Isalo III Formation

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Isalo III Formation
Stratigraphic range: Bajocian-Bathonian
~168–165  Ma
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S
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Type Geological formation
Sub-unitsIsalo IIIa or Beronono Formation
Isalo IIIb or Sakaraha Formation
Overlies Isalo II Formation (unconformity)
Lithology
Primary Sandstone
Other Claystone, marl
Location
Coordinates 16°36′S47°00′E / 16.6°S 47.0°E / -16.6; 47.0
Approximate paleocoordinates 23°54′S25°06′E / 23.9°S 25.1°E / -23.9; 25.1
Region Mahajanga & Fianarantsoa Provinces
CountryFlag of Madagascar.svg  Madagascar
Extent Mahajanga Basin
Madagascar physical map.svg
Blue pog.svg
Blue pog.svg
Blue pog.svg
Blue pog.svg
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The Isalo III Formation is a geological formation in Madagascar, off the eastern coast of Africa. It dates back to the Middle Jurassic. [1] The use of the term "Isalo III" is somewhat controversial as the two prior units Isalo I and II are Triassic cross-bedded sandstone units that form a continuous depositional sequence, while the "Isalo III" sandstones are not part of the same depositional sequence, and were deposited considerably later. and are perhaps better treated as part of several separate formations. [2] It is traditionally divided into two subunits the lower, Bajocian aged Isalo IIIa unit also known as the Beronono Formation and the upper, Bathonian aged Isalo IIIb unit also known as the Sakaraha Formation or Sakahara Formation. [3] The Sakaraha Formation consists of sandstones, marls and carbonates and represents a coastal plain environment, and is laterally equivalent to the predominantly carbonate Bemaraha Formation, which represents a coastal barrier lagoon complex. [2] The formation is found in the northwest and in the southeast of the country and has provided a variety of fossils.

Contents

Vertebrate fauna

Dinosaurs

TaxonSpeciesPresenceRemainsNotesImages
Lapparentosaurus [1] L. madagascariensis Faritany Majunga [1] "More than [four] partial skeletons lacking skulls and teeth" [4] Considered a titanosauriform by Mannion (2010), [5] Suggested to be a Cetiosaurid by Raveloson et al (2019) [6]
Lapparentosaurus femur.png
Narindasaurus N. thevenini [7] [8] AnkinganivalakaRight tibia, left pubis, caudal vertebrae, right fibula Turiasaurian sauropod
Lapparentosaurus madagascariensis left pubis.jpg
Archaeodontosaurus A. descouensi Ambondromamy, Majunga Teeth and mandible
Archaeodontosaurus dent fond.jpg
Theropoda IndeterminateIIIbMSNM V6234 "a large, serrated tooth crown" [9] MSNM V5804 vertebra, isolated teeth representing 8 morphotypes [10]
Ceratosauria IndeterminateIIIbMSNM V6235 Pedal ungual [9]
 ?Diplodocoidea [11] IndeterminateIIIbTeeth
 ?Titanosaurifomes [11] IndeterminateIIIbTeeth

Crocodyliformes

TaxonSpeciesPresenceNotesImages
Razanandrongobe [3] R. sakalavaeIIIb Notosuchian
Razanandrongobe-fig2-MNHTspecimens.jpg

Mammals

TaxonSpeciesPresenceNotesImages
Ambondro A. mahaboIIIbA member of Australosphenida [12]
Ambondro lingual.jpg

Pterosaur teeth referred to Rhamphorhynchoidea are known from the formation. [13]

See also

Related Research Articles

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<i>Narindasaurus</i> Genus of sauropod dinosaur (fossil)

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References

  1. 1 2 3 Weishampel et al., 2004, pp.542-543
  2. 1 2 Geiger et al., 2004
  3. 1 2 Dal Sasso et al., 2017
  4. "Table 13.1," in Weishampel et al., 2004, p.266
  5. Mannion, Philip D. (March 2010). "A revision of the sauropod dinosaur genus ' Bothriospondylus ' with a redescription of the type material of the Middle Jurassic form ' B. madagascariensis '". Palaeontology. 53 (2): 277–296. Bibcode:2010Palgy..53..277M. doi: 10.1111/j.1475-4983.2009.00919.x .
  6. Raveloson, Miky Lova Tantely; Clark, Neil D. L.; Rasoamiaramana, Armand H. (2019-11-27). "New Information on the Madagascan Middle Jurassic Sauropod Lapparentosaurus madagascariensis" (PDF). Geosciences. 9 (12): 498. Bibcode:2019Geosc...9..498R. doi: 10.3390/geosciences9120498 . ISSN   2076-3263.
  7. Royo Torres et al., 2020
  8. Thevenin, 1907
  9. 1 2 Maganuco S, Cau A, Dal Sasso C, Pasini G.2007. Evidence of large theropods from the Middle Jurassic of the Mahajanga Basin, NW Madagascar, with implications for ceratosaurian pedal ungual evolution.  Atti della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale in Milano 148(II):261-271
  10. Maganuco S., Cau A. & Pasini G.. 2005 First description of theropod remains from the Middle Jurassic (Bathonian) of Madagascar. Atti Soc. it. Sci. nat. Museo civ. Stor. nat. Milano. 146, 165–202.
  11. 1 2 Bindellini & Dal Sasso, 2019
  12. Ambondromahabo, M-8 at Fossilworks.org
  13. Dal Sasso C. & Pasini G., 2003 - First record of pterosaurs (Pterosauria, Archosauromorpha, Diapsida) in the Middle Jurassic of Madagascar. Atti della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale in Milano, 144 (II): 281-296.

Bibliography

Further reading