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The genus ''Dyrosaurus'' describes an extinct Crocodylomorpha form living from the upper Cretaceous to the Eocene period, surviving the K-T mass extinction〔 Jouve, S., Iarochène, M., Bouya, B., and Amaghzaz. M. 2005. A new dyrosaurid crocodyliform from the Palaeocene ofMorocco and a phylogenetic analysis of Dyrosauridae. ''Acta Palaeontologica Polonica'' 50 (3): 581–594. 〕 or the Cretaceous–Paleogene extinction event. ''Dyrosaurus'' are linked to pholidosaurids as a clade are defined as slender-snouted, fish-eating specialists adapted to near-shore marine habitats.〔 Sereno C., Paul; Larsson E. C., Hans; Sidor, Christian A.; Gado, Boubé. The Giant Crocodyliform ''Sarcosuchus'' from the Cretaceous of Africa. 2001. Science. Vol 294. 1516-1519. Downloaded from http://www.sciencemag.org on March 2, 2015 〕 'Etymology': sauros (σαῦρος) Greek for lizard or reptile. Dyr: Djebel Dyr (mountain near discovery of fossils) D. maghribensis: From ‘Maghrib’, Morocco in Arabic language, referring to the distribution of this species, known up to now in Morocco only.〔 Jouve, Stephanie; Larochène, Mohamed; Bouya, Baâdi;Amaghzaz, Mbarek. A new species of Dyrosaurus (Crocodylomorpha, Dyrosauridae) from the early Eocene of Morocco: phylogenetic implications. 2005. Published in Zoological Journal of the Linnean Society. pg 603-656. 〕 The Dyrosauridae family which encompasses the ''Dyrosaurus'' genus is known to be mostly marine, long jawed crocodile-like species up to 6 meters long.〔 Jouve, Stephanie. A new description of the skull of Dyrosaurus phosphaticus (Thomas, 1893) (Mesoeucrocodylia: Dyrosauridae) from the Lower Eocene of North Africa. 2005. Retrieved March 2, 2015 from http://cjes.nrc.ca. 〕 Based on bone tissue evidence, it has been hypothesized that the family Dyrosauridae were a slow-growing,〔Andrade RCLPd, Saya ̃o JM (2014) Paleohistology and Lifestyle Inferences of a Dyrosaurid (Archosauria: Crocodylomorpha) from Paraíba Basin (Northeastern Brazil). PLoS ONE 9(7): e102189. doi:10.1371/journal.pone.0102189〕 near-shore marine animal that had interlocking closed jaws 〔 Antonio Barbosa, José; Wilhelm Armin Kellner, Alexander. Somália Sales Viana, Maria. New dyrosaurid crocodylomorph and evidences for faunal turnover at the K–P transition in Brazil. 2008. Proceedings of the Royal Society. Downloaded from http://rspb.royalsocietypublishing.org/ 〕 and were quadrupedal with the ability to swim as well as walk on land. It has external naris at the posterior end of its snout and an internal naris in its pterygoid indicative of the need for hunting while swimming with its top of its skull protruding from the water to breathe and see prey easily. 〔 Jouve, Stephanie. A new description of the skull of Dyrosaurus phosphaticus (Thomas, 1893) (Mesoeucrocodylia: Dyrosauridae) from the Lower Eocene of North Africa. 2005. Retrieved March 2, 2015 from http://cjes.nrc.ca. 〕 Fossils from this genus have been found in Africa, Europe, North and South America, Southern Asia and India. 〔 Ashu Khosla, Joseph J. W. Sertich, Guntupalli V. R. Prasad and Omkar Verma Source: Journal of Vertebrate Paleontology, Vol. 29, No. 4 (Dec. 12, 2009), pp. 1321-1326 Published by: Taylor & Francis, Ltd. on behalf of The Society of Vertebrate Paleontology Stable URL: http://www.jstor.org/stable/20627142. Accessed: 03-03-2015 07:01 UTC 〕 Although the family Dyrosauridae is quite diverse with many forms of crocodyliforms, the genus ''Dyrosaurus'' has only two described species: ''D. phosphaticus'' and ''D. maghribensis''. ''D. phosphaticus'' was first discovered in Algeria and Tunsinia whereas ''D. maghribensis'' has only been found in Morocco.〔 Jouve, Stephanie; Larochène, Mohamed; Bouya, Baâdi;Amaghzaz, Mbarek. A new species of ''Dyrosaurus'' (Crocodylomorpha, Dyrosauridae) from the early Eocene of Morocco: phylogenetic implications. 2005. Published in ''Zoological Journal of the Linnean Society''. pg 603-656. 〕 ''D. maghribensis'' differs from ''D. phosphaticus'' by several synapomorphies, most notably: a smooth dorsal margin of the parietal and widely opened choanae, interfenestral bar wide and strongly T shaped instead of moderately T shaped. ==Description== Dyrosaurids are known to have a very characteristic skull shape with a long and thin snout that is approximately 68% of the total skull length. The most anterior part of the skull and snout is the external naris followed posteriorly by two premaxillae bones until they reach two maxillae bones separated by a single nasal bone. 〔 Jouve, Stephanie. A new description of the skull of ''Dyrosaurus phosphaticus'' (Thomas, 1893) (Mesoeucrocodylia: Dyrosauridae) from the Lower Eocene of North Africa. 2005. Retrieved March 2, 2015 from http://cjes.nrc.ca. 