| 1. |
- Bassett, MG, et al.
(författare)
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Organophosphatic brachiopods : Patterns of biodiversification and extinction in the early Palaeozoic
- 1999
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Ingår i: Geobios. - : Elsevier. - 0016-6995 .- 1777-5728. ; 32:2, s. 145-163
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Tidskriftsartikel (refereegranskat)abstract
- From a database of 226 Cambrian - Ordovician genera of organophosphatic-shelled brachiopods comprisingthe Subphylum Linguliformea, 11 sets of morphological characters typify all orders and superfamilies. Seven sets of these large-scale evolutionary novelties were established already by the end of the mid Cambrian, 2 more by the end of the late Cambrian, and the remaining 2 before the end of the Arenig. The earliest linguliformeans are of Tommotian age and represent some of the oldest known benthic organisms with a mineralised skeleton. Major diversification at the generic level took place during the mid and late Cambrian, by which time members of the Order Lingulida spread from near-shore to deep-water environments and became dominant in low diversity benthic assemblages that inhabited mobile sandy bottoms. There was a significant decline in diversity of linguliformeans during the latest Cambrian. Following recovery in the late Tremadoc-early Arenig, they then became one of the most distinctive components of benthic assemblages inhabiting marginal environments, e.g. eutrophic basins, shallow mobile sands, and abyssal depths. During the Llanvirn, there was a significant, worldwide turnover in linguliformean brachiopod faunas, when the majority of epibenthic lingulides of the families Obolidae, Zhanatellidae and Elkaniidae became extinct and were replaced, in shallow marine biofacies, by assemblages dominated by bivalved molluscs and burrowing lingulides. There is no trace until the mid Ashgill of a significant decline of micromorphic taxa in linguliformean assemblages characteristic of outer shelf environments. However, all siphonotretides, paterinides and most acrotretide genera disappeared towards the end of the late Ordovician pre-Hirnantian Dicellograptus anceps Biozone.
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| 2. |
- Bordiga, Manuela, et al.
(författare)
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Reticulofenestra daviesii : Biostratigraphy and paleogeographic distribution across the Eocene-Oligocene boundary
- 2017
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Ingår i: Geobios. - : Elsevier. - 0016-6995 .- 1777-5728. ; 50:5-6, s. 349-358
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Tidskriftsartikel (refereegranskat)abstract
- Improving the biostratigraphy across the Eocene-Oligocene is fundamental to better constrain the timing and causes of an important global climate change of the Cenozoic, the Eocene-Oligocene Transition (EOT; 34-33.5 Ma). Across the EOT, only few nannofossil bioevents are considered globally synchronous and reliable. One of these is the first common occurrence (Bc) of the species Reticulofenestra daviesii that has been proven to be useful for biostratigraphical correlations in the Southern Ocean, but the potential of R. daviesii as a biostratigraphical marker at mid- and low latitudes has not been explored yet in detail. We investigate three deep-sea drill sites located across a N-S transect at mid-low latitudes of the Atlantic Ocean spanning from 34.4 to 33 Ma, reviewing the temporal and geographical distribution together with the intraspecific variability of R. daviesii. Our data quantify the occurrence of R. daviesii in (sub)tropical regions of the Atlantic Ocean, although with lower abundances (similar to 4-12%) compared to Southern Ocean assemblages (40-95%). This suggests that R. daviesii was a cosmopolitan species capable to adapt to a wider range of sea surface temperatures and environmental conditions than previously thought. However, the temporal distributions of R. daviesii at the three studied sites are not comparable to the trends recorded in the Southern Ocean. Its Bc is clearly identifiable only at the equatorial site, occurring similar to 500,000 years before the age estimated in the Southern Ocean (33.705 Ma). Thus, we suggest caution when using the Bc of R. daviesii as a reliable biostratigraphical event at mid- and low latitudes. In addition, our biometrical data reveal that up to 38% of R. daviesii coccoliths is > 8-10 mu m in major axis size, thus bigger than the medium size range (5-8 mu m) originally described. Refining the size range of R. daviesii is important for estimating its cell volume versus surface area and coccolith carbonate mass. (C) 2017 Elsevier Masson SAS. All rights reserved.
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| 3. |
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| 4. |
- Doguzhaeva, Larisa, et al.
(författare)
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Connecting stripes: An organic skeletal structure in Sepia from Red Sea
- 2012
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Ingår i: Geobios. - : Elsevier BV. - 0016-6995 .- 1777-5728. ; 45, s. 13-17
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Tidskriftsartikel (refereegranskat)abstract
- The skeletal structure, herein termed ‘‘connecting stripes’’, is demonstrated in dried cuttlebones of Sepia (Acanthosepion) savignyi de Blainville from the Gulf of Aqaba, Red Sea, Eilat, Israel. This structure consists of segmented chitinous strip-like sheets covering the outside opening to the cuttlebone chambers. Scanning electron microscope images demonstrate that the connecting stripes are tightly attached to the neighbouring septa along the septal edges and do not continue from one chamber to the next. When broken, they leave band-like remnants along the attachment sites. The connecting stripes consist of fibrous, organic, possibly mainly chitinous, laminas. Chemical analysis using energy dispersive spectrometry shows that the connecting stripes contain C, O, Na, K but lack Ca and P. The connecting stripes show perceptible, usually barely visible micropores with diameter of ca. 0.1 mm; distances between the micropores are 0.2 to 0.3 mm. The connecting stripes in Sepia are similar to connecting rings in bactritoids and ammonoids in having a segmented structure and a non-mineralized, organic composition. The microporosity of connecting stripes observed in Sepia has been also recorded in three genera of Mesozoic ammonoids. The connecting stripes may serve as a transport route of the cameral liquid in and out of the chambers and are considered to be a homologue of the connecting rings in cephalopods with a fully developed siphonal tube.
