Petrosal bones of metatherian mammals from the Late Palaeocene of Itaboraí (Brazil), and a cladistic analysis of petrosal features in metatherians

Metatherian petrosal bones were recovered from the early Late Palaeocene Itaboraí, Brazil, and are formally described. A cladistic analysis of the distribution of 56 petrosal and basicranial characters among extant and fossil metatherians was conducted, resulting in seven parsimonious trees. Relationships among metatherian ingroup taxa are congruent with current understanding of metatherian phylogeny. Metatheria is diagnosed by eight petrosal synapomorphies: stapedial artery absent in adults; reduced, intramural prootic canal; extrabullar internal carotid artery; inferior petrosal sinus between petrosal, basisphenoid, and basioccipital; cava supracochleare and epiptericum completely separated; reduction of the lateral flange; reduction of the anterior lamina; separation of the jugular foramen from the opening for the inferior petrosal sinus. The Palaeocene taxa Mayulestes , Pucadelphy s, and Andinodelphys from Tiupampa, and Petrosal Type II from Itaboraí are the sister groups of all other South American and Australian metatherians. This analysis confirms previous results showing the South American 'monito del monte' Dromiciops nested within the Australasian radiation. Within this australidelphian clade, Dromiciops is closely related to the dasyurids. The South American Caenolestes appears more closely related to the Australidelphia than to the South American didelphids. The Petrosal Types I, III, IV and V from Itaboraí are the stem taxa of the clade Australidelphia plus Caenolestes . The significant synapomorphies supporting this relationship are: enlargement of the fossa subarcuata that produces a bulbous ventral aspect of the mastoid and loss of post-temporal canal.  Journal compilation © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society , 2007, 150 , 85–115. No claim to original French government works.     

Tumulduria incomperta and the case for Tommotian trilobites

The enigmatic fossil Tumulduria incomperta Missanhevsky 1969 from the basal Tommotian Stage at 'Dvortsy' on the Aldan River, Siberian Platform, is reinvestigated in light of the report (Fedorov et al. 1979, Dokl. AN SSSR 249) of trilobite remains from the same beds. Comparisons of these supposed trilobites with old and new collections from 'Dvortsy' leave no doubt that they are identical to Tumulduria incomperta. Tumulduria is represented by phosphatic plates with a crude bilateral symmetry, consisting of a central longitudinal rounded ridge flanked by flat lateral portions. They are built of growth lamellae overlapping each other along the axis of symmetry. The surface carries prominent transverse folds and lamellar terminations. There is considerable morphological variation, and the similarity of some specimens to trilobites is only superficial. Tumulduria is interpreted as a bilaterally symmetrical metazoan with a dorsal protective plate; it probably represents a short-lived group that left no descendants.     

松辽盆地白垩纪微体浮游植物群及其环境讨论

该文报道了松辽盆地白垩纪丰富的非海相微体浮游植物群,主要是沟鞭藻类及一些绿藻和疑源类;论述了藻类的生物地层特征,自下而上初步划分出10个组合带;结合微量元素和古地磁等资料,较详细地讨论了含微体浮游植物组段的沉积环境,认为松辽盆地在白垩纪至少遭受过两次重要的海侵(分别在青山口组一段及嫩江组一、二段沉积时期),导致古松辽湖泊五种不同水体环境的演替,指出微体浮游植物组合的变化是受古盐度、古温度和古水深等因素控制的。此外,对有关组段的地质时代也进行了讨论,进一步补充了新的浮游植物化石证据。     

Pattern of conodont reworking in the Upper Devonian of the Alps: palaeoenvironmental and palaeotectonic implications

