| Popis: |
Planicoxa venenica DiCroce & Carpenter, 2001 2001 Planicoxa venenica DiCroce & Carpenter, p. 190. Holotype. DMNH 42504, left ilium. Paratypes. DMNH 42511, 42516, 42518, 42519, 42520, 42521, 42522, 42524, 42513, 42515, 42525, 42523, 42526, 42527, 42510, 42514, 42517, 42508, 42507, 42505, 40917, 40914, 40918, 42506, 42509, 42512 (DiCroce & Carpenter 2001). Locality and horizon. Tony’s Bone Bed, near Moab, Grand County, Utah (DiCroce & Carpenter 2001); Poison Strip Member, Cedar Mountain Formation, lower–middle Aptian. Generic diagnosis. As for species by monotypy. Specific diagnosis. Provisionally diagnostic basal styracosternan distinguished from Osmakasaurus depressus, Cedrorestes crichtoni, and Iguanacolossus fortis by the convex dorsal margin of the ilium (Fig. 12 B). Remarks. The reassessment of USNM 4753 given above casts doubt upon the supposed horizontal postacetabular process of DMNH 42504, which was the primary feature used by DiCroce & Carpenter (2001) in diagnosing Planicoxa venenica. In dorsal view, the postacetabular process of DMNH 42504 is heavily fractured (Fig. 12 A). There are additional smaller cracks along the dorsal margin of the ilium visible in lateral view (Fig. 12 B). It is likely that the fractures on the postacetabular process and dorsal margin are the results of deformation of the ilium, akin to what is proposed above for the left ilium of USNM 4753. If so, then the diagnosis of Planicoxa venenica loses its key feature. Nevertheless, pending recovery of additional iguanodont specimens from the Poison Strip Member, Planicoxa venenica is herein retained as a provisionally viable taxon, as its ilium can still be differentiated from all other basal styracosternan ilia known from the Early Cretaceous of North America by its convex dorsal margin. The dorsal margin of the ilium is convex cranial to the distorted part of the bone, indicating that this is probably a real feature (Fig. 12 B). |