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| 5. |
- Ebbestad, Jan Ove, 1967-, et al.
(författare)
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Ordovician (Caradoc) Gastropoda of the Katkoyeh Formation, Kerman Province, Iran
- 2008
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Ingår i: Geobios. - 0016-6995 .- 1777-5728. ; 41:5, s. 605-624
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Tidskriftsartikel (refereegranskat)abstract
- Seven taxa of gastropods are described from the Ordovician (Caradoc) upper Katkoyeh Formation of the Kerman region, east-central Iran.Three are named species and four are under open nomenclature. The most abundant is the minute bellerophontiform Tritonophon peeli Horny´,1977, indicative of a shallow water plectonotid community. Shell material is not preserved in this species, but a small, simple bulbous protoconch ispresent. Two new species are Slehoferia pachyta and Nonorios kleistos, both with prominent thick-shelled conchs. Shell repair is documented inboth of these forms, interpreted as a result of failed predation. Other micromorphic species occur in the samples, but only Tropidodiscus sp. andNonorios? sp. are named. The Kerman assemblage is comparable directly with similar, closely coeval faunas in Bohemia, France, Portugal,Morocco, and Italy, corresponding with the Palaeozoic Mediterranean Province of northern peri-Gondwana.
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| 6. |
- Ebbestad, Jan Ove R., 1967-, et al.
(författare)
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An unusual onychochilid mollusc from the Ordovician (Tremadocian) Fezouata Formation, Morocco
- 2015
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Ingår i: Geobios. - : Elsevier BV. - 0016-6995 .- 1777-5728. ; 48:6, s. 427-438
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Tidskriftsartikel (refereegranskat)abstract
- Pelecyogyra fezouataensis nov. gen., nov. sp. is described from the Lower Ordovician (Tremadocian, A. murrayi Biozone) Fezouata Formation at Oued Beni Zoli (locality Z-F5), in the central Anti-Atlas, Morocco. This is the first Onychochilidae Koken in Koken and Perner, 1925 reported from the Ordovician of Morocco. Its stratigraphical position bridges the gap between the late Cambrian and Middle to Upper Ordovician records. This new taxon draws together large specimens, reaching 27 mm in the greatest diameter, with 3 rapidly expanding whorls. All specimens are invariably preserved as dorsoventrally compressed moulds although preservation suggests that the degree of compaction was not great and that the species was generally low spired. A characteristic axe-shaped apertural lip and an ornamentation consisting of fine and dense lirae serve to distinguish the new genus from other onychochilids. The species appears to have been gregarious. In some specimens, small scalloped injuries are preserved along the apertural margins but these are not considered to reflect failed predation. Up to now, twenty-two species and eight genera of Ordovician onychochilids have been documented, being distributed in eight different terranes. The composition of the Onychochilidae is briefly reviewed and updated from the literature, to include Helicotis? Koken in Koken and Perner, 1925, Hyperstrophema Horný, 1964, Invertospira Horný, 1964, Kobayashiella Endo, 1937, Laeogyra Perner, 1903, Matherella Walcott, 1912, Matherellina Kobayashi, 1937, Onychochilus Lindström, 1884, Pelecyogyra nov. gen., Pervertina Horný, 1964, Scaevogyra Whitfield, 1878, Sinistracirsa Cossmann, 1908, Versispira Perner, 1903, and Voskopiella Frýda, 1992. Onychochilidae and Clisospiridae are placed in Mimospirida Dzik, 1983, regarding Hyperstrophina Linsley and Kier, 1984 as a junior synonym.
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| 7. |
- Ebbestad, Jan Ove R., 1967-, et al.
(författare)
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First occurrence of Pterotheca (Gastropoda) from the Silurian (Aeronian) of Spain
- 2017
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Ingår i: Geobios. - : Elsevier BV. - 0016-6995 .- 1777-5728. ; 50:2, s. 97-104
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Tidskriftsartikel (refereegranskat)abstract
- Pterotheca hispanica nov. sp. is described from the basal beds (Stimulograptus sedgwickii graptolite Zone) of the Formigoso Fm., in the Cantabrian Zone of the Iberian Massif, north-western Spain. This specialized bellerophontoid gastropod is for the first time recorded in the Silurian of peri-Gondwana; it is the only Aeronian species known so far. Its most closely allied relatives are from higher beds placed in the Telychian of Scotland. Pterotheca is considered a highly derived genus within the Pterothecinae of the Carinaropsidae, with the strongly reduced to absent coiling and the growth of the septum being synapomorphies. In the present work it is shown that not only the apical angle of the septum can be used to distinguish species, but also the relative length and width of the septum. In some cases, the slit may extend as far back as the anterior part of the internal septum. Silurian species were hitherto only found in marginal Laurentian and Eastern Avalonian settings. Pterotheca is absent from central Laurentia and Baltica, where it could be expected to be present based on its wide Ordovician distribution. In the light of this, the occurrence of the genus in the Aeronian of Spain seems difficult to explain, albeit the genus was present in peri-Gondwana prior to the end-Ordovician extinction. The extreme scarcity of described taxa recorded from Avalonia, Baltica and Iberia during the Early Silurian may explain this patchy distribution.
