Kenneth Carpenter

The Dinosaurs of the Niobrara Chalk Formation (Upper Cretaceous, Kansas)

ABSTRACT The dinosaurian fauna of the Niobrara Chalk Formation constitutes the best known assemblage from the middle Santonian-early Campanian interval of the Late Cretaceous of North America. The fauna consists of both hadrosaurid ornithopods and nodosaurid ankylosaurs. The nodosaurid specimens from the Smoky Hill Chalk Member of the Niobrara Chalk Formation include the holotype of Hierosaurus sternbergii (here regarded as nomen dubium), material of “Hierosaurus” coleii (herein designated the type species of the new genus Niobrarasaurus) and two specimens that may belong to N. coleii, but are better interpreted as Nodosauridae incertae sedis. Claosaurus agilis, the sole hadrosaurid from the Niobrara Chalk Formation, constitutes a poorly known, but distinct species having a basal relationship among remaining hadrosaurids.

The Goddard High Resolution Spectrograph: In-orbit performance

The in-orbit performance of the Goddard High Resolution Spectrograph onboard the Hubble Space Telescope (HST) is presented. This report covers the pre-COSTAR period, when instrument performance was limited by the effects of spherical aberration of the telescopes primary mirror. The digicon detectors provide a linear response to count rates spanning over six orders of magnitude, ranging from the normal background flux of 0.01 counts diode -1 s-1 to values larger than 104 counts diode-1 s-1. Scattered light from the first-order gratings is small and can be removed by standard background subtraction techniques. Scattered light in the echelle mode is more complex in origin, but it also can be accurately removed. Data have been obtained over a wavelength range from below 1100 A to 3300 A, at spectral resolutions as high as R = lambda/delta-lambda = 90,000. The wavelength scale is influenced by spectrograph temperature, outgassing of the optical bench, and interaction of the magnetic field within the detector with the earths magnetic field. Models of these effects lead to a default wavelength scale with an accuracy better than 1 diode, corresponding to 3 km s-1 in the echelle mode. With care, the wavelength scale can be determined to an accuracy of 0.2 diodes. Calibration of the instrument sensitivity functions is tied into the HST flux calibration through observations of spectrophotometric standard stars. The measurements of vignetting and the echelle blaze function provide relative photometric precision to about 5% or better. The effects of fixed-pattern noise have been investigated, and techniques have been devised for recognizing and removing it from the data. The ultimate signal-to-noise ratio achievable with the spectrograph is essentially limited only by counting statistics, and values approaching 1000:1 have been obtained.

The Goddard High Resolution Spectrograph: Instrument, goals, and science results

The Goddard High Resolution Spectrograph (GHRS), currently in Earth orbit on the Hubble Space Telescope (HST), operates in the wavelength range of 1150-3200A with spectral resolutions (lambda/delta-lambda) of approximately 2 X 103, 2 X 104, and 1 X 105. This paper describes the instrument and its development from inception, its current status, the approach to operations, representative results in the major areas of the scientific goals, and prospects for the future.

Forelimb biomechanics of nonavian theropod dinosaurs in predation

Theoretical models of theropod forelimb biomechanics are often tainted with preconceived ideas. Actualistic modeling using specimens and casts, coupled with CAT-scans and dissections of extant vertebrate forelimbs, demonstrates that forelimb motion in theropods is considerably less than hypothetical models indicate. The forelimbs ofCoelophysis, cf.Coelurus, Allosaurus, Deinonychus, andTyrannosaurus were investigated. Motion at the shoulder, elbow, wrist, and digits were analyzed and compared with those of birds and crocodiles, then motion of the entire forelimb was examined. The results have considerable implications for forelimb use in predation. Three models of predation are recognized: 1) long armed grasper —Deinonychus, cf.Coelurus; 2) clutcher -Tyrannosaurus; 3) combination grasper-clutcher -Allosaurus. Analysis of the joints ofDeinonychus show that the forelimb could not fold avian fashion. The scapula of the theropodUnenlagia was oriented incorrectly and differs little from the standard theropod scapula.

Different Growth Patterns between the Skeleton and Osteoderms of Stegosaurus (Ornithischia: Thyreophora)

ABSTRACT Stegosaurus has unique plate- and spike-shaped osteoderms. Previous studies have focused on the function of the osteoderms; however, ontogenetic development and maturity of these osteoderms with respect to Stegosaurus body growth are little known. In this study, the bone growth of both the skeleton and osteoderms was assessed using thin sections from small to large-sized individuals. In the small individual, the bone histology shows a fibro-lamellar tissue with a radial and/or reticular vascular network in both a body element and an osteoderm. In the medium-sized individual, the cortex shows a longitudinal vascular network and a few lines of arrested growth (LAG) in the skeleton, whereas the osteoderms still retain fibro-lamellar bone and show a reticular vascular network without LAGs. In large individuals, both body elements and osteoderms have fibro-lamellar tissue and multiple LAGs. However, bone tissues from body elements possess external fundamental systems (EFS) at their periphery, whereas osteoderms from the large individual lack EFS. Four histological stages are observed in both the skeleton and the osteoderms in the growth series of Stegosaurus sections: (1) a fibro-lamellar tissue with a radial and/or reticular vascular network, (2) fibro-lamellar tissue with a longitudinal vascular network, (3) with LAGs, and (4) with EFS. The timing of histological changes of osteoderms was delayed from those of the skeleton. This delay indicates that osteoderms might have maintained faster growth rates than the body elements after the maturity of the skeleton.

