The Urumaco Formation is a

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondary ...

Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in ...

that includes deposits from the

Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene Epoch made up of two stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million years ago) to 5.333 Ma. The ...

. It is the site of several "giant forms": the

turtles Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked t ...

crocodiles Crocodiles (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 include all extant m ...

, sloths and

rodents Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...

of Urumaco are among the largest of their groups.

Location

The Urumaco formation is located in the Urumaco region in the Caribbean coastal

Falcón ) , anthem = , image_map = Falcon in Venezuela.svg , map_alt = , map_caption = Location within Venezuela , pushpin_map = , pushpin_map_alt = , pushpin_mapsiz ...

state. The deposits date from 10 to 5.3 million years ago and the Urumaco formation was deposited in an area with large

river A river is a natural flowing watercourse, usually freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the ...

s, swamps,

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environme ...

lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into '' coastal lagoons'' (or ''barrier lagoons' ...

s and shallow coastal seas. These conditions in the Late Miocene contrast strongly with the current dry environment in the area today.

Fauna

Cartilaginous fish

There are 21 known species of

cartilaginous fishes Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissue ...

from the Urumaco Formation, belonging to the orders

Lamniformes The Lamniformes (, from Greek ''lamna'' "fish of prey") are an order of sharks commonly known as mackerel sharks (which may also refer specifically to the family Lamnidae). It includes some of the most familiar species of sharks, such as the grea ...

, Carcharhiniformes,

Myliobatiformes Myliobatiformes () is one of the four orders of batoids, cartilaginous fishes related to sharks. They were formerly included in the order Rajiformes, but more recent phylogenetic studies have shown the myliobatiforms to be a monophyletic grou ...

and

Rajiformes Rajiformes is one of the four orders in the superorder Batoidea, flattened cartilaginous fishes related to sharks. Rajiforms are distinguished by the presence of greatly enlarged pectoral fins, which reach as far forward as the sides of the head ...

. '' Carcharhinus caquetius'' is an

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found els ...

species of predator shark from Urumaco. A large number of well-preserved

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s of the

sawfish Sawfish, also known as carpenter sharks, are a family of rays characterized by a long, narrow, flattened rostrum, or nose extension, lined with sharp transverse teeth, arranged in a way that resembles a saw. They are among the largest fish ...

'' Pristis rostra'' have been found in the deposits. The

megalodon Megalodon (''Otodus megalodon''), meaning "big tooth", is an extinct species of mackerel shark that lived approximately 23 to 3.6 million years ago (Mya), from the Early Miocene to the Pliocene epochs. It was formerly thought to be a me ...

is also known from the Urumaco Formation. The coastal seas of Urumaco were further inhabited by species that still live in the

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

today, such as the

spotted eagle ray The spotted eagle ray (''Aetobatus narinari'') is a cartilaginous fish of the eagle ray family, Myliobatidae. As traditionally recognized, it is found globally in tropical regions, including the Atlantic, Pacific and Indian Oceans. Recent au ...

, smooth hammerhead shark,

tiger shark The tiger shark (''Galeocerdo cuvier'') is a species of requiem shark and the last extant member of the family Galeocerdonidae. It is a large macropredator, capable of attaining a length over . Populations are found in many tropical and temper ...

and

bull shark The bull shark (''Carcharhinus leucas''), also known as the Zambezi shark (informally zambi) in Africa and Lake Nicaragua shark in Nicaragua, is a species of requiem shark commonly found worldwide in warm, shallow waters along coasts and in ri ...

Bonefish

The

bony fishes Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartila ...

from the Urumaco Formation include groupers, piranha-like fish such as pacas,

cuttlefish Cuttlefish or cuttles are marine molluscs of the order Sepiida. They belong to the class Cephalopoda which also includes squid, octopuses, and nautiluses. Cuttlefish have a unique internal shell, the cuttlebone, which is used for control ...

thorny catfish The Doradidae are a family of catfishes also known as thorny catfishes, raphael catfishes or talking catfishes. These fish are native to South America, primarily the Amazon basin and the Guianas. Doradids are omnivorous. Taxonomy As of 2007, 3 ...

and red-tailed catfish.

Reptiles

The Urumaco Formation has a great diversity of crocodilians with twelve known species. Seven species of caimans have been described: ''

Caiman brevirostris ''Caiman brevirostris'' is an extinct species of caiman that lived during the Late Miocene, around 11.6 million years ago, to the end of the Miocene 5.3 million years ago in Acre and Amazonas, Brazil as well as Urumaco, Venezuela. Several specim ...

'', '' C. latirostris'', '' Globidentosuchus brachyrostris'', ''

Melanosuchus fisheri ''Melanosuchus'' is a genus of alligatorid caiman. The black caiman of South America is the sole extant (living) species, and is the largest living member of the subfamily caimaninae, and the entire alligator family. Taxonomy Extant species Ther ...

'', '' Mourasuchus arendsi'', '' M. nativus'' and '' Purussaurus mirandai'', '' Gryposuchus croizati'', '' G. jessei'', '' Hesperogavialis cruxenti'' and '' Ikanogavialis gameroi'' are the gavials of Urumaco, a group that is no longer found in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the souther ...

today. The kinship of '' Charactosuchus mendesi'' with the other crocodilians is considered unclear. Multiple species of crocodilians were able to live together because they focused on specific niches, making it limited competition between species. For example, ''Mourasuchus arendsi'' had a duck-like beak with which it caught

crustaceans Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean gr ...

