Shark Teeth Fossilization

Fossilized shark teeth are one of the few easily recognizable parts of a shark that fossilizes. The internal skeleton of sharks is cartilage and disappears soon after burial in sediments. The main exceptions are the teeth and dermal ossicles, which are the tiny hard sandpaper-like protrusions on shark skin. The central vertebrate can also become calcified and is occasionally fossilized. Cartilage does not mineralize like bones and breaks down much quicker than the hard parts of a shark. Teeth are the most common shark fossil, but sometimes the fossilized dermal ossicles and pieces of vertebrate are found in the same sediments. The dermal ossicles are tiny and are not as easy to identify as the shark teeth.

Permineralization

Shark teeth become fossils through permineralization. Permineralization can happen with other organisms including crab fossils on Florida beaches. This results when minerals dissolved in water fill the open spaces of an organism or organic tissue, and eventually, only the minerals remain. When a shark loses a tooth or a shark dies, the teeth and the shark sink to the bottom and may be covered by sediments. Teeth or sharks that are not buried, such as those that settle on a rocky bottom or in fast-moving water, will disintegrate. The buried sediment provides an anaerobic, or oxygen-deficient, environment and this preserves the tooth or other hard parts of the shark.

Over time the sediment accumulates and the pressure from the sediments pushes water with dissolved minerals into the tooth. Eventually, the minerals crystallize, and the tooth is nearly entirely replaced by silica and other elements including phosphorous, iron and calcium. The buried sediments are later subjected to tectonic forces and eroded, which exposes the sediments with the shark teeth and other fossils. This mineralization requires lots of time. Fossil shark teeth generally range in age from 75 million to 10 thousand years, and the best way to determine the age of a shark tooth is to know the age of the geologic formation that hosted the fossil. The permineralization process also turns the fossil shark teeth black or dark gray, which makes them much easier to spot in sands along the beach.

The Fossil-Rich Aquia Formation

Shark teeth and other fossils at the Purse area are found in the Aquia Formation. The Aquia Formation is composed of clayey, silty, glauconitic sands and has some areas that are rich in invertebrate fossils. The Aquia Formation was deposited during the Paleocene Epoch, which was approximately 59 to 55.5 million years ago. The Aquia Formation is much older than the sediments at Calvert Cliffs on the eastern Maryland shore along the Chesapeake, which is another shark tooth collecting region in Maryland. The Calvert Cliff fossils are within the Chesapeake Group, and were deposited during Miocene Epoch, which was 23 to 5 million years ago. The fossils along the Calvert Cliffs are much younger than those of the Purse area.

In southwestern Maryland, the Aquia Formation is best exposed in cliffs along the Potomac and along streams that have cut into the formation. The cliffs along the Potomac are unstable and are constantly eroded. This exposes more sections with shark teeth and other Paleocene fossils.

Purse Area Beaches

The Purse area is remote but the roads to get to the site are all paved. The area is reached by taking State Route 224, also known as Riverside Road, which bisects the Nanjemoy WMA. The trailhead parking area is clearly marked with a sign that says it is part of the Nanjemoy WMA. While parking at the trailhead is limited, it is possible to park on the sides of the road south of the park. Parking is limited in these areas, and collectors may have to walk up to one-quarter of a mile to get to the trailhead on busy days.

The trail from the parking area to the beach is flat and well-defined, and collectors will not get lost if they continue to walk westward to the beach. Since the area is relatively remote, there are no nearby restrooms or places to eat. Visitors should bring lunch and plenty of drinking water. It is important to come prepared, as anyone that leaves will quickly lose their parking space and miss out on time spent on the beach.

Purse Beach Advantages

The Purse area beach is narrow, and it is tough to find a good space to sit for lunch or relax when not collecting if the beach is crowded. It becomes much narrower during high tide. Like most beaches, it gets the most use on weekends, but people can show up during the work week.

Purse Beach has another big advantage for fossil collectors and other visitors. The beach faces west, so it has sun until it gets dark. This is a big contrast to the beaches at the Calvert Cliffs on the eastern side of Maryland, which face to the east. The sun quickly goes below the cliffs by late afternoon, and the collecting sites in eastern Maryland become cold and much darker, which makes it more difficult to find shark teeth.

Finding Shark Teeth

Shark teeth, as well as fossil dental plates of rays, are found directly on the surface of the sand and gravel along the beach and along the water line. Some collectors use a small shovel or trowel to dig into the beach gravel and then use a screen to examine the sand and gravel for shark teeth. A metal colander or similar screen can be used for screening, but it is important to have the holes sized correctly. If the holes are too big, some of the smaller teeth will pass through the holes, and if they are too small, they will not screen the sand. Generally, holes should be at least one-quarter inch in diameter. Some collectors also make their own screens with wire screen and wood from their local hardware store.

