scholarly journals Description and ontogeny of a 40-million-year-old parasitic isopodan crustacean: Parvucymoides dvorakorum gen. et sp. nov.

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e12317
Author(s):  
Serita Van der Wal ◽  
Mario Schädel ◽  
Boris Ekrt ◽  
Joachim T. Haug
Keyword(s):  
Developmental Stages ◽  
Morphological Characteristics ◽  
Single Species ◽  
Late Eocene ◽  
Fossil Specimen ◽  
Ontogenetic Stages ◽  
Extant Species ◽  
Polarised Light ◽  
Body Shapes ◽  
Insight Into

A collection of exceptionally well-preserved fossil specimens of crustaceans, clearly representatives of Isopoda, is presented here. Excavated from the late Eocene (approximately 40 million years ago) freshwater sediments of the Trupelník hill field site near Kučlín, Czech Republic, these specimens are preserved with many details of the appendages. The morphological characteristics of the fossils were documented using macro-photography with polarised light, as well as stereo imaging. These characteristics, especially including the trunk appendage morphology, were compared to those of related extant groups from different ontogenetic stages. All specimens are conspecific, representing a single species Parvucymoides dvorakorum gen. et sp. nov. Morphometric analysis of body shapes and sizes of the reconstructed fossils and related extant species were performed. These analyses provided insight into the ontogenetic stages of each reconstructed fossil specimen. In combination with the morphological assessment, the results indicate that the fossils represent at least two (possibly three) developmental stages, including immatures. The morphology of the appendages suggests that these fossils were parasites. The fossils are interpreted as either representatives of Cymothoidae or at least closely related to this group.

scholarly journals Ontogenetic variability in crystallography and mosaicity of conodont apatite: implications for microstructure, palaeothermometry and geochemistry

2020 ◽  
Vol 7 (7) ◽  
pp. 200322
Author(s):  
Mohammad Shohel ◽  
Neo E. B. McAdams ◽  
Bradley D. Cramer ◽  
Tori Z. Forbes
Keyword(s):  
Developmental Stages ◽  
Single Species ◽  
Relative Increase ◽  
X Ray Diffraction ◽  
Systematic Testing ◽  
Cell Dimensions ◽  
Crown Tissue ◽  
Element Type ◽  
Unit Cell Dimensions ◽  
Insight Into

X-ray diffraction data from Silurian conodonts belonging to various developmental stages of the species Dapsilodus obliquicostatus demonstrate changes in crystallography and degree of nanocrystallite ordering (mosaicity) in both lamellar crown tissue and white matter. The exclusive use of a single species in this study, combined with systematic testing of each element type at multiple locations, provided insight into microstructural and crystallographic differentiation between element type ( S a , S b - c , M ) as well as between juveniles and adults. A relative increase in the unit cell dimensions a / c ratio of nanocrystallites during growth was apparent in areas demonstrating single-crystal behaviour, but no such relationship was seen in dominantly polycrystalline areas. Systematic variations in mosaicity were identified, with mosaicity (as a proxy for disorder) increasing during growth, as well as along elements from tip to base. These results provide potential insight into the integrity of conodont apatite as a recorder of palaeoseawater chemistry, as well as demonstrate the need to consider the influence of ontogeny and element type on the use of conodonts in palaeothermometry and geochemical investigations.

scholarly journals Phytophthora Diversity in Pennsylvania Nurseries and Greenhouses Inferred from Clinical Samples Collected over Four Decades

2020 ◽  
Vol 8 (7) ◽  
pp. 1056
Author(s):  
Cody Molnar ◽  
Ekaterina Nikolaeva ◽  
Seonghwan Kim ◽  
Tracey Olson ◽  
Devin Bily ◽  
...  
Keyword(s):  
Plant Species ◽  
Morphological Characteristics ◽  
Phytophthora Species ◽  
Clinical Samples ◽  
Department Of Agriculture ◽  
Distinct Subgroup ◽  
Exotic Pathogens ◽  
Diverse Plant Species ◽  
Insight Into ◽  
Diverse Plant

