• Two members of the Paja Formation are recognized, the Arcillolitas abigarradas (Barremian–Aptian; 480 m thick) and Arcillolitas con nodulos huecos (Aptian; 80 m thick; Fig. 1; Etayo-Serna 1968; Guerrero 2002a, b). Macrofossils are for the most part preserved in calcareous concretions; the part of this formation richest in fossil vertebrates appears to be the Barremian–Aptian aged Arcillolitas abigarradas Member (Etayo-Serna 1968). The Arcillolitas abigarradas forms extensive natural outcrops in the area around Villa de Leyva (Fig. 1). Ammonites are exceptionally abundant and three-dimensionally preserved in this region. Thus, relative age is constrained primarily by ammonite biostratigraphy, relying heavily on the zonation scheme proposed by Etayo-Serna (1968) and refined by subsequent authors (Patarroyo 2000; Hoedemaeker 2004). Correlation between Colombian (Caribbean Subprovince, Tethyan Realm) and European (Mediterranean Subprovince, Tethyan Realm) ammonite zones has been attempted based on genera and even species shared between the two regions (Patarroyo 2000; Hoedemaeker 2004; Kakabadze et al. 2004). These include species of Nicklesia, Pulchellia, Heinzia, Pseudohaploceras, Colchidites, Cheloniceras, Acanthohopclites, Colombiceras and Dufrenoyia, among others (Etayo-Serna 1968; Patarroyo 2000; Hoedemaeker 2004; Kakabadze et al. 2004).
Sauroposeidon proteles: OMNH 53062. Its type locality is OMNH locality V821, which is in an Aptian/Albian terrestrial claystone in the Antlers Formation of Oklahoma.
Paluxysaurus jonesi: FWMSH 93B-10-18, a partial skull (left maxilla with teeth, nasal). Its type locality is Jones Ranch Quarry, SMU Loc. v282, FWMSH 93B-10, which is in an Aptian coarse channel fill sandstone/sandstone in the Twin Mountains Formation of Texas.