Walking along the beach and scanning the water line for shark teeth and other fossils is productive for many collectors. Low tide is best for collecting, and it is easy to find the tide tables online. The beach is continuously washing and reworking the sand, and shark teeth and other fossils can be easily spotted on the surface. Shark teeth and ray plates are black and are easy to see in the brown sand and gravel. The sharply pointed shape of a black shark tooth also stands out against the sand and gravel. The ray dental plates have a rectangular shape and are also black.

Tiny Teeth

Many of the shark teeth and ray plates along Purse Beach are tiny and sometimes less than one-quarter inch. Larger teeth are found with the smaller teeth, so any area with teeth may also reveal larger teeth. The largest teeth range up to about one inch long. The teeth at Purse are generally pointy and curved, in contrast to some of the large triangle-shaped teeth found at other shark teeth localities. Many of the teeth found in the Purse area are extremely narrow with sharp points, and these are reportedly from Scapanorhynchus, which is an extinct genus of shark that is like the living goblin shark.

Walking on the beach is safest with shoes. There is potential for broken glass, but the biggest threats to bare feet are small pieces of sharp pointed driftwood. The beach near the trail that leads from the road is generally open and easy to hike. If carrying a phone or camera it is better to stay on land, as some of the water is more than waist deep, and there is always the potential to slip or trip in the water.

Turritella Fossils – A Bonus

Small cliffs are present north of the trail where it reaches the beach. Fossils are abundant in the rocks exposed in this area, and many of these are turritella, which are tightly coiled sea snails that are shaped like a narrow cone. Most of the fossils are weathered and crumble when touched, but some of their casts are intact. Some of the interiors of the turritella are preserved by fine mud that has filled their interior spaces. The mud solidified and remained intact long after the original shells had eroded. These casts are like a negative of the original animal’s shell.

Turritella is a genus of medium-sized sea snails. They have coiled shells that resemble an elongated cone. The name comes from the Latin “turritus” which means turreted or towered. The Latin diminutive suffix “-ella” means small. Turritella fossils are worldwide and range in age from the Cretaceous to recent periods. Turritella agate is a beautiful specimen and lapidary material.

Where to Find Turritella Fossils

South of the trail along the beach is a small point on the Potomac River. This is just south of a swampy area that drains into the river. The cliffs become steeper south of the swampy area and many trees have fallen and block the beach path. Sections of the cliffs have collapsed and are on shore. This area is difficult to access and will require climbing over fallen trees and wading into the water.

This area has huge outcrops of the Aquia Formation, and in some sections, the entire rock is made of fossils. The fossils are easy to see as they are generally white against the brown-to-black background of the sandy shale matrix. The outcrops have turritella and bivalve fossils, and many of them are solid and are found as loose pieces next to the outcrops and the large boulders. The large blocks that have fallen from the cliffs are often loaded with fossils, and the matrix material is relatively soft. Digging in the cliffs is illegal, as this leads to increased erosion and is dangerous in areas with overhangs. Many of these fossils are turritella casts, and large rocks with distinct turritella casts are found in this area. While shark teeth are certainly present along the beach near the cliffs, the shoreline is so rocky that it is difficult to find teeth in this area.

Getting to Purse and GPS Coordinates

Purse is reached by taking State Route 224, which roughly follows the Potomac River shoreline in southwestern Charles County. State Route 224 is also known as Riverside Road. The parking area is marked with a sign that says “Nanjemoy Wildlife Management Area.”

The following are key GPS coordinates obtained from Google Earth:

• Parking area at trailhead: 38°25’56.33”N, 77°15’6.28”W

• Beach area at end of trail: 38°25’54.69”N, 77°15’23.34”W

• Southern outcrops with turritella fossils: 38°25’24.81”N, 77°15’40.00”W

The Purse area is accessible throughout the year, depending on the weather. Snow and ice are potential issues during the winter, and thunderstorms are a safety hazard, especially during periods of unsettled weather in the spring and summer. Families and advanced collectors will find that the Purse area offers the opportunity to collect both shark teeth and turritella fossils.

This story about fossil shark teeth previously appeared in Rock & Gem magazine. Click here to subscribe. Story & Photos by Robert Beard.

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Where to Find Fossil Fish – Dig Sites

Two sites outside the small town of Kemmerer, Wyoming, offer pay-to-dig. Just make an appointment or register, show up and they will take great care of you, showing you how to fish… with a hammer and chisel.

One site is the Warfield Quarry, also known online as Fossil Safari, and the other is the American Quarry.

