Describing the find, Associate Professor Parry remarked, "As well as having their beautiful and striking golden colour, these fossils are spectacularly preserved. They look as if they could just get up and scuttle away." The new species honors Greg Edgecombe of the Natural History Museum in London and adds new depth to our understanding of megacheirans - an iconic arthropod group recognized for their large, prey-capturing appendages known as "great appendages."
Megacheirans flourished in the Cambrian Period (538-485 million years ago) and were largely believed extinct by the Ordovician Period (485-443 million years ago). This specimen, however, reveals otherwise, offering fresh insights into arthropod evolution, especially regarding how their specialized head appendages developed for various functions. Such adaptations include modern insect antennae, crustacean sensory organs, and the pincers and fangs seen in spiders and scorpions.
"Today, there are more species of arthropod than any other group of animals on Earth. Part of the key to this success is their highly adaptable head and its appendages, that has adapted to various challenges like a biological Swiss army knife," Associate Professor Parry explained.
Unlike other megacheirans, Lomankus features three elongated, flexible flagella on its front appendage instead of typical claws, likely enabling environmental sensing rather than hunting. The absence of eyes in Lomankus suggests it relied on this appendage to navigate and find food within a dark, low-oxygen habitat - a notable deviation from its Cambrian relatives.
"Rather than representing a 'dead end,' Lomankus shows us that megacheirans continued to diversify and evolve long after the Cambrian, with the formerly fearsome great appendage now performing a totally different function," added Parry.
Professor Yu Liu from Yunnan University, co-corresponding author of the study, noted, "These beautiful new fossils show a very clear plate on the underside of the head, associated with the mouth and flanked by the great appendages. This is a very similar arrangement to the head of megacheirans from the early Cambrian of China except for the lack of eyes, suggesting that Lomankus probably lived in a deeper and darker niche than its Cambrian relatives."
These head features align with structures in living arthropods, suggesting that the great appendage may be the equivalent of insect antennae or the mouthparts of spiders and scorpions.
The fossil emerged from New York's Beecher's Trilobite Bed, a site renowned for its exceptional preservation of trilobites within a rock layer conducive to fossil pyritization. At this site, low-oxygen conditions allowed pyrite to replace organic material, transforming the organisms into golden fossils. This dense mineral structure enables the use of CT scans to reveal intricate anatomical details, providing a three-dimensional reconstruction of the fossil.
Professor Derek Briggs, a co-author from Yale University, emphasized the significance, saying, "These remarkable fossils show how rapid replacement of delicate anatomical features in pyrite before they decay, which is a signature feature of Beecher's Trilobite Bed, preserves critical evidence of the evolution of life in the oceans 450 million years ago."
Research Report:A pyritized Ordovician leanchoiliid arthropod
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