The Adamantina Formation is a geological formation in the Bauru Basin of western São Paulo state in southeastern Brazil.

Its strata date back to the Late Cretaceous epoch of the Cretaceous Period, during the Mesozoic Era. The formation is part of the Bauru Group in the northeastern Paraná Basin.

Geology Dinosaur remains are among the fossils that have been recovered from the Adamantina Formation. According to some studies, the Adamantina Formation dates from the Turonian to the Santonian stage (90-83.5 million years ago) of the late Cretaceous, other studies have found a much younger age - Campanian to Maastrichtian (83.5-66 million years ago) of the late Cretaceous.

More recent studies lean into the latter category and an unpublished article abstract revealed at the Society of Vertebrate Paleontology in 2017 also argues that the Allen Formation, Loncoche, and Los Alamitos Formation are all contemporaries and are no later than 72.1Ma in age. A zircon was found dating to 87.8 Ma, so this represents a maximum age.

Geological setting During the Early Jurassic, the supercontinent Pangea started to drift apart due to the breakup of Gondwana and Laurasia. The breakup of Gondwana caused the formation of the large Parana Basin. This basin has a size of ~1,100,000km2 and can be found not only in Brazil but also in Paraguay, Uruguay, and Argentina. The separation of the supercontinent and the breakup of Brazil and Africa was accompanied by volcanism that caused large eruptions of flood basalts. These volcanic rocks formed the Serra Geral Formation which underlies the deposits of the Bauru Group.

The Bauru Basin is a trough that, as Miall (1990) argues, evolved due to "thermo-mechanical subsidence" during the Late Cretaceous, probably due to the breakup of Africa and India. The sediments reach a thickness of up to ~300 m and consist mainly of siliciclastic sediments. The Bauru Group can be subdivided into five different formations from bottom to top: Caiua, Santo Anastacio, Adamantina, and Uberaba. Not all formations are equally well represented in the different states and differences occur according their sedimentary composition and therefore also in their naming.

Vertebrate paleofauna

Crocodylomorphs

Crocodylomorphs of the Adamantina Formation Genus Species Location Stratigraphic position Material Notes Images Adamantinasuchus A. navae Six specimens and several isolated bone remains. A zhiphosuchian notosuhian AphaurosuchusA. kaiju Skull elements and teeth. A baurusuchine baurusuchid Aplestosuchus B. sordidus A baurusuchine baurusuchid Armadillosuchus A. arrudai A sphagesaurid notosuchian Barreirosuchus B. franciscoi A itasuchid notosuchia Baurusuchus B. albertoi A baurusuchine baurusuchid B. pachechoi B. salgadoensis Brasileosaurus B. pachecoi A notosuchid notosuchian Campinasuchus C. dinizi A pissarrachampsine baurusuchid Caipirasuchus C. catanduvensisA sphagesaurid notosuchian C. paulistanus Caryonosuchus C. pricei A sphagesaurid notosuchian Epoidesuchus E. tavaresae. A itasuchid notosuchian Mariliasuchus M. amarali Very common. Several specimens - juvenile and adults – with skulls articulated to skeletons, and many isolated materials. Eggs clutches, eggshells, and coprolites were found also. A notosuchid notosuchian M. robustus A notosuchid notosuchian Montealtosuchus M. arrudacamposi A peirosaurid notosuchian Morrinhosuchus M. luziae A sphagesaurid notosuchian Roxochampsa R. paulistanus Several teeth, splenials, and dentaries. A itasuchid notosuchian Sphagesaurus S. huenei A sphagesaurid notosuchian S. montealtensis A sphagesaurid notosuchian Stratiotosuchus S. maxhechti A baurusuchine baurusuchid Sphagesauria Indet. Indeterminate A tooth One of the largest sphagesaurian specimens reported to date from the formation and the first notosuchian record from mid-west Brazil Crocodylomorph eggs have also been found in the Adamantina formation. With the largest known mesozoic crocodylian egg clutch (47 eggs) being founin the formation.

