Argopecten gibbus (Linnaeus, 1767) - Atlantic calico scallop shell, modern (latest Holocene)
Bivalves are bilaterally symmetrical molluscs having two calcareous, asymmetrical shells (valves) - they include the clams, oysters, and scallops. In most bivalves, the two shells are mirror images of each other (the major exception is the oysters). They occur in marine, estuarine, and freshwater environments. Bivalves are also known as pelecypods and lamellibranchiates.
Bivalves are sessile, benthic organisms - they occur on or below substrates. Most of them are filter-feeders, using siphons to bring in water, filter the water for tiny particles of food, then expel the used water. The majority of bivalves are infaunal - they burrow into unlithified sediments. In hard substrate environments, some forms make borings, in which the bivalve lives. Some groups are hard substrate encrusters, using a mineral cement to attach to rocks, shells, or wood.
The fossil record of bivalves is Cambrian to Recent. They are especially common in the post-Paleozoic fossil record.
Scallops are distinctive bivalves with nearly symmetrical valves. The convexity and color of the two valves of an individual can vary dramatically in many species.
Classification: Animalia, Mollusca, Bivalvia, Pteriomorphia, Pectinoida, Pectinidae
Locality: Lighthouse Point beach, southern shore of the eastern tip of Sanibel Island, Gulf of Mexico coast of southern Florida, USA
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More info. at:
en.wikipedia.org/wiki/Scallop
and
en.wikipedia.org/wiki/Argopecten_gibbus
Tags: Argopecten gibbus Atlantic calico scallop shell shells scallops Sanibel Island Florida
Conus spuroides Olsson & Harbison, 1953 - fossil cone snail shells from the Cenozoic of Florida, USA. (abapertural view; field of view ~5.4 cm across)
The gastropods (snails & slugs) are a group of molluscs that occupy marine, freshwater, and terrestrial environments. Most gastropods have a calcareous external shell (the snails). Some lack a shell completely, or have reduced internal shells (the slugs & sea slugs & pteropods). Most members of the Gastropoda are marine. Most marine snails are herbivores (algae grazers) or predators/carnivores.
The conid gastropods (cone shells) are fascinating marine snails for a couple reasons - they have attractively-shaped, colorful shells and they are killers. The conids are predatory, as are many other marine snails, but they take down their prey in an unusual fashion. The radula of most snails is a mineralized or heavily sclerotized mass of small teeth that scrapes across a substrate during feeding. Conid snails have a toxoglossate radula - one that has been evolutionarily modified into tiny, unattached, toxin-bearing, harpoon-like darts (see photo - science.naturkundemuseum-bw.de/files/images/niederhofer_2...) that can be fired at prey. Each dart is an individual tooth. The nickname "killer snails" is well deserved (even people have been killed). Some species have incredibly powerful toxins, while in other species the toxin has little effect on humans.
The fossil cone snails shown above are from richly fossiliferous beds in the Cenozoic of Florida. Many quarries and pits in such beds produce fossil shell "gravel" for use in non-paved roadways, sidewalks, and decorative landscaping.
Note the presence of fossil color spots in the left three shells. Bleached-away color spots in fossil snail shells may show up under ultraviolet black light (UV).
Classification: Animalia, Mollusca, Gastropoda, Neogastropoda, Conoidea, Conidae
Stratigraphy: supposedly derived from the Caloosahatchee Formation, Upper Pliocene to Lower Pleistocene
Locality: apparently derived from a commercial quarry pit in southwestern Florida, USA
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More info. at:
en.wikipedia.org/wiki/Conus
Tags: Conus spuroides conid Conidae cone fossil fossils snail snails shell shells gastropod gastropods Caloosahatchee Formation Pliocene Pleistocene Florida color colors spots
Cyrtopleura costata Linnaeus, 1758 - angelwing clam shell (modern) from Florida, USA.
Bivalves are bilaterally symmetrical molluscs having two calcareous, asymmetrical shells (valves) - they include the clams, oysters, and scallops. In most bivalves, the two shells are mirror images of each other (the major exception is the oysters). They occur in marine, estuarine, and freshwater environments. Bivalves are also known as pelecypods and lamellibranchiates.
