Fossils

Fossils johncallahan Fri, 06/25/2010 - 10:07

What is a fossil?

What is a fossil? johncallahan Mon, 07/13/2009 - 15:42
Body

The Glossary of Geology (Glossary of Geology, 4th edition, 1997, Edited by Julia A. Jackson: American Geological Institute, Alexandria, VA) defines a fossil as “any remains, trace, or imprint of a plant or animal that has been preserved in the earth’s crust since some past geologic or prehistoric time.” The field of geology involving the study of fossils is called paleontology. Fossils are of great use to geologists in understanding what the earth was like in the distant past and how life has changed through time. They are also a practical tool in the correlation of sedimentary rock layers from one area to another, which is an important part of exploring for petroleum and understanding the underground "plumbing" of groundwater systems.

Fossils can be fun to collect and interesting to study for the amateur, but they also tell geologists about the history of the world and how it was formed. The best time to look for fossils is after a heavy rain, when pieces of shell and fossil may be exposed in the soil. A stick is handy for scratching around in the top layer of soil. Collectors should remember their manners and should enter pits or other privately owned areas only after obtaining the owner's permission.

Delaware Geological Survey Special Publication Nos. 18 & 19 offer helpful hints for fossil identification and collection. These booklets are available by contacting the Survey or through the on-line ordering of DGS publications.

The most common fossils found in Delaware are from the Cretaceous period, and range from 65 to 100 million years in age. Some fossil collecting localities have also been found in central and southern Delaware, with the fossils generally being younger further south in the state. Fossils found in Kent County are commonly 12 to 20 million years old, and those in Sussex County mostly date from less than less than 1 million years.

Dinosaurs in Delaware?

Dinosaurs in Delaware? johncallahan Thu, 01/14/2010 - 21:45
Body

Only fragmentary remains of dinosaurs have been found in Delaware. All of these have come from the Chesapeake and Delaware Canal, mainly from the spoil piles created by the dredging of the Canal. Various nature groups in Delaware lead trips to the Canal for collecting. Most of the fossils found are those of marine invertebrates (primarily bivalves and gastropods with some remains of sponges, ammonites, and belemnites).

These fossils date to the late Cretaceous (97 to 65 million years ago) and come from the marine sediments of the Marshalltown and Merchantville Formations. Of the dinosaur remains, none have been complete enough for genus and species identification. At least two hadrosaurid (duck-bill dinosaurs such as Maiasaura) teeth have been found. Several toe bones of ornithomimosaur (small and agile theropod predators that look something like plucked ostriches with long tails and arms) dinosaurs and a partial hadrosaurid vertebra have been recovered. In addition to the dinosaur remains, other vertebrate fossils that have been recovered include: teeth of the marine reptiles Mosasaurus, Globidens, and Tylosaurus; part of a jaw and plates (scutes) of the giant crocodile Deinosuchus; a pleisiosaur vertebra; remains of bony fishes; and shell fragments of the turtles Trionyx, Toxochelys, and other forms. One of the most unique remains found in Delaware is that of a neck bone and a wing bone from a pterosaur (a flying reptile).

Sources of Information

There are many excellent books on dinosaurs available at your local library. A very good book on collecting dinosaur fossils in this region is one entitled "Dinosaurs of the East Coast" and was written by David B. Weishampel and Luther Young. It was published in 1996 by The Johns Hopkins University Press. The book is very thorough in describing dinosaur fossil collecting localities from all along the East Coast of North America, the kinds of dinosaurs to be found, and the habitats and lifestyles.

Another fine book on local dinosaurs is written by William B. Gallagher and is entitled "When Dinosaurs Roamed New Jersey." It was published by Rutgers University Press in 1997. It describes the dinosaur fossils that have been found in New Jersey as well as some information about those from Delaware. The information of dinosaurs from Delaware given above comes from these books. For information regarding the Cretaceous fossils from Delaware, the following are available from the Delaware Geological Survey:

Latitude
39.68
Longitude
-75.75
Set Cover Image?
Off

Fossil Sites In Delaware

Fossil Sites In Delaware johncallahan Mon, 07/13/2009 - 15:47
Body

Delaware offers a few sites for fossil collectors, and the Chesapeake and Delaware Canal and the Pollack Farm are first two locations to check out. Much information is known about these two sites. More information is below, including references to DGS publications detailing the areas. Some other locations throughout the state also offer good hunting grounds for fossil collectors. If you know of good sites in Delaware not listed on this page, please feel free to contact us!