The increasing movement of exotic pathogens calls for systematic surveillance so that newly introduced pathogens can be recognized and dealt with early. A resource crucial for recognizing such pathogens is knowledge about the spatial and temporal diversity of endemic pathogens. Here, we report an effort to build this resource for Pennsylvania (PA) by characterizing the identity and distribution of Phytophthora species isolated from diverse plant species in PA nurseries and greenhouses. We identified 1137 Phytophthora isolates cultured from clinical samples of >150 plant species submitted to the PA Department of Agriculture for diagnosis from 1975 to 2019 using sequences of one or more loci and morphological characteristics. The three most commonly received plants were Abies, Rhododendron, and Pseudotsuga. Thirty-six Phytophthora species identified represent all clades, except 3 and 10, and included a distinct subgroup of a known species and a prospective new species. Prominent pathogenic species such as P. cactorum, P. cinnamomi, P. nicotianae, P. drechsleri, P. pini, P. plurivora, and P. sp. kelmania have been found consistently since 1975. One isolate cultured from Juniperus horizontalis roots did not correspond to any known species, and several other isolates also show considerable genetic variation from any authentic species or isolate. Some species were isolated from never-before-documented plants, suggesting that their host range is larger than previously thought. This survey only provides a coarse picture of historical patterns of Phytophthora encounters in PA nurseries and greenhouses because the isolation of Phytophthora was not designed for a systematic survey. However, its extensive temporal and plant coverage offers a unique insight into the association of Phytophthora with diverse plants in nurseries and greenhouses.

Falcatifolium (Podocarpaceae) macrofossils from paleogene sediments in south-eastern Australia: a reassessment

1998 ◽  
Vol 11 (6) ◽  
pp. 711 ◽  
Author(s):  
Robert S. Hill ◽  
Leonie J. Scriven
Keyword(s):  
Leaf Morphology ◽  
Middle Eocene ◽  
Late Eocene ◽  
South Eastern ◽  
Early Oligocene ◽  
Extant Species ◽  
Eastern Australia ◽  
South Eastern Australia

A re-investigation of macrofossils previously referred to the extantpodocarpaceous genus Falcatifolium Laubenfels shows thatno records can be sustained. Falcatifolium australisD.R.Greenwood from Middle Eocene sediments in Victoria bears littleresemblance to extant species in the genus and is transferred to the newfossil genus Sigmaphyllum R.S.Hill & L.J.Scriven.Specimens from Early Oligocene sediments in Tasmania previously assigned toFalcatifolium are described as a second species ofSigmaphyllum, S. tasmanensisR.S.Hill & L.J.Scriven, and specimens from mid to late Eocene sediments inTasmania previously assigned to Falcatifolium do notbelong to that genus, although their true generic affinities are uncertain.Dispersed cuticle specimens from Late Eocene–Oligocene sediments inSouth Australia referred to Falcatifolium are notreliable records of the genus and require further investigation. However,Dacrycarpus eocenica D.R.Greenwood, from Middle Eocenesediments in Victoria is transferred to Falcatifolium,and is similar to the extant species F. angustumLaubenfels, which has a leaf morphology unusual for the genus.Falcatifolium eocenica (D.R.Greenwood) R.S.Hill & L.J.Scriven is the only reliable record of the genus in the Australian fossilrecord to date.

Paleoecology of Marine Foraminifera in the Pluvial Estancia Valley, Central New Mexico

1977 ◽  
Vol 7 (2) ◽  
pp. 254-267 ◽  
Author(s):  
F.W. Bachhuber ◽  
W.A. McClellan
Keyword(s):  
New Mexico ◽  
Air Temperature ◽  
Marine Environment ◽  
Developmental Stages ◽  
Geographic Location ◽  
Salinity Range ◽  
Extant Species ◽  
Lake Temperature ◽  
Minimum Depth ◽  
Unusual Occurrence

Two species of marine Foraminifera have been identified in the Quaternary pluvial sequence of the Estancia Valley, central New Mexico. Besides being an unusual occurrence of marine organisms in an inland body of water remote from the marine environment, the Foraminifera yield useful paleolimnological and paleoclimatological information about two major late Wisconsin pluvial lakes. In addition, the geographic location of the Estancia Valley relative to the closest marine environment requires foraminiferal introduction by avian means. Paleontologic evidence verifies the freshwater nature of the pluvial maxima of Late Lake Estancia (18,000-10,500 BP) and Lake Willard (8500-6000 BP) but early lake conditions were considerably different. The occurrence of foraminifers Cribroelphidium selseyense and Protelphidium orbiculare, both extant species, in the sediments from the early part of each pluvial stand indicates that initial lake development was characterized by a salinity range of 25 to 35‰. At these times lake depth approximated 6 m. By comparison, the freshwater maximum of Late Lake Estancia attained a minimum depth of 90 m. The modern holarctic distribution of the Foraminifera could suggest a mean August lake temperature of 10°C during the developmental stages of Late Lake Estancia and Lake Willard. Because of the shallow-water nature of the lake basins it is likely that this temperature was reflective of mean August air temperature. Therefore, a lowering of mean August air temperature of 9.7°C from that of the present is possible.

scholarly journals A taxonomic review of pterotracheoid gastropod mollusks from California Current waters off the west coast of North America

Zoosymposia ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 147-150
Author(s):  
ROGER R. SEAPY
Keyword(s):  
North America ◽  
West Coast ◽  
Morphological Characteristics ◽  
California Current ◽  
Single Species ◽  
The West ◽  
Taxonomic Review ◽  
Gastropod Mollusks ◽  
Taxonomic Characterization

Taxonomic characterization of pterotracheoid gastropods, morphological characteristics and occurrence in California Current waters are reviewed. Single species of atlantid (Atlanta californiensis) and carinariid (Carinaria japonica) from these waters are described and illustrated.

