Mount Saint Peter
Around 1765 the skull of a "Mosasaurus" was discovered here in a limestone quarry, one of the first recognised reptile fossils, which was later acquired by the Teylers Museum in Haarlem. A more famous "Mosasaurus" fossil was found between 1770 and 1774 but was confiscated by the French in 1794 and is now in the Muséum national d'Histoire naturelle in Paris. Later dinosaur remains were discovered here as well, belonging to "Betasuchus" and "Orthomerus", as well as turtles and fossils of smaller creatures of the sea.
Mesosaurus
Clearly amniote-type fossil embryos of "Mesosaurus" in an advanced stage of development (i.e. fetuses) have been discovered in Uruguay and Brazil. These fossils are the earliest record of amniote fetuses, although amniotes are inferred to have had their typical reproductive strategy since their first appearance in the Late Carboniferous. Prior to their description, the oldest known amniote fetuses were from the Triassic. One isolated coiled fetus called FC-DPV 2504 is not surrounded by calcareous egg shells, suggesting that the glands in the oviduct of "Mesosaurus" and probably all paleozoic amniotes were not able to secrete calcium carbonate, in contrast to post-paleozoic archosaurs. This would explain the scarcity of egg fossils in the paleozoic amniote fossil record. One "Mesosaurus" specimen called MCN-PV 2214 comprises a medium-size adult with a small individual in its rib cage which is interpreted as a fetus ‘in utero’, even suggesting that "Mesosaurus" like many other marine reptiles, gave live birth. If this interpretation is correct, this specimen would represent the earliest known example of viviparity in the fossil record. The isolated fetus FC-DPV 2504, however, rather points to an ovoviviparous reproduction strategy in "Mesosaurus".