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in category paleontology

190 results found. For more information, click each entry to expand.

121: Effectiveness of micromorphy against drilling predation: Insights from early Miocene faunal assemblage of Quilon limestone, India
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Posted 26 Nov 2019

Effectiveness of micromorphy against drilling predation: Insights from early Miocene faunal assemblage of Quilon limestone, India
581 downloads bioRxiv paleontology

Debarati Chattopadhyay, K. S. Venu gopal, Devapriya Chattopadhyay

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 families with an average drilling frequency (DF) of 0.06 and an incomplete drilling frequency (IDF) of 0.26. The characteristic drillhole morphology and occurrence of five genera of modern drilling gastropods (Naticid: Natica, Tanea and Polinices; Muricid: Triplex and Dermomurex) from the same locality reveals the predator identity. Predation in the studied assemblage is found to be highly selective in terms of prey taxa, size, mobility and site selection. Six out of nine families show evidence of predation indicating taxon selectivity. Poor correlation between DF and abundance further supports this view. Failed attacks are strongly correlated with morphological features such as surface ornamentation (Lucinidae), presence of conchiolin layers (Corbulidae). Drilling occurs primarily on medium size class and prey outside this size range show lower rate of attack. This indicates the existence of an “inverse size refugia” for extremely small prey along with the classical size refugia existing for large prey. Mobility is found to be a deterrent to drilling predation and it also increases failure.  Microbenthos of Quilon limestone shows a lower predation intensity in comparison to the Miocene macrobenthos worldwide including coeval formation of the Kutch Basin. The interaction in microbenthos is more strongly size-dependent in contrast to the Kutch fauna. Reduced predation intensity in microfauna and existence of “inverse size refugia” support the claim of micromorphy acting as a defense mechanism and highlights the role of size-dependent predation in marine benthos.

122: Glendonite occurrences in the Tremadocian of Baltica: first Early Palaeozoic evidence of massive ikaite precipitation at temperate latitude
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Posted 04 Dec 2018

Glendonite occurrences in the Tremadocian of Baltica: first Early Palaeozoic evidence of massive ikaite precipitation at temperate latitude
581 downloads bioRxiv paleontology

Leonid E Popov, J. Javier Álvaro, Lars E. Holmer, Heikki Bauert, Mansoureh Ghobadi Pour, Andrei V Dronov, Oliver Lehnert, Olle Hints, Peep Männik, Zhifei Zhang, Zhiliang Zhang

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 organic productivity. Surprisingly, the precipitation of glendonite is contemporaneous with the record of conodonts displaying low δ values, which would suggest high temperatures (>40°C) in the water column. Therefore, the early Tremadocian sediments of Baltoscandia contain both 'greenhouse' pelagic signals and near-freezing substrate indicators. This apparent paradox suggests both the influence of isotopically depleted freshwater yielded by fluvial systems, and the onset of sharp thermal stratification patterns in a semi-closed basin, which should have played an important role in moderating subpolar climates and reducing latitudinal gradients.

123: A Geophysical and Climatological Assessment of New Guinea — Implications for the Origins of Saccharum
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Posted 20 Jun 2020

A Geophysical and Climatological Assessment of New Guinea — Implications for the Origins of Saccharum
579 downloads bioRxiv paleontology

Dyfed Lloyd Evans

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. The late Pleistocene megafaunal mass extinction and the last glacial maximum (33-16 ka) are two global effects that would have significantly altered the flora on New Guinea; though the implications of these events on New Guinea have not previously been studied. Even if the genus Saccharum was established on the island during pre-historic times the consequences of Toba and other global climate change events means that it would have been eliminated from New Guinea and would have had to be re-introduced during the period of human colonization. Indeed, given the evolution of Saccharum 's immediate ancestors in Africa and Indochina it is most parsimonious to conclude that it was never native to New Guinea, but was introduced by humans relatively recently. Little work has been done on palaeotsunami evidence and ancient tsunami modelling in New Guinea. However, the recent recognition that the Aitape skull (dating to about 6 ka) may have been the victim of a tsunami show that, in the past, tsunami have penetrated significantly (about 10 km in this case) into the interior of the island to have a profound effect on biodiversity. This tsunami would have left the north coast of the island impoverished of plant life for several decades after. ### Competing Interest Statement Though the author states that no competing interests exist, for transparency DLlE declares that he is co-founder and senior scientist at CSS a non-profit organization for the furtherment of sequencing technologies.

