A Carboniferous arachnid

This week has been a good one for chelicerate evolution. Here’s another fossil, Douglassarachne acanthopoda, which was creeping around in the forests of Illinois in the late Carboniferous.

Douglassarachne acanthopoda n. gen. n. sp., holotype and only known specimen FMNH PE 91366; for interpretative drawings and scale, see Figure 2. (1) Part, detail of distal femur and more-distal podomeres, showing nature of curved macrospines on lateral edge of distal podomeres, bases of macrospines on dorsal surface of femur; (2) counterpart, detail of posterior opisthosoma showing bilobed structure at base of anal tubercle.

What is it? I don’t know. The authors are unsure. It’s an arachnid, but it could be in the spider lineage or the harvestman lineage, or it could be its own weird thing. It’s spiderish, anyway.

Douglassarachne acanthopoda n. gen. n. sp., reconstruction of the possible appearance of the animal in life.

An Ordovician ancestor to spiders

On this Memorial Day, I’m going to have to have a discussion with my spiders about their distinguished, noble ancestry. It was kind of Nature to publish a study of their many-times-great grand uncles, an ancient euchelicerate named Setapedites abundantis, a common fossil found in Moroccan sediments that are about 478 million years old, which puts it right in the middle of the Great Ordovician Biodiversification Event, a key moment in the evolution of modern taxa.

This is not a spider, though. It belongs in the euchelicerata, the large systematic group that includes spiders, scorpions, ticks, horseshoe crabs, sea scorpions, and other extinct groups. As you might guess from the name, a key feature is the presence of chelicerae, anterior appendages that in spiders carry the venomous fangs. It also has a common feature we see in both spiders and horseshoe crabs, the fusion of the anterior segments to form a prosoma, with posterior segments forming the abdomen or opisthosoma.

While it’s a cool looking little dude, it’s marine and pretty remote from modern chelicerates. From the dorsal side, it looks like an undistinguished little crustacean, of a type that was probably swarming in Ordovician seas.

A, B MGL.102899 and interpretative drawing, articulated specimen in dorsal view. C, D MGL.102828 and interpretative drawing, articulated specimen in dorsal view. E, F MGL. 102872 and interpretative drawing, articulated specimen in dorsal view. Abbreviations: btg, bipartite tergites; mr, median ridge; pl, pleura; pr, prosomal rim; saxn, sub-axial node; sr, sunken region; t1–11, tergites 1–11; t, telson; tk, telson keel. Scale bars, (A–F) 1 mm.

Where it gets interesting is when it’s flipped over, and you get a glimpse of the mass of limbs.

A, B YPM IP 517932c and interpretative drawing (counterpart), articulated specimen in ventral view. C, D YPM IP 517932c and interpretative drawing, chelicerae, and labrum anatomy detail. E, F Close-up of the prosoma of MGL.102934 and interpretative drawing, in dorso-lateral view. G, H Close-up of the prosoma of MGL.102634 and interpretative drawing, in ventral view. I, J Close-up of the prosoma of MGL.102800a under alcohol and polarized lighting, and interpretative drawing, in ventral view. Abbreviations: 1–6, podomeres 1–6 of the exopod; ptp, pretelsonic process; bs, basipodite; bst, brush-like setae; che, chelate podomere; db, doublure; lb, labrum; ss, single setae; st, pair of setae. Chelicerae are highlighted in gray, endopods in blue, exopods in green, opisthosomal appendages in red, and the pretelsonic process in purple. Scale bars, (A, B) 1 mm; (C, D) 100 µm; (E–K) 500 µm.

In front of the jaws proper (labrum, lb) it has a pair of small chelicerae (che). These have since evolved into the massive, sharptoothed chompers you can see my tarantula using to turn a mealworm into macerated mush.

Setapedites wasn’t such a fierce predator. Here’s what it looked like.

Illustration by Elissa Sorojsrisom.

Cute, right? I don’t know why it’s drawn as a swimmer, though — with that anatomy, it looks more like a benthic organism.

The final bit of interesting information is that they mapped out the correspondences in the segmentation of this animal with other, similar fossils and the extant Xiphosurians.

