A New Silurian (Llandovery, Telychian) Sponge Assemblage from Gotland, Sweden

A newly discovered, diverse sponge fauna of early Silurian age, is described from Gotland, Sweden. This is the first Silurian sponge assemblage known from Baltica, and the only diverse Llandoverian assemblage known worldwide. The fauna includes 20 genera and 29 species, of which three genera and six species are new. Eighteen species are new to Baltica. The fauna shows strong similarities to later Silurian assemblages in Arctic Canada, but one endemic species comprises ca. 50% of the fauna. The fauna shows that lithistid sponges recovered well from the late Ordovician extinction in some areas, and became widely spread in the early Silurian. In contrast, non-lithistid sponges like, such as hexactinellids, appear to have evolved rapidly during the Late Ordovician - early Silurian interval, and some modern groups probably originated in inshore habitats.

Autorentext

Freek Rhebergen and Joseph Botting are the authors of A New Silurian (Llandovery, Telychian) Sponge Assemblage from Gotland, Sweden, published by Wiley.

Inhalt
Introduction 1 Institutional abbreviations 3

Geological setting 3

Material, methods, terminology 6

Systematic palaeontology 8

Phylum Porifera Grant, 1836 8

Class Demospongea Sollas, 1875 8

Order Orchocladina Rauff , 1895 8

Family Anthaspidellida Miller, 1889 8

Genus Archaeoscyphia Hinde, 1889 8

Archaeoscyphia minganensis Billings, 1859 8

Archaeoscyphia annulata Rigby, 1973 12

Archaeoscyphia gislei de Freitas, 1989 14

Archaeoscyphia rectilinearis de Freitas, 1989 16

Archaeoscyphia aulocopiformis de Freitas, 1989 18

Archaeoscyphia scalaria de Freitas, 1989 19

Archaeoscyphia attenuata de Freitas, 1989 21

Genus Finksella Rigby & Dixon, 1979 22

Finksella turbinata Rigby & Dixon, 1979 22

Genus Calycocoelia Bassler, 1927 24

Calycocoelia typicalis Bassler, 1927 24

Genus Climacospongia Hinde, 1884 25

Climacospongia undulata de Freitas, 1991 26

Genus Multistella Finks, 1960 28

Multistella leipnitzae nsp 29

Genus Somersetella Rigby & Dixon, 1979 32

Somersetella amplia Rigby & Chatterton, 1989 32

Somersetella digitata Rigby & Dixon, 1979 34

Family Streptosolenidae Johns, 1994 35

Genus Postperissocoelia ngen 35

Postperissocoelia gnisvardensis nsp 36

Family Chiastoclonellidae Rauff , 1895 38

Genus Chiastoclonella Rauff , 1895 39

Chiastoclonella spRauff , 1895 39

Subclass Tetractinomorpha Lévi, 1953 39

Order Streptosclerophorida Dendy, 1924 39

Suborder Eutaxicladina Rauff , 1894 39

Family Hindiidae Rauff , 1893 39

Genus Hindia Duncan, 1879 40

Hindia sphaeroidalis Duncan, 1879 40

Suborder Sphaerocladina Schrammen, 1910 42

Family Astylospongiidae Zittel, 1877 42

Genus Caryoconus Rhebergen & van Kempen, 2002 42

Caryoconus gothlandicus (Schlüter, 1884) 42

Genus Lindstroemispongia ngen 45

Lindstroemispongia cylindrata nsp 47

Order Spirosclerophorida Reid, 1963 48

Suborder Rhizomorina Zittel, 1878a 48

Family Haplistiidae de Laubenfels, 1955 48

Genus Haplistion Young & Young, 1877 48

Haplistion minutum Rigby & Dixon, 1979 50

Haplistion cylindricum Rigby & Dixon, 1979 52

Haplistion toftanum nsp 54

Haplistion spYoung & Young, 1877 57

Genus Warrigalia Rigby & Webby, 1988 59

Warrigalia robusta Rigby & Webby, 1988 59

Rhizomorina indet 62

Subclass Tetractininellida? Marshall, 1876 62

Order Hadromerida? Topsent, 1898 63

Family uncertain 63

Genus Opetionella von Zittel, 1878 63

Opetionella incompta nsp 63

Class Hexactinellida Schmidt, 1870 65

Order Lyssacinosida? von Zittel, 1877 65

Family uncertain 65

Genus Urphaenomenospongia ngen 65

Urphaenomenospongia euplectelloides nsp 66

Lyssacinosida? indet 69

Order and family uncertain 71

Hexactinellid indetA 71

Hexactinellid indetB 71

Spiculite 72

Class Stromatoporoidea Stearn, Webby, Nestor & Stock, 1999 74

Order Labechiida Kühn, 1927 74

Family Stylostromatidae Webby, 1993 74

Genus Pachystylostroma Nestor, 1964 74

Pachystylostroma sp 74

Order Clathrodictyida Bogoyavlenskaya, 1969 76

Family Clathrodictyidae Kühn, 1939 76

Genus Clathrodictyon Nicholson & Murie, 1878 76

Clathrodictyon sp 76

Order Stromatoporida Stearn, 1980 76

Family Syringostromellidae Stearn, 1980 76

Genus Syringostromella Nestor, 1966 76

Syringostromella sp 76

Order Amphiporida Rukhin, 1938 76

Family Amphiporidae Rukhin, 1938 76

Genus Amphipora Schulz, 1883 76

Amphipora sp 76 Palaeobiogeography and community evolution 7...