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Artist's illistration of Machimosaurus rex
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Superclass: Archosauromorpha
Class: Sauropsida
Clade: Mesoeucrocodylia
Suborder: Thalattosuchia
Family: Teleosauridae
Genus: Machimosaurus
Von Meyer, 1837
  • M.mosae,
  • M.huggi
  • M.nowackianus
  • M.buffetauti
  • M.rex
Type species
Machimosaurus huggi
Von Meyer, 1923

Not to be confused with Mamenchisaurus.

Machimosaurus is an extinct genus of crocodyliform, thalattosuchian and teleosaurid that lived from the Kimmeridgian to the Tithonian stage of the Late Jurassic, Switzerland. Other fossils have been found in England, France, Germany, Portugal, and Tunisia indicating a large range for these creatures.

Machimosaurus was a sea going genus. One species of Machimosaurus- Machimosaurus rex was not only the largest thalattosuchian and teleosaurid ever but it was the largest crocodyliform of the Jurassic period and was comparable to the largest crocodyliformes like Deinosuchus riograndensis since it grew up to 9 metres long and longer than a killer whale. Machimosaurus rex grew up to 9.6 metres (31 feet) and weighed around 3 tonnes making it comparable to the largest killer whales and Dunkleosteus terrelli itself which was one of the largest fish ever and the second largest macropredatory fish.

Machimosaurs were very efficient killers in that they were crocodyliform so they had long rostrums filled with large conical teeth designed for holding on to slippery prey like fish as with most thalattosuchians and crocodyliforms in general.


Machimosaurs were very gharial like in appearance, as is most crocodyliforms that preyed mostly on fish like, Gavialis gangeticus, Crocodylus cataphractus, Crocodylus johnstoni and Tomistoma schlegelii of today that hunt by sweeping their snout through the water using their pressure sensors and electroreception to help them locate the fish and bite down. It can be assumed that Machimosaurus did not use this technique since those crocodilians spend their time waiting at the bottom of rivers and lakes and wait for prey to come to them since they are ambush predators. Machimosaurus on the other hand did not have time to wait at the bottom of the ocean for fish to come to them. This would be unreasonable since the oceans they swam in Europe did not have much areas where they could do this since they would have to keep swimming up to the surface to breathe and it can be assumed that they might have lowered their metabolism and slow down their body functions so they could hold their breath longer since alligators do this. What they do is that when winter comes they poke their snout above the surface of the water and wait for the water to freeze over so they then shut down their bodies to only have the respiratory system and other extremely basic functions like sleeping and breathing so they can hold their breath for up to 8 hours. It is unlikely Machimosaurs did this so they wold have instead been the type to chase their prey down and eaten.

Discovery and species[]

The species of Machimosaurus are:

  • Machimosaurus hugii
  • Machimosaurus mosae
  • Machimosaurus buffetauti
  • Machimosaurus nowackianus
  • Machimosaurus rex




  • Machimosaurus rex's size is based on rough estimates and crocodiles grow their whole lives so it is possible that it grew even bigger.
  • Machimosaurus were highly likely to lay their eggs on land by crawling out of the sea like sea turtles do. Since crocodyliforms do not give live birth.
  • Machimosaurus were likely to only be preyed on by larger marine carnivores like the pliosaurs. Some plesiosaurs and Ichthyosaurs did grow bigger. They all ate the same sort of food and had small heads thus rendering them unable to be predators of prey over 2 metres save for ichthyosaurs like Thalattoarchon.