Paleontologists have adopted a cutting-edge digital fossil mining technique to examine over 250 fossil beaks from 40 ancient squid species. The findings indicate that there is no prolonged slow-moving change associated with the slower parietal layer, previously linked to the mass extinction event of late white matter around 66 million years ago. Early squid species had already established large populations, surpassing the biomass of both ammonites and fish. They evolved into intelligent and agile swimmers, contributing to modern marine ecosystems.
This lithograph features Loligo Forbesii, a squid species from the order Myopsida. Image credit: Comingio Mercuriano.
Squid are recognized as the most diverse and widely distributed group of marine cephalopods in today’s oceans, serving a crucial role in marine ecosystems as both predators and prey.
Their evolutionary success is generally attributed to the loss of a rigid external shell, a significant characteristic of their parietal ancestors.
Yet, their evolutionary beginnings remain unclear due to the scarcity of fossils from soft-bodied organisms.
The fossil record for squid dates back around 45 million years, with most specimens discovered consisting of fossilized statoris, or small calcium carbonites that assist in balance.
The early absence of such fossils has led to hypotheses that squid diversified following the mass extinctions during the Cretaceous period, approximately 66 million years ago.
Molecular studies of living squid species provide estimates regarding their divergence times; however, these estimates have become increasingly uncertain because of the dearth of prior fossil evidence.
In this recent study, Shin Ikegami, a paleontologist from Hokkaido University, and colleagues addressed these deficiencies using high-resolution grinding tomography and advanced image processing to digitally scan rocks as layered cross-sectional images, effectively revealing hidden 3D models.
This method was applied to Cretaceous carbonate rocks in Japan, resulting in the discovery of 263 fossilized squid beaks from 40 species across 23 genera and five families.
Results indicate that squid emerged around the boundaries of the early and late Cretaceous, roughly 100 million years ago, followed by a rapid diversification.
The authors assert that this newly uncovered fossil record significantly extends the documented origins of the two main squid groups: oegopsida extending back about 15 million years and myopsida extending as far back as 55 million years.
Early oegopsids showcased unique anatomical features that later species lacked, hinting at rapid morphological evolution, whereas Myopsids already displayed modern characteristics.
This study further indicates that late Cretaceous squids were more populous and often larger than their contemporaneous ammonite and bony fish counterparts. This ecological dominance might have triggered the radiation of bony fish and marine mammals roughly 30 million years ago, establishing squid as the first intelligent and agile swimmers that shaped modern marine ecosystems.
“In terms of population and size, these ancient squids were evidently proliferating across the oceans,” stated Dr. Ikenakamoto.
“Their body size rivaled that of fish, often even surpassing the ammonites found alongside them.”
“This demonstrates that squid thrived as the most abundant swimmers in the ancient seas.”
“These discoveries revolutionize our understanding of marine ecosystems in the past,” remarked Dr. Yasuhiro Iba from Hokkaido University.
“Squids were likely the pioneers of fast, intelligent swimmers that dominated the modern ocean.”
Study published in the journal Science.
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Shin Ikegami et al. 2025. The origin and radiation of squid revealed by digital fossil mining. Science E 388 (6754): 1406-1409; doi: 10.1126/science.adu6248
Source: www.sci.news
