Temporal range: 183–163 Ma Toarcian – Callovian
|Steneosaurus bollensis, Holzmaden Germany|
Steneosaurus is an extinct genus of teleosaurid crocodyliform from the Early Jurassic to Middle Jurassic (Toarcian to Callovian). Fossil specimens have been found in England, France, Germany, Switzerland and Morocco. The largest species, S. heberti, reached up to 5 m (16.5 ft) long, though 2.5–3.5 m was far more common.
Species in this genus are traditionally classed into two skull groups: longirostrine (long, narrow jaws) and brevirostrine (short, broad jaws).
- S. baroni: Madagascar from the Bathonian.
- S. bollensis: Western Europe (England, France and Germany) from the Toarcian.
- S. boutilieri: Western Europe (England, France and Switzerland) from the Bathonian.
- S. gracilirostris: Western Europe (England) from the Toarcian.
- S. heberti: Western Europe (France) from the Callovian.
- S. larteti: Western Europe (England and France) from the Bathonian.
- S. leedsi: Western Europe (England and France) from the Callovian.
- S. megistorhynchus: (type) Western Europe (France) from the Bathonian.
- S. pictaviensis: Western Europe (France) from the Callovian.
- S. brevior: Western Europe (England) from the Toarcian.
- S. edwardsi: Western Europe (England and France) from the Callovian.
- S. obtusidens: Western Europe (England) from the Callovian.
A 2005 phylogenetic analysis into the evolutionary relationships of Thalattosuchia did not support the monophyly of Steneosaurus, as the genera Machimosaurus and Teleosaurus both fell within Steneosaurus. Reinforcing the paraphyly of Steneosaurus, the Callovian species Steneosaurus obtusidens has been recovered as the sister species of Machimosaurus in recent cladistic analyses of Thalattosuchia, while Steneosaurus bollensis was recovered in a basal position to other members of Steneosaurus sensu lato. Given the paraphyly of Steneosaurus, Macrospondylus von Meyer, 1830 is the earliest available generic name for S. bollensis.
Steneosaurus (=Aeolodon) priscus is one of five thalattosuchian species known from the Mörnsheim Formation (Solnhofen limestone, early Tithonian) of Bavaria, Germany. Steneosaurus was the only teleosaurid known from this Formation, co-existing with four metriorhynchid species: Dakosaurus maximus, Geosaurus giganteus, Cricosaurus suevicus and Rhacheosaurus gracilis. It has been hypothesised that niche partitioning enabled several species of crocodyliforms to co-exist. D. maximus and G. giganteus would have been top predators of this Formation, both of which were large, short-snouted species with serrated teeth. The remaining species (S. priscus, C. suevicus and R. gracilis) would have fed mostly on fish.
From the semi-aquatic Oker locality in Lower Saxony, Germany (Kimmeridgian-age) two genera of teleosaurids (Steneosaurus and Machimosaurus) are known, in addition to the neosuchian genera Goniopholis and Theriosuchus. Steneosaurus and Machimosaurus are also found together in the same Tithonian-age deposits of western France.
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- 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