Unenlagia comahuensis Novas and Puerta, 1997

Age . Turonian-Coniacian.

Occurrence. Rio Neuquén Formation, Neuquén, Argentina.

Diagnosis. Deep lateral pits at the bases of the posterior dorsal and sacral neural spines; scapular blade strongly twisted against the glenoid region; postacetabular iliac blade distinctly concave dorsoposteriorly.

Remarks. Despite the fragmentary nature of the holotype specimen, Unenlagia is an important taxon supposedly close to the ancestry of birds (Novas and Puerta 1997). According to a phylogenetic analysis in Forster et al. (1998), it represents a member of basal birds that also includes Rahonavis and Archaeopteryx . However, the forearm proportions of Unenlagia, as far as can be judged from the preserved humerus, do not agree with a position within volant birds and Norell and Makovicky (1999) pointed out several characters shared with dromaeosaurids. Therefore, the species is treated as a separate OTU here.