Structure and habits of living branchiopod crustaceans and their bearing on the interpretation of fossil forms

1985 ◽  
Vol 76 (2-3) ◽  
pp. 103-113 ◽  
Author(s):  
Geoffrey Fryer
Keyword(s):  
Recent Work ◽  
Adaptive Radiation ◽  
Living Animal ◽  
Genomic Evolution ◽  
Living Fossil ◽  
Larval Stages ◽  
Living Fossils ◽  
Morphological Stasis

ABSTRACTBranchiopods are primitive crustaceans whose history extends back at least to the Devonian, yet some are highly successful today. Most fossil branchiopods do not show many features that lead to an understanding of function, but the Devonian lipostracan Lepidocaris is an exception. Recent work on living branchiopods, especially anostracans and anomopod cladocerans, enables Lepidocaris to be considered as a living animal. Work on extant anostracan nauplii also makes it possible to deduce how its larval stages swam and collected food.Other early crustaceans are briefly considered and comments are made on the concept of “living fossils”. While rates of morphological and genomic evolution are often discordant, the concept is still useful. Some branchiopods, such as the Notostraca, display remarkable morphological stasis: on the basis of morphology, a Triassic and a present-day form appear to be conspecific. The latter may be referred to as a “living fossil”.The outstanding morphological stasis of the crustacean nauplius is noted. Its existence in Cambrian times, deducible from its distribution among modern taxa, has been confirmed by Müller's finds. Such stasis, involving part of the genome of organisms whose adults display enormous adaptive radiation, has persisted with relatively small modifications since before the commencement of the entire radiation of vertebrates.

scholarly journals The living fossil concept: reply to Turner

2021 ◽  
Vol 36 (2) ◽  
Author(s):  
Scott Lidgard ◽  
Alan C. Love
Keyword(s):  
Complex Problem ◽  
Morphological Stability ◽  
Main Argument ◽  
Geological Time ◽  
Problem Space ◽  
Living Fossil ◽  
Living Fossils ◽  
Tadpole Shrimps ◽  
Evolutionary Stasis

AbstractDespite the iconic roles of coelacanths, cycads, tadpole shrimps, and tuataras as taxa that demonstrate a pattern of morphological stability over geological time, their status as living fossils is contested. We responded to these controversies with a recommendation to rethink the function of the living fossil concept (Lidgard and Love in Bioscience 68:760–770, 2018). Concepts in science do useful work beyond categorizing particular items and we argued that the diverse and sometimes conflicting criteria associated with categorizing items as living fossils represent a complex problem space associated with answering a range of questions related to prolonged evolutionary stasis. Turner (Biol Philos 34:23, 2019) defends the living concept against a variety of recent skeptics, but his criticism of our approach relies on a misreading of our main argument. This misreading is instructive because it brings into view the value of three central themes for rethinking the living fossil concept—the function of concepts in biology outside of categorization, the methodological importance of distinguishing parts and wholes in conceptualizing evolutionary phenomena, and articulating diverse explanatory goals associated with these phenomena.

scholarly journals Resequencing 545 ginkgo genomes across the world reveals the evolutionary history of the living fossil

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Yun-Peng Zhao ◽  
Guangyi Fan ◽  
Ping-Ping Yin ◽  
Shuai Sun ◽  
Ning Li ◽  
...  
Keyword(s):  
Evolutionary History ◽  
Charles Darwin ◽  
Eastern China ◽  
Population Expansion ◽  
Fossil Species ◽  
Living Fossil ◽  
Living Fossils ◽  
Bioclimatic Variables ◽  
The World ◽  
History Of

Abstract As Charles Darwin anticipated, living fossils provide excellent opportunities to study evolutionary questions related to extinction, competition, and adaptation. Ginkgo (Ginkgo biloba L.) is one of the oldest living plants and a fascinating example of how people have saved a species from extinction and assisted its resurgence. By resequencing 545 genomes of ginkgo trees sampled from 51 populations across the world, we identify three refugia in China and detect multiple cycles of population expansion and reduction along with glacial admixture between relict populations in the southwestern and southern refugia. We demonstrate multiple anthropogenic introductions of ginkgo from eastern China into different continents. Further analyses reveal bioclimatic variables that have affected the geographic distribution of ginkgo and the role of natural selection in ginkgo’s adaptation and resilience. These investigations provide insights into the evolutionary history of ginkgo trees and valuable genomic resources for further addressing various questions involving living fossil species.

