Isalo III Formation explained

Isalo III Formation
Period:	Bathonian
Age:	Bajocian-Bathonian ~
Type:	Geological formation
Prilithology:	Sandstone
Otherlithology:	Claystone, marl
Subunits:	Isalo IIIa or Beronono Formation Isalo IIIb or Sakaraha Formation
Overlies:	Isalo II Formation (unconformity)
Coordinates:	-16.6°N 47°W
Paleocoordinates:	-23.9°N 25.1°W
Region:	Mahajanga & Fianarantsoa Provinces
Country:	Madagascar
Extent:	Mahajanga Basin

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. 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. The formation is found in the northwest and in the southeast of the country and has provided a variety of fossils.

Vertebrate fauna

Dinosaurs

Taxon	Species	Presence	Remains	Notes	Images
Lapparentosaurus	L. madagascariensis	Faritany Majunga	"More than [four] partial skeletons lacking skulls and teeth"^[3]	Considered a titanosauriform by Mannion (2010),^[4] Suggested to be a Cetiosaurid by Raveloson et al (2019)^[5]
Narindasaurus	N. thevenini^[6] ^[7]	Ankinganivalaka	align=center	Right tibia, left pubis, caudal vertebrae, right fibula	Turiasaurian sauropod
Archaeodontosaurus	A. descouensi	Ambondromamy, Majunga	Teeth and mandible
Theropoda	Indeterminate	IIIb	MSNM V6234 "a large, serrated tooth crown"^[8] MSNM V5804 vertebra, isolated teeth representing 8 morphotypes^[9]
Ceratosauria	Indeterminate	IIIb	MSNM V6235 Pedal ungual
?Diplodocoidea^[10]	Indeterminate	IIIb	Teeth
?Titanosaurifomes	Indeterminate	IIIb	Teeth

Mammals

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

See also

• List of dinosaur-bearing rock formations
• List of fossiliferous stratigraphic units in Madagascar
• Geology of Madagascar

References

Bibliography

• Rafael . Royo Torres . Alberto . Cobos . Pedro . Mocho . Luis . Alcalá . Origin and evolution of turiasaur dinosaurs set by means of a new 'rosetta' specimen from Spain . . 2021 . 191 . 201–227. 10.1093/zoolinnean/zlaa091. free .
• Bindellini . Gabriele . Sasso . Cristiano Dal . 2019 . Sauropod teeth from the Middle Jurassic of Madagascar, and the oldest record of Titanosauriformes . . 7 . 137–161. 10.1002/spp2.1282. 203376597 .
• Dal Sasso . Cristiano . Pasini . Giovanni . Fleury . Guillaume . Maganuco . Simone . 2017 . Razanandrongobe sakalavae, a gigantic mesoeucrocodylian from the Middle Jurassic of Madagascar, is the oldest known notosuchian . . 5 . e3481. 10.7717/peerj.3481 . 28690926 . 5499610 . free .
• Geiger . Markus . Clark . David Norman . Mette . Wolfgang . 2004 . Reappraisal of the timing of the breakup of Gondwana based on sedimentological and seismic evidence from the Morondava Basin, Madagascar . . 38 . 4 . 363–381. 10.1016/j.jafrearsci.2004.02.003 . 2004JAfES..38..363G .
• Book: Weishampel . David B. . Dodson . Peter . Osmólska . Halszka . 2004 . The Dinosauria . 2nd . Berkeley . University of California Press . 1–880 . 9780520941434.
• Thevenin . A . 1907 . Paléontologie de Madagascar. IV Dinosauriens . . 2 . 121–136.

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

Notes and References

1. Weishampel et al., 2004, pp.542-543
2. Geiger et al., 2004
3. "Table 13.1," in Weishampel et al., 2004, p.266
4. 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. en. 53. 2. 277–296. 10.1111/j.1475-4983.2009.00919.x. 2010Palgy..53..277M . free.
5. 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. en. 9. 12. 498. 10.3390/geosciences9120498. 2019Geosc...9..498R. 2076-3263. free.
6. Royo Torres et al., 2020
7. Thevenin, 1907
8. 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
9. 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.
10. Bindellini & Dal Sasso, 2019
11. Dal Sasso et al., 2017
12. http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=92151 Ambondromahabo, M-8
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.