Barbara S. Grandstaff

REE Signatures in Vertebrate Fossils from Sewell, NJ: Implications for Location of the K-T Boundary

Abstract Rare Earth Element (REE) signatures have been used to test whether mosasaur bones in a basal Hornerstown Formation bonebed (the Main Fossiliferous Layer, or MFL) in New Jersey were reworked from the underlying Maastrichtian beds or deposited synchronously with the bones of other taxa in the Hornerstown Formation. The interpreted age of the bonebed (Maastrichtian vs. Danian) and the position of the K-T boundary in New Jersey are affected by the possible reworking. Statistical techniques, such as ANOVA and Discriminant Analysis, show that signatures of REE in MFL bones are different from those of bones in either the underlying Navesink Formation or the upper part of the Hornerstown Formation, suggesting a unique depositional setting for this bonebed. REE signatures of the MFL mosasaur bones conform with signatures in bones from other taxa within the MFL, suggesting that their deposition was contemporaneous with that of the other taxa. Thus, the MFL bonebed appears to be Cretaceous in age and the K-T boundary must be in or above the MFL, within the Hornerstown Formation.

A New Species of Borealosuchus (Crocodyliformes, Eusuchia) from the Late Cretaceous—Early Paleogene of New Jersey

ABSTRACT A lower jaw and associated postcranial remains from the Late Cretaceous—early Paleocene Hornerstown Formation of New Jersey form the basis of a new crocodyliform species, Borealosuchus threeensis. Although one of the oldest known species of Borealosuchus, phylogenetic analysis supports a closer relationship to Borealosuchus from the early Eocene than with other Late Cretaceous or early Paleocene forms. This is based on the shared presence of a short mandibular symphysis excluding the splenial, a small external mandibular fenestra, and ventral osteoderms composed of two sutured ossifications. It is also similar to Borealosuchus material from the Paleocene of western Texas, though conspecificity cannot be demonstrated at present. A close relationship with the basal alligatoroids Leidyosuchus or Diplocynodontinae is not supported. The distribution of lower jaws with very small slit-like external mandibular fenestrae, or no fenestrae at all, among basal crocodylian lineages (including Borealosuchus) and close crocodylian relatives suggests the fenestrae may have been ancestrally absent in Crocodylia and regained two or more times. Current phylogenetic hypotheses are consistent with dispersal of more-derived species of Borealosuchus to the Western Interior during the Paleocene, and they indicate the presence of several unsampled lineages crossing the Cretaceous-Paleogene boundary.

Jaw Mechanics in Basal Ceratopsia (Ornithischia, Dinosauria)

Ceratopsian dinosaurs were a dominant group of herbivores in Cretaceous terrestrial ecosystems. We hypothesize that an understanding of the feeding system will provide important insight into the evolutionary success of these animals. The mandibular mechanics of eight genera of basal ceratopsians was examined to understand the variability in shape of the jaws and the early evolution of the masticatory system in Ceratopsia. Data were collected on lever arms, cranial angles and tooth row lengths. The results indicate that psittacosaurids had higher leverage at the beak and in the rostral part of the tooth row than basal neoceratopsians, but lower leverage in the caudal part of the tooth row. Although the vertebrate mandible is generally considered as a third‐class lever, that of basal neoceratopsians acted as a second‐class lever at the caudal part of the tooth row, as is also true in ceratopsids. When total input force from the mandibular adductor muscles on both sides of the skull is considered, the largest bite force in basal ceratopsian tooth rows was exerted in the caudal part of the tooth row at the caudal extremity of the zone with near‐maximum input force. Medially positioned teeth generate higher leverage than laterally positioned teeth. The largest bite force in all basal ceratopsians is smaller than the maximum input force, a limit imposed by the morphology of the basal ceratopsian masticatory system. In ceratopsids, caudal extension of the tooth row resulted in a much larger bite force, even exceeding the maximum input force. Anat Rec, 292:1352–1369, 2009.