Cranial morphology and systematics of an extraordinary sample of the Late Neogene dwarf tapir, Tapirus polkensis (Olsen)

2009 ◽  
Vol 83 (2) ◽  
pp. 238-262 ◽  
Author(s):  
Richard C. Hulbert ◽  
Steven C. Wallace ◽  
Walter E. Klippel ◽  
Paul W. Parmalee
Keyword(s):  
Single Species ◽  
Relative Strength ◽  
Cranial Morphology ◽  
Linear Measurements ◽  
Average Mass ◽  
Gray Fossil Site ◽  
Extant Species ◽  
Late Neogene ◽  
Fossil Site ◽  
Almost All

The previously poorly known “Tapiravus” polkensis Olsen, 1960 (Mammalia, Perissodactyla, Tapiridae) is now known from abundant, well preserved specimens from both the type area in central Florida and from the Gray Fossil Site (GFS) in eastern Tennessee. The latter has produced over 75 individuals, the greatest number of tapirids from a single fossil site, including many articulated skeletons. Almost all linear measurements taken on skulls, mandibles, and cheek teeth from GFS have coefficients of variation less than 10 (most between 3 and 7), indicating the presence of a single species. However, the sample reveals considerable intraspecific variation for a few key morphologic features, including development of the sagittal crest, outline shape of the nasals, and number and relative strength of lingual cusps on the P1. The Florida sample of T. polkensis is more limited, but has the same state as the GFS sample for all preserved characters of systematic significance, and while the Florida teeth are on average smaller (especially narrower lower cheek teeth), they fall either within or just below the observed range of the Gray Fossil Site population. The new material supports a reassignment of “Tapiravus” polkensis to the genus Tapirus, and demonstrates that the geologic age of the species is significantly younger than previously thought, Hemphillian rather than Barstovian. Tapirus polkensis is the smallest known North American Tapirus, and smaller than any of the extant species in the genus, with an estimated average mass of 125 kg.

scholarly journals Ecological specialisation and evolutionary reticulation in extant Hyaenidae

2020 ◽  
Author(s):  
M V Westbury ◽  
Diana Le Duc ◽  
David A. Duchêne ◽  
Arunkumar Krishnan ◽  
Stefan Prost ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Single Species ◽  
Spotted Hyena ◽  
Genetic Changes ◽  
Slow Decline ◽  
Extant Species ◽  
Phylogenetic Discordance ◽  
Population Sizes ◽  
Olfactory Receptor Genes ◽  
Striped Hyena

AbstractDuring the Miocene, Hyaenidae was a highly diverse family of Carnivora that has since been severely reduced to four extant genera, each of which contains only a single species. These species include the bone-cracking spotted, striped, and brown hyenas, and the specialised insectivorous aardwolf. Previous genome studies have analysed the evolutionary histories of the spotted and brown hyenas, but little is known about the remaining two species. Moreover, the genomic underpinnings of scavenging and insectivory, defining traits of the extant species, remain elusive. To tackle these questions, we generated an aardwolf genome and analysed it together with those from the other three species. We provide new insights into the evolutionary relationships between the species, the genomic underpinnings of their scavenging and insectivorous lifestyles, and their respective genetic diversities and demographic histories. High levels of phylogenetic discordance within the family suggest gene flow between the aardwolf lineage and the ancestral brown/striped hyena lineage. Genes related to immunity and digestion in the bone-cracking hyenas and craniofacial development in the aardwolf showed the strongest signals of selection in their respective lineages, suggesting putative key adaptations to carrion or termite feeding. We also found a family-wide expansion in olfactory receptor genes suggesting that an acute sense of smell was a key early adaptation for the Hyaenidae family. Finally, we report very low levels of genetic diversity within the brown and striped hyenas despite no signs of inbreeding, which we putatively link to their similarly slow decline in Neover the last ∼2 million years. We found much higher levels of genetic diversity in both the spotted hyena and aardwolf and more stable population sizes through time. Taken together, these findings highlight how ecological specialisation can impact the evolutionary history, demographics, and adaptive genetic changes of a lineage.

