File:Stromatoporoid (probably the Traverse Group, Middle Devonian; Northport area, Michigan, USA) 4.jpg
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English: Stromatoporoid sponge with mamelons and astrorhizae from the Devonian of Michigan, USA.
Sponges are sessile, benthic, filter-feeding organisms. They are not metazoan animals, as they lack organs or tissues - they are called parazoans. Sponges are essentially colonies of cells (the cells can live independently for short periods of time). Most sponges are marine, but some occupy freshwater environments. Sponges construct organic or mineralized, multi-element skeletons. Individual pieces of a sponge skeleton are called spicules. The group first appears in the fossil record in the Neoproterozoic and extends to today, in the Holocene. Some sponges make skeletons composed of opal spicules (SiO2·nH2O - hydrous silica), while others are calcareous (calcite or aragonite) or make spicules of organic material (spongin - a tough, proteinaceous, organic compound). Seen here is a partial stromatoporoid fossil. They occur in Paleozoic and Mesozoic sedimentary rocks (Ordovician to Cretaceous), but the Mesozoic-aged stromatoporoids may represent a separate group. Stromatoporoids have a layered, calcitic skeleton, usually with small vertical pillars between individual layers (laminations). The top living surface has small mounds (mamelons) with radiating canals (astrorhizae) - this specimen has preserved mamelons, expressed as depressions, because we're looking at their undersides. Astrorhizae are well preserved on this surface (click on the photo once or twice to zoom in). Stromatoporoids are similar to a living group of sponges called the sclerosponges - some researchers place the stromatoporoids with the sclerosponges. Stromatoporoids were important components of some Paleozoic and Mesozoic shallow-water reefs. Classification: Animalia, Porifera, Stromatoporoidea Stratigraphy: probably derived from the Traverse Group (Middle Devonian) Locality: unrecorded locality at or near the town of Northport (likely from the shoreline of Lake Michigan), northern Lower Peninsula of Michigan, USA |
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| Source | https://www.flickr.com/photos/47445767@N05/50354666542/ |
| Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/50354666542. It was reviewed on 26 October 2020 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| current | 13:58, 26 October 2020 | | 4,000 × 2,059 (3.66 MB) | Ser Amantio di Nicolao (talk | contribs) | Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/50354666542/ with UploadWizard |
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