Chesapeake and Delaware Canal - Cretaceous Fossils

The Chesapeake and Delaware Canal is likely the best site in Delaware for fossil collecting. When the canal was built, several formations having fossils from the Cretaceous Period (144 to 65 million years ago) were exposed. Fossils found there represent life forms that existed for a good portion of that period of time and that lived in a shallow sea or along the seashore. The fossils include large clam and oyster shells and a pen-shaped fossil called a belemnite. The belemnite species Belemnitella americana is one of the more common fossils from this area and so was designated Delaware's state fossil. It comes from the inside of a squid-like animal that lived in the seas of the Cretaceous Period. Similar fossils are found in New Jersey and in England. Geologists can use this information to correlate geologic rock units in different areas, allowing them to link events in different parts of the world.

Most fossils found in the Canal area are called "steinkerns." These are formed when a shell fills with mud that later hardens. In some cases, the shell then dissolves, although at the Canal many original shells also are preserved. Other fossils commonly found at the Canal include fish and reptile bones, including vertebrae and teeth.

Good locations at the Canal to search for fossils are the dredge spoils near St. Georges and at the foundation of the Reedy Point Bridge. The U. S. Army Corps of Engineers has jurisdiction over the Canal lands, and small-scale collecting of fossils for private collections is permitted. It is against federal law to collect fossils from the area to sell.

For more information




Pollack Farm - Miocene Fossils

Located in Kent County, Delaware, the Pollack Farm Site was a surprise to many to contain numerous fossils. The fossils discovered range from a simple Arthropod, small insect, to large vertebrates, such as sharks. In 1991, while Delaware Geological Survey staff collected earth minerals during a highway construction, they came across an upper shell bed full of molluscan fossils. As digging continued numerous fossils of various species and phylum were found.

The Delaware Geological Survey provides a resource of facts and photos of the numerous fossils found in central Delaware. This site includes links to four main phylum, which lead to fossil photographs containing brief descriptions.

For more information




Delaware Mineralogical Society

The Delaware mineralogical Society is a nonprofit organization dedicated to the promotion and education of mineralogy, paleontology and the lapidary arts. They hold regular meetings, an annual rock and mineral show (with numerous fossils for sale, great for kids and collectors alike!), and field trips throughout the state and surrounding area. Refer to their website below for more information.




Other Fossil Sites in Delaware

Other locations throughout the state also offer good hunting grounds for fossil collectors. Just south of Dagsboro, where Route 113 crosses Pepper Creek, the collector can find young (less than 2 million year old) marine fossils from the Pleistocene Epoch. At the state sand and gravel pit just south of Middletown on Route 896, plant impressions from the Pleistocene may be found.

A variety of Miocene fossils are know from central Delaware. Fossils from the Miocene epoch, approximately 15 million years in age, have been found in the banks of the Coursey and Killen Ponds near Felton. This is addition to the fossils found at Pollack Farm.

For more information:

Fossil Identification Sheet

Fossil Identification Sheet johncallahan Thu, 04/15/2010 - 14:45
Body

Belemnite

In Delaware, the best place to look for Belemnitella americana is in the dredge spoil piles on the north side of the Chesapeake and Delaware Canal, just west of St. Georges and also just east of the north side of the Reedy Point Bridge. On July 2, 1996, belemnite was named as the official fossil of Delaware. More information can be found at Delaware's State Fossil.

Bivalve Steinkerns and Molds

A steinkern is an internal mold, or a type of fossil formed when a shell fills with mud that later hardens. The external molds of shells are also commonly fossilized. These molds were produced by shells of bivalves, the group of molluscs with two hinged shells such as clams, oysters, and scallops in Delaware's ancient seas. These bivalve steinkerns and molds are from the late part of the Cretaceous Period, approximately 65 to 85 million years old. These fossils were found along the Chesapeake and Delaware Canal.

Fossil Scallop

Along the western shore of the Chesapeake Bay in southern Maryland is a famous fossil collecting area known as the Calvert Cliffs. Among the many shells are beautiful fossil scallops, including forms like this called Pecten or Chesapecten. These fossils are from the Miocene epoch, between 5 and 25 million years old.

Gryphaea

Gryphaea is an oyster that lived in Delaware's shallow seas during the age of the dinosaurs. This fossil can be found along the Chesapeake and Delaware Canal, within the Mount Laurel Formation and the Marshalltown Formation, which were deposited between 65 and 85 million years ago during the late part of the Cretaceous Period.

Marine Mammal Bone

Along the western shore of the Chesapeake Bay in southern Maryland is a famous fossil collecting area known as the Calvert Cliffs. Among the shells are common bones and bone fragments which are the remains of ancient marine mammals (probably dolphins, whales and seals). Note the spongy appearance of the bone. These fossils are from the Miocene epoch, between 5 and 25 million years old.

Petrified Wood

Petrified wood may be found in pits and stream banks in northern Kent County and southern New Castle County, Delaware. This petrified wood occurs near where porous, sandy layers lie on layers that contain abundant fossil diatoms. Diatoms are microscopic shells made of silica, the same compound as opals. The silica is dissolved by water passing through the sand. When this water flows to and soaks the buried wood, it can recrystallize and fill the pores in the wood. The central Delaware petrified wood is from either the Miocene epoch (5 to 25 million years ago) or the Pleistocene epoch (10,000 years to 2 million years ago).