Are wounded-tree beetles living fossils? A new nosodendrid genus from Burmese amber with bilobed tarsi (Coleoptera: Nosodendridae)

2021 ◽  
Vol 4 (1) ◽  
pp. 050-056
Author(s):  
ERIK TIHELKA ◽  
YAN-DA LI ◽  
DI-YING HUANG ◽  
CHEN-YANG CAI
Keyword(s):  
New Genus ◽  
Unique Feature ◽  
Body Plan ◽  
Compound Eyes ◽  
Living Fossil ◽  
Burmese Amber ◽  
Climbing Plants ◽  
Living Fossils ◽  
Geological Past

Nosodendridae, the wounded-tree beetles, are a small polyphagan family with less than 100 described species placed into two extant and one fossil genera. Here we describe a new nosodendrid genus and species, Mesonosa scandens gen. et sp. nov., from mid-Cretaceous Burmese amber from northern Myanmar (ca. 99 Ma). The new genus differs from extant nosodendrids in its bilobed tarsomeres 2–4, as well as putatively plesiomorphic characters such as strongly protuberant compound eyes and relatively elongate prosternum. The distinctly lobed tarsi are a unique feature within Nosodendridae, and likely represent an adaptation for climbing plants. The discovery of a third wounded-tree beetle genus from the Mesozoic indicates that while their body plan remained relatively conserved since the Cretaceous, nosodendrids have been more ecomorphologically diverse in the geological past than the present day, and thus are an example of a true “living fossil” lineage.

scholarly journals Aenigmachannidae, a new family of snakehead fishes (Teleostei: Channoidei) from subterranean waters of South India

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Ralf Britz ◽  
Neelesh Dahanukar ◽  
V. K. Anoop ◽  
Siby Philip ◽  
Brett Clark ◽  
...  
Keyword(s):  
Morphological Analysis ◽  
South India ◽  
Sister Group ◽  
Phylogenetic Position ◽  
Fossil Calibration ◽  
New Family ◽  
Living Fossils ◽  
Morphological Stasis ◽  
The Family ◽  
Subterranean Waters

Abstract Pronounced organism-wide morphological stasis in evolution has resulted in taxa with unusually high numbers of primitive characters. These ‘living fossils’ hold a prominent role for our understanding of the diversification of the group in question. Here we provide the first detailed osteological analysis of Aenigmachanna gollum based on high-resolution nano-CT scans and one cleared and stained specimen of this recently described snakehead fish from subterranean waters of Kerala in South India. In addition to a number of derived and unique features, Aenigmachanna has several characters that exhibit putatively primitive conditions not encountered in the family Channidae. Our morphological analysis provides evidence for the phylogenetic position of Aenigmachanna as the sister group to Channidae. Molecular analyses further emphasize the uniqueness of Aenigmachanna and indicate that it is a separate lineage of snakeheads, estimated to have split from its sister group at least 34 or 109 million years ago depending on the fossil calibration employed. This may indicate that Aenigmachanna is a Gondwanan lineage, which has survived break-up of the supercontinent, with India separating from Africa at around 120 mya. The surprising morphological disparity of Aenigmachanna from members of the Channidae lead us to erect a new family of snakehead fishes, Aenigmachannidae, sister group to Channidae, to accommodate these unique snakehead fishes.

Deep genetic divergence within a “living fossil” brachiopodLingula anatina

2013 ◽  
Vol 87 (5) ◽  
pp. 902-908 ◽  
Author(s):  
Shujuan Yang ◽  
Xulong Lai ◽  
Guilian Sheng ◽  
Shuoshuo Wang
Keyword(s):  
Genetic Divergence ◽  
Marine Invertebrates ◽  
Genetic Distances ◽  
Living Fossil ◽  
Geographic Population ◽  
Mitochondrial Coi ◽  
China Sea ◽  
Morphological Stasis ◽  
Close Relationship ◽  
Gulf Of Tonkin

The geographic population patterns ofLingula anatinaacross the Indo-West Pacific region are analyzed based on mitochondrial COI and nuclear EF-1α gene sequences. Compared with the remarkable morphological stasis, genetic evidence of extantLingulaspecies displays deep genetic divergence. Three distinct COI lineages were detected forL. anatina, one of which is from Qinhuangdao (Hebei, China, Bohai Sea), the other two from Beihai (Guangxi, China, Gulf of Tonkin). Individuals from South Japan have a very close relationship with one of the two COI lineages found in Beihai, which is also supported by EF-1α results, suggesting a relatively recent migration between South China Sea and East China Sea. Genetic distances between the three lineages ofL. anatinaare rather high (8.9%, 8.6%, and 2.7%), and those betweenL. anatinaandL. adamsiis much higher (44.5%), compared to other marine invertebrates. Both tectonic evolution and the repeated Quaternary glaciations have contributed to the complex phylogeographic pattern found in these recentLingula anatinapopulations.

