''Guemesia'' (named after

Martín Miguel de Güemes Martín Miguel de Güemes (8 February 1785 – 17 June 1821) was a military leader and popular caudillo who defended northwestern Argentina from the Spain, Spanish royalist army during the Argentine War of Independence. Biography Güemes was bor ...

, whose death bicentenary was in 2021) 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 foun ...

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'', ...

Los Blanquitos Formation of Salta 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 type and only species is ''Guemesia ochoai'', known from a nearly complete braincase. It is one of the smallest abelisaurids currently known.

Discovery

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 sever ...

of ''Guemesia'', IBIGEO-P 103, is a small, nearly complete braincase. It was found in the Los Blanquitos Formation, in the Amblayo Valley of Salta Province, Argentina. The specimen was described in 2022 by Agnolín ''et al''. as belonging to a new genus and species of abelisaurid dinosaur, and the first dinosaur of its kind known from the area.

Classification

Agnolín ''et al.'' place ''Guemesia'' as a derived abelisaurid within the clade Brachyrostra.

Paleoecology

''Guemesia'' is known from the Los Blanquitos Formation. The controversial

tetanuran Tetanurae (/ˌtɛtəˈnjuːriː/ or "stiff tails") is a clade that includes most theropod dinosaurs, including megalosauroids, allosauroids, tyrannosauroids, ornithomimosaurs, compsognathids and maniraptorans (including birds). Tetanurans ar ...

theropod ''

Unquillosaurus ''Unquillosaurus'' (meaning "Unquillo river lizard") is a genus of possible maniraptoran or carnosaurian theropod dinosaur from the Late Cretaceous Los Blanquitos Formation of Salta Province, Argentina. The genus contains a single species, ''U. ...

'' is also known from this formation, as well as fossils of what may belong to a species of ''

Titanosaurus ''Titanosaurus'' (; ) is a dubious genus of sauropod dinosaurs, first described by Richard Lydekker in 1877.R. Lydekker. (1877). Notices of new and other Vertebrata from Indian Tertiary and Secondary rocks. ''Records of the Geological Survey of I ...

''.Arroyo El Morterito
at Fossilworks.org

References

{{Theropoda, B. Late Cretaceous Fossils of Argentina Late Cretaceous dinosaurs of South America Campanian life Brachyrostrans Fossil taxa described in 2022 Cretaceous Argentina Salta Basin