David A . T . Harper (original) (raw)

Papers by David A . T . Harper

Estonian Journal of Earth Sciences

Despite its small areal extent, the island of Ireland exposes eight Caledonian tectonic terranes;... more Despite its small areal extent, the island of Ireland exposes eight Caledonian tectonic terranes; six of them contain Ordovician brachiopod assemblages. These terranes record the early phases and destruction of the Iapetus Ocean through the occurrence of latitude-sensitive brachiopod faunas during the Middle Ordovician and early Late Ordovician; more cosmopolitan faunas characterized the later Ordovician.

Journal of Systematic Palaeontology, 2019

Like most of the benthos, brachiopods suffered huge losses in biodiversity during the end-Permian... more Like most of the benthos, brachiopods suffered huge losses in biodiversity during the end-Permian extinction and did not fully recover until the Anisian (Middle Triassic). Anisian brachiopod faunas are thus a key clade characterizing the recovered marine ecosystems in the early Mesozoic. Of these, the brachiopod fauna from Qingyan Town in Guizhou Province, southwestern China has long been one of the best-known Anisian faunas in the world. The taxonomy of the Qingyan fauna, however, was last studied half century ago, and thus requires revision. Here we describe 34 species (and subspecies) (including seven undetermined species) assigned to 29 brachiopod genera from the Qingyan Formation from the Leidapo and Wachangpo localities in the Qingyan section. Of these, 11 species are described for the first time from this area.

Proceedings of the Geologists' Association, 2017

A collection of unremarkably preserved fossil irregular echinoids from the Upper Oligocene (Chatt... more A collection of unremarkably preserved fossil irregular echinoids from the Upper Oligocene (Chattian) Antigua Formation of Antigua, Lesser Antilles, nonetheless provides evidence of a range of palaeoecological interactions. A dead test of the heart urchin Eupatagus sp. formed a hard substrate for the attachment of gregarious Thecidellina? sp., a thecidoid brachiopod. Although obligate encrusters, these brachiopods more commonly occur as disarticulated valves free of the substrate in the Antillean fossil record. Elongate pits in test fragments were formed, variously, before and after the death of the host echinoids. These depressions on the external surface were formed either by invertebrates excavating domiciles or by claws or teeth; the echinoid later reclaimed the pits and grew new tubercles in the base. Post-mortem pits lack such new tuberculation. A test of Eupatagus sp. bears the boring Oichnus isp., formed either by a predator (gastropod?) or after the death of the echinoid (domicile), and a serpulid worm tube which grew on the test subsequent to the echinoid's death. The echinoid fauna of the Antigua Formation has been easy to collect and specimens are to be found in many museums; they now await re-examination to reveal palaeosynecological data analogous to that determined from the fragments discussed herein.

Royal Society Open Science, 2016

The Sirius Passet Lagerstätte of North Greenland contains the first exceptionally preserved mat-g... more The Sirius Passet Lagerstätte of North Greenland contains the first exceptionally preserved mat-ground community of the Cambrian, dominated, in terms of abundance, by trilobites but particularly characterized by iconic arthropods and lobopods, some also occurring in the Burgess shale. High-resolution photography, scanning electron imaging and elemental mapping have been carried out on a variety of specimens of the non-mineralized arthropod Campanamuta mantonae (Budd 2011 J. Syst. Palaeontol. 9 , 217–260 ( doi:10.1080/14772019.2010.492644 )) which has three-dimensional gut and muscle preservation. Results show that the guts contain a high concentration of calcium phosphate (approximating to the mineral francolite), whereas the adjacent muscles are silicified. This indicates a unique, tissue-specific taphonomy for this Cambrian taxon. We hypothesize that the precipitation of calcium phosphate in the guts occurs rapidly after death by ‘crystal seed’ processes in suboxic, slightly acidi...

New finds of trilobites and brachiopods are described from two horizons in the autochthonous/para... more New finds of trilobites and brachiopods are described from two horizons in the autochthonous/parautoch thonous Hardangervidda Group. The occurrence of the trilobites Lejopyge armata (Linnarsson) and Andrarina costata (Angelin) indicates, for the first time, a late mid-Cambrian (Lejopyge /aevigata Zone) age for part of the 'Alum Shale' (Bjørno Member of the Låven Formation) on Hardangervidda. Brachiopods from the younger Bjørnaskalle Formation include orthides, a clitambonitide and Antigon ambonites of the p/anus species group of Opik and are indicative of a late Arenig-early Llanvirn age. Both faunas indicate the most westerly known extension of Cambrian and Ordovician rocks on the Baltic platform. But whilst the uniformity of the 'Alum Shale' facies across the platform is confirmed, the upper Arenig-lower Llanvirn rocks differ from coeval strata elsewhere in the autochthon.

