Trilobites may not appear to be cuddly creatures, but when it came to mating, one species of these now-extinct arthropods, which resembled enormous, swimming potato bugs wearing Darth Vader helmets, would come together for a brief embrace, according to recent research.
Trilobites dominated the fossil record of early sophisticated animal life because of their readily petrified exoskeleton.
However, trilobite appendages and the architecture of their underside are seldom preserved, making it impossible to deduce their mating and reproductive habits.
Trilobites employed clasper-like appendages for breeding
Wes Warren/Unsplash
Until recently, current arthropods were largely utilized as analogs to infer trilobite mating behavior, but a new study published Friday in Geology detailed the finding of a specialized limb in a mature male trilobite species, which throws light on trilobite mating habits for the first time.
A detailed examination of a fossil specimen of the trilobite Olenoides serratus showed two pairs of unusually shortened appendages in the center of its body.
Each of these appendages is interpreted as a clasper-like arm that adult males would employ during mating to hold females and guarantee that the male is in the ideal position for artificial insemination of the eggs, as per ScienceDaily.
"The male has to be in the appropriate posture whenever the eggs are delivered," study lead researcher Sarah Losso, a doctorate candidate in biological and evolutionary science at Harvard University, told Live Science.
"Because it improves the possibility that his sperm will fertilize the eggs, which raises the chance of successful mating."
There are over 20,000 species found of trilobites, which lived on Earth for around 270 million years before becoming extinct approximately 252 million years ago at the end of the Permian epoch.
O. serratus has been studied for a century after paleontologists discovered its fossil remains in the Burgess Shale.
Given their comparable appearance and behaviors, horseshoe crabs are widely utilized as modern analogs for trilobites.
This particular trilobite limb is remarkably equivalent to the claspers that male horseshoe crabs have and use to grab onto the spines of a female during external fertilization.
While it was previously assumed that trilobites had mating habits similar to horseshoe crabs, this fossil finding gave proof of physical parallels in their reproductive techniques.
Trilobites and horseshoe crabs are not especially related, yet they have a similar general structure and live in comparable maritime settings.
It's similar to how a bat and a bumblebee can both fly.
They both have wings, but the wings themselves are extremely different in terms of construction and operation.
According to Javier Ortega-Hernández, co-author of the study, "if you are a helmet-looking marine species that lives on the bottom, there are so various other ways that may effectively mate externally."
This investigation indicated that O. Losso believes serratus' strange appendages were claspers.
During a mating session, the male is likely to go on top of the female, with his head aligned with the female's trunk, so he's offset more toward the rear, but on top of her, according to Losso.
These spines protrude from the tail in this place on the exoskeleton.
