Season 1 Transcript

“Amber 101” Transcript and References

The following was the script for the “Amber 101” episode for Fossil Bonanza.

Hello, my name is Andy Connolly and welcome back to another episode of Fossil Bonanza.  This is a podcast where I look at fantastic fossil sites found across the world, called Fossil-Lagerstätten, and gush why these sites are so fantastic, what they can tell us about the ancient world, and how their fossils became preserved.  This is a special episode for us as this is the first episode focused on amber!  Amber!  Yes, the almost fantastical substance who has played strong roles in both our cultural and scientific history.  Not only has it been a part of our history for thousands of years, it continues to astound us to this day for the fossils they contain.  

Fossils in amber, called inclusions, are among the best preserved fossils in the world.  Amber’s unique properties are so amazing in halting decay that it seems the trapped insects are in stasis, ready to be woken again.  The entombification of these creatures is so precise that you can find mummified insect organs, and even pollen and bacteria.  Other, more “traditional” ways of fossilization can’t even approach the level of life-like quality that amber inclusions have obtained.  Even in older times, many people were appreciative of these inclusions and a stanza I particularly like by 18th century, English poet, Alexander Pope goes

“Pretty!  In amber to observe the forms
Of hairs, or straws, or dirt, or grubs, or worms!
The things, we know, are neither rich nor rare,
But wonder how the devil they got there.”

Wonder indeed!  But we’ll learn in this episode how the devil the insects got into the amber and why they are in amazing condition.  And for our first amber episode we’ll dive into the Dominican Amber and appreciate the animals locked in its golden tombs.  We’ll see crawling spiders, terrifying parasites, and ants, ants, ants!  Ladies and gentlemen…(in the voice of John Hammond)…welcome to Fossil Bonanza! 

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7 Survival Uses Of Pine Resin You Need To Know | Survival Life
Tree resin

All amber is formed from resin, a viscous substance used by trees to patch open wounds.  Whenever a tree may experience damage from high winds or an insect invasion, it exudes the resin to patch these wounds and ensure that no further damage or invaders take place.  The resin works very well as an insecticide as not only can the chemicals be deadly but they suffocate any would be intruders from getting into the tree.  The resin then hardens and acts as scab for the wounded tree. (Grimaldi 1996, Nudds and Selden 2008)

Immediately, we begin to understand why amber is an excellent way to preserve fossils.  Not only is there a high opportunity for insects (invasive or not) to be entombed, but the resin’s solidifying properties means it can survive transport and burial.

It should be pointed out, before we go any further, that resin and sap are technically different from each other even though they both come from trees.  Sap is a watery substance that is full of sugars.  Trees use sap to deliver nutrients and sugars, produced in the leaves, throughout its body.  Maple syrup is derived from the sap of maple trees.  Resin on the other hand is made from a tree’s bark and is much thicker.  In fact, if you ever go hiking through a conifer forest, it’s highly likely you have stumbled upon resin and even felt its highly sticky, pine-like aroma on the tree’s bark.  The resin is made of terpene chemicals which give it its unique properties.

It actually takes awhile for the viscous resin to transform into an amber gem.  The transformation immediately begins once the resin has left the tree and is exposed to the air.  Many of the resin’s chemicals will slowly evaporate over time while the rest will begin to link together in a process known as polymerization.  This polymerization is what hardens the resin into amber. (Grimaldi 1996, Nudds and Selden 2008)

Before the resin can fully become amber, it reaches a stage called copal which is sort of like a proto-amber.  Copal is very similar to amber in that it’s hard and can contain inclusions but there are a few critical differences.  For one thing, it’s still undergoing polymerization and as such can be melted at lower temperatures than amber.  It also isn’t as hard as amber and it can be dissolved in many kinds of acids.  Many people have been fooled into thinking they have an amber which in fact it’s just a disguised copal.  Copal isn’t as useful for paleontologists because they are relatively young, usually less than 50,000 years old or so.  Real amber takes much longer to form and although there isn’t a hard date of when the transformation is complete.  When transformed, the amber is harder and can withstand higher temperatures and is more resistant to acids.  (Grimaldi 1996, Nudds and Selden 2008)

However, if the resin is exposed to air for too long during polymerization it can degrade and crack.  The resin needs to be safely transported and buried somewhere to continue its transformation.  That is why a lot of amber sites have been found in delta and lagoon deposits.  As the resin drips off the tree or falls down with a broken branch, it can be carried by a fast moving current to a river where it will eventually be buried by the sand and mud.  The burying mud is air-sealed and allows the water-proof resin to continue its amberfication.  (Grimaldi 1996)

There’s also another problem with amber that we need to take into account.  The trees that produce it.  You see, not every tree can produce resin and even the ones that do may not produce a lot of it.  The trees that DO produce a lot of resin are usually found in tropical areas possibly due to the high amount of invasive insects and fungi and the prominence of tropical storms that can break branches. (Martínez-Delclòs et al. 2004)

As such, we are seeing very specific circumstances for our Amber-Lagerstätten to happen.  There needs to be an abundance of trees that can produce a high amount of resin who live near a delta or a river which can quickly transport and bury the resin so it can become amber. These are very rare circumstances which seems fitting given these are among the best fossils in the entire world.  We’ll briefly mention a few global amber sites that satisfy these conditions but I want to talk about one more important piece to our Lagerstätte puzzle and that’s our inclusions, the poor critters who got stuck in the resin.