While visiting the pay-to-dig sites in Kemmerer, it is a must to travel a short distance away to the Fossil Butte National Monument. Sorry no collecting here, but the museum boasts a tremendous variety of animals and plants from the Green River Formation. Cut unobtrusively into the hillside, the visitor center is filled with wonderous fossils, a great compilation of the ecosystem 50 million years ago.

The Green River Formation

Pay-to-dig sites are part of the Green River Formation where there are hundreds, no, thousands of fish trapped in rock that was once a series of fairly shallow lakes. Streams and rivers drained the surrounding mountains enabling the formation of this special fossil location.

The Green River Formation is known as a lagerstatte, which loosely translated from German means “storage place.” The area butts up against the limestone of the Wasatch, Unita, Wind River and other mountain ranges. It is an area where fabulous and spectacularly preserved fossils including plants and animals represent a snapshot of life living within that ecosystem.

When & How was this Site Made?

The Eocene period, about 53 to 48 million years ago, was a transition from a warm and moist environment to one that was hotter and drier. This is evidenced by some of the fossil finds in the area. Palm fronds, crocodile and sycamore leaf remains point to a warm moist environment and deciduous tree leaves point to a drier climate. The mountains were partially made up of limestone. During heavy rains, water would run down into the streams and rivers bringing with it sand, mud and silt sediments filled with dissolved minerals such as calcium oxides, inorganic elements and calcium components.

This would wash into the lakes fouling the water, making it turbid and in some cases changing the pH levels. At times the change in the chemical composition of the water was detrimental to the life forms in it.

Fish would die along with many of the other creatures and become buried in the silty sediments. Paleontologists can tell by looking at the various layers, which were deposited during times of drought and which were deposited in times of flood. It is also possible by studying the cross-section of the quarry where the best location is to find fossil fish.

The spectacular fossilization and completeness of the fossil fish is because they were buried quickly. Even the bottomfeeding scavengers were not quick enough or did not survive to disarticulate the bodies of the dead fish. The sediments filtered down to the bottom of the lake and covered the creatures with thin layers. It is within these layers that spectacular fish specimens may be found.

Where to Find Fossil Fish – Digging

In specific horizons, one of which is called the split fish layer, a finely laminated limestone is present that entombed many fish. This is easy to split and if the rock contains a fossil, it splits so that you can easily see it in both a positive fish fossil and also a negative impression. The fish are beautifully preserved with bones, gill covers, ribs and even scales intact. In some cases, a bit of matrix, the limestone that clings to the fish skeleton, is still present. It is quite easy to remove. In many instances, all that is needed is a dental pick, or a pin vise to gently remove excess rock matrix. You must be very careful not to go too deep into the limestone so it’s best to attack it at an acute angle.

This limestone is so fine-grained that many plants and insects that fell into the water or were washed in from rivers and streams are also seen in spectacular detail.

In some areas birds, reptiles, turtles and even crocodiles may be found all preserved in exquisite detail.

This story about where to find fossil fish previously appeared in Rock & Gem magazine. Click here to subscribe! Story and photos by Joseph “PaleoJoe” Kchodl.

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Beautiful Petoskey Stones

Walking along the northern Lower Peninsula shorelines of Lake Huron and Lake Michigan, it is easy to see this fossil’s natural attraction on people. Looking into the water, one can sometimes see this coral, rounded by relentless waves, worn smooth showing its beautiful internal structure. It is easy to see that rockhounds, jewelry makers and almost everyone would be taken by this attractive fossil.

Once removed from the water, however, it quickly dries and loses its bright polished shine. To achieve that permanent shine, it is necessary to polish the rock by grinding and sanding it and finishing it with a polishing compound to bring out the beautiful luster of the stone.

What Corals Make Petoskey Stones?

Petoskey stones are fossilized corals. There are at least nine species of Hexagonaria, but the only true Petoskey Stone is the H. percarinata. These corals are marine organisms that are made up of many, sometimes thousands of hard calcium carbonate exoskeletons called corallites. Each corallite contains a polyp – an individual multi-cellular animal.

There are two major types of corals – solitary corals growing by themselves, and colonial corals, growing in a tight community of genetically identical polyps. The polyp is the actual living individual creature that inhabits each corallite. As the coral grows, it extends the calcium carbonate exoskeleton and seals off part of the base.

Symbiotic Relationships

Corals live in a symbiotic relationship with a variety of marine algae. Although corals have stinging tentacles and are able to capture food such as zooplankton, the algae provide the energy corals need to survive.

Food is captured by tentacles and brought down to the center where the mouth and stomach are located. The algae use a process called photosynthesis to provide additional energy to the coral polyp. In turn, the hard calcium carbonate exoskeleton of the coral and stinging tentacles provide protection for the algae.