Cretaceous Fossils of the C&D Canal

Cretaceous Fossils of the C&D Canal johncallahan Fri, 06/25/2010 - 10:24

Cretaceous Fossils Overview

Cretaceous Fossils Overview johncallahan Mon, 07/13/2009 - 15:49
Body

The Cretaceous Period is the last period in the Mesozoic Era, a time in earth history commonly called "The Age of the Reptiles." This period lasted from approximately 144 to 65 million years ago.

Delaware was mostly an area of rivers, swamps, and dry land during the early part of the Cretaceous Period. During the late part of the Cretaceous, the sea covered most of Delaware. These ancient seas left deposits that contain the remains of marine life that lived on the sea bottom and swam in the water.

This web site is designed to show some of the fossil remains of this Cretaceous marine life that have been found in Delaware. Many fossils have been collected in the past from Cretaceous deposits exposed along the Chesapeake and Delaware (or C&D) Canal in northern Delaware. Most of the good collecting localities have been covered in recent years as the canal has been widened and improved, but in places fossils still can be found in "spoil piles," which are piles of material dug from the bottom of the canal when it is deepened or cleaned.

This web site describes many of the types of fossils that are known from the Cretaceous deposits of Delaware. It includes pictures and drawings of many of the fossils. It also provides a checklist of Delaware's Cretaceous as well as some maps that show collecting sites and the geology of the area.

Whether you are interested in collecting yourself, or just want to learn about Delaware's fossils, we hope this web page will give you helpful information.

One-celled Organisms: Phylum Protozoa

One-celled Organisms: Phylum Protozoa johncallahan Mon, 07/13/2009 - 15:54
Body

Protozoans are one-celled organisms that include the amoeba. One group of protozoans, the Foraminifera ("forams"), are among the most common fossils found in the Cretaceous of Delaware -- but are hard to study without a microscope. Forams build a hard outer covering -- some by secreting calcium carbonate or opaline silica, some by cementing sand grains -- in order to provide support and protection. The resulting many-chambered shells, which are commonly called "tests," are the parts preserved as fossils. Some are very simple, and others are very ornate.

Foraminifera live almost exclusively in marine environments. Some foraminifera live on the sea bottom or within sea bottom sediments -- these are referred to as benthic foraminifera. Others float in the water -- these are called planktonic. Certain species of benthic foraminifera are known to prefer to live in certain marine environments, making them useful in interpreting the marine conditions that existed in the past. Planktonic foraminifera are commonly useful for determining the age of ancient sediments because of the rapid evolution through time of many groups.

Forams are usually collected by special filtration and floatation techniques and studied under the microscope because of their tiny size. However, two genera from the Cretaceous of Delaware, Dentalina and Citharina, are large enough to be seen in a magnifying glass and are fairly common in the Mount Laurel dredge spoils.

Reference(s)

Photograph and figures from DGS Special Publication No. 18, by E. M. Lauginiger, 1988.

Sponges: Phylum Porifera

Sponges: Phylum Porifera johncallahan Tue, 07/14/2009 - 01:07
Body

Phylum Porifera is a group of simple animals that includes the sponges. Porifera have no internal organs, nervous tissue, circulatory system, or digestive systems, making them the most primitive of the multi-cellular animals. To support and protect their soft bodies, sponges produce skeletons of calcium carbonate, silica, or a soft organic material called spongin. The most common fossil sponge in the Cretaceous sediments of Delaware is the genus Cliona. Cliona sponges lived on rocks and shells of the seafloor and commonly bored holes in these objects, in which it lived. To obtain food, the sponges filtered the water around them as it passed through tiny pores located on their outer walls. The sponge is common in the Mount Laurel Formation along the Canal.

Reference(s)

Photographs and figures from DGS Special Publication No. 18, by E. M. Lauginiger, 1988.

Clams, Snails, and Squid: Phylum Mollusca, Class Gastropoda

Clams, Snails, and Squid: Phylum Mollusca, Class Gastropoda johncallahan Fri, 07/31/2009 - 10:08
Body

Gastropods is the group of molluscs that includes the snails. Many types secrete a single coiled or uncoiled shell for protection, and these shells may be found as fossils. Some species spend their lives crawling along the sea floor, eating algae or debris from rocks and bottom sediments. Others are predatory and feed on other molluscs such as clams and oysters by drilling with a "radula" or rasping tongue.

Most of the Cretaceous gastropod fossils from the Canal are internal casts (steinkerns). They are difficult to identify, and most can only be assigned to a family or genus. Gastropods are abundant in the spoils from the Mount Laurel Formation on both sides of the Canal in the vicinity of Reedy Point.

