“TRI-LO-BIIITE!”
Oh, no, that was a terrible opening. You’ll only know what the heck I’m talking about if you remember JJ from the television show Good Times, and it’s such a pathetic joke it’s only going to appeal to grade schoolers. So if you’re a time-traveling 8 year old from the 1970s, you’ll appreciate the reference. How many of those are reading this right now?
Maybe this will work better. Here’s a small chip of shale I keep at my desk.
My son Alaric and I collected that on a trip to Delta, Utah over 20 years ago. We had permission from the owner of a commercial dig site to rummage around in their tailings*, and we ambled about picking up chunks of rock and splitting them with a hammer. Everywhere we looked were trilobites. We brought home a good haul, chiefly Elrathia, like that one, and lots of Peronopsis. I keep it at my desk as a token of a good memory, and also because it’s about half a billion years old.
I can reach over and touch a half billion year old fossil at will, which I find to be an awesome thrill. That it’s also from a subphylum that was so successful, swarming in our oceans for about 300 million years, yet that ended so finally in the Permian extinction, is humbling. Puny ephemeral humans — we can only dream of achieving the glories of the Trilobite empire.
Summary of the evolutionary history of the major trilobite clades plotted against stratigraphic time. The y-axis scale approximates a log scale to permit the more detailed illustration of the Cambrian and Ordovician diversifications. Numbers refer to age in millions of years (Ma). Although the spread along the x axis approximates the morphological diversity within a clade at any given stratigraphic level, horizontal distances between groups should not be interpreted to suggest degrees of phenetic difference. The diagram is not meant to imply that maximal phenetic variance was present in the early part of the Cambrian, even though groups such as Agnostida and Corynexochida form the extremes along the x axis. This is an artifact of the mode of representation. Trilobite color represents the condition of dorsal exoskeletal trunk tagmosis: orange is the homonomous condition, pink is the heteronomous condition in which the batch boundary occurs within the holaspid thorax, blue is where this boundary occurs within the holaspid pygidium, and green where it occurs at the thoracic/holaspid pygidial boundary. The representation is schematic and not meant to imply that all members of these clades younger than the image shown had that condition.
If you want to learn more about trilobites, I can’t recommend Richard Fortey’s book, Trilobite: Eyewitness to Evolution
Despite being extinct for 250 million years, and despite being nothing but fossils, we still have a pretty good idea of the development of trilobites, because they were so numerous and we can find great drifts of entire populations of the animals embedded in lagerstätten. That allows us to see the range of variation and the distribution of different developmental stages, and further, because they’re arthropods, we can see well preserved cuticles of both intact animals and molted shells. And with almost 300 million years of recorded species, we’ve also got a good picture of their evolution. This is a classic evo-devo story.
So, quick, here’s a general introduction to trilobite anatomy. First thing to know is that the ‘three lobes’ of the word ‘trilobite’ refer to the longitudinal divisions of the animal: a central axis with a lateral or pleural lobe on either side of it. There are also, usually, three transverse divisions: cephalic (head) segments, thoracic segments in the middle, and a pygidium or tail.
Basic anatomy of the dorsal surface of two trilobites. (Left panel ) The figure is based on a generalized olenelloid trilobite, which had a boundary between two distinct or heteronomous batches of segments located within the thorax, dividing the protrunk from the opisthotrunk. (Right panel ) Aulacopleura konincki displayed the homonomous trunk condition in which all trunk segments shared a similar morphology. A, anterior; Opi, opisthotrunk; P, posterior; Pyg, pygidium.
Not usually shown are the limbs. If you flip over a trilobite, you discover that each segment, except the anterior- and posterior-most, has a pair of biramous appendages — they’re branched legs, with one branch functioning as the walking limb, and the outer branch being lamellate (thin and flat) and probably functioning as a gill. They’re surprisingly uniform and consistent in general structure, from head to thorax to pygidium. One of the curious features of trilobites is that most species are marked by this homonomous condition (that is, maintaining identity or close similarity between adjacent segments), while most of the extant arthropods are strongly heteronomous, making strong distinctions in the structure of adjacent segments.
