Ntawere Formation

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

Ntawere Formation
Stratigraphic range: Anisian
~247–242 Ma
TypeGeological formation
Sub-unitsLower Ntawere, Upper Ntawere
UnderliesRed Marls
OverliesEscarpment Grit
Lithology
PrimaryMudstone
OtherSandstone, marl
Location
Coordinates10°48′S 33°06′E / 10.8°S 33.1°E / -10.8; 33.1Coordinates: 10°48′S 33°06′E / 10.8°S 33.1°E / -10.8; 33.1
Approximate paleocoordinates53°36′N 20°36′E / 53.6°N 20.6°E / 53.6; 20.6
RegionEastern Province
Country Zambia
ExtentLuangwa Basin
Ntawere Formation is located in Zambia
Ntawere Formation
Ntawere Formation (Zambia)

GeologyEdit

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]

PaleobiotaEdit

InvertebratesEdit

Invertebrates of the Ntawere Formation
Taxon Member Material Notes
Unio karooensis Upper Ntaware Shells A freshwater unionid bivalve

FishEdit

Fish of the Ntawere Formation
Taxon Member Material Notes
Hybodontoidei indet. Upper Ntaware Fin spines An indeterminate non-hybodontid hybodontoid shark, similar to Lissodus and Lonchidion
Ptycoceratodontidae indet. Lower Ntaware, Upper Ntawere Tooth plates An indeterminate lungfish, similar to Ptychoceratodus

AmphibiansEdit

Amphibians of the Ntawere Formation
Taxon Member Material Notes Images
Batrachosuchus concordi Upper Ntaware A skull and forelimbs A brachyopid stereospondyl
Cherninia megarhina Upper Ntaware A partial skull A mastodonsaurid stereospondyl
"Stanocephalosaurus" pronus Upper Ntaware A skull A new species of capitosauroid, likely not part of the genus Stanocephalosaurus
Stereospondyli indet. Upper Ntaware Vertebrae and part of a jaw Indeterminate stereospondyl material. The jaw fragment may belong to a rhinesuchid, lydekkerinid, or rhytidosteid

SynapsidsEdit

Synapsids of the Ntawere Formation
Taxon Member Material Notes Images
Cricodon metabolus Upper Ntaware A partial skeleton A trirachodontid cynodont
Cynognathus crateronotus Lower Ntaware Teeth, vertebrae, partial humerus, ilium A cynognathian cynodont
Diademodon tetragonus Lower Ntaware A skull A diademodontid cynodont
"Kannemeyeria" latirostris Lower Ntaware A skull A kannemeyeriiform dicynodont, possibly a species of Kannemeyeria or Dolichuranus
Kannemeyeria lophorhinus Lower Ntaware A skull A kannemeyeriid dicynodont
Luangwa drysdalli Upper Ntaware Skulls and postcranial material A traversodontid cynodont
Sangusaurus edentatus Upper Ntaware A partial skull A stahleckeriid dicynodont
Traversodontidae sp. Upper Ntaware Skulls and postcranial material An unnamed species of gomphodont-like traversodontid cynodont
Zambiasaurus submersus Upper Ntaware A skull fragment A stahleckeriid dicynodont

ArchosauromorphsEdit

Archosauromorphs of the Ntawere Formation
Taxon Member Material Notes Images
Archosauriformes indet. Upper Ntaware Teeth Various indeterminate large carnivorous archosauriforms, likely loricatans
Archosauromorpha indet. Upper Ntaware A neck vertebra An indeterminate archosauromorph, possibly an allokotosaur
Dinosauriformes indet. Upper Ntaware A partial fibula A large dracohortian, likely a silesaurid
Loricata indet. Upper Ntaware Vertebrae An indeterminate large archosaur, similar to Stagonosuchus
Lutungutali sitwensis Upper Ntaware An ilium A basal silesaurid
Shuvosauridae indet. Upper Ntaware Part of a femur An indeterminate shuvosaurid archosaur similar to Shuvosaurus and the indeterminate "Moenkopi poposauroid"
Silesauridae indet. Upper Ntaware A maxilla, femurs, and material from the hip, ankle, and foot Indeterminate basal silesaurid material comparable to Asilisaurus and Lutungutali

See alsoEdit

ReferencesEdit

  1. ^ a b c 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. doi:10.1080/02724634.2017.1410484. ISSN 0272-4634. S2CID 133878741.

Further readingEdit

  • K. D. Angielczyk, J. S. Steyer, C. A. Sidor, R. H. H. Smith, R. L. Whatley and S. Tolan. 2014. Permian and Triassic Dicynodont (Therapsida: Anomodontia) Faunas of the Luangwa Basin, Zambia: Taxonomic Update and Implications for Dicynodont Biogeography and Biostratigraphy. In C. F. Kammerer, K. D. Angielczyk and J. Fröbisch (eds.), Early Evolutionary History of the Synapsida 93-138
  • A. R. Drysdall and J. W. Kitching. 1963. A re-examination of the Karroo succession and fossil localities of part of the Upper Luangwa Valley. Memoir of the Geological Survey of Northern Rhodesia 1:1-62