Timetable of Clams

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Timetable of Bivalve Drawing (Six Clams and One Scallop)

Clams fall under the class of animals called “Bivalia” which are soft bodied, filter-feeding animals with two identical shell halves. Some attach themselves to a substrate on the sea bottom while others simply hang around deep in the depths, and yet a few are capable of free swimming, namely the scallops. Most, are marine salt water animals while a few varieties have evolved into fresh water habitats. I have drawn a few samples of bivalves and or clams. They are amazing animals, one of Earth’s original complex organisms and they are still with us today after 500 million years! The drawings represent seven species from all three of Earth’s timetable eras including the Paleozoic, Mesozoic and Cenozoic. Find out their genus names and brief descriptions from the oldest to most recent, along with fossil samples primarily found on the internet. 

Middle Left Orange Colored Rendering: Ctendonta has smooth surface with fine concentric growth lines and teeth along the hinge plate. Ordovician – Silurian (505 million years ago (mya) to 408 mya)

Top Right Pinkish Colored Rendering: Modiolopsis has asymmetrical thin valves crossed by an oblique depression. Ordovician-Silurian (505 mya to 408 mya)  

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MODIOLOPSIS Fossil Clam Shell

Middle Bluegreen Colored Rendering: Byssonychia has sharp steeply inclined beak near end of hinge; usually has strong radial ribs. Mostly Upper Ordovician (400 mya)

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BYSSONYCHIA Source: Wendell Rickets (All Rights Reserved) https://invertebrateme.wordpress.com/2012/03/10/byssonychia-sp/

Top Middle Yellow/Brown Colored Rendering: Goniophora has a lopsided shell with a prominent beak and ridge extending to the rear margin. Silurian – Devonian (438 mya – 360 mya)  

Bottom Left Goldish/Brown Colored Rendering: Pteria has thin inequilateral shaped valves with a long straight hinge merging into large unequal wings. Jurassic to recent (245 mya – today)

Bottom Right Tanish/Peach Colored Rendering: Glycimeris has symmetrical circular outline with pointed beak. Cretaceous to Recent (144 mya – today)

Top Left Deep Blue Colored Rendering: Pecten is a genus of many well known bivalves otherwise know as large scallops. Valves have strong radial ribs and are symmetrical except for slightly unequal wings. Mississippian to Recent (360 mya – today)

Bivalves feed the world. Bivalve oysters, scallops and clams are near the bottom of the food chain which many marine and freshwater species depend on for a food source. But don’t forget about land creatures such as otters, for one, and we humans who especially enjoy a treat of clam chowder. Their shells, secreted from calcium carbonate, can be beautiful and are used to adorn our homes in many creative ways.  Scan_Pic0009