Mosasaurus of Maastricht: The Sea Lizard Seized by France

The Mosasaurus of Maastricht is a set of giant fossil skulls dug from chalk quarries near the Dutch city of Maastricht in the 18th century. The most famous, found around 1780, was seized by French troops in 1795 and carried to Paris, where it became one of the first fossils to show that animals could vanish entirely from the Earth. The creature, a sea-going lizard of the Late Cretaceous, was later named Mosasaurus, “lizard of the Meuse”.

The chalk mines of Mount St Peter

Sint-Pietersberg, or Mount St Peter, is a low hill just south of Maastricht beside the River Meuse. For centuries its soft limestone and chalk were quarried through miles of underground tunnels for building stone. The rock formed on the floor of a shallow sea around 66 to 68 million years ago, at the very end of the Cretaceous Period.

The rocks are so typical of that time that geologists later named the last stage of the Cretaceous the Maastrichtian, in 1849. Quarrymen regularly found fossil shells, sea urchins and, occasionally, the bones of large animals.

Two remarkable skulls

The first large jaws were found around 1764 and eventually reached the collection of an army officer in Maastricht. Later in the 18th century they were acquired by the Teylers Museum in Haarlem, where they remain.

A second, more complete skull came to light around 1780. According to the traditional story, it was acquired by Johann Leonard Hoffmann, a retired army surgeon and fossil collector, but the canon Theodorus Godding, who owned the land above the quarry, claimed it through the courts and kept it in his country house. Historians have since questioned parts of this tale, including Hoffmann’s exact role and the date of discovery, and some think the skull was found in the 1770s.

Scholars at first could not agree what the animal was. The Dutch anatomist Petrus Camper believed it was a toothed whale, while others suggested a crocodile.

Seized by France in 1795

During the wars of the French Revolution, French armies besieged Maastricht and captured the city in November 1794. Revolutionary France sent commissioners with its armies to collect art and scientific treasures, and the geologist Barthélemy Faujas de Saint-Fond was among those interested in the famous skull.

Godding’s house was searched in vain, as the skull had been hidden in the city. In 1795 it was handed over and shipped to the National Museum of Natural History in Paris. Faujas later told a colourful story that a reward of 600 bottles of wine was offered to the soldiers who found it. The tale is widely repeated, but it rests largely on Faujas’s own account.

Lizard, not whale or crocodile

Faujas published a lavish book on the hill and its fossils in 1798–1799, still describing the animal as a crocodile. Petrus Camper’s son, Adriaan Gilles Camper, studied the bones closely and argued around 1800 that they belonged to a giant lizard related to modern monitor lizards.

The French anatomist Georges Cuvier agreed and developed the case in work published in 1808 and in his great study of fossil bones in 1812. To Cuvier, a marine lizard many metres long, with no living equivalent anywhere, was strong evidence that whole species had become extinct, an idea he was also building from fossils such as mammoths and the Megatherium. In 1822 the English geologist William Conybeare gave the animal the name Mosasaurus, and in 1829 Gideon Mantell added the species name hoffmannii in honour of Hoffmann.

Later finds and legacy

Mosasaurs are now known from Late Cretaceous rocks around the world. They were fully marine predators with paddle-like limbs and long tails, and they died out in the extinction caused by the Chicxulub asteroid impact about 66 million years ago.

Maastricht has continued to produce important specimens, including a well-preserved skeleton found in a quarry in 1998 and nicknamed “Bèr”, now in the city’s natural history museum. The original “great animal of Maastricht” remains in Paris, a lasting reminder of how fossils were caught up in the politics of the revolutionary wars.

Timeline

• c. 1764: First large mosasaur jaws found in the Sint-Pietersberg quarries.
• c. 1780: The more complete “great animal” skull is found; traditional date, possibly earlier.
• 1794, November: French forces capture Maastricht after a siege.
• 1795: The famous skull is taken to Paris.
• 1798–1799: Faujas de Saint-Fond publishes his book on Mount St Peter.
• 1808: Cuvier publishes his identification of the animal as a giant marine lizard.
• 1822: William Conybeare coins the name Mosasaurus.
• 1829: Gideon Mantell names the species Mosasaurus hoffmannii.

Why it matters

The Maastricht skulls were among the first large fossil reptiles studied scientifically, and they played a central role in establishing extinction as a fact of Earth’s history. Their seizure in 1795 also made the “great animal” one of the most famous objects of war booty in the history of science.