Papers by Nidia Álvarez Armada
Irish Journal of Earth Sciences
Geoconservation is a burgeoning area of activity within the Earth sciences and the preservation o... more Geoconservation is a burgeoning area of activity within the Earth sciences and the preservation of significant fossil finds remains crucial for the advancement of palaeontological knowledge and protection of geoheritage. Here, we report on the discovery of an unusually large and remarkably well-preserved cluster of Carboniferous echinoids near Hook Head in County Wexford, Ireland. The fossil accumulation was located in the upper part of the Ballysteen Limestone Formation, which is Tournaisian in age and records sedimentation on a mixed carbonate-siliciclastic shelf/ramp. The fossil record of Paleozoic echinoids is generally poorly sampled; however, the fossil cluster from Hook Head includes at least 250 partially imbricated echinoid specimens in close association and preserves features such as the spines, Aristotle's lantern and peristomal plates. The fossil-bearing surface was precariously located on a coastal outcrop and at serious risk of being removed by storm activity, prompting an emergency rescue operation. The successful recovery of this important fossil find, which included securing official permission for extraction of the slab and its lodgement with the National Museum of Ireland, represents something of a first for Irish geological conservation.
Irish Journal of Earth Sciences, 2022
Geoconservation is a burgeoning area of activity within the Earth sciences and the preservation o... more Geoconservation is a burgeoning area of activity within the Earth sciences and the preservation of significant fossil finds remains crucial for the advancement of palaeontological knowledge and protection of geoheritage. Here, we report on the discovery of an unusually large and remarkably well-preserved cluster of Carboniferous echinoids near Hook Head in County Wexford, Ireland. The fossil accumulation was located in the upper part of the Ballysteen Limestone Formation, which is Tournaisian in age and records sedimentation on a mixed carbonate-siliciclastic shelf/ramp. The fossil record of Paleozoic echinoids is generally poorly sampled; however, the fossil cluster from Hook Head includes at least 250 partially imbricated echinoid specimens in close association and preserves features such as the spines, Aristotle's lantern and peristomal plates. The fossil-bearing surface was precariously located on a coastal outcrop and at serious risk of being removed by storm activity, prompting an emergency rescue operation. The successful recovery of this important fossil find, which included securing official permission for extraction of the slab and its lodgement with the National Museum of Ireland, represents something of a first for Irish geological conservation.
Proceedings of the Royal Society B: Biological Sciences
Deuterostomes comprise three phyla with radically different body plans. Phylogenetic bracketing o... more Deuterostomes comprise three phyla with radically different body plans. Phylogenetic bracketing of the living deuterostome clades suggests the latest common ancestor of echinoderms, hemichordates and chordates was a bilaterally symmetrical worm with pharyngeal openings, with these characters lost in echinoderms. Early fossil echinoderms with pharyngeal openings have been described, but their interpretation is highly controversial. Here, we critically evaluate the evidence for pharyngeal structures (gill bars) in the extinct stylophoran echinoderms Lagynocystis pyramidalis and Jaekelocarpus oklahomensis using virtual models based on high-resolution X-ray tomography scans of three-dimensionally preserved fossil specimens. Multivariate analyses of the size, spacing and arrangement of the internal bars in these fossils indicate they are substantially more similar to gill bars in modern enteropneust hemichordates and cephalochordates than to other internal bar-like structures in fossil b...
Proceedings of the Royal Society B, 2022
Deuterostomes comprise three phyla with radically different body plans. Phylogenetic bracketing o... more Deuterostomes comprise three phyla with radically different body plans. Phylogenetic bracketing of the living deuterostome clades suggests the latest common ancestor of echinoderms, hemichordates and chordates was a bilaterally symmetrical worm with pharyngeal openings, with these characters lost in echinoderms. Early fossil echinoderms with pharyngeal openings have been described, but their interpretation is highly controversial. Here, we critically evaluate the evidence for pharyngeal structures (gill bars) in the extinct stylophoran echinoderms Lagynocystis pyramidalis and Jaekelocarpus oklahomensis using virtual models based on high-resolution X-ray tomography scans of three-dimensionally preserved fossil specimens. Multivariate analyses of the size, spacing and arrangement of the internal bars in these fossils indicate they are substantially more similar to gill bars in modern enteropneust hemichordates and cephalochordates than to other internal bar-like structures in fossil blastozoan echinoderms. The close similarity between the internal bars of the stylophorans L. pyramidalis and J. oklahomensis and the gill bars of extant chordates and hemichordates is strong evidence for their homology. Differences between these internal bars and bar-like elements of the respiratory systems in blastozoans suggest these structures might have arisen through parallel evolution across deuterostomes, perhaps underpinned by a common developmental genetic mechanism.
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Papers by Nidia Álvarez Armada