The teeth of two megatooth macro-predatory shark species (Carcharocles chubutensis and Carcharocles megalodon; Otodontidae, Chondrichthyes) occur within the Miocene Chesapeake Group of Maryland, U.S.A. Definitive separation between all the teeth of Carcharocles chubutensis and Carcharocles megalodon is impossible because a complex mosaic evolutionary continuum characterizes this transformation, particularly in the loss of lateral cusplets. The cuspleted and uncuspleted teeth of Carcharocles spp. are designated as chronomorphs because there is wide overlap between them both morphologically and chronologically. In the lower Miocene Beds (Shattuck Zones) 2-9 of the Calvert Formation (representing approximately 3.2 million years, 20.2-17 Ma, Burdigalian) both cuspleted and uncuspleted teeth are present, but cuspleted teeth predominate, constituting approximately 87% of the Carcharocles spp. teeth represented in our sample. However, in the middle Miocene Beds 10-16A of the Calvert Formation (representing approximately 2.4 million years, 16.4-14 Ma, Langhian), there is a steady increase in the proportion of uncuspleted Carcharocles teeth. In the upper Miocene Beds 21-24 of the St. Marys Formation (representing approximately 2.8 million years, 10.4-7.6 Ma, Tortonian), lateral cusplets are nearly absent in Carcharocles teeth from our study area, with only a single specimen bearing lateral cusplets. The dental transition between Carcharocles chubutensis and Carcharocles megalodon occurs within the Miocene Chesapeake Group. Although this study helps to elucidate the timing of lateral cusplet loss in Carcharocles locally, the rationale for this prolonged evolutionary transition remains unclear.

A description and analysis is given of a single physeteroid tooth, from the Neogene of the Nutrien Aurora Phosphate Mine (formerly known as the Lee Creek Mine, Aurora, North Carolina, USA), that was bitten either by the extinct megatoothed shark Otodus chubutensis or Otodus megalodon. The tooth shows three gouges, one of which also preserves raking bite traces, made as the serrations on the Otodus sp. tooth struck and cut into its surface. We do not know if these bite traces came about as a result of scavenging or active predation. However, because the bite traces occur on part of the skull, this suggests a predatory interaction. This tooth preserves the first evidence in the fossil record of a predatory/antagonistic interaction between a sperm whale and a megatoothed shark.

Geochemical Perspectives Letters Letter Letter Geochemical Perspectives Letters gastropods that lived from the late Oligocene to the Pliocene (Carter et al., 1994; Ward and Andrews, 2008). Ecphora in its various species and subspecies span nearly 10 Ma of time along Calvert Cliffs, Maryland within the Calvert, Choptank and St. Marys Formations. This genus is unique in the context of the Calvert Cliffs fauna, in that pronounced colouration is preserved in the sculpted calcitic (CaCO 3) outer shell layer, as opposed to the white aragonitic (also CaCO 3) nacreous inner shell layer (Fig. 1C). Most other mollusk shells of the Calvert Cliffs are composed principally of aragonite and occur as white chalky shells, or are completely leached out of some beds (Shattuck, 1904; Vokes, 1957; Petuch and Drolshagen, 2010). By contrast, Ecphora found in situ invariably maintains its rich red-brown colour, which fades gradually to light tan when exposed to sunlight. This striking colouration is preserved in specimens as old as 18 Ma and suggests the possibility that biomolecular fossils of shell-binding proteins and associated pigments might be preserved. Figure 1 A. Image showing characteristic colouration and shape of Ecphora gardnerae germonae; St. Marys Formation, Little Cove Point member, Driftwood Beach, Calvert County MD. B. Polymeric protein-rich residue from the calcitic portions of dissolved Ecphora shell from a St. Marys Formation, Driftwood Beach specimen. This material gives the distinctive colour to the shells. C. A polished cross-section of two costae from Ecphora gardnerae germonae reveals the colored calcitic outer layer and white aragonitic inner layer.

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New finds of remarkable coprolites (fossilized feces) are here reported from the famous Miocene marine sediments of the Chesapeake Group exposed along Calvert Cliffs (Maryland, U.S.A.).  Although vertebrate coprolites have been described from these deposits, here we provide the first description of tiny invertebrate fecal pellets. Thus far, these fecal pellets have only been found in the upper Miocene (Tortonian) St. Marys Formation. The micro-coprolites represent the coprulid ichnospecies Coprulus oblongus. The fecal pellets are found in small clusters or strings of dozens to masses of many hundreds. Pellets range in size from approximately 0.4 – 2.0 mm wide by 1.0 – 5.0 mm long, and range in color from gray to brownish black. Their length/diameter ratio is always very nearly 2. These coprulids have been found in a variety of Miocene fossils/concretions including a uranoscopid neurocranium, naticid gastropod, bivalve shells, barnacle tests, and in pellet-backfilled sinuous burrows through sediment. Because the fecal pellets are often found in tiny spaces or spaces thought to be inaccessible to shelled invertebrates, the coprulids are attributed to small and soft-bodied polychaetes or other annelids. Some coprolites attributed to crocodilians from the lower-middle Miocene Calvert Formation were tunneled into, presumably the result of coprophagy, by some unknown kind of organism(s). These compound trace fossils are in the form of burrows that excavate the coprolites, the sides of which are sculptured by scratch/gouge marks.