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Showing results for tags 'miocene era'.
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Shark Teeth SITE LOCATION: Florida TIME PERIOD: Miocene Era (5.3-23 Million Years ago) Data: Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorpha (or Selachii) and are the sister group to the rays. However, the term "shark" has also been used for extinct members of the subclass Elasmobranchii outside the Selachimorpha, such as Cladoselache and Xenacanthus, as well as other Chondrichthyes such as the holocephalid eugenedontidans. Under this broader definition, the earliest known sharks date back to more than 420 million years ago. Kingdom: Animalia Phylum: Chordata Class: Chondrichthyes Order: Elasmobranchii Family: Selachii