Microstructure de CladochonusMcCoy, 1847(Tabulata,Carbonifère)

The microstructure of two species of Cladochonusfrom Algerian Carboniferous, C. crassus (McCoy) and C. cf. tenuicollisMcCoy, has been studied by ultra-thin sections. Their walls consist of: 1. an external fibrous layer, 2. a median layer of undulating lamellae, 3. an internal zone of slender, elongated elements to which the name of «grundulae is given here. New data bring complements to the generic diagnosis of Cladochonus s. str. Some Permian cladochonid forms show different microstructures and should, therefore, be shifted to new generic units.     

Upper Cenomanian bivalves from the Guir Basin (southwestern Algeria): Order Veneroida

The Upper Cretaceous rocks are widely distributed and well exposed in south Algeria and consist in beds rich in macrofauna. For the first time, twenty veneroid species (Bivalvia) are systematically described from the upper Cenomanian deposits of the Guir Basin. While three species were reported since long before [Granocardium desvauxi (Coquand), G. productum (J. de C. Sowerby) and Glossus aquilinus (Coquand)]; Lucina fallax Forbes, Crassatella (Rochella) tenuicostata (Seguenza), Protocardia hillana (J. Sowerby), G. productum (J. de C. Sowerby) var. byzacenica (Pervinquière), Arctica cordata (Sharpe), A. humei (Cox), A. inornata (d’Orbigny), A. picteti (Coquand), Tenea delettrei (Coquand), Paraesa faba (J. de C. Sowerby), Meretrix desvauxi (Coquand) were previously unknown from the Cretaceous of Algerian Sahara. Because of reduced degree of preservation, Sphaera cf. corrugata J. Sowerby, Maghrebella cf. forgemoli (Coquand), Maghrebella sp., Granocardium cf. carolinum (d’Orbigny), Protocardia sp. and Meretrix sp. are tentatively determined. The studied material, found in the lower part of the “Calcaires de Sidi Mohamed Ben Bouziane” Formation, evidences palaeobiogeographic affinities occurring over a wide geographical area: from North Africa, southern Europe to Middle East and India. The present study provides new information to the knowledge of the upper Cenomanian palaeobiology of the studied region.     

Implications paléobiogéographiques de la découverted'une nouvelle localité éocène à vertébrés continentaux en afrique nord-occidentale: El Kohol (Sud-Oranais,Algérie)

The new fossil locality of El Kohol is located on the southern flank of the Saharan Altas, near Brezina (Algeria). It has been discovered in a thick Palaeogene continental series divided into 4 members: a transitional gypsiferous member, a lower red detritic member, a middle marly-calcareous member, and an upper red detritic member. The new flora and fauna have been obtained by excavation and washing-screening of a marly level of the middle member. The main finds are charophytes, lower vertebrates, a marsupial and eutherian mammals (lipotyphlan Insectivora, hyracoids, creodonts and Proboscidea). Geological and palaeontological data allow to refer these fossil remains, at least provisorily, to the end of the early Eocene. Palaeobiogeographical comments are made about forms with Holarctic affinities.     

Roveacrinids (Crinoidea,Roveacrinida) from the Cenomanian-Turonian of southwest Algeria (Saharan Atlas and Guir Basin)

In the southwestern part of Algeria, the Cenomanian-Turonian marine deposits build up a prominent ledge in a perched syncline (Ksour Mountains, western Saharan Atlas) or at high radius of curvature (Guir Basin). The petrographical analysis of the Cenomanian-Turonian deposits of the Ksour Mountains and of the Guir Basin reveals unexpected assemblages of roveacrinoidal ossicles comparable with those formerly reported from the Tinrhert area. For the first time, isolated ossicles of genuine and undisputable Roveacrinidae are illustrated. Three sections, Djebel Rhoundjaia (western Saharan Atlas), Berridel and Kénadsa (Guir Basin), were scrutinized to recognize the microcrinoidal sections within the carbonate microfacies and to compile the successive occurrence of respective roveacrinid taxa (besides the classical search for standard index microfossils) in an attempt to pinpoint more precisely the position of the Cenomanian-Turonian boundary (C/T B). These assemblages are particularly morphologically and taxonomically diverse with three species of genus Roveacrinus and one of genus Orthogonocrinus. The presence of Saccocomidae (Applinocrinus) is especially unusual in such stratigraphic levels. The relative abundance and diversity of Roveacrinidae evidence a peak when approaching the C/T B. Such an event is recurring in the latest Cenomanian in various Tethyan and Atlantic areas. These fluctuations are consistent with a high surface-water productivity just before the C/T B.     

