chelicerate

4

Scorpiones, Scorpio, Scorpion…

It’s hard to get a good picture of a scorpion - they’ve just got so much going on. Here, at least, are four images that show some key features: chelicerate mouth-parts, claws (chela) like an unrelated lobster, and tail with a sting segment (telson) and sting (aculeus). Fun creatures…

Scorpions have been on our little planet for an awful long time with the earliest evidence, fossils from the Silurian, around 450 million years ago, long before vertebrates began their land invasion. Some of these were real beasts up to about one metre (three feet) long, unlike today’s well over 1000 species which are usually less than 10 cm (3 in) long. Thankfully.

Here the images show two species and there’s an obvious difference in two of the images that clearly differentiates them. Know what it is?

Scorpions are one of the Many Little ancient Things.

vedajuno  asked:

Trilobites are pretty much a staple of paleontology and yet they're almost never talked about. What can you tell me about them?

Trilobites were one of the first major groups of animals to establish themselves on the planet Earth, but they’ve never really gotten their due - and their story isn’t a particularly happy one

 Trilobites are classified in their own unique subphylum of Arthropoda, the group that includes modern-day insects, arachnids, crustaceans, and myriapods.  None of these animals are descended from trilobites, who have no direct descendants alive today.  (The modern-day horseshoe crab, while sometimes mistaken for a descendant of trilobites, is actually more closely related to spiders.)

Some of Earth’s earliest known animals, trilobites originated in the Early Cambrian, some 540 million years ago.  The first known trilobites show all the features of later specimens, indicating that even earlier transitional forms exist, but have not yet been discovered.

The trilobites are named for their “three lobes” - the left, right, and central sections into which the thorax of the exoskeleton is divided.  Like modern-day insects, trilobites were divided into three distinct parts - the cephalon (or “head”), the thorax, and the pygidium, a fused segment that may or may not have borne legs.

Wait, they had legs?

I genuinely never knew this.  I thought the “lobes” were how they got around, that they kind of crept around on the ground by wiggling their– oh my God.  This is mind-blowing.  And look, at the top you can see preserved antennae!  I never knew they had those, either!

Holy crap, you can even see the outlines of the legs on the specimen preserved at the bottom!  Am I the only one who never knew this?  Was I the only person who was imagining trilobites wrong his whole life?

Well, regardless, the vast majority of trilobite fossils are shells discarded after molting, composed of only the larger pieces that would have stuck together for a while after such a process.  I guess it’s understandable that I had such a plebeian understanding of trilobites for so long.

Almost all trilobites had large and complex eyes - some of the first to develop in animals.  They likely had very good eyesight, allowing them to spot predators on the approach - or their own prey.

Trilobites inhabited a wide variety of lifestyles.  Some were bottom-dwelling crawlers who scavenged from fallen carcasses; others filter-fed from the silt; still others were predators; and others were active swimmers who fed on plankton.  Some of them, like Phacops rana, defended themselves from predators by rolling into balls of impenetrable armor; others developed more elaborate defenses, like the “trident” of Walliserops trifurcatus.

You might recognize some of the examples in the above list as the roles and adaptations taken on today by crustaceans, the dominant group of marine arthropods in our modern seas.  You might also remember that earlier in this post, I said that trilobites have no living descendants.  That’s not a coincidence.

Trilobites survived through the Cambrian, Ordovician, and Silurian, undergoing explosions of diversity and dominating the prehistoric seas.  Then, the Devonian mass extinction occurred.  It’s uncertain why this extinction occurred, but a great deal of Earth’s life was wiped out, including every order of trilobite - except one.  The order Proetida managed to struggle on into the Carboniferous, but their foothold was already lost; other groups of arthropods quickly filled all the niches that trilobites had abandoned, and the trilobites were completely extinct by the end of the Permian period.

While the trilobites may be long extinct, their strange and alien anatomy still fascinates paleontologists today - even if the public may not be as enthused.  I think it has a great deal to do with the fact that there are just so damn many trilobite species, most of which are pretty indistinguishable at first glance.  However, as you can see from my reaction above, there’s still a lot to learn about these ancient arthropods - and a lot of it may be right under our noses, waiting for us to see it.

axew  asked:

Hey there, I know we have never talked before but I got a request and I have to make a gifset with all the crustaceans-like pokemon in pokemon amie so I asked my followers if they know about crustacean and stuff and someone told me that you would probably know about that... Like, I know Krabby and Kingler are but I'm not sure about Clauncher and Crustle even thought Crustle has 'CRUST' on its name haha so yeah I was wondering if you could explain/help with that c: Sorry about my messy english.

Hey there! I’m always happy to talk about this kind of stuff :D

Crustaceans are a huge huge HUGE group within the arthropods and include animals such as crabs, lobsters, crayfish, shrimps, prawns, and krill, as well as some other animals such as barnacles, sea monkeys (brine shrimp) and copepods (like plankton from spongebob)

Essentially, if it has a segmented shell, lots of legs, and lives in the sea, then it’s probably a crustacean (there are some exceptions, and I’ll come to that in a moment)

The following pokémon are based on crustaceans:

  • Krabby and Kingler (Crabs)
  • Dwebble and Crustle (Hermit Crabs)
  • Corphish and Crawdaunt (Crayfish)
  • Clauncher and Clawitizer (Snapping Shrimp)
  • Binacle and Barbacle (Barnacles) 

Now, the exceptions are found within fossil types. Kabuto and Kabutops are based on horseshoe crabs, however, the name horseshoe crab is misleading because horseshoe crabs are NOT crabs and NOT crustaceans. They are actually in the same group as spiders and scorpions, the chelicerates. So, Kabuto and Kabutops are not crustaceans.

Also, Anorith and Armaldo may look like crustaceans, but again, they are not. They are based on the anomalocarids, a very ancient arthropod group which is long extinct. Anorith and Armaldo are not crustaceans.

I hope that helps! :)