Yamanasaurus

Yamanasaurus (meaning "Yamana lizard") is an extinct genus of saltasaurine titanosaur dinosaur from the Río Playas Formation of Ecuador, which dates to the Maastrichtian epoch of the Cretaceous period (approximately 66.9 million years ago). The type and only species is Yamanasaurus lojaensis. It is the first non-avian dinosaur described from Ecuador.^[1]

Yamanasaurus Temporal range: Maastrichtian, 66.9 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Artistic depiction of Yamanasaurus
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	†Sauropodomorpha
Clade:	†Sauropoda
Clade:	†Macronaria
Clade:	†Titanosauria
Family:	†Saltasauridae
Subfamily:	†Saltasaurinae
Genus:	†Yamanasaurus Apesteguía et al., 2019
Type species
†Yamanasaurus lojaensis Apesteguía et al., 2019

The holotype, consisting of fragments of a humerus, ulna, tibia, two sacral vertebrae and a single caudal, was discovered in 2017.

Etymology

The genus Yamanasaurus refers to the locality of Yamana, where the bones were found, which is located in southern Ecuador, about fifty kilometers from the Peruvian border.

The specific name, lojaensis, composed of loja and the Latin suffix -ensis, meaning "which lives in, which inhabits", was given in reference to the town of Loja, where the discovery was presented and where part of its study was carried out.^[1]

Description

As a saltasaurinid sauropod, Yamanasaurus is distinguished by a stocky, quadripedal body, an elongated neck and tail and a small head, although its neck and overall size are smaller than the average sauropod, as it is estimated to have been around 6 m (20 ft) long^[2][3]. Like other saltasaurinid, it also likely had a protective armour^[3]made of osteoderms.

The morphology, size and age of the specimen suggest that Yamanasaurus is closely related to Neuquensaurus, being the closest known saltasaurinid (having been discovered in Argentina and Uruguay). This herbivore probably fed on low vegetation.

Yamanasaurus is further characterised by its anterior to mid-tail vertebrae having a dorsoventrally compressed condyle, with the posterior end raised above the midline, without a longitudinal ventral ridge. The internal structure is spongy and lacks internal cavities. The last centrum of the sacral vertebra is as long as it is high, with a small shallow ovoid cavity on the lateral side. The radius is robust with a flattened diaphysis and a marked constriction just below the epiphysis, which has a concave, heptagonal proximal surface^[1].

Discovery

The discovery was made in 2017 by Francisco Celi, an octogenarian resident of Yamana, who, after finding a vertebra of the animal informed university professor Galo Guamán and his geology students, who were on a field trip in the area.

On the subject of its dating, Galo Guamán, who ended up in charge of the study, explains: “The age of the fossils was determined by geological correlation, thanks to rock samples that correspond to the Maastrichtian period, the last period of the Cretaceous, before the fall of the meteorite that caused the extinction of the dinosaurs.”^[3]