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Solomons, MD, United States

Visaggi C.C.,University of North Carolina at Wilmington | Godfrey S.J.,Calvert Marine Museum
Journal of Vertebrate Paleontology | Year: 2010

Shark teeth are the most common vertebrate fossils found along the western shore of Chesapeake Bay at Calvert Cliffs in Maryland. The stratigraphic distribution of teeth within the cliffs has not yet been documented. We utilized museum collections of in situ teeth to access their distribution within stratigraphic beds and a large selection of float teeth retrieved from Calvert County beaches as a proxy for the distribution of teeth within stratigraphic beds and across underlying beaches. Museum collections provide 1,866 teeth recorded in situ; float collections yield a total of 24,409 teeth. These data sets offer different, but complementary, results. Miocene sediments along Calvert Cliffs comprise the Calvert, Choptank, and St. Marys formations. Over 96% of all teeth in the in situ data set derive from the Calvert Formation, likely due to favorable paleoenvironmental conditions for sharks. The non-uniform stratigraphic distribution of teeth is further supported by an uneven distribution of teeth collected on beaches below the cliffs. Samples from northern localities contained more float specimens; cliffs in this area are composed almost entirely of the Calvert Formation. Fifteen genera are represented in the in situ and float collections. The main constituents are Carcharhinus spp., Hemipristis serra, Galeocerdo spp., Isurus spp., and Carcharias spp. Most of these genera exhibit significant unidirectional trends in the proportional abundance of teeth across Calvert Cliffs beaches. Factors influencing these variations remain unclear, but the overall dominance of carcharhiniforms over lamniform and other sharks observed for the Miocene persists in modern nearshore environments. © 2010 by the Society of Vertebrate Paleontology.

Godfrey S.J.,Calvert Marine Museum | Smith J.B.,American Institutes for Research
Naturwissenschaften | Year: 2010

Coprolites (fossilized feces) preserve a wide range of biogenic components, from bacteria and spores to a variety of vertebrate tissues. Two coprolites from the Calvert Cliffs outcrop belt (Miocene-aged Chesapeake Group), MD, USA, preserve shark tooth impressions in the form of partial dental arcades. The specimens are the first known coprolites to preserve vertebrate tooth marks. They provide another example of trace fossils providing evidence of prehistoric animal behaviors that cannot be directly approached through the study of body fossils. Shark behaviors that could account for these impressions include: (1) aborted coprophagy, (2) benthic or nektonic exploration, or (3) predation. © Springer-Verlag 2010.

Godfrey S.J.,Calvert Marine Museum | Godfrey S.J.,Smithsonian Institution
Comptes Rendus - Palevol | Year: 2013

Most extant odontocetes appear to be anosmatic. However, some Miocene odontocetes, including a broken skull attributed to Squalodon sp. (Calvert Formation, Calvert Cliffs, Maryland, USA) preserve the osteological components associated with a well-developed sense of smell: dorsal nasal meatuses, ethmoturbinates within olfactory recesses, a perforate cribriform plate, and an olfactory bulb chamber. In Squalodon sp., the area within the olfactory recesses (i.e., covered in life by olfactory sensory epithelia) is 5367mm2 and the area occupied by the olfactory bulbs (i.e., the ethmoid area) is 769.8mm2. In most mammals, the area of the olfactory epithelium is typically circa 16 times larger than the ethmoid area. The area covered by olfactory epithelium in CMM-V-2287 is only about seven times larger than its ethmoid area, less than half the area in typical mammals. During the Miocene, most odontocetes variously lost the osteological proxies indicative of osmatic ability. Perhaps biosonar surpassed the efficiency of olfactory cues during predation and social/parental/sexual interactions rendering the latter redundant/obsolete in odontocete analysis of, and interactions with and within their aquatic environments. © 2013 Académie des sciences.

Godfrey S.J.,Calvert Marine Museum | Godfrey S.J.,Smithsonian Institution | Geisler J.,Smithsonian Institution | Geisler J.,York College | Fitzgerald E.M.,Smithsonian Institution
Anatomical Record | Year: 2013

The structure of the olfactory apparatus is not well known in both archaic and extant whales; the result of poor preservation in most fossils and locational isolation deep within the skulls in both fossil and Recent taxa. Several specimens now shed additional light on the subject. A partial skull of an archaic cetacean is reported from the Pamunkey River, Virginia, USA. The specimen probably derives from the upper middle Eocene (Piney Point Formation) and is tentatively assigned to the Protocetidae. Uncrushed cranial cavities associated with the olfactory apparatus were devoid of sediment. CT scans clearly reveal the dorsal nasal meatus, ethmoturbinates within the olfactory recess, the cribriform plate, the area occupied by the olfactory bulbs, and the olfactory nerve tract. Several sectioned skulls of the minke whale (Balaenoptera acutorostrata) were also examined, and olfactory structures are remarkably similar to those observed in the fossil skull from the Pamunkey River. One important difference between the two is that the fossil specimen has an elongate olfactory nerve tract. The more forward position of the external nares in extant balaenopterids when compared with those of extant odontocetes is interpreted to be the result of the need to retain a functional olfactory apparatus and the forward position of the supraoccipital/cranial vertex. An increase in the distance between the occipital condyles and the vertex in balaenopterids enhances the mechanical advantage of the epaxial musculature that inserts on the occiput, a specialization that likely stabilizes the head of these enormous mammals during lunge feeding. © 2012 Wiley Periodicals, Inc.

Geisler J.H.,York College | Godfrey S.J.,Calvert Marine Museum | Lambert O.,French Natural History Museum | Lambert O.,Institute Royal Des Science Naturelles Of Belgique
Journal of Vertebrate Paleontology | Year: 2012

A new genus and species of extinct inioid odontocete (Meherrinia isoni) is based on nine partial crania that probably originated from the late Miocene marine Eastover Formation in North Carolina, U.S.A. They were collected from the riverbed of the Meherrin River, a tributary of the Chowan River. Ossification of the mesethmoid and the tight interdigitation of many sutures indicate that these specimens represent mature individuals. Key characteristics of the new inioid include maxillae that squeeze the nasals into a slight hourglass shape and supraoccipital that is deeply wedged between the frontals and maxillae on the vertex. As compared to the extant iniid Inia geoffrensis (Amazon River dolphin) and the extant pontoporiid Pontoporia blainvillei (La Plata dolphin), Meherrinia is more plesiomorphic in having less elevated premaxillary eminences and supraorbital processes. In other respects Meherrinia is intermediate in morphology between the two extant genera of inioids. For example, the essentially symmetrical vertex is intermediate in height between the low and high vertices in Pontoporia blainvillei and Inia geoffrensis, respectively. A cladistic analysis of morphological and molecular data supports a sister-group relationship between Meherrinia and Inia; thus our new taxon is tentatively assigned to the Iniidae. If correct, this is the first iniid represented by diagnostic remains from marine deposits and just the second from North America. © 2012 Copyright Taylor and Francis Group, LLC.

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