124: Direct morpho-chemical characterization of elusive plant residues from Aurignacian Pontic Steppe ground stones
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Posted 23 Jul 2020

Direct morpho-chemical characterization of elusive plant residues from Aurignacian Pontic Steppe ground stones
561 downloads bioRxiv paleontology

G. Birarda, C. Cagnato, I. Pantyukhina, C. Stani, N. Cefarin, G. Sorrentino, E. Badetti, A. Marcomini, Carmine Lubritto, G. Khlopachev, S. Covalenco, T. Obada, N. Skakun, L. Vaccari, Laura Longo

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 morphological and chemical profiles for ASCs, that partially match the vibrational polysaccharide features of modern reference starches, highlighting diagenetic differences ranging from partial oxidation to mineralization. The results suggest the intentional processing of roots and tubers by means of mechanical tenderization and shed light on the role of dietary carbohydrates during Homo sapiens ′ (HS) colonization of Eurasia, demonstrating a long acquaintance with predictable calorific foods, crucial to maintain homeostasis during the harsh conditions of the Late MIS 3 (40-25 ky). ### Competing Interest Statement The authors have declared no competing interest.

125: Online spike sorting via deep contractive autoencoder
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Posted 24 Apr 2021

Online spike sorting via deep contractive autoencoder
551 downloads bioRxiv paleontology

Morteza Moazami Goudarzi, Mohammadreza Radmanesh, Ahmad Asgharian Rezaei, Alireza Hashemi, Mahdi Jalili

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 the clinical setting by providing the means to produce real-time perturbations of neurons via closed-loop control. Current approaches to online spike sorting are not fully automated, are computationally expensive and are often outperformed by offline approaches. In this paper, we present a novel algorithm for fast and robust online classification of single neuron activity. This algorithm is based on a deep contractive autoencoder (DCAE) architecture. DCAEs are deep neural networks that can learn a latent state representation of their inputs. The main advantage of DCAE approaches is that they are less sensitive to noise (i.e., small perturbations in their inputs). We therefore reasoned that they can form the basis for robust online spike sorting algorithms. Overall, our DCAE-based online spike sorting algorithm achieves over 90% accuracy at sorting previously-unseen spike waveforms. Moreover, our approach produces superior results compared to several state-of-the-art offline spike-sorting procedures.

126: Greenhouse conditions in lower Eocene coastal wetlands? – Lessons from Schöningen, Northern Germany
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Posted 24 Apr 2020

Greenhouse conditions in lower Eocene coastal wetlands? – Lessons from Schöningen, Northern Germany
548 downloads bioRxiv paleontology

Olaf K. Lenz, Walter Riegel, Volker Wilde

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 perturbation. This allows facies-dependent vegetational changes to be distinguished from those that were climate induced. Cluster analyses and NMDS of well-preserved palynomorph assemblages reveal four successional stages in the vegetation during peat accumulation: (1) a coastal vegetation, (2) an initial mire, (3) a transitional mire, and (4) a terminal mire. Biodiversity measures show that plant diversity decreased significantly in the successive stages. The highly diverse vegetation at the coast and in the adjacent initial mire was replaced by low diversity communities adapted to wet acidic environments and nutrient deficiency. The palynomorph assemblages are dominated by elements such as Alnus (Betulaceae) or Sphagnum (Sphagnaceae). Typical tropical elements which are characteristic for the middle Eocene part of the succession are missing. This indicates that a more warm-temperate climate prevailed in northwestern Germany during the early lower Eocene. ### Competing Interest Statement The authors have declared no competing interest.

127: Sexual dimorphism in mastoid process volumes measured from 3D models of dry crania from medieval Croatia
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Posted 05 Jan 2021

Sexual dimorphism in mastoid process volumes measured from 3D models of dry crania from medieval Croatia
543 downloads bioRxiv paleontology

Anja Petaros, Sabrina B. Sholts, Mislav Čavka, Mario Slaus, Sebastian K.T.S. Wärmländer