Major divisions of the anterior-posterior (a-p) body axis in trilobites. The letter M indicates an individualized segment morphotype. Colors indicate major morphological divisions along the axis, with shading approximating the degree of morphological difference between adjacent segments. Segments in red are cephalic, those in light blue are thoracic, those in dark blue are pygidial, and the terminal piece is in purple. Thoracic segments articulate with one another, whereas those in the cephalon and pygidium are conjoined.
Now here’s the cool bit: a generalized staging series for trilobites. There are some broad terms for different stages — protaspid, then meraspid, then holaspid — but this diagram makes it clear that growth was by sequential addition of new segments to the posterior end of the animal. This is not an unusual pattern: vertebrates also build segments sequentially from front to back, as do many insects (the short germ band insects), but others, long germ band insects like flies, build the whole collection nearly simultaneously.
Generalized trilobite ontogeny showing the boundaries of ontogenetic stages based on three aspects of the development of trunk segments: generation (Gn), articulation (Art), and morphology (Form). The generation state contains a poorly known initial stage that may have had a constant set of cephalic segments, the anamorphic phase during which new segments appeared in the trunk, and the epimorphic phase after which the exoskeletal segment number was constant despite continued molting. The articulation state is based on dorsal sclerite articulation pattern, with the onset of the protaspid stage marked by the development of the dorsal facial suture, onset of the meraspid stage marked by the onset of trunk articulation, and the onset of the holaspid stage marked by the completion of trunk articulation. The morphology state refers to the form of trunk segments, which in some trilobites are divided into discrete, heteronomous batches of anterior (protrunk) and posterior (opisthotrunk) segments. The site of the appearance of new trunk segments is shown for the first trunk segment only. Segment color scheme as in previous figure. Individualized segments, such as those that bore unusually large axial or pleural spines (i.e., a macrospinous condition), retained the same position relative to the cephalic margin following their first appearance, indicating that the site of appearance of new segments was subterminal, and the boundary between articulating and conjoined segments migrated posteriorly during the meraspid phase.
Development is the foundation of evolutionary change, and I can’t help but wonder how this pattern, and the unknown genetic constraints behind it, affected trilobite evolution. The early history of arthropods seems to be one of exuberant exploration of the potentials of that modular segmental organization, with trilobites tending to be more conservative than other arthropods. What that means is tricky to interpret: the more inventive arthropods still have descendants around, while trilobites are extinct without issue. But 300 million years is still a fantastically good run, and clearly they had the flexibility to survive major changes in geological history.
The real mystery is why the clade as a whole began to decline after the Ordovician, and how the end of the Permian could so thoroughly quench this gigantic group.
Hughes NC (2007) The Evolution of Trilobite Body Patterning. Annu. Rev. Earth Planet. Sci. 35:401–34.
*By the way, I recommend digging in fossil beds as a great way to connect with the history of the planet with your kids. You can’t make it to Delta? There are quarries that will sell you crates of unprocessed rock, 30 pounds for $75, and you can take them apart in your back yard.
Well, I watched a lot of Good Times reruns, so I got the reference.
I will try to keep some of this information in mind when I take my daughter to the natural history museum next week. It might help me answer her questions.
When I was in school we took a stratigraphy field trip, and I found a perfect little rolled-up trilobite mostly free from surrounding matrix and everything. It rolled right out when I was digging. I still have it in my desk drawer. So cute.
Also, trilobite cookies
Trilobites are the coolest things ever, and I’m consistently peeved that they’re extinct. As a boy I used to play in the sand with what we called “roly poly bugs” (Armadillidiidae) and in my mind they were always l’il trilobites.
Also I’d really like to know what a trilobite tasted like. I want it to taste like crab. Is it possible for anyone with some expertise to reasonably speculate about what such a critter would taste like?
(Cross posted at ScienceBlogs)
Yeah, apparently it’s a thing that the Cambrian Period couldn’t have happened and trilobites disprove evolution– at least, that was the claim from the creationist that emailed me recently.
