''Lucianovenator'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

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 ...

coelophysid Coelophysoidea is an extinct clade of theropod dinosaurs common during the Late Triassic and Early Jurassic periods. They were widespread geographically, probably living on all continents. Coelophysoids were all slender, carnivore, carnivorous fo ...

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 ...

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 ...

which lived in

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

during the

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

. The genus name ''Lucianovenator'' translates to "Luciano's hunter", in reference to Don Luciano Leyes, who first reported the remains. The species name ''bonoi'' refers to Tulio del Bono, a local scientific authority who collaborated on the describers' research. It is one of the few

neotheropods 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 Sauropodomor ...

known from South America.

Discovery

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 ...

(PVSJ 906) of ''Lucianovenator bonoi'' was found in the "Quebrada del puma" locality of the

Quebrada del Barro Formation The Quebrada del Barro Formation is a geological formation of the Marayes-El Carrizal Basin in San Juan Province, Argentina. This formation is the most fossiliferous portion of the Triassic Marayes Group, and is also the youngest unit of the gr ...

in Argentina, which is estimated to be from the late

Norian The Norian is a division of the Triassic geological period, Period. It has the rank of an age (geology), age (geochronology) or stage (stratigraphy), stage (chronostratigraphy). It lasted from ~227.3 to Mya (unit), million years ago. It was prec ...

Rhaetian The Rhaetian is the latest age (geology), age of the Triassic period (geology), Period (in geochronology) or the uppermost stage (stratigraphy), stage of the Triassic system (stratigraphy), System (in chronostratigraphy). It was preceded by the N ...

in age, approximately 210 to 202 million years ago. PVSJ 906 represents an articulated vertebral sequence from the third cervical to fourth dorsal

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 ...

, as well as a

sacrum The sacrum (: sacra or sacrums), in human anatomy, is a triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30. The sacrum situates at the upper, back part of the pelvic cavity, ...

and a partial

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 ...

. In addition, three more specimens were referred to ''Lucianovenator''. These include PVSJ 899 (a sacrum and partial pelvis), PVSJ 1013 (a sacrum), and PVSJ 1084 (a sacrum and partial pelvis). PVSJ 1004, the proximal end of a right

tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

, may also belong to the species.

Description

As with other neotheropods, the cervical vertebrae of ''Lucianovenator'' possess a complex system of fossae (pits) and laminae (ridges) that connect the main body of each vertebra (centra), front and rear joint plates (pre- and post- zygapophyses), and top and bottom rib facets (diapophyses and pleurapophyses) to each other. Although the cervicals of ''Lucianovenator'' possess many fossae, four particular examples of paired fossae (four on each side of the vertebrae) can be used to distinguish it from other neotheropods. The first of these is deep pit located directly at the base of each prezygapophysis, and the second is a larger pit is located immediately behind it. These two pits are obscured by a ridge known as a prezygapophyseal centrodiapophyseal lamina, which connects each prezygapophysis to the each diapophysis, and each diapophysis to the rear portion of the centrum. A third fossa is located at the rear portion of the vertebra. It too is obscured from the side, this time by the centropostzygapophyseal lamina which connects each postzygapophysis to the rear portion of the centrum. Each of the third fossae connects to a pair of large internal cavities which lie adjacent to the canal for the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

. This combination of features is unique to ''Lucianovenator,'' as no other coelophysoid possesses all of these features at once. The first and third pairs of fossae are similar to those of '' "Syntarsus" kayentakatae'', but the second pair is not. The third pair does connect to internal cavities in ''

Coelophysis bauri ''Coelophysis'' ( traditionally; or , as heard more commonly in recent decades) is a genus of coelophysid theropod dinosaur that lived approximately 215 to 201.4 million years ago during the Late Triassic period from the middle Norian to ...

'', but so does the first pair, unlike the case in ''Lucianovenator''. Another of ''Lucianovenator'''s distinguishing traits is that the anterior cervical ribs are very long (more than five times as long as the cervical centra). The fourth diagnostic pair of cervical fossae in ''Lucianovenator'' is also the only

autapomorphy In phylogenetics, an autapomorphy is a distinctive feature, known as a Synapomorphy, derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or Outgroup (cladistics), outgroup taxa, not ...

(unique distinguishing trait) of the genus''.'' ''Lucianovenator'' is unique in the fact that the edge of each centrodiapophyseal lamina (which connects each diapophysis to the centrum) acquires a long and deep pit, which becomes progressively longer and deeper towards the base of the neck. In cervical 9, the pit is nearly the entire length of the centrodiapophyseal lamina, and is so deep that it is not completely visible from the side.

Classification

A phylogenetic analysis published along with the description of ''Lucianovenator'' assigned it to the

Coelophysidae Coelophysoidea is an extinct clade of theropod dinosaurs common during the Late Triassic and Early Jurassic periods. They were widespread geographically, probably living on all continents. Coelophysoids were all slender, carnivorous forms with a ...

, in a clade with '' Coelophyis rhodesiensis'' and ''

Camposaurus ''Camposaurus'' ( ) is a coelophysid dinosaur genus from the Norian stage of the Late Triassic period of North America. The pertinent fossil remains date back to the early to middle Norian stage, and is widely regarded as the oldest known neothe ...

''. This clade is supported by a single feature, the fact that the zygapophyses of the sacral vertebrae are fused. The authors of the paper suggested that the relative rarity of theropods in Rhaetian deposits compared to Norian deposits may be the result of

taphonomic bias Taphonomy is the study of how organisms decay and become fossilized or preserved in the paleontological record. The term ''taphonomy'' (from Greek , 'burial' and , 'law') was introduced to paleontology in 1940 by Soviet scientist Ivan Efremov ...

rather than a decline in diversity.

References

{{Taxonbar, from=Q30116769 Coelophysoidea Dinosaur genera Rhaetian dinosaurs Fossil taxa described in 2017 Dinosaurs of Argentina

Discovery

Description

Classification

See also

References