First things first, all the bone data available has been scaled to fit the measurements provided for Deltadromeus's holotype, SGM-Din2. And what is known from SGM-Din2 isn't much. At all. A partial scapulocoracoid, a partial humerus, a femur, a proximal tibia and fibula, and some neural spines and some caudals. Basically everything in this skeletal schematic provided in Sereno's description, which restores it as a light weight, somewhat coelurosaurian theropod (with no regard for the paper's own measurements):
Which brings me to the elephant in the room. Deltadromeus's phylogeny, as with noasauridae as a whole, is a god damn mess.
In past years, Deltadromeus has been classified as anything from a giant coelurosaur, to an ornithomimid, to a carnosaur, a megaraptoran, merged with Bahariasaurus and that whole mess in its own right, an abelisaur, or some other vague ceratosaur. More recently it's been pinned down somewhat as some kind of noasaurid, among the basal ceratosaurs.
But usually among the elaphrosaurines, which are bizarre, somwhat bird-like herbivorous ceratosaurs which are so often mistaken for Middle Jurassic to Early Cretaceous ornithomimid offshoots, that it's SHOCKING. And this group is represented somewhat poorly by Elaphrosaurus itself, but ASTONISHINGLY well by Limusaurus, and maybe by quite a few "ornithomimid" remains from across Africa and Europe (I'm looking at you, Angeac "Ornithomimid").
But as of subsequent studies done in 2016 and 2017, it would appear that its affinities lie somewhere between basal noasauridae
(Rauhut & Carrano, 2016) and true noasaurines like Masiakasaurus (Wang et al. 2017). So I opted to take that route for this restoration, and see what happens.
Which was a stupid idea, because noasaurinae is poorly represented by Masiakasaurus, even more poorly represented by Noasaurus, and even MORE poorly by everything else.
Then all the remaining noasauridae that float around the clade, do just that. They're a bunch of scraps that float around the clade doing nothing helpful. Except Spinostropheus, which doesn't have good photos (which would have been SO much nicer to work with had they existed - its got a pretty good vertebral series).
The only constant for Deltadromeus these days seems to be that it and Gualicho are sister taxa, however that study (
Apesteguía et al. 2016) also dumped them in Neovenatoridae, along with everything deemed a "megaraptoran".
With those tiny, didactyl arms? Really?
So uh... RIP?
So yeah, I don't even know, guys. Deltadromeus is an enigma. And I'll definitely end up revisiting this one as more data crops up. Until then, kinda stuck with this one.
Deltadromeus agilis - SGM-Din2 (Sereno et al. 1996)
Gualicho shinyae - MPCN PV 0001 (Apesteguía et al. 2016)
Masiakasaurus knopfleri - FMNH PR 2481 (Carrano et al. 2002; Carrano et al. 2011), FMNH PR 2485 (Carrano et al. 2002; Carrano et al. 2011), and their referred isolated specimens.
Elaphrosaurus bambergi - MB R 4960 (Rauhut & Carrano, 2016)BONES USED:Skull - Speculative composite based off available data for Masiakasaurus
(Carrano et al. 2002; Carrano et al. 2011).
Vertebrae - Atlas speculative. Cervical vertebrae modified from Masiakasaurus
(Carrano et al. 2011). Anterior dorsal vertebrae restored from Masiakasaurus. Posterior dorsal vertebrae composites based on Deltadromeus neural spines (Sereno et al. 1996) and Elaphrosaurus centra (Rauhut & Carrano, 2016). Anterior and caudal vertebrae composites based on Deltadromeus neural spines (Sereno et al. 1996) and Elaphrosaurus centra (Rauhut & Carrano, 2016). Distal caudals speculative.
Ribs - Cervical ribs mostly speculative, with only the 6th represented in Masiakasaurus
(Carrano et al. 2011). Dorsal ribs speculative. Gastralia based on Gualicho (
Apesteguía et al. 2016).
Pectoral girdle - Scapulocoracoid restored after known elements from Deltadromeus (Sereno et al. 1996) and Gualicho (
Apesteguía et al. 2016). Sternal elements speculative. Furcula speculative.
Arms - Humerus from Deltadromeus (Sereno et al. 1996). Forearm and hand from Gualicho (
Apesteguía et al. 2016).
Pelvic girdle - Ilium modified from Masiakasaurus
(Carrano et al. 2011). Ischium modified from Masiakasaurus (Carrano et al. 2011). Pubis composite from Deltadromeus (Sereno et al. 1996), Gualicho (Apesteguía et al. 2016) and Masiakasaurus (Carrano et al. 2002; Carrano et al. 2011).
Leg - Femur based on Deltadromeus (Sereno et al 1996). Tibia and fibula modified from Gualicho (
Apesteguía et al. 2016) and Elaphrosaurus (Rauhut & Carrano, 2016). Foot restored from Gualicho (Apesteguía et al. 2016) and Masiakasaurus (Carrano et al. 2002; Carrano et al. 2011). Hallux and metatarsal V speculative.
Scale bar represents 1m (with 10cm intervals) in relation to the Deltadromeus agilis holotype specimen, SGM-Din2.
Apesteguía, S., Smith, N.D., Valieri, R.J. and Makovicky, P.J., 2016. An unusual new theropod with a didactyl manus from the Upper Cretaceous of Patagonia, Argentina. PloS one, 11(7), p.e0157793.
Carrano, M.T., Sampson, S.D. and Forster, C.A., 2002. The osteology of Masiakasaurus knopfleri, a small abelisauroid (Dinosauria: Theropoda) from the Late Cretaceous of Madagascar. Journal of Vertebrate Paleontology, 22(3), pp.510-534.
Carrano, M.T., Loewen, M.A. and Sertich, J.J., 2011. New materials of Masiakasaurus knopfleri Sampson, Carrano, and Forster, 2001, and implications for the morphology of the Noasauridae (Theropoda: Ceratosauria). Smithsonian Institution Scholarly Press.
Rauhut, O.W. and Carrano, M.T., 2016. The theropod dinosaur Elaphrosaurus bambergi, from the Late Jurassic of Tendaguru, Tanzania. Zoological Journal of the Linnean Society, 178(3), pp.546-610.
Sereno, P.C., Dutheil, D.B., Iarochene, M., Larsson, H.C., Lyon, G.H., Magwene, P.M., Sidor, C.A., Varricchio, D.J. and Wilson, J.A., 1996. Predatory dinosaurs from the Sahara and Late Cretaceous faunal differentiation. Science, 272(5264), pp.986-991.
Wang, S., Stiegler, J., Amiot, R., Wang, X., Du, G.H., Clark, J.M. and Xu, X., 2017. Extreme ontogenetic changes in a ceratosaurian theropod. Current Biology, 27(1), pp.144-148.