undet. Ammonoidea
From the collection of Yale Peabody Museum. Free to download, adapt and use — no permission needed.
Geological context: Late Cretaceous, Fox Hills Fm, Timber Lake Mbr. Collection locality: concs., float on flats along NW-SE-trending road, .5 mi NW of Eagle Butte, and 1.8 mi SSE of Eagle Butte village, Ziebach County, South Dakota, USA. Collected by Karl M. Waage, David E. Schindel, Neil H. Landman, Danita Brandt, 1983. IP number 337857; lot count 1; original nature=chip/slab (multi-specimen); taphonomy=concretion; accn=IPA.07048; associatedwith=on same slab: IP.337851,on same slab: IP.337852,on same slab: IP.337853,on same slab: IP.337854,on same slab: IP.337855,on same slab: IP.337856,on same slab: IP.337857,on same slab: IP.337858,on same slab: IP.337859,on same slab: IP.337860,on same slab: IP.337861,on same slab: IP.337862,on same slab: IP.337863,on same slab: IP.337864,on same slab: IP.337865,on same slab: IP.337866,on same slab: IP.337867,on same slab: IP.337868,on same slab: IP.337869,on same slab: IP.337870,on same slab: IP.337871.
Yale Peabody Museum’s own description