Isalo III Formation

Isalo III Formation
Isalo III Formation
Stratigraphic range: Bajocian-Bathonian; ~168–165 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Geological formation
Sub-units	Isalo IIIa or Beronono Formation; Isalo IIIb or Sakaraha Formation
Overlies	Isalo II Formation (unconformity)
Lithology
Primary	Sandstone
Other	Claystone, marl
Location
Coordinates	16°36′S 47°00′E / 16.6°S 47.0°E
Approximate paleocoordinates	23°54′S 25°06′E / 23.9°S 25.1°E
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.^[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.

Fossil content

Pterosaur teeth referred to Rhamphorhynchoidea are known from the formation.^[4]

Color key

Taxon	Reclassified taxon	Taxon falsely reported as present	Dubious taxon or junior synonym	Ichnotaxon	Ootaxon	Morphotaxon

Notes
Uncertain or tentative taxa are in small text; ~~crossed out~~ taxa are discredited.

Dinosaurs

Sauropods

Sauropods of the Isalo III Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Archaeodontosaurus	A. descouensi	Ambondromamy, Majunga		Teeth and mandible	A eusauropod sauropod
Lapparentosaurus^[5]	L. madagascariensis	Faritany Majunga		"More than [four] partial skeletons lacking skulls and teeth"	A cetiosaurid sauropod
Narindasaurus^[6]	N. thevenini	Ankinganivalaka		Right tibia, left pubis, caudal vertebrae, right fibula	A turiasaurian sauropod
?Diplodocoidea Indet^[7]	Indeterminate	IIIb	Teeth
?Titanosaurifomes Indet^[7]	Indeterminate	IIIb	Teeth

Theropoda

Theropods of the Isalo III Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Theropoda Indet.	Indeterminate	IIIb		MSNM V6234 "a large, serrated tooth crown"^[8] MSNM V5804 vertebra, isolated teeth representing 8 morphotypes^[9]
Ceratosauria Indet.	Indeterminate	IIIb		MSNM V6235 Pedal ungual^[8]

Crocodyliformes

Crocodyliformes of the Isalo III Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Andrianavoay^[10]	A. baroni	IIIb			A machimosaurine thelattosuchian
Razanandrongobe^[3]	R. sakalavae	IIIb			A notosuchian

References

^ Weishampel et al., 2004, pp.542-543
^ ^a ^b Geiger et al., 2004
^ ^a ^b Dal Sasso et al., 2017
^ 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.
^ Miky Lova Tantely Raveloson; Neil D. L. Clark; Armand H. Rasoamiaramana (2019). "New information on the Madagascan Middle Jurassic sauropod Lapparentosaurus madagascariensis" (PDF). Geosciences. 9 (12): Article 498. Bibcode:2019Geosc...9..498R. doi:10.3390/geosciences9120498.
^ Rafael Royo-Torres; Alberto Cobos; Pedro Mocho; Luis Alcalá (2020). "Origin and evolution of turiasaur dinosaurs set by means of a new 'rosetta' specimen from Spain". Zoological Journal of the Linnean Society. 191 (1): 201–227. doi:10.1093/zoolinnean/zlaa091.
^ ^a ^b Bindellini & Dal Sasso, 2019
^ ^a ^b 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
^ 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.
^ Michela M. Johnson; Mark T. Young; Stephen L. Brusatte (2020). "The phylogenetics of Teleosauroidea (Crocodylomorpha, Thalattosuchia) and implications for their ecology and evolution". PeerJ. 8: e9808. doi:10.7717/peerj.9808. PMC 7548081. PMID 33083104.

Bibliography

Royo Torres, Rafael; Cobos, Alberto; Mocho, Pedro; Alcalá, Luis (2021). "Origin and evolution of turiasaur dinosaurs set by means of a new 'rosetta' specimen from Spain". Zoological Journal of the Linnean Society. 191: 201–227. doi:10.1093/zoolinnean/zlaa091.
Bindellini, Gabriele; Sasso, Cristiano Dal (2019). "Sauropod teeth from the Middle Jurassic of Madagascar, and the oldest record of Titanosauriformes". Papers in Palaeontology. 7: 137–161. doi:10.1002/spp2.1282. S2CID 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". PeerJ. 5: e3481. doi:10.7717/peerj.3481. PMC 5499610. PMID 28690926.
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". Journal of African Earth Sciences. 38 (4): 363–381. Bibcode:2004JAfES..38..363G. doi:10.1016/j.jafrearsci.2004.02.003.
Weishampel, David B.; Dodson, Peter; Osmólska, Halszka, eds. (2004). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 1–880. ISBN 9780520941434.
Thevenin, A (1907). "Paléontologie de Madagascar. IV Dinosauriens" (PDF). Annales de Paléontologie. 2: 121–136.