Dinosaurs

Sauropods Sauropods of the Adamantina Formation Genus Species Location Stratigraphic position Material Notes ImagesAdamantisaurusA. mezzalirai A lithostrotian titanosaurian Arrudatitan A. maximus A single partially articulated skeleton. An aeolosaurin titanosaurian Antarctosaurus A. brasiliensis Postcranial remains."Table 13.1," in Weishampel, et al. (2004). Page 270. A colossosaurian titanosaurian Brasilotitan B. nemophagus Raposo Tavares. A partial skeleton and dentition. A lithostrotian titanosaurian Gondwanatitan G. faustoi Partial postcranial skeleton."Table 13.1," in Weishampel, et al. (2004). Page 269. An aeolosaurin lithostrotian Maxakalisaurus M. topai A fragmentary right maxilla with teeth, twelve cervical vertebrae and some cervical ribs, seven dorsal vertebrae and some dorsal ribs, a neural spine and centrum from the sacrum, six caudal vertebrae, some haemal arches, pieces of the scapulae, both sternal plates, part of the left ischium, both humeri, two metacarpals, part of the fibula, an osteoderm, and some unidentified pieces An aeolosaurin lithostrotian

Theropods Theropods of the Adamantina Formation Genus Species Location Stratigraphic position Material Notes Images Abelisauridae Indet.Indeterminate Fragment of right premaxilla and a toothAbelisauridae Indet.InderteminateA fragmentary left ilium with most of the preacetabular and supracetabular regions preserved. An distal portion of a right femur.Enantiornithes indet.IndeterminateNear complete jaws and skulls Navaornis N. hesitate Complete skull and well-preserved skeleton An enantiornithean bird Noasauridae Indet. IndeterminateCervical vertebra, almost complete right femur.An isolated cervical vertebra (DGM 929-R), (CPPLIP 1490) almost complete isolated right femur Unenlagiinae indet. Indeterminate A single dorsal vertebra

Squamates Squamate fossils include those of unnamed, indeterminate snakes.

Squamates of the Adamantina Formation Genus Species Location Stratigraphic position Material Notes Images Boipeba B. tayasuensis A single precloacal vertebra A large, primitive blind snake Brasiliguana B. prudentis A maxilla An iguanian lizard Squamata indet. Indeterminate Estrada Velha, ponto 1 MPM 151 R consists of 10 articulated dorsal vertebrae A non-snake squamate Tametara T. mirim An early snake

Amphibians Amphibians of the Adamantina Formation Genus Species Location Stratigraphic positionMaterial Notes Images Baurubatrachus B. santosdoroi Near Catanduva city, São Paulo. Remains of two individuals A frog Calyptocephalellidae indet. Indeterminate Mariliabatrachus M. navai A frog.

Turtles Turtle of the Adamantina Formation Genus Species Location Stratigraphic positionMaterial Notes Images Bauruemys B. brasilensis A podocnemidoid side-necked turtle Roxochelys R. wanderleyi A podocnemididoid side-necked turtle Yuraramirim Y. montealtensis A peiropemydid side-necked turtle

Fish Fishes of the Adamantina Formation Genus Species Location Stratigraphic position Material Notes Images Amiidae indet. Indeterminate Atractosteus A. sp. A gar Britosteus B. amarildoi A gar Dipnoi indet. Indeterminate Lepisosteidae indet. Indeterminate, previously described as "Lepisosteus cominatoi" A gar

Mammals Mammals of the Adamantina Formation Genus Species Location Stratigraphic position Material Notes Images Eutheria indet. Indeterminate Brasilestes B. stardusti A tribosphenic mammal Gondwanatheria indet. Indeterminate Meridiolestida indet. Indeterminate

See also

List of dinosaur-bearing rock formations

Asencio Formation

References