A new species of Cretalamna sensu stricto (Lamniformes, Otodontidae) from the Late Cretaceous (Santonian-Campanian) of Alabama, USA

Decades of collecting from exposures of the Upper Cretaceous Tombigbee Sand Member of the Eutaw Formation and Mooreville Chalk in Alabama, USA has produced large numbers of isolated Cretalamna (sensu stricto) teeth. Many of these teeth had formerly been assigned to the extinct Late Cretaceous shark Cretalamna appendiculata (Agassiz, 1843), a taxon that is now considered largely restricted to the Turonian of Europe. Recent studies have shed light on the diversity of Late Cretaceous Cretalamna (s.s.) taxa, and here we recognize a new species from Alabama, Cretalamna bryanti. The teeth of C. bryanti sp. nov. appear aligned with the members of the Cretalamna borealis species group, but can be distinguished from these other species by a combination of the following: anterior teeth with a more pronounced and triangular lingual root protuberance, broader triangular cusp, and a taller root relative to the height of the crown; anteriorly situated lateroposterior teeth have a distally inclined or hooked main cusp and more than one pair of lateral cusplets; and lateroposterior teeth have a strong distally hooked main cusp and a root that is largely symmetrical in basal view. At present, C. bryanti sp. nov. is stratigraphically confined to the Santonian/Campanian Dicarinella asymetrica Sigal, 1952 and Globotruncanita elevata Brotzen, 1934 Planktonic Foraminiferal Zones within the Tombigbee Sand Member of the Eutaw Formation and Mooreville Chalk, and teeth have been collected from only four counties in central and western Alabama. The recognition of C. bryanti sp. nov. in Alabama adds to our knowledge on the diversity and distribution of Late Cretaceous otodontids in the region.

A new carnivorous cynodont (Synapsida, Therapsida) from the Brazilian Mid-dle Triassic (Santa Maria Formation): Candelariodon barberenai gen. et sp. nov.

A new small cynodont, Candelariodon barberenai gen. et sp. nov., from the Middle Triassic of Brazil (Santa Maria Formation) is reported. The new taxon is represented by a partial mandible having some complete teeth. The morphology of the dentary and splenial is similar to other carnivorous cynodonts, except for the absence of the angular process of the dentary. The anterior-most lower teeth are slightly expanded buccolingually with a tall and posteriorly curved main cusp and one or two accessory cusps. The posterior-most preserved lower postcanine, however, has lingual and buccal rows of cusps, each formed by four anteroposteriorly aligned cusps, separated by a shallow basin. This tooth resembles the posterior-most lower teeth of Aleodon Crompton 1955 from the Middle Triassic of Tanzania, but the anterior-most teeth of Candelariodon and Aleodon are essentially different. In this context, the phylogenetic relationships of the new taxon remain unclear until the discovery of more informative material.

New records of Staffia aenigmatica (Mammalia, Allotheria, Haramiyida) from the Upper Jurassic of Tendaguru in southeastern Tanzania, East Africa