Skull of a Jurassic ankylosaur (Dinosauria)

The origin and early evolution of many major dinosaur groups are poorly known because specimens are rare. One of these groups, the Ankylosauria, or armour-plated dinosaurs, is best known from well-preserved specimens from the Upper Cretaceous period of Asia and North America. Here we describe a well-preserved skull of an earlier, Late Jurassic ankylosaur, which will be important in clarifying the early history of this group. The specimen, Gargoyleosaurus parkpini gen. et sp. nov., was collected from the Upper Jurassic Morrison Formation of Wyoming, USA. Despite its geological age, the skull shows features seen in Late Cretaceous ankylosaurs, including fusion of bone armour to the surface of the skull and mandible and closure of two skull openings, the antorbital and upper temporal fenestrae. The new taxon also has characters common to the two ankylosaur families, the Ankylosauridae and Nodosauridae, supporting the proposal that the Ankylosauria originated from a single ancestor. Nevertheless, specialized characters place Gargoyleosaurus as the most primitive, or basal, member of the Ankylosauridae.

Observing stellar coronae with the Goddard High Resolution Spectrograph. 1: The dMe star AU microscopoii

We report on an observation of AU Mic taken with the Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope. The data consist of a rapid sequence of spectra covering the wavelength range 1345-1375 A with a spectral resolution of 10,000. The observations were originally intended to search for spectral variations during flares. No flares were detected during the 3.5 hr of monitoring. A method of reducing the noise while combining the individual spectra in the time series is described which resulted in the elimination of half of the noise while rejecting only a small fraction of the stellar signal. The resultant spectrum was of sufficient quality to allow the detection of emission lines with an integrated flux of 10(exp -15) ergs/sq cm(sec) or greater. Lines of C I, O I, O V, Cl I, and Fe XXI were detected. This is the first indisputable detection of the 1354 A Fe XXI line, formed at T approximately = 10(exp 7) K, on a star other than the Sun. The line was well resolved and displayed no significant bulk motions or profile asymmetry. From the upper limit on the observed line width, we derive an upper limit of 38 km/s for the turbulent velocity in the 10(exp 7) K plasma. An upper limit is derived for the flux of the 1349 A Fe XII line, formed at T approximately = 1.3 x 10(exp 6) K. These data are combined with contemporaneous GHRS and International Ultraviolet Explorer (IUE) data to derive the volume emission measure distribution of AU Mic over the temperature range 10(exp 4)-10(exp 7) K. Models of coronal loops in hydrostatic equilibrium are consistent with the observed volume emission measures of the coronal lines. The fraction of the stellar surface covered by the footprints of the loops depends upon the loop length and is less than 14% for lengths smaller than the stellar radius. From the upper limit to the estimated width of the Fe XXI line prfile we find that the we cannot rule out Alfven wave dissipation as a possible contributor to the required quiescent loop heating rate.

Redescription of the holotype of Dryptosaurus aquilunguis (Dinosauria: Theropoda) from the Upper Cretaceous of New Jersey

ABSTRACT The skeleton of the enigmatic theropod Dryptosaurus aquilunguis is redescribed in light of the many new theropods named since Copes original description in 1866. Unfortunately, the fragmentary nature of the single known skeleton makes comparison with other theropods difficult. Historically, Dryptosaurus has been placed, at one time or another, in the theropod families Coeluridae, Deinodontidae, Megalosauridae, Tyrannosauridae, and its own family, Dryptosauridae. Most of these assignments have been based upon superficial resemblances to various members of those families. Reexamination of the specimen indicates the presence of unique serrations on the maxillary teeth, a large ungual/humeral ratio, the probable presence of a high, centrally located ascending process on the astragalus, and a non-arctometatarsal. These features indicate that Dryptosaurus is a unique theropod and should be placed in its own family, Dryptosauridae.

Evidence for a cool wind from the K2 dwarf in the detached binary V471 Tauri

Evidence for mass loss from the K2 dwarf in V471 Tauri is found in the form of discrete absorption features in lines of various elements (Mg, Fe, Cr, Mn) and ionization stages (Mg I, Mg II, Fe I, Fe II). Resonant Mg II absorption indicates a mass loss rate of at least 10 to the -11th solar masses per year. The wind appears to be cool (no more than a few times 10,000 K). 6 refs.

BRAINCASE OF AN EARLY CRETACEOUS TITANOSAURIFORM SAUROPOD FROM TEXAS

Abstract The first braincase belonging to an Early Cretaceous sauropod from North America is described. The diagnostic characters of this well preserved partial braincase are: prominent supraoccipital crest, with a distinct median ridge extending almost to the foramen magnum; short, ventrally directed basitubera, divided by a deep groove extending to the basipterygoid; single foramen for cranial nerve XII; accessory foramen for cranial nerve XI. A lack of juvenile characters suggests this specimen, although quite small, belongs to an adult individual. Comparison of this specimen with other sauropod crania indicates strong similarities with brachiosaurids and titanosaurids.