Thanks for this, PZ. It’s very helpful!
Josh:
I like the way you think. Extinct animal, OM NOM NOM!
It’s all about noms, A. If I saw a trilobite coming my way I’d whip out an ACME Trilobite Trap. Upside down box propped up by a stick with a string on it, ramekin of melted butter placed underneath. Sign would say TRILOBITES BATHE FREE!!!
Limulus is the closest living relative of the trilobites (p. 158)–a second cousin, perhaps. Its larva has been known for a century as “the trilobite larva” and does, indeed, have a passing resemblance to the protaspis stage of my own animals. This could be my best chance to find out what trilobites actually tasted like! I ordered the dish. When it arrived I was surprised to find the whole creature had been steamed, and it looked very unappetizing. My amazement increased as the underside of the head-shield was lifted outward–what we would call the doublure in trilobites–and there inside the head was the edible bit of the animal: big yolky eggs. Horseshoe crabs evidently carried their eggs in the head region, unlike shrimp and other crustaceans that carry them under the thorax. This was exactly the same position as the inflated blubs on the front of the trilobites; circumstantial evidence, of course, but much better than no evidence at all. And the taste? Even mixed with abundant noodles it was rancid and intense. I like to think trilobites would have tasted sweeter. — Richard Fortey, Trilobite!: Eyewitness to Evolution
Drat. I forgot to add the blockquotes. Everything at 8 is Richard Fortey.
Aaaah *nostalgia*, a romerogram, from the ancient times when phylogenetics still was an art and not a science… *blink* what? Furongian? L[u]opingian? WTF, this must be from 2004 or later. Trilobite researchers still make romerograms???
(Romerogram: named after the great & mighty Alfred Sherwood Romer, the most famous vertebrate paleontologist of his time and well beyond. Wrote the book on vertebrate anatomy and the book on vertebrate paleontology, both in many editions and later reprints. Romerograms represent groups, often paraphyletic ones, as bubbles that are usually drawn out at one or both ends; the widths of the bubbles represent diversity or importance or something in an impressionistic way, never actual species counts or anything else quantifiable; bubbles often arise from stippled lines that spring forth from question marks. The whole epoch of romerograms ended in phylopessimism… except it evidently still hasn’t ended for trilobite researchers. ~:-| )
The romerogram actually makes clear that both of these things didn’t happen this way. The beginning and the end of the Furongian look like major events there, then there’s the beginning and the end of the Middle Ordovician, then the well-known mass extinction event at the Ordovician-Silurian boundary kills off the remnants of two whole orders and decimates a third, then the beginning of the Přídolí (…I just wanted to write that word! ^_^ ) unexpectedly takes out that third one completely, and then both the Kellwasser and the Hangenberg events strike (the former in the Late Devonian at the Frasnian-Famennian boundary, the latter at the Devonian-Carboniferous boundary), leaving only one order for the whole Carboniferous and Permian till it croaks in the mother of all mass extinction events.
♥!
Possibly more like spider and scorpion and horseshoe crab and sea “spider” than like crab. But the phylogenetic position of the trilobites isn’t entirely clear. :-)
Thanks, Hekunicat. What a disappointment! I will replace the sign in my Trilobite Trap with FREE CREMATION FOR TRILOBITES.
Recommended.
…What? No! The horseshoe “crabs” are arachnids! They’re no closer to trilobites than spiders are!
Or does he mean “they’ve changed the least” by “closest relative”? That would get very subjective very quickly, though.
I love this blog. And I love the commenters.
Commenter A: I wonder what (…some really esoteric thing…)
Commenter B: Well, according to (……) the answer is (……).
Commenter C: True, but (……) suggests (……) and I’ve always thought (……).
Commenter D: But what about the MENZ?
Commenters A, B, and C: Fuck off, cupcake.
Yeah. I love this blog.
Go House Heterodyne! Trilobites forever!!!
I’ve been in love with trilobites since my fossil collecting Aunt took me to the Devonian Silica shale quarry near Sylvania Ohio. My favourite species is Phacops rana (commonly found in the Silica Shale) in case you were wondering, but Elrathia is a close second.
