Machimosaurus

Machimosaurus Temporal range: 154–136 Ma PreЄ Є O S D C P T J K Pg N Kimmeridgian - Valanginian
Machimosaurus sp. fossil
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Sauropsida
Infraclass:	Archosauromorpha
(unranked):	Mesoeucrocodylia
Suborder:	Thalattosuchia
Family:	Teleosauridae
Genus:	Machimosaurus Von Meyer, 1837
Species
M. hugii type Von Meyer (1837) M. mosae M. nowackianus  ?M. bathonicus  ?M. rigauxi

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.^[1] 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.^[1] However, Machimosaurus became extinct during the Valanginian, and was the last of the teleosaurids.^[2]

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 mis-spelled the name, he emended Madrimosaurus to Machimosaurus.^[1] The teeth of Machimosaurus, with their rounded, blunt apex and stout morphology make them characteristic and easily identifiable compared to other teleosaurid teeth.^[3]

The type species, M. hugii, is known from the Kimmeridgian of Austria, England, France, Portugal and Switzerland.^[1] Machimosaurus ferox, M. recurvirostris and M. interruptus are all junior synonyms of M. hugii.^[4][5]

Krebs (1967),^[4] 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.^[6] 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.^[1][4]

Two species also placed within Machimosaurus are M. bathonicus and M. rigauxi, from the Bathonian of France.^[7] 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.^[8]

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.^[9] Machimosaurus and Steneosaurus are also found together in the same Tithonian-age deposits of western France.^[10]

Diet

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.^[11] Kimmeridgian-age fossil turtles from "Solothurn Turtle Limestone" of northern Switzerland have bite marks, and splintered Machimosaurus teeth imbedded,^[12] while fossil turtles from the Late Jurassic of Germany also possess bite marks that match teeth of Machimosaurus found in the same deposit.^[13]

Morphofunctional analysis on the skull of Machimosaurus strongly suggests they eat turtles (chelonophagy).^[4][5] Morphological comparison of their teeth also confirms that they are adapted to seizing and crushing hard prey.^[3][14]

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.^[4]

See also

Paleontology portal

• List of marine reptiles

References

1. ^ ^{a b c d e} Steel R. 1973. Crocodylia. Handbuch der Paläoherpetologie, Teil 16. Stuttgart: Gustav Fischer Verlag,116 pp.
2. ^ Cornée JJ, Buffetaut E. 1979. Découverte d’un Téléosauridié (Crocodylia, Mesosuchia) dans le Valanginien sup. du Massif d’Allauch (Sud-Est de la France). Compte Rendu l’Acadamie des Sciences Paris 288: 1151-1154.
3. ^ ^{a b} Vignaud P. 1997. La morphologie dentaire des Thalattosuchia (Crocodylia, Mesosuchia). Palaeovertebrata 26 (1/4): 35-59.
4. ^ ^{a b c d e} Krebs B. 1967. Der Jura-Krokodilier Machimosaurus H. v. Meyer. Paläontologische Zeitschrift 41: 46–55.
5. ^ ^{a b} Buffetaut E. 1982. Le crocodilien Machimosaurus VON MEYER (Mesosuchia, Teleosauridae) dans le Kimmeridgien de l’Ain. Bulletin trimestrielle Societe de la géologique Normandie et Amis du Museum, Havre 69 (1/2): 17-27.
6. ^ Hua S, Vasse D, Buffetaut E, Martin M, Mazin J-M, Vadet A. 1993. Un squelette de Machimosaurus mosae Sauvage et Lienard, 1879 (Crocodylia, Thalattosuchia) dans le Kimméridgien du Boulonnais. Comptes rendus de l'Académie des sciences. Série 2, Mécanique, Physique, Chimie, Sciences de l'univers, Sciences de la Terre 317 (6):851-856
7. ^ Sauvage H-E. 1874. Mémoire sur les dinosauriens et les crocodiliens des terrains jurassiques de Boulogne-sur-Mer. Mémoires de la Société Géologique de France, série 2 10 (2):1-57.
8. ^ Bardet N, Hua S. 1996. Simolestes nowackianus HUENE, 1938 from the Late Jurassic of Ethiopia is a teleosaurid crocodile, not a pliosaur. Neues Jahrbuch für Geologie und Paläontologie Monatschefte 1996: 65-71.
9. ^ 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.
10. ^ 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
11. ^ Meyer CA, Thüring CR. 2003. Dinosaurs of Switzerland. Comptes Rendus Palevol 2 (1): 103–117.
12. ^ Meyer CA. 1991. Burial experiments with marine turtle carcasses and their paleoecological significance. Palaios 6 (1): 89-96.
13. ^ Tichy G, Karl H-V. 2004. The structure of fossil teeth of chelonophagous crocodiles (Diapsida: Crocodylia). Studia Geologica salmanticensia 40: 115-124.
14. ^ Massare JA. 1987. Tooth morphology and prey preference of Mesozoic marine reptiles. Journal of Vertebrate Paleontology 7: 121-137.

External links

• Angellis Net pdf
• Images on French Paleopedia