Geologisk Tidsskrift • 1999/2
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Stratigrafisk korrelation af øvre karbone (Moscov) miosporer fra Kap Jungersen, Amdrup Land, det østlige NordgrønlandThomsen, C.: Stratigrafisk korrelation af øvre karbone (Moscov) miosporer fra Kap Jungersen, Amdrup Land, det østlige Nordgrønland. Geologisk Tidsskrift, hæfte 2, pp. 7- 1 8 . København, 1999-09-27.
Abstract: The 350 meter thick sedimentary succesion at Kap Jungersen, southem Amdrup Land, eastem NOlth Greenland, is dominated by marine shallow water carbonates with minor evaporites and siliciclastics. The age of the succesion is dated to Kashirskian and Podolskian in the Moscovian epoch by correlation of fusulinids to the Russian fusulinid stratigraphy.
33 productive palyno samples were collected and 48 miospore species have been identified and described (Thomsen et al. manus.). 21 of these species are new and described for the first time. Few scolecodonts and no acritarchs have been observed. The miospore assemblage is dominated by saccate striate and non striate pollen. Vitta tina is common.
The composition of the miospore assemblage indicates affinity to the nothem subtropicaI and arid Tianural floral province by similarity to other miospore assemblages in nothem Canada, the Urals and China. Age determination by comparison of the miospore assemblage to the West European miospore zonation indicates an age coresponding to Gzelian - Asselian, which is approximately 1 7 m.y. younger than the age determinated by the cooccouring fusulinids. This age discrepancy is best explained by floral provincialism resulting from differences in aridity between the humid tropicai Euramerica and the arid subtropicai Tianural futher north.
Adresse: Christian Thomsen, Enator A/S, Vesterbrogade 149, DK-1620 København V [cth@enator.dk]
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Hadrosauride dinosuarers forben: funktionel morfologi og systematikRasmussen, M.E.: Hadrosauride dinosaurers forben; funktionel morfologi og systematik.Geologisk Tidsskrift, hæfte 2, pp. 1 9-23. København, 1999-09-27.
Abstract: Hadrosaurs (Ornithischia, Ornithopoda, Hadrosauridae), Late Cretaceous "duckbilled" dinosaurs, are often reconstructed with incorreetly articulated forelimbs. The palm of the manus is generally reconstructed facing backwards, but the morphology dictates a more medial orientation. This is supported by the orientation of manus prints from quadrupedal trackways of hadrosaurs. The position of manus prints of quadrupedal trackways furthermore suggests that lateral oscillations of the body occurred, when the animal was walking.
A cladistic analysis, based on 92 morphological characters from the forelimbs of 18 hadrosaur species (representing 1 3 genera), eight other ornithopods and the Early Jurrasic ornithischian Heterodontosaurus, resulted in one single, most parsimonious tree. This tree is similar to other published phylogenies, and the family Hadrosauridae, as well as the two subfamilies Hadrosaurinae and Lambeosaurinae, are well defined, as is the group including hadrosaurs and the Early Cretaceous Iguanodon and Ouranosaurus (family Iguanodontidae).
The evolutionary trend of the ornithopod forelimb is traced. The early ornithopods, such as Heterodontosaurus were bipedal, while the forelimb of the intermediate-sized ornithopods was adapted for mass support. In the larger ornithopods, like hadrosaurs and iguanodonts, the forelimbs served several functions, and there are a clear functional division ofthe digits. Mass-support was the main function of the tree middle digits, the fifth digit could be used for manipulation, and perhaps the first digit of the iguanodonts served for defence or display.
Adresse: Mette Elstrup Rasmussen, Geologisk Museum, Københavns Universitet, Øster Voldgade 5- 7, 1350 København K.
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Udforskning af Thylacocephala - en mærkelig gruppe af leddyr
Steeman, F.A .: Udforskningen af Thylacocephala - en mærkelig g ruppe af leddyr. Geologisk Tidsskrift, hæfte 2, pp. 24-28. København, 1999-09-27.
Sammendrag: Thylacocephala er en klasse af leddyr (Arthropoda), der formodentlig har tilknytning til krebsdyrene (Crustacea). Thylacocephala blev først opdaget i starten af 1980' erne af tre uafhængige forskergrupper. Klassen Thylacocephala blev etableret i 1985 . De andre navne som var foreslået for denne gruppe, Concavicarida og Conchyliocarida, blev henført til ordner indenfor klassen.
Senere er en lang række af nye arter blevet beskrevet. I mange tilfælde har fejlidentificerede fossiler vist sig at tilhøre denne gruppe, hvilket formodentlig også gælder et antal uidentificerede fossile leddyr. Thylacocephalerne optræder fra Silur til Sen Kridt. De har et skjold, der dækker hele kroppen, og som har en indskæring fortil. Ventralt findes tre par store gribelemmer og postero-ventralt er der et antal små, trådformede lemmer. I den forreste indskæring findes en stor, afrundet struktur, som de fleste har tolket som et sammensat øje. Der er dog nogle der betragter denne struktur som en hovedsæk dækket af mikroskæl. Ifølge den førstnævnte tolkning, som nu støttes af de fleste data, var thylacocephaler aktive rovdyr. Nøglekarakterer for identifikation af thylacocephaler gives .
Adresse: Fedor A . Steeman, Grønnegården 332, 2670 Greve [fsteeman@dds.nl]
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