Beetle in Baltic Amber

So one of the running themes on this show is fossilization bias, that not every type of animal or plant in an ecosystem will get preserved.  Fossilization usually favors animals with hard parts located near areas that can bury them.  Even our previous Lagerstätten demonstrated some form of bias despite their amazing fossils.  The underwater mudslide in Beecher’s Trilobite Bed only buried the animals living on the sea floor while the Posidonia Shale only fossilized creatures who could swim or float in the open waters.  The same thing is true for our amber fossils.

Obviously, size is going to be the first factor here that eliminates who can become an amber inclusion.  If you’re big enough, you can easily escape the resin if you find yourself semi-trapped by it.  An absolutely huge proportion of animal inclusions are less than an inch long so it’s no wonder a lot of them are arthropods like insects, spiders, and millipedes.  It’s very rare to find vertebrate inclusions and when you do it’s just a portion of them like a body part of a feather or scales.  

Also, as mentioned before, the trees that are likely to produce amber are found in tropical rainforests.  So you’re eliminating animals and plants that can be found in other habitats like grasslands even if the two habitats are nearby.  Even then, the many micro-habitats that reside in tropical rainforests are outstanding.  Animals may specialize to live in just the trees, solely on the ground, IN the ground itself, and anywhere in between.  I encourage you all next time you’re in a park or in your own backyard to observe a tree for a few minutes and then observe the ground nearby and see how animals and plants differ even when they’re fifteen feet apart.

The Dominican Republic amber is a fantastic example of this.  Even though there are over 800 species of butterflies and is the third most species-rich insect on modern Hispaniola, only 7 species are known from amber.  This is probably because they just don’t regularly interact with the resin trees.  Meanwhile, ants make up 26% of all the amber inclusions due to their frequent crawling up and down the tree.  (Penney 2010)

Then you have to take into account geologic time.  Although resin has been found dated to about 300 million years old, it didn’t become abundant until about 120 mya during the age of dinosaurs.  Why the sudden rise?  Although there is some discussion on the matter, it may have been tied to the evolution of wood-boring insects.  More resin means less intruders!  (Martínez-Delclòs et al. 2004)

All of this means we have a very, very focused lens on our inclusions.  Yes, the animals and plants may not wholly represent the world they lived in but danget are they not the most wonderful fossils out there.  Let’s dive into what it takes for an insect to be immortalized in amber.

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In general, one of the best ways for an organism to become a fossil is to remove it from the environment as fast as you can.  You want to minimize the time between an animal’s death to its burial so you can preserve as much of it as you can.  For many burying environments, this can take several days to hundreds of years before the animal remains are submerged.  Resin can do this in minutes.  As an insect, say an ant, is crawling on a tree, it walks across the resin and almost immediately becomes stuck in the viscous substance.  While struggling in its gooey deathbed, another wave of resin buries it completely and submerges it.  The ant dies through either suffocation or dehydration and exhaustion if it’s only partially submerged.  Immediately, the resin begins it amberfication and the ant begins its fossilization.

Resin is incredibly good for decay prevention.  I already mentioned before that resin is waterproof but some resin have anti-fungal or anti-bacterial properties that prevent tiny microbes from infiltrating and growing in its golden walls.  Not all resin have this though as I came across an example of fungi growing off of an insect inside of the amber!  It’s likely that the fungi was already leeching on the insect by the time the resin submerged it.  The fungi then immediately grew off of its now dead host before it succumbed to its oxygen-deprived, resinic environment.  Very cool!  (Martínez-Delclòs et al. 2004)

However, in some cases, resin may be too good at its entombification.  If an insect is quickly submerged, it can go through a process known as autolysis.  The insect’s own cells and bacteria begin to break down the internal cells and tissues.  When the resin seeps into the insect, it reacts with the internal soupy fluids and creates a bubbly sphere around the insect.  The resulting process leaves a 3-dimensional, hollow cast of its inclusion.  (Martínez-Delclòs et al. 2004)

Fortunately, there is a way nature can prevent autolysis from happening.  If the insect is only partially submerged and dies before another wave of resin buries it, it can dehydrate to the surrounding environment.  The lack of water halts any kind of bacteria activity that may destroy the internal organs.  Once the resin submerges it, the insect will be mummified with its internal organs still in place.  (Martínez-Delclòs et al. 2004)

Archaeid spider in Baltic amber. Notes: The presence of this family... |  Download Scientific Diagram
Amber spider. Image from

This is when amber’s astonishing potential of fossilization occurs.  If the tissue compounds are relatively stable we can detect the likes of organs like a spider’s book lungs, liver, or spinning glands.  We can even identify cell organelles like mitochondria, ribosomes, and cell nuclei which is absolutely insaaaaaaaane (Nudds and Selden 2008).

