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 Black Hills Institute of Geological Research in South Dakota. This Tyrannosaurus, over thirty years old – the oldest known Tyrannosaurus specimen – lived around 67 million years ago. It is considered to be the third most complete Tyrannosaurus found, with between 78% and 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 United States 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 de 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 United States. 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. 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 United States. 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. Trix is approximately 12.5–13 meters (41.0–42.7 ft) long along the centra, and stands 4 meters (13 ft) tall at the hips. Trix has been estimated to have weighed between 5 metric tons (5.51 short tons) when living, as of 2017.
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: an X-ray microtomography, which can be done without damaging the bones, and a very small hole drilled in the fibula to allow comparison with the results of the X-ray based technique. This study was carried out in collaboration with Sifra Bijl, from the Vrije Universiteit Amsterdam, and Koen Stein, a Belgian researcher from the Free University of Brussels, and attached to the Royal Belgian Institute of Natural Sciences. The growth lines were numerous, and difficult to distinguish. These facts alongside the roughness and rugosity of the skull are indications that this individual had reached an old age for a T. rex; in this case at least 30 years, as opposed to Sue's 28 years (which was the second oldest specimen known until now), making Trix the oldest Tyrannosaurus known. Subsequent analysis has updated the age estimate, placing Sue between 27-33 years old at the time of her death, making her the oldest T. rex specimen ever published, and Trix the second-oldest known.
Diseases
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