Tratayenia is an extinct genus of megaraptoran theropod dinosaurs known from remains found in the Santonian-age Bajo de la Carpa Formation of Argentina.
[1] This skeleton was first discovered in 2006 at a Bajo de la Carpa Formation fossil site by Universidad Nacional del Comahue technician Diego Rosales.
Tratayenia is also the largest-bodied carnivorous animal named from the Bajo de la Carpa Formation, reinforcing the hypothesis that megaraptorids were apex predators in southern South America from the Turonian through the Santonian or early Campanian, following the extinction of carcharodontosaurids.
[1][2] The dorsal vertebrae were tall and narrow, with large pits known as pleurocoels on the side of their centra (spool-shaped main portion).
A large and deep excavation is located directly below each transverse process, bounded from the front and rear by thin laminae (ridges).
The front edge of each vertebra has a third autapomorphy, related to two pairs of laminae (four total) connecting the prezygapophyses to the neural spines.
They are very similar to the dorsal vertebrae in various aspects, such as the presence of large pleurocoels, tall and narrow centra, and laminae-bound excavations below the transverse processes.
This trait has also been observed in Tyrannosaurus and an unnamed megaraptoran sacrum (SNMS 58023) from the Romualdo Member of the Santana Formation in Brazil,[4] so its status as an autapomorphy of Tratayenia is not concrete.
A bone identified as the pubic boot (expanded tip of the pubis) has been found in the holotype, as well as fragments of the ischium, which has the form of a long, thin shaft covered in grooves.
The second popular hypothesis considers them to be basal tyrannosauroids, part of the coelurosaur lineage which includes the crested proceratosaurids as well as the famous tyrannosaurids such as Tyrannosaurus.
[1] Although the results are different, the methodology analysis was practically identical to that of Apesteguia et al. (2016), only differing in the fact that it incorporated Tratayenia and Murusraptor, two megaraptorans not sampled in the analysis of Apesteguia et al.[5] Eocarcharia Neovenator Concavenator Acrocanthosaurus Allosaurus Sinraptor Monolophosaurus Shaochilong Carcharodontosaurus Tyrannotitan Mapusaurus Giganotosaurus Gualicho Chilantaisaurus Fukuiraptor Murusraptor Tratayenia Megaraptor Aerosteon Australovenator Orkoraptor Tyrannoraptora Tratayenia lived in the Bajo de la Carpa Formation alongside many lizards and turtles, the snake species Dinilysia patagonica, many birds such as Patagopteryx deferrariisi, a diverse amount of crocodylomorphs and many dinosaurs such as Viavenator exxoni and Traukutitan eocaudata.