Which leads me to the T-Rex in the room, the million dollar question, can amber preserve DNA?!  To give an unsatisfying answer…it likely does not.  DNA is highly unstable and even in the best of best conditions it’s rare to find DNA that’s over 100,000 years old.  In the 90’s, during the Jurassic Park hey-day, there were a number of publications saying scientists were able to extract DNA from insects millions of years old but these results have since not been replicated and were likely due to lab error.  The history behind the DNA Holy Grail is quite complex but fascinating so I’ll leave it to a future amber episode to tell that story.  (Austin et al. 1997, Martínez-Delclòs et al. 2004)

In fact, DNA, and other organic compounds like proteins, in general do not have a stable shelf life, even in the comforts of an amber home.  The body constantly needs to update, fix, and mend broken and degraded molecules to keep itself functional.  Many of those compounds just break down over time while others, like the hard exoskeleton of insects, remain strong and relatively unchanged for millions of years.  So even amber, despite its near perfect conditions of delaying decomposition, can only do so much for its imprisoned inclusions. (Martínez-Delclòs et al. 2004)

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As we have seen, amber deposits just go all in on having high quality fossils.  They’re the definition of a Konservat-Lagerstätten or a fossil site with excellently preserved fossils.  The trade off being that A. only certain kinds of organisms can become fossils and B. there are relatively few amber sites found throughout the world.  Even profitable amber sites struggle to produce inclusions as a majority of the amber stones have nothing in them. (Martínez-Delclòs et al. 2004)

One source I’ve read dating from the 90s said there are hundreds of known global sites that produce amber but only in trace quantities.  About 20 of them have an abundance of mined amber.  Even then, these 20 or so, from what I can tell, are overshadowed by four sites that dominate the amber literature.  They are known as the Lebanon, Burmese, Baltic, and Dominican Amber sites.  These big four sites again and again are praised for their scientific significance and their amber abundance.  The Dominican and Burmese sites in particular have seen a rush of new species identified every year and keeping up with them is almost impossible.  The fossils all four of these sites contain are magnificent and give a critical look into our world’s evolutionary history.  Their importance cannot be understated. (Grimaldi 1996)

In another time, we will look at the Lebanon, Burmese, and Baltic sites but for now we’re going to end the episode here and resume next time for the Dominican Amber! Hope to see you then.

<end of episode>


-Austin, Jeremy J., et al. “Problems of reproducibility–does geologically ancient DNA survive in amber–preserved insects?.” Proceedings of the Royal Society of London. Series B: Biological Sciences 264.1381 (1997): 467-474.
-Grimaldi, David A. “Amber: window to the past.” (1996).
-Martı́nez-Delclòs, Xavier, Derek EG Briggs, and Enrique Peñalver. “Taphonomy of insects in carbonates and amber.” Palaeogeography, Palaeoclimatology, Palaeoecology 203.1-2 (2004): 19-64.
-Penney, David, ed. Biodiversity of fossils in amber from the major world deposits. Siri Scientific Press, 2010.
-Selden, Paul, and John Nudds. Fossil ecosystems of North America: a guide to the sites and their extraordinary biotas. CRC Press, 2008.

Season 1 Transcript

“Beecher’s Trilobite Bed” Transcript and References

(The following is the script used for “Beecher’s Trilobite Bed” and closely matches the final episode product)

<sounds of nature which slowly fades>

For eight years, William Valiant, a one-armed carpenter and fossil enthusiast had been looking for the find of a lifetime.  He and his half-brother, Sidney Mitchell, would spend their days off in the countryside, near their home of Rome, New York, looking for a particular fossil.  It started from a chance find, when William found an odd fossil at Six Mile Creek in 1884.  It was a golden leg of a trilobite, an ancient sea creature that looked like a squashed centipede.  Up until then, no one knew what a trilobite’s leg looked like.  This leg was amazingly preserved, unlike what William had ever seen before, and he was enamored by its design.  He knew that if he could find the rest of the fossil, he might find something even more remarkable, their antennae.  Paleontologists, up until then, had thought trilobites had antennae but the lack of fossilized evidence meant that this was mere postulating.  William knew that if he found the trilobite, antennae, legs and all, he would be making history.

William Valiant standing next to a Mastodon in Rutgers Geology Museum

So for eight years he and his brother would search for these fossils.  Again and again, nothing.  Finally, he found the fossils; they were buried deep along a hillside and nestled within a layer of shale just 4 cm thick that was practically indistinguishable from the meters of rock that surrounded it.  Yet within these 4 cm of rock were some of the most amazing fossils found by that date.  These trilobites were golden as if touched by Midas himself.  They were preserved in stunning detail with their many legs in neat rows and their original 3-dimensional body only slightly squashed by the layers of rock above it.  And there, in miraculous detail, were the thin antennae arching like a whip.  He had finally found his white whale, or in this case, his golden trilobite.  Few other trilobite fossils can match the level of stunning quality and detail of these golden trilobites.  But how did this happen?  Why are the trilobites preserved so perfectly?

In this episode of Fossil Bonanza, we will answer these pertinent questions and dive into the wonderful Lagerstatte of Beecher’s Trilobite Bed.  Let’s take a look!

<Music intro>
History of Beecher’s Trilobite Bed

Hello and welcome to Fossil Bonanza!  My name is Andy Connolly and this is a podcast where we look at unusual fossil sites around the world called Fossil-Lagerstätten.  In our first episode, we talked about the history of paleontology, how it can be very hard for a critter to become a fossil, and the different types of Fossil-Lagerstätten.  This is our second episode and the first to focus on a particular fossil site.  For our first episode, I wanted to focus on something that was small but impressive and I thought Beecher’s Trilobite Bed fit the bill.

If you were to step back to upstate New York about 445 mya, you would not be strolling through a cool, temperate forest but swimming in a sub tropical sea.  It is the late Ordovician Period and the world is very different than it is today.  Dinosaurs, reptiles, mammals, or amphibians haven’t evolved yet.  In fact, life on land is restricted to just a few small colonizers of bugs and moss.  The sea in New York hosts a variety of weird and wonderful creatures who thrive in this world.  One of which are the trilobites; a very successful ancient group of bug-like animals who could be found in every sea across the world.  And on one fateful day, these trilobites and their ecological partners, would be preserved in a freak accident that would make them one of the best fossil sites in North America.