Bivalves are sessile, benthic organisms - they occur on or below substrates. Most of them are filter-feeders, using siphons to bring in water, filter the water for tiny particles of food, then expel the used water. The majority of bivalves are infaunal - they burrow into unlithified sediments. In hard substrate environments, some forms make borings, in which the bivalve lives. Some groups are hard substrate encrusters, using a mineral cement to attach to rocks, shells, or wood.
The fossil record of bivalves is Cambrian to Recent. They are especially common in the post-Paleozoic fossil record.
Classification: Animalia, Mollusca, Bivalvia, Heterodonta, Myida, Pholadidae
Locality: southern end of the western shoreline of Cayo Costa Island, western side of Pine Island Sound, offshore from the Gulf of Mexico coast of southern Florida, USA
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See info. at:
en.wikipedia.org/wiki/Cyrtopleura_costata
Tags: Cyrtopleura costata angelwing clam shell clams shells Cayo Costa Island Florida
Vermicularia fargoi Olsson, 1951 - Fargo's worm snail in Florida, USA.
The gastropods (snails & slugs) are a group of molluscs that occupy marine, freshwater, and terrestrial environments. Most gastropods have a calcareous external shell (the snails). Some lack a shell completely, or have reduced internal shells (the slugs & sea slugs & pteropods). Most members of the Gastropoda are marine. Most marine snails are herbivores (algae grazers) or predators/carnivores.
Shown above is one of the more bizarre gastropod shells around - this is Vermicularia, also called a worm snail. It’s one of the few snails that does not have a tightly coiled shell. Several snails from different families have shells somewhat like this (e.g., the vermetids & the turritellids). They all resemble the twisted mineralized shells made by some annelid worms, hence the common name “worm snails” or “worm shells”.
Despite the superficially very different-looking shells, malacologists have demonstrated that Vermicularia is very closely related to the high-spired snail Turritella (www.gastropods.com/Shell_Images/T/Turritella_terebra_2.jpg). Juvenile Vermicularia are free living, infaunal filter feeders that position themselves apex-down and aperture-up within the sediment. During this stage in ontogeny, the Vermicularia shell is tightly coiled, as is any ordinary gastropod shell. Later in life, the snail becomes an epifaunal, encrusting filter feeder (assuming hard or firm substrates are available), and its shell starts uncoiling. The advantage of an uncoiled shell in Vermicularia is generally inferred to be rapid upright growth (that’s desirable for a sessile, benthic filter feeder).
If hard or firm substrates aren’t available, Vermicularia generally doesn’t grow an unwound shell during growth, and it ends up looking like a typical Turritella shell. The degree of uncoiling also depends on the nature of the hard substrate (e.g., a ramose scleractinian coral vs. a hemispherical scleractinian coral vs. a bivalve shell). So, shell uncoiling is an ecophenotypic character.
Classification: Animalia, Mollusca, Gastropoda, Turritellidae
Provenance: marine beach from near the southern end of Cayo Costa Island, southwestern Florida, USA
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Most info. synthesized from Morton (1953) and Gould (1968, 1969):
Morton (1953) - Vermicularia and the turritellids. Proceedings of the Malacological Society of London 30: 80-86.
Gould (1968) - Phenotypic reversion to ancestral form and habit in a marine snail. Nature 220: 804.
Gould (1969) - Ecology and functional significance of uncoiling in Vermicularia spirata: an essay on gastropod form. Bulletin of Marine Science 19: 432-445.
Tags: Vermicularia fargoi Fargo's worm snail Cayo Costa Island Florida snails shell shells gastropod gastropods
Neverita duplicata (Say, 1822) - shark's eye snail shell from Florida, USA; modern (latest Holocene). (apical view)
The gastropods (snails & slugs) are a group of molluscs that occupy marine, freshwater, and terrestrial environments. Most gastropods have a calcareous external shell (the snails). Some lack a shell completely, or have reduced internal shells (the slugs & sea slugs & pteropods). Most members of the Gastropoda are marine. Most marine snails are herbivores (algae grazers) or predators/carnivores.
Classification: Animalia, Mollusca, Gastropoda, Naticidae
Locality: Marco Island, Gulf of Mexico coast of southern Florida, USA
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Info. at:
en.wikipedia.org/wiki/Neverita_duplicata
Tags: Neverita duplicata shark's eye snail shell shells snails Marco Island Florida Naticidae