Photo Gallery
Reference(s)

Unless otherwise noted, photographs and figures are from DGS Special Publication No. 18, by E. M. Lauginiger, 1988.

Clams, Snails, and Squid: Phylum Mollusca, Class Cephalopoda

Clams, Snails, and Squid: Phylum Mollusca, Class Cephalopoda johncallahan Fri, 07/31/2009 - 10:52
Body

Phylum Mollusca
Class Cephalopoda
Cephalopods are a group of molluscs that include the pearly chambered Nautilus, squids, and the octopus. They can be divided into three categories: the Nautiloidea (chambered Nautilus), the Ammonoidea (the extinct ammonites), and the Dibranchiata (squids, the extinct belemnites, and octopuses).

Ammonite fossils occur in places in the Cretaceous of Delaware. An ammonite can be thought of as an octopus stuffed inside a straight, coiled, or spiral shell. They are uncommon finds at the C & D Canal, usually occuring as broken pieces; a complete one is a rare and exciting find. Most of the larger coiled ones are found in the Merchantville Formation. Sections of the straight-shelled Baculites are more common in the Mount Laurel Formation.

The belemnite species Belemnitella americana is the Delaware State Fossil. They are amber colored, bullet-shaped fossils that served as the internal skeleton in an extinct squid-like animal called a belemnoid. Belemnites are a common find on the Mount Laurel spoils pile because they probably traveled in large schools.

Reference(s)

Unless otherwise noted, photographs and figures are from DGS Special Publication No. 18, by E. M. Lauginiger, 1988.

Clams, Snails, and Squid: Phylum Mollusca, Class Pelecypoda

Clams, Snails, and Squid: Phylum Mollusca, Class Pelecypoda johncallahan Fri, 07/31/2009 - 10:36
Body

Phylum Mollusca
Class Pelecypoda
Pelecypods have two shells, or bivalves, that protect the soft parts of the animal. The valves are generally of equal size (except in groups like the oysters) and shape and are hinged at the back. Some types, such as oysters, live in large groups that create beds or low-relief banks of shells, where the animals feed by filtering plankton and organic debris from the water. Other bivalves burrow through the mud or swim about in search of debris to eat. Many bivalve fossils in Delaware are preserved as steinkerns. Pelecypods are abundant in the spoils from the Mount Laurel Formation on both sides of the Canal in the vicinity of Reedy Point.

Photo Gallery
Reference(s)

Unless otherwise noted, photographs and figures are from DGS Special Publication No. 18, by E. M. Lauginiger, 1988.

Corals and Jellyfish: Phylum Cnidaria

Corals and Jellyfish: Phylum Cnidaria johncallahan Tue, 07/14/2009 - 12:37
Body

Cnidarians are soft-bodied animals that include corals, jellyfish, and sea anemones. These soft-bodied animals have saclike digestive cavities and tentacles containing rows or stinging cells used for defense and capture of food. Many secrete calcium carbonate to support and partly enclose the soft parts; the most familiar of these are corals. The only members of the phylum found at the Canal are solitary corals. One of these corals, Micrabacia, may be the most common fossil found. Another common fossil found there, a solitary horn-shaped coral, has been given different names by different authors.

Reference(s)

Unless otherwise noted, photographs and figures are from DGS Special Publication No. 18, by E. M. Lauginiger, 1988.

Insects and Crustaceans: Phylum Arthropoda

Insects and Crustaceans: Phylum Arthropoda johncallahan Fri, 07/31/2009 - 11:08
Body

Phylum Arthropoda
Arthropods are animals with a segmented body, external skeleton, and jointed appendages. The Arthropoda includes insects and crustaceans. Only two groups of arthropods are common as fossils in the Cretaceous of the C&D Canal area, and both are types of crustaceans: the Malacostraca (crabs, lobsters, and shrimp) and the microscopic Ostracoda.

The most common crustacean fossils come from the ghost shrimp Callianassa. Pieces of the claws and pinchers are the most common body parts found; only around the area of the Deep Cut have complete appendages been found. More common than body parts are the burrows of this shrimp, which occur as lumpy tubes called called Ophiomorpha nodosa. These "trace fossils" are very common in the Englishtown and Marshalltown formations.

Occasionally, small crabs (Tetracarcinus subquadratus) or fragments of lobsters (Hoploparia gabbi) are found on some of the spoil areas from the Merchantville and Marshalltown Formations.

Ostracodes can be collected by studying the sand-sized residue from screenings of the Mount Laurel Formation.

Reference(s)

Unless otherwise noted, photographs and figures are from DGS Special Publication No. 18, by E. M. Lauginiger, 1988.

Lamp Shells: Phylum Brachiopoda

Lamp Shells: Phylum Brachiopoda johncallahan Mon, 07/20/2009 - 14:43
Body

Brachiopods are shelled invertebrate that look somewhat like bivalved molluscs. However, the animal living in the shell is a filter feeder that collects food with a special organ called a lophopore (bryzozoa also have lophophores).

