''Fukuiraptor'' ("thief of
Fukui") 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 medium-sized
megaraptora
Megaraptora is a clade of carnivorous theropod dinosaurs. Its derived members, the Megaraptoridae are noted for their large hand claws and powerfully-built forelimbs, which are usually reduced in size in other large theropods. Although undoubt ...
n
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 of 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 ...
epoch
In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured.
The moment of epoch is usually decided b ...
(either
Barremian
The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 125.77 Ma (million years ago) and 121.4 ± 1.0 Ma (Historically, this stage was placed at 129.4 million to approximately 125 million years ago) It is a ...
or
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 ...
) that lived in what is now
Japan
Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
.
''Fukuiraptor'' is known from the
Kitadani Formation and possibly also the
Sebayashi Formation.
History
The
type specimen
In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...
is a partial skeleton (designated FPDM-V97122) discovered in the
Kitadani quarry near
Katsuyama in the
Fukui prefecture
is a Prefectures of Japan, prefecture of Japan located in the Chūbu region of Honshū. Fukui Prefecture has a population of 737,229 (1 January 2025) and has a geographic area of 4,190 Square kilometre, km2 (1,617 sq mi). Fukui Prefecture border ...
. It is thought that this specimen was not mature and an adult may have been larger. The remains of many other individuals have been found in the quarry, with numerous humeri, femurs, and teeth being assigned to this species.
However, the other individuals recovered from the same locality are mostly juveniles that were smaller than 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 ...
(Currie & Azuma, 2006), in the smallest case less than a quarter of the holotype's size. A tooth (NDC-P0001) discovered in a block of
conglomerate from the
Sebayashi Formation has been referred to ''Fukuiraptor'' as well.
Description

As indicated by its slender phalanges, ''Fukuiraptor'' was a relatively lightly built animal, regardless of its maturity.
The immature holotype is estimated to reach long and weigh in its initial description.
In 2010
Gregory Paul
Gregory Scott Paul (born December 24, 1954) is an American freelance researcher, author and illustrator who works in paleontology. He is best known for his work and research on theropod dinosaurs and his detailed illustrations, both live and sk ...
gave a length of 5 meters (16 ft) and a weight of 300 kg (660 lbs). In 2014, its body mass was estimated up to . Molina-Pérez and Larramendi estimated a length of 4.3 meters (14.1 ft) and a weight of 590 kg (1,300 lbs) in 2016.
The distinctive teeth of ''Fukuiraptor'' show similarities with both
carcharodontosaurids (being very compressed and blade-like, as well as having wrinkled enamel) and
tyrannosaurids
Tyrannosauridae (or tyrannosaurids, meaning "tyrant lizards") is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to fifteen genera, including the eponymous ''Tyrannosaurus''. The exact number of genera i ...
(having oblique blood grooves near the serrations).
The holotype also had very large and flat manual unguals (hand claws), which played a role in its initial classification as a dromaeosaurid (as the hand claws were mistaken for foot claws) as well as its current classification as a megaraptoran.
Classification
Initially considered a member of the
Dromaeosauridae
Dromaeosauridae () is a family of feathered coelurosaurian theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from ...
when first discovered, its initial describers considered it a
carnosaur, related to ''
Allosaurus
''Allosaurus'' ( ) is an extinct genus of theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period ( Kimmeridgian to late Tithonian ages). The first fossil remains that could definitively be ascribed to th ...
''. More recent studies consider it a megaraptoran, an enigmatic group which may have been part of the family
Neovenatoridae
Carnosauria is an extinct group of carnivorous theropod dinosaurs that lived during the Jurassic and Cretaceous periods.
While Carnosauria was historically considered largely synonymous with Allosauroidea, some recent studies have revived Carn ...
.
However, more recently, another analysis has proposed that all
megaraptora
Megaraptora is a clade of carnivorous theropod dinosaurs. Its derived members, the Megaraptoridae are noted for their large hand claws and powerfully-built forelimbs, which are usually reduced in size in other large theropods. Although undoubt ...
ns are actually
tyrannosauroids, which would reclassify ''Fukuiraptor'' as a
tyrannosauroid
Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinen ...
coelurosaur
Coelurosauria (; from Greek, meaning "hollow-tailed lizards") is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs.
Coelurosauria is a subgroup of theropod dinosaurs that includes compsognathids, ty ...
. Recent cladistic analysis of the theropod ''
Gualicho
''Gualicho'' (named in reference to the gualichu) is an enigmatic genus of theropod dinosaurs. The type species is ''Gualicho shinyae''. It lived in what is now northern Patagonia, on what was then a South American island continent split off fro ...
'' has suggested that ''Fukuiraptor'' and other megaraptorans are either
allosauroid
Carnosauria is an extinct group of carnivorous theropod dinosaurs that lived during the Jurassic and Cretaceous periods.
While Carnosauria was historically considered largely synonymous with Allosauroidea, some recent studies have revived Carn ...
s, or non-tyrannosauroid basal coelurosaurs.
It has been suggested that ''Fukuiraptor'' is a close relative to the Australian megaraptoran known as ''
Australovenator'', however a subsequent study has placed ''Australovenator'' as a
megaraptorid megaraptoran alongside other derived South American taxa, while ''Fukuiraptor'' remains a megaraptoran outside of Megaraptoridae.
Below is a cladogram reconstructing the position of ''Fukuiraptor'' in the Megaraptora as per Delcourt and Grillo, 2018.
Palaeoecology

In the
Kitadani Formation, where fossils of ''Fukuiraptor'' have been recovered,
fossils of other vertebrates have been preserved. Among the species that have been properly described and named are ''
Fukuisaurus tetoriensis'', a
styracostern ornithischia
Ornithischia () is an extinct clade of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek ...
n, ''
Fukuititan nipponensis'', a
titanosauriform 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 ...
, ''
Koshisaurus katsuyama'', a
hadrosauroid
Hadrosauroidea is a clade or superfamily of ornithischian dinosaurs that includes the "duck-billed" dinosaurs, or Hadrosauridae, and all dinosaurs more closely related to them than to ''Iguanodon''. Their remains have been recovered in Asia, Euro ...
ornithischian, ''
Fukuivenator paradoxus'', a possible
therizinosaurian 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 ...
, and ''
Fukuipteryx prima'',
an
avialan
Avialae ("bird wings") is a clade containing the only living dinosaurs, the birds, and their closest relatives. It is usually defined as all theropod dinosaurs more closely related to birds (Aves) than to deinonychosaurs, though alternative defi ...
as defined by the authors''.''
External links
Image of the holotype skeleton, published by the twitter account of Thomas Holtz*
References
{{Taxonbar, from=Q132536
Megaraptora
Dinosaur genera
Aptian dinosaurs
Taxa named by Philip J. Currie
Fossil taxa described in 2000
Dinosaurs of Japan