Continental trace fossils and museum exhibits - Geological Curators ...

Figure 6. A typical Late Triassic dinosaur footprint fromnear Tucumcari, New Mexico, NMMNH P-44218, assignedto Grallator, the track of a small theropod. Scale is incentimetres.Figure 7. Brachychirotherium (probably aetosaur) tracksfrom Upper Triassic Redonda Formation near Tucumcari,New Mexico, NMMNH P-44193. Scale is in centimetres.-266-Trace fossil identification for the publicThe geology of New Mexico is diverse, with rocks ofvirtually every time period since the Proterozoicexposed at the surface in some part of the state. This,and the arid and rugged landscape, make fossildiscovery by members of the public common.Each year, New Mexico residents bring hundreds offossils and would-be fossils that they have found tothe NMMNH to be identified. Many of these objectsare concretions or other rounded rocks thought to bedinosaur eggs. Only once has an actual dinosaur eggbeen brought to the Museum, in 1995, when a fathercame in with his three-year-old son who had pickedup pieces of Jurassic dinosaur eggshell on a hike westof Albuquerque, New Mexico. Only a few kinds oftrace fossils are usually brought in by members of thepublic, mostly crustacean burrows assigned toOphiomorpha and Thalassinoides, which are commonin Cretaceous shoreline sandstones in northern NewMexico.Trace fossils on exhibitSeveral Museum exhibits, past, present and planned,have or will feature trace fossils. An exhibit devotedto the Robledo Mountains Permian footprints ran forabout a decade and was recently dismantled. TheMuseum will open a Triassic Hall in 2007, and LateTriassic tracks of dinosaurs and other archosaursfrom the Tucumcari area in eastern New Mexico(Figures 6-7) will be featured. The fragments ofdinosaur eggshell, found by the three-year-old boyjust west of Albuquerque (Bray and Lucas 1997), arenow on display in the Museum’s renovated JurassicHall, which opened in August 2004. The Museum’sCretaceous exhibit, called ‘New Mexico’s seacoast’,begins with the world-famous dinosaur tracks from a100-million year old seashore now exposed at ClaytonLake State Park in northeastern New Mexico (Figure8). These are mostly tracks of early ornithopoddinosaurs that browsed vegetation along the EarlyCretaceous coastline (Lockley et al. 2000).In the summer of 2004, a large trackway belonging tothe ichnospecies Diplichnites cuithensis wasdiscovered in Upper Pennsylvanian strata in a rugged,remote canyon in northern New Mexico (Lucas et al.2005a). This trackway is attributable to the giganticmyriapod Arthropleura. The specimen, preserved ona thick bed of sandstone, was loaded onto a truck andtransported to the New Mexico Museum of NaturalHistory and Science in the spring of 2005. TheMuseum also purchased a life-size plastic model ofArthropleura to accompany the trace fossil. Mostvery large specimens of Diplichnites cuithensis areknown from field localities, and only casts or replicas