Yes. As we look for similarities in a creature’s body, and even environment, we can make a reasonable guess as to how it might taste, especailly if we know its diet.
A great example of this comes from a noted Professor. He used the data before him to deduce the taste of one of the most improbable things we could speculate the taste of. I’ll let his quote speak for itself: “And therefore, by process of elimination, the electron must taste like grapeade.”
(Yes, that was all bullshit just so I could do my lame joke)
So I am wondering (not having read the paper) that the different developmental stages are also representative of different species lines of trilobites. For example, I think there are trilobites with only a small # of defined segments, and those could be produced by maturing at an early developmental stage.
Johnny Walker, hooray, Johnny Walker. What? Sorry, I’m an excitable Spañard. Carry on!
That was one cool thing about growing up in western NY. Walk to the creek and look for trilobites.
Of course you have to sift through the trash of all of the brachiopods, the occasional ammonite, corals, and of course the weed of fossils, crinoids. Damned crinoids.
Foot thick concrete-solid layers of 100% compressed crinoid.
Pesky stuff.
(county hall in Buffalo, formerly city hall, has outdoor walkway walls and steps built from that thick crinoid layer. Inside you might stumble across a neglected closet-like “map room” – Grover Cleveland’s office. Fossils everywhere.)
I was 8 years old in 1978, and I approve of the joke.
A few years after that, my 6th grade science class took a field trip to dig up fossils of trilobites and other organisms. Very cool.
Re. the taste of trilobites:
I’m not sure how well direct comparisons would work, since taste depends on diet as well as genetics. However, given how small some of them are, you’d want to eat those whole. They’d be a little crunchy. Kind of like grasshoppers.
Dinosaurs, on the other hand, most likely tasted like chicken.
In the old-things-sitting-on-desk contest: I have meteorites nine to ten times older than that, and could probably dig out a few pre-solar dust grains that are older still. But they were never swimming through the Panthalassic ocean.
I did not know there were so many species of trilobite. I thought they were all just… trilobites. I really do feel enlightened; thank you!
(More books on the famed reading list.)
Why trilobites went extinct
(YES I KNOW IT’S STILL FUNNY)
Y’know, awe over handling an object hundreds of billions of years old never struck me until reading this post and thread. Now I find myself envious of those who have done so (cf. michaelbusch
While it’s true that Limulus is certainly not a close relative to trilobites, they are also not arachnids. Arachnids and horseshoe crabs (and pycnogonids) are different lineages of chelicerates.
Carlie, what the heck ARE those things?
Is the larva of Limulus called a ‘trilobite larva’ because they look like trilobites, or just because they too have three lobes?
isopod crustaceans
isopod crustaceans
Man… what will Apple think of next?
(sorry. it was either that or a lame “Is Apple suing them?” joke.)
@Tony:
Technically speaking, the oldest things in the universe are some of the neutrinos sleeting through your body right now and a bunch of the electrons. They’re all just a bit older than those protons that haven’t fused since baryogenesis. Of course, we’re talking about less than a second out of 13.77 ± 0.06 billion years. But some of those electrons and protons are almost everywhere (except in the cores of stars).
The meteorites are 4.567 billion years old, with a spread of maybe ten million years, so they’ve been around for 33% of the age of the universe. Most of the presolar grains are a few hundred million years older than that, so they’re still only 37% the age of the universe or less.
The trilobites did pretty well – the lineage survived from between 4% and 2% the current age of the universe ago.
@myself @30:
Also, you can’t really handle the presolar grains. Most of them are only a few microns across, and need to be extracted from larger meteorites by the arcane techniques of geochemistry.
If I ever have a grandkid, I am so going to send out for a crate of fossils!
–
And they work for the Sleeper in the Pyramid.
–
michaelbusch:
Ok, I will settle for being envious that you have 4.5-5 billion year old meteorites on your desk :)
Oh, sure, but was that meteorite ever walking, eating, mating, and thinking deep thoughts about whether that shadow was going to eat it?