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| 8. |
- Ebbestad, Jan Ove R., 1967-, et al.
(författare)
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Pelecyogyra (Mollusca) from the Early Ordovician of the Montagne Noire, France
- 2020
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Ingår i: Geobios. - : Elsevier BV. - 0016-6995 .- 1777-5728. ; 63, s. 23-32
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Tidskriftsartikel (refereegranskat)abstract
- A new occurrence of the onychochilid mollusc Pelecyogyra is reported from the late Floian Landeyran Formation (Apatokephalus incisus Biozone) in the Montagne Noire, southern France, where it is associated with the two tergomyans Carcassonnella courtessolei and Thoralispira laevis, and a mollusc indet. With a low cap-shaped shell. The Montagne Noire specimens compare morphologically with Pelecyogyra fezouataensis from the late Tremadocian Fezouata Formation (Araneograptus murrayi Biozone) in Morocco and are tentatively referred to this species. Each occurrence of Pelecyogyra is from one or two localities only, but separated in time. They differ further in the deeper facies, association with Carcassonnella and Thoralispira, and non-gregarious occurrence in Montagne Noire compared to the shallower facies, lack of other molluscs and gregarious occurrence in the Fezouata Formation. In the Lower Ordovician, Pelecyogyra, Carcassonnella courtessolei, the rare C. vizcainoi and Thoralispira laevis are taxa that occur only in Montage Noire and the Anti-Atlas, while Lesueurilla prima also occurs in the Prague basin of the Czech Republic. Contrary to other faunal elements, like echinoderms and trilobites, these genera seem to have a wide environmental tolerance and are long ranging taxa. The main occurrence of the three key taxa Carcassonnella, Thoralispira and Lesueurilla in the Montagne Noire is in the lower part of the La Maurerie Formation (Taihungshania miqueli acme Zone), while the same taxa appear just slightly later in Morocco (?Cymatograptus protobalticus Biozone). Migration to the Anti-Atlas during the early Floian seems to have been possible during a period of general faunal exchange. Pelecyogyra may either have migrated from the Anti-Atlas to Montagne Noire during the same interval or possibly during the late Floian as indicated by shared faunal elements between these two regions at that time.
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| 9. |
- Georgalis, Georgios L., et al.
(författare)
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The fossil turtles of Greece : An overview of taxonomy and distribution
- 2013
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Ingår i: Geobios. - : Elsevier BV. - 0016-6995 .- 1777-5728. ; 46:4, s. 299-311
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Tidskriftsartikel (refereegranskat)abstract
- Turtle remains are common in the Miocene-Holocene deposits of Greece, and are a key focus of the growing research interest in Neogene. herpetofaunas from the Aegean region. Some of the most important finds include one of Europe's stratigraphically youngest pleurodiran taxa, Nostimochelone lampra, from the Early Miocene of Macedonia, together with arguably the richest record of fossil tortoises from the Eastern Mediterranean. This incorporates the presently oldest definitive representatives of the quintessential genus Testudo sensu stricto from the Late Miocene of Attica and Macedonia, and numerous specimens of the colossal (carapace similar to 2 m-length) testudinid Cheirogaster from Late Miocene-Late Pliocene sediments in southern and northern Greece, as well as on the eastern Aegean islands of Samos and Lesvos. Tantalising, but as yet unconfirmed Miocene accounts of the geoemydid Mauremys in Macedonia, and indeterminate emydid-like remains from Euboea, also provide potentially significant range extensions. Although hampered by a historically sparse documentation, the fossil turtles of Greece are a significant resource that record both assemblage changes and the origin of modern lineages.
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| 10. |
- Gubanov, Alexander P., et al.
(författare)
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Anabarella australis (Mollusca, Helcionelloida) from the Lower Cambrian of Greenland
- 2004
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Ingår i: Geobios. - : Elsevier BV. - 0016-6995 .- 1777-5728. ; 37:6, s. 719-724
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Tidskriftsartikel (refereegranskat)abstract
- The Early Cambrian helcionelloid mollusc Anabarella australis is described from North-East Greenland, representing the second occurrence of the species outside of Australia. Other Australian molluscs of this age are known from many localities including North China, Siberia, Altai, Transbaikalia, southern Kazakhstan, Mongolia, eastern Germany and Spain. These records, supported now by A. australis, demonstrate the close proximity of continents in the Early Cambrian.
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