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Texigryphaea marcoui bivalve SITE LOCATION: Mills County, Texas, USA TIME PERIOD: Lower Cretaceous (100-145 million years ago) Data: Gryphaea, common name Devil's toenails, is a genus of extinct oysters, marine bivalve mollusks in the family Gryphaeidae. These fossils range from the Triassic to the Tertiary periods, but are mostly restricted to the Triassic and Jurassic. Both periods belong to the era Mesozoic. They are particularly common in many parts of Britain. These oysters lived on the sea bed in shallow waters, possibly in large colonies. The complete fossils consist of two articulated valves: a larger gnarly-shaped shell (the "toenail") and a smaller, flattened shell, the "lid". The soft parts of the animal occupied the cavity between the two shells, just like modern oysters. The shells also feature prominent growth bands. The larger, curved shell sat within the mud on the sea floor. These shells are sometimes found in fossil plates along with Turritella, clams, and sometimes sharks' teeth and fossilized fish scales. Its distribution is common in areas of both Europe and North America. A classic location to find these fossils is Redcar, on the northeast coast of England. There used to be a common folk belief that carrying one of these fossils could prevent rheumatism. They are also found in abundance in the state of Kansas in riverbeds and cliffs as well as the Big Horn Canyon of Wyoming and Montana. The benthic, free-living oyster Texigryphaea was the dominant constituent of many late Albian marine communities in the Texas and southern Western Interior regions. Large topotypic assemblages of three common lower–middle Washita Group species (T. navia and T. pitcheri in Oklahoma and T. tucumcarii in New Mexico) each display considerable morphological variation in valve shape and the proportions and expression of various features. Variation within an assemblage is partly due to ontogenetic changes but is mainly ecophenotypic, with local variation in nature of substrate, water turbulence, length of attachment time, and other factors influencing the final morphology of the mature shell. Kingdom: Animalia Phylum: Mollusca Class: Bivalvia Order: Ostreoida Family: Gryphaeidae Genus: †Texigryphaea Species: †marcoui

Texigryphaea marcoui bivalve SITE LOCATION: Mills County, Texas, USA TIME PERIOD: Lower Cretaceous (100-145 million years ago) Data: Gryphaea, common name Devil's toenails, is a genus of extinct oysters, marine bivalve mollusks in the family Gryphaeidae. These fossils range from the Triassic to the Tertiary periods, but are mostly restricted to the Triassic and Jurassic. Both periods belong to the era Mesozoic. They are particularly common in many parts of Britain. These oysters lived on the sea bed in shallow waters, possibly in large colonies. The complete fossils consist of two articulated valves: a larger gnarly-shaped shell (the "toenail") and a smaller, flattened shell, the "lid". The soft parts of the animal occupied the cavity between the two shells, just like modern oysters. The shells also feature prominent growth bands. The larger, curved shell sat within the mud on the sea floor. These shells are sometimes found in fossil plates along with Turritella, clams, and sometimes sharks' teeth and fossilized fish scales. Its distribution is common in areas of both Europe and North America. A classic location to find these fossils is Redcar, on the northeast coast of England. There used to be a common folk belief that carrying one of these fossils could prevent rheumatism. They are also found in abundance in the state of Kansas in riverbeds and cliffs as well as the Big Horn Canyon of Wyoming and Montana. The benthic, free-living oyster Texigryphaea was the dominant constituent of many late Albian marine communities in the Texas and southern Western Interior regions. Large topotypic assemblages of three common lower–middle Washita Group species (T. navia and T. pitcheri in Oklahoma and T. tucumcarii in New Mexico) each display considerable morphological variation in valve shape and the proportions and expression of various features. Variation within an assemblage is partly due to ontogenetic changes but is mainly ecophenotypic, with local variation in nature of substrate, water turbulence, length of attachment time, and other factors influencing the final morphology of the mature shell. Kingdom: Animalia Phylum: Mollusca Class: Bivalvia Order: Ostreoida Family: Gryphaeidae Genus: †Texigryphaea Species: †marcoui