Trix (dinosaur)

Trix is a ''Tyrannosaurus rex'' specimen excavated in 2013 in Montana, United States by a team of paleontologists from the Naturalis Biodiversity Center in Leiden, the Netherlands and Hills Institute of Geological Research, Black Hills institute of Geological Research in South Dakota. This ''Tyrannosaurus'', over thirty years old the oldest known ''Tyrannosaurus'' specimen lived about 67 million years ago. It is considered to be the third most complete ''Tyrannosaurus'' found, with between 75% to 80% of its bone volume recovered. The specimen was named ''Trix'' after the former Queen Beatrix of the Netherlands. It is one of only two ''Tyrannosaurus'' specimens on permanent exhibit in mainland Europe. The other one is a specimen named Tristan on exhibit at the Natural History Museum of Berlin.

At Naturalis, Trix has the accession or inventory number "RGM 792.000" in which "RGM" refers to the Rijksmuseum van Geologie en Mineralogie, one of the former museums that merged to form the constituent parts of Naturalis.

Discovery

In 2012, Naturalis Biodiversity Center at Leiden, the largest natural history museum of the Netherlands, planned to open a new exhibition hall in 2017. In order to increase the structural number of visitors from 300,000 to 400,000 per annum, the management decided to try and procure an authentic ''Tyrannosaurus'' skeleton, preferably one excavated by the museum itself. In September 2012, a museum delegation travelled to the US to contact the Black Hills Institute, a company that had been involved in nine ''Tyrannosaurus'' excavations. As it happened, the BHI had just received a report from a farmer in Wyoming about a ''Tyrannosaurus'' discovery. Senior Naturalis paleontologist John Vos immediately visited the site and identified the remains as those of ''Tyrannosaurus''. As it was late in the season, it was decided to postpone the excavation until the next Spring. In April and May 2013, the site was thoroughly excavated, but apart from some foot bones, a skeleton proved to be absent. However, five ''Triceratops'' skeletons were present elsewhere on the farm land and procured by the museum for exhibition.

On the evening of 27 May 2013, Blaine Lunstad, an amateur paleontologist, and his wife Michele Lunstad who is of Dutch descent, stumbled upon some bones in the "East Pasture", part of the land of farmer Lige M. Murray, fifty kilometres south of Jordan, Montana. Local fossil hunter Clayton "Dino Cowboy" Phipps confirmed that it was a tyrannosaur skeleton. Rumours of the find reached the BHI, which informed Naturalis. In August 2013, a team of paleontologists from the Naturalis Biodiversity Center, now headed by Anne Schulp, again travelled to the US. From 29 August to 9 September they unearthed a big and remarkably complete ''Tyrannosaurus rex'' specimen. The fossil was found in the Hell Creek Formation. The pattern of geomagnetic reversal showed it had an age of at least 67 million years. The excellent preservation had been caused by the skeleton being surrounded by a three metres thick sandstone lens with a high chalk content, neutralising damaging acids. The Black Hills Institute collaborated with the team in the excavation, which was also assisted by Phipps and the Lundstads. On 5 September, paleontologist Philip Manning of the University of Manchester performed a lidar-laserscan of the site surface to precisely determine the position of all bones.

In May 2015, a CAT-scan of the skull was made in a large industrial scanner of the ''Fraunhofer Entwicklungszentrum Röntgentechnik'' of the '' Fraunhofer Institut'' at Fürth in Germany.

Description

According to Peter Larson, director of the Black Hills Institute, Trix is the third most complete ''Tyrannosaurus'' found, after Sue and Stan. About half of the bones have been found. These represent between 75% and 80% of its bone volume.http://www.thefossilforum.com/uploads/monthly_2016_09/10.thumb.jpg.592a065fd0a51cd2c23fa6d1a2063c29.jpg The main missing parts include the tip of the snout, the front lower jaws, at least seven vertebrae of the middle tail, the point of the tail, the right shoulder blade, the arms, the left hindlimb and the right foot. Parts never before discovered in a ''Tyrannosaurus'' fossil include a turbinal bone in the nasal cavity. A rare element present is the furcula and the stapes of the ear. There is some root damage from plant growth and some bones had been gnawed by scavengers. A smaller shed tooth was found, attributed to '' Nanotyrannus''. Trix in 2016 was the most complete ''Tyrannosaurus'' specimen permanently exhibited outside of the US. ''Tyrannosaurus'' skeletons part of the collection of the Natural History Museum, London, are more fragmentary. Tristan, a skeleton on display in Berlin's Museum für Naturkunde since 2015 (a long-term loan to the museum by its private owner), has around 56% of the original bones, which is slightly more than Trix.

Due to its very large size and robust build, as well as a thickened postorbital bone, it has been suggested that Trix belongs to the robust, instead of the gracile, morphotype. However, the existence of these categories has been doubted and debated several times. The BHI classified Trix as a female, since they and several researchers theorize that a higher robustness is indicative of belonging to the female sex.

Age

Trix's age has been estimated by counting the growth lines in the bones. Two different methods were used for this: a X-ray microtomography, which can be done without damaging the bones, and a very small hole drilled in the fibula to a