scholarly journals Additional records and stratigraphic distribution of the middle Eocene carettochelyid turtle Anosteira pulchra from the Uinta Formation of Utah, North America

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9775
Author(s):  
Brent Adrian ◽  
Patricia A. Holroyd ◽  
J. Howard Hutchison ◽  
KE Beth Townsend
Keyword(s):  
North America ◽  
New Records ◽  
Middle Eocene ◽  
Single Species ◽  
Uinta Basin ◽  
Stratigraphic Framework ◽  
Multiple Levels ◽  
Land Mammal ◽  
Anatomical Information ◽  
Insight Into

Background Anosteira pulchra is one of two species of the obligately-aquatic freshwater clade Carettochelyidae (pig-nosed turtles) from the Eocene of North America. Anosteira pulchra is typically rare in collections, and their distribution is poorly documented. The Uinta Formation [Fm.] contains a diverse assemblage of turtles from the Uintan North American Land Mammal Age. Whereas turtles are abundantly preserved in the Uinta Fm., A. pulchra has been reported only from a few specimens in the Uinta C Member. Methods We describe new records of Anosteira pulchra from the Uinta Basin and analyze the distribution of 95 specimens from multiple repositories in the previously published stratigraphic framework of the middle and upper Uinta Fm. Results Here we report the first records of the species from the Uinta B interval, document it from multiple levels within the stratigraphic section and examine its uncommon appearance in only approximately 5% of localities where turtles have been systematically collected. This study details and extends the range of A. pulchra in the Uinta Fm. and demonstrates the presence of the taxon in significantly lower stratigraphic layers. These newly described fossils include previously unknown elements and associated trace fossils, with new anatomical information presented. This study provides insight into the taxonomy of Anosteira spp. in the middle Eocene, and suggests the presence of a single species, though no synonymy is defined here due to limits in Bridger material.

The community structure of larval fish populations in an area of the Celtic Sea in 1998

2002 ◽  
Vol 82 (4) ◽  
pp. 641-648 ◽  
Author(s):  
S. Acevedo ◽  
O. Dwane ◽  
J.M. Fives
Keyword(s):  
Community Structure ◽  
Fish Species ◽  
Larval Fish ◽  
Single Species ◽  
Coastal Fish ◽  
Larval Stages ◽  
Celtic Sea ◽  
Sea Area ◽  
Insight Into ◽  
Fish Distributions

Ichthyoplankton from an area in the Celtic Sea was studied to provide an insight into the fish larval community structure in March, May and June 1998. Three station groups were defined each month, Neritic, Transition and Oceanic. The Neritic assemblages included larval stages of coastal fish species and the Oceanic assemblages included mesopelagic and high-oceanic fish species which were not recorded from any of the Neritic stations. The Transition stations usually contained species characteristic of both the Neritic and Oceanic assemblages. It is suggested that these broad patterns of larval fish distributions are constant features of the Celtic Sea area, probably related to the spawning location of the adults. The area is, in general, species poor, with the Oceanic stations usually dominated by a single species, indicating the presence of a large spawning school of fish.

Why Don't You Act Your Age?

2021 ◽  
Author(s):  
Michael Green
Keyword(s):  
Search Engines ◽  
Text Comprehension ◽  
Developmental Stages ◽  
Search Behavior ◽  
Random Forest Classifier ◽  
Strong Impact ◽  
Online Search ◽  
Concrete Operational ◽  
Direct Feedback ◽  
Insight Into

Online search engines for children are known to filter retrieved resources based on page complexity, and offer specialized functionality meant to address gaps in search literacy according to a user's age or grade. However, not every searcher grouped by these identifiers displays the same level of text comprehension, or requires the same aid with search. Furthermore, these search engines typically rely on direct feedback to ascertain these identifiers. This reliance on self identification may cause users to accidentally misrepresent themselves. We therefore seek to recognize users from skill based signals rather than utilizing age or grade identifiers, as skill dictates appropriate aid and resources. Therefore, in this thesis we propose a strategy that automatically recognizes users on the fly by analyzing search behavior found in search sessions. In particular, our efforts focus on recognizing the stereotypical 8 to 12 year old searcher, who we posit exhibits skills defined by developmental stages that have a strong impact on language development (Piaget's concrete operational stage) and search literacy (digital competency's first level). This strategy analyzes user-generated text extracted from queries and patterns of search interactions in order to infer features that are leveraged by a random forest classifier in order to determine whether or not a user is a part of this specific segment of searchers. The outcomes from this thesis lay the groundwork for enabling search engines to recognize users based on their search skills and provides further insight into the search behavior of youths.

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