171 Hunt et al., eds., 2012, Vertebrate Coprolites. New Mexico Museum of Natural History and Science, Bulletin 57. BROMALITES FROM THE MISSISSIPPIAN BEAR GULCH LAGERSTÄTTE OF CENTRAL MONTANA, USA ADRIAN P. HUNT 1 , SPENCER G. LUCAS 2 , JUSTIN A. SPIELMANN 2 AND MARTIN G. LOCKLEY 3 1 Flying Heritage Collection, 3407 109th St SW, Everett, WA 98204, e-mail: adrianhu@flyingheritage.com; 2 New Mexico Museum of Natural History and Science, 1801 Mountain Road NW, Albuquerque, NM 87104, e-mail: spencer.lucas@state.nm.us, justin.spielmann1@state.nm.us; 3 Dinosaur Tracks Museum, University of Colorado Denver, CO 80217-3364, e-mail: martin.lockley@ucdenver.edu Abstract—The Bear Gulch Lagerstätte (Mississippian: Chesterian) of central Montana is characterized by its extensive ichthyofauna. The vertebrate ichnofauna includes six morphotypes/ichnotaxa of bromalites: (1) morphotype A coprolites are large and ovoid to pear shaped; (2) morphotype B coprolites are elongate and triangular in shape; (3) morphotype C coprolites are elongate and rounded; (4) morphotype D coprolites are small, ovoid and composed of dense groundmass; (5) spiral coprolites; and (6) Ostracobromus snowyensis ichnogen. et ichnosp. nov, is ovoid and characterized by inclusions of multiple valves of ostracods set in a groundmass and is possibly a regurgitalite. The Bear Gulch assemblage provides a baseline for further work on Mississippian vertebrate bromalites. INTRODUCTION Sedimentary rocks of the Rocky Mountains yield one of the world’s most extensive fossil records of Carboniferous marine and terrestrial life (Nelson and Lucas, 2011). The Bear Gulch Lagerstätte in the Big Snowy Mountains of Montana has been extensively studied (e.g., Horner and Lund, 1985; Lund et al., 1993, 2012; Schram and Horner, 1978; Schram, 1979; Grogan and Lund, 2002). Recent stratigraphic studies place this Lagerstätte in the Bear Gulch Limestone Member of the Tyler Formation (Porter et al., 2005; Nelson and Lucas, 2011) whereas most paleontologi- cal literature continues to refer this fauna to the Heath Formation (e.g., Lund et al., 2012). The Bear Gulch is Chesterian in age based on evidence from conodonts (Scott, 1973), palynomorphs (Cox, 1986), and diverse vertebrate and invertebrate faunas (Grogan and Lund, 2002). The fossils from the Bear Gulch Limestone include palynomorphs, algae, conulariids, sponges, brachiopods, bivalves, nautiloids, worms, arthropods, echino- derms and more enigmatic forms (e.g., Sphenothallus, Typhloessus). The most distinctive element of the Lagerstätte is the fossil ichthyofauna, which comprises more than 120 described taxa including an exception- ally diverse assemblage of chondrichthyans as well as a petromyzontiform, an acanthodian, many actinopterygians and several sarcopterygians (Horner and Lund, 1985; Lund et al., 1993; Grogan and Lund, 2002). Zidek (1980) described spiral coprolites from Bear Gulch found in association with Acanthodes lundi. The purpose of this paper is to describe additional vertebrate bromalites from the Bear Gulch Lime- stone. Many bromalites occur in the Bear Gulch Limestone but in general they have previously not been collected or they have been discarded (B. Hawes, personal commun., 1995). Bill Hawes and Paula Ott collected and retained a small number of specimens (11), which are described here. The ichnofossil assemblage contains five morphotypes, one of which is distinct enough to be named as a new ichnogenus and ichnospecies. These specimens are considered to represent bromalites because they are discrete rounded bodies composed of phosphatic groundmass and frag- mented fish material. The bromalites cannot be related to the Lagerstätte facies recognized by Grogan and Lund (2002). All specimens are pre- served flattened on surfaces of split laminae of shale and are in the collection of the New Mexico Museum of Natural History and Science (NMMNH). BROMALITES Morphotype A Morphotype A are large and ovoid to pear shaped with dimen- sions of up to 400 mm by 250 mm. NMMNH P-54188 is pear shaped and 49.7 mm long and 31 mm wide (Fig. 1A). One end is rounded and thicker, with a sharp margin, whereas the other end is more acute in shape, thinner and shows evidence of decay. Presumably one end was exposed above the sediment surface for a longer period than the other and subjected to deterioration. This bromalite contains a large amount of fish material in a phosphatic groundmass. There is a slight indication of a spiral structure. NMMNH P-63718 is similarly pear shaped with a length of 51 mm and a width of 34 mm, with an inferred maximum thickness above the sediment interface of 3 mm (Fig. 1D). The bromalite contains many fish scales, and there is scattered debris around the margin that indicates some decay prior to fossilization. The third specimen (NMMNH P-54189) is 400 mm long and 250 mm wide and is largely covered by a thin lamina of shale except for an area of 80 mm by 28 mm (Fig. 1C). A halo of small fragments, including fish scales, indicates that the bromalite decayed on the sediment surface. NMMNH P-54191 preserves half a bromalite on the margin of a piece of matrix with maximum dimensions of 48 and 27 mm (Fig. 1B). The speci- men seems to be weathered and contains abundant fish debris in a phos- phatic groundmass. This morphotype is considered to represent a coprolite because of the presence of abundant fish debris preserved within a phosphatic groundmass in a discrete rounded body. Given the diversity of the ich- thyofauna in the Lagerstätte it is not possible to match the coprolite with a producer. Morphotype B The bromalites of morphotype B are elongate and triangular in shape. NMMNH P-54135 is elongate and tapering and contains a large number of scales, some of which are imbricated. The coprolite is 31.5 mm long and 22.1 mm at its widest point and 4-5 mm thick (Fig. 1E). This morphotype is also considered to represent a coprolite on the basis of abundant fish debris preserved within a phosphatic groundmass in a discrete rounded body. It is not clear which fish produced this coprolite. Morphotype C Morphotype C bromalites are elongate and rounded. NMMNH P-54133 is 36 mm long and a maximum width of 12 mm (Fig. 1F). It is elongate and ovoid in cross section with a thin, right angular extension that is 21 mm long. An area of the other end of the bromalite has fallen out, leaving a partial mold. The bromalite contains abundant phosphatic groundmass and little bone material. NMMNH P-54137 is an elongate and irregularly-shaped bromalite lacking its margins, which were dam- aged during collection (Fig. 1G). The abundance of phosphatic ground-