Lirainosaurus

*Lirainosaurus astibiae*

Lirainosaurus is the name given to a genus of dinosaur from the Late Cretaceous. It was a titanosaurid sauropod which lived in what is now Spain. The type species, Lirainosaurus astibiae, was described by Sanz, Powell, Le Loeuff, Martinez, and Pereda-Suberbiola in 1999.

Lirainosaurus lived in the Upper Cretaceous (Campanian / Maastrichtian, some 71 million years ago) and its fossil remains have been found in northern Spain. It is considered one of the lightest sauropods from the constitution.

This dinosaur is known for the scattered remains of some specimens, both young and adults, including skull fragments, teeth, pencil-shaped, dorsal and caudal vertebrae, a scapula, a coracoid, part of the sternum, part of the hind legs and front, fragments of a pelvis and two bony plates (osteoderms). The appearance of this animal had to be rather light for a sauropod, and feet were unusually slender. The length should not exceed 10 meters, while the body was protected by an armor of small bony plates embedded in the skin, as in many Titanosaurus (eg Saltasaurus).

Lirainosaurus has been described for the first time in 1999, and was attributed to the Titanosauridae, a group of sauropods which were very numerous and widespread in much of the world in the Cretaceous period. In particular, it seems that Lirainosaurus was a relatively primitive, perhaps close to the origin of the family of Saltasauridae, which also includes the most advanced Titanosaurs.

The name Lirainosaurus derives from a word in the Basque language, â€œlirainâ€, which means “slender”(with reference to the unusual structure of slender leg bones). The specific name, is in honor of Humberto Astibia, leader of the researchers who excavated the site where the fossils were found.

## Description

Lirainosaurus was small in size for a sauropod, Company in 2011 estimated its dimensions between 8 and 10 meters in length and a weight of around 1.5 tons, while Díez Díaz et al. in 2013 only 4 to 6 meters in length and 2 to 4 tons for the largest individuals. It was only slightly heavier than dwarf sauropods such as Europasaurus . Despite its relatively small size, it was the largest representative of the fauna of Laño from the late Campanian or early Maastrichtian. To date, only two fragmentary osteoderms have been found, which may suggest that the armor of Lirainosaurus was not as extensive as that of titanosaurs such as Ampelosaurus .

A revised list of distinguishing features was given in 2013. At the base of the skull each basilar tubercle has a hole in the lower surface. The perforating foramina in the basioccipital, between the basilar tubercle, are missing below the occiput. However, this may be a maturation characteristic. In the front tail vertebrae there is a ledge in the cavity between the posterior joint bosses, which extends between the posterior joint boss and the lateral boss, separating the recesses between the posterior joint boss and the ledge between the lateral protuberance and the vertebral body. Between the rear joint boss and the ledge that extends between the lateral boss and the mandrel boss. For the posterior tail vertebrae, the protrusion between the vertebral column boss and the posterior joint boss does not protrude backwards. The inside of the shoulder blade has a bulge at the top and sometimes a ledge at the bottom. The sternum has a ledge on the lower front, and a protuberance on the front side and a hollow lateral edge. Lirainosaurus ' teeth are pin-shaped. Lirainosaurus also has the typical characteristics of more derived titanosaurs. A hyposphene hypantrum complex is missing. The tail vertebrae are procoelic. The pelvis has a rectangular profile.

Found in the Iberian Peninsula, more precisely in Spain and described in 1999. This genus was defined from a fragment of skull, teeth and postcranial bones from the Upper Cretaceous, from the upper Campanian to the lower Maastrichtian, from Laño, Treviño County , in the north of the Iberian Peninsula. In 2009, new remains found in the municipality of Chera, in the province of Valencia, were described. Vertebrae of the tail, holotype MCNA 7458 and the back, the occipital part of the skull, loose teeth, sternum, humerus, fragments of the ilium and pubis, femur, tibia and osteoderms. In 2013, several vertebrae were described, cervical, dorsal and caudal, as well as dorsal ribs.

The holotype, MCNA 7458 , was found in a layer of the Vitoria formation dating to the late Campanenise. It consists of a proximal tail vertebra. Other bones were designated as paratype. This is specimen MCNA 7439 , a skull fragment, MCNA 7440 and MCNA 7441 , loose teeth, MCNA 7442-7450 , nine vertebrae, MCNA 7451-57 , six tail vertebrae, MCNA 1812 , one tail vertebra, MCNA 7459 , a scapula, MCNA 7460 , a pelvis, MCNA 7461 , a sternum, MCNA 7462-7465 four humeri, MCNA 7466 , a piece of ilium bone, MCNA 7467 a piece of pubis, MCNA 7468 and MCNA 7470; two femurs, MCNA 3160 , one femur; MCNA 7471 , a tibia; MCNA 7472 , one fibula and MCNA 7473 and MCNA 7474 , two osteoderms. The paratypes represent five different individuals and are excavated in three different layers. In 2015 it was reported that the number of bones recovered was 150. In 2011, the base of the skull was described in more detail and in 2012 the teeth, by Verónica Díez -Diaz. In 2013 she described the spine and in a second publication the limbs in detail. Due to all the descriptions, Lirainosaurus was the most studied titanosaur in Europe in 2015.

In 2009, titanosaur finds made at Chera were reported as a cf. Lirainosaurus astibiae and were described in 2011. In 2015 it was concluded that there was no evidence that it was Lirainosaurus .

In the sites where it has been found, they are probably coeval, since they share species such as the dinosaurs Rhabdodon, an Ornithopoda , and Struthiosaurus , an Ankylosauria , the alligatoroid crocodiles Musturzabalsuchus and Acynodon , azhdarchid pterosaurs, and the turtles Dortoka , Polysternon , and Solemys .

It is considered slightly less derived than the Saltasaurids and possibly belonging to a sister group of these. Regarding phylogeny, the combination of characters present in the newly described axial remains supports the placement of Lirainosaurus as a closely related derived lithostrotian titanosaur. with Saltasaurinae. Results from an unpublished SVPCA summary published in 2016 narrow the exact position of Lirainosaurus by placing it closer to Alamosaurus and Opisthocoelicaudia than to Saltasaurus . Later, Diez Díaz et al. in 2018 they erected Lirainosaurinae to accommodate Lirainosaurus , as well as Ampelosaurus and Atsinganosaurus .

Samples have been found at the Bellevue site in the northern Pyrenees, which lies at the base of the Marnes de la Maurine member of the Marnes Rouges Inférieures Formation. Marine biostratagraphic evidence for the formation places its age somewhere between late Campanian and early Maastrichtian. Other contemporary dinosaurs in the Bellevue layer include the titanosaur sauropod Ampelosaurus , the rhabdodont Rhabdodon , and indeterminate elements of ankylosaurian and Dromaeosauridae.

Other material attributed to Lirainosaurus has been found at the locality of Fox-Amphoux-Métisson, where unfortunately no magnetostratigraphic dating has been carried out. However, the local stratigraphy presents the same facies succession as in the Aix-en-Provence basin, which is also found in the late Campanian to early Maastrichtian era.