, the 10-foot-long, fish-eating ''Gryposuchus croizati'' lived particularly in estuaries, and the 11.5-foot-long ''Purussaurus mirandai'' hunted a wide range of prey animals. ''

Stupendemys geographicus ''Stupendemys'' is an extinct genus of freshwater side-necked turtle, belonging to the family Podocnemididae. It is the largest freshwater turtle known to have existed, with a carapace over 2 meters long. Its fossils have been found in nor ...

'' is the best-known turtle species from the Urumaco formation. This animal from the American necked turtles family was one of the largest turtles ever with a shell 3.3 meters long. Other turtles from Urumaco include several species of ''

Bairdemys ''Bairdemys'' is an extinct genus of side-necked turtles in the family Podocnemididae. The genus existed from the Late Oligocene to Late Miocene and its fossils have been found in South Carolina, Puerto Rico, Panama and Venezuela. The genus was ...

, ''the ''

mata mata Matamata () is a town in Waikato, New Zealand. It is located near the base of the Kaimai Ranges, and is a thriving farming area known for Thoroughbred horse breeding and training pursuits. It is part of the Matamata-Piako District, which takes ...

Chelus lewisi'' and

softshell turtles The Trionychidae are a taxonomic family of a number of turtle genera, commonly known as softshell turtles. The family was erected by Leopold Fitzinger in 1826. Softshells include some of the world's largest freshwater turtles, though many can ad ...

. In addition to the multiple crocodilians and turtles, vertebra of a boa have also been found in the Urumaco Formation.

Mammals

'' Phoberomys pattersoni'' is one of the largest known rodents ever. This three-meter-long relative of today's pacarana had a lifestyle similar to that of the

capybara The capybaraAlso called capivara (in Brazil), capiguara (in Bolivia), chigüire, chigüiro, or fercho (in Colombia and Venezuela), carpincho (in Argentina, Paraguay and Uruguay) and ronsoco (in Peru). or greater capybara (''Hydrochoerus hydro ...

. Several species of

xenarthra Xenarthra (; from Ancient Greek ξένος, xénos, "foreign, alien" + ἄρθρον, árthron, "joint") is a major clade of placental mammals native to the Americas. There are 31 living species: the anteaters, tree sloths, and armadillos. Ex ...

ns are known from the Urumaco Formation. '' Urumaquia robusta'' was a

ground sloth Ground sloths are a diverse group of extinct sloths in the mammalian superorder Xenarthra. The term is used to refer to all extinct sloths because of the large size of the earliest forms discovered, compared to existing tree sloths. The Cari ...

from the

Megatheriidae Megatheriidae is a family of extinct ground sloths that lived from approximately 23 mya—11,000 years ago. Megatheriids appeared during the Late Oligocene (Deseadan in the SALMA classification), some 29 million years ago, in South America. ...

weighing four tons. Others ground sloths from Urumaco are '' Bolivartherium urumaquensis'', '' Urumacotherium garciai'', '' Eionaletherium tanycnemius'', and '' Pseudoprepotherium venezuelanum'' belonging to the

Mylodontidae Mylodontidae is a family of extinct South American and North American ground sloths within the suborder Folivora of order Pilosa, living from around 23 million years ago (Mya) to 11,000 years ago. This family is most closely related to another fa ...

.''

Urumacocnus ''Urumacocnus'' is an extinct genus of megalonychid sloth that lived during the Miocene in Venezuela. The genus contains one known species, ''Urumacocnus urbanii''. Fossils have been found in the Urumaco Formation of Venezuela. Etymology The g ...

urbani'' and ''

Pattersonocnus ''Pattersonocnus'' is an extinct genus of megalonychid sloth that lived during the Miocene in Venezuela 11.6 million years ago. The genus contains one known species, ''Pattersonocnus diazgameroi''. Fossils have been found in the Urumaco Forma ...

diazgameroi'' are ground sloths from the Megalonychidae. '' Boreostemma pliocena'' is a

glyptodont Glyptodonts are an extinct subfamily of large, heavily armoured armadillos. They arose in South America around 48 million years ago and spread to southern North America after the continents became connected several million years ago. The best-k ...

. '' Bounodus enigmaticus'' ( Proterotheriidae, Litopterna) and '' Gyrinodon'' ( Toxodontidae,

Notoungulata Notoungulata is an extinct order of mammalian ungulates that inhabited South America from the early Paleocene to the Holocene, living from approximately 61 million to 11,000 years ago. Notoungulates were morphologically diverse, with forms resem ...

) are the South American ungulates of the Urumaco formation. In the waters of Urumaco lived the freshwater dolphins '' Ischyrorhynchus vanbenedeni'' and '' Saurodelphis'' and the dugongs '' Nanosiren sanchezi'' and possibly '' Metaxytherium''. Fossil Sirenia of the West Atlantic and Caribbean region. VIII. ''Nanosiren garciae'', gen. et sp. nov. and ''Nanosiren sanchezi'', sp. nov. DP Domning & OA Aguilera. Journal of Vertebrate Paleontology (2008).

References

{{Reflist Geologic formations of Venezuela Neogene Venezuela Miocene Series of South America Laventan Mayoan Chasicoan Lagerstätten Fossiliferous stratigraphic units of South America Paleontology in Venezuela