''Niebla antiqua'' is an extinct species 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 foun ...

theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...

dinosaurs from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent 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 ''cre ...

(

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. Campa ...

–

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 ...

) of Río Negro province, Argentina. ''Niebla antiqua'' is the only species in the genus ''Niebla'', known from a partial, non-articulated skeleton. 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 ...

, 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 forma ...

, represents an adult individual about nine years old in minimum age.

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 and space forces, marines or naval infantry. In some usages, the term "general officer" refers to a rank above colonel."general, adj. and n.". OED Online. Ma ...

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 cap ...

, Argentina. The fossil material includes a near-complete

braincase In human anatomy, the neurocranium, also known as the braincase, brainpan, brain-pan, or brainbox, 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 calv ...

, fragmentary

jaw The jaws are a pair of opposable articulated structures 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

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 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 spina ...

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 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 ...

'', 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 , "socket", reflecting the shoulder joint's ball-and-socket form. It is a shallow, pyrif ...

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

among these South American theropods.

Paleoecology

''Niebla'' is known from the

of Argentina. The pterosaur ''

Aerotitan ''Aerotitan'' is a genus of azhdarchid pterosaur that lived during the Maastrichtian age of the Late Cretaceous period in what is now Argentina. Its only remains, which consist of a partial snout, were found in the Allen Formation of the Neuqué ...

'', as well as many

s (''

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 Bonaparte, José F. Bonaparte's claw") is a monospecific genus of alvarezsauroidea, alvarezsauroid dinosaur from Argentina that lived during the Late Cretaceous (Campanian-Maastrichtian) in what is now the uppe ...

'', ''

Austroraptor ''Austroraptor'' ( ) is a genus of dromaeosaurid theropod dinosaur that lived during the Campanian and Maastrichtian ages of the Late Cretaceous period in what is now Argentina. ''Austroraptor'' was a large, moderately-built, ground-dwelling, ...

''),

sauropod 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 b ...

s (''

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 speci ...

'', ''

Aeolosaurus ''Aeolosaurus'' (; "Aeolus' lizard") is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Period (geology), Period of what is now South America. Like most sauropods, it would have been a quadrupedal herbivore with a long neck an ...

'', '' Menucocelsior'', ''

Panamericansaurus ''Panamericansaurus'' (meaning " Pan American Energy lizard") is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Period of Argentina. The holotype is very similar to known fossil material of ''Aeolosaurus'', which ''Panamerica ...

'', ''

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 naming ...

'', ''

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 ...

''), the

ankylosaur Ankylosauria is a group of herbivorous dinosaurs of the clade Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short, powerful l ...

Patagopelta ''Patagopelta'' (meaning "Patagonian shield") is an extinct genus of ankylosaurian dinosaur from the Late Cretaceous (upper Campanian–lower Maastrichtian) Allen Formation of Argentina. The genus contains a Monotypic taxon, single species, ''P. ...

'', and

ornithopod Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (). They represent one of the most successful groups of herbivorous dinosaurs during the Cretaceous. The most primitive members of the group were bipedal and relatively sm ...

s ('' Lapampasaurus'', ''

Kelumapusaura ''Kelumapusaura'' (meaning "red earth lizard") is a genus of saurolophine hadrosaur from the Late Cretaceous Allen Formation in what is now Patagonia in Argentina. The type and only species is ''K. machi'', known from a bonebed of various individ ...

'', '' Willinakaqe'', and ''

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.

References

{{Taxonbar, from=Q100376723 Abelisauridae Dinosaur species Maastrichtian dinosaurs Allen Formation Taxa named by Fernando Novas Fossil taxa described in 2020 Dinosaurs of Argentina