〕 Typical in dyrosaurids is a single nasal element with a characteristic collection of small pits and a constant width until it widens to contact the lacrimal bones, then tapering off for a short distance until it meets the boundary of the frontals and prefrontals.〔 Jouve, Stephanie. A new description of the skull of ''Dyrosaurus phosphaticus'' (Thomas, 1893) (Mesoeucrocodylia: Dyrosauridae) from the Lower Eocene of North Africa. 2005. Retrieved March 2, 2015 from http://cjes.nrc.ca. 〕 Dyrosaurs have a premaxilla with shallow pits that extend posterior to the third maxillary alveoli. There are two premaxillae that are narrow as compared to the maxillary bones and extend in the two long maxilla bones which separated by the single nasal bone. The last premaxilla and first maxilla are widely separated by a fourth dentary tooth. Alveoli are widely spaced anteriorly and the space between the them decreases posteriorly from the fifteenth alveolus with the diameter remaining constant.〔 Jouve, Stephanie. A new description of the skull of ''Dyrosaurus phosphaticus'' (Thomas, 1893) (Mesoeucrocodylia: Dyrosauridae) from the Lower Eocene of North Africa. 2005. Retrieved March 2, 2015 from http://cjes.nrc.ca.〕 The maxilla is long (approx. two and a half times the length of jugal) and forms most of the lateral margin of the skull.〔 Antonio Barbosa, José; Wilhelm Armin Kellner, Alexander. Somália Sales Viana, Maria. New dyrosaurid crocodylomorph and evidences for faunal turnover at the K–P transition in Brazil. 2008. Proceedings of the Royal Society. Downloaded from http://rspb.royalsocietypublishing.org/ 〕 According to Jouve and Barbosa and perhaps depending on the age of the animal, each maxilla bears 13-19 teeth.〔 Antonio Barbosa, José; Wilhelm Armin Kellner, Alexander. Somália Sales Viana, Maria. New dyrosaurid crocodylomorph and evidences for faunal turnover at the K–P transition in Brazil. 2008. Proceedings of the Royal Society. Downloaded from http://rspb.royalsocietypublishing.org/ 〕 An important feature of the dyrosaurid dentition are deep occlusal pits, present particularly in the posterior region of the maxillae that get less pronounced anteriorly. The pits are indicative of an interlocking closed jaw for dyrosaurids because the pits give a way for the upper and lower jaws to alternate. Although they are still present in dyrosaurus phosphaticus, this feature of deep occlusal pits become less developed and broad.〔 Antonio Barbosa, José; Wilhelm Armin Kellner, Alexander. Somália Sales Viana, Maria. New dyrosaurid crocodylomorph and evidences for faunal turnover at the K–P transition in Brazil. 2008. ''Proceedings of the Royal Society''. Downloaded from http://rspb.royalsocietypublishing.org/ 〕 Dyrosaurus teeth are homodont and conical as well as long and slender with asymmetrically labial and lingual surfaces. Posterior teeth are shorter and more compressed than anterior tooth indicating that the tooth size decreased anterior to posterior. Dyrosaurs have a snout to skull length of about 68% and the genus ''Rhabdognathus'' and ''Atlantosuchus'', ''Dyrosaurus'' and ''Arambourgisuchus'' have the largest snout proportions of all dyrosaurids. Snout length was previously used it to establish dyrosaurid relationships, while considering the lengthening of the snout to be a ‘more evolved’ character. This was not congruent with Jouve's conclusion which was that the longest snout is actually the primitive condition so the shorter or longer snout appears independently at least four times in dyrosaurid evolution.〔 Jouve, Stephanie; Bouya, Baadi; Amaghzaz, Mbarek. A LONG-SNOUTED DYROSAURID (CROCODYLIFORMES, MESOEUCROCODYLIA) FROM THE PALEOCENE OF MOROCCO: PHYLOGENETIC AND PALAEOBIOGEOGRAPHIC IMPLICATIONS. 2006. Paleontology, vol. 51, part 2, 2008. pp 281-294. 〕 While both are species in the ''Dyrosaurus'' clade, ''D. maghribensis'' and ''D. phosphaticus'' have some difference, one of them being the shape and style of their osteoderm. ''D. maghribensis'' have lateral and medial dorsal osteoderms that are not sutured and have no serration.The anterolateral margin of medial row of the dorsal osteoderms have a rounded lateral lobe and the lateral row of dorsal osteoderms are square in shape with rounded corners. ''D. phosphaticus'' has four longitudinal rows of square osteoderms that are thin and have shallow and wide pits. The osteoderms are square and the anterolateral margin of the medial dorsal osteoderms have an acute rounded process directed laterally.〔 Jouve, Stephanie; Larochène, Mohamed; Bouya, Baâdi;Amaghzaz, Mbarek. A new species of Dyrosaurus (Crocodylomorpha, Dyrosauridae) from the early Eocene of Morocco: phylogenetic implications. 2005. Published in Zoological Journal of the Linnean Society. pg 603-656. 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Dyrosaurus」の詳細全文を読む スポンサード リンク
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