Juratyrant

''Juratyrant'' (meaning "Jurassic tyrant") is a tyrannosauroid dinosaur genus from the late Jurassic period (early Tithonian age) of England. The genus contains a single species, ''Juratyrant langhami'', which was once classed as a species of '' Stokesosaurus''.

Discovery

The species is known from a single specimen consisting of an "associated partial skeleton represented by a complete pelvis" as well as a partially complete leg and neck, back and tail vertebrae. This skeleton was discovered in 1984 in Dorset. The specimen was mentioned in several papers, but was not formally described until 2008. The species was named in honor of commercial fossil collector Peter Langham, who uncovered the specimen. The specimen was discovered in strata of the Kimmeridge Clay dating from the Tithonian, the final stage of the Late Jurassic, and belonging to the '' Pectinatites pectinatus'' ammonite zone, indicating the fossil is between 149.3 and 149 million years old.

Description

Paul (2010) listed it at and . In a 2013 study, it was estimated to weigh up to . Another estimation gave a larger size of and .

The holotype of ''Juratyrant'' is a partial skeleton composed of specimens OUMNH J.3311-1 through OUMNH J.3311-30. Its components include a cervical vertebra, five dorsal vertebrae, a complete sacrum, five caudal vertebrae, a complete pelvic girdle, both femurs, both tibiae, and various other fragments. Although initially considered a species of ''Stokesosaurus'' due to various traits of the ilium, subsequent review has shown that due to the limited amount of pelvic material for basal tyrannosauroids, these traits cannot be assumed to only be present in these two species and thus ''S. langhami'' must be placed in its own genera. Once separated from ''Stokesosaurus'', ''Juratyrant'' can be characterized by four autapomorphies, as well as two assumed autapomorphies (which are difficult to assess due to preservation):

* An ischial apron with a "folded" appearance.
* A fibular flange that continues as a distinct low ridge to the proximal end of the tibia.
* A convex tubercule on the ischium.
* A deep lateral fossa on the pubis below the acetabulum.
* A thin but prominent hyposphene on the fifth sacral vertebra (assumed).
* A broad, concave extensor groove of the femur (assumed).

Classification

The species was originally assigned to the genus '' Stokesosaurus'', as ''Stokesosaurus langhami'', by Roger Benson in 2008. However, later studies showed that it was not necessarily a close relative of ''Stokesosaurus clevelandi'', the type species of that genus. It was formally re-classified in its own genus, ''Juratyrant'', by Benson and Stephen L. Brusatte in 2013 and placed as a sister taxon to ''Stokesosaurus clevelandi'' in a clade (also including ''Eotyrannus'') of basal tyrannosauroids more advanced than ''Dilong''.

However, in 2013 Loewen ''et al.'' published a cladogram placing ''Juratyrant'' as a sister taxon to ''Stokesosaurus'' inside Proceratosauridae due to sharing with '' Sinotyrannus'' a narrow preacetabular notch. Many basal tyrannosauroids have incomplete or unknown ilia and this trait may be more widespread than currently known. This cladogram is shown below.

However, a 2016 analysis by Brusatte and Carr utilizing both parsimonious and Bayesian phylogeny placed ''Stokesosaurus'' and ''Juratyrant'' as tyrannosauroids slightly more advanced than the Proceratosauridae and ''Dilong''. In addition, '' Eotyrannus'' is recovered as a sister taxon of these genera in the parsimonious phylogeny.

See also

* Timeline of tyrannosaur research

References

{{Taxonbar, from=Q2701043

Tyrannosauroidea
Dinosaur genera
Tithonian dinosaurs
Fossil taxa described in 2013
Taxa named by Stephen L. Brusatte
Dinosaurs of the United Kingdom