Two non-multituberculate allotherian cheek teeth are described from the Upper Jurassic of Tendaguru in southeastern Tanzania, East Africa, Both specimens were collected from dinosaur-bearing matrix of bone bed Wj of the Middle Saurian Bed at Tendaguru Site dy by the German Tendaguru Expedition (1909&ndash;1913). Bone Bed Wj represents limnic to brackish deposits of Kimmeridgian-Tithonian age. The cheek teeth, considered as lower posterior molar and upper molar, represent a single taxon of the Haramiyida and are referred to <i>Staffia aenigmatica</i>, known only from the Upper Jurassic of Tendaguru. This assignment reinforces evidence for the palaeogeographic dispersal of haramiyids to Gondwana and the temporal persistence of these non-multituberculate allotherians into the Late Jurassic. Characters that distinguish <i>Staffia aenigmatica</i> from other haramiyids include the medial position of main cusp a1 at the front of the tooth crown and the presence of a large, anterolingual main notch between cusps a1 and a2 in lower cheek teeth, as well as the development of a strong anterolabial cingular ridge in the only known upper cheek tooth. <i>Staffia</i> shows the closest resemblance to <i>Thomasia</i> from the Late Triassic to Early Jurassic of Europe, although these genera are disdinctly different. Retention of the basic tooth crown pattern of haramiyids and traces of wear in the Tendaguru teeth suggest that the masticatory movements in <i>Staffia</i> were essentially restricted to a longitudinal direction, as in <i>Thomasia</i>. It is suggested that owing to its central position at the front of the tooth crown the lower main cusp a1 could have occluded in the central basin of the opposing upper molar during masticatory movements. <br><br> Aus dem Oberjura von Tendaguru in Tansania, Ostafrika, werden zwei Backenzähne eines Haramiyiden beschrieben. Beide Zähne stammen aus knochenführenden Gesteinsproben, die von der Deutschen Tendaguru Expedition (1909&ndash;1913) in der Fundstelle dy gesammelt wurden. Fundschicht der Haramiyiden-Zähne ist eine knochenführende Lage (Wj) der Mittleren Saurierschicht, die im Zeitraum Kimmeridge-Tithon in einem küstennahen Ablagerungsraum entstand. Beide Backenzähne, ein hinterer unterer Molar und ein oberer Molar, werden zu <i>Staffia aenigmatica</i> gestellt, die bisher nur aus dem Oberjura von Tendaguru bekannt ist. Beide Nachweise bestätigen erneut, daß Haramiaiden einst in Gondwana verbreitet waren und dort noch in der späten Jura-Zeit vorkamen. Merkmale, die <i>Staffia aenigmatica</i> von anderen Haramiyiden unterscheiden, sind die zentrale Position des a1-Höckers im Vorderabschnitt der Zahnkrone und die tiefe, breite anterolinguale Furche zwischen dem a1- und a2-Höcker der unteren Backenzähne sowie die starke labiale Cingulumleiste am einzigen bisher bekannten oberen Molaren. Zwischen <i>Staffia</i> aus dem Oberjura Ostafrikas und <i>Thomasia</i> aus der oberen Trias und dem unteren Jura Europas bestehen Gemeinsamkeiten, aber auch wesentliche Unterschiede. Die Beibehaltung des Backenzahn-Grundmusters der Haramiyiden und Abkauungsspuren an den Zähnen aus Tendaguru zeigen, daß die Kaubewegung bei <i>Staffia</i> im wesentlichen in longitudinaler Richtung erfolgte, wie bei <i>Thomasia</i>. Für Staffia wird vermutet, daß der a1-Haupthöcker auf Grund seiner zentralen Lage im vorderen Abschnitt der Zahnkrone in das zentrale Becken des entsprechenden oberen Backenzahnes paßte und dort bei der Zerkleinerung von Nahrungspartikeln mitwirkte. <br><br> doi:<a href="http://dx.doi.org/10.1002/mmng.20010040114" target="_blank">10.1002/mmng.20010040114</a>

ESR and EISCAT observations of the response of the cusp and cleft to IMF orientation changes