Simplified extended majority rule tree of a Bayesian analysis chronogram of euchelicerate relationships, based on a matrix of 39 taxa and 114 discrete characters, showing the position of Setapedites abundantis within Offacolidae. Lineages extending after the Silurian are indicated with arrowheads. Schematic models of the body organization in Habelia, Setapedites abundantis, Dibasterium, Offacolus, and Xiphosurida illustrate the origin and early evolution of euchelicerate uniramous prosomal appendages and tagmosis. Roman numbers designate somites. Prosoma somites are highlighted in blue, pre-abdomen somites in yellow, abdomen somites in brown, and the possible anal pouch or post-ventral structure (pvs) in purple. Black dorsal lines indicate tergites and cephalotorax. Schematic model of Xiphosurida Offacolus, and Dibasterium from 45, Habelia

Also of note: Setapedites had biramous appendages, a feature that is mostly kind of lost in modern arthropods — the outer branch got adapted into gills and lungs and even wings.

I can’t help but notice that domestication and artificial selection turns wolves in little yapping Pomeranians, but natural selection turns shrimp into tarantulas.

Spiders blooming everywhere!

Mary spotted all these tiny yellow spiders all around the backyard. Apparently, a sac full of Araneinae hatched out in the last few days.

These are the equivalent of those kids’ show Minions. They’re all over, I can’t tell them apart, and they talk funny.

While I was out roaming in the yard, I spotted a few other familiar faces. This is Salticus scenicus, the zebra jumper. They were all over the walls.

Then there was this guy, Parasteatoda, who had caught a sowbug. It’s like having lobster for lunch.

Who knew spiders were so lucrative?

It’s like dealing cocaine. An arachnid kingpin, Lorenzo Prendini, curator of arachnids at the American Museum of Natural History, was arrested in Istanbul as he attempted to smuggle 1500 spiders and scorpions out of Turkey. The Turkish police aired a video showing how they tracked the criminal through the airport — looking like an obvious nerd, very suspicious — and then laying out bags and vials full of spiders and spider parts, like they were illicit goods bravely seized from a cabal of nefarious criminals.

They claim, “It has an estimated market value of around $10 million.” Wow. They threw him in a Turkish prison. Look at this smug badass.

He’s my hero.

Of course, they released him after a day when they noticed that he had permits for all of his biological specimens. I hope he’s now strutting around the AMNH like the Walter White or Scarface of arachnology.

Years ago, I was invited to debate one of Harun Yahya’s disciples in Istanbul — I turned it down without a moment’s thought because I figured taking an atheist position in Turkey would get me arrested (also, Yahya was such a fool that I would gain nothing from the encounter.) It’s too bad he’s in prison and his creationist organization dismantled, because now I might consider it for the opportunity to score a cool few million dollars in smuggled baggies full of dead spiders.

Hey, where did they get that market value of $10 million? Who would they sell them to?

What a pretty home you have!

One of the things Parasteatoda does is build cobwebs on the side of our house (yes, we have an orange house) that not only gathers bugs, but also windblown debris. They seem to like it, and will even add to it by hoisting bits of gravel and small twigs from the ground up to their nest, which will gradually become more cluttered over the course of the summer. It’s still early, so this tiny little spider mainly has scraps of flower blossoms to hide behind.

If she survives and thrives, she’ll add her egg sacs to the accretion.

I assume you can see her, just below the dark seed pod? She was hiding behind that, and I had to nudge her a bit to get her to come out.

Spider sex orgy, coming right up

This is the week! It was a busy morning in the lab, doing a complete spider cage cleanup, shuffling everyone around, sorting out males and females, and getting ready for the big sexual event scheduled for Thursday, when the virginal boys are introduced to the virginal girls, and we hope grand things happen.

The party takes a couple of days of preparation — tomorrow is the preparatory feast day, for instance. I’ll be posting all the details on Patreon, if you’re really interested.

P.S. When searching for an image to illustrate a ‘spider sex orgy’, make sure you’ve got Safe Search on. I didn’t, and now I have to go bleach my eyeballs. So many strange images, and virtually none of them included an actual arachnid…

Spider gluttony

I was checking out our compost bin, which is swarming with young juvenile spiders, and what jumped out at me was how fat they’re getting. These little spiders are growing fast and are turning into regular whales. This one, I noticed, had a secret stash — they’d corralled a bunch of baby isopods to snack on whenever they felt peckish.

Parasteatoda

Yum. All gathered into one spot, and tender and delicious nibbles, too. No wonder they’re getting so plump.

Personally, I’m feeling well satiated right now. I scheduled one class to turn in their final assignment last night, and another class to turn in their term papers tonight. I’d rather lick isopods off a compost bin lid than read any more student papers.