Machimosaurus

File:Machimosaurus illustration.jpg

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.{{cite journal | last1 = Vignaud | first1 = P | year = 1997 | title = La morphologie dentaire des Thalattosuchia (Crocodylia, Mesosuchia) | journal = Palaeovertebrata | volume = 26 | issue = 1/4| pages = 35–59 }}

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,{{cite journal | last1 = Krebs | first1 = B | year = 1967 | title = Der Jura-Krokodilier Machimosaurus H. v. Meyer | journal = Paläontologische Zeitschrift | volume = 41 | issue = 1–2| pages = 46–55 | doi=10.1007/bf02998548| bibcode = 1967PalZ...41...46K | s2cid = 130110535 }}{{cite journal | last1 = Buffetaut | first1 = E | year = 1982 | title = Le crocodilien Machimosaurus VON MEYER (Mesosuchia, Teleosauridae) dans le Kimmeridgien de l'Ain | journal = Bulletin Trimestrielle Société de la Géologique Normandie et Amis du Museum, Havre | volume = 69 | issue = 1/2| pages = 17–27 }} 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.{{cite journal | last1 = Hua | first1 = S | last2 = Vasse | first2 = D | last3 = Buffetaut | first3 = E | last4 = Martin | first4 = M | last5 = Mazin | first5 = J-M | last6 = Vadet | first6 = A | year = 1993 | title = Un squelette de Machimosaurus mosae Sauvage et Lienard, 1879 (Crocodylia, Thalattosuchia) dans le Kimméridgien du Boulonnais | journal = Comptes Rendus de l'Académie des Sciences, Série II | volume = 317 | issue = 6| pages = 851–856 }}

Two species also placed within Machimosaurus are M. bathonicus and M. rigauxi, from the Bathonian of France.{{cite journal | last1 = Sauvage | first1 = H-E | year = 1874 | title = Mémoire sur les dinosauriens et les crocodiliens des terrains jurassiques de Boulogne-sur-Mer | journal = Mémoires de la Société Géologique de France |series=Série 2 | volume = 10 | issue = 2| pages = 1–57 }} However, these are gracile species, lacking the characteristic blunted teeth of Machimosaurus, and are probably referable to Steneosaurus.

File:Machimosaurus buffetauti.jpg

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.{{cite journal | last1 = Bardet | first1 = N | last2 = Hua | first2 = S | year = 1996 | title = Simolestes nowackianus HUENE, 1938 from the Late Jurassic of Ethiopia is a teleosaurid crocodile, not a pliosaur | journal = Neues Jahrbuch für Geologie und Paläontologie, Monatshefte | volume = 1996 | pages = 65–71 | doi = 10.1127/njgpm/1996/1996/65 }}

File:Machimosaurus rex skull palatal view.png

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 {{convert|9.6|m|ft|1|abbr=on}} in length (skull length {{convert|155|cm|in|abbr=on}}) 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 {{convert|6.9|-|7.15|m|ft|1|abbr=on}} long.{{Cite journal|url=http://palaeo-electronica.org/content/2016/1554-teleosaurid-size-estimation|doi=10.26879/648|title=Big-headed marine crocodyliforms and why we must be cautious when using extant species as body length proxies for long-extinct relatives|year=2016|last1=Young|first1=MT|last2=Rabi|first2=M.|last3=Bell|first3=MA|last4=Foffa|first4=D.|last5=Steel|first5=L.|last6=Sachs|first6=S.|last7=Peyer|first7=K.|journal=Palaeontologia Electronica|volume=19|issue=3|pages=1–14|doi-access=free}} 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 {{convert|9.6|m|ft|1|abbr=on}} 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.

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

File:Machimozahn.jpg

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.{{cite journal | last1 = Meyer | first1 = CA | last2 = Thüring | first2 = CR | year = 2003 | title = Dinosaurs of Switzerland | journal = Comptes Rendus Palevol | volume = 2 | issue = 1| pages = 103–117 | doi=10.1016/s1631-0683(03)00005-8| bibcode = 2003CRPal...2..103M }} Kimmeridgian-age fossil turtles from "Solothurn Turtle Limestone" of northern Switzerland have bite marks, and splintered Machimosaurus teeth imbedded,{{cite journal | last1 = Meyer | first1 = CA | year = 1991 | title = Burial experiments with marine turtle carcasses and their paleoecological significance | journal = PALAIOS | volume = 6 | issue = 1| pages = 89–96 | doi=10.2307/3514956| jstor = 3514956 | bibcode = 1991Palai...6...89M }} while fossil turtles from the Late Jurassic of Germany also possess bite marks that match teeth of Machimosaurus found in the same deposit.{{cite journal | last1 = Tichy | first1 = G | last2 = Karl | first2 = H-V | year = 2004 | title = The structure of fossil teeth of chelonophagous crocodiles (Diapsida: Crocodylia) | journal = Studia Geologica Salmanticensia | volume = 40 | pages = 115–124 }}

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.{{cite journal | last1 = Massare | first1 = JA | year = 1987 | title = Tooth morphology and prey preference of Mesozoic marine reptiles | journal = Journal of Vertebrate Paleontology | volume = 7 | issue = 2| pages = 121–137 | doi=10.1080/02724634.1987.10011647| bibcode = 1987JVPal...7..121M }}

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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{{Reflist|2}}

• [http://www.angellis.net/Web/PDfiles/repcrocs.pdf Angellis Net pdf]
• [https://web.archive.org/web/20141020000838/http://paleopedia.free.fr/croco_thalattosuchia.html#Machimosaurus Images on French Paleopedia]

{{Thalattosuchia}}

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Category:Prehistoric pseudosuchian genera

Category:Prehistoric marine crocodylomorphs

Category:Early Cretaceous crocodylomorphs of Europe

Category:Late Jurassic crocodylomorphs of Europe

Category:Early Cretaceous crocodylomorphs of Africa

Category:Late Jurassic genus first appearances

Category:Early Cretaceous genus extinctions

Category:Thalattosuchia

Category:Fossil taxa described in 1837