''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 Fossilworks.org is ...

from Santa Cruz Province in

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

. The

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...

and only species is ''Nullotitan glaciaris''. It was a contemporary of the ornithopod '' Isasicursor'' 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. He has been described by paleontologist ...

. 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 (geology), Period of what is now South America. The type species, ''Antarctosaurus wichmannianus'', and a second speci ...

''. 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 ( ; ) were the pre-Twelve Olympians, Olympian gods. According to the ''Theogony'' of Hesiod, they were the twelve children of the primordial parents Uranus (mythology), Uranus (Sky) and Gaia (Earth). The six male ...

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

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

, 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 Fossilworks.org is ...

that dates from the Campanian-Maastrichtian. It consists of a partial skeleton without a skull. The following are preserved: a third cervical vertebra (the MACN-PV 18644 specimen found by Bonaparte in 1981), tail vertebrae, a neck rib, ribs, a left shoulder blade, the ends of a right thigh bone, a right shin, a right calf bone, and a right ankle bone. These bones were found scattered but were believed to represent one individual. In addition, various specimens were allocated. MPM 21545 is a patchy skeleton of which only a humerus, a rib and a vertebra are found. It was a hundred meters from the holotype and higher on the slope so that it is probably another individual that is also clearly smaller than the type specimen. MPM 21546 consists of separate rear tail vertebrae. MPM 21547 consists of a series of five middle tail vertebrae found in a different position. These have not yet been excavated. MPM 21548 has been found in a different position and consists of a left shin. A few meters away lay specimen MPM 21549, a front central vertebra. Eggshells and teeth of sauropods are also stored in this position. No osteoderms have been found anywhere. The fossils are part of the collection ''Museo Regional Provincial "Padre Molina"'', with the exception of the original cervical vertebra that is kept in the ''Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"''.

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 0.28. 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 Titanosauria Dinosaur genera Campanian dinosaurs Taxa named by Fernando Novas Fossil taxa described in 2019 Dinosaurs of Argentina