Simolestes

Simolestes
	Artistic representation of life
Temporal occurrence
	Middle Jurassic ( Bajocium ) to Upper Jurassic ( Tithonium )
	170.3 to 145 million years
Locations
	England; India; France;
Systematics
	Lepidosauromorpha
	Sauropterygia
	Plesiosaurs (Plesiosauria)
	Pliosaurs (Pliosauroidea)
	Simolestes
Scientific name
	Simolestes
	Andrews , 1909
species
	Simolestes vorax ( type species ); Simolestes indicus; Simolestes keileni;

Simolestes is a genus of extinct marine reptiles belonging to the Pliosauroidea group that lived during the Middle and Late Jurassic Period . The type species Simolestes vorax was described in 1909 by Charles William Andrews on the basis of an almost complete skeleton that comes from the Oxford Clay Formation in England . Two other species are currently recognized, Simolestes indicus and Simolestes keileni , which originate from India and France. The Pliosauroidea are assigned to two groups, the Rhomaleosauridae and the Pliosauridae , although it is disputed which of these groups Simolestes belongs to. Most recent studies suggest, however, that the genus can be counted among the Pliosauridae.

features

Drawing of the skull from 1913

As with other representatives of the Pliosauroidea, it was a large, carnivorous animal with a spindle-shaped body and short tail. The relatively short neck, consisting of around 20 cervical vertebrae, ended in a relatively large head. The front and rear limbs were converted into paddles, with the front pair of paddles being significantly shorter than the rear. Simolestes reached a length of more than 10 m and is one of the largest Pliosaurids.

The skull was relatively short and wide compared to other Pliosauroidea. There were about 26 teeth on each side of the lower jaw, which were round in cross-section and had no cutting edges. The lower jaws converged at the tip of the snout to form a spoon-shaped rosette, the five to six teeth of which were larger than the remaining teeth. Such a rosette was typical for members of the Rhomaleosauridae, but was missing from most members of the Pliosauridae.

Systematics, species and fossil record

Tooth of Simolestes vorax

The systematic position of Simolestes within the Plesiosauroidea is controversial. The short snout and the spoon-shaped snout tip indicate that it belongs to the Rhomaleosauridae, while the structure of the palate suggests that it belongs to the Pliosauridae. Most recent studies classify the genus within the Pliosauridae. The spoon-shaped tip of the snout in Simolestes and the rhomaleosaurids could have developed independently of one another ( convergent ), possibly due to similar eating habits.

The type species Simolestes vorax is based on an almost complete skeleton (specimen number BMNH R.3319) that 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 attributed a skull to this species (specimen number PETMG R296), which was discovered as early as 1990 and was initially attributed to Liopleurodon . In addition to the type species, two other species are recognized: The Simolestes indicus from the Upper Jura ( Tithonium ) of India and the Simolestes keileni from the Middle Jura ( Bajocium ) of France . S. indicus was already described by Lydekker (1877) as a species of the genus Plesiosaurus and later the genus Thaumatosaurus ; Bardet and colleagues (1991) finally assigned them to the genus Simolestes . S. keileni was described by Godefroit (1994), based on a fragmentary skeleton from the Lorraine community of Montois-la-Montagne .

Individual evidence

↑ ^a ^b ^c ^d Adam Stuart Smith: Anatomy and systematics of the Rhomaleosauridae (Sauropterygia: Plesiosauria). University College Dublin, Dublin 2007, pp. 239-230, 257, 264 (Dublin, University College Dublin - School of Biology & Environmental Science, Thesis (Ph. D.), 2007).
^ Richard Forrest: A large rhomaleosaurid Pliosaur from the Upper Lias of Rutland. In: Mercian Geologist. Vol. 15, No. 1, 2000, ISSN 0025-990X , pp. 37-40 ( online ).
^ ^A ^b Charles William Andrews : A descriptive Catalog of the marine Reptiles of the Oxford Clay. Based on the Leeds collection in the British Museum (Natural History). Part 1. British Museum (Natural History) Department of Geology. Printed by order of the Trustees, London 1910, pp. 25-34 ( GoogleBook ).
^ Simolestes - Taxonomy. In: The Paleobiology Database. Retrieved May 23, 2011 .
↑ Pascal Godefroit: Simolestes keileni sp. nov., un Pliosaure (Plesiosauria, Reptilia) du Bajocien supérieur de Lorraine (France). In: Bulletin des Académie et Société Lorraines des Sciences. Vol. 33, No. 2, 1994, ISSN 0567-6576 , pp. 77-95 ( online ).

Web links

Commons : Simolestes - collection of images, videos and audio files

Adam S. Smith: Simolestes Andrews, 1909 . The Plesiosaur Directory.

[smith_07-1] Adam Stuart Smith: Anatomy and systematics of the Rhomaleosauridae (Sauropterygia: Plesiosauria). University College Dublin, Dublin 2007, pp. 239-230, 257, 264 (Dublin, University College Dublin - School of Biology & Environmental Science, Thesis (Ph. D.), 2007).

[forrest_20-2] Richard Forrest: A large rhomaleosaurid Pliosaur from the Upper Lias of Rutland. In: Mercian Geologist. Vol. 15, No. 1, 2000, ISSN 0025-990X , pp. 37-40 ( online ).

[andrews_1910-3] A ^b Charles William Andrews : A descriptive Catalog of the marine Reptiles of the Oxford Clay. Based on the Leeds collection in the British Museum (Natural History). Part 1. British Museum (Natural History) Department of Geology. Printed by order of the Trustees, London 1910, pp. 25-34 ( GoogleBook ).

[paleodb-4] Simolestes - Taxonomy. In: The Paleobiology Database. Retrieved May 23, 2011 .

[godefroit_94-5] Pascal Godefroit: Simolestes keileni sp. nov., un Pliosaure (Plesiosauria, Reptilia) du Bajocien supérieur de Lorraine (France). In: Bulletin des Académie et Société Lorraines des Sciences. Vol. 33, No. 2, 1994, ISSN 0567-6576 , pp. 77-95 ( online ).