Beecher’s Trilobite Bed, found within the Frankfort Shale of the Utica Formation, is a Konservat-Lagerstätten, a Lagerstätte with very high quality fossils.  There’s not a lot of fossils here but dang are they not just outstanding!  The fossils are made of pyrite which gives them a most luxurious sheen compared to the more drab and dull-looking fossils you may see in museums.  This gives the golden fossils a very sharp image contrasting the surrounding shale which is a dark gray, almost black color.


You may be thinking that Beecher was the scientist who discovered the these pyritic fossils.  Well, although Charles Beecher was instrumental in the site’s history, he wasn’t the first to discover it.

Like a lot of famous fossil finds, Beecher’s Trilobite Bed was found by luck, persistence, and an amateur.  As introduced in this episode, the fossils were found by William Valiant of Rome, New York.  While walking along Six Mile Creek, he found a chip of shale with trilobite appendages on it and immediately recognized its importance.  As we’ll get into later, trilobite legs are rarely preserved in the rocks.  Even rarer were fossilized antennae which paleontologists hypothesized trilobites had but lacked crucial evidence to support it.  Valiant recognized the importance of his lucky find and vowed to locate the site that entombs these creatures.  It took him eight years but he and his brother found the trilobite bed in 1892.  Antennae, appendages, and all.

Finding these golden critters was like hitting the paleontological jackpot and Valiant was excited!  He wrote to several regional paleontologists and sent them fossil samples of his instrumental find.  One of them was WD Matthew who recognized their significance and proclaimed in 1893 using the samples as examples that trilobites had antennae. Valiant also wrote to the famous Professor Marsh at Yale.  Marsh referred this information to a man he thought would take a great interest in the pyritic trilobites, a younger colleague named Charles Beecher.  Beecher was Yale’s first invertebrate paleontologist and was Curator of Geology beginning in 1891 (as a side note, an invertebrate is an animal that doesn’t have a backbone like we do such as insects, corals, clams, and worms).   The excited Beecher wasted no time; he took a lease on the land in 1893 and started excavating the fossils that same year.  When Beecher found the trilobites he excitedly wrote to Marsh “I feel quite well satisfied now with the results of this trip, and think we can nearly control the antennae business. I look forward with pleasure to working up the collection.”  You see?  I wasn’t kidding about the antennae, it was like the paleontological equivalent of seeing dollar signs.  

Dr. Charles Emerson Beecher

Upon fossil extraction, Beecher prepared the 4 cm long trilobites by experimenting with different tools.  When it was quite apparent that a simple chisel and hammer weren’t going to cut it, he tried acid which ended up dissolving both the stone and the fossil.  Dental tools worked well but couldn’t uncover the delicate legs very well.  But finally, Beecher found that an eraser with a soft rubber was the best tool as he could rub away the soft shale without damaging the fossil.  It was so refined he could even clean out the spaces inbetween the trilobite legs.  He was so good at it that William Dall of the Smithsonian wrote “aided by his remarkable manual dexterity, mechanical skill, and untiring patience, [he] worked out the structure of antennae, legs, and other ventral appendages with a minuteness which had previously been impossible.”

Beecher’s meticulous preparation, research, and publications on the trilobites is the reason why the quarry is named after him.  He gave detailed analysis of the trilobites’ anatomy and described larval stages of key trilobite species using the specimens.  His artistic reconstructions of a trilobite were so incredible that his artwork was reproduced many, many times in textbooks and brought fame to his quarry.  In fact, before he published photographs as proof, some scientists regarded his drawings as so outlandish that they were unreliable.  They were that game breaking.  Unfortunately, before Beecher could publish more papers on the triobite’s anatomy and family relationships, he passed away at just 47 in 1904.  Thankfully, his student Percy Raymond completed his work in 1920 when he became a professor at Harvard University and Beecher’s work is still available today for all to read.

Image from Beecher (1896)

Beecher believed his quarry, and another quarry that was located just upstream, was completely excavated but attempts have been made decades after his death to confirm it.  This proved difficult as many people had trouble trying to find it.  But in the 1980s the bed was rediscovered by two fossil collectors after carefully studying old photographs of Beecher’s site.  The site has since been further excavated by paleontologists from the Smithsonian, American Museum of Natural History, and the Yale Peabody Museum and continues to be a treasure trove of fossils to this day.

Trilobites and their Fossilization

So, it may not come as a great shock to you that most of the discovered fossils of Beecher’s Trilobite Bed are trilobites with just a few creatures from other animal groups.  So…what is a trilobite exactly?

The Life Of The Ordovician. Continued | Trilobite fossil, Trilobite, Fossils
Trilobites in all their wonderful forms

The trilobite is probably the most iconic fossil just behind the ammonites (the spiral shaped fossil).  It’s more than likely you have seen one before and there’s a good chance that if you have a fossil collection you have a trilobite.  Trilobites kind of look like pill bugs but a bit wider, a more prominent head, and generally larger.  The name “trilobite” means “three lobe” in reference to their general body plan.  They have an axial lobe, which runs centrally from their head to tail, and is flanked by two pleural lobes that make up their sides.  Despite the great difference in size and shape among trilobites, they all have these three lobes.

