The Isalo III Formation is a geological formation in Madagascar, off the eastern coast of Africa. It dates back to the Middle Jurassic.Weishampel et al., 2004, pp.542-543 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.Geiger et al., 2004 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.
Fossil content Pterosaur teeth referred to Rhamphorhynchoidea are known from the formation.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.
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 L. madagascariensis Faritany Majunga "More than [four] partial skeletons lacking skulls and teeth" A cetiosaurid sauropod Narindasaurus N. thevenini Ankinganivalaka Right tibia, left pubis, caudal vertebrae, right fibula A turiasaurian sauropod ?Diplodocoidea indet.Bindellini & Dal Sasso, 2019 Indeterminate IIIb Teeth ?Titanosaurifomes indet. Indeterminate IIIb Teeth
Theropoda Theropods of the Isalo III Formation Genus Species Location Stratigraphic position Material Notes ImagesAbelisauridae indet.IndeterminateIIIbMSNM V5778, V5779, V5781, V5789, V5799, V5809; FC-DPV 3531; PVL 3672, 515 4062-1 to 4062-4, 4173, 4174, 4175; NHMUK R4190 - all isolated shed crownsThe earliest record of Abelisauridae Theropoda indet. Indeterminate IIIb MSNM V6234 "a large, serrated tooth crown"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 MSNM V5804 vertebra, isolated teeth representing 8 morphotypesMaganuco 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. Ceratosauria indet. Indeterminate IIIb MSNM V6235 Pedal ungual
Crocodyliformes Crocodyliformes of the Isalo III Formation Genus Species Location Stratigraphic position Material Notes Images Andrianavoay A. baroni IIIb A machimosaurine thelattosuchian RazanandrongobeDal Sasso et al., 2017 R. sakalavae IIIb A notosuchian
See also List of dinosaur-bearing rock formations List of fossiliferous stratigraphic units in Madagascar Geology of Madagascar
References
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