Temporal range: 154–136Ma Kimmeridgian - Valanginian
|Machimosaurus sp. fossil|
Von Meyer, 1837
Machimosaurus is an extinct genus of teleosaurid crocodyliform from the Late Jurassic (Kimmeridgian and Tithonian) and Early Cretaceous (Berriasian and Valanginian). The type species, Machimosaurus hugii, was found in France. Other fossils have been found in Austria, England, Germany, Portugal and Switzerland. Machimosaurus was not only both the largest teleosaurid and thalattosuchian, but with a length exceeding 9 metres (skull length 1.5 m), it was the largest crocodyliform of the Jurassic. However, Machimosaurus became extinct during the Valanginian, and was the last of the teleosaurids.
Discovery and species
Christian Erich Hermann von Meyer in 1837 named isolated conical, blunt teeth with numerous longitudinal lines from Switzerland and Austria, Madrimosaurus hugii. However, in 1838, realising he had made misspelled the name, he emended Madrimosaurus to Machimosaurus. The teeth of Machimosaurus, with their rounded, blunt apex and stout morphology make them characteristic and easily identifiable compared to other teleosaurid teeth.
The type species, M. hugii, is known from the Kimmeridgian of Austria, England, France, Portugal and Switzerland. Machimosaurus ferox, M. recurvirostris and M. interruptus are all junior synonyms of M. hugii.
Krebs (1967), considered M. mosae to be a junior synonym of M. hugii, however a nearly complete skeleton found from the late Kimmeridgian of France supports it as a valid species. As of current knowledge, it remains the only other valid European species. The skull and post-cranial remains Richard Owen referred to Pliosaurus trochanterius, actually belong to M. mosae.
Two species also placed within Machimosaurus are M. bathonicus and M. rigauxi, from the Bathonian of France. However, these are gracile species, lacking the characteristic blunted teeth of Machimosaurus.
The fossilised anterior portion of the lower jaw from the Late Jurassic (Oxfordian or Kimmeridgian) of Ethiopia referred to the pliosaur Simolestes nowackianus, is in fact a large species of Machimosaurus.
From the Kimmeridgian-age, semi-aquatic deposits of Oker, Lower Saxony, Germany two genera of teleosaurids (Steneosaurus and Machimosaurus) are known, in addition to the neosuchian genera Goniopholis and Theriosuchus. Machimosaurus and Steneosaurus are also found together in the same Tithonian-age deposits of western France.
Bite marks on an early Kimmeridgian sauropod (Cetiosauriscus) femur from Switzerland match teeth known from Machimosaurus hugii, also found in the same deposits. This suggests either scavenging on the sauropod's corpse, or active predation from the waters edge, much like living crocodilians. Kimmeridgian-age fossil turtles from "Solothurn Turtle Limestone" of northern Switzerland have bite marks, and splintered Machimosaurus teeth imbedded, while fossil turtles from the Late Jurassic of Germany also possess bite marks that match teeth of Machimosaurus found in the same deposit.
Morphofunctional analysis on the skull of Machimosaurus strongly suggests they eat turtles (chelonophagy). Morphological comparison of their teeth also confirms that they are adapted to seizing and crushing hard prey.
Based on the vertebrae (zygapophysial) articulations, Machimosaurus is considered to have lived in open-seas, swimming by lateral undulations of the tail with the limbs used for steering and balancing. Head and neck depressing (downward moving) muscles would have been well-developed, as their attachment site on the skull (basioccipital tubera) were large. This would have greatly assisted Machimosaurus in diving.
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