An ancient stone slab in Morocco has preserved a creature that could fill a crucial evolutionary gap.
In a study recently published in the scientific journal Nature Communications, a team led by Dr. Lorenzo Lustri from the University of Lausanne (Switzerland) has traced the ancestral creature of a highly diverse group of arthropods that includes modern spiders, scorpions, and horseshoe crabs.
Portrait of the ancestor of many modern arthropods – (Photo: NATURE COMMUNICATIONS).
Today’s scorpions, spiders, and horseshoe crabs belong to a vast lineage of arthropods that emerged on Earth nearly 540 million years ago, at the beginning of the Cambrian period.
“More specifically, they belong to a sub-phylum of creatures with pincers that are specially adapted for biting, grasping prey, or injecting venom, known as chelicerae. But what is the ancestor of this particular group?” Dr. Lustri raises the question.
This question has puzzled paleontologists since the study of ancient fossils began.
Many bizarre creatures from the Cambrian period and the subsequent Ordovician period have been discovered, but until now, none had enough similarities to modern species to be considered their ancestors.
Dr. Lustri’s team struck gold when they found the answer in an ancient slab in Morocco.
Named Setapedites abundantis, this new species represents a transitional evolutionary step between the earlier Cambrian forms and modern arthropods.
This creature measured only 0.5-1 cm and swam in the Ordovician seas approximately 478 million years ago.
Its anatomical features have provided insights into the initial evolutionary steps that led to the formation of a distinct group known as arthropods.
Thus, it can be said that it is the missing link for modern spiders, scorpions, and horseshoe crabs.
Setapedites abundantis in the Ordovician seas – (Graphic: NATURE COMMUNICATIONS).
The Cambrian and subsequently the Ordovician periods were phases marked by rapid evolutionary advancements of Earth’s animal life in oceanic regions.
While most of these life forms have been wiped out by mass extinctions, their descendants—with entirely different evolutionary patterns—form the foundation of today’s animals.