Transfer of sediments from shallow shelf to basin usually implies vertical (stratigraphic) reworking of fossils, but in a few instances produces only lateral reworking (actually within the time span of a subzone). An Upper Devonian (Frasnian) pelagic carbonate sequence with allodapic intercalations and thick intraclast parabreccias triggered by seismic shocks and related tsunami and turbidity currents has been studied. Here, the standard biozone sequence is undisturbed at the zonal as well as the subzonal level. However, distribution of conodonts is discontinuous, and ranges of some important species are altered; mature specimens are commonly broken, whereas complete specimens are mostly juvenile forms. Maxima and minima of element frequency and anomalous thickening or thinning of subzones are recognized. Such distribution patterns of conodonts are compared with the four main facies distinguished and related to the environmental interpretation (a platform-basin system, the original gentle slope of which was fragmenting in fault-controlled blocks). The mean frequency of shallow-water, proximal conodonts is 10% whereas transitional to distal deeper-water genera dominate throughout the entire section. In the dominant biofacies, conodonts settled vertically, in the subordinate one they were transported laterally. The 'intraclast parabreccia' is interpreted as a peculiar type of seismitc. The anomalous thickness variation of biozones is related to the step topography of the slope in a fault-controlled carbonate basin.     

Paleobotanical studies inFagaceae of the European Tertiary

A systematic reassessment of megafossil records ofFagaceae in Central Europe has been undertaken on the basis of leaf cuticular characters. The oldest representatives date back to the Eocene:Quercus subhercynica spec. nova,Dryophyllum furcinerve (Rossm.)Schmalh.,Trigonobalanopsis rhamnoides (Rossm.) gen. & comb. nov. In the Oligocene other members of extant genera appear:Quercus rhenana (Weyl. & Kilpp.)Knobloch & Kvaek,Fagus attenuata Goepp.,Lithocarpus saxonicus spec. nova. In the Neogene these ancient taxa (except inFagus lineage), are gradually replaced by deciduous species ofQuercus andCastanea. Trigonobalanus andCastanopsis are recorded by fruits (or wood) only.     

Evolution of the Australian flora through the Tertiary

The evolution of the Australian flora through the Tertiary has not been reviewed by a megafossil palaeobotanist for almost a century. Based on material available and published studies, the Australian Tertiary can be considered in three units: Eocene, Oligo-Miocene, and Pliocene. Key taxa in the Eocene includeCasuarinaceae, Proteaceae, Fagaceae, Podocarpaceae, andLauraceae. Many known Eocene deposits are interpreted as warm, humid rainforests.Oligo-Miocene floras reflect a climatic deterioration, with greater occurrence of sclerophylly and xerophylly. A reduction of tropical taxa is seen with an increase ofMyrtaceae and earliest records ofMimosaceae, Chenopodiaceae, andPoaceae. These trends continue into the Pliocene, which is not well represented in Australia.Problems needing to be addressed include the discrepancy between the pollen and megafossil records ofNothofagus, the origins of Australia's wet tropical taxa, and the role of fire in the early evolution of the Australian flora.     

Speculations on carbon dioxide starvation, Late Tertiary evolution of stomatal regulation and floristic modernization

Ambient atmospheric CO₂ concentration ([CO₂]_a) has apparently declined from values above 200μmol mol⁻¹ to values below 200μmol mol⁻¹ within the last several million years. The lower end of this range is marginal for C₃ plants. I hypothesize that: (1) declining [CO₂]_a imposed a physiological strain on plants, and plant taxa evolving under declining [CO₂]_a tended to develop compensating mechanisms, including increased stomatal efficiency; (2) angiosperms were better able to adjust to declining [CO₂]_a than were gymnosperms and pteridophytes; and (3) angiosperm adjustment has been uneven. Fast-evolving taxa (e.g. grasses and herbs) have been better able to adapt to CO₂ starvation. If these propositions are true, stomatal adjustment mechanisms should show patterned variation, and a single pattern of stomatal regulation cannot be assumed.     

湖北南襄盆地枣阳凹陷第三纪轮藻化石及其地层意义

本文研究了南襄盆地枣阳凹陷第三系玉皇顶组到凤凰镇组轮藻化石。共划分出４个组合,其时代分别属早始新世、中始新世、晚始新世和渐新世。