Ntawere Formation

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Ntawere Formation
Stratigraphic range: Anisian
~247–242  Ma
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Type Geological formation
Sub-unitsLower Ntawere, Upper Ntawere
Underlies Red Marls
Overlies Escarpment Grit
Lithology
Primary Mudstone
Other Sandstone, marl
Location
Coordinates 10°48′S33°06′E / 10.8°S 33.1°E / -10.8; 33.1
Approximate paleocoordinates 53°36′N20°36′E / 53.6°N 20.6°E / 53.6; 20.6
Region Eastern Province
Country Zambia
Extent Luangwa Basin
Zambia relief location map.svg
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Ntawere Formation (Zambia)

The Ntawere Formation is a Middle Triassic (Anisian) geological formation in Zambia, preserving fossils of synapsids, archosaurs, and temnospondyls. [1]

Contents

Geology

Several different facies are present in the Ntawere Formation, reconstructing a floodplain environment. The coarsest facies are trough cross-bedded conglomeratic sandstone full of mineral concretions. These coarse deposits formed in ancient channels such as riverbeds. Another type of facies involves thick beds of mudstone interbedding with thinner layers of fine-grained sandstone, indicating alternating low- and high-energy water flow within the channels. Graded sandstone to mudstone overbank deposits (complete with ripple marks) occur near channel deposits. Extensive successions of laminated or massive mudstone are common, often containing slickensides, calcareous nodules or layers (marls), and/or hematite nodules. These types of thick mud/marl layers likely formed in more quiet parts of the floodplain isolated from turbulent channels. [1]

The floodplain was seemingly more active during the deposition of the Lower Ntaware Formation, as coarser sandstone channel fills are prevalent in that section while extensive mudstone layers are more common in the Upper Ntaware Formation. Fossils are typically found preserved in calcareous nodules in the mudstone of the Upper Ntaware, although they occur in some parts of the Lower Ntaware as well. The Ntaware Formation is an example of red beds, which are typically deposited in warm environments with seasonal ponds and rivers tied to wet and dry seasons. [1]

Paleobiota

Invertebrates

Invertebrates of the Ntawere Formation
TaxonMemberMaterialNotes
Unio karooensis Upper NtawareShellsA freshwater unionid bivalve

Fish

Fish of the Ntawere Formation
TaxonMemberMaterialNotes
Hybodontoidei indet.Upper NtawareFin spinesAn indeterminate non-hybodontid hybodontoid shark, similar to Lissodus and Lonchidion
Ptycoceratodontidae indet.Lower Ntaware, Upper NtawereTooth platesAn indeterminate lungfish, similar to Ptychoceratodus

Amphibians

Amphibians of the Ntawere Formation
TaxonMemberMaterialNotesImages
Batrachosuchus concordi Upper NtawareA skull and forelimbsA brachyopid stereospondyl Batrachosuchus1DB.jpg
Cherninia megarhina Upper NtawareA partial skullA mastodonsaurid stereospondyl Cherninia12.jpg
"Stanocephalosaurus" pronusUpper NtawareA skullA new species of capitosauroid, likely not part of the genus Stanocephalosaurus
Stereospondyli indet.Upper NtawareVertebrae and part of a jawIndeterminate stereospondyl material. The jaw fragment may belong to a rhinesuchid, lydekkerinid, or rhytidosteid

Synapsids

Synapsids of the Ntawere Formation
TaxonMemberMaterialNotesImages
Cricodon metabolus Upper NtawareA partial skeletonA trirachodontid cynodont
Cynognathus crateronotus Lower NtawareTeeth, vertebrae, partial humerus, ilium A cynognathian cynodont Cynognathus NT small.jpg
Diademodon tetragonus Lower NtawareA skullA diademodontid cynodont Diademodon.jpg
"Kannemeyeria" latirostrisLower NtawareA skullA kannemeyeriiform dicynodont, possibly a species of Kannemeyeria or Dolichuranus
Kannemeyeria lophorhinus Lower NtawareA skullA kannemeyeriid dicynodont
Luangwa drysdalli Upper NtawareSkulls and postcranial materialA traversodontid cynodont
Sangusaurus edentatus Upper NtawareA partial skullA stahleckeriid dicynodont
Traversodontidae sp.Upper NtawareSkulls and postcranial materialAn unnamed species of gomphodont-like traversodontid cynodont
Zambiasaurus submersus Upper NtawareA skull fragmentA stahleckeriid dicynodont

Archosauromorphs

Archosauromorphs of the Ntawere Formation
TaxonMemberMaterialNotesImages
Archosauriformes indet.Upper NtawareTeethVarious indeterminate large carnivorous archosauriforms, likely loricatans
Archosauromorpha indet.Upper NtawareA neck vertebraAn indeterminate archosauromorph, possibly an allokotosaur
Dinosauriformes indet.Upper NtawareA partial fibula A large dracohortian, likely a silesaurid
Loricata indet.Upper NtawareVertebraeAn indeterminate large archosaur, similar to Stagonosuchus
Lutungutali sitwensis Upper NtawareAn ilium A basal silesaurid Lutungutali.png
Shuvosauridae indet.Upper NtawarePart of a femur An indeterminate shuvosaurid archosaur similar to Shuvosaurus and the indeterminate "Moenkopi poposauroid"
Silesauridae indet.Upper NtawareA maxilla, femurs, and material from the hip, ankle, and footIndeterminate basal silesaurid material comparable to Asilisaurus and Lutungutali

See also

References

  1. 1 2 3 Peecook, Brandon R.; Steyer, J. Sébastien; Tabor, Neil J.; Smith, Roger M. H. (2017-11-29). "Updated geology and vertebrate paleontology of the Triassic Ntawere Formation of northeastern Zambia, with special emphasis on the archosauromorphs". Journal of Vertebrate Paleontology. 37 (sup1): 8–38. Bibcode:2017JVPal..37S...8P. doi:10.1080/02724634.2017.1410484. ISSN   0272-4634. S2CID   133878741.

Further reading