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 estimation purposes. A total of 170 crania (86 male, 84 females) excavated from five medieval Croatian sites were CT-scanned and used to produce 3D stereolitographic models. The three different isolation techniques were based on various anatomical landmarks and planes, as well as the anatomy of the mastoid process itself. Measurements of the three different mastoid volumes yielded different accuracies and precisions. Interestingly, anatomical structures were sometimes more useful than classical landmarks as demarcators of mastoid volume. For all three volume definitions, male mastoid volumes were significantly larger than female volumes, in both relative and absolute numbers. Sex estimation based on mastoid volume showed a slightly higher precision and better accuracy (71 % correct classifications) than visual scoring techniques (67 %) and linear distance measurements (69 %) of the mastoid process. Sex estimation based on cranial size performed even better (78 %), and multifactorial analysis (skull size + mastoid volume) reached up to 81% accuracy. These results show that measurements of the mastoid volume represent a promising metric to be used in multifactorial approaches for sex estimation of human remains.

128: Absence of general rules governing molluscan body-size response to climatic fluctuation during Cenozoic
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Posted 08 Oct 2018

Absence of general rules governing molluscan body-size response to climatic fluctuation during Cenozoic
534 downloads bioRxiv paleontology

Devapriya Chattopadhyay, Devapriya Chattopadhyay

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 be different between epifaunal and infaunal groups. To confirm the generality of these relationship among marine families, we compiled the relationship between body-size and global temperature trends over Cenozoic using a database of marine benthic molluscs of class gastropoda and bivalvia resolved to temporal stages. We evaluated the dependence of climate induced body-size response to the existing size and latitudinal spread via correlating the first-difference correlation coefficient of temperature-size (ρ1st (size-temp)) with maximum size and latitudinal spread of family respectively. Cenozoic record of this highly diverse group does not show any signature of TSR for molluscan class or for any other regional, ecological groups during the past 66My long climatic fluctuation. We did not find any evidence supporting heightened response to climatic fluctuation in groups with limited latitudinal spread or with large body- size. The tropical species did not show significant difference in their body-size response in comparison to temperate species. It also shows lack of any difference in response between ecological groups of molluscs with varying substrate relationship and hence, refutes the predicted variation due to difference in thermal specialization. Although a negative correlation between maximum latitudinal spread and ρ1st (size-temp) is observed for infaunal families, it is not statistically significant. Our results highlight the limited validity of “universal rules” in explaining the climate induced morphological response of marine communities in deep time and underscores the complexity in generalizing the biotic outcome of future climatic fluctuation.

129: Root grooves on two adjacent anterior teeth of Australopithecus africanus
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Posted 19 Nov 2017

Root grooves on two adjacent anterior teeth of Australopithecus africanus
527 downloads bioRxiv paleontology

Ian Towle, Joel D Irish, Marina Elliott, Isabelle De Groote

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 root grooves consistent with non-carious cervical lesions. Two teeth, a mandibular right permanent lateral incisor (STW 270) and canine (STW 213), belonging to the same Australopithecus africanus individual, show clear ante-mortem grooves on the labial root surface. These lesions start below the CEJ, extend over a third of the way toward the apex, and taper to a point towards the lingual side. Microscopic examination revealed no clear directional striations. The shape of these grooves is extremely similar to clinical examples of dental erosion, with the lack of striations supporting this diagnosis. These are the oldest hominin examples of non-carious cervical lesions and first described in a genus other than Homo; further, the lesions suggest that this individual regularly consumed or processed acidic food items.

130: Modelling predation and mortality rates from the fossil record of gastropods
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Posted 20 Jul 2018

Modelling predation and mortality rates from the fossil record of gastropods
519 downloads bioRxiv paleontology

Graham E Budd, Richard P. Mann

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 information about population structure. Nevertheless, by making the probably reasonable assumptions that the non-predatory death rate is both constant and low, we show that it is possible to use relatively small assemblages of gastropods to produce accurate estimates of both attack and success rates, if the overall death rate can be estimated. We show in addition what sort of information would be required to solve this problem in more general cases. However, it is unlikely that it will be possible to extract the relevant information easily from the fossil record: a variety of important collection and taphonomic biases are likely to intervene to obscure the data that gastropod assemblages may yield.

