Scientists have just discovered four tarantula species with genitals so unusually long that they had to be put in a category of their own. Literally.
Their mating appendages are so extreme that researchers couldn’t cram them into any existing spider genus—so they made a new one: Satyrex.
In the world of tarantulas, male genitalia typically scales at about twice the length of the spider’s upper body. But these guys? Their palps—the sperm-delivery limbs—are four times longer than their cephalothorax (that’s head-plus-torso, for non-arachnologists), and almost half the length of their longest legs. In one case, that’s a 2-inch genital limb on a 5.5-inch spider.
“The males of these spiders have the longest palps amongst all known tarantulas,” lead researcher Alireza Zamani said in a statement. Zamani, an arachnologist at the University of Turku in Finland, co-authored the study recently published in ZooKeys.
He believes the adaptation might have evolved to give males a little distance from their partners during sex since female tarantulas are famously cannibalistic.
These Tarantulas Have Genitals So Large They Require a New Genus
It’s not just the palps that make these spiders notable. One species, Satyrex ferox, raises its legs and hisses at the slightest disturbance. It gets the “ferox” title (Latin for fierce) not for show, but for its full-on attitude and massive size.
The name Satyrex is derived from the combination of “satyr” and “rex.” Satyrs, the half-goat mischief-makers of Greek mythology, were often portrayed as overly horny and well-endowed. Rex, of course, means king. Combined, it’s a fitting name for the new rulers of the spider penis world.
The newly discovered tarantulas—S. arabicus, S. ferox, S. somalicus, and S. speciosus—were found hiding in rocky crevices and burrows across the Arabian Peninsula and the Horn of Africa. Zamani and his team found S. arabicus in Saudi Arabia, photographed S. ferox in Yemen and Oman, and described the other two in Somaliland.
A fifth spider, previously classified under a different genus (Monocentropus longimanus), has now been reassigned to the Satyrex family, thanks to its matching proportions.
In a field where genitalia often holds the key to classification, these spiders didn’t just stand out. They stretched the whole system. As Zamani put it: “At least in tarantula taxonomy, it seems that size really does matter.”
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