Trilobites are in the arthropod group of animals which contains critters like insects, spiders, crabs, and basically anything that has a hard exoskeleton and jointed legs.  A lot of people like to compare trilobites to the modern horseshoe crab which I’m a bit uneasy at.  True, horseshoe crabs are marine and they’re arthropods but they’re not descendents of them; they are as closely related to them as they are to spiders.

In fact, trilobites are basically their own group of arthropods!  Broadly speaking, there are five groups of arthropods; the crustaceans (which include lobsters and crabs), the myriapods (centipedes and millipedes), the chelicerates (spiders, scorpions, and horseshoe crabs), the insects, and finally the trilobites.  I have read estimates that over 20,000 species have been named so far which is incredible.  By comparison there are just over 5,000 species of modern mammals.  Indeed, trilobites were a very successful group of animals.

You may have noticed that among the five arthropod groups only trilobites aren’t alive today.  Trilobites, unfortunately, are currently extinct.  They evolved very early about 521 million years ago and rapidly flourished.  However, as time went on they began to die off and their numbers were greatly reduced following many extinction events.  The greatest extinction of all time, the Permian Extinction, was the one that wiped them out 252 million years ago.  So they lived for about 270 million years which is a fantastic achievement.  (As a frame of reference, dinosaurs, who appeared after trilobites went extinct, lived for about 165 million years.)  

Okay, so since trilobites are a very common fossil, why do paleontologists make a big deal about Beecher’s Trilobite Bed?  This…is where the story gets interesting!

One of the reasons why arthropods are the most dominant lifeform on the planet is their exoskeleton.  Their exoskeleton is made of mostly chitin which is a rather tough and resilient material.  In trilobites, crabs, and lobsters, the shells are further reinforced by the hard mineral calcium carbonate.  The exoskeleton is the main source of strength and speed for arthropods.  With it, they’re able to exploit environments and fill in roles that may otherwise be left open.

The biggest drawback of the exoskeleton is its rigidity.  Unlike our bones or a shell of a tortoise, an arthropod’s exoskeleton does not grow with the animal as it ages from larva to adult.  Every time it gets too big for its exoskeleton, it sheds it, crawls out of it like some sort of freaky body bag, and allows its new exoskeleton to expand and harden.  This process is called “ecdysis” and the discarded old exoskeleton is called an “exuviae.”  A well known example of this are cicadas who, after they crawl out of the ground like cute zombies, will shed their old skin, unfurl their wings, and begin their wonderful life above ground.  You’ll see their exuviae everywhere, especially when a group of them come out of the ground at the end of their 17 year cycle.


Trilobites go through ecdysis as well!  Paleontologists hypothesize that trilobites start its ecdysis by latching its tail to the bottom of the ocean and wiggling back and forth.  The sides of their head, called a cephalon, would then split wide open and allow the trilobite to escape.  Their exuviae, now completely discarded, could be easily buried by sand and mud and eventually fossilize.  Given that trilobites can sometimes be a foot long, they likely shed their skin at least several times a year.  This means (ready for the mind blowing part?) that a single trilobite can leave multiple fossils of itself!  In fact, most trilobite fossils found in the world are just their exuviae!  Whole species and genera are described from their discarded exoskeleton alone.  It’s honestly quite rare to find the actual trilobite body.

Now remember what I said a moment ago that trilobites use calcium carbonate to reinforce their shells?  That shell’s durability gives it strength to fossilize properly.  HOWEVER, a trilobite’s legs and antennae do NOT have that mineral!  That means they are much softer AND are more likely to rot away before being preserved!  It’s very much like a bird’s feather or a mammal’s hair, if you find a trilobite’s antennae, you found something good.

Now it falls into place.  Why our amateur fossil collector, Valiant, was so keen in finding those trilobite fossils.  When he stumbled upon that shale chip of a fossilized trilobite leg, he knew how valuable it was and why he had to find the rest of it.  Why he had to spend eight years of his life looking for that bed.  To find trilobites that were not just their exuviae but of their legs, and antennae, and anything else that could be preserved in those black layers of shale.

That is the significance of Beecher’s Trilobite Bed.  Not just because they’re golden or preserved in pyrite but because they store the memory of the trilobite itself, body and all.  We know exactly what trilobites look like thanks to those 4 cm layers of rock.  This is why Beecher’s Trilobite Bed is a Konservat-Lagerstätten.

How the Trilobites got Preserved

So how did these trilobites gets preserved?  And why did pyritized trilobites only happen in this very specific, 4cm layer of rock when the surrounding shale layers only have bits and pieces of fossils?

Organisms can become fossils in several different ways but one of the most prominent methods is called “permineralization.”  This occurs when pores inside an animal or plant’s cells are filled with mineralized water; this water can come oceans, lakes, or even rain.  As the water evaporates or moves out of the pores, it leaves behind minerals that were dissolved in the water. The minerals will crystalize and reconstruct the tissue shape of the organism and can even preserve the original organic material.  Petrified wood and bones commonly go through permineralization to become a fossil.  As we progress on Fossil Bonanza, we will return to permineralization again and again and how it affected our Lagerstätten.  

So, permineralization can use different minerals to preserve the organism.  Silica is a really common mineral in permineralization and can be frequently seen petrified wood.  If the animal is preserved fast enough, some minerals work very well to protect soft tissues like carbonate or phosphate.  For Beecher’s Trilobite Bed, the presence of sulfur changes the trilobite into pyrite which is called pyritization.


