The Berivotra Formation is a

Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...

sedimentary formation of the

Mahajanga Basin Mahajangā (French: Majunga) is a city and an administrative district on the northwest coast of Madagascar. The city of Mahajanga (Mahajanga I) is the capital of the Boeny Region. The district (identical to the city) had a population of 258,068 ...

Boeny Boeny is a region in northwestern Madagascar. It borders Sofia Region to the northeast, Betsiboka to the south and Melaky to the southwest. The capital of the region is Mahajanga, and the population was 931,171 in 2018. The area of Boeny is . ...

Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...

. It underlies the

Danian The Danian is the oldest age or lowest stage of the Paleocene Epoch or Series, of the Paleogene Period or System, and of the Cenozoic Era or Erathem. The beginning of the Danian (and the end of the preceding Maastrichtian) is at the Cretac ...

Betsiboka Limestone, and is underlain (and partially coeval to) the

Maevarano Formation The Maevarano Formation is a Late Cretaceous sedimentary formation (geology), rock formation found in the Mahajanga Province of northwestern Madagascar. It is most likely Maastrichtian in age, and records a seasonal, semiarid environment with rive ...

. The tan and yellow claystones and marls of the formation were deposited along a shallow marine shelf that evolved slowly from a

clastic Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus,Essentials of Geology, 3rd Ed, Stephen Marshak, p. G-3 chunks, and smaller grains of rock broken off other rocks by ...

-dominated to

carbonate A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group ...

-dominated

depositional environment In geology, depositional environment or sedimentary environment describes the combination of physical, chemical, and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will b ...

. Whilst the

fluvial A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it ru ...

sandstones Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains, cemented together by another mineral. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed o ...

of the Maevarano represent terrestrial, freshwater, and lacustrine environments, the Berivotra preserves the marine environment offshore, and many fossils of marine invertebrates (

brachiopods Brachiopods (), phylum Brachiopoda, are a phylum of animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the fron ...

bryozoans Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic animal, aquatic invertebrate animals, nearly all living in sedentary Colony (biology), colonies. Typically about long, they have a spe ...

sea urchins Sea urchins or urchins () are echinoderms in the class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal zone to deep seas of . They typically have a globular body covered by a spiny p ...

bivalves Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed by a calcified exoskeleton consis ...

, and

gastropods Gastropods (), commonly known as slugs and snails, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and from the land. Ther ...

) are known. Many

shark Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the ...

and ray teeth were collected by surface prospecting on outcrops of the Berivotra Formation, as have fossils of the frog '' Beelzebufo,'' which is also known from the Maevarano Formation.

Vertebral centra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...

bony fish Osteichthyes ( ; ), also known as osteichthyans or commonly referred to as the bony fish, is a Biodiversity, diverse clade of vertebrate animals that have endoskeletons primarily composed of bone tissue. They can be contrasted with the Chondricht ...

are also known from the Berivotra.

Fossil content

The following fossils have been reported from the formation:Berivotra
at

Fossilworks Fossilworks was a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cr ...

.org * '' Beelzebufo ampinga'' * '' Cretolamna appendiculata'', '' C. maroccana'' * '' Serratolamna serrata'' * '' Squalicorax kaupi'', '' S. pristodontus'' * '' Carcharias sp.'' * '' Parapalaeobates sp.'' * '' Pristiophorus sp.'' * '' cf. Brachyrhizodus sp.''

References

{{reflist

Fossil content

See also

References

Further reading