Like clams, the brachiopod lives in a shell consisting of two hinged valves, but the orientation of the shells is different. Brachiopods have valves covering the top and bottoms of the animal that are of different sizes and shapes, but the left and right sides are are symmetrical (or mirror images to each other). In contrast, the valves of a clam shell are mirror images of each other, but the individual valves are asymmetrically shaped.

Brachiopods spend their adult life as bottom dwelling filter-feeders. They have generally decreased in abundance and diversity since the Paleozoic Era. Some types are fairly common, easy to identify, and are restricted to certain periods of time. These features make them important index or guide fossils. The brachiopod species Terebratulina cooperi is an index fossil for the Mount Laurel Formation in Delaware.

Reference(s)

Photographs from DGS Special Publication No. 18, 1988, by E. M. Lauginiger; DGS Special Publication No. 19, 1992, compiled by T.E. Picket and D.C. Windish; and DGS Report of Investigation No. 21, 1972, by T. E. Pickett.

Moss Animals: Phylum Bryozoa

Moss Animals: Phylum Bryozoa johncallahan Mon, 07/20/2009 - 14:38
Body

Bryozoans, sometimes referred to as "moss animals," are a type of simple colonial animal that mostly lives in marine environments (a few inhabit freshwater). Bryozoans feed by means of a lophophore, a small ring of tentacles covered with tiny cilia that are used to filter food from the water. Bryozoan colonies are protected with a covering of organic materials or calcium carbonate. Some calcium carbonate forms may be found as fossils in the Cretaceous strata near the C & D Canal.

Three species of bryozoans have been found in the spoils piles (refuse material from excavation of the canal) in the area of Reedy Point. The origin of these bryozoans is under much debate. Their occurrences are most commonly reported from the Mt. Laurel Formation. However, an alternative view is that many are from sediments of the overlying, Tertiary-age Vincentown Formation, which is exposed to the south - if so, they would have been washed into the eastern end of the Canal by the Delaware River and then dumped on the spoils with the other dredgings.

Reference(s)

Unless otherwise noted, photographs and figures are from DGS Special Publication No. 18, by E. M. Lauginiger, 1988.

Segmented Worms: Phylum Annelida

Segmented Worms: Phylum Annelida johncallahan Fri, 07/31/2009 - 11:01
Body

Phylum Annelida
Annelids are segmented worms. The remains of the soft-bodied segmented worms are not usually preserved as fossils. Some marine (salt-water) types, however, secrete tubes of calcium carbonate to use both as a home and to provide protection from their enemies. These tubes can be found as isolated specimens or attached to larger shells. Two genera, Serpula and Hamulus, are fairly common in formations near the C&D canal.

Reference(s)

Unless otherwise noted, photographs and figures are from DGS Special Publication No. 18, by E. M. Lauginiger, 1988.

Starfish and Urchins: Phylum Echinodermata

Starfish and Urchins: Phylum Echinodermata johncallahan Fri, 07/31/2009 - 12:53
Body

Phylum Echinodermata
Echinoderms are "spiny-skinned" invertebrate animals that live only in marine environments. Two major divisions are recognized by biologists: principally attached, usually stalked forms of the Pelmatozoa; and unattached free-moving forms of the Eleutherozoa.

Fossil Pelmatozoa are represented in Delaware by stem fragments or columnals from crinoids or sea lilies. Columnals belonging to the Cretaceous crinoid Dunnicrinus are common finds on the Reedy Point spoils. The calyx or head of this crinoid has not been found, probably because of its fragile nature.

Eleutherozoan fossils include a group of starfish-like, free-moving forms called brittle stars, and a group of armless spiny forms known as sea urchins. Complete sea urchins are rare and highly prized specimens. The most common finds along the canal are isolated spines and plates of sea urchins and small fragments of brittle stars.

Reference(s)

Unless otherwise noted, photographs and figures are from DGS Special Publication No. 18, by E. M. Lauginiger, 1988.

Vertebrates: Phylum Chordata

Vertebrates: Phylum Chordata johncallahan Fri, 07/31/2009 - 13:06
Body

Phylum Chordata includes the vertebrates. Although not as common as the invertebrates, teeth and bones from different classes of vertebrate animals can be found at Canal sites.

Chondrichthyes, or “cartilage fish,” include the sharks, skates, and rays. Teeth and vertebrae from these animals are the most common types of vertebrate fossil found. They may be found on the surface of a rock outcrop or in various spoil piles.

The most commonly found shark teeth belong to the extinct shark Squalicorax. These broad and serrated teeth are easy to identify to the genus level, but it is more difficult to distinguish between the species. Teeth of the goblin shark, Scapanorhynchus, are the largest shark teeth found at the Canal, with some specimens reaching over two inches in length. The teeth of this shark have caused workers much confusion because teeth from different parts of the mouth have different and distinct shapes. At one time there were three different names given to the teeth of this single shark species.

