Simolestes
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- Simolestes vorax ( type species )
- Simolestes indicus
- Simolestes keileni
Simolestes is a genus of extinct marine reptiles from the group of Pliosauroidea that lived during the Middle and Late Jurassic period. The type species was Simolestes vorax 1909 described by Charles William Andrews based on a nearly complete skeleton, which dates from the Oxford Clay Formation in England. Currently, two additional species are recognized, Simolestes indicus and Simolestes keileni that originate from India and France. The Pliosauroidea be assigned to two groups, the Rhomaleosauridae and Pliosauridae, which is controversial, to which of these groups Simolestes be expected. The most recent studies suggest, however, that the genus to the Pliosauridae can be counted.
Features
As with other members of the Pliosauroidea there was a large carnivore with a spindle-shaped body and a short tail. Composed of about 20 neck vertebrae, relatively short neck ending in a relatively large head. Front and hind limbs were transformed into paddles, paddle vobei the front pair was significantly shorter than the rear. Simolestes reached a length of more than 10 m, making it one of the largest Pliosauriden.
The skull was compared with other Pliosauroidea relatively short and wide. On each side of the lower jaw were about 26 teeth that were round in cross-section and no cutting edges had. The lower jaw ran together in the tip of the snout to a spoon-shaped rosette, whose five to six teeth were enlarged compared to the remaining teeth. Such rosette was typical for representatives of Rhomaleosauridae, but was absent in most representatives of Pliosauridae.
Systematics, species and fossil record
The systematic position of Simolestes within the Plesiosauroidea is controversial. The short snout and spoon-shaped tip of the snout have a membership to the Rhomaleosauridae, during the construction of the palate speaks for a membership to the Pliosauridae. The most recent studies classify the genus within the Pliosauridae. Thus, the spoon-shaped tip of the snout could at Simolestes and Rhomaleosauriden independently ( convergent ) have developed, possibly due to similar eating habits.
The type species Simolestes vorax based on a nearly complete skeleton ( copy number BMNH R.3319 ), which was discovered near Peterborough in England and comes from the Lower Oxford Clay formation. This rock unit is dated to the Callovian ( Middle Jurassic ). Noé (2001) also wrote of this kind to a skull ( copy number PETMG R296 ), which was discovered in 1990 and initially Liopleurodon was attributed. In addition to the type species, two additional species are recognized: the from the Upper Jurassic ( Tithonian ) of India originating Simolestes indicus and from the Middle Jurassic ( Bajocian ) of France coming Simolestes keileni. S. indicus was described by Lydekker (1877 ) as a species of the genus Plesiosaurus and later the genus Thaumatosaurus; Bardet and colleagues ( 1991), she finally arranged to the genus Simolestes. S. keileni was described by Godefroit (1994 ), based on a fragmentary skeleton from the Lorraine community Montoises -la -Montagne.