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Porifera

Porifera - Class Hexactinellida – Cambrian-R “glass...

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Fossil Algal Megaflora Stromatolites & Oncolites – cyano-bacterial colonies, layered sediment (flat/columnar vs spherical “algal biscuits”)
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Fossil Algal Megaflora Calcareous Green Algae (Chlorophyta) – Ord-R modern Halimeda and Penicillus
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Fossil Algal Megaflora Fossil Receptaculites – Dasycladacean Green Algae?
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Fossil Algal Megaflora Coralline Red Algae (Rhodophyta) – Ord - R Solenopora – Ord – Jr
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Porifera Simplest metazoa – heterotrophic multicellular Limited differentiation of cells, no coelom All sessile suspension feeders Record Cambrian – R, generally poor fossilization Marine & fresh
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Sponge Biology Choanocyte – “collar” cells, make current Sclerocyte – make spicules Spongocyte – make spongin Archaeocyte – general purpose in mesohyl Ostum – incurrent Spongocoel – cavity Osculum – outcurrent Reproduction – asexual by budding, sexual by release of egg (from archaeocytes) and sperm (from choanocytes) into water Gemmules – armored archaeocytes
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Sponge Systematics
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Unformatted text preview: Class Hexactinellida – Cambrian-R - “glass sponges”, spicules of silica. Today common in cold deep waters. Hydnoceras Euplectella Sponge Systematics Class Calcarea – Cambrian-R - “calcareous sponges”. Today warm shallow waters. Heteroactines Sphinctozoans ex. Astraeospongia ex . Girtyocoelia Sponge Systematics Class Demospongea – Cambrian-R – framework primarily spongin, a few siliceous spicules (monaxons, tetraxons 60/120, demas) Astylospongia Sponge Systematics Class Sclerospongea – Sil-R – calcareous & siliceous spicules or none. May occupy cryptic habits. Stromatoporoids now included here. Psammobiotic sponges • Sponges living in sediment. Facilitate cementation of carbonate sand to produce hardgrounds. Beginning point for modern reefs. Archaeocyathids • Early – Middle Cambrian, marine. Shallow current-washed water, high tolerance to turbidity. Passive filterer? Cambrian reef builders, symbiotic algae?...
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Porifera - Class Hexactinellida – Cambrian-R “glass...

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