Osteichthyes, or “bony fish,” are represented by the dagger-like teeth of the Cretaceous predator Enchodus. Single, isolated teeth and small sections of the jaw with teeth still attached are relatively common finds. Teeth from other bony fish include Anomoeodus and Stephanodus. Vertebral columns of bony as well as cartilaginous fish are also found on the spoil piles.

Reptile remains are rare and thus the most treasured finds from the Delaware Cretaceous. Teeth of the sea-going reptile Mosasaurus and fragments from the upper and lover shells of turtles are the usual finds. Most collectors have to hunt for years before they find a single mosasaur tooth.

Photo Gallery
Reference(s)

Unless otherwise noted, photographs and figures are from DGS Special Publication No. 18, by E. M. Lauginiger, 1988.

Miocene Fossils of Pollack Farm

Miocene Fossils of Pollack Farm johncallahan Fri, 06/25/2010 - 10:24

Miocene Fossils Overview

Miocene Fossils Overview johncallahan Tue, 07/14/2009 - 13:03
Body

The Pollack Farm Site, located in Kent County, Delaware, is named for a borrow pit on the former Pollack property that was excavated during 1991 and 1992 for road material used in the construction of Delaware State Route 1. While Delaware Geological Survey staff collected earth minerals during construction of State Route 1, they came across an upper shell bed full of molluscan fossils. As digging continued, numerous fossils of various species and phylum were found. The fossils discovered range from a simple Arthropod, small insect, to large vertebrates, such as sharks. By 1993, the pit was back-filled, graded, and developed into a wetlands mitigation site.

The Delaware Geological Survey has created this web page to provide a resource of facts and photos of the numerous fossils found in central Delaware. The site includes links to four main phylum, which lead to fossil photographs containing brief descriptions.

In designing this website we hope to provide you with information that will be both educational and enjoyable!

Latitude
39.24
Longitude
-75.58
Set Cover Image?
On

Bivalves: Phylum Mollusca, Class Bivalvia

Bivalves: Phylum Mollusca, Class Bivalvia johncallahan Tue, 07/14/2009 - 14:06
Body

Clams, mussels, oysters, and scallops are members to the class Bivalvia (or Pelecypodia). Bivalves have two shells, connected by a flexible ligament, which encase and shield the soft vulnerable parts of the creature. All 15,000 known species of bivalves are aquatic in nature, with close to 80% being marine (saltwater environments).

Living at the bottom of the marine environment bivalves tend to either swim using their mantle cavity to force water movement, burrow into the sand, or attach themselves to an object with sticky strings called "byssal threads."

Below is a list of notable Bivalve species found at the Pollack Farm site.

  • Dallarca sp.
  • Astarte distans
  • Astarte sp.
  • Cyclocardia castrana
  • Glossus sp.
  • Iphigenia sp.
  • Caryocorbula subcontracta

Click the image or the link below to view the bivalvia collection!

Latitude
39.24
Longitude
-75.58
Reference(s)

Photographs from DGS Special Publication No. 21, 1998, R.N. Benson, ed.
Top left image: http:/commons.wikimedia.org/wiki/File:Cockle.jpg

Set Cover Image?
On

Snails and Slugs: Phylum Mollusca, Class Gastropoda

Snails and Slugs: Phylum Mollusca, Class Gastropoda johncallahan Tue, 07/14/2009 - 13:51
Body

The Class Gastropoda (in Phylum Mollusca) includes the groups pertaining to snails and slugs. The majority of gastropods have a single, usually spirally, coiled shell into which the body can be withdrawn. The shell of these creatures is often what is recovered in a fossil dig. Gastropods are by far the largest class of molluscs, comprising over 80% of all molluscs.

The presence of gastropods, at the Pollack site, provides evidence to validate the researchers beliefs that, years ago, the environment was of shallow-water, near-shore locality.

Below are a few notable taxa recovered from the Pollack Farm site.

  • Gastrapoda:
  • Turritella cumberlandia
  • Diastoma insulaemaris
  • Epitonium charlestonensis
  • Urosalpinx cumberlandianus
  • Tritonopsis ecclesiastica
  • Nassarius sopora
  • Oliva simonsoni
  • Inodrillia whitfieldi

Click the image or the link below to view the gastropod collection!

Latitude
39.24
Longitude
-75.58
Reference(s)

Photographs from DGS Special Publication No. 21, 1998, R.N. Benson, ed.
Top left image: http:/commons.wikimedia.org/wiki/ File:Orange_slug.jpg

Birds: Phylum Chordata

Birds: Phylum Chordata johncallahan Fri, 07/31/2009 - 13:58
Body

The lower Miocene Pollack Farm Fossil Site has yielded few avian fossils in comparison to the other classes of vertebrates and invertebrates. Only eleven fossil fragments, assignable to six taxa, were collected at the Pollack site. Of the eleven avian fossils collected, representations from three distinctive orders were recovered: Gaviiformes (divers and loons, seen below), Charadriiformes (gulls and shore birds), Pelecaniformes (cormorants and pelicans).

