@SocialJusticeHeals @Sheril Trilobites may be more closely related to Chelicerata (the group including horseshoe crabs, sea spiders, and arachnids) than to Mandibulata (the group including crustaceans and insects). But I don't know where the systematics is at now.

Some systematists have found via molecular analysis that some groups of arachnids are more closely related to horseshoe crabs than to other arachnids—that is, horseshoe crabs should be nested within arachnids, and the traditional definition of arachnids is obsolete.

However, other work has upheld the traditional interpretation that all arachnids are more closely related to each other than to horseshoe crabs. It's been kind of ping-ponging back and forth for several years.

@Sheril

for those interested, here's where I first heard about this: https://maximumfun.org/episodes/sawbones/how-horseshoe-crabs-probably-saved-your-life/

@2ck @Sheril

from this article
https://www.theatlantic.com/technology/archive/2014/02/the-blood-harvest/284078/

"The industry says that not that many of the animals die. Between 10 and 30 percent of the bled animals, according to varying estimates, actually die.."

But what is fucked up is that according to the article, they're only not harvested (i.e. killed) outright because the population is so valuable alive as a chemical source.