Natural History Museum Basel

Basel, Switzerland

Natural History Museum Basel

Basel, Switzerland
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Mary Y.,Natural History Museum Basel | Mary Y.,University of Basel | Knappertsbusch M.W.,Natural History Museum Basel | Knappertsbusch M.W.,University of Basel
Marine Micropaleontology | Year: 2013

The morphological variation of the planktonic foraminifera plexus of Globorotalia (Menardella) (Bandy, 1972) has been studied in a Pliocene time-slice at 3.2. Ma. Using a combination of size, linear shell measurements and shape analysis, an extended morphological protocol is explored in order to define morphological subgroups within the Menardella subgenus (Bandy, 1972). Isochronous samples at 3.2. Ma have been selected at five ODP/IODP Sites in the low latitude Atlantic Ocean, in which up to 600 specimens per sample have been oriented, imaged and analyzed using a new automated prototype for morphological analysis called AMOR. Multimodal size frequency distribution is related to the occurrence of several distinct populations. Three main ubiquitous populations of such menardellids are isolated, next to two additional biogeographically limited subgroups. These populations strongly differ in abundance and size. Using morphological classifiers, subpopulations are distinguished among these populations, leading to the establishment of seven different morphotypes informally named: MA, MB, MC1, MC2, MC3, SH1 and SH2. These morphotypes are assigned to formal species, i.e., MA corresponds to Globorotalia (Menardella) menardii, MB to G. (M.) limbata, SH1 to G. (M.) exilis, and SH2 to G. (M.) pertenuis. In contrast, the species G. (M.) multicamerata is interpreted as being composed of three distinct morphotypes, sharing a similar size range, but differing in shell morphology.Morphotype MC1 shows thin and elongated chambers, whereas morphotype MC2 is characterized by a thick and robust test. MC3 is inflated with a distinct flexure in the final chamber. Size differences are linked to variations in habitat temperature and oxygenation, with the exception of G. (M.) multicamerata morphotypes, which are probably adapted to a productivity gradient. © 2013 Elsevier B.V.

Knappertsbusch M.W.,Natural History Museum Basel | Mary Y.,Natural History Museum Basel
Palaeontologia Electronica | Year: 2012

A technique is explored to visualize series of bivariate morphometric measurements of microfossil shells through geological time with the help of 3D-animated volume-density distributions. Visualization tests were performed using two existing and published sets of morphometric data, i.e., the Neogene coccolithophorid group Calcid-iscus leptoporus-Calcidiscus macintyrei and the planktonic foraminifera plexus of Glo-borotalia menardii. The technique converts series of downcore bivariate morphometric shell data into a continuous frequency distribution, which can be investigated with the help of a graphical data mining tool called Voxler from Golden Software. This tool allowed us to compose and animate complex subsurface structures raised from mor-phometric measurements of microfossils, and so provides an intuitive, comprehensive insight into the structure and dynamics of complicated evolutionary patterns. With upcoming future large morphometric data sets for oceanic microfossils, this instructive illustration method may hopefully serve to raise more interest in studying topics like morphological evolution, speciation and advances to achieve more universial species concepts needed so strongly in paleontology. An important conclusion from the experiments is that the structure of size frequency distribution through time shows a stronger differentiation into separate morphotype clusters in the coccolith example than in the case of the investigated planktonic foraminifers. The difference between the groups is explained by the differences in ontogenetic shell growth between the alga C. leptopo-rus and the foraminifer G. menardii. These differences have implications for morpho-type classification and evolutionary research by means of morphometry with coccolithophorids and foraminifers. © Palaeontological Association September 2012.

The fossil ibis Plegadis paganus is known from the Early Miocene of the Saint-Gérand-le-Puy area, France. It was first described in the 19th century by Milne-Edwards (1867-1868), who noticed similarities with members of the extant genera Eudocimus and Plegadis, a view endorsed by subsequent descriptions. The fossil's present placement within the genus Plegadis is not supported by synapomorphic features, and important differences with members of this genus have been noted in the past. The present analysis demonstrates that retention of P. paganus in the extant genus Plegadis is no longer justified, and it is therefore referred to the new genus Gerandibis. A phylogenetic analysis of 55 osteological characters supports placement of Gerandibis pagana in a clade together with Neotropical taxa. This analysis also allowed for an evaluation of the relationships among extant threskiornithids. Contrary to results obtained in molecular-based phylogenies, the present analysis supports a basal divergence of crown group Threskiornithidae into a clade comprising Threskiornis and Platalea and a clade comprising all other ibises. Within the latter, two clades, one made up of Old World taxa and the other consisting predominantly of New World taxa, were recovered. © 2013 British Ornithologists' Union.