Ichnos, 2016

Limestones of the Upper Oligocene Antigua Formation of Antigua unusual burrows filled with the de... more Limestones of the Upper Oligocene Antigua Formation of Antigua unusual burrows filled with the densely packed debris of shelly benthos. Unlined burrows (Planolites?) in deep-water biofacies at Half Moon Bay, parish of Saint Philip, are packed with a monospecific assemblage of large benthic foraminiferans (Lepidocyclina canelli Lemoine & Douvillé) and a single brachiopod valve, Tichosina sp. A similar burrow in shallower-water biofacies at Hughes Point, parish of Saint Philip, is packed with echinoderm debris and, particularly, test fragments of the spatangoid echinoid Lovenia n. sp. Fragments of the same echinoid fill a conical burrow, Bergaueria isp. The latter is probably a physical accumulation, the common fragments of echinoid being washed into an empty burrow. In contrast, the infill of Planolites? isp. is more likely to be an accumulation mediated by the burrower.

Nature communications, Mar 9, 2018

Recent discoveries of fossil nervous tissue in Cambrian fossils have allowed researchers to trace... more Recent discoveries of fossil nervous tissue in Cambrian fossils have allowed researchers to trace the origin and evolution of the complex arthropod head and brain based on stem groups close to the origin of the clade, rather than on extant, highly derived members. Here we show that Kerygmachela from Sirius Passet, North Greenland, a primitive stem-group euarthropod, exhibits a diminutive (protocerebral) brain that innervates both the eyes and frontal appendages. It has been surmised, based on developmental evidence, that the ancestor of vertebrates and arthropods had a tripartite brain, which is refuted by the fossil evidence presented here. Furthermore, based on the discovery of eyes in Kerygmachela, we suggest that the complex compound eyes in arthropods evolved from simple ocelli, present in onychophorans and tardigrades, rather than through the incorporation of a set of modified limbs.

Journal of paleontology, Feb 27, 2024

Non-technical Summary.-A major glaciation can have fundamental effects on the diversity and globa... more Non-technical Summary.-A major glaciation can have fundamental effects on the diversity and global distribution of marine invertebrate organisms. This study documents brachiopods from a shelly benthic marine fauna in northwestern Canada during the first major glaciation of the Phanerozoic Era, in the latest Ordovician Period. The study area in the Mackenzie Mountains was located in the northern-hemisphere tropics during the Late Ordovician. The presence of a unique glaciation-age brachiopod fauna in both the southern-hemisphere tropics of ancient North America (in today's southeastern USA) and the Mackenzie Mountains indicates the far reach of the latest Ordovician glaciation centered in the southern Polar region.

International audienceThe early Palaeozoic radiation has generally been documented through the pr... more International audienceThe early Palaeozoic radiation has generally been documented through the promotion of discernible 'global' events. The Cambrian 'Explosion,' placed by most authors in an interval around-540 and-520 million years ago (Ma), is considered to be an abrupt appearance in the fossil record of most animal phyla, with a sudden, or almost sudden increase in complex morphologies across the metazoan groups. In a few recent papers, the Great Ordovician Biodiversification 'Event' (GOBE) has similarly been restricted to a single dramatic biodiversification 'event' in the Darriwilian Stage of the Middle Ordovician Series, between 470 and 455 Ma, although historically the biodiversification is considered as an aggregation of radiation 'events' capturing a large and complex increase of taxonomic diversity of marine invertebrates covering the entire Ordovician. In analogy with studies of other, more recent geological intervals, it becomes m...

Palaeogeography, Palaeoclimatology, Palaeoecology, 2019

Recent molecular clock data suggest with highest probability a Cambrian origin of Embryophyta (al... more Recent molecular clock data suggest with highest probability a Cambrian origin of Embryophyta (also called land plants), indicating that their terrestrialization most probably started about 500 million years ago. The fossil record of the 'Cambrian explosion' was limited to marine organisms and not visible in the plant fossil record. The most significant changes in early land plant evolution occurred during the Ordovician. For instance, the earliest bryophytelike cryptospores and the oldest fragments of the earliest land plants come from the Middle and Late Ordovician, respectively. Organic geochemistry studies on biomarker compositions hint at a transition from green algae to land plants during the 'Great Ordovician Biodiversification Event' (GOBE). The colonization of the terrestrial realms by land plants clearly had an impact on marine ecosystems. Interactions between the terrestrial and marine biospheres have been proposed and the radiation of land plants potentially impacted on CO2 and O2 concentrations and on global climate. In addition, the shift of strontium isotopes during the Ordovician is probably linked to changing terrestrial landscapes, affected by the first massive land invasion of eukaryotic terrestrial life. The land plants seem unaffected by the first global mass extinction at the end of the Ordovician that eliminated many marine invertebrate taxa.

