Fukuiraptor
Fukuiraptor is a genus of medium-sized megaraptoran theropod dinosaur of the Early Cretaceous epoch that lived in what is now Japan. Fukuiraptor is known from the Kitadani Formation and possibly also the Sebayashi Formation. Fukuiraptor may have been one of the basalmost members of Megaraptora, or a sister taxon to Australovenator.
History
The type specimen is a partial skeleton discovered in the Kitadani quarry near Katsuyama in the Fukui prefecture. 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, in the smallest case less than a quarter of the holotype's size. A tooth 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 gave a length of 5 meters and a weight of 300 kg. In 2014, its body mass was estimated up to. Molina-Pérez and Larramendi estimated a length of 4.3 meters and a weight of 590 kg in 2016.The distinctive teeth of Fukuiraptor show similarities with both carcharodontosaurids and tyrannosaurids. The holotype also had very large and flat manual unguals, which played a role in its initial classification as a dromaeosaurid as well as its current classification as a megaraptoran.
Classification
Initially considered a member of the Dromaeosauridae when first discovered, its initial describers considered it a carnosaur, related to Allosaurus. More recent studies consider it a megaraptoran, an enigmatic group which may have been part of the family Neovenatoridae. However, more recently, another analysis has proposed that all megaraptorans are actually tyrannosauroids, which would reclassify Fukuiraptor as a tyrannosauroid coelurosaur. Recent cladistic analysis of the theropod Gualicho has suggested that Fukuiraptor and other megaraptorans are either allosauroids, 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.