By leveraging trace fossils as surrogates for body fossils, paleontologists have undertaken an analysis of the morphological characteristics of Ediacaran-Cambrian biota.
A reconstruction of early Cambrian ocean life in South China. Image credit: Dongjing Fu.
The epoch commonly referred to as the Cambrian explosion is widely characterized as the period in Earth’s geological narrative during which animal body plans demonstrably emerged.
The prevailing consensus among numerous investigations places this pivotal event between 541 and 530 million years ago, marking the inception of the Cambrian period.
“The Cambrian explosion represents a singular juncture in the evolutionary trajectory of life, presenting a multitude of unresolved scientific inquiries,” articulated Dr. Olmo Miguez Salas, affiliated with the Universitat Barcelona, and Dr. Zekun Wang from the Natural History Museum in London.
“In the pursuit of understanding the biodiversity of this epoch, the predominant approach in paleontological research tends to concentrate on the examination of organisms possessing calcified structures.”
“Conversely, the investigation of trace fossils unlocks the potential to ascertain the behavioral patterns of organisms, both those with rigid exoskeletons and those with pliable bodies or limited skeletal development, as preserved within the stratigraphic record.”
“The evidence gleaned from trace fossils furnishes invaluable insights into evolutionary phases when fauna characterized by soft tissues were the dominant life forms.”
“The imprints left by these organisms are direct reflections of their behavior, which in turn is dictated by their habitat and their adaptive responses to environmental stimuli.”
“Consequently, these traces serve as key indicators of the paleoecological conditions under which the originating organisms existed.”
Within their comprehensive study, the researchers meticulously examined trace fossils dating from the Ediacaran-Cambrian transitional period, an interval recognized for its profound paleoevolutionary significance and as a critical turning point in the development of complex life forms on our planet.
This transitional epoch witnessed a dramatic transformation in biodiversity, accompanied by substantial alterations in organismal morphology and ecosystem architecture.
“The Ediacaran biota was predominantly composed of intricate, multicellular organisms lacking rigid skeletal structures,” elaborated Dr. Miguez Salas.
“The transition into the Cambrian era entailed the demise of a significant portion of the Ediacaran fauna, succeeded by a rapid proliferation of complex, multicellular life forms that exhibited the development of hard anatomical components (such as exoskeletons).”
“This evolutionary crucible represents the origin from which the majority of modern animal phyla subsequently diversified: an phenomenon broadly understood as the Cambrian explosion.”
The research findings indicate a prevalence of organisms with attenuated body geometries approximately 545 million years ago, during the Ediacaran period.
“These ancient creatures likely possessed hydrostatic bodies supported by coelomic cavities, featuring a distinct anteroposterior axis, musculature, and potentially segmentation,” posited Dr. Miguez Salas.
“Furthermore, these organisms were capable of directed movement (directional locomotion) and likely possessed sensory apparatus that facilitated navigation and foraging across varied substrates within environments characterized by microbial mats.”
“Therefore, the widely accepted timeline for the Cambrian explosion and its associated evolutionary ramifications may require revision, potentially extending further back in time than previously theorized.”
The scholarly publication detailing the team’s research is accessible in the esteemed journal Geology. You can access the paper here.
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Zekun Wang & Olmo Miguez-Salas. Quantitative decoding of Ediacaran locomotory trace fossil morphologies: Evidence for the emergence of slender anterior-posterior body profiles. Geology, published online June 9, 2025; doi: 10.1130/G53332.1
