Although Baron would later revise his dataset and conclude that the affinities of Chilesaurus remain uncertain. While multiple analyses find it to be a basal tetanuran (Novas, Cau, 2015 2018), it has also been found to be a coelurosaur (Dal Sasso et al. 2018).

and Matzia et al. 2021 criticized all of the aforementioned studies for not actually testing the tetanurine affinities of Chilesaurus, with Fonseca et al. 2024 finding an ornithischian position unlikely.

The final didactyl theropod to talk about is the equally enigmatic Chilesaurus. Known from the Late Jurassic-aged Toqui Fm of Chile, most of the skeleton is preserved. Baron & Barrett 2017, Baron 2018 and Müller & Dias-da-Silva 2019 found Chilesaurus as a basal ornithischian, however, Muller et al.-

A more recent study found Gualicho in a completely different position - Ceratosauria. Specifically an elaphrosaurine in a polytomy with Deltadromeus, Aoniraptor & Bahariasaurus (Cau, 2024). Calvo et al. 2025 found that Gualicho was most likely not closely related to Megaraptora.

However, a later analysis (Porfiri et al. 2018) found Gualicho rather at the base of Coelurosauria. A 2022 study found Gualicho also as a coelurosaur, though rather as a tyrannosauroid sister to Tyrannosauridae (Rolando et al. 2022).

Ok, now we're moving out of Coelurosauria, or are we? Gualicho is a theropod from the Huincul Fm of Argentina with tiny didactyl hands. Its original description found it as the sister taxon of (the also enigmatic) Deltadromeus, as a neovenatorid, alongside Megaraptora (Apesteguía et al. 2016).

but the subsequent study is yet to be published. The only known images of this therizinosaur are from a 2019 Twitter post. The aforementioned abstract only mentioned the 2 arms, though the images also show various vertebrae and a partial pelvis.

Despite the most striking feature of therizinosaurs being their long fingers and claws, a specimen from the Urlibe Khudak locality of Mongolia, found in 2012, actually possessed functionally didactyl hands. It was mentioned in a SVP 2015 abstract-

Funston et al. 2020's phylogenetic analysis found both as members of Heyuanninae, though not as sister taxa, rather clading with Jiangxisaurus & Banji and H. yanshini & Nemegtomaia, respectively.

Interestingly, the didactyl condition would later reevolve in oviraptorosaurs in Oskoko & Heyuannia huangi, both from Asia. Both also show great reduction in their arms as a whole.

The tiny, early oviraptorosaurs, the caudipterids (Caudipteryx, Xingtianosaurus and Similicaudipteryx) also had a two-fingered arm. All known members of Caudipteridae come from the Early Cretaceous of China.

The classification of Balaur is still quite unclear. Analyses have found it to be either a velociraptorine (Brusatte, Turner, Napoli et al. 2013, 2021, 2021, respectively), basal avialan (Godfroit, Lee, Cau, Stoicescu et al. 2013, 2014, 2015, 2024, respectively) or an unenlagiine (Foth et al. 2025)

The second (non-?) avian didactyl is the ambiguous Romanian Balaur. Known from a mostly complete postracial skeleton lacking the skull, Balaur possesses a reduced third finger (Csiki et al. 2010). Some studies have suggested it to be a junior synonym of Elopteryx (Stoicescu et al. 2024)