Mosasaurus hoffmannii
- 演化之聲
- 4 days ago
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Updated: 1 day ago
Age
Cretaceous（Campanian-Maastrichtian）
82.7-66.0 Ma
Taxonomy
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Order: Squamata
Superfamily: Mosasauroidea
Family: Mosasauridae
Subfamily: Mosasaurinae
Genus: Mosasaurus
Species: Mosasaurus hoffmannii
Morphological description
Mosasaurus hoffmannii was an exceptionally large marine squamate from the Late Cretaceous, with adults reaching approximately 13 to 14 metres in total length. The skull was massive and heavily built, and the tip of the snout bore a short, conical edentulous rostrum. The marginal teeth were robust and sharply pointed, and in the anterior portion of the jaws the two carinae were asymmetrical.
The quadrate was tall and thick, and the tympanic rim formed a distinct anteroventral projection, one of the diagnostic features of Mosasaurus hoffmannii. The angular was only briefly visible in lateral view, whereas the surangular was notably tall. The humerus had a broad distal end and a robust, laterally offset postglenoid process, while the femur was expanded at both the proximal and distal ends, reflecting the full transformation of the limbs into flipper-like appendages.
Etymology
Genus name Mosasaurus: derived from the Meuse River (Maas or Mosa) near Maastricht in the Netherlands, the locality most closely associated with the earliest and most famous discoveries of the animal. The name can be understood as meaning "lizard of the Meuse River."
Species name hoffmannii: named in honour of Johann Leonard Hoffmann, a local surgeon and amateur geologist from Maastricht who was closely associated with the early history of the fossil.
Biological description
Mosasaurus hoffmannii was one of the major marine predators of the Late Cretaceous. At a body length of around 14 metres, it was large enough to occupy the uppermost levels of the marine food web. Its heavily built jaws and sharp dentition suggest a feeding apparatus capable of piercing, gripping, tearing, and dismembering prey, making it well suited for handling a wide range of large vertebrates.
The holotype specimen (MNHN AC 9648) comes from the upper Maastrichtian chalk quarries of St Pietersberg near Maastricht in the Netherlands. This famous fossil later became known as the "Grand Animal de Maestricht" and occupies a symbolic place in the history of palaeontology. It was discovered at a time when the idea of extinction had not yet been widely accepted, and its strange anatomy forced naturalists to reconsider how the history of life on Earth should be understood. The work of Georges Cuvier and other early anatomists helped make this specimen one of the key fossils in the development of extinction theory and early vertebrate palaeontology.
In terms of geographic distribution, Mosasaurus hoffmannii was not simply a local form restricted to the shallow seas of Europe. Its known fossil record spans roughly paleolatitudes 30 to 45°N and includes Campanian to Maastrichtian marine deposits in Europe, North America, and western Asia. A new record from Morocco published in 2022 extended this range farther south to approximately 25°N, suggesting that its geographic distribution during the Late Cretaceous may have been broader than previously thought. This indicates that Mosasaurus hoffmannii was a successful large-bodied marine predator capable of maintaining populations across extensive seaways.
Research from Morocco has shown that the Maastrichtian phosphates of that region were deposited in warm, shallow marine environments and preserve an exceptionally diverse mosasaur assemblage. These faunas include piscivorous forms, durophagous taxa, and other large predatory mosasaurs. The occurrence of Mosasaurus hoffmannii in such an assemblage indicates that it was not the sole large predator dominating the region. Instead, it inhabited a marine ecosystem characterized by numerous competitors, diverse prey resources, and a relatively complex ecological partitioning among apex and sub-apex predators.
For more than two centuries, many large marine reptile fossils from around the world that resembled Mosasaurus in general appearance were assigned to the genus. As a result, Mosasaurus became, for a long time, a broadly defined and taxonomically unstable catch-all genus. Only in recent years has re-examination of multiple specimens gradually narrowed the range of species that truly resemble Mosasaurus hoffmannii, restoring its importance as the principal reference point for defining the genus and clarifying the evolutionary limits of Mosasaurus.
The naming history of Mosasaurus hoffmannii was also long and complicated. Although the species epithet hoffmannii was intended to honour Hoffmann, the species was referred to by several alternative names during the 19th and early 20th centuries, including Mosasaurus belgicus and Mosasaurus camperi. Only after later researchers revisited the nomenclatural and specimen history was Mosasaurus hoffmannii stabilized as the accepted formal name for this species.
（Author: Shui-Ye You）
References
Jánišová S. (2025). Evolution, anatomy and distribution of mosasaurs (Mosasauridae). Univerzita Karlova.
Rempert TH et al. (2022). Occurrence of Mosasaurus hoffmannii Mantell, 1829 (Squamata, Mosasauridae) in the Maastrichtian Phosphates of Morocco.
Street HP and Caldwell MW. (2016). Rediagnosis and redescription of Mosasaurus hoffmannii (Squamata: Mosasauridae) and an assessment of species assigned to the genus Mosasaurus. Geological Magazine.
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