Fossil fragments such as the proximal end of right scapula(order Charadriiformes), Middle trochlea of left tarsometatarsus (order Pelecaniformes) are some of the few materials paleontologist were able to gather.

Other taxa represented include:

Gavia small sp. (1 specimen and possibly another) Morus cf. M. loxostylus (5 specimens)
large species of pseudodontorn (1 specimen)

Although the number of remains is relatively small to other phylum and classes collected, the groups importance can not be undermined due to the information they provide in explaining the past environment of the lower Miocene bed. Because the majority of the birds represent groups that are largely or entirely marine, it further strengthens the hypothesis that the lower Miocene formation was once a near shore area of an embayment.

Click the image or the link below to view the avian fossil collection.

Latitude
39.68
Longitude
-75.75
Reference(s)

Photographs from DGS Special Publication No. 21, 1998, R.N. Benson, ed.
Top left image: http:/commons.wikimedia.org/wiki/File:TringaSemipalmata_3897.JPG

Fish: Phlyum Chordata

Fish: Phlyum Chordata johncallahan Mon, 07/20/2009 - 12:34
Body

While sampling the lower Miocene Calvert Formation at the Pollack Farm Site, 30 fossil fish taxa were collected, consisting of 24 cartilaginous and 6 osteichthyes fishes. The fossils found in the lower Miocene bed have similar characteristics to an equally aged Formation in southern Delaware suggesting deposition occured in a subtropical, shallow-water, near shore environment.

The early Miocene Fish fossils found in Delaware are of two kinds, Chondrichthyes(consisting mainly of Sharks and rays) and Osteichthyes(commonly known as bony fish).

Paleontologists, at the Pollack Farm, were able to collect a large number of teeth and vertebrae from Chondrichthyes. However, because their bodies do not contain a true bone, full body fossils are very rare to find.

Osteichthyes, differ than Chondrichthyes, in that their skeleton is made of a stiffer bone, compared to their cartilaginous counterparts. Osteichthyes are often associated with dagger-like, isolated teeth

The stingray, dayatis americana, (shown above) is just one of the many Chondrichthyes and fish fauna found at the Pollack Farm Site, in Delaware! Click the image or the link below to view the fish collection.

Latitude
39.24
Longitude
-75.58
Reference(s)

Photographs from DGS Special Publication No. 21, 1998, R.N. Benson, ed.
Top left image: http:/www.pbs.org/oceanrealm/seadwellers

Insects and Crustaceans: Phylum Arthropoda

Insects and Crustaceans: Phylum Arthropoda johncallahan Mon, 07/20/2009 - 12:19
Body

The majority of Arthropods recovered at the lower Miocene bed are from various species of crustaceans (lobsters, shrimp, barnacles). Fossils from crustaceans often consist of small body parts such as claws. However, crustaceans such as ghost shrimp (callichirus) tend to construct burrows that resemble lumpy tubes called Ophiomorpha. These corn-stalked resembling tunnels, are created from mud and depository waste to form burrows in which the creatures reside. In comparison to claws and pincher fossils, "trace fossils", such as Ophiomorpha tubes, are often commonly found in greater number than that of various body parts.

Arthropods include an exceedingly diverse group of taxa such as insects, crustaceans, spiders, scorpions, and centipedes. There are more species of arthropods than species in all other phyla combined. The name Arthropod means "jointed foot." All arthropods have segmented bodies and are enclosed in a jointed, protective armor called an exoskeleton. Most arthropods have a pair of compound eyes and one to several simple ("median") eyes or ocelli.

In addition to shrimp and other shellfish, barnacles are commonly found in the lower Miocene bed. Barnacles are separated into two groups sessil and stalked. Both have soft bodies that are protected by an outer wall, which resembles either an acorn (sessil) or stalk. Living in a tight grouping with other barnacles these creatures attach themselves to any suitable surface (rocks, boats, even whales and turtles!) in effort to aid in reproduction.

The trace fossils for Arhtropods found at the Pollock Site include Ophiomorpha nodosa (burrow tubes dug by shrimp) and Skolithos linearis (burrow tubes left by ground-dwelling insects).

Click the image or the link below to view the Arthropod collection.

Latitude
39.24
Longitude
-75.58
Reference(s)

Photographs from DGS Special Publication No. 21, 1998, R.N. Benson, ed.
Top left image: http:/www.pbs.org/kcet/shapeoflife/animals/arthropods4.html

Land Mammals: Phylum Chordata

Land Mammals: Phylum Chordata johncallahan Fri, 07/31/2009 - 14:18
Body

Land mammal fossils were discovered in 1992 in the lower part of the Calvert formation at the Pollack Farm site. During the short time the pit was open, the collection grew to become the most diverse tertiary land mammal fauna known north of Florida on the eastern half of North America.

