The Ripley Formation is a

geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

found in the

U.S. The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

states of

Alabama (We dare defend our rights) , anthem = "Alabama (state song), Alabama" , image_map = Alabama in United States.svg , seat = Montgomery, Alabama, Montgomery , LargestCity = Huntsville, Alabama, Huntsville , LargestCounty = Baldwin County, Al ...

Georgia Georgia most commonly refers to: * Georgia (country), a country in the Caucasus region of Eurasia * Georgia (U.S. state), a state in the Southeast United States Georgia may also refer to: Places Historical states and entities * Related to the ...

Mississippi Mississippi () is a state in the Southeastern region of the United States, bordered to the north by Tennessee; to the east by Alabama; to the south by the Gulf of Mexico; to the southwest by Louisiana; and to the northwest by Arkansas. Miss ...

Missouri Missouri is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. Ranking List of U.S. states and territories by area, 21st in land area, it is bordered by eight states (tied for the most with Tennessee ...

, and

Tennessee Tennessee ( , ), officially the State of Tennessee, is a landlocked state in the Southeastern region of the United States. Tennessee is the 36th-largest by area and the 15th-most populous of the 50 states. It is bordered by Kentucky to th ...

. The

lithology The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain size, and composition. Lit ...

is consistent throughout the layer. It consists mainly of

glauconitic sandstone Greensand or green sand is a sand or sandstone which has a greenish color. This term is specifically applied to shallow marine sediment that contains noticeable quantities of rounded greenish grains. These grains are called ''glauconies'' and co ...

. It was formed by sediments deposited during the

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from ...

stage Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * Sta ...

of the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

. It is a unit of the

Selma Group The Selma Group is a geological formation in North America, within the U.S. states of Alabama, Mississippi, and Tennessee. The strata date from the Santonian to the Maastrichtian stages of the Late Cretaceous. The group is composed of, in ascendi ...

and consists of the Cusseta Sand Member, McNairy Sand Member and an unnamed lower member. It has not been extensively studied by vertebrate paleontologists, due to a lack of accessible exposures. However, fossils have been unearthed including

crocodile Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to inclu ...

hadrosaur Hadrosaurids (), or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod family, which includ ...

, nodosaur,

tyrannosaur Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent be ...

ornithomimid Ornithomimidae (meaning "bird-mimics") is a family of theropod dinosaurs which bore a superficial resemblance to modern ostriches. Ornithomimids were fast, omnivorous or herbivorous dinosaurs known mainly from the Late Cretaceous Period of Laura ...

, dromaeosaur, and

mosasaur Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Greek ' meaning 'lizard') comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Maastricht on th ...

remains have been recovered from the Ripley Formation.

Paleofauna

*''

Hypsibema missouriensis ''Hypsibema missouriensis'' (; originally ''Neosaurus missouriensis'', first renamed to ''Parrosaurus missouriensis'', also spelled ''Hypsibema missouriense'') is a species of plant-eating dinosaur in the genus ''Hypsibema'', and the state din ...

'' (

hadrosaurid Hadrosaurids (), or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod family, which inclu ...

) – "Caudal vertebrae, fragmentary dentary and predentary.""Table 20.1," in Weishampel, et al. (2004). Page 443. *cf. ''

Gryposaurus ''Gryposaurus'' (meaning "hooked-nosed (Ancient Greek, Greek ''grypos'') lizard"; sometimes incorrectly translated as "griffin (Latin ''gryphus'') lizard") was a genus of hadrosaur, duckbilled dinosaur that lived about 80 to 75 million years ...

'' sp. *

Nodosauridae Nodosauridae is a family of ankylosaurian dinosaurs, from the Late Jurassic to the Late Cretaceous period in what is now North America, South America, Europe, and Asia. Description Nodosaurids, like their close relatives the ankylosaurids, wer ...

sp. *

Tyrannosauroidea Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent b ...

sp. *cf. ''Albertosaurus'' sp. * Dromaeosauridae sp. *Possible

Ornithomimidae Ornithomimidae (meaning "bird-mimics") is a family of theropod dinosaurs which bore a superficial resemblance to modern ostriches. Ornithomimids were fast, omnivorous or herbivorous dinosaurs known mainly from the Late Cretaceous Period of Lauras ...

indet. *'' Eothoracosaurus mississippiensis'' * ''Thoracosaurus neocesariensis'' *'' Leidyosuchus'' sp. * ''

Adocus ''Adocus'' is an extinct genus of aquatic turtles belonging to the family Adocidae. ''Adocus'' was once considered to belong to the family Dermatemyidae. Description Species of the genus ''Adocus'' had flattened and smoothly contoured shells w ...

punctatus'' * ''

Naomichelys ''Naomichelys'' is an extinct genus of helochelydrid stem turtle known from the Cretaceous (Aptian-Campanian) of North America. It is the only member of the family known to be native to North America. Distribution ''Naomichelys'' is known nume ...

speciosa'' * '' Trionyx'' sp. * '' Habrosaurus'' sp. * '' Amiidae'' sp. * ''

Lepisosteus ''Lepisosteus'' is a genus of gars in the family Lepisosteidae. Distribution While in the present day, ''Lepisosteus'' is only known across North America, fossil remains show it was much more widespread in the past, with specimens known from t ...

'' sp. * '' Platacodon nanus''

References

{{Reflist Cretaceous Mississippi Cretaceous Alabama Cretaceous Georgia (U.S. state) Cretaceous Missouri Cretaceous geology of Tennessee Sandstone in the United Kingdom Chalk Maastrichtian Stage of North America

Paleofauna

See also

References