131: Extinct species identification from Upper Pleistocene bone fragments not identifiable from their osteomorphological studies by proteomics analysis
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Posted 07 Oct 2020

Extinct species identification from Upper Pleistocene bone fragments not identifiable from their osteomorphological studies by proteomics analysis
509 downloads bioRxiv paleontology

Fabrice Bray, Stéphanie Flament, Grégory Abrams, Dominique Bonjean, Kévin Di Modica, Christian Rolando, Caroline Tokarski, Patrick Auguste

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 samples. Another difficulty is the absence of genomic data for most of the extinct species. In this study, a proteomic methodology was applied to mammalian bones of 130,000 years old from the earlier Upper Pleistocene site of Scladina Cave (Belgium). Starting from 5 milligram samples, our results show a large majority of detected peptides matching collagen I alpha 1 and alpha 2 proteins with a sequence coverage up to 60%. Using sequence homology with modern sequences, a biological classification was successfully achieved and the associated taxonomic ranks to each bone were identified consistently with the information gained from osteomorphological studies and palaeoenvironmental and palaeodietary data. Among the taxa identified are the Felidae family, Bovinae subfamily, Elephantidae family and the Ursus genus. Amino acid substitutions on the collagens were identified providing new information on extinct species sequences and also helping in taxonomy-based clustering. Considering samples with no osteomorphological information, such as two bone retouchers, proteomics successfully identified the bovidae and ursidae families providing new information to the paleontologists on these objects. Combining osteomorphology studies and amino acid variations identified by proteomics, one retoucher was identified to be potentially from the Ursus spelaeus species. ### Competing Interest Statement The authors have declared no competing interest.

132: Tooth chipping patterns in Paranthropus do not support regular hard food mastication
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Posted 14 Feb 2021

Tooth chipping patterns in Paranthropus do not support regular hard food mastication
508 downloads bioRxiv paleontology

Ian Towle, Joel D Irish, Carolina Loch

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 foods in this genus. In this study, data were compiled from the literature for six hominin species (including P. boisei and P. robustus) and 17 extant primate species, to analyse Paranthropus chipping patterns in a broad comparative framework. Severity of fractures, position on the dentition, and overall prevalence were compared among species. The results indicate that both Paranthropus species had a lower prevalence of tooth fractures compared to other fossil hominin species (P. boisei: 4%; P. robustus: 11%; Homo naledi: 37%; Australopithecus africanus: 17%; Homo neanderthalensis: 45%; Epipalaeolithic Homo sapiens: 29%); instead, their frequencies are similar to apes that masticate hard items in a non-regular frequency, including chimpanzees, gibbons, and gorillas (4%, 7% and 9% respectively). The prevalence is several times lower than in extant primates known to habitually consume hard items, such as sakis, mandrills, and sooty mangabeys (ranging from 28% to 48%). Comparative chipping analysis suggests that both Paranthropus species were unlikely habitual hard object eaters, at least compared to living durophage analogues.

133: Hydraulic diversity of El Cien Formation (Baja California Sur, Mexico) and the consequences of functional diversity in paleoclimate estimation using fossil wood
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Posted 14 Sep 2019

Hydraulic diversity of El Cien Formation (Baja California Sur, Mexico) and the consequences of functional diversity in paleoclimate estimation using fossil wood
494 downloads bioRxiv paleontology

Hugo I. Martínez-Cabrera, Emilio Estrada-Ruiz

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 variation has important implications for paleoclimate estimation using fossil wood since the main tenet of the approach is environmental driven trait convergence, and assumes a central role of environmental filtering. We used functional diversity (FD) to determine how three wood anatomical traits vary in 14 extant communities (272 species) growing under different climate regimes, and inferred the prevalence of environmental filtering/limiting similarity. We also calculated FD metrics for the El Cien Formation fossil woods and discussed the results in light of the current knowledge of the flora. We found lower anatomical diversity in communities growing in dry/cool places (smaller functional spaces and lower abundance of trait combinations), suggesting that strong wood anatomical trait convergence could be the result of stronger habitat filtering in these communities. A lower strength of environmental filter in warm/wet environments, likely results in an amplification of the role of other drivers that promote higher number of hydraulic strategies through niche partition in highly structured communities. More complex ecological structures in mild tropical places likely lead to a higher spread of wood trait values. This asymmetry in the strength of environmental filter along climate gradients, suggest that the imbalances in strength of the trait-climate convergence, should be incorporated in paleoclimate prediction models. FD approach can be used to recognize promising traits with narrow niches along climate gradients, and therefore a constant effect of environmental filter.

