Machimosaurus Illustration

''Machimosaurus'' is an extinct genus of machimosaurid crocodyliform from the Late Jurassic (Kimmeridgian and Tithonian) and Early Cretaceous. The type species, ''Machimosaurus hugii'', was found in Switzerland. Other fossils have been found in England, France, Germany, Portugal, Switzerland and Tunisia.Steel R. 1973. ''Crocodylia. Handbuch der Paläoherpetologie, Teil 16''. Stuttgart: Gustav Fischer Verlag,116 pp. ''Machimosaurus rex'' is the largest named teleosauroid and thalattosuchian, with an estimated length of up to (skull length ). ''Machimosaurus'' is the largest known crocodyliform of the Jurassic.

Discovery and species

Christian Erich Hermann von Meyer in 1837 named isolated conical, blunt teeth with numerous longitudinal lines from Switzerland, ''Madrimosaurus hugii''. However, in 1838, realising he had misspelled the name, he emended ''Madrimosaurus'' to ''Machimosaurus'', from the Greek ''machimoi'', ancient Egyptian troops deployed during the Ptolemaic Dynasty plus the ''-saurus'' suffix, literally meaning "pugnacious lizard". 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 Portugal, Spain, Tunisia and Switzerland. ''Machimosaurus ferox'' and ''M. interruptus'' were previously considered junior synonyms of ''M. hugii'', but have been recently considered possible synonyms of ''Machimosaurus mosae''.

Krebs (1967), considered ''M. mosae'' (Lienard, 1876) to be a junior synonym of ''M. hugii'', but is considered a second valid species of the genus based on a nearly complete skeleton found from the late Kimmeridgian of France.

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'', and are probably referable to ''Steneosaurus''.

Mark Young and his colleagues Young, M. T., Hua S., Steel L., Foffa D., Brusatte S. L., Thüring S., Mateus O., Ignacio-Ruiz Omeñaca J., Lepage Y., Havilk P., & Andrade M. B. (2014). Revision of the Late Jurassic teleosaurid genus Machimosaurus (Crocodylomorpha, Thalattosuchia). Royal Society Open Science. 1(140222), 1-42.Young, M. T., Hua S., Steep L., Foffa D., Brusatte S. L., Thüring S., Mateus O., Ruiz-Omeñaca J. I., Havlik P., Lepage Y., & de Andrade M. B. (2015). Addendum to ‘Revision of the Late Jurassic teleosaurid genus Machimosaurus (Crocodylomorpha, Thalattosuchia)’. Royal Society Open Science. 2, Number 2 made a detailed revision of the genus and recognized four species: ''M. hugii'', ''M. mosae'', ''M. nowackianus'' from Harrar, Ethiopia, and a new species, ''Machimosaurus buffetauti''. They hypothesized that ''Machimosaurus'' may have been analogous to the Pliocene–Holocene genus ''Crocodylus'' in having one large-bodied taxon suited to traversing marine barriers and additional, geographically limited taxa across its range.

The fossilized 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''.

In 2016, a new species of ''Machimosaurus'' from Douiret Formation in Tunisia was described in the journal ''Cretaceous Research''. Named ''Machimosaurus rex'', it was the largest teleosauroid known at the time, estimated to be in length (skull length ) based on a partial skeleton. ''M. rex'' was also the youngest teleosauroid known at the time. However, more recent estimates put ''M. hugii'' along with ''M. rex'' at about long. The discovery of ''M. rex'' indicates that teleosauroid crocodylomorphs survived the extinction event at the end of the Late Jurassic, but did not retain the biodiversity seen in the Jurassic. Moreover, an incomplete specimen from the Barremian of Colombia attributed to Teleosauroidea is not only the youngest known teleosauroid, but also the largest at about long.Cortes D, Larsson HCE, Maxwell EE, Parra Ruge ML, Patarroyo P, Wilson JA. 2019. An Early Cretaceous teleosauroid (Crocodylomorpha: Thalattosuchia) from Colombia. Ameghiniana. doi:10.5710/AMGH.26.09. 2019.3269.

Palaeobiology

Niche partitioning

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''.Karl H-V, Gröning E, Brauckmann C, Schwarz D, Knötschke N.2006. The Late Jurassic crocodiles of the Langenberg near Oker, Lower Saxony (Germany), and description of related materials (with remarks on the history of quarrying the "Langenberg Limestone" and "Obernkirchen Sandstone"). ''Clausthaler Geowissenschaften'' 5: 59-77. ''Machimosaurus'' and ''Steneosaurus'' are also found together in the same Tithonian-age deposits of western France.Billon-Bruyat J-P, Mazin J-M, Buffetaut E, Tong H, Abit D. 2001. New occurrence of vertebrate remains in the latest Jurassic of western France (Oléron island, Charente-Maritime). ''6th European Workshop on Vertebrate Palaeontology - Florence and Montevarchi (Italy) - September 19–22, 2001 Abstract Booklet'', p. 19

Diet

Bite marks on an early Kimmeridgian sauropod (''Amanzia'') 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 ate turtles (chelonophagy). Morphological comparison of their teeth also confirms that they are adapted to seizing and crushing hard prey.

Locomotion

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.

See also

*List of marine reptiles

References

External links

Angellis Net pdf

{{Taxonbar, from=Q140791

Prehistoric pseudosuchian genera
Prehistoric marine crocodylomorphs
Early Cretaceous crocodylomorphs of Europe
Late Jurassic crocodylomorphs of Europe
Early Cretaceous crocodylomorphs of Africa
Late Jurassic genus first appearances
Early Cretaceous genus extinctions
Thalattosuchia
Fossil taxa described in 1837