I just realized I wrote ‘hundreds of billions’. Egads. Even though I am not very knowlegeable about many scientific areas, I knew the universe is @12-14 billion years old. I think I was mixing up millions with billions. Oops. Ah, my brain…
Deep Rifts 3.0-> trilobites vs meteorites. Grab yer popcorn, peanuts and peas.
Meteorites may contain the deep fried remains of extrasolar trilobites. For a sufficiently small (homeopathic) value of may.
PZ
*Raises hand*
I live on an old farm with a couple mounds of strip-mine tailings from the 1900s. Unfortunately, it’s all Carboniferous Period so all I have fossil-wise is loads of stems of some kind of scaly-trunked plant and little leaves. The good news is: I have thousands of fucktonnes of them. I long for trilobites. I grew up in an area with loads of bellemnites – now that was cool.
On’t you mean 6023 years old?
I came to this comments section wanting to impose a strident and stern rule: only those who own a trilobite fossil may comment! And then I found the comments were already from fossil and meteorite fragment owners, often scientists with a splash of paleo-gourmets. Lovely comments!
Me? I just have a bit of rock in a trunk somewhere with a trilobite on it. Dang I’m gonna go fishing for that one now though!
I wonder what trilobites taste like?
Shrimp? Horseshoe crabs?
Oh, and while we’re on the topic of being awestruck by old stuff – anyone who hasn’t seen David Attenborough’s show about his piece of amber, get thee to an Attenboroughry!
@PZ:
As I said, yours wins all the ancient swimming records (I don’t know the different species that well – did Elrathia like to swim or burrow more?)
@Tony:
Billions and billions… [/Carl Sagan voice]
Trilosong
copyright 2012
Martin Richard
So tell me, little trilobite,
Of those old Devonian days,
Five hundred million years ago,
When you walked beneath the waves.
When you were just a trilokid,
Did you play with other triloboys?
Did trilodads say, “Go outside,
Or stop that awful trilonoise.”?
Did trilokids have triloboards
For awesome trilomotion?
Did trilomoms say, “Be careful now,
When you go to cross the ocean.”?
Triloschool was easy since
You had much less to remember.
It was a half a billion years before
The first day of September
Trilomath? A piece of cake!
You only had to count to three.
And since it hadn’t started yet,
There was no trilohistory.
What kind of trilokid were you?
Were you rowdy? Were you docile?
Did you ever think, “When I grow up,
I want to be a fossil!”
“That’s cool!” You thought, “I’ll turn to stone
And hide out on the ocean floor.
“I’ll be the first to see a fish
And every kind of dinosaur.”
“I’ll watch the mammals nurse their young,
And raise them in their hairy way.
The sabertooth will come and go.
Now doubt he’ll die of tooth decay.”
“And somewhere deep in Africa
Some apes will start to walking.
And once they figure out just how,
They’ll never stop their talking.”
“Some human will discover me,
Beneath my sheets of stone grown cold.
The wise will hear my silent song:
Man is young; the Earth is old.”
In an earlier epoch of the Anthropocene, two decades ago, I wrote “Trilosong” for two sets of brothers, representatives of the young of our species. They now care for their own young, so I hereby rededicate an updated “Trilosong” to my favorite members of our next human generation: my friend Liam, six years old, and my nephew Martin, seven.
*headdesk*
*looking for health-related excuses for forgetting the term Chelicerata*
*more headdesking*
Awesome!
That’s so sad :.-(
Thread won, were it not for the mention of peas.
Boffo. A good one.
–
500 Ma ago is in Epoch 3 of the Cambrian, probably in the Guzhangian Stage, otherwise in the Drumian. (…The Cambrian/Ordovician boundary has moved up a lot since I checked last time. o_O )
400 Ma ago, though, is in the Emsian Stage of the Early Devonian Epoch. So you could just use that.
Otherwise, the song is awesome. :-)
Marcus Ranum:
See #8.
I was about 6 or so when Good Times was on TV, so I laughed at the joke – funniest thing all day!
PZ should note that the connection of Jimmy Walker and “Dynomite!” was perpetuated by the Beastie Boys on Paul’s Boutique.
