Dyrosauridae

The Dyrosauridae are Crocodyliforme S (a gathering taxon good number of groups, whose only the group of the Crocodilien S remains current), appeared there is probably a little more than 80 million years (higher Crétacé) and which died out there is 40 million years. It is thus only via the Fossile S that we know this group.

Simplified version

It is a group (except for one or two exceptions) of marine crocodiles, adapted well to the aquatic life (its tail, principal agent of locomotion in the crocodiles, is very high, allowing an active and effective stroke), but also, thanks to its robust members, very at ease on the dry land.

Its particularitées anatomical common to all the species of it group are rather numerous: the muzzle generally is very lengthened (marking a primarily piscivorous food mode), them windows supratemporales (holes with the back of the orbits, being used for the insertion of the muscles of the jaw on cranium) are very large and lengthened, the seventh tooth of the jaw is always reduced and near to the eighth.

65 million years ago, the end of the Cretaceous will be marked by the famous disappearance of the Dinosaur S on the dry land, but also by the disappearance of the Mosasaure S and the Plésiosaure S in seamen circle. Dyrosauridae, as for them cross without encumbers the great biological crisis, and it even seems that the dyrosauridae, occupying of the ecological niches similar to those occupied by mosasaures and plésiosaures, benefitted from the disappearance of the latter to colonize the seamen circle, where they largely have thrived, before strongly regressing in their turn 40 million years ago, perhaps because of the competition created by the emergence of the first Mammifère S sailors, before dying out completely. Today, the crocodiles (cousins of Dyrosauridae) are fluviatile animals, two species (the marine Crocodile and the Crocodile of the Nile, very far away from dyrosaures) attend the seamen circle and only one is nourished at sea (the marine Crocodile).

Complement (for the specialists and impassioned… and courageous…)

History

The family of Dyrosauridae was created by Stefano (1903) for the Tunisia Dyrosaurus phosphaticus ; this species, described by Thomas (1893) under the name of Crocodilus phosphaticus on some teeth and fragments postcrâniens, was regarded a rhynchocéphale by Stefano (1903) and as a champsosaure by Pomel (1894a). This last described one second species in Algérie, D. thevestensis (Pomel, 1894b) before synonymiser with D. phosphaticus (Pomel, 1894a).

In fact, the first remainders belonging to this were initially described by Owen (1849) with Hyposaurus rogersii , which regarded this species of Maastrichtien and Paleocène of the New Jersey as a “Teleosauroid”. Savage (1904), Nopsca (1905) and Thévenin (1911a, b) as for them, classified Dyrosauridae in the group of the “mésosuchiens”.

The validity of this family was often discussed, Thévenin (1911a, b), Dollo (1914) and Abel (1919) regarding Dyrosaurus as Teleosauridae, Piveteau (1935), Arambourg (1952), Bergounioux (1956) and Romer (1956) like one pholidosauridés and Roux and Douvillé (1910) like Plesiosauridae. Only von Huene (1956), Kuhn (1968) and Steel (1973) regarded Dyrosauridae as a distinct family.

Many family names were in addition given for the remainders of Dyrosauridae, thus Dollo (1914) created Congosauridae for Congosaurus bequaerti , a dyrosaure of the Paléocène of Cabinda (Angola), Swinton (1930) Rhabdognathidae for its Rhabdognathus rarus of Paleocene of the Nigeria, and Bergounioux (1955) Rhabdosauridae for its Rhabdosaurus acutidentatus of Tunisia. The name Congosauridae was accepted besides by several authors like Kuhn (1968) and Steel (1973), which classified in this family all at that time the known dyrosauridae such as C. bequaerti, Dyrosaurus phosphaticus, Phosphatosaurus gavialoides, Rhabdognathus, Rhabdosaurus, Wurnosaurus and Sokotosaurus (among those, certain names of species being regarded more as valid). The clarification of the statute of this family was brought only by Buffetaut, which definitively regarded Dyrosauridae as a family with distinct whole share (Buffetaut, 1976a, 1978b, 1981a), synonymisant all the names defined to him subsequently. It paid to this family, in addition to Dyrosaurus phosphaticus of Tunisia, Sokotosuchus ianwilsoni of Maastrichtien of Nigeria and previously considered as Teleosauridae (Halstead, 1975) and Hyposaurus rogersii of North America and considered until there as Goniopholididae (Mook, 1925; Steel, 1973) or Pholidosauridae (Kälin, 1955). Buffetaut (1976) created later the group of Tethysuchia, perfectly synonymous with the name Dyrosauridae, and divided those into two groups: Phosphatosaurinae (Dyrosauridae with robust teeth) and Hyposaurinae (Dyrosauridae with teeth grèles) (Buffetaut, 1981a).

