The Manda Formation (also known as the Manda Beds) is a

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma and ...

(

Anisian In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from million years ago until million years ago. The Anisian Age succeeds the Olenekian Age (part of the Lower Triassic Ep ...

?) or possibly

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch ...

(

Carnian The Carnian (less commonly, Karnian) is the lowermost stage of the Upper Triassic Series (or earliest age of the Late Triassic Epoch). It lasted from 237 to 227 million years ago (Ma). The Carnian is preceded by the Ladinian and is followed by t ...

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

Tanzania Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands and ...

. It preserves fossils of many terrestrial vertebrates from the Triassic, including some of the earliest

dinosauromorph Dinosauromorpha is a clade of avemetatarsalian archosaurs (reptiles closer to birds than to crocodilians) that includes the Dinosauria (dinosaurs) and some of their close relatives. It was originally defined to include dinosauriforms and lag ...

archosaur Archosauria () is a clade of diapsids, with birds and crocodilians as the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of the term which includes birds. Extinct archosaurs include non-avian d ...

s. The formation is often considered to be

in age according to general tetrapod biochronology hypotheses and correlations to the ''Cynognathus'' Assemblage Zone of

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...

. However, some recent studies cast doubt to this age, suggesting that parts deposits may actually be younger (

) 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 Late may refer to: * LATE, an acronym which could stand for: ** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia ** Local-authority trading enterprise, a New Zealand business law ** Local average treatment effect, ...

to the

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 Alan Jack Charig (1 July 1927 – 15 July 1997) was an English palaeontologist and writer who popularised his subject on television and in books at the start of the wave of interest in dinosaurs in the 1970s. Charig was, though, first and fo ...

described many more fossils from the bone beds in his Ph.D. thesis for the

University of Cambridge , mottoeng = Literal: From here, light and sacred draughts. Non literal: From this place, we gain enlightenment and precious knowledge. , established = , other_name = The Chancellor, Masters and Schola ...

.Charig, A. J. (1957). New Triassic archosaurs from Tanganyika, including ''Mandasuchus'' and ''Teleocrater'': Dissertation Abstracts. Cambridge University. 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 In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ei ...

, invalidating Stockley's division into two distinct bone beds. Since Charig's description, the Kawinga Formation has been renamed the

Usili Formation The Usili Formation is a Late Permian geologic formation in Tanzania. It preserves fossils of many terrestrial vertebrates from the Permian, including temnospondyls, pareiasaurs, therapsids and the archosauromorph ''Aenigmastropheus''. History ...

, 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

, including the Idusi (K1),

Mchuchuma Mchuchuma in south western Tanzania near Ludewa off the northern tip of Lake Nyasa, is the site of major coal deposits. There is also a thermal power station costing$612m. Recent studies indicate that Mchuchuma/ Ketewaka coal deposits should be c ...

(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

Therapsids

=Dicynodonts

=Cynodonts

Age and correlations

The upper Manda Beds have been assigned to the

Perovkan Land vertebrate faunachrons (LVFs) are Biochronology, biochronological units used to correlate and date terrestrial sediments and fossils based on their tetrapod faunas. First formulated on a global scale by Spencer G. Lucas in 1998, LVFs are primar ...

LVF based on reports that ''Eryosuchus, Shansiodon,'' ''Angonisaurus,'' and ''Scalenodon'' were present. ''Angonisaurus'' does seem to tie the Manda Beds to subzone C of the ''Cynognathus'' Assemblage Zone in the

Karoo Basin The Karoo Supergroup is the most widespread stratigraphy, stratigraphic unit in Africa south of the Kalahari Desert. The group (stratigraphy), supergroup consists of a sequence of units, mostly of nonmarine origin, deposited between the Pennsylvan ...

. However, the relations of the other Tanzanian taxa are more ambiguous. Purported Tanzanian "''Eryosuchus''" and "''Shansiodon''" specimens likely represent new genera unrelated to their supposed namesakes, while ''Scalenodon'' may be endemic to Africa due to the uncertain relations of non-African "''Scalenodon"'' species. One Upper Manda cynodont, ''

Aleodon ''Aleodon'' is an extinct genus of cynodonts that lived from the Middle to the Late Triassic. Relatively few analyses have been conducted to identify the phylogenetic placement of ''Aleodon'', however those that have place ''Aleodon'' as a siste ...

'', has also been found in the ''Dinodontosaurus'' assemblage zone of the

Santa Maria Formation The Santa Maria Formation is a sedimentary rock formation found in Rio Grande do Sul, Brazil. It is primarily Carnian in age (Late Triassic), and is notable for its fossils of cynodonts, "rauisuchian" pseudosuchians, and early dinosaurs and oth ...

in Brazil.

References

{{reflist Geologic formations of Tanzania Triassic System of Africa Triassic Tanzania Anisian Stage Sandstone formations Siltstone formations Marl formations Deltaic deposits Fluvial deposits Lacustrine deposits Paleontology in Tanzania