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Life cycle of Helicodonta obvoluta

100%

Maltz T. K.

Folia Malacologica

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1999

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tom 07

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nr 4

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Minute Silurian oncocerid nautiloids with unusual colour patterns

100%

Manda S., Turek V.

Acta Palaeontologica Polonica

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2009

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tom 54

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nr 3

503-512

A minute Silurian oncocerid Cyrtoceras pollux, from the Prague Basin is assigned here to the genus Pomerantsoceras. The only so far known species of this genus comes from the Upper Ordovician (Hirnantian) of Estonia. Pomerantsoceras thus represents, except for un−revised poorly understood taxa, the single known oncocerid genus surviving the end−Ordovician extinction events. Cyrtoceras pollux is unusual among the Silurian nautiloids because of its small shell. Colour pattern characterised by a few longitudinal bands on the entire circumference of the shell is here reported in oncocerids. Longicone and only slightly curved small shells as in Pomerantsoceras are unusual among nautiloids and resemble straight shells of orthocerids and pseudorthocerids, in which the colour pattern consists of straight colour bands. Consequently the shell shape as well as the colour pattern should be regarded as adaptive convergence with orthocerids and pseudorthocerids. It supports the hypothesis that colour pattern functioned as camouflage and its evolution was under adaptive control. In addition, several types of the shell malformations including anomalous growth of septa, shell wall and pits on an internal mould are described.

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Variation of the shell, genitalia and coloration of Perfolatella incarnata and P. vicina

80%

Pawlowska E.

Folia Malacologica

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1999

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tom 07

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nr 4

4

Shells of Unio tumidus (Bivalvia: Unionidae) from an archaeological site and contemporary population inhabiting the same lake

80%

Ozgo M., Bogucki Z., Nowakowska M.

Polish Journal of Ecology

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2012

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tom 60

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nr 4

Mollusc shells from archaeological excavations are often well preserved and allow for species identification and measurements. Large shell assemblages can provide information for environmental reconstruction and investigation of anthropogenic impacts. In this study we compare freshwater mussel shells from a shell midden excavated on a lake island in northern Poland, dated 2,700–2,600 BP, with contemporary populations from that lake. No changes in species composition occurred, with only Unio tumidus and Anodonta sp. present in the prehistoric sample, and Unio tumidus and Anodonta anatina in the contemporary one. In both the archaeological and contemporary samples, shells of Unio tumidus were relatively small (mean shell length 49.3 } 5.2 mm, max 64 mm, and 46.0 } 5.9 mm, max 61 mm, respectively). However, the values of all measured characteristics (length, height, mass, and thickness) were significantly lower in the contemporary compared to prehistoric shells. In modern times, in the region of the study largescale forest clearing and conversion of land into agricultural areas occurred; presently areas of intensive agriculture directly adjoin the lake. Dwarfing of the shells likely results from anthropogenic deterioration of mussel habitat.

Ograniczanie wyników

2 Folia Malacologica

1 Acta Palaeontologica Polonica

1 Polish Journal of Ecology

1 Bogucki Z.

1 Maltz T. K.

1 Manda S.

1 Nowakowska M.

1 Ozgo M.

1 Pawlowska E.

1 Turek V.

1 2012

1 2009

2 1999

Life cycle of Helicodonta obvoluta

Minute Silurian oncocerid nautiloids with unusual colour patterns

Variation of the shell, genitalia and coloration of Perfolatella incarnata and P. vicina

Shells of Unio tumidus (Bivalvia: Unionidae) from an archaeological site and contemporary population inhabiting the same lake