Nyasasaurus (meaning "Lake Nyasa lizard") is an extinct genus of avemetatarsalian archosaur from the putatively Middle Triassic Manda Formation of Tanzania that may be the earliest known dinosaur.

Previously, the oldest record of dinosaurs was from Brazil and Argentina and dated back to the mid-late Carnian stage, about 233.23 to 231.4 million years ago.

Nyasasaurus comes from a deposit conventionally considered Anisian in age, meaning that it would predate other early dinosaurs by about 12 million years.

[5] In 1967 Charig used the name "Nyasasaurus cromptoni", in a review of Archosauria, but without any description, so it was commonly considered a nomen nudum; the dissertation was also never published.

In 2013 a new description was published by Sterling Nesbitt, Paul Barrett, Sarah Werning and Christian Sidor, including the late Charig as posthumous co-author, ensuring the validity of the name Nyasasaurus, though the specific name was changed to parringtoni, in honour of Parrington.

The specimen was probably associated as evidenced by the bone quality, color and surrounding matrix (dark gray to black carbonate).

[1] The type specimen, NHMUK PV R 6856, is a partial skeleton belonging to an individual estimated to have been two to three metres in length.

However, the vertebral features that link NHMUK PV R 6856 and SAM-PK-K10654, including a connection between two bony projections called the hyposphene and hypantrum, are also found in other Triassic archosaurs.

The 2013 description of Nyasasaurus by Sterling Nesbitt, Paul Barrett, Sarah Werning and Christian Sidor used a second line of evidence, the similar positions of the two specimens on the evolutionary tree, to justify their placement as the same species.

[1] The study also mentioned the similarity between the presacral vertebrae of both specimens of Nyasasaurus parringtoni and those of the enigmatic avemetatarsalian archosaur, Teleocrater rhadinus.

SAM-PK-K10654 possesses several theropod features, including deep pits or fossae in its neck vertebrae, which are not found in NHMUK PV R 6856 because of the limited overlap between the specimens.

[1] The following cladogram depicts these possibilities: Pseudosuchia (including crocodilians) Pterosauromorpha Lagerpetidae Marasuchus lilloensis Silesauridae

Dilophosaurus wetherilli Other theropods (including birds) A large phylogenetic analysis of early dinosaurs and dinosauromorphs by Matthew Baron, David B. Norman and Paul Barrett (2017) found that Nyasasaurus may represent a derived member of Sauropodomorpha most closely related to massospondylids like Massospondylus and Lufengosaurus.

[14] In his 2018 thesis on dinosaur interrelationships, Matthew Baron cast doubt on the referral of "Thecodontosaurus" alophos to Nyasasaurus, arguing that SAM-PK-K10654 instead represents a neotheropod due to the lack of skeletal pneumaticity seen in massospondylids.

However, the Chañares Formation lacks CAZ fauna, instead preserving more advanced species of cynodonts, dicynodonts, and archosauromorphs.