Geographical distribution

In North America, where the first dyrosaure at summer described, several species were identified in the sediments Maastrichtiens and Paléocènes (Danien). They come mainly from the New Jersey (Owen, 1849; Leidy, 1865; Cope, 1868; Troxell, 1925c; Miller, 1955a; Wolfe, 1977; Parris, 1986; Denton and Al, 1994,1997), but their presence were also announced in South Carolina, Alabama and perhaps in Virginia and the Mississippi (Denton and Al, 1994,1997). Many species were named, with Hyposaurus rogersii (Owen, 1849), Hyposaurus ferox (March, 1871), Hyposaurus natator (Troxell, 1925c) and Hyposaurus natator oweni (Troxell, 1925c). Among those, only H. rogersii and H.natator was recognized like valid species by Norell and Storrs (1989), whereas Denton and Al (1994, 1997) as for them considered only one species, H. rogersii . In South America, the specimen best preserved is represented by a cranial mandible and some fragments and postcrâniens of the Cretaceous of the state of Pernambouc in Brazil (Cope, 1885,1886; Oliveira Roxo, 1937). Cope (1886) named this specimen Hyposaurus derbianus , and Woodward (1888) allotted to this species of the new material of the Lower Cretaceous of Bahia, material allotted thereafter to Goniopholis (Mawson and Woodward, 1907), but probably belonging to Sarcosuchus (Buffetaut and Taquet, 1977; Norell and Storrs, 1989). Brazil, fragments of vertebrae (Carvalho and Azevedo, 1997) or teeth (Gallo and Al, 2000) were also discovered in the Formation Maria Farhina. Other southern countries American, only the Cretaceous of Colombia (Langston, 1965) and the Paleocene one of Bolivia (Argallo and Al, 1987; Buffetaut, 1991a) provided some fragmentary remainders, the species Sulcusuchus erraini of Maastrichtien of Argentina (Gasparini and Spalletti, 1990; Gasparini, 1996), as for it, one not being dyrosauridé as it was initially identified, but a plésiosaure (Gasparini and Fuente, 2000).

In Asia, only some vertebrae were announced in the Paleocene one and the Eocene of the Pakistan (Buffetaut, 1976b, 1977a, 1978c; Storrs, 1986), Higher Eocene of Burma (Buffetaut, 1977a, 1978d), and the Higher Cretaceous of India (Rajendra, 1987). Other remainders coming from the Lower Cretaceous of India could also be allotted to Dyrosauridae (Lydekker, 1879; Pilgrim, 1940), without however, with the sight of the small quantity of material, that this attribution is more final. Of all these fossils, the remainders best preserved are those of a spinal column of connection of Paleocene of Pakistan (Storrs, 1986), which, like all the other Asian fossils, remain unfortunately too fragmentary to be identified more precisely.

In Europe, only a symphyse mandibulaire of Cénomanien of Portugal could be referred to the dyrosaures (Buffetaut and Laverjat, 1978), which, if this taxonomic attribution proved to be exact, would represent the oldest remainder of dyrosauridé known. Another fragment was indeed announced in the Paleocene one of Spain by Costa and Al (1995), but its reduced window supratemporale excluded from the start of Dyrosauridae.