The coral polyp produces waste products that the algae needs for its survival. Because sunlight is needed for the algae’s photosynthesis processes and sunlight only penetrates the ocean to a certain depth, corals normally grow in shallow waters from 30 to 150 feet.

Hexagonaria Coral

Hexagonaria coral is a colonial marine animal that lived in warm shallow salt-water tropical seas. Prehistoric Michigan was once such an environment. During the Devonian Period some 419 -358 million years ago, Michigan was located much closer to the equator.

Much of Michigan’s bedrock is made up of huge limestone beds that underlie the surface soil. These large tracts of limestone bedrock are the remains of ancient coral reefs that filled the sea that once covered what is now Michigan. Ancient coral seas were full of a variety of creatures that included but were not limited to, corals -both solitary and colonial.

Each corallite of the Hexagonaria is made of a sometimes five but usually six-sided compartment which adjoined the others in the colony and created the elaborate six-sided hexagon. The radiating lines one sees in the Petoskey Stone are the septa and theca. The septa are the lines of division between each corallite and the theca are the internal radiating lines. These patterns of hexagon shapes and radiating lines are what will gives the Petoskey Stone its uniqueness among rocks.

Finding Petoskey Stones

The Hexagonaria are found across Michigan along lakeshores and rivers in the sediments commonly called the Traverse group. They are rounded fragments of the coral Hexagonaria. Some of these coral reefs still lie beneath the ground and some under the water of Little Traverse Bay.

Because of the wave and abrasive action of the sand, these stones are rounded and washed up on the beach. The action of ice moving also brings these stones into shallow water. The best time to hunt for Petoskey stones is in the spring as soon as the ice melts. But beware, it is a cold time to search! I have seen locals donning dry suits and walking in waist-deep water as ice floats by and picking up the stones before they even reach the shore.

How Did Petoskey Stones Get Their Name?

The name Petoskey is said to come from an old Odawa Indian legend. It is said that a French fur trader, Antoine Carre, came to Michigan traveling extensively in the area now known as Petoskey where he met and married an Odawa princess. In time, he was adopted by the local Odawa tribe and eventually was made their chief.

It is further told that in the spring of 1787 traveling with his wife on his way from near present-day Chicago, he camped near what is now Kalamazoo. During the night, his wife gave birth to a son. Legend says that as the morning sun rose, the sun’s rays fell upon the infant’s face, and his father pronounced his name shall be Petosegay. The translation of the Odawa Petosegay means sunbeam or rising sun or rays of dawn.

Petosegay became a fur trader like his father and also became quite wealthy. He owned much land in the Petoskey area, and a community was settled on the shores of Little Traverse Bay. The present location of the city of Petoskey stands as a tribute to Petosegay. Because these rounded and water-tumbled fossils were found in great abundance on the shores of Little Traverse Bay, they became known as Petoskey stones.

Becoming a State Stone

The Petoskey stone was made the state stone of Michigan by legislative action. Then-Governor George Romney signed House Bill 2297 in 1965. This legislation elevated this fossil to the prestigious position it now holds around the world. For visitors to the Great Lakes, a Petoskey stone find is often a must-do!

This story about Petoskey stones appeared in the September 2021 issue of Rock & Gem magazine. Click here to subscribe! Story by Joseph “Paleo Joe” Kchodl.  

The post Petoskey Stones: Where & How to Find Them first appeared on Rock & Gem Magazine.

The story of “ghost crabs” is unique. Crabs are so rare as fossils that they are a prized find. Crabs and other crustaceans have a hard carapace or external shell. This exoskeleton is thin and fragile and falls apart immediately upon death. These discarded shells break into small pieces when washed up on the beach or are broken apart in the tides and currents. But in the case of the ghost crabs, they are found essentially complete. Locals along the line from Eau Gallie Causeway to Pineda, Florida, call these fossils stoned crabs, beach crabs and coquina crabs.

What is Coquina?

Coquina is a sedimentary rock formed almost entirely of ground-up fragments of shells from mollusks and other invertebrates and cemented with grains of sand.

The rich history of Florida’s geography is replete with the advancing and receding of coastline along with fluctuating sea levels. As these shorelines moved, animals died and were buried. Florida also boasts coquina deposits inland that can also be found full of fossils. Florida can be a fossil hunter’s dream!

How Did Whole Fossils Form?

Because of the shape of these crab fossils with their claws folded in front of them as in life, it is believed that these crabs died in their burrows perhaps to escape a winter chill or a quick fall in temperature. When they died in their burrows there was no disarticulation, they remained virtually intact. They then mineralized along with the sand and shell rubble that surrounded them.

The crabs fossilized by the same process that created those ancient coquina rock formations on land in East Central Florida. These coquina deposits are approximately 110,000 years old. Due to offshore dredging, fossils get washed up on the shores of Florida’s beaches. Normally anything washing up on a beach is pulverized rapidly by the incessant waves or abraded by the beach sand. Such is the fate of the ghost crabs of Brevard County – if not found quickly enough.