Pyrite, also known as Fool’s Gold, has a simple chemical formula of iron disulfide and is a very common Earth mineral especially in marine sediment (if you ever go to gem and mineral shows you’ll see these minerals on sale relatively cheap).  I really like pyrite because they’ll grow into these beautiful golden cubes.  Sometimes they’ll have cubes upon cubes and create a stunning geometric shape to them!  They’re very wonderful.  (and as a side note, I love teaching rocks and minerals to my students because they’ll get to see pyrite and debate if they pyrite cube is gold or not which is quite amusing.)

A source for pyrite’s commonality are humble organisms with an intense name; anaerobic sulfate-reducing bacteria.  There’s a lot to unpack here!  Anaerobic sulfate-reducing bacteria.  Let’s break that down.  First, bacteria are single-celled microorganisms that are smaller than our animal cells and can live in all sorts of crazy environments like the hot springs of Yellowstone.  In fact, many bacteria don’t need oxygen to survive.  These bacteria are called “anaerobic” while those who do need oxygen are called “aerobic.”  Aerobic organisms use oxygen to breathe while anaerobic organisms use other molecules instead.  What’s wild is that many anaerobic bacteria find oxygen toxic and can even die from oxygen poisoning!  Okay, so if they don’t need oxygen, what do they use?

Anaerobic organisms can use such molecules as sulfate, nitrate, or iron to produce energy and quote-unquote “breathe.”  For sulfate-reducing bacteria, they use sulfate (which is made of one sulfur and four oxygen atoms) and reduce it to hydrogen sulfide as an end product.  You may have experienced sulfate-reducing bacteria in real life as they’re the source of rotten egg smell or the sulfurous smells from salt marshes.  The hydrogen sulfide is important to us as when it reacts to the sediment’s iron minerals they form pyrite!  (this, btw, is a simplified look at the process and is about as in-depth as we’ll get for our fossil podcast).  

Despite the commonality of these bacteria along with sulfur and iron, the process to turn animals into pyrite is actually pretty rare.  Even then, when pyritization does happen it’s only the animal’s hard parts that are preserved and nothing else.  Only in very specific circumstances can soft-part preservation happen.  So what was it that led to the trilobite preservation?

Before the trilobites came, the sulfate-reducing bacteria were living in an ocean floor with a severe lack of organic food.  We know this because many of the surrounding rock layers had a plethora of fossilized burying organism but that 4 cm layer of rock had nothing, it was an underwater desert.  This was a time when the bacteria were starving. But what the layer DID have was iron and lots of it.  All of this iron and all of these starving bacteria were primed to make our Lagerstatte happen. It just needed one more key ingredient.

That key ingredient came in a flash.  Based on the fossils and the sediment patterns, we can infer that the trilobites were dumped into their current position from somewhere upshore by a turbidity current (basically an underwater avalanche).  We know this for several reasons and the first of which are the trilobites which are arranged roughly parallel to each other. This indicates that a strong unidirectional-moving current carried the trilobites all at once before burial.  This also means that the trilobites were already dead by the time they got buried because otherwise they would have attempted to escape and disrupt their alignment.  Furthermore, the sediment patterns in Beecher’s Trilobite Bed match modern turbidity currents which is quite a smoking gun.  You can see evidence of this in the rock layers as it starts with a heavily eroded base followed by a gradual decrease of sediment size upward due to a weakening current.

As such, we now have all our pieces to reconstruct the scene of the crime.  First, a turbidity current was triggered by some unknown force and swept across the ocean floor. It picked up the trilobites and buried them further downwards.  The shock of the deeper water’s cold temperatures likely killed the trilobites quickly which kept them in place.  Now buried, the trilobites were protected from any scavengers who may tear apart the soft limbs.

The influx of this fresh meat triggered the sulfate-reducing bacteria who immediately went to town on the trilobites’ shells, antennae, and legs.  The bacteria produced hydrogen sulfide which was trapped by the overlying sediment.  The water, rich with iron, seeped in through the trilobites’ pores and reacted with the hydrogen sulfide.  Pyrite precipitated out of the water and replaced the trilobite’s original body, reconstructing it with the golden mineral.  Since the sediment was still loose and non-compacted, the trilobite bodies’ original 3-dimensional form was replaced by the pyrite recreating even their soft tissues and structures.  In a matter of months the reactions ceased and the trilobites laid undisturbed for over 400 million years, waiting patiently to be discovered by William Valiant.

Two Triarthrus

The Trilobites in Beecher’s Bed

Now that we understand how our trilobites got preserved let’s focus on the animals themselves.  What have we found in these rock layers and what can we infer from the fossils?

Although trilobites dominate the fossil assemblage, both in abundance and in notoriety, we see other animals that are typical of the Ordovician period.  These mainly include the clam-like brachiopods and the colony-oriented graptolites.  As these animals make up a small percentage of the fossils, and aren’t particularly special, we will put them aside for now.  Perhaps in a future episode I will talk more about them and their global commonality but for now they’ll just be a footnote for us.

Even among our trilobites there is one species that dominates the rest called Triarthrus.  It’s so abundant it makes up about 85% of the fauna recovered from the bed!  Growing up to 4 cm long, Triarthrus is probably one of the most recognizable species of trilobites in the world thanks to Beecher’s Trilobite Bed.  The original drawings of Triarthrus by Beecher were quickly favored in paleontology textbooks and research papers and they were recreated again and again.  The clean visuals, the many spindly legs, and the long and flowing antennae were easy on the eyes and mind.  If you ever see a recreation of a trilobite, it’s a good chance it’s a Triarthrus.  

