Leonerasaurus was a small non-sauropod sauropodomorph, showing an unusual combination of basal and derived characters.

[1] The generic name is derived from Leoneras, in reference to the lithostratigraphic unit where this taxon was found, and saurus, "lizard" (Latinized Greek).

The specific name taquetrensis refers to the Sierras de Taquetrén, where Las Leoneras Formation crops out in Central Patagonia.

Near the area where it touches the contralateral element at the tip of the lower jaw (the symphysis) the bone is straight and only gently arched medially, as is seen in basal sauropods.

More derived sauropods (eusauropods) have medially broadly arching symphyseal regione and anterior portions of the tooth row.

Teeth further back in the dentary are nearly all damaged, but a not erupted tooth has large denticles similar to basal sauropodomorphs.

[1] The anterior teeth are spoon-shaped, with the outer surface convex (bulging out), the inner one concave (hollowed out), again resembling basal sauropods.

[1] In the trunk, the vertebrae show typical non-sauropod characters, such as relatively long and low neural arches with a narrow anterior ridge (the anteriormost dorsal vertebrae have slightly high neural arches), an anteriorly placed parapophysis (one of the articulation points for the ribs), and lack of or less strong development of certain laminae (thin ridges).

A cladogram after Pol, Garrido & Cerda, 2011,[1] illustrates a possible placing of Leonerasaurus in Sauropodomorpha: Saturnalia Pantydraco Thecodontosaurus Efraasia Ruehleia Plateosaurus Riojasaurus Massospondylus Coloradisaurus Lufengosaurus Gyposaurus Yunnanosaurus Anchisaurus Aardonyx Leonerasaurus Melanorosaurus Antetonitrus Lessemsaurus Kotasaurus Vulcanodon Eusauropoda The following cladogram shows the position of Leonerasaurus within Massopoda, according to Oliver W. M. Rauhut and colleagues, 2020:[6] Eucnemesaurus Riojasaurus Sarahsaurus Yunnanosaurus Jingshanosaurus Seitaad Coloradisaurus Glacialisaurus Lufengosaurus Massospondylus Adeopapposaurus Leyesaurus Xingxiulong Anchisaurus Leonerasaurus Mussaurus Aardonyx Sefapanosaurus Meroktenos Melanorosaurus Camelotia Lessemsaurus Antetonitrus Ingentia Blikanasaurus Pulanesaura Gongxianosaurus Schleitheimia Isanosaurus Tazoudasaurus Sauropoda