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Results 121 through 140 out of 197

in category paleontology

 

121: Defining variation in pre-human ecosystems can guide conservation: An example from a Caribbean coral reef

Aaron O'Dea, Mauro Lepore et al.

585 downloads (posted 29 Aug 2019)

There is a consensus that Caribbean coral reefs are a pale shadow of what they once were, yet a reef's pre-human state is typically assumed or estimated using space-for-time substitution approaches. These approaches may fail to account for past variation before human impact which could mislead conservation priorities and actions. In this study we use a suite of fossilised mid-Holocene (7.2-5.6 ka) fringing reefs in Caribbean Panama to define the Historical Range of Variation (HRV) in coral community structure before human-impact to provide context for the states of modern reefs in the same area. Using the abundances of coral taxa to quantify communities, we found that most of the modern coral communities exist in novel ecosystem states with no fossil precedence. We do however identify one modern reef that is indistinguishable in coral community structure from the mid-Holocene reefs. Reef-matrix cores show that the community on this reef has remained in a stable state for over 760 years, suggesting long-term resistance to the region-wide shift to novel states. Without historical context this robust and stable reef would be overlooked since it does not fulfil expectations of what a pristine coral reef should look like. This example illustrates how defining past variation using the fossil record can place modern degradation in historical context and improve conservation recommendations.

https://rxivist.org/papers/59329
https://doi.org/10.1101/749382

122: Effectiveness of micromorphy against drilling predation: Insights from early Miocene faunal assemblage of Quilon limestone, India

Debarati Chattopadhyay, K. S. Venu gopal et al.

584 downloads (posted 26 Nov 2019)

The nature of drilling predation, although well documented for molluscan fossils, is understudied for micromolluscs (<5mm). Studying predation in micromolluscs is especially critical in evaluating the adaptive significance of micromorphy against predation and assessing the importance of predator-prey size relationship (PPSR). This study documents drilling predation event in microbivalves from early Miocene (Burdigalian) fossil assemblage of Quilon limestone from Kerala, India. Our sample of ~2000 valves represent nine f...

https://rxivist.org/papers/67338
https://doi.org/10.1101/856260

123: Glendonite occurrences in the Tremadocian of Baltica: first Early Palaeozoic evidence of massive ikaite precipitation at temperate latitude

Leonid E Popov, J. Javier Álvaro et al.

583 downloads (posted 04 Dec 2018)

The Tremadocian (Early Ordovician) is currently considered a time span of greenhouse conditions with tropical water surface temperature estimates, interpolated from oxygen isotopes, approaching 40°C. In the high-latitude Baltoscandian Basin, these data are in contrast with the discovery of glendonite, a pseudomorph of ikaite (CaCO3·6H2O) and valuable indicator of near-freezing bottom-water conditions. The massive precipitation of this climatically sensitive mineral is associated with transgressive conditions and high or...

https://rxivist.org/papers/38105
https://doi.org/10.1101/486779

124: A Geophysical and Climatological Assessment of New Guinea — Implications for the Origins of Saccharum

Dyfed Lloyd Evans

583 downloads (posted 20 Jun 2020)

Any assessment of whether or not Saccharum species are native or introduced in New Guinea require an evolutionary (in a geological sense), geophysical and climatological assessment of the island. Like many of the land masses circling the Pacific (in the volcanically active region known as the 'ring of fire') New Guinea is geologically young, with the island in its modern form not pre-dating 2Ma. Novel modelling of the 74ka youngest Toba supereruption indicates a potential extinction level tsunami and loss of habitat. Th...

https://rxivist.org/papers/88207
https://doi.org/10.1101/2020.06.20.162842

125: Online spike sorting via deep contractive autoencoder

Morteza Moazami Goudarzi, Mohammadreza Radmanesh et al.

578 downloads (posted 24 Apr 2021)

Spike sorting-the process of separating spikes from different neurons-is often the first and most critical step in the neural data analysis pipeline. Spike-sorting techniques isolate a single neuron's activity from background electrical noise based on the shapes of the waveforms (WFs) obtained from extracellular recordings. Despite several advancements in this area, an important remaining challenge in neuroscience is online spike sorting, which has the potential to significantly advance basic neuroscience research and t...

https://rxivist.org/papers/139426
https://doi.org/10.1101/2021.04.23.441225

126: New fossils of Australopithecus sediba reveal a nearly complete lower back

Scott A Williams, Thomas Cody Prang et al.