Variabilité dentaire et crânienne de Numidotherium koholense (Mammalia, Proboscidea) de l’Éocène d’El Kohol, Algérie

The variability of one of the oldest known proboscideans, Numidotherium koholense from the Lower Eocene of El Kohol, Algeria, is here examined. The biometrical study of the jugal teeth shows that the population is homogeneous and corresponds to a single species. The important variations of the skull's shape are interpreted as resulting from sexual dimorphism. The dental variability is analysed and discussed from an evolutionary perspective regarding the adaptative radiation of the proboscidean order at the beginning of the Tertiary.     

Effet du stress salin sur la germination et la croissance in vitro du pistachier (Pistacia vera L.)

In order to study the salinity tolerance of pistachio (Pistacia vera L.), embryos developed from mature seeds were isolated and cultured in vitro and subjected to different NaCl concentrations (0, 42.8, 85.5, 171.1 and 256.6 mM) for 30 days. The results showed that in vitro germination of embryonic axes was not affected by the salt concentration. However, the germinated embryo survival rates decreased from 100% for the control to 62.9% for the highest salt concentration (256.6 mM).In addition, the plantlet growth (length of aerial and root parts, number of leaf produced per embryo, as well as the production of total fresh and dry matter for both aerial parts and roots) showed significant differences according the various salt concentrations. To cite this article: B. Benmahioul et al., C. R. Biologies 332 (2009).     

Le passage Cénomanien–Turonien dans le Nord-Ouest algérien (coupe de Douar Menkouchi,Ouarsenis) : biostratigraphie des radiolaires

The Ouarsenis Massif belongs to the Algerian Tell domain which is considered as the eastern part of the Maghrebian Tethys former margin. The Cenomanian-Turonian Douar Menkouchi section outcropping in the eastern side of the Ouarsenis massif is composed of marls and laminated limestone alternations, including massive limestone and a biosiliceous bed toward the upper part of the succession. It reveals the presence of well-preserved and diversified radiolarians. In this study, we have identified for the first time in the Algerian domain, age-diagnostic radiolarian assemblages characterizing the Cenomanian-Turonian transition (C/T). The organic-rich laminated beds (black shales) confined to Silvae Zone, Cenomanian in age and underlying a biosiliceous interval, have provided radiolarian assemblages dominated by Pseudodictyomitrae. The successions overlying the biosiliceous interval have provided diversified radiolarian assemblages including Hagiastridae (i,e. Crucella cachensis, Alievium cf. superbum) and abundant Dictymitrae taxa (i,e. Dictyomitra cf. napaensis and Dictyomitra undata) indicating early Turonian age. These marl-limestone alternations are assigned to the Alievium superbum Zone. Considering taphonomic and diagenetic implications on assemblages content, we conclude that organic-rich beds and biosiliceous interval outline the latest Cenomanian. The radiolarian assemblage composition exhibits similarities to microfauna recovered from Bonarelli Horizon in Central Italy. Morphological similarities are also deduced from assemblages containing Pseudodictyomitrae tiara morphotypes (synonym of P. nakasekoi) which resemble those recovered from ophiolitic intervals in Cyprus and Oman areas.     

Triassic Conifers as the basis for stratigraphical correlation

Floras with abundant Conifers have been recentlydiscovered in Siberia and China. They are correlated with the floras of the Voltzia sandstones of Western Europe.     

Découverte de faunes d'Ammonites de la zone à Platynota(Kimméridgien inférieur) dans les Monts de Chellala (avant-pays Tellien,Algérie); Conséquences stratigraphiques et paléogéographiques

In Chellala mountains (Seba el Abiod), in Western Algeria, new biostratigraphic data, based on Ammonites, allow characterize, for the first time in North Africa, the Platynota zone with the species-index Sutneria platynota. This species was known, to the present time, only in the South European border. These new biostratigraphic data show the diachronism of flyschoid facies. They do not exceed middle Oxfordian in the Tlemcenian zone; on the contrary they go up to lower Kimmeridgian in the preatlasic zone.     

Cupressus dupreziana A. Camus: distribution,decline and regeneration on the Tassili n'Ajjer,central Sahara

As soon as it was first discovered in 1924, on the heights of the Tassili n'Ajjer, Cupressus dupreziana (A. Camus) was declared an endangered species. The few ancient trees to be seen in the beds of wadis gave reason to suppose that they were isolated individuals left behind from a forest that had flourished in a damper climate. Attempts at a census of the trees were made on a number of occasions, the fullest, in 1972, reporting a total of 230 living specimens. The revision of this inventory between 1997 and 2001 has now enabled us to draw the boundaries of the present range of this species, to assess its rate of decline over the last three decades and, for the first time, to record some regeneration, with the presence of new, young trees.