Mary Y.,Natural History Museum Basel | Mary Y.,University of Basel | Knappertsbusch M.,Natural History Museum Basel
Marine Micropaleontology | Year: 2015

Proper species concepts of planktonic foraminifera are essential for paleo-environmental studies. Although subtle but key differences indicate the existence of sibling species, the quantitative morphological variability of foraminifera tests remains still poorly documented. We present morphological analyses of over 7500 oriented specimens of the subgenus Menardella (globorotalid foraminifera) at a time-slice at 3.2 Ma (Mid-Pliocene). Size, frequency distribution and linear test measurements were collected with an automated device, the robot AMOR. We performed morphometric investigations in a total of 19 samples distributed worldwide. Among formally established menardellid morpho-species, eight different morphotypes are recognized. The geographic variation in morphotype abundance allows for the recognition of five menardellid provinces among the tropical Atlantic, Indian and Pacific Ocean. Results suggest that during the Mid-Pliocene, the formal morpho-species Globorotalia (Menardella) menardii is in fact composed of two distinct morphotypes, which differ in size range, morphological variability and biogeography. Morphological characterization of the morpho-species Globorotalia (M.) multicamerata reveals the occurrence of three distinct morphotypes, which may represent an adaptation to their vertical distribution in the water column. © 2015.

Evolutionary prospection is the study of morphological evolution and speciation in calcareous plankton from selected time-slices and key sites in the world oceans. In this context, the Neogene menardiform globorotalids serve as study objects for morphological speciation in planktic foraminifera. A downcore investigation of test morphology of the lineage of G. menardii-limbata-multicamerata during the past 8 million years was carried out in the western tropical Atlantic ODP Hole 925B. A total of 4669 specimens were measured and analyzed from 38 stratigraphic levels and compared to previous studies from DSDP Sites 502 and 503. Collection of digital images and morphometric measurements from digitized outlines were achieved using a microfossil orientation and imaging robot called AMOR and software, which was especially developed for this purpose. Most attention was given to the evolution of spiral height versus axial length of tests in keel view, but other parameters were investigated as well. The variability of morphological parameters in G. menardii, G. limbata, and G. multicamerata through time are visualized by volume density diagrams. At Hole 925B results show gradual test size increase in G. menardii until about 3.2 Ma. The combination of taxonomic determination in the light microscope with morphometric investigations shows strong morphological overlap and evolutionary continuity from ancestral to extant G. menardii (4–6 chambers in the final whorl) to the descendent but extinct G. limbata (seven chambers in the final whorl) and to G. multicamerata (≥8 chambers in the final whorl). In the morphospace defined by spiral height (δX) and axial length (δY) Globorotalia limbata and G. multicamerata strongly overlap with G. menardii. Distinction of G. limbata from G. menardii is only possible by slight differences in the number of chambers of the final whorl, nuances in spiral convexity, upper keel angles, radii of osculating circles, or by differences in reflectance of their tests. Globorotalia multicamerata can be distinguished from the other two forms by more than eight chambers in the final whorl. It appeared as two stratigraphically separate clusters during the Pliocene. Between 2.88 and 2.3 Ma G. menardii was severely restricted in size and abundance. Thereafter, it showed a rapid and prominent expansion of the upper test size extremes between 2.3 and 1.95 Ma persisting until present. The size-frequency distributions at Hole 925B are surprisingly similar to trends of menardiform globorotalids from Caribbean DSDP Site 502. There, the observations were explained as an adaptation to changes in the upper water column due to the emergence of the Isthmus of Panama. In light of more recent paleontological and geological investigations about the completion of the permanent land connection between North and South America since about 3 Ma the present study gives reason to suspect the sudden test size increase of G. menardii to reflect immigration of extra-large G. menardii from the Indian Ocean or the Pacific. It is hypothesized that during the Late Pliocene dispersal of large G. menardii into the southern to tropical Atlantic occurred during an intermittent episode of intense Agulhas Current leakage around the Cape of Good Hope and from there via warm eddy transport to the tropical Atlantic (Agulhas dispersal hypothesis). © 2016, The Author(s).

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