I also like trilobites – here is one Phacops rana I collected from the Devonian Mahantango Formation in Milesburg, PA.
And I grew up with trilobites and dreamed of riding my bike to PA in hopes of finding cool plant fossils.
The rocks are always greener I guess.
word added to personal lexicon
I have no fossil, but I once owned a bit of char-ish rock from the K-T boundary (the young whippersnappers have renamed it the Cretaceous/Paleogene boundary now. Bastards!).
I mailed it as a gift to Stanislaw Lem (yes, that Stanislaw Lem) but *forgot* to include the note saying what it was, so he probably threw a pece of dinosaur ash in the garbage.
.
You should go up to northern Canada and chip loose a piece of 4.01 billion year old bedrock to keep as a paperweight. But if you are really smart you should go to northern Canada and chip loose a big diamond from their kimberlite deposits.
.
In theory, impact ejecta from planets of other stars of the same star association whence the sun came may have entered the solar system and hit one of “our” planets or protoplanets. there is a non-zero chance life can be transported between planetary systems inside the same star association this way.
But impact ejecta from other exoplanets (not part of the star association) …not very likely.
“pece” should be “piece”. D’oh!
I remember going on a fossil-collecting trip near one of the Finger Lakes in upstate New York. I found some brachiopod-shell imprints and fragments of trilobite skins. The imprints were about 1 cm long and wide, were more common, and looked something like scallop shells. The trilobite skins suggested an owner length of about 2 cm.
Trilobites could roll up like pillbugs. I remember lots of pillbugs from my childhood.
As to adding segments on one’s rear end, that’s the usual mechanism for all three segmented phyla: arthropods, annelids, and vertebrates. That’s not enough to indicate homology, because that’s a logical place to add new segments. However, we may eventually be able to work out whether or not the molecular mechanisms are homologous.
I have a few thalassinoides I found out around Bridgeport, TX where they were developing (I believe that’s a code word for fucking up a field) a subdivision and had bulldozed quite a pile of shale. My favorite section is studded with about a dozen gastropod shells in various orientations. If you’re in the DFW area of Texas, I’m sorry for you, but as a consolation, Route 380 heading west from Denton has some damned nice road cuts through Cretaceous rock which transition to (if I remember correctly) Pennsylvanian formations somewhere near Jaxboro. Well worth a few hours screwing around just on the shoulder of the road.
One reason I love horseshoe crabs is how much they remind me of trilobites.
Late to the thread again. Sigh.
Ah, well. If anyone reads this far, a cool place to check out in Locust Grove, Ohio is a little rock shop called House of Phacops. It’s just a couple of miles from Serpent Mound, and they deal in fossils, Native American artifacts, and locally-found impactites from the Serpent Mound crater. Cool stuff for everyone!
The proprietor of the shop once put together a trilobite display for the Smithsonian and is still considered one of the experts in the field. The Smithsonian has since changed to a different display, so you won’t see his work there. Instead, they gave it back to him, and it now covers the back wall of the shop.
Incidentally, my husbeast and I also collect rock specimens of all sorts–fossils, minerals, crystals, meteorites, and impactites. I’m going to email a link to that quarry site to our local mineral club!
Unfortunately, while we’ve found trilobite pieces, we’ve only found one complete specimen. I found that as a teenager, and gave it to my mother. On the plus side, we have found some gorgeous Plumalina plumaria here in Ithaca, and also some local (not diamond-bearing) Jurassic-era kimberlite!
Went to U-Dig last summer. Had a fantastic time. The first hour of digging was a bit slow because I’d never been fossil hunting before and didn’t have “eyes” for it. After I found a few, they just started jumping out of the rock. Found a couple dozen trilobites in the matter of hours. I had grand plans of ordering several crates of shale and tiling my floor with trilobites when I was done.
There’s another quarry just down the (dirt) road called A New Dig that is open Sundays while U-Dig is closed Sundays (for those who might be planning a trip). Both quarries will sell trilobites directly, but that takes half the fun out of it.