Since 1999, Centro Portugues de Geo-Historia e Pre-Historia carried out research in the Papo-Seco Formation, during which a set of vertebrate remains (bones and teeth) were found: turtles, fishes, tetanuran
theropods (including derived maniraptorans/birds) and iguanodontian ornithopods among dinosaurs (Figueiredo, 2002, 2004, 2005, 2007, 2008, 2014).
There is a second basal tetanuran represented at La Cantalera.
The taxa identified to date are included in basal tetanurans such as baryonychines and possible carcharodontosaurids, as well as coelurosaurians such as maniraptorans, dromaeosaurines, velociraptorines and "paronychodontids.
The rest of the theropod teeth from La Cantalera present a combination of characters that are derived for the tetanurans, such as marked lateromedial flattening, the absence of either or both of the denticulate carinae, and a posterior side that is markedly concave.
However, new information suggests that some of these taxa constituted endemic clades, or primitive grades, of basal tetanuran theropods (Zhao et al.
However, Monolophosaurus and Chuandongocoelurus show an intriguing combination of derived, tetanuran synapomorphies and primitive features shared with non-tetanurans, which together suggest a basal position within Tetanurae (Zhao et al.
Similarly, its phylogenetic relationships are poorly resolved, and most authors have regarded it as a basal tetanuran theropod of uncertain affinities (e.
Fukuiraptor was originally described as a basal tetanuran theropod, likely an allosauroid, but its more precise phylogenetic affinities have proven elusive (Brusatte and Sereno, 2008; Hocknull et al.
These theropods, including carcharodontosaurians and spinosaurids, belong to basal tetanuran clades.
The oldest large theropods of Asia, from the Middle Jurassic, belonged to largely endemic clades of basal tetanuran theropods.
However, Chuandongocoelurus is exceptionally small among basal tetanurans (Table 1), with an estimated mass of only 13 kg.