''Koleken'' (meaning "coming from clay and water") is a genus of carnotaurin

abelisaurid Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are foun ...

from the

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 ...

La Colonia Formation The La Colonia Formation is a geological Formation (geology), formation in Argentina whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.Weishampel et al., 2004, pp.600- ...

in the

Chubut Province Chubut ( from Tehuelche language, Tehuelche 'transparent'; ) is a provinces of Argentina, province in southern Argentina, situated between the 42nd parallel south (the border with Río Negro Province), the 46th parallel south (bordering Santa ...

of Argentina. The type and only species is ''K. inakayali'', known from one immature specimen about long and six years old in minimum age.

Discovery and naming

''Koleken'' is known from only the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

MPEF-PV 10826 which was initially found and reported in 2015, but was not described as ''K. inakayali'' until 2024. The holotype, consists of "closely associated (but disarticulated) remains of the skull and atlas, as well as the articulated postcranial skeleton composed of the posterior most eight dorsal vertebrae, a complete sacrum, eight caudal vertebrae, an almost complete pelvis and hind limbs". It differs from the larger ''Carnotaurus'' in anatomical characteristics found in the skull, vertebrae, and leg bones. The specimen likewise is believed to represent a sub-adult based on a lack of fusion in some of the bones. The generic name, ''Koleken'', is a name in

Teushen The Teushen or Tehues were an Indigenous hunter-gatherer people of Patagonia in Argentina. They were considered "foot nomads", whose culture relied on hunting and gathering.Adelaar and Muysken 550 Their territory was between the Tehuelche people t ...

spoken by the native population of central

Patagonia Patagonia () is a geographical region that includes parts of Argentina and Chile at the southern end of South America. The region includes the southern section of the Andes mountain chain with lakes, fjords, temperate rainforests, and glaciers ...

that means "coming from clay and water", given the specimen was found in a sedimentary section dominated by

claystone Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone and shale. Most of the particles of which the stone is composed are less than and are too small to ...

representing an

estuarine 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 environm ...

environment. The specific name, ''inakayali'', honours Inakayal, one of the last chiefs of

Tehuelches The Tehuelche people, also called the Aónikenk, are an Indigenous people from eastern Patagonia in South America. In the 18th and 19th centuries the Tehuelche were influenced by Mapuche people, and many adopted a horseriding lifestyle. Once a ...

, native people from central Patagonia.

Classification

''Koleken'' is placed in the

Carnotaurini Brachyrostra (meaning "short snouts") is a clade within the theropod dinosaur family Abelisauridae. It includes the famous genera ''Carnotaurus'', '' Aucasaurus'', potentially '' Abelisaurus'' as well as their close relatives from the Cretaceous ...

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide use of the term in English is in the discipline of anthropology. The definition is contested, in part due to conflict ...

Abelisauridae Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are fou ...

, in a

polytomy An internal node of a phylogenetic tree is described as a polytomy or multifurcation if (i) it is in a rooted tree and is linked to three or more child subtrees or (ii) it is in an unrooted tree and is attached to four or more branches. A tree ...

with the other carnotaurins in a phylogenetic analysis:

Paleoenvironment

''Koleken'' was found in outcrops of the

, which dates to the

(Cretaceous)–

Paleocene The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...

(Paleogene) boundary. This formation is best known for fossils of the

theropod ''

Carnotaurus ''Carnotaurus'' (; ) is a genus of Theropoda, theropod dinosaur that lived in South America during the Late Cretaceous period, probably sometime between 72 and 69 million years ago. The only species is ''Carnotaurus sastrei''. Known from a si ...

'' and the saltasauroid

titanosaur Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still thr ...

Titanomachya ''Titanomachya'' (named after the Titanomachy of Greek mythology) is an extinct genus of titanosaurian sauropod dinosaur from the Late Cretaceous La Colonia Formation of Argentina. The genus contains a Monotypic taxon, single species, ''T. gimenez ...

'', as well as fossils of other reptiles including the turtle '' Patagoniaemys'', the snake ''

Alamitophis ''Alamitophis'' is a genus of fossil snakes in the extinct family of Madtsoiidae. Its length is estimated at and it probably fed on frogs, lizards, and small mammals. It is found in Australia (Tingamarra Fauna, after which ''A. tingamarra'' is n ...

'' and the

plesiosaurs The Plesiosauria or plesiosaurs are an Order (biology), order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared in the latest Triassic Period (geology), Period, possibly in the Rhaetian st ...

Kawanectes ''Kawanectes'' (meaning "Kawas swimmer") is a genus of elasmosauridae, elasmosaurid plesiosaur, a type of long-necked marine reptile, that lived in the marginal marine (probably estuary, estuarine) environment of Late Cretaceous Patagonia. It co ...

'', ''

Chubutinectes ''Chubutinectes'' (meaning "Chubut Province, Chubut swimmer") is an extinct genus of elasmosaurid plesiosaur from the Late Cretaceous La Colonia Formation of Argentina. The genus contains a Monotypic taxon, single species, ''C. carmeloi'', known ...

'' and ''

Sulcusuchus ''Sulcusuchus'' is a genus of polycotylid plesiosaur from the Late Campanian to Early Maastrichtian of Argentina. Description The type species ''Sulcusuchus erraini'' was named in 1990 by Zulma Brandoni de Gasparini and Luis Spalletti. It w ...

''. Mammals discovered from the formation include ''

Reigitherium ''Reigitherium'' was a mammal that lived during the Late Cretaceous, in the (Late Campanian-Maastrichtian). Its fossils have been found in the Los Alamitos and the La Colonia Formations of Argentina. Description The original specimen of ''Rei ...

'', ''

Coloniatherium ''Coloniatherium'' is a meridiolestid mammal from the Late Cretaceous of Argentina. The single species, ''Coloniatherium cilinskii'', was a large member of the family Mesungulatidae. Taxonomy ''Coloniatherium'' was named in 2009 by Guillermo R ...

'', ''

Argentodites ''Argentodites'' is a possible multituberculate mammal from the Cretaceous of Argentina. The single species, ''Argentodites coloniensis'', is known from a single blade-like fourth lower premolar (p4) from the La Colonia Formation, which is mostl ...

'' and ''

Ferugliotherium ''Ferugliotherium'' is a genus of fossil mammals in the family Ferugliotheriidae from the Campanian and/or Maastrichtian period (Late Cretaceous; around 70 million years ago) of Argentina. It contains a single species, ''Ferugliotherium windhaus ...

''. Remains of an

enantiornithine The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct avialans ("birds" in the broad sense), the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth and c ...

and, possibly, of a neornithine bird have been discovered.

References

{{Taxonbar, from=Q126012874 Abelisauridae Dinosaur genera Maastrichtian dinosaurs Taxa named by Fernando Novas Fossil taxa described in 2024 Dinosaurs of Argentina