Content area
Full Text
Articles
Introduction
Duck-billed dinosaurs, or hadrosaurs, rank among the most diverse and successful dinosaur groups. They have been found across Europe, Asia, North and South America, and Antarctica (Case et al., 2000; Lund and Gates, 2006; Prieto-Márquez, 2010b) concentrated in a 15 million year period toward the end of the Late Cretaceous (Campanian-Maastrichtian; Horner et al., 2004). These herbivorous browsers are split into a diphyletic origin of hollow-crested and solid-crested species (Horner, 1990), and their remains are often prolific, ranging from isolated elements to complete articulated skeletons. With the addition of comprehensive ontogenetic stages including eggs and embryos along with a vast array of trace fossils, hadrosaurs provide some of the most extensive data sets of any dinosaur group (Horner et al., 2004).
For over a century, vertebrate fossils have been collected from the San Juan Basin (SJB) of New Mexico (upper Campanian, Late Cretaceous; Fig. 1; Williamson, 2000). Although the hadrosaurid record of the SJB pales in comparison to the well-preserved specimens and growth series from the northern United States and Canada, many enigmatic taxa have been discovered. In 1904, Barnum Brown briefly collected and later described the solid-crested Kritosaurus navajovius (Brown, 1910; AMNH 5799), but the SJB remained primarily unexplored until Charles Hazelius Sternberg arrived in 1921. Sternberg, aged 71, collected for three consecutive field seasons discovering the hollow-crested hadrosaurids Parasaurolophus tubicen (Wiman, 1931; PMU R.1250) and Parasaurolophus cyrtocristatus (Ostrom, 1961, 1963; FMNH P27393), the ceratopsian Pentaceratops sternbergii (Osborn, 1923; AMNH 6325), and vast amounts of isolated material. More recent excavations have continued to expand the diversity of the region with the additions of the solid-crested Anasazisaurus horneri (Hunt and Lucas, 1993; BYU 12950) and Naashoibitosaurus ostromi (Hunt and Lucas, 1993; NMMNH P-16106), but simultaneously complicated the taxonomy (Prieto-Márquez, 2013; Sullivan and Lucas, 2014).
Figure 1
Stratigraphic distribution of hadrosaurid taxa and key specimens in the San Juan Basin, New Mexico (modified from Sullivan and Lucas, 2014). Prieto-Márquez (2013) considered A. horneri as a junior synonym of K. navajovius. LVA=North American Land Vertebrate Age; Hadrosaur Biostrat=Hadrosaur Biostratigraphy.
[Figure Omitted; See PDF]
Here we present the first descriptive account of isolated hadrosaurid material at the Field Museum of Natural History (FMNH) from C. H. Sternberg's 1922 expedition of the SJB. Although detailed locality...