Pisanosaurus

Pisanosaurus (pron.:"PIE-san-uh-SAWR-us") is an extinct genus of primitive ornithischian dinosaur that lived approximately 228 to 216 million years ago during the latter part of the Triassic Period in what is now South America. It was a small, lightly-built, ground-dwelling, bipedal herbivore, that could grow up to an estimated 1 m (3.3 ft) long. Only one species, the type, Pisanosaurus mertii, is known, based on a single partial skeleton discovered in Argentina's Ischigualasto Formation.

The exact classification of Pisanosaurus has been the topic of debate by scientists for over 40 years; the current consensus is that Pisanosaurus is the oldest known ornithischian, part of a diverse group of dinosaurs which lived during nearly the entire span of the Mesozoic Era.

Etymology
The genus name Pisanosaurus, means "Mr. Pisano’s lizard", and is derived the "Pisano" in honor of Argentine paleontologist Juan A. Pisano of La Plata Museum, and "sauros" from the Greek (σαύρα) meaning "lizard".[1][2] Pisanosaurus was described and named by Argentine paleontologist Rodolfo Casamiquela in 1967. The type and only valid species known today is Pisanosaurus mertii’’. The specific name honors the late Araucanian naturalist Carlos Merti.

Discovery and naming
Pisanosaurus is known from a single fragmented skeleton discovered y Galileo J. Scaglia at the Agua de Las Catas locality in the Ischigualasto Formation, in La Rioja, Argentina.[3] It is based on a specimen given the designation PVL 2577, which consists of a partial skull with a fragmentary right maxilla with teeth, and incomplete right mandibular ramus (lower jaw), six incomplete cervical vertebrae, seven incomplete dorsal vertebrae, molds of five sacral vertebrae, a rib and several rib fragments, a fragmentary scapula, a coracoid, a fragmentary ilium, ischium and pubis, an impression of 3 metacarpals, complete femora, the right tibia, the right fibula, with an articulated astragalus and calcaneum, a tarsal element with a metatarsal, metatarsals III and IV, three phalanges from metatarsal III and four metatarsals and the ungual from metatarsal IV, and an indeterminate long bone fragment.