A Field Guide to the Fossils of Scientists’ Cliffs A brief introduction to the geological history of the area, with descriptions of the common (and not so common) fossils found here. July 2004 Table of Contents TABLE OF CONTENTS ............................................................................................................................................ 0 1. INTRODUCTION ................................................................................................................................................... 3 1.1 BACKGROUND ................................................................................................................................................... 3 1.2 OBJECTIVES ...................................................................................................................................................... 4 1.3 SCOPE .............................................................................................................................................................. 4 1.5 APPLICABLE DOCUMENTS ................................................................................................................................. 5 1.6 DOCUMENT ORGANIZATION ............................................................................................................................... 5 2. GEOLOGY .............................................................................................................................................................. 7 2.1 NAMING ROCK/SOIL UNITS ................................................................................................................................ 7 2.2 CALVERT CLIFFS’ GEOLOGIC STRUCTURE ......................................................................................................... 8 2.3 STRATIGRAPHY ................................................................................................................................................ 12 2.3.1 Calvert Formation ............................................................................................................................... 12 2.3.2 Choptank Formation ............................................................................................................................ 13 2.3.3 St. Mary's Formation ........................................................................................................................... 13 2.4 CROSS SECTIONS OF THE CLIFFS .................................................................................................................... 13 3. FOSSIL IDENTIFICATION ................................................................................................................................ 16 3.1 VERTEBRATE FOSSILS ...................................................................................................................................... 16 3.1.1 Sharks .................................................................................................................................................. 20 3.1.1.1 Thesher Sharks ................................................................................................................................................ 21 3.1.1.2 Tiger Sharks .................................................................................................................................................... 22 3.1.1.3 Giant White Shark ........................................................................................................................................... 22 3.1.1.4 Sand Tiger Sharks ........................................................................................................................................... 23 3.1.1.5 Mako Sharks ................................................................................................................................................... 23 3.1.1.6 Snaggletooth Sharks ........................................................................................................................................ 24 3.1.1.7 Angel Sharks ................................................................................................................................................... 25 3.1.1.8 Lemon Sharks ................................................................................................................................................. 25 3.1.1.9 Requiem Sharks .............................................................................................................................................. 26 3.1.1.10 Seven Gill Sharks ....................................................................................................................................... 26 3.1.1.11 Hammer Head Sharks ................................................................................................................................ 27 3.1.2 Skates and Rays ................................................................................................................................... 27 3.1.2.1 Ray Teeth ........................................................................................................................................................ 27 3.1.2.1.1 Eagle Rays (Myliobatis) ............................................................................................................................. 28 3.1.2.1.2 Spotted-Eagle or Duck-Billed Ray (Aetobatus) ......................................................................................... 28 3.1.2.1.3 Cow-Nosed Ray (Rhinoptera).................................................................................................................... 29 3.1.2.2 Caudal Spine of the Miocene Stingrays .......................................................................................................... 29 3.1.3 Bony Fishes .......................................................................................................................................... 29 3.1.3.1 Hyperostoses “Tilly Bones” ............................................................................................................................ 32 3.1.3.2 Ocean Sunfish ................................................................................................................................................. 32 3.1.3.3 Black Drum ..................................................................................................................................................... 33 3.1.4 Reptiles ................................................................................................................................................ 34 3.1.4.1 Turtles ............................................................................................................................................................. 34 3.1.4.1.1 Leatherback Turtles ................................................................................................................................... 34 3.1.4.2 Crocodiles ....................................................................................................................................................... 35 3.1.5 Mammals ............................................................................................................................................. 36 3.1.5.1 Marine Mammals ............................................................................................................................................ 36 3.1.5.1.1 Whales and Dolphins (Cetaceans) ............................................................................................................. 37 3.1.5.1.2 Seals ........................................................................................................................................................... 39 3.1.5.1.3.1 Sea Cows (Dugongs).................................................................................................................................. 39 1 3.1.5.2 Land Mammals ............................................................................................................................................... 40 3.1.5.2.1.1 Camels ....................................................................................................................................................... 40 3.1.5.3 Epiphysis ......................................................................................................................................................... 41 3.1.6 Birds..................................................................................................................................................... 42 3.2 INVERTEBRATE FOSSILS ................................................................................................................................... 42 3.2.1 Mollusks ............................................................................................................................................... 42 Figure 6. Common Shell Fossils of Calvert County ........................................................................................................ 43 3.2.1.1 Bivalves ........................................................................................................................................................... 44 3.2.1.1.1 Scallop Shells ............................................................................................................................................. 45 3.2.1.1.2 Isognomon maxillata