The crabs are generally covered with a thick layer of heavily cemented sandy matrix. If the crab has been in the surf for quite some time, it can be highly abraded, worn and even slightly polished. Some of the voids between the claws and legs can be infilled with calcium grains, calcite crystals and cemented sand.

Florida’s Coastline

Along Florida’s coast, the barrier island and sand dune system is believed to have formed within the last 7000 years. It is also believed that the crabs could have accumulated over the last 100,000 years. The sandy beaches are smooth and clear of debris during most of the year and it is particularly after hurricanes and strong storms that these crabs wash up on shore and can be easily found. They are rare but usually widely scattered along the beaches.

These crabs are believed to come from two sources of offshore coquina rock deposits to the east which appear to be the ancient shoreline before the retreat of the last Pleistocene Ice Age some 10,000 years ago.

It’s also believed that during the construction of Port Canaveral 70 years ago that dredging activities dislodged much of the Anastasia formation releasing some of these fossils from their long slumber.

Beachcombing is fun and now beachcombers can also be fossil hunters looking for that elusive megalodon tooth…or maybe even a ghost crab.

This story about Florida beach crab fossils previously appeared in Rock & Gem magazine. Click here to subscribe. Story by Joseph J. “PaleoJoe” Kchodl.

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Rising from the Red Mountain in the center of the Lhasa Valley, Potala had been the winter palace of the Dalai Lama since the 7th century. Rockefeller sketched its grandeur on the back of an envelope that he shared years later as governor, with architect Wallace Harrison (designer of Manhattan’s Rockefeller Center). He envisioned a modernist plaza, similarly built atop a three-mile-long escarpment of a 1,200-foot tall limestone cliff, with a panoramic view of four mountain ranges: the Adirondacks, Berkshires, Green Mountains and Taconics.

Fortunately for fossil hunters and geologists, Rockefeller’s plans for urban renewal were nixed because of the area’s lack of proximity to the city or downtown state offices.

Today, preserved within John Boyd Thacher State Park, the Helderberg Escarpment’s incomparable fossils and limestone layers share the story of land once covered by a shallow sea and brimming, for millions of years, with marine life.

By the Sea, The Sirulian Sea

The escarpment had inspired Rockefeller to think “up” (Heldeberg is Dutch for ‘clear mountain’) but savvy fossil and rock buffs will see how the good stuff starts at the bottom, where the “Cliffs Higher Than the Palisades” found their origin as a salty seabed.

The Erie Lowlands-Allegheny Plateau consists of flat-lying layers of sediment rock from the Late Silurian and Devonian periods, 420-380 million years ago.

The oldest are the rocks of the Upper Silurian (dolostones, evaporites and shales) and limestones of the Helderberg Group. These tell of a warm, shallow sea covering most of New York. Above a terminal dominated by carbon rock, an unconformity records the sea’s retreat and the beginning of erosion to the exposed Helderberg Group.

Helderberg Workshop, a nonprofit organization at the foot of the escarpment, says the exposed cliff was “essentially the shore of an ancient sea,” a vertical stretch of sedimentary rock, laid down by the ebb and flow of water over half a billion years, that by the 1800s was destined to become a world-famous geological landmark and hotbed for the scientific query.

Fantastic Fossils

Helderberg Escarpment fossils chronicle a geological history that began intriguing scholars worldwide in the early 19th century. So, when you go, don’t miss a stop by the Thacher Park plaque erected in 1933 to 16 great inquiring minds that found inspiration and information there: “In memory of those pioneer geologists whose researches in the Helderbergs from 1819 to 1850 made this region classic ground.”

Among them: American geologist Amos Eaton (1776-1842), founder of the modern scientific prospectus in education; Eaton’s surveyor and mineralogist, James Eights; paleontologist James Hall (1811-1898), discoverer of the first North American fossil reefs; William W. Mather (1804-1859) author of The Geology of New York-Part IV; and Sir Charles Lyell, a Scottish Baronet (1797-1875), whose evolution uniformitarianism posited that the formation of the Earth’s crust was through small changes, occurring over vast periods, according to known natural laws.

Fossils here include brachiopods, coral, crinoid stems, cystoids, and trilobites. Brachiopods have hard “valve” shells on their upper and lower surfaces (unlike left/right placement on bivalves) and include nearly 30,000 fossil species with less than 400 surviving today.

Crinoids mislabeled “sea lilies,” are not plants but animals, with a calyx (skeleton) that provides a stony anchor to hold it fast to a sea floor.

And who doesn’t love a good trilobite?