BAWITIUS, GEN. NOV., A GIANT POLYPTERID (OSTEICHTHYES, ACTINOPTERYGII) FROM THE UPPER CRETACEOUS BAHARIYA FORMATION OF EGYPT

ABSTRACT A newly discovered osteichthyan ectopterygoid from the Upper Cretaceous (lower Cenomanian) Bahariya Formation of the Bahariya Oasis, Egypt, is nearly identical to the holotypic specimen of Polypterus? bartheli from the same area and geologic unit. The Bahariya ectopterygoids are referable to Polypteridae based on the presence of a robust, laterally directed process that articulates with the maxilla. Additionally, ganoid scales from the Bahariya Formation have an isopedine layer, a histological character of Polypteriformes; but differ from those of previously described members of this clade in having a discontinuous ganoin layer, rectilinear shape, and proportionally small articular processes. Both the ectopterygoids and the scales are unusually large, and are the only polypteriform remains so far identified from the Bahariya Formation. The ectopterygoids and (tentatively) the scales are herein assigned to a single species of gigantic polypterid, the morphology of which is sufficiently distinctive to warrant its placement in a new genus, Bawitius, gen. nov. Differences in scale anatomy and the enormous disparity in body size between Bawitius and Serenoichthys support the hypothesis (originally proposed on the basis of varied fin spine morphologies) that a diversity of polypterid fishes inhabited North Africa during the early Late Cretaceous.

Geographic and stratigraphic distribution of the Late Cretaceous suspension-feeding bony fish Bonnerichthys gladius (Teleostei, Pachycormiformes)

ABSTRACT The stratigraphic and paleogeographic distribution of the suspension-feeding pachycormiform fish Bonnerichthys is reviewed. Fossils attributable to this genus are known from the Western Interior Seaway (Niobrara Formation of Kansas, Sharon Springs Formation of Kansas, Nebraska, and North Dakota, DeGrey Formation of South Dakota, and possibly Mobridge Formation of Nebraska), the Eastern (Eutaw Formation of Mississippi and Mooreville and Demopolis formations of Alabama and Mississippi) and Western (Ozan Formation of Texas and Marlbrook Marl Formation of Arkansas) Gulf Coastal Plain, the Atlantic Coastal Plain (Wenonah Formation of New Jersey and possibly Marshalltown Formation of Delaware), and Pacific coast (Moreno Formation of California). Chronologically, occurrences of Bonnerichthys range in age from Coniacian to Maastrichtian. Fossils of Bonnerichthys from the Atlantic Coastal Plain, Eastern and Western Gulf Coastal Plain, and Pacific coast are definitively identified and figured here for the first time. Candidate deposits outside the United States that might yield Bonnerichthys are reviewed.

MICROSTRUCTURE OF POLYPTERID SCALES (OSTEICHTHYES: ACTINOPTERYGII: POLYPTERIDAE) FROM THE UPPER CRETACEOUS BAHARIYA FORMATION, BAHARIYA OASIS, EGYPT

Abstract Histology of newly discovered ganoid scales from the lower Bahariya Formation, in the Bahariya Oasis of western Egypt, confirms the presence of polypterid osteichthyans in this early Cenomanian locality. These fossils, occurring in the ∼97 million-year-old lower Bahariya sequences, are among the earliest known polypterids. The Bahariya scales exhibit four tissues: ganoin, dentine, isopedine (elasmodin), and a basal plate of cellular bone, confirming their inclusion within the Polypteriformes. They have a discontinuous ganoin layer, present only as highly variable ridges and bosses. Dentine along the edges of the ganoin ridges appears to have undergone active remodeling, suggesting that the ganoin ridges represent the remnants of a continuous ganoin cover. Modern polypterids inhabit exclusively freshwater environments. Polypterids are not rare in the lower Bahariya Formation. Their presence in these coastal sediments suggests that freshwater habitats lay close to the site of deposition of this sequence during the early Cenomanian.

A juvenile Mastodon skull from Monmouth County, New Jersey

ABSTRACT. We report on the partial skull of a small juvenile Mammut americanum Kerr from the Monmouth brooks area of New Jersey. Most Pleistocene mammal specimens from the brooks occur as disarticulated fragments. This specimen, the left side of a skull, includes portions of the premaxillae, maxillae, nasals, lacrimals, frontals, and four teeth: three sequential deciduous premolars and the permanent tusk. The skull bones are loosely articulated and essentially unfused, and the reconstructed skull shows gaps representing unossified growth zones between bones. The two anterior left deciduous teeth (DP2 and DP3) are much worn and very fragile, while the posterior left deciduous tooth (DP4) is essentially unworn. The crypt for the left first molar (M1) is partially preserved. The interior of the braincase is characterized by shallow pitting; it is neither smooth nor does it show molding against gyri and sulci of the brain. The pits are not characteristic of the inner surface of a normal mammalian skull, and appear to represent lytic lesions due to a disease process. Radiocarbon dating of the skull yielded an age of 11,680 ± 30 years.