''Nullotitan'' (meaning "Nullo's giant", in honor of paleontologist Francisco Nullo) is a genus of lithostrotian

titanosaur Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still thr ...

from the

Chorrillo Formation The Chorrillo Formation, also named as Chorillo Formation,Río Leona
at Santa Cruz Province in

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

. The type and only species is ''Nullotitan glaciaris''. It was a contemporary of the ornithopod ''

Isasicursor ''Isasicursor'' (meaning "Isasi's runner" after Marcelo Pablo Isasi) is a genus of elasmarian ornithopod from the Chorrillo Formation from Santa Cruz Province in Argentina. The type and only species is ''Isasicursor santacrucensis''. It was a c ...

'' which was described in the same paper.

Discovery and naming

In 1980, geologist Francisco E. Nullo noticed the presence of sauropod bones on a hillside of the Estancia Alta Vista, south of the Centinela River in the Santa Cruz province of Argentina. He reported these finds to then-prominent paleontologist

José Bonaparte José Fernando Bonaparte (14 June 1928 – 18 February 2020) was an Argentine paleontologist who discovered a plethora of South American dinosaurs and mentored a new generation of Argentine paleontologists . One of the best-known Argentine paleo ...

. Bonaparte dug up a large cervical vertebra in 1981 and reported it as a cf. ''

Antarctosaurus ''Antarctosaurus'' (; meaning "southern lizard") is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Period of what is now South America. The type species, ''Antarctosaurus wichmannianus'', and a second species, ''Antarctosau ...

''. The old site was relocated and new excavations were carried out between 13 and 17 January and 14 to 19 March 2019, and a new site was discovered on the Estancia La Anita. A whole new fauna came to light on an area of . including six concentrations of bones that could be assigned to the original find, which was now recognized as a new sauropod species. In 2019, the type species ''Nullotitan glaciaris'' was named and described by Fernando Emilio Novas, Federico Lisandro Agnolin, Sebastián Rozadilla, Alexis Mauro Aranciaga-Rolando, Federico Brisson-Egli, Matias Javier Motta, Mauricio Cerroni, Martín Dario Ezcurra, Agustín Guillermo Martinelli, Julia S. D´Angelo, Gerardo Alvarez -Herrera, Adriel Roberto Gentil, Sergio Bogan, Nicolás Roberto Chimento, Jordi Alexis García-Marsà, Gastón Lo Coco, Sergio Eduardo Miquel, Fátima F. Brito, Ezequiel Ignacio Vera, Valeria Susana Perez Loinaze, Mariela Soledad Fernández and Leonardo Salgado. The large number of authors is a consequence of the fact that the article described the entire fauna in which every expert contributed his part. The genus name honors Nullo and links his name to a Greek "''titan''", referring to the large race of powerful giants, the

Titans In Greek mythology, the Titans ( grc, οἱ Τῑτᾶνες, ''hoi Tītânes'', , ''ho Tītân'') were the pre-Olympian gods. According to the ''Theogony'' of Hesiod, they were the twelve children of the primordial parents Uranus (Sky) and Gai ...

of Greek mythology. The species designation refers to the Perito Moreno Glacier that is visible from the site. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

, MACN-PV 18644; MPM 21542, is found in a layer of the lower

Chorrillo Formation The Chorrillo Formation, also named as Chorillo Formation,Río Leona
at

Description

Size and distinctive features

''Nullotitan'' is a huge sauropod. The found remains of the holotype point to an animal of more than in length. The descriptors were able to identify some distinguishing features. Two of them are autapomorphies, unique derived properties. The anterior and middle tail vertebrae have sides and undersides that are eroded by numerous large depressions that do not pierce the bone wall. From the front or rear, the fibula has a striking, wavy bend. In addition, there is a unique combination of characteristics that are not unique in themselves. The vertebral bodies of the anterior tail vertebrae are remarkably short, twice as wide across as horizontally long. At the middle tail vertebrae there is a large trough on the side that is covered from above by the side protrusion. The tail vertebrae are not pneumatized. The middle tail vertebrae have a deep longitudinal trough on the underside bounded by two thick ridges. The lower end of the tibia is flattened from the front to the rear and widened more across than with other titanosaurs.

Skeleton

The cervical vertebra of the holotype is elongated with a length of and rather low with a height of , apart from the broken vertebral arch. The side is pierced by a large oval pleurocoel. The bottom is flat. The bone has many small air chambers internally, known as ''camellae''. The anterior tail vertebrae have an oval anterior facet. The sides slope down steeply. The side projections are high and flattened from front to back. The first tail vertebra is approximately twenty-five centimeters long and forty wide. The hollows on the sides are randomly distributed, separated by ridges. They are elongated and run lengthwise. Perhaps there were epaxial tendons anchored in it, holding the tail up. The middle tail whirls are square in side view, have a convex cotyle at the back, a deep longitudinal trough on the underside, numerous but shallower recesses, and short conical side protrusions placed at the middle height. The ''Musculus caudofemoralis'', the large retractor muscle that pulled the femur backwards, continued to the sixteenth vertebra. The procoal posterior tail vertebrae are elongated, flattened and with a conical cotyle. The shoulder blade shows few details. There is a bump on the inside, above the level of the ''acromial process'', close to the front and top edges. On the inside there is also a protrusion on the bottom edge. The humerus of MPM 21545 is long. It is relatively slim, with a robustness index (RI) of 2.8. The delta-detectoral comb is relatively short with the lower edge at a quarter of the shaft length measured from above, a basic characteristic. The femur has lower joint nodules that are about the same size. The lower shaft is strongly flattened from front to back, up to . The tibia of the holotype has a length of . It is robust and extremely wide at the bottom. The fibula is . It is robust with an RI of 0.4 but not extreme. The shaft bolt outwards. The ends are strongly widened from front to back. The upper surface runs horizontally. The leg has a low rising branch and a strong widening inside.

Phylogeny

''Nullotitan'' was placed within the Titanosauria in the Colossosauria in 2019, although its precise relationships remain unclear.

Notes

References

{{Taxonbar, from=Q77809704 Titanosaurs Campanian life Maastrichtian life Late Cretaceous dinosaurs of South America Cretaceous Argentina Fossil taxa described in 2019