scholarly journals The first late cretaceous mawsoniid coelacanth (Sarcopterygii: Actinistia) from North America: Evidence of a lineage of extinct ‘living fossils’

PLoS ONE ◽  
2021 ◽  
Vol 16 (11) ◽  
pp. e0259292
Author(s):  
Lionel Cavin ◽  
Pablo Toriño ◽  
Nathan Van Vranken ◽  
Bradley Carter ◽  
Michael J. Polcyn ◽  
...  
Keyword(s):  
North America ◽  
Eastern Coast ◽  
Time Duration ◽  
Living Fossil ◽  
Living Fossils ◽  
Life Traits ◽  
Slow Evolution ◽  
Vertebrate Assemblage ◽  
Fossil Records ◽  
The Impact

Today, the only living genus of coelacanth, Latimeria is represented by two species along the eastern coast of Africa and in Indonesia. This sarcopterygian fish is nicknamed a "living fossil", in particular because of its slow evolution. The large geographical distribution of Latimeria may be a reason for the great resilience to extinction of this lineage, but the lack of fossil records for this genus prevents us from testing this hypothesis. Here we describe isolated bones (right angular, incomplete basisphenoid, fragments of parasphenoid and pterygoid) found in the Cenomanian Woodbine Formation in northeast Texas that are referred to the mawsoniid coelacanth Mawsonia sp. In order to assess the impact of this discovery on the alleged characteristic of "living fossils" in general and of coelacanths in particular: 1) we compared the average time duration of genera of ray-finned fish and coelacanth in the fossil record; 2) we compared the biogeographic signal from Mawsonia with the signal from the rest of the vertebrate assemblage of the Woodbine formation; and 3) we compared these life traits with those of Latimeria. The stratigraphical range of Mawsonia is at least 50 million years. Since Mawsonia was a fresh, brackish water fish with probably a low ability to cross large sea barriers and because most of the continental components of the Woodbine Fm vertebrate assemblage exhibit Laurasian affinities, it is proposed that the Mawsonia’s occurrence in North America is more likely the result of a vicariant event linked to the break-up of Pangea rather than the result of a dispersal from Gondwana. The link between a wide geographic distribution and the resilience to extinction demonstrated here for Mawsonia is a clue that a similar situation existed for Latimeria, which allowed this genus to live for tens of millions of years.

scholarly journals One More “Living Fossil”: Mesozoic Lineage Differentiation, Morphological Stasis and Weak Phylogeographic Structure in Eurasia in the Bosminopsis Deitersi Group (Crustacea: Cladocera: Bosminidae)

2020 ◽  
Author(s):  
Petr G. Garibian ◽  
Dmitry P. Karabanov ◽  
Anna N. Neretina ◽  
Derek J. Taylor ◽  
Alexey Kotov
Keyword(s):  
Morphological Evolution ◽  
Single Species ◽  
Species Group ◽  
Phylogeographic Structure ◽  
Species Problem ◽  
Living Fossil ◽  
Ecological Requirements ◽  
Lineage Differentiation ◽  
Morphological Stasis ◽  
The Family

Abstract Background: Water fleas (Crustacea: Cladocera) of the Family Bosminidae have been studied since the founding of paleolimnology and freshwater ecology. However, one species, Bosminopsis deitersi, stands out for its exceptional multicontinental range and broad ecological requirements. Results: Here we use an integrated morphological and multilocus genetic approach to to address the species problem in B. deitersi. We analyzed 32 populations of B. deitersi s. lat. Two nuclear and two mitochondrial loci were used to carry out the bGMYC, mPTP and STACEY algorithms for species delimitation. Detailed morphological study was also carried out across continents. The evidence indicated a widely distributed cryptic species in the Old World (Bosminopsis zernowi) that is genetically divergent from B. deitersi s.str. We revised the taxonomy and redescribed the species in this complex. Our sampling indicated that B. zernowi had weak genetic differentiation across its range. A molecular clock and biogeographic analysis with fossil calibrations suggested a Mesozoic origin for the Bosminopsis deitersi group. Conclusions: Our evidence rejects the single species hypothesis for B. deitersi and is consistent with an ancient species group (potentially Mesozoic) that shows marked morphological conservation. The family Bosminidae, then, has examples of both rapid morphological evolution (Holocene Bosmina), and morphological stasis (Bosminopsis).