Palaeoworld, 2019

A new, high-diversity, latest Ordovician brachiopod fauna of nearly 800 brachiopod specimens was ... more A new, high-diversity, latest Ordovician brachiopod fauna of nearly 800 brachiopod specimens was collected from the Wanyaoshu Formation (Hirnantian) in the Shaodihe section, Mangshi City, western Yunnan, Southwest China. Altogether 22 genera and two undetermined taxa were identified; dominant are Aegiromena, Anisopleurella,

Geological Curator, Oct 1, 1996

This document is a copy of the following article published by the Geological Curators' Group. It ... more This document is a copy of the following article published by the Geological Curators' Group. It is provided for non-commercial research and educational use. Copyright of this article remains with the author(s). Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited unless agreed in advance. This cover page must be included as an integral part of any copies of this document. Geological collections are an irreplaceable part of our scientific and cultural heritage. The Geological Curators' Group is dedicated to their better care, maintenance and use.

Episodes, 2013

IUGS) uses the units and formally defined boundaries as international standards: they are include... more IUGS) uses the units and formally defined boundaries as international standards: they are included in the library of GeoSciML, an application for globally accessing standards-based geoscience data and information. Furthermore, the GSSPs (Global Boundary Stratotype Section and Point) that define the boundaries are recognized as international geostandards, at which ICS encourages the placement of markers, educational exhibits, and even 'golden spikes' in wellattended dedication ceremonies (Schmitz et al., 2011: their Fig. 4; Morton, 2012). Here we present the most recently updated version of the ICS Chart dated January 2013 (Fig. 1). From earlier editions, we have continued the organisation of the chart in four columns. Three columns present the Phanerozoic, showing four systems in each column. At the lowest level they display 34 + 34 + 32 stages. The stage names are derived from stratotype areas, and the stages are defined primarily on marine faces. The fourth column shows the Precambrian, subdivided to system level. An innovation to the layout is that the stages of greater temporal duration are shown with thicker intervals in the columns. The numerical ages make clear that the chronostratigraphic units are not of equal temporal duration and that the geological time scale is not a linear one. The three Phanerozoic columns span 145, 214 and 182 Ma respectively, but have equal heights in the chart. Within these columns, each stage is given a fixed proportion of the column height (e.g., 2%). The remaining height (100-(34 x 2) = 32% in the example) is then distributed proportionally to the stages that cover more than the fixed proportion on a linear timescale for that column. With the design we have tried to communicate visually, in improved style, that the division of Phanerozoic geological time is irregular and governed by the stratigraphical successions on which the units were originally defined, to which many subsequent revisions have been made. The chart design is intended to be advantageous in the daily use for both professional geologists and other users alike. Global divisions and 'Golden Spikes' Units of all ranks are in the process of being defined by GSSPs for their lower boundaries, including those of the Archean and Proterozoic, the latter long defined by Global Standard Stratigraphic Ages (GSSA). The status of each GSSP is displayed in the chart by small golden-spike icons at the base of the divisions that they define. The status of each GSSA is indicated similarly with clock icons. For boundaries in the Phanerozoic for which no GSSP is currently ratified, or which lack constraining numerical ages, an approximate numerical age (~) is provided. Note that numerical ages do not define units in the Phanerozoic and the Ediacaran, they are only defined by GSSPs. The International Commission on Stratigraphy (ICS) has a long tradition of producing international charts that communicate higher-order divisions of geological time and actual knowledge on the absolute numerical ages of their boundaries. The primary objective of ICS is to define precisely a global standard set of timecorrelative units (Systems, Series, and Stages) for stratigraphic successions worldwide. These units are, in turn, the basis for the Periods, Epochs and Ages of the Geological Time Scale. Setting an international global standard is fundamental for expressing geological knowledge. It is also of considerable pragmatic importance as it provides the framework through which regional-scale higher-resolution divisions can be linked, equated and collated. This is a status update on the International Chronostratigraphic Chart and the ICS website www.stratigraphy.org.

Irish Journal of Earth Sciences, 2017

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