The Manda Formation (also known as the Manda Beds) is a Middle Triassic (Anisian?) or possibly Late Triassic (Carnian?) geologic formation in Tanzania. It preserves fossils of many terrestrial vertebrates from the Triassic, including some of the earliest dinosauromorph archosaurs. The formation is often considered to be Anisian in age according to general tetrapod biochronology hypotheses and correlations to the Cynognathus Assemblage Zone of South Africa. However, some recent studies cast doubt to this age, suggesting that parts deposits may actually be younger (Carnian) in age.
History of study
One of the first to study rocks of the Manda Formation was British geologist G. M. Stockley. In 1932, Stockley explored the geology of the Ruhuhu Basin in Tanzania. He called a series of layers dating from the Late Carboniferous to the Middle Triassic the Songea Series and divided it into eight units labelled K1-K8. Stockley was also the first to describe fossils from these rocks, naming an older layer the "Lower Bone Bed" and a younger layer the "Upper Bone Bed".
In 1957, paleontologist Alan J. Charig described many more fossils from the bone beds in his Ph.D. thesis for the University of Cambridge. Charig renamed the youngest of Stockley's units in 1963, calling unit K6 the Kawinga Formation, K7 the Kingori Sandstones, and K8 the Manda Formation. Fossils were identified in many strata, invalidating Stockley's division into two distinct bone beds. Since Charig's description, the Kawinga Formation has been renamed the Usili Formation, the Kingori Sandstones have become the Kingori Sandstone Member of the Manda Formation, and Charig's original Manda Formation has become a subunit of the formation called the Lifua Member. Six formations and one informal unit are currently recognized in the Songea Group (Ruhuhu basin) rocks range in age from Pennsylvanian to Anisian, including the Idusi (K1), Mchuchuma (K2), Mbuyura (K3), Mhukuru (K4), Ruhuhu (K5), and Usili (K6) formations and the informal Manda Beds, which include the Kingori Sandstone (K7) and Lifua Member (K8).
Paleobiota
Tetrapods
Temnospondyls
Parareptiles
Archosauromorphs
Archosaurs
{ | class="wikitable sortable" |- ! Taxon !! Species !! Member !! class="unsortable" | Material !! class="unsortable" | Notes !! class="unsortable" | Images |- |Asilisaurus |A. kongwe || Lifua || || A silesaurid dinosauriform || |- | Hypselorhachis | H. mirabilis || Lifua || NHMUK R16586, a complete dorsal vertebra || A sail-backed archosaur possibly belonging to the family Ctenosauriscidae || |- | Mambawakale | M. ruhuhu || Lifua Member || NHMUK R36620, partial skull and some postcranial fragments || A paracrocodylomorph; previously informally known as "Pallisteria angustimentum". || |- | Mandasuchus | M. tanyauchen ||Lifua Member || NHMUK R6792, partial mandible and postcranial skeletons ||A paracrocodylomorph | |- | Nundasuchus | N. songeaensis || Lifua || NMT RB48, partial skeleton and skull || An archosaur, possibly suchian ||
|-
| Nyasasaurus
| N. parringtoni || Lifua || NHMUK R6856, a right humerus, three partial presacral vertebrae and three sacral vertebrae. SAM-PK-K10654 is also potentially referable - see "Thecodontosaurus" alophos below. || A theropod or an ornithischian or the most advanced non-dinosaurian dinosauriform. Possibly the oldest dinosaur. || |- | Teleocrater | T. rhadinus || Lifua || NHMUK R6795, vertebrae, limb bones and other elements. Additional material referred from two other individuals. || An early avemetatarsalian||
|-
| style="background:#fbdddb;" | "Thecodontosaurus" | style="background:#fbdddb;" | "T." alophos || style="background:#fbdddb;" | Lifua Member || style="background:#fbdddb" | SAM-PK-K10654, three neck vertebrae and two rear presacral vertebrae || style="background:#fbdddb" | A probable subjective senior synonym of Nyasasaurus, first identified as a sauropodomorph dinosaur. || style="background:#fbdddb;" | |- | Unnamed archosaur | Unidentified. || Lifua || Nearly complete skull and partial skeleton || A stem-aetosaur || |- |}