Such a strange animal. Last described in the 1920s, it hasn't been dealt with seriously since, although the original description is quite thourough and detailed (albeit in German). This animal has been linked to the abelisaurs, and now appears to be unique simply because it has the longest legs for its mass than any other abelisaur known.
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Elaphrosaurus and Limusaurus are each apparently some of the most basal members of a group called Abelisauria. This includes "Elaphrosauridae" (incl. perhaps Spinostropheus), Noasauridae, and Abelisauridae. Sereno et al. originally indicated through a limited analysis that Deltadromeus might be a coelurosaur, but most of these features were recently found to also appear in various abelisaurs ("abelisaur" refers to Abelisauria, and abelisaurian, not abelisaurids = Abelisauridae). The huge shoulders, thin feet, and various other vertebral features now seem to point to a large-bodied, late-surviving basal abelisaurian, for Deltadromeus. This being based on two analyses which use mostly the same dataset to produce their results. That's all I know.
At the moment, I think there's a lot about Delta we don't know about, the material is actually pretty scarce for the most part (we are missing large areas, such as most of the limbs and vertebrae) that obscures its affinities, hence the large number of differing opinions that evolve as new data gets added.
This is still generally true, at least historically when you consider that Ceratosauria as it is still conceived may contain Abelisauria. Recent arguments prefer placing Abelisauria outside of a classic Ceratosauria, which would contain perhaps only Ceratosaurus, Coelophysidae, and a few other taxa, and may not contain Limusaurus, which would be closer to Abelisauria.
There is a small set of well-done analyses that indicate that Abelisauria, then Ceratosauridae, then Ceolophysoidea are serial outgroups of Tetanurae. Some analyses place Coelophysoidea in Ceratosauria, while others place all of them in Ceratosauria. There isn't a whole lot of consensus on this.
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Thanks. Some studies muck around with where Elaphrosaurus sits relative to noasaurids and abelisaurids. It is currently undergoing new study, so hopefully clarifying phylogenetic works can be made.
That came after I started looking at the possible skull of Noasaurus, with the jaw of Masiakasaurus. These are close in morphic space, technically, so I figured a basal, nontetanuran jaw, with down-sloping snout. That's pretty much it. It was probably a little larger, just how Masiakasaurus' head is much bigger. I should post my Noasaurus sometime, to really draw attention to these little guys' weirdness.