573 downloads (posted 29 May 2021)

Adaptations of the lower back to bipedalism are frequently discussed but infrequently demonstrated in early fossil hominins. Newly discovered lumbar vertebrae contribute to a near-complete lower back of Malapa Hominin 2 (MH2), offering additional insights into posture and locomotion in Australopithecus sediba. We show that MH2 demonstrates a lower back consistent with human-like lumbar lordosis and other adaptations to bipedalism, including an increase in the width of intervertebral articular facets from the upper to lo...

https://rxivist.org/papers/143848
https://doi.org/10.1101/2021.05.27.445933

127: Direct morpho-chemical characterization of elusive plant residues from Aurignacian Pontic Steppe ground stones

G. Birarda, C. Cagnato et al.

571 downloads (posted 23 Jul 2020)

Direct evidence for the intentional processing of starch-rich plants during the Paleolithic is scant, and that evidence is often compromised by concerns over preservation and contamination. Our integrated, multimodal approach couples wear-trace analysis with chemical imaging methods to identify the presence of genuine ancient starch candidates (ASC) on ground stones used in the Pontic Steppe starting around 40,000 years ago. Optical and electron microscopy coupled with infrared spectromicroscopy and imaging provide morp...

https://rxivist.org/papers/92028
https://doi.org/10.1101/2020.07.23.212324

128: Greenhouse conditions in lower Eocene coastal wetlands? – Lessons from Schöningen, Northern Germany

Olaf K. Lenz, Walter Riegel et al.

556 downloads (posted 24 Apr 2020)

The Paleogene succession of the Helmstedt Lignite Mining District in Northern Germany includes coastal peat mire records from the latest Paleocene to the middle Eocene at the southern edge of the Proto-North Sea. Therefore, it covers the different long- and short-term climate perturbations of the Paleogene greenhouse. 56 samples from three individual sections of a lower Eocene seam in the record capture the typical succession of the vegetation in a coastal wetland during a period that was not affected by climate perturb...

https://rxivist.org/papers/81039
https://doi.org/10.1101/2020.04.24.059345

129: Sexual dimorphism in mastoid process volumes measured from 3D models of dry crania from medieval Croatia

Anja Petaros, Sabrina B. Sholts et al.

545 downloads (posted 05 Jan 2021)

3D analysis of skeletal volumes has become an important field in digital anthropology studies. The volume of the mastoid process has been proposed to display significant sexual dimorphism, but it has a complex shape and to date no study has quantified the full mastoid volume for sex estimation purposes. In this study we compared three different ways to isolate the volume of the mastoid process from digital 3D models of dry crania, and then evaluated the performance of the three different volume definitions for sex estim...

https://rxivist.org/papers/123626
https://doi.org/10.1101/2021.01.04.425320

130: Absence of general rules governing molluscan body-size response to climatic fluctuation during Cenozoic

Devapriya Chattopadhyay, Devapriya Chattopadhyay

537 downloads (posted 08 Oct 2018)

Body size is a key factor in dictating the fate of interaction between an organism and its surrounding environment. A negative temperature-size relationship (TSR) has been suggested as one of the universal responses to climatic warming. It is also predicted that groups with narrow latitudinal range, tropical affinity and higher body size, would show higher sensitivity to climatic fluctuation. Moreover, because of the difference in thermal sensitivity, it is also expected that the response to climatic fluctuation would b...

https://rxivist.org/papers/34278
https://doi.org/10.1101/438002

131: Root grooves on two adjacent anterior teeth of Australopithecus africanus

Ian Towle, Joel D Irish et al.

531 downloads (posted 19 Nov 2017)

Tooth root grooves and other ante-mortem dental tissue loss not associated with caries found on or near the cementoenamel junction (CEJ) are commonly termed non-carious cervical lesions. Three main processes are implicated in forming these lesions: abrasion, dental erosion, and abfraction. As yet, these lesions have not been described in non-Homo hominins. In this study South African fossil hominin collections were examined for evidence of any type of non-carious cervical lesion. Only one individual shows ante-mortem ro...

https://rxivist.org/papers/30120
https://doi.org/10.1101/222059

132: Tooth chipping patterns in Paranthropus do not support regular hard food mastication

Ian Towle, Joel D Irish et al.

524 downloads (posted 14 Feb 2021)

The paranthropines, including Paranthropus boisei and Paranthropus robustus, have often been considered hard-food specialists. The large post-canine teeth, thick enamel, and robust craniofacial features are often suggested to have evolved to cope with habitual mastication of hard foods. Yet, direct evidence for Paranthropus feeding behaviour often challenges these morphological interpretations. The main exception being antemortem tooth chipping which is still regularly used as evidence of habitual mastication of hard fo...

https://rxivist.org/papers/129243
https://doi.org/10.1101/2021.02.12.431024

133: Extinct species identification from Upper Pleistocene bone fragments not identifiable from their osteomorphological studies by proteomics analysis

Fabrice Bray, Stéphanie Flament et al.

