''Santanaraptor'' (meaning " Santana Formation thief") is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of tyrannosauroid theropod

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

that lived in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

during the

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

(late

Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...

-early

Albian The Albian is both an age (geology), age of the geologic timescale and a stage (stratigraphy), stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early Cretaceous, Early/Lower Cretaceous epoch (geology), Epoch/s ...

), about 112 million years ago.

Discovery

The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

is ''S. placidus'', first described by Kellner in 1999. The species epithet refers to , who founded the Museu de Paleontologia da Universidade Regional do Cariri.

Description

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 ...

( MN 4802-V) is a juvenile partial skeleton consisting of three caudal vertebrae with chevrons, ischia, femora, tibia, fibula, pes, and soft tissue. The

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 preserve ...

ized tissue includes a thin

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the ...

muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...

fibers, and possibly

blood vessel Blood vessels are the tubular structures of a circulatory system that transport blood throughout many Animal, animals’ bodies. Blood vessels transport blood cells, nutrients, and oxygen to most of the Tissue (biology), tissues of a Body (bi ...

s. Skin impressions under the left foot are also preserved, showing scales. It was unearthed in 1996 from the Romualdo Formation (Santana Group) in the

Ceará Ceará (, ) is one of the 26 states of Brazil, located in the Northeast Region, Brazil, northeastern part of the country, on the Atlantic Ocean, Atlantic coast. It is the List of Brazilian states by population, eighth-largest Brazilian State by ...

State, northeastern

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

. While primarily known from hindquarter elements, the individual represented by the fossil may have reached in length and in mass. The

consists of bones from the

pelvis The pelvis (: pelves or pelvises) is the lower part of an Anatomy, anatomical Trunk (anatomy), trunk, between the human abdomen, abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also c ...

, hindlimbs, and

tail The tail is the elongated section at the rear end of a bilaterian animal's body; in general, the term refers to a distinct, flexible appendage extending backwards from the midline of the torso. In vertebrate animals that evolution, evolved to los ...

. These provide little information on its overall appearance. However, it was definitely a coelurosaur, and a few of its details suggest that it might be a member of the tyrannosauroids. It is presumed to be similar to '' Dilong'' and '' Guanlong'' in that it had long arms, three fingered hands, and slim hindlimbs.

Classification

''Santanaraptor'' was originally thought to be a maniraptoran theropod when it was first discovered. However, it is now thought to be a basal coelurosaur based on several features present on the

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

. ''Santanaraptor'' was tabulated by Holtz (2004) as the first tyrannosauroid known from

Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...

, a position also found by Delcourt and Grillo (2018) who recovered ''Santanaraptor'' as a tyrannosauroid in all of their phylogenetic analyses based on three different datasets. However, this position has been criticised, as the supposed tyrannosauroid characters are widely distributed in Coelurosauria, and several aspects of the foot are more similar to noasaurids.

External links

A photograph of the fossil specimen, published by Rafael Delcourt's twitter account

References

{{Taxonbar, from=Q134305 Coelurosauria Dinosaur genera Albian dinosaurs Romualdo Formation Taxa named by Alexander Kellner Fossil taxa described in 1999 Dinosaurs of Brazil

Discovery

Description

Classification

External links

See also

References