Museum Triarthrus Trilobite

The plethora of Triarthrus that make up our death assemblage means we can gleam some juicy information that may otherwise be lost with just the one individual.  For instance, the amazingly preserved legs and gills give us an idea how Triarthrus moved and fed along the ocean floor.  We also have an idea of their overall shape given their 3-dimensional burial with minimal squashing.  However, one of the more incredible things about these fossils are their preserved guts!  Since the pyrite recreated the original structure of the trilobites’ internal organs, we can peak inside them using X-rays and see what they look like.  It’s preserved so well that we can determine a trilobite’s gut is very similar to a crab or spider’s gut.  Isn’t that wild???

These detailed anatomical recreations of Triarthrus are quite useful in reconstructing the overall arthropodal family tree.  Thanks to these remarkable trilobites along with other fossilized evidence, paleontologists infer that trilobites’ closest living relatives are the crustaceans and the chelicerates (who again include the horseshoe crab, spiders, and scorpions).

The abundance of Triarthrus fossils also means we can think about their life cycle.  Adult Triarthrus are very common in Beecher’s Trilobite Bed but what’s notably absent are the juveniles.  Although you can find fossils of juvenile exuviae, just like any other trilobite fossil, their actual bodies are completely absent.  This is also interesting given that only a small percentage of trilobites reach adulthood.  So why is Beecher’s Trilobite Bed so adult-heavy?

Well, based on Beecher’s Trilobite Bed and other Triarthrus fossils found elsewhere, we have a pretty good idea what their lifecycle was like.  After hatching from eggs less than a millimeter long, the baby trilobites would float in the water for a month or so as a suspension feeder.  As they grow older and shed their exoskeletons, they gradually transitioned to a seabed-only lifestyle where they scavenged on carcusses and hunt any small critters they dig up.  Based on their exuviae, it’s likely they lived to about four years of age and probably had an annual breeding season like modern crustaceans.

Given this context, it makes sense why the adults were preserved and not the juveniles in Beecher’s Trilobite Bed.  When the turbidity current came it only affected the adults and not the kids as they were having a good time up in the water column, relaxing, and taking it easy.  Meanwhile, the adults were swept away by the underwater avalanche and died for simply being too old.  This also explains why there’s a notable absence of other sea dwellers as they were above the disaster zone.  Very cool.

Cryptolithus tessellatus
Cryptolithus although not from BTB

There are a few other trilobite species found here but they are quite rare.  One of the more interesting species is Cryptolithus which, unlike Triarthrus lacked eyes!  They had these sensory pits instead which helped them observe the low-light world of the ocean floor.  We also find mainly baby specimens of Stenoblepharum and it’s likely they spent their time on the sea floor before moving up to the water column (basically the complete opposite scenario of Triarthrus).  But like I said, both of these species are quite rare and really, a more accurate name for Beecher’s Trilobite Bed should be Beecher’s Triarthrus Bed!  Hm, probably for the best that we stick to the original; it’s a lot more brand friendly!


So as we close our first Lagerstätte-themed episode I want to reflect on the importance of Beecher’s Trilobite Bed.  I think Beecher’s Trilobite Bed is a great example of a Konservat-Lagerstätte because of those amazing trilobites.  The fact that we can preserve the legs, antennae, and even their gut, preserved in multiple specimens is amazing!  We can recreate their life cycle, their feeding habits, and their way-of-life from these precious fossils.  We can also learn more about how Triarthrus, and in general trilobites, fit in the overall tree of life, how they relate to modern animals and, on the flip side, how we can use modern animals to infer about their lifestyle.  And to this day, we see Beecher’s drawings of trilobites as they fill our textbooks and minds of these once bygone creatures.  It’s all just very remarkable and poetic.

As we progress in this series, I have a feeling we will be seeing the influence of Fossil-Lagerstatten, whether subtle or not, come again and again.  The gaps in our Earth’s history are so wide and so thin that any remarkable fossil will give a peak into a world that is otherwise lost.  Their fossils fill museum displays, painted into murals, and make up so many iconic ancient animals that we see on TV and in the movies. 

When I teach my students geology, I sometimes get asked how much money the pyrite is worth.  And my response?  It’s not the financial value that makes it important, it’s what we can learn from the object.  And though the trilobites’ pyritic makeup does make them amazing to behold, what we can learn from them, I would argue, makes them many times more special.  William Valiant knew this as well and it’s what made his eight years of searching for the golden trilobites worth it.If you liked this episode and would like to hear more please subscribe and check out my Fossil Bonanza blog where I post articles and more podcast episodes.  If you have any thoughts or what you would like to learn more og let me know in the comments!  If you also want to read more about Beecher’s Trilobite Bed I’ll include research papers that are free for the public as well as Beecher’s original papers.  One thing that I didn’t mention were the Sulfur isotopes that were influential in the pyritization process.  I’d figured I already went technical enough as is in this episode so I kept it on the lighter side.  And check out the books Fossil Ecosystems of North America  by Nudds and Selden and Exceptional Fossil Preservation by Bottjer, Etter, Hagadorgn, and Tang.  These books talk about Beecher’s Trilobite Bed along with other unusual fossil sites.  Also check out Richard Conniff’s House of Lost Worlds which provided some good insight into the trilobite bed.  Thanks again for watching and I hope to see you again next time!