The gathering, collected from the lower Miocene formation, includes at least 26 species representing at least 17 families in 7 orders (listed below).

Orders:

  • Soricomorpha (Shrews, moles)
  • Erinaceomorpha (Hedge hogs)
  • Chiroptera (Bats)
  • Rodentia (Rats, mice)
  • Carnivora (Bears, wolves)
  • Perissodactyla (Rhinoceros, horses)
  • Artiodactyla (Deer)

The Collection of Miocene land mammal fossils, especially north of Florida, is relatively minimal. Only four localities distancing between Georgia and New Jersey yielded significant Miocene fossil beds. Although single teeth and parts of postcranial elements represent the majority of land mammals of the Pollack Farm local fauna, the sites diversity of species elevates the importance of the Pollack Farms location.

Click the image or the link below to view the Land Mammal collection!

Latitude
39.68
Longitude
-75.75
Reference(s)

Photographs from DGS Special Publication No. 21, 1998, R.N. Benson, ed.
Top left image: http:/www.hedweb.com/animimag/rhino.jpg

Marine Mammals: Phylum Chordata

Marine Mammals: Phylum Chordata johncallahan Fri, 07/31/2009 - 14:28
Body

The Pollack Farm Site, in the Cheswold sands of the lower Miocene Calvert Formation, produced a fragmentary marine mammal fauna. The Pollack location yielded at least six cetaceans (whales, porpoises), a sirenian(manatee), along with one of the earliest records of a true seal (Listed below).

Marine mammals have the same characteristics as all other mammals, but they have adapted or adjusted to life in the ocean. For instance, many species residing in the deep oceans have a thick layer of blubber, which holds their body temperature warm. Marine mammals also have greater amounts of blood than land mammals, in proportion to their body sizes. This feature allows the blood to be sent to vital organs that in turn slows the heartbeat and minimizes the use of oxygen allowing longer dives underwater.

Species:

  • Porpoises - Squalodon calvertensis, Phocageneus venustus, Zarhachis flagellator, Rhabdosteus, & kentriodontid
  • Sperm Whale
  • Manatee
  • Seal - Leptophoca lenis

The collections of marine mammals, from the Miocene Calvert, are less diverse and more fragmentary than the other phylum. However, the Pollack site does extend the marine mammal fossil record into Delaware, which thus validates findings from other locations.

Click the image or the link below to view the Marine Mammal collection!

Latitude
39.68
Longitude
-75.75
Reference(s)

Photographs from DGS Special Publication No. 21, 1998, R.N. Benson, ed.
Top left image: http:/www.seasky.org/reeflife/sea2k1.html

Reptiles: Phlyum Chordata

Reptiles: Phlyum Chordata johncallahan Fri, 07/31/2009 - 13:51
Body

The Pollack Farm Site has provided the first legitimate window of Miocene reptilian life in North America east of the great plains and north of Florida. In years prior to the excavation of the Pollack site, records of particular small lizards and snakes were non-existent in locations of the mid-Atlantic and northeast, thus providing a significant value to the Miocene fossils recovered.

The fossils recovered from the lower Miocene bed, have provided considerable information to the regions past ecology and environment. The fossils of crocodiles and aquatic turtles gives evidence to a large shallow lake or a river oxbow setting; furthermore, the remaining reptiles probably preferred open brush or grassy environments with loose or sandy soil.

The lower Miocene dig was responsible for the findings of a number of different orders and families of reptiles. Below is a list of species with their fossils recovered from the Pollack Farm Site.

  • Kinosternon sp. Mud Turtle(fragmentary costals, hyoplastra, hypoplastra)
  • "Chrysemys group" turtle. Painted turtle, cooter, slider group(nuchal, costals)
  • Geochelone sp. Very large land tortoise(Entoplastron, hypoplastron)
  • cf. Crocodylus sp. Very large crocodile (Tooth)
  • Ophisaurus sp. Legless Lizard (trunk vertebra)
  • Pterygoboa delawarensis. New species of distinctive small boid genus(trunk vertebra)
  • Calamagras sp. small boid (fragmentary vertebra)
  • Ameiseophis robinsoni. Extinct genus and species of small colubrid snake (trunk vertebra)
  • Pollackophis depressus. Distinctive new genus and species of small colubrid snake (trunk vertebra)
  • cf. Crotalinae. et. sp. Viperid snake (two vertebrae)
Latitude
39.68
Longitude
-75.75
Reference(s)

Photographs from DGS Special Publication No. 21, 1998, R.N. Benson, ed.
Top left image: http:/www.resalliance.org/projects/images/Geochelone.jpg