Pisanosaurus facts for kids

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Pisanosaurus
Temporal range: Upper Triassic, 228–216.5 mya
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: Dinosauria
Order: Ornithischia
Family: Pisanosauridae
Casamiquela, 1967
Genus: Pisanosaurus
Casamiquela, 1967

Pisanosaurus (/pɪsænəˈsɔːrəs/) is an extinct genus of primitive dinosauriform 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 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 the Ischigualasto Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina.

Classification

The exact classification of Pisanosaurus has been the topic of debate by scientists for over 40 years; until 2017, the consensus was 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, but recently, some have begun to consider it a non-dinosaurian silesaurid.

Description

Pisanosaurus NT small
Restoration of Pisanosaurus as a silesaurid

Based on the known fossil elements from a partial skeleton, Pisanosaurus was a small, lightly built dinosauriform approximately 1 m (3 ft 3 in) in length. Its weight was between 2.27–9.1 kg (5–20 lb). These estimates vary due to the incompleteness of the holotype specimen PVL 2577. The orientation of the pubis is uncertain, with some skeletal reconstructions having it projecting down and forward (the propubic condition) similar to that of the majority of saurischian dinosaurs.

According to a redescription by José Bonaparte in 1976, Pisanosaurus has some distinctive characteristics. The acetabulum, the hip-joint, is open. The pedicels of the ilium are short, resulting in a low axially long acetabulum. The upper region of the ischium is wide, larger than that of the pubic bone. The metacarpals of the hand are apparently elongated, measuring about fifteen millimeters.

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