that anyone thought. Even in their declining years there were a lot more species that we thought."
Ichthyosaurs (= fish lizard in ancient Greek) lost their limbs with the evolution. The fore limbs were transformed in paddles while the pelvis and hind limbs were much reduced, making ichthyosaurs very similar to dolphins in appearance. Only their tail fin had a vertical position, not horizontal like in cetaceans. So, like the cetaceans, they were incapable to crawl out of the water to lay eggs.
These finding add to the previous proofs that was "very clear they gave life birth and didn't lay eggs," says Caldwell.
Like most reptiles, ichthyosaurs continuously replaced their teeth throughout their lives.
During the pregnancy, most female ichthyosaurs are completely toothless, giving up the calcium for their own teeth and bones to their developing embryo. "And considering an ichthyosaur could be carrying 12 embryos at one time, that is a lot of calcium needed."
The fossils of Loon River Formation belong to a new genus of ichthyosaur, named Maiaspondylus.