We report observations of the cusp/cleft ionosphere made on December 16th 1998 by the EISCAT (European incoherent scatter) VHF radar at Tromsø and the EISCAT Svalbard radar (ESR). We compare them with observations of the dayside auroral luminosity, as seen by meridian scanning photometers at Ny Ålesund and of HF radar backscatter, as observed by the CUTLASS radar. We study the response to an interval of about one hour when the interplanetary magnetic field (IMF), monitored by the WIND and ACE spacecraft, was southward. The cusp/cleft aurora is shown to correspond to a spatially extended region of elevated electron temperatures in the VHF radar data. Initial conditions were characterised by a northward-directed IMF and cusp/cleft aurora poleward of the ESR. A strong southward turning then occurred, causing an equatorward motion of the cusp/cleft aurora. Within the equatorward expanding, southward-IMF cusp/cleft, the ESR observed structured and elevated plasma densities and ion and electron temperatures. Cleft ion fountain upflows were seen in association with elevated ion temperatures and rapid eastward convection, consistent with the magnetic curvature force on newly opened field lines for the observed negative IMF By. Subsequently, the ESR beam remained immediately poleward of the main cusp/cleft and a sequence of poleward-moving auroral transients passed over it. After the last of these, the ESR was in the polar cap and the radar observations were characterised by extremely low ionospheric densities and downward field-aligned flows. The IMF then turned northward again and the auroral oval contracted such that the ESR moved back into the cusp/cleft region. For the poleward-retreating, northward-IMF cusp/cleft, the convection flows were slower, upflows were weaker and the electron density and temperature enhancements were less structured. Following the northward turning, the bands of high electron temperature and cusp/cleft aurora bifurcated, consistent with both subsolar and lobe reconnection taking place simultaneously. The present paper describes the large-scale behaviour of the ionosphere during this interval, as observed by a powerful combination of instruments. Two companion papers, by Lockwood et al. (2000) and Thorolfsson et al. (2000), both in this issue, describe the detailed behaviour of the poleward-moving transients observed during the interval of southward Bz, and explain their morphology in the context of previous theoretical work.Key words: Ionosphere (ionosphere - magnetosphere interactions; auroral ionosphere; plasma temperature and density)

Internal structure of Cambrian Conodonts

Based on material of the Upper Cambrian of Sweden the internal structure of proto-, para- and euconodonts has been investigated. The protoconodontidsGapparodusandGumellashow some special development of the median unit of the skeletal tissue. InGapparodus, long, parallel-running lamellae suggest a continuous growth, even of previously secreted lamellae, until their eventual outcropping. InGumellathe fibrous median layer decreases considerably during growth until its complete reduction, which coincides with the disappearance of the posterior wall. Paraconodonts also produced several specialities in their mode of growth. Elements with lateral processes such asProacodusandSerratocambriadeveloped by allometric growth. The lamellae are much more widely spaced in the process than in the main cusp to attain the required length of the former. InSerratocambriaadditional lamellae are inserted in the process. Thin sections of tricuspidate westergaardodinids reveal paraconodontid growth with lamellar remains in the tip of the median denticle, which are isolated from the growth lines in the lateral denticles. Based on this observation a hypothetical growth model explains the lamellar development as a result of stress and strain. The Ordovician euconodontidChosonodinaclearly shows white matter and is thus unrelated, but homeomorphic toWestergaardodina. Cambropustulafrom the lower Upper Cambrian is the oldest euconodont yet but it lacks white matter. The latter was an evolutionary novelty, which progressively developed in the euconodont line.The systematic position of conodonts is briefly discussed; the studied material cannot contribute to the hypothesis of neural crest derived skeletal tissue.

Upper premolar configuration of Didelphodon vorax (Mammalia, Marsupialia, Stagodontidae)

Stagodontid marsupials were a common component of late Mesozoic vertebrate faunas of the Western Interior of North America and were among the largest mammals that coexisted with Late Cretaceous dinosaurs. Two genera have been described, Didelphodon and Eodelphis; three if Pariadens (?Stagodontidae) from the Cenomanian of Utah (Cifelli and Eaton, 1987) is included. The dental arcade of stagodontids is notable for the presence of bulbous premolars, each with a massive main cusp and a large accessory lobe. The most complete stagodontid material consists of a maxillary fragment and a few nearly complete dentaries referred to Didelphodon (see Clemens, 1968, 1973; Fox and Naylor, 1986). However, the configuration of the anterior upper dentition of Didelphodon and other stagodontids is uncertain because of the lack of specimens preserving this portion of the skull. Thus, based on isolated teeth, upper premolars of Didelphodon have been interpreted to have been oriented with their accessory lobes either on their labial (Clemens, 1966) or lingual (Clemens, 1968; Lillegraven, 1969; Archibald, 1982; Fox and Naylor, 1986) sides.