-Beecher, Charles Emerson. “ART. XXIX.–The Morphology of Triarthrus.” American Journal of Science (1880-1910) 1.4 (1896): 251.
-Briggs, Derek EG, Simon H. Bottrell, and Robert Raiswell. “Pyritization of soft-bodied fossils: Beecher’s trilobite bed, Upper Ordovician, New York State.” Geology 19.12 (1991): 1221-1224.
-Cisne, John L. “Life history of an Ordovican trilobite Triarthrus Eatoni.” Ecology 54.1 (1973): 135-142.
-Cisne, John L. “Anatomy of Triarthrus and the relationships of the Trilobita.” (1975).

Fossil Spotlight

Fossil Spotlight: Mesosaur Embryo

Pictures, Diagram, and Drawings of the Mesosaur Embryo.  Image by Piñeiro et al. 2012
Picture, diagram, and drawing of the Mesosaur embryo. Image from Piñeiro et al. 2012

Who: Mesosaur embryo
Lagerstätte: Mangrullo Formation in Uruguay
What: Mesosaurs were an Early Permian group of reptiles that swam in the seas. They were the first reptiles to return to the oceans starting a marine reptile trend that would continue to this day. Many ancient marine reptiles like mosasaurs, ichthyosaurs, and plesiosaurs have evolved to give live birth, called viviparity, which was crucial in their marine domination. This mesosaur embryo is the oldest known amniotic (which includes mammals, reptiles, and birds) embryo. The advance stage of the embryo suggests that mesosaurs were also viviparous or laid eggs on land which quickly hatched. Mesosaurs may have even tended to their young in a nurturing behavior. In general, eggs and embryos are rare in the fossil record due to their low fossil potential but every now and then we get lucky with a truly remarkable find like this one.

Piñeiro, Graciela, et al. “The oldest known amniotic embryos suggest viviparity in mesosaurs.” Historical Biology 24.6 (2012): 620-630.

Fossil Spotlight

Fossil Spotlight: Pumiliornis, the Earliest Known Flower-Visiting Bird

Pumiliornis fossil; boxed area is the location of the pollen grains. Image from

Who: Pumiliornis tessellatus
Lagerstätte: Messel Pit in Germany
What: Pumiliornis is the oldest known flower-visiting bird in the fossil record at 47 million years old (Eocene Epoch). This is based on preserved pollen grains in its stomach! This strongly supports nectar-eating behavior further compounded by its beak which was long and likely flexible similar to hummingbirds. Fish and seeds have been found in birds stomach before, like the Jehol Biota in China, but pollen-finds are rarer and usually nectar-visiting behavior has to be inferred based on the fossil’s anatomy which can be difficult. Pumiliornis is not closely related to any known modern pollinators.

Close up of Pumiliornis stomach contents. Pollen grains circled. Image from

Mayr, Gerald, and Volker Wilde. “Eocene fossil is earliest evidence of flower-visiting by birds.” Biology Letters 10.5 (2014): 20140223.

O’Connor, Jingmai K., and Zhonghe Zhou. “The evolution of the modern avian digestive system: insights from paravian fossils from the Yanliao and Jehol biotas.” Palaeontology 63.1 (2020): 13-27.

Fossil Spotlight

Fossil Spotlight: Orb-Weaver Spider in Amber

Who: Pulchellaranea pedunculata
Lagerstätte: Dominican Amber
What: Pulchellaranea is an orb-weaver spider encased in amber from the Dominican Republic. Orb-weavers are the most common group of spiders who spin the wheel-shaped webs you see in your backyard, forests, and parks. Spiders are notoriously rare in the fossil record and over 90% of spider fossils are found in amber. Their rarity is due to their fragile nature and burial difficulties as their corpses tend to float on water and not sink. Spiders are more common in amber as it gently entombs them and minimizes decay. An ant, which are quite common in the Dominican Amber, joins this spider. Their proximity indicates they fell into the amber at the same time probably after a brief interaction.

-High def image from the New Yorker
-The same image can also be found in black and white along with a description of this species here
Poinar Jr, George. “Pulchellaranea pedunculata n. gen. n. sp.(Araneae: Araneidae), a new genus of spiders with a review of araneid spiders in Cenozoic Dominican amber.” Historical Biology 27.1 (2015): 103-108.

Fossil Spotlight

Fossil Spotlight: Heliobatis radians

Who: Heliobatis radians
Lagerstätte: Green River Formation
What: Heliobatis is a freshwater stingray that lived in Wyoming during the Eocene period.  At the time, Wyoming used to be much warmer and wetter than it is today (think Louisiana) and was filled with freshwater lakes.  Stingrays are cartilaginous fishes related to sharks.  As such, its rare to have complete stingrays in the fossil record as they mostly lack hard parts; usually you would fine their teeth, scales or stings if you’re lucky.  However, the Green River Formation, where Heliobatis is found, is one of two places in the entire world with complete stingray fossils (and the only site with freshwater ones).  This is because the stingray’s lakes had a salty and anoxic bottom so when they died they fell to the bottom of the lake where they’re eventually burried and preserved almost to perfection.

File:Heliobatis radians, Lincoln County, Wyoming - Natural History Museum of Utah - DSC07176.JPG

“Freshwater stingrays of the Green River Formation of Wyoming (early Eocene), with the description of a new genus and species and an analysis of its phylogenetic relationships (Chondrichthyes, Myliobatiformes),” Carvalho et al. 2004
(Link is a download pdf provided by AMNH)