Isalo III Formation

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.

Isalo III Formation
Stratigraphic range: Bajocian-Bathonian
~168–165 Ma
↓
TypeGeological formation
Sub-unitsIsalo IIIa or Beronono Formation
Isalo IIIb or Sakaraha Formation
OverliesIsalo II Formation (unconformity)
Lithology
PrimarySandstone
OtherClaystone, marl
Location
Coordinates16.6°S 47.0°E / -16.6; 47.0
Approximate paleocoordinates23.9°S 25.1°E / -23.9; 25.1
RegionMahajanga & Fianarantsoa Provinces
Country Madagascar
ExtentMahajanga Basin

Vertebrate fauna

Dinosaurs
Dinosaurs
TaxonSpeciesPresenceRemains NotesImages
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]
Narindasaurus N. thevenini[7][8] Ankinganivalaka Right tibia, left pubis, caudal vertebrae, right fibula Turiasaurian sauropod
Archaeodontosaurus A. descouensi Ambondromamy, Majunga Teeth and mandible
"Bothriospondylus" [1] "B." madagascariensis Faritany Majunga[1] Type:"NHM R2598: mid‐dorsal vertebra." Referred: "NHM R2596–2615, R16588, R16589 dorsal, sacral and caudal vertebrae; elements of the pectoral and pelvic girdles; a partial humerus; fragments of the hindlimbs. Material represents a minimum of three individuals, based on duplication of elements and size differences."[5] Non‐neosauropod eusauropod, distinct from Lapparentosaurus, also formerly referred to by the same name.[5]
Theropoda Indeterminate IIIb MSNM V6234 "a large, serrated tooth crown"[9] MSNM V5804 vertebra, isolated teeth representing 8 morphotypes[10]
Ceratosauria Indeterminate IIIb MSNM V6235 Pedal ungual[9]
?Diplodocoidea[11] Indeterminate IIIb Teeth
?Titanosaurifomes[11] Indeterminate IIIb Teeth

Crocodyliformes
Crocodyliformes
TaxonSpeciesPresenceNotesImages
Razanandrongobe[3] R. sakalavae IIIb Notosuchian

Mammals
Mammals
TaxonSpeciesPresenceNotesImages
AmbondroA. mahaboIIIb[12]

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

See also

References
  1. Weishampel et al., 2004, pp.542-543
  2. Geiger et al., 2004
  3. 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. 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". Geosciences. 9 (12): 498. doi:10.3390/geosciences9120498. ISSN 2076-3263.
  7. Royo Torres et al., 2020
  8. Thevenin, 1907
  9. 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. 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
  • É. Buffetaut. 2005. A new sauropod dinosaur with prosauropod-like teeth from the Middle Jurassic of Madagascar. Bulletin de la Société Géologique de France 176(5):467-473
  • S. Maganuco, C. Dal Sasso, and G. Pasini. 2006. A new large predatory archosaur from the Middle Jurassic (Bathonian) of Madagascar. Atti della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano 147(1):19-51
  • J. J. Flynn, J. M. Parrish, B. Rakotosamimanana, W. F. Simpson, and A. R. Wyss. 1999. A Middle Jurassic mammal from Madagascar. Nature 401:57-60
  • A. Ogier. 1975. Etude de Nouveaux Ossements de Bothriospondylus (Sauropode) d'un Gisement du Bathonien de Madagascar [Study of New Bones of Bothriospondylus (Sauropod) from a Locality from the Bathonian of Madagascar]. Sciences Naturelles, Université de Paris VI 1-111
  • M. Collignon. 1954. Decouverte de dinosauriens a Tsinjorano, district d'Ambato-Boeni [Discovery of dinosaurs at Tsinjorano, Ambato-Boeni district]. Bulletin de l'Académie Malgache 31:59-61
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.