Thus, even if, as we have just seen it, dyrosauridés are widespread on almost all the continents, they are largely more numerous on the African continent. In North Africa, they are present in Tunisia (Thomas, 1893; Pomel, 1894a, B; Stefano, 1903; Thévenin, 1911; Joleau, 1922, have, B; Jouve, 2005), Algeria (Piveteau, 1935) and Morocco (Brives, 1919; Nice, 1922; Joleaud, 1922a, B, 1923,1926; Depéret and Russo, 1924,1925; Arambourg, 1934,1952; Gigout, 1951; Ennouchi, 1957; Buffetaut, 1979a; Hooted, 1995; Jouve, 2004; Jouve and Al, 2004,2005a, 2005b). Arambourg (1952) and Bergounioux (1956) provided the most detailed studies of these African dyrosaures north.

Arambourg (1952) described mainly material Moroccan, but such Tunisian, and named Hyposaurus paucidens starting from a mandible and some remainders postcrâniens. Bergounioux (1955, 1956) as for, named him six new species of Dyrosaurus in the Eocene Inférieur of Tunisia, whereas only one had not been recognized until there. It named also two new kinds, Phosphatosaurus gavialoides and Rhabdosaurus acutidentatus . Buffetaut (1978b) and Moody and Buffetaut (1981) considered only one species of Dyrosaurus like valid at the time of their revision, brought Rhabdosaurus to Rhabdognathus , and provided a more detailed description of Phosphatosaurus gavialoides . The presence of P. gavialoides was in addition announced to Niger and Mali (Buffetaut, 1979b, 1980b), countries partially covered by the Basin of Iullemmeden of the Cretaceous Higher than the Eocene, and where many remainders of dyrosauridés were described. The first fossil was collected by Cortier (1908) and described by Lemoine (1909) and Thévenin (1911b). Because of their abundance in this basin, the dyrosaures were announced to many recoveries (Nopsca, 1925; Bourcart and Keller, 1929; Pérébaskine, 1933a, B; Monod, 1939; Arambourg and Joleaud, 1943; Horn, 1943; Jones, 1948; Karpoff and Visse, 1950; To erase, 1953,1959; Lavocat and Radier, 1953; Lavocat, 1953a, B, 1955b; Karpoff and Al, 1954; Swinton 1930; Kogbe, 1975,1979; Halstead and Middleton, 1976), but Swinton (1930) were truly the first to provide the first exhaustive study of it, by naming three new species: Wurnosaurus wilsoni, Sokotosaurus nopcsai and Rhabdognathus rarus . The revision of the species of the Basin of Iullemmeden made it possible Buffetaut (1980b) to transfer W. wilsoni and S. nopcsai in Hyposaurus , and to set up two new species, R. compressus and Tilemsisuchus lavocati . A cranium of Mali, preserved particularly well, was described well later and allotted to Rhabdognathus sp. by Brochu and Al (2002). This cranium, remains, as well as cranium of Dyrosaurus phosphaticus describes by Jouve (2004), remain best preserved and described of all the specimens of dyrosauridés known until now.

Morocco, has provides recently various news species such Arambourgisuchus khouribgaensis (Jouve and Al, 2005), and Chenanisuchus lateroculi (2005), preserved particularly well.

Dollo (1914) briefly described and named Congosaurus bequaerti , a dyrosaure of Paleocene of Angola, specimen describes more in detail by Swinton (1950), that Arambourg (1952) and Antunes (1964) regarded as synonym of Dyrosaurus . Buffetaut (1976a, 1980b) as for him, regarded it as pertaining to the Hyposaurus , this last attribution being currently that accepted by the majority of the authors.

Many remainders were discovered in many other African countries like Maastrichtien of Egypt (Gemmellaro, 1921), the Paléocène of the Togo (Stromer, 1910; Furon and Kouriatchy, 1948), the Paleocene one and Eocene of the Senegal (Tessier, 1952), Eocene of Libya (Arambourg and Magnier, 1961), Maastrichtien of Sudan (Buffetaut and Al, 1990, Werner, 1993, 1994,1996), the Paleogene of Ethiopia (Wood and Al, 1993; Werner, 1995; Goodwin At Al, 1994) and the Paleocene one of Saudi Arabia (Langston, 1995). In this last country of many remainders are allotted to Hyposaurus sp. and Rhabdognathus sp.

External bond

detailed Phylogenetic tree of the species of this group

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