Ancient marine animals known as brachiopods may have had a more inventive past than previously thought
A recent study conducted by researchers from the University of Bristol, the Open University, and the China University of Geosciences reveals insightful details about brachiopods, an ancient marine animal. Contrary to their limited representation in terms of species numbers, brachiopods were found to have experienced evolutionary progress in various directions, reports ScienceDaily.
Brachiopods, often referred to as lamp shells, were dominant creatures on the seabed during the Palaeozoic era, spanning from 540 to 250 million years ago. These filter-feeding organisms ranged in size, some being quite small while others were larger with thick shells and extended lifespans. The researchers discovered that brachiopods encountered a significant setback during the end-Permian mass extinction, around 252 million years ago. However, instead of facing complete extinction, they began exploring new ecological behaviors and shell shapes.
The team's study, published in Nature Ecology & Evolution, emphasizes that while modern oceans house an extensive array of molluscs comprising over 50,000 species, brachiopods remain a rarity with only 394 known species. The researchers found that despite innovations in brachiopod form and function, this didn't result in a significant increase in species numbers. It appears that after the mass extinction, brachiopods were unable to widely spread and diversify like their mollusc counterparts.
Professor Michael Benton of the University of Bristol's School of Earth Sciences emphasizes how the survivors of the mass extinction could have vanished entirely, as molluscs surged in terms of success. This resonates with the belief that brachiopods remained scarce due to their confinement to a limited range of living habits. However, Dr. Tom Stubbs from the Open University notes that the surviving brachiopods continuously experimented with new ways of life. Specifically, a group known as the terebratulids flexibly explored diverse body shapes and ecological functions over time. Nevertheless, this innovation did not lead to a substantial rise in overall diversity.
The researchers conducted an extensive analysis by studying a vast database comprising more than 1000 genera of brachiopods spanning 250 million years. They meticulously examined various measurements, including overall shell shape, external features, and internal anatomy, to determine the key characteristics of each brachiopod group during different periods. This analysis provided insights into the diversity of shape, also known as disparity, which was then compared to species or genera counts to gauge evolutionary progress.
Dr. Zhen Guo from the China University of Geosciences underscores the importance of understanding modern biodiversity within the context of its historical development. Exploring the rich past and evolutionary innovation of brachiopods helps shed light on their limited species numbers in the present. The researchers' discovery that disparity and diversity are decoupled in brachiopod history was unexpected yet significant. While brachiopods showcased impressive inventiveness by evolving diverse shell forms, this didn't translate into a substantial increase in species numbers.
The study's findings provide valuable insights into the evolutionary dynamics and the delicate interplay between ecological innovation and species diversity within ancient marine ecosystems. By assessing the intricate history of brachiopods, scientists can deepen their comprehension of biodiversity and the underlying processes that shape it.
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