Figure 3.

(a) Phylogenetic positions of Effigia and Shuvosaurus among basal archosaurs. Unique tree shown (81 characters, length=156, RI=0.8320, CI=0.5897). The placement of Effigia within Theropoda requires the addition of 27 steps and the placement sister to ornithomimids requires the addition of 30 steps. The first number is the decay value and the second number is the bootstrap value. (b) The convergences listed below are present in Effigia and are characters that describe the dinosaurian clade and nested theropod clade. (i) Dinosauria. Reduction of arm/leg ration, postfrontal absent, ‘offset femoral head’, elongated parabasisphenoid. (ii) Neotheropoda. Enlargement of the preacetabular process of the ilium, incorporation of additional sacral vertebrae, hollow limbs, ‘antitrochanter’, present on the ilium, fusion of sacral vertebrae into rigid rod, fusion of the sacral neural arches, left and right oppression of the ischium, cervical vertebra pleurocoels. (iii) Coelurosauria. Increased pubic boot size, elongated prezygapophyses in distal caudal vertebrae, preacetabular fossa. (iv) Ornithomimosauria. Enlargement of the orbit, posteroventral rotation of the squamosal, anteroventrally angled quadrate, lacrimal–frontal contact absent. (v) Clade within Ornithomimosauria. Posterior directed process on each diapophysis of the posterior cervical vertebrae, edentulous jaws.