scholarly journals Cretaceous fire-resistant angiosperms

2021 ◽  
Author(s):  
Shuo Wang ◽  
Chao Shi ◽  
Hao-hong Cai ◽  
Hong-rui Zhang ◽  
Xiao-xuan Long ◽  
...  
Keyword(s):  
South African ◽  
Fire Resistance ◽  
Sister Group ◽  
Living Fossil ◽  
Morphological Stasis ◽  
Core Eudicots ◽  
Fossil Flowers ◽  
Floral Characters ◽  
African Genus

Abstract Background: Flowering plants (angiosperms) dominate most global ecosystems today, but their rapid Cretaceous diversification has remained poorly understood ever since Darwin referred to it as an ‘abominable mystery’. Although numerous Cretaceous fossil flowers have been discovered in recent years, most are represented by incomplete charcoalified fragments that do not preserve delicate structures such as complete petals and surface textures, which means that their similarity to living forms is often difficult to discern. The scarcity of information about the ecology of early angiosperms makes it difficult to test hypotheses about the drivers of their diversification. Among other factors, frequent fires in the Cretaceous have been postulated as having possibly facilitated the rise of angiosperms. However, to date no early fossil angiosperms displaying fire-adapted traits have been known, making the role of fire in shaping Cretaceous floras uncertain.Results: We report the discovery of two exquisitely preserved fossil flower species, one identical to the inflorescences of the extant crown eudicot genus Phylica and the other recovered as a sister group to Phylica, both preserved as inclusions in Cretaceous amber from northern Myanmar (~99 Ma). These specialized flower structures, named Phylica piloburmensis sp. nov. and Eophylica priscastellata gen. et sp. nov., were adapted to surviving frequent wildfires, providing the earliest evidence of fire-resistance in angiosperms. The fossils suggest that fire was a significant selective force in Cretaceous angiosperm floras and that adaptations to fire resistance in some eudicot clades have been conserved for at least 99 Ma. This morphological stasis encompasses a range of floral characters, including the production of ‘pseudo-flowers’, and characteristic fruit and pollen architecture. Given its morphological distinctiveness, the Eophylica-Phylica clade represents one of the first well-documented angiosperm ‘living fossil’ genera from the Cretaceous. Conclusion: Our study suggests that core eudicots with specialised flower morphology displaying hallmarks of fire resistance and identical to those of the extant south African genus Phylica, had originated by the mid-Cretaceous (~99 Ma). Palaeoenvironmental reconstructions indicate that these plants lived in conditions similar to those of present-day southern Africa where 70% of taxa survive frequent burning, and that fire resistance was probably widespread in the fire-prone Cretaceous. The results also provide new insights into the biogeographic origin of at least one element of the highly endemic Greater Cape Region biodiversity hotspot flora biota.

What sentimentalists should say about emotion

2019 ◽  
Vol 42 ◽  
Author(s):  
Charlie Kurth
Keyword(s):  
Moral Judgment ◽  
Recent Work ◽  
Relevant Information ◽  
Moral Cognition ◽  
Multilevel Structure

Abstract Recent work by emotion researchers indicates that emotions have a multilevel structure. Sophisticated sentimentalists should take note of this work – for it better enables them to defend a substantive role for emotion in moral cognition. Contra May's rationalist criticisms, emotions are not only able to carry morally relevant information, but can also substantially influence moral judgment and reasoning.

The Sun as a Magnetic Star

1976 ◽  
Vol 32 ◽  
pp. 457-463
Author(s):  
John M. Wilcox ◽  
Leif Svalgaard
Keyword(s):  
Recent Work ◽  
Rotation Axis ◽  
Polar Field ◽  
Magnetic Star ◽  
Rotational Axis ◽  
Field Variation ◽  
The Sun ◽  
Arbitrary Angle ◽  
Solar Magnetism ◽  
Oblique Rotator

SummaryThe sun as a magnetic star is described on the basis of recent work on solar magnetism. Observations at an arbitrary angle to the rotation axis would show a 22-year polar field variation and a 25-day equatorial sector variation. The sector variation would be similar to an oblique rotator with an angle of 90° between the magnetic and rotational axis.

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