522 downloads (posted 07 Oct 2020)

The ancient preserved molecules offer the opportunity to gain a better knowledge on the biological past. In recent years, bones proteomics has become an attractive method to study the animal biological origin, extinct species and species evolution as an alternative to DNA analysis which is limited by DNA amplification present in ancient samples and its contamination. However, the development of a proteomic workflow remains a challenge. The analysis of fossils must consume a low quantity of material to avoid damaging the...

https://rxivist.org/papers/97044
https://doi.org/10.1101/2020.10.06.328021

134: Modelling predation and mortality rates from the fossil record of gastropods

Graham E Budd, Richard P. Mann

520 downloads (posted 20 Jul 2018)

Gastropods often show signs of unsuccessful attacks by predators in the form of healed scars in their shells. As such, fossil gastropods can be taken as providing a record of predation through geological time. However, interpreting the number of such scars has proved to be problematic - would a low number of scars mean a low rate of attack, or a high rate of success, for example? Here we develop a model of scar formation, and formally show that in general these two variables cannot be disambiguated without further infor...

https://rxivist.org/papers/17330
https://doi.org/10.1101/373399

135: Hydraulic diversity of El Cien Formation (Baja California Sur, Mexico) and the consequences of functional diversity in paleoclimate estimation using fossil wood

Hugo I. Martínez-Cabrera, Emilio Estrada-Ruiz

496 downloads (posted 14 Sep 2019)

Community assembly processes, environmental filtering and limiting similarity, determine functional traits values within communities. Because environment influences the number of viable functional strategies species might take, a strong effect of environmental filter often results in communities having species with similar trait values and narrow functional niches. On the other hand, limiting similarity lead to communities with broader functional spaces. The degree to community assembly processes influence wood trait va...

https://rxivist.org/papers/60812
https://doi.org/10.1101/768283

136: Are local dominance and inter-clade dynamics causally linked when one fossil clade displaces another?

Scott Lidgard, Emanuela Di Martino et al.

487 downloads (posted 17 Sep 2020)

Disputing the supposition that ecological competition drives macroevolutionary patterns is now a familiar goal in many fossil biodiversity studies. But it is an elusive goal, hampered by patchy sampling, few assemblage-level comparative analyses, unverified ecological equivalence of clades and a dearth of appropriate statistical tools. We address these concerns with a fortified and vetted compilation of 40190 fossil species occurrences of cyclostome and cheilostome bryozoans, a canonical example of one taxonomically dom...

https://rxivist.org/papers/99074
https://doi.org/10.1101/2020.09.16.299750

137: The ecomorphology of southern African rodent incisors: Potential applications to the hominin fossil record

Oliver C.C. Paine, Jennifer N. Leichliter et al.

482 downloads (posted 27 Sep 2018)

The taxonomic identification of mammalian fauna within fossil assemblages is a well-established component of paleoenvironmental reconstructions. However, many fragmentary specimens recovered from fossil sites are often disregarded as they can be difficult to identify with the precision required for taxonomic methods. For this reason, the large numbers of isolated rodent incisors that are often recovered from hominin fossil bearing sites have generally been seen as offering little interpretive value. Ecomorphological ana...

https://rxivist.org/papers/33772
https://doi.org/10.1101/429365

138: OCCURRENCE OF THE BRACHIOPOD TICHOSINA IN DEEP-SEA CORAL BOTTOMS OF THE CARIBBEAN SEA AND ITS PALEOENVIRONMENTAL IMPLICATIONS

Alexis Rojas, Adriana Gracia et al.

481 downloads (posted 24 Jun 2020)

Despite its importance as the larger component of the modern and Cenozoic brachiopod faunas in the Caribbean region, the ecology and habitat preferences of the terebratulid Tichosina remain poorly understood. We compiled field observations from multiple sites in the Caribbean of Colombia (i.e., San Bernado Bank, Bahia Honda-Guajira, Puerto Escondido, Joint Regime Area Jamaica-Colombia) and data from the R/V Pillsbury program, indicating that Tichosina may have close ecological ties with deep-water corals. In addition, w...

https://rxivist.org/papers/88650
https://doi.org/10.1101/2020.06.24.168658

139: Deciphering trophic interactions in a mid-Cambrian assemblage

Anshuman Swain, Matthew Devereux et al.

479 downloads (posted 28 May 2020)

The Cambrian Period (541-485 Mya) represents a major stage in the development of metazoan-dominated assemblages with complex community structure and species interactions. Exceptionally preserved fossil sites have allowed specimen-based identification of putative trophic interactions to which network analyses have been applied. However, network analyses of the fossil record suffer from incomplete and indirect data, time averaging that obscures species coexistence, and biases in preservation. Here, we present a novel high...

https://rxivist.org/papers/85179
https://doi.org/10.1101/2020.05.26.116848

140: Dietary and body mass reconstruction of the Miocene neotropical bat Notonycteris magdalenensis (Phyllostomidae) from La Venta, Colombia

Camilo Lopez-Aguirre, Nicholas J Czaplewski et al.

478 downloads (posted 10 Dec 2020)

The middle Miocene La Venta bat fauna is the most diverse bat palaeocommunity in South America, with at least 14 species recorded. They include the oldest plant-visiting bat in the New World, and some of the earliest representatives of the extant families Phyllostomidae, Thyropteridae and Noctilionidae. Notonycteris magdalenensis from La Venta is an extinct member of the subfamily Phyllostominae, a group of modern Neotropical animalivorous and omnivorous bats, and is commonly included in studies of the evolution of Neot...

https://rxivist.org/papers/121008
https://doi.org/10.1101/2020.12.09.418491