134: New fossils of Australopithecus sediba reveal a nearly complete lower back
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Posted 29 May 2021

New fossils of Australopithecus sediba reveal a nearly complete lower back
492 downloads bioRxiv paleontology

Scott A Williams, Thomas Cody Prang, Marc R Meyer, Thierra K Nalley, Renier Van Der Merwe, Christopher Yelverton, Daniel Garcia-Martinez, Gabrielle A Russo, Kelly R Ostrofsky, Jennifer Eyre, Mark Grabowski, Shahed Nalla, Markus Bastir, Peter Schmid, Steven E Churchill, Lee R Berger

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 lower lumbar column ("pyramidal configuration"). This contrasts with recent work on lordosis in fossil hominins, where MH2 was argued to demonstrate no appreciable lordosis ("hypolordosis") similar to Neandertals. Our three-dimensional geometric morphometric (3D GM) analyses show that MH2s nearly complete middle lumbar vertebra is human-like in shape but bears large, cranially-directed transverse processes, implying powerful trunk musculature. We interpret this combination of features to indicate that A. sediba used its lower back in both human-like bipedalism and ape-like arboreal positional behaviors, as previously suggested based on multiple lines of evidence from other parts of the skeleton and reconstructed paleobiology of A. sediba.

135: Are local dominance and inter-clade dynamics causally linked when one fossil clade displaces another?
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Posted 17 Sep 2020

Are local dominance and inter-clade dynamics causally linked when one fossil clade displaces another?
485 downloads bioRxiv paleontology

Scott Lidgard, Emanuela Di Martino, Kamil Zágoršek, Lee Hsiang Liow

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 dominant clade being displaced by another. Dramatic increases in Cretaceous cheilostome genus diversification rates begin millions of years before cheilostomes overtake cyclostomes in local species proportions. Moreover, analyses of origination and extinction rates over 150 Myr suggest that inter-clade dynamics are causally linked to each other, but not to changing assemblage-level proportions. One Sentence Summary Global fossil diversification rates and local taxonomic dominance are not causally linked. ### Competing Interest Statement The authors have declared no competing interest.

136: The ecomorphology of southern African rodent incisors: Potential applications to the hominin fossil record
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Posted 27 Sep 2018

The ecomorphology of southern African rodent incisors: Potential applications to the hominin fossil record
480 downloads bioRxiv paleontology

Oliver C.C. Paine, Jennifer N. Leichliter, Nico Avenant, Daryl Codron, Austin Lawrence, Matt Sponheimer

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 analysis, often referred to as a “taxon-free” method, can potentially circumvent this problem by focusing on the adaptive, rather than the taxonomic significance of rodent incisor morphology. Here, we determine if the morphology of the upper incisors of modern southern African rodents reflects dietary behavior using discriminant function analysis. Our model suggests that a strong ecomorphological signal exists in our modern sample and we apply these results to two samples of isolated incisors from the hominin fossil bearing sites, Sterkfontein and Swartkrans.

137: OCCURRENCE OF THE BRACHIOPOD TICHOSINA IN DEEP-SEA CORAL BOTTOMS OF THE CARIBBEAN SEA AND ITS PALEOENVIRONMENTAL IMPLICATIONS
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Posted 24 Jun 2020

OCCURRENCE OF THE BRACHIOPOD TICHOSINA IN DEEP-SEA CORAL BOTTOMS OF THE CARIBBEAN SEA AND ITS PALEOENVIRONMENTAL IMPLICATIONS
476 downloads bioRxiv paleontology

Alexis Rojas, Adriana Gracia, Ivan Hernández-Ávila, Pedro Patarroyo, Michał Kowalewski

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, we reviewed literature sources on Cenozoic sediments in the Dominican Republic and found tentative evidence that such ecological ties could have existed since at least the Pliocene. These observations are reminiscent of the Gryphus -anthozoan association observed in the modern Mediterranean continental margin. Understanding to what extent the brachiopod Tichosina is linked to deep-water habitats has implications for the recognition of deep-water macrobenthic communities in the Cenozoic rock record of the Caribbean ### Competing Interest Statement The authors have declared no competing interest.