Certainly, Charles Emerson Beecher did who wrote, in 1893 in the American Journal of Science, “Attention has been called to the perfection of fossils in the siliceous limestones from a limited locality in the Helderberg Mountains. Proper collecting yields quantities of the most delicate and exquisitely preserved remains. The conditions of preservation are such that not only are large and strong species preserved, but also the smallest and young of many in all stages of growth.”

Indian Ladder Trail is probably the park’s most popular hiking choice. It was named after native trails that originally traversed the escarpment that led to settlements in the Schoharie Valley and later, during the Revolution, to caves providing refuge for loyalists. Look for dark grey-to-black chert nodules (silica-rich lumps originating from the diagenesis of shelled organisms), which were used as arrowhead material by local indigenous nations. Thin grey, black, or brown shale beds along the trail hold small mollusks and snails. Look up and you may find brachiopods, crinoid stems, and (if lucky) a black, dime-to-quarter-sized trilobite or two.

Thank You, Mr. & Mrs. Thacher

Who were John Boyd and Emma Treadwell Thacher, and why is a park protecting a half-billion-year-old geologic treasure named after them?

The interest originally generated in the cliffs by the scientific community — leading one to call the Helderbergs “a key to the geology of North America” – began attracting tourists. The bucolic mountain valley below the escarpment started, thanks to a burgeoning Delaware & Hudson Railroad, to look like an uncomfortable plethora of boarding houses, hotels and campgrounds.

Enter former Albany mayor and state senator, J.B. Thacher (1847-1909). In 1906, he and Emma Treadwell Thacher (1850- 1927) began acquiring property along the escarpment to protect it from development.

The couple owned numerous ridge-top parcels before his passing three years later.

Thacher, an inveterate collector, also had an impressive array of autographs that included every signer of the U.S. Declaration of Independence, which Emma later donated to the Library of Congress.

She also donated 350 of their acres to New York State for a public parkland. In 1914, the legislature delegated management to the American Scenic and Historic Preservation Society (ASHPS) so that “the lover of nature, the geologist, the seeker for inspiration can here make interesting explorations of the wonders of nature…”

In 1924, when New York State passed a $15 million bond to develop a state park system, Thacher Park received $25,000 for development. The state park plan, which sought to link urban populations with scenic resources, called Thacher “the key park serving the Capital District.” This prompted plans for additional improvement and, by the 1960s, its parking lots “accommodated record-breaking weekend crowds.”

By the mid-1990s, the Open Space Institute picked up where the Thachers had left off, identifying and acquiring more key parcels along the escarpment and conveying them to the state as additions to the park. In a decade, they more than doubled the park’s size.

Exploring Today

While collecting fossils is prohibited in state parks, you’ll find all the same opportunities for scientific inquiry and exploration of the natural world that has drawn visitors for centuries to one of the richest fossil-bearing formations found anywhere.

As recently as April 2022, Thacher Park was named a Best Of The Capital Region winner and “an adventure every time.”

Fossils are easy to spot on rocks in streambeds, in stone walls along the Overlook and in exposed rocks on the Cliff Top Trail.

Before you strike out on one of more than 25 miles of trails, check out the Visitor Center’s geological and historical exhibits showcasing the Helderberg Escarpment, and the panoramic Helderberg Room, a favorite spot for weddings and celebrations.

Outdoors, camping for tents or RVs is available at any of 140 sites at Thompson’s Lake Campgrounds. Sport climbing is available with a signed permit application.

A Wild Play Adventure Course has 60 aerial games, a 40-foot jump, and 15 zip lines. A New York State Park vehicle entrance fee of $6 is collected 9 a.m. to 5 p.m. daily, May 1-October 31.

In 1905 – half a billion years after a sea floor became a limestone cliff – Thacher wrote, “The writing of a man, it is held, is the most perfect relic he leaves behind.”

One visit to the geological and paleontological wonder that bears his name (and inspired a Rockefeller) and it’s fair to say that both underestimated the power and perfection, millennia after millennia, of the Helderberg Escarpment.

This story about the Helderberg escarpment fossils previously appeared in Rock & Gem magazine. Click here to subscribe. Story by L.A. Sokolowski.

The post Helderberg Escarpment Fossils first appeared on Rock & Gem Magazine.

Trilobites were arthropods with segmented bodies, paired jointed legs and an exoskeleton. Modern arthropods are made up of insects, spiders, millipedes and crustaceans.

The name Isotelus is Greek. Translated, isos means equal and telos means end. Isotelus was first described by John Locke in 1838. Locke was involved in the first serious study of the geology of Ohio in 1837 and 1838.

