''Niebla'' is a genus of

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 found ...

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

from 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 ...

Period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

(

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian s ...

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 ...

) of Río Negro province,

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

. The genus contains a single species, ''Niebla antiqua'', and is known from a partial, non-articulated skeleton. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, found in the

Allen Formation The Allen Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous (middle Campanian to early Maastrichtian.Salgado et al., 2007 Dinosaur remains are among the fossils that have been recovered from the formati ...

, represents an adult individual.

Discovery and naming

The holotype, MPCN-PV-796, was found near Matadero Hill, south of

General Roca A general officer is an officer of high rank in the armies, and in some nations' air forces, space forces, and marines or naval infantry. In some usages the term "general officer" refers to a rank above colonel."general, adj. and n.". OED O ...

Río Negro province Río Negro (, ''Black River'') is a province of Argentina, located in northern Patagonia. Neighboring provinces are from the south clockwise Chubut, Neuquén, Mendoza, La Pampa and Buenos Aires. To the east lies the Atlantic Ocean. Its capit ...

. The fossil material includes a near-complete

braincase In human anatomy, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria or skul ...

, fragmentary

jaw The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth and serv ...

and

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

, relatively complete

scapulocoracoid The scapulocoracoid is the unit of the pectoral girdle that contains the coracoid and scapula. The coracoid itself is a beak-shaped bone that is commonly found in most vertebrates with a few exceptions. The scapula is commonly known as the ''shoulde ...

, dorsal ribs and incomplete

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

e. The genus name ''Niebla'' comes from the Spanish word for "mist", referring to the foggy days during the excavation of the fossil. The specific name, ''antiqua'', is derived from a Latin word meaning "old."

Description

''Niebla'' represents one of the most derived abelisaurids. Despite its relatively small size, especially when compared to related dinosaurs like ''

Carnotaurus ''Carnotaurus'' (; ) is a genus of theropod dinosaur that lived in South America during the Late Cretaceous period, probably sometime between 71 and 69 million years ago. The only species is ''Carnotaurus sastrei''. Known from a single well-p ...

'', the holotype represents an adult. Based on the remains, ''Niebla'' would have been roughly long. The

is notably similar to that of ''

'' in having a posterodorsally oriented

glenoid The glenoid fossa of the scapula or the glenoid cavity is a bone part of the shoulder. The word ''glenoid'' is pronounced or (both are common) and is from el, gléne, "socket", reflecting the shoulder joint's ball-and-socket form. It is a sha ...

, a dorsoventrally expanded and wide coraco-scapular plate, and a very narrow and straight

scapular blade The scapular (from Latin ''scapulae'', "shoulders") is a Western Christian garment suspended from the shoulders. There are two types of scapulars, the monastic and devotional scapular, although both forms may simply be referred to as "scapular ...

. These features are very different from those of other abelisaurids, which may indicate a unique conformation of the

pectoral girdle The shoulder girdle or pectoral girdle is the set of bones in the appendicular skeleton which connects to the arm on each side. In humans it consists of the clavicle and scapula; in those species with three bones in the shoulder, it consists of t ...

among these

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 southe ...

Paleoecology

''Niebla'' is known from the Allen Formation of Argentina. The pterosaur ''

Aerotitan ''Aerotitan'' is a genus of large azhdarchid pterosaur known from the Late Cretaceous period (Maastrichtian stage) of what is now the Allen Formation of the Neuquén Basin in northern Patagonia, Argentina. Discovery and naming The type species ...

'', as well as

theropods Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

(''

Quilmesaurus ''Quilmesaurus'' is a genus of carnivorous abelisaurid theropod dinosaur from the Patagonian Upper Cretaceous (Campanian stage) of Argentina. It was a member of Abelisauridae, closely related to genera such as ''Carnotaurus''. The only known rema ...

'', ''

Bonapartenykus ''Bonapartenykus'' (meaning "José F. Bonaparte's claw") is a monospecific genus of alvarezsauroid dinosaur from Argentina that lived during the Late Cretaceous (Campanian-Maastrichtian) in what is now the upper Allen Formation of the Río Negro ...

'', ''

Austroraptor ''Austroraptor'' ( ) is a genus of large dromaeosaurid dinosaur that lived during the Late Cretaceous Period in what is now Argentina. ''Austroraptor'' was a large-sized, moderately-built, ground-dwelling, bipedal carnivore, estimated at in len ...

''),

sauropods Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their bo ...

(''

Bonatitan ''Bonatitan'' is a genus of titanosaurian dinosaur from the Late Cretaceous Allen Formation of Argentina. It was named in 2004. Description The type species is ''Bonatitan reigi'', first described by Martinelli and Forasiepi in 2004. The s ...

'', ''

Pellegrinisaurus ''Pellegrinisaurus'' (meaning ''Lizard from Pelligrini'') is a genus of titanosaurian sauropod dinosaur that lived in South America during the Late Cretaceous period. The holotype was found in the Allen Formation, Argentina. Discovery and namin ...

Rocasaurus ''Rocasaurus'' (meaning "General Roca lizard") is a genus of titanosaurian sauropod that lived in South America. ''Rocasaurus'' was discovered in Argentina in 2000, within the Allen Formation which is dated to be middle Campanian to early Maastr ...

)'' and

ornithopods Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (), that started out as small, bipedal cursorial, running grazers and grew in size and numbers until they became one of the most successful groups of herbivores in the Creta ...

('' Lapampasaurus,

Bonapartesaurus ''Bonapartesaurus'' (meaning "Bonaparte's lizard", named after José Bonaparte) is an extinct genus of herbivorous ornithopod dinosaur belonging to Hadrosauridae, which lived in the area of modern Argentina during the Campanian and Maastrichtian ...

)'', are also known from the formation. Allen Formation Fauna

References

{{Taxonbar, from=Q100376723 Abelisaurids Maastrichtian life Late Cretaceous dinosaurs of South America Cretaceous Argentina Fossils of Argentina Allen Formation Fossil taxa described in 2020