The new Lower Ordovician fossil spores, which date back to about 480 Ma, is intermediate in their character between the controversial Cambrian forms, and the well-accepted plantspores from Silurian and later Ordovician deposits. This linkage combines fossil spores and molecular data, which helps to explain why megafossil plant axes didn't appear in geological records until 75 million years after the Silurian. Credit to Paul StrotherAccording to a new Science report, the world might need to think differently about plants. Researchers took a fresh look into spore-like microfossils that have characteristics that challenge conventional knowledge about the evolution and evolution of land plants.The microfossils, which were found in rock samples taken in Australia over 60 years ago, are dated to the Lower Ordovician Period. They fill a gap of approximately 25 million years in our knowledge.This reconciliation supports an evolutionary-developmental model connecting plant origins to freshwater green algae, or charophyte algae, said Boston College paleobotanist Paul Strother, a co-author of the new report. The "evo–devo" model provides a better understanding of plant evolution, starting with simple cell division and ending at the initial embryonic stage. It does not make large leaps between species.Strother stated that he found fossils that linked older, less problematic microfossils to spore-like microfossils and younger spores derived from land plants. This helps align the fossil spore records with molecular clock dates, if we view the origin of land plants in a long-term process that involves the evolution of embryonic growth.Strother said that fossil evidence provides direct evidence of the evolution of the regulatory and developmental genes of plants. This begins with the evolution and development of the plant spore, which leads to the creation of tissues and organs and finally to complete plants, perhaps akin to modern mosses.Strother stated that spores are an important part of the evolution land plants. There is no gap between molecular dating (or fossil recovery) in the fossil record. We can see a new evolutionary step, from simple cellularity and complex multicellularity, if we eliminate that gap.Strother said that researchers and the general public might need to reconsider their views on the origin of terrestrial plants, which is a pivotal step in the evolution of life from water into land.The new Lower Ordovician fossil spore assemblage, approximately 480 Ma, is intermediate in nature between the controversial Cambrian forms, and the well-accepted plantspores from Silurian and later Ordovician deposits. This linkage combines fossil spores and molecular data, which helps to explain why megafossil plant axes didn't appear in geological records until 75 million years after the Silurian. Credit to Paul StrotherStrother stated that we need to stop thinking about the origin of land plants in a single time and instead incorporate the fossil record into an integrated evo-devo model describing genome assembly over millions of years during Paleozoic Eraspecifically within the Cambrian, Devonian divisions. This requires serious reinterpretation of problematic fossils, which were previously interpreted as fungi and not plants.Clinton Foster, co-author at the Australian National University, was the first to describe a spore-like microfossil assemblage from a deposit that dates back to the Early Ordovician age, approximately 480 million years. Strother said that this material fills in the gap of 25 million years in fossil spore records, linking older, more problematic forms to well-accepted younger spores.Foster and Strother examined fossil spore populations from a rock core that was drilled in northern Western Australia in 1958. These microfossils contain highly resistant organic compounds within their cell walls, which can structurally withstand burial and lithification. They were examined at Boston College and at the ANU's Research School of Earth Sciences using standard optical light microscopy.Strother stated that fossil spores are taken from rock drill cores in order to reconstruct an evolutionary history of plants. This includes the time period from when plants evolved from algal ancestors. "We can independently age these rock samples so that we can study evolution by studying changes in the types of spores over time."Molecular biologists also study evolutionary history over time using genes from living plants to determine the timing of plant origins. They use "molecular clocks", which measure evolutionary divergence by the average rate at which mutations accumulate in a species’ genome.Strother said that there are large discrepancies between fossil data and molecular clock dates. There are also similar time gaps between the oldest and actual whole plant occurrences.These gaps led to hypotheses about a missing fossil record of the earliest land plants," stated Strother.Strother stated, "Our work seeks some of these answers by integrating fossil spore records into an evolutionary developmental model for plant origins from Algal ancestors."Further exploration: Billion-year-old fossil uncovers missing link in evolution of animalsAdditional information: Science (2021): A fossil record showing land plant origins from Charophyte Algae, Science (2021). Information from Science: Journal A fossil record of landplant origins from Charophyte Alga, (2021). science.sciencemag.org/lookup/ 1126/science.abj2927