What are Trilobite Fossils? – Body Segments

The name trilobite derives from the three distinct body divisions or lobes running vertically through the body. There is one central or axial lobe with two pleural lobes on either side. It is also divided three ways horizontally into the head section or cephalon, the body section or thorax and the tail section or pygidium.

Some species had long projecting spines emanating from various segments. In the case of Isotelus, it had long spines radiating backward from the sides of the head section, called genal spines. The head and tail sections were solid shields while the body was made up of individual segments, each with a corresponding pair of legs and gill branches.

Body Armor

Some species had as few as two body segments while others had as many as 60. Isotelus had eight body segments. With these segments, the trilobites were able to “enroll” or roll up their bodies, much like the modern-day pill bug or roly-poly. It is with this action called conglobation that they were able to pull the soft body tissues in for protection from danger.

They were covered by a thick exoskeleton, a skeleton on the outside of the body protecting the soft tissues including legs, gill branches and antennae. It also protected them from danger be it storms or predators.

What are Trilobite Fossils? – Fossil Remnants

It is this exoskeleton that is found as a fossil. To grow, trilobites would have to shed or molt their exoskeleton. While molting they would grow a bit and then the new exoskeleton would harden and they would continue on their way. In many cases, it is discarded and disarticulated sections of the exoskeleton that are found as fossils.

Complete trilobites are not that common.

Trilobites Day-to-Day

Trilobites were the first major creature on earth with complex eyes and many lenses. The eyes generally were crescent-shaped and sat high on the head section. As such it can be imagined they had nearly 360-degree vision. Some species had thousands of lenses in each eye. Some species were blind and had no eyes.

They were creatures that scurried about on the ocean floor eating decaying plant and animal material much as their relatives the horseshoe crabs, lobsters and shrimp do today. They had a mouthpart called a hypostome on the underside of the head section. One could almost imagine them as an undersea vacuum cleaner.

What are Trilobite Fossils? – Index Fossils

To date, there have been over 20,000 species named and described from the Cambrian Period some 521 to 252 million years ago when the Permian mass extinction erased almost 90% of life on earth. They ranged in size and shape from just under a quarter-inch to just over two feet long. They were quite a resilient and diverse group of creatures.

Trilobites are a well-known index fossil that can generally date the age of the rocks. Certain trilobites can be found in rocks of a certain geological age and no other, thus they are an index of the age of rocks.

Becoming a State Fossil

School children played a major role in having this magnificent trilobite designated as the State Fossil of Ohio. After students learned of a large Isotelus being found at Huffman Dam near Dayton in 1919, third and fourth-grade students and teachers lobbied for the designation. But it wasn’t until June 20, 1985, that Ohio House Bill 145 finally designated the Isotelus as Ohio’s State Invertebrate Fossil.

Other states have designated various species of trilobites as their state fossil — Pennsylvania has chosen Phacops rana and Wisconsin the Calymene celebra.

Finding Trilobite Fossils

Isotelus trilobites and Isotelus pieces can be found in several locations in Ohio. One of the most popular areas is along Caesar Creek State Park southeast of Dayton. There are restrictions and a fossil collecting permit must be obtained from the park office before heading to the large spillway where many fossils can be found.

This story about what are trilobite fossils previously appeared in Rock & Gem magazine. Click here to subscribe! Story and photos by Joseph “PaleoJoe” Kchodl.

The post What are Trilobite Fossils? first appeared on Rock & Gem Magazine.

Crinoids are often called “Sea Lilies” or “Lilies of the Seas” because of their appearance; however, they are animals. They are relatives of the extinct cystoid. Crinoids are members of a group of animals called echinoderms which include starfish, sea urchins, and brittle stars. Their name comes from the ancient Greek, Krinon which means a lily. The appearance of the stalked animals does resemble a flower.

Crinoid Body Parts

Crinoids have a five-sided pentaradial symmetry. In some species, they have arms in multiples of five and still retain symmetry. They have exoskeleton ossicles (bony plates) comprised mainly of calcium carbonate. It is because of this calcium carbonate that they became fossilized in the ancient sea. In certain deposits, they can be some of the most abundant fossils, especially the disks. Crinoids are made up of distinct body parts that include the holdfast, stalk, calyx, and arms.

The Holdfast

The holdfast is a complex system of body segments that allows crinoids to attach themselves to the ocean floor, rocks, and other hard substrates. In some cases, they attach to other animals such as bryozoans, corals, and even other crinoids. Some crinoids can release their grip and float in the water column until they find a more advantageous feeding area. This is essential for survival.

The Stalk

The stalk, sometimes erroneously called a stem, is made of many, single-round calcium carbonate disk-shaped segments or plates. Stacked atop one another, they form a long column. These disks are porous and held together by ligament-like structures. These structures quickly decayed when ancient creatures died. The stalk is hollow with a central canal passing from the calyx to the holdfast. The column can be round, square, five-sided, oval, or star-shaped. The internal cavity of the disks is also marked by a wide variety of sizes and shapes of holes.

