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Live Birth In Cretaceous Icthyosaurus



came across this while looking for something else:

http://www.pubs.royalsoc.ac.uk/biol_lett/abstracts/caldwell.htm

First record of live birth in cretaceous icthyosaurus: closing an 80
million year gap

by EE Maxwell and MW Caldwell

Ichthyosaurs, are a diverse group of ancient marine reptiles that evolved
a number of specialized adaptations to life in the water and retained
reproductive links to their ancient origins on land. Egg-laying in
ichthyosaurs is not known, though live bearing has been recognized in
ichthyosaurs for some time and evolved early in their history. Until now,
the last known pregnant ichthyosaurs were from the Lower Jurassic (180
ma), however, new fossils from the Lower Cretaceous (100 ma) close that 80
million year gap. These embryos are both the smallest and geologically
youngest known embryos and raise interesting questions about embryonic
development in ichthyosaurs.



http://gessler.ingentaselect.com/vl=2303886/cl=86/ini=rsl/nw=1/rpsv/catchword/rsl/09628452/previews/w03bl0108

Abstract: New fossils of embryonic ichthyosaurs are both the geologically
youngest and the physically smallest known ichthyosaur embryos. The
embryos are articulated, though only partially preserved, and are located
within the body cavity of an adult, presumably the mother. The embryos and
adult were found in association with several other individuals of
differing size classes, all of which appear to be a new taxon of
Cretaceous ichthyosaur. The material was collected from units of the Loon
River Formation, Hay River, Northwest Territories, Canada. The
implications of this new material to ichthyosaurian reproductive biology
are discussed. 


pdf here:


http://gessler.ingentaselect.com/vl=2303886/cl=86/ini=rsl/nw=1/rpsv/catchword/rsl/09628452/previews/w03bl0108.pdf