138: Deciphering trophic interactions in a mid-Cambrian assemblage
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Posted 28 May 2020

Deciphering trophic interactions in a mid-Cambrian assemblage
475 downloads bioRxiv paleontology

Anshuman Swain, Matthew Devereux, William F. Fagan

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-resolution fossil dataset from the Raymond Quarry (RQ) member of the mid-Cambrian Burgess Shale (7549 specimens, 61 taxa, ~510 Mya) affording new perspectives on these challenging issues. Further, we formulate a new measure of 'preservation bias' that aids identification of those assemblage subsets to which network analyses can be reliably applied. For sections with sufficiently low bias, abundance correlation network analyses predicted longitudinally consistent trophic and competitive interactions. Our correlation network analyses predicted previously postulated trophic interactions with 83.5% accuracy and demonstrated a shift from specialist interaction-dominated assemblages to ones dominated by generalist and competitive interactions. This approach provides a robust, taphonomically corrected framework to explore and predict in detail the existence and ecological character of putative interactions in fossil datasets, offering new windows on ancient food-webs. ### Competing Interest Statement The authors have declared no competing interest.

139: Dietary and body mass reconstruction of the Miocene neotropical bat Notonycteris magdalenensis (Phyllostomidae) from La Venta, Colombia
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Posted 10 Dec 2020

Dietary and body mass reconstruction of the Miocene neotropical bat Notonycteris magdalenensis (Phyllostomidae) from La Venta, Colombia
473 downloads bioRxiv paleontology

Camilo Lopez-Aguirre, Nicholas J Czaplewski, Andres Link, Masanaru Takai, Suzanne Hand

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 Neotropical bats, but aspects of its biology remain unclear. In this study, we used a multivariate dental topography analysis (DTA) to reconstruct the likely diet of N. magdalenensis by quantitatively comparing measures of molar complexity with that of 25 modern phyllostomid and noctilionid species representing all major dietary habits in bats. We found clear differences in molar complexity between dietary guilds, indicating that DTA is potentially an informative tool to study bat ecomorphology. Our results suggest N. magdalenensis was probably an omnivore or insectivore, rather than a carnivore like its modern relatives Chrotopterus auritus and Vampryum spectrum. Also, we reconstructed the body mass of N. magdalenensis to be ~50 g, which is larger than most insectivorous bats, but smaller than most carnivorous bats. Our results confirm that Notonycteris magdalenensis was probably not a specialised carnivore. It remains to be demonstrated that the specialised carnivory ecological niche was occupied by the same lineage of phyllostomines from at least the middle Miocene. Combining our diet and body mass reconstructions, we suggest that N. magdalenensis exhibits morphological pre-adaptations crucial for the evolution of specialised carnivory.

140: The balancing act of Nipponites mirabilis (Nostoceratidae, Ammonoidea): managing hydrostatics during a complex ontogenetic trajectory
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Posted 11 Jun 2020

The balancing act of Nipponites mirabilis (Nostoceratidae, Ammonoidea): managing hydrostatics during a complex ontogenetic trajectory
462 downloads bioRxiv paleontology

David J. Peterman, Tomoyuki Mikami, Shinya Inoue

Nipponites is a heteromorph ammonoid with a complex and unique morphology that obscures its mode of life and ethology. The seemingly aberrant shell of this Late Cretaceous nostoceratid seems deleterious. However, hydrostatic simulations suggest that this morphology confers several advantages for exploiting a quasi-planktic mode of life. Virtual, 3D models of Nipponites mirabilis were used to compute various hydrostatic properties through 14 ontogenetic stages. At each stage, Nipponites had the capacity for neutral buoyancy and was not restricted to the seafloor. Throughout ontogeny, horizontally facing to upwardly facing soft body orientations were preferred. These orientations were aided by the obliquity of the shell’s ribs, which were parallel to former positions of the aperture during life. Static orientations were somewhat fixed, inferred by stability values that are slightly higher than extant Nautilus. The initial open-whorled, planispiral phase is well suited to horizontal backwards movement with little rocking. Nipponites then deviates from this coiling pattern with a series of alternating U-shaped bends in the shell. This modification allows for proficient rotation about the vertical axis, while possibly maintaining the option for horizontal backwards movement by redirecting its hyponome. These particular hydrostatic properties likely result in a tradeoff between hydrodynamic streamlining, suggesting that Nipponites assumed a low energy lifestyle of slowly pirouetting in search for planktic prey. Each computed hydrostatic property influences the others in some way, suggesting that Nipponites maintained a delicate hydrostatic balancing act throughout its ontogeny in order to facilitate this mode of life.

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