The Calyx

The calyx or aboral cup is the main body of the crinoid. It contains most of the vital, simple organs of the creature. This is where the mouth and anus are located. The calyx is made up of irregular calcareous polygonal ossicles (bony plates) that lock together to form a general round, pentangular or oval shape.

Attached to the calyx are the brachiols or arms with feeding structures called pinnules. Located on the pinnules are small mucous-covered tube feet. The tiny pinnules on the arms sieve the water capturing microscopic particles. The tube feet capture the particles. Then they pass the particles to the center of the pinnules that have a ciliated grove called the ambulacral groove. The cilia, small hair-like structures, in turn, pass it down the groove to the mouth located near the center of the calyx. All the grooves converge on the mouth where the food enters the digestive system. The anus discharges waste matter sometimes through an anal tube that extends beyond the arms discharging material into the water.

These are the basic body parts of a crinoid. Paleontologists have named and described hundreds of different species of ancient crinoids.

Crinoid Preservation

In our prehistoric past, crinoids lived and thrived in shallow saltwater environments close to shore where food sources were abundant. Being close to the equator, these areas were prone to terrible storms and hurricanes. Much like today, these storms would ravage the shallow seas and lagoons disturbing the fragile ecosystem and destroying many creatures in the sea.

Crinoids would be ripped from their holdfasts and be torn apart strewing the ocean floor with their remains. Torrents of rain and floods, plus the retreating storm surge, would pick up dirt, mud, sand, and other sediments and wash them into the sea. Vast areas of mud and silt would cover the seafloor smothering life and burying the remains of these creatures. Rarely were crinoids preserved in their entirety.

Occasionally the storms were not as severe. Crinoids would be ripped from the seafloor and remain generally intact. Storm surges would still impact the land and bring a slurry of fine mud into the sea. They would be covered by soft mud retaining their structure and becoming excellently preserved. These are some of the rarest fossils and are the reason we know so much about crinoids.

Bringing Fossilized Crinoids Back to Their Glory

Even when well-preserved specimens are found, they still must be professionally prepared using air abrasive technology.

The process of air abrasion is painstaking to expose such delicate structures. The air abrasive unit simply consists of a pressurized air source, a prep box, a dust evacuation system, a magnification source, abrasive powders and an air abrasive tool -a mini-sandblaster.

Air is pushed through a hose at pressure picking up the abrasive material from a reservoir. It is then passed through the nozzle of the tool and the excess matrix is blasted away. Care must be taken around the fossil so as to not destroy or abrade it away. It takes much practice, and more than a few mistakes to master the process, but the results can be outstanding.

This story about crinoid fossils appeared in Rock & Gem magazine. Click here to subscribe. Story by Joseph “PaleoJoe” Kchodl.

The post What Are Crinoid Fossils? first appeared on Rock & Gem Magazine.

Shark teeth are fun fossils because (like dinosaurs) sharks are fearsomely fascinating and (unlike dinosaurs) their fossils are common. A shark may have as many as 50 teeth in a row, and behind them are six to 20 more rows, bent back and ready to spring forward as front teeth are shed. A single shark may shed 35,000 teeth over its lifespan! These are made of durable enamel, which aids in fossilization.

These two factors account for the abundance of fossil shark teeth. Fossil shark teeth come in varied colors, sizes, and shapes. Teeth of living sharks are white but, as they fossilize, they take on colors of minerals in sediments in which they’re buried and become tinted yellow-orange, tan, brown, gray or black. They vary in size depending on species. The largest, belonging to Carcharocles megalodon, can reach 7 inches. Most are under an inch.

Variation of Teeth Speaks to Species

Teeth also vary in shape. Different species have different types of teeth for different functions: flattened enamel for crushing crustaceans; pointed teeth for spearing fish; serrated teeth for tearing chunks from marine mammals. Just as our incisors and molars are different, the same shark may have very different teeth. A shark may have smooth bottom teeth for stabbing and grabbing, and serrated upper teeth for slicing and dicing. This variation in shape and function makes it difficult to identify the species of fossil shark teeth.

Sharks have an ancient lineage. The first forms date back 400 million years! Because they’ve been around so long, they’re found in sedimentary rocks around the world. Moroccan phosphate mines are especially known for them. They’re common in many places throughout the United States. I’ve collected them in Illinois limestone quarries, New Jersey stream beds, Nebraska and California hillsides, the Chesapeake Bay cliffs in Maryland, and the Gulf beaches of Florida.

The post Exploring Fossilized Shark Teeth first appeared on Rock & Gem Magazine.