scholarly journals A critical revision of the fossil record, stratigraphy and diversity of the Neogene seal genus Monotherium (Carnivora, Phocidae)

2018 ◽  
Vol 5 (5) ◽  
pp. 171669 ◽  
Author(s):  
Leonard Dewaele ◽  
Olivier Lambert ◽  
Stephen Louwye
Keyword(s):  
North Atlantic ◽  
Fossil Record ◽  
East Coast ◽  
Late Oligocene ◽  
Deep Time ◽  
Western Atlantic ◽  
The North ◽  
Fossil Material ◽  
Phocid Seals ◽  
Critical Revision

Historically, Monotherium had been one of the few genera of extinct Phocidae (true seals) that served as a wastebin taxon. Consequently, it did neither aid in understanding phylogenetic relationships of extinct Phocidae, nor in understanding seal diversity in deep time. This urged the reassessment of the genus. Before our review, Monotherium included five different species: Monotherium aberratum , Monotherium affine , and Monotherium delognii from Belgium; Monotherium gaudini from Italy; and Monotherium ? wymani from the east coast USA. In this work we redescribe the fossil record of the genus, retaining the type species M. delognii . Monotherium aberratum and M. affine are reassigned to the new phocine genus Frisiphoca . Monotherium gaudini is renamed and considered a stem-monachine ( Noriphoca gaudini ). The holotype of the monachine M. ? wymani requires further study pending the discovery of new fossil material that could be attributed to the same taxon. Reinvestigating the stratigraphic context reveals that N. gaudini most likely represents one of the two oldest named phocid seals, or even the oldest, dated to the late Oligocene–earliest Miocene. Our results allow questioning the widespread idea that Phocidae originated in the western Atlantic and better appreciate their palaeobiogeography during the late Oligocene–Miocene interval in the North Atlantic realm.

A Review of the Morid Fish Genus Halargyreus with First Records from the Western North Atlantic

1968 ◽  
Vol 25 (5) ◽  
pp. 877-901 ◽  
Author(s):  
Wilfred Templeman
Keyword(s):  
New Zealand ◽  
North Atlantic ◽  
The Other ◽  
Nominal Species ◽  
Meristic Characters ◽  
Western Atlantic ◽  
North Central ◽  
Northeast Atlantic ◽  
The North

Three specimens of Halargyreus johnsonii taken on the southwestern and southeastern slopes of the Grand Bank in 1959 and 1964 are apparently the first records of this species and genus from the western Atlantic. These specimens are compared with the holotypes of H. johnsonii Günther and of H. brevipes Vaillant and with the syntypes of H. affinis Collett and also with specimens identified as H. affinis from the north-central and northeast Atlantic and with specimens of H. johnsonii from Madeira and New Zealand. These three nominal species are also compared. Is it concluded that for the present all North Atlantic specimens may be referred to H. johnsonii and that the other two species names should be considered as junior synonyms of H. johnsonii.The New Zealand specimens of Halargyreus, described by Günther (1887, Challenger Rept., 22(Zoology), p. 1–268) as H. johnsonii, have higher numbers for some meristic characters than Atlantic specimens of H. johnsonii but these differences are not too great to be possibly due to environmental differences. Pending the study of additional specimens in better condition, these New Zealand specimens are tentatively allowed to remain as H. johnsonii.

scholarly journals C14 content of recent molluscs from Scoresby Sund, central East Greenland

1975 ◽  
Vol 75 ◽  
pp. 95-99
Author(s):  
H Tauber ◽  
S Funder
Keyword(s):  
North Atlantic ◽  
East Coast ◽  
Marine Organisms ◽  
Water Masses ◽  
Lower Activity ◽  
Terrestrial Plants ◽  
East Greenland ◽  
The North ◽  
The North Atlantic ◽  
Turn Over

C14 dating of subfossil marine shelIs presupposes a knowledge of the original C14 activity of the organisms while living. Due to the slow turn over of water masses, the C14 activity of marine bicarbonate and marine organisms is not the same in all parts of the oceans, but may show marked deficiencies in certain oceanic areas, especially at southern latitudes. In large areas of the North Atlantic the C14 activity seems to be fairly uniform and equal to or only slightly lower than that of 'pre-industrial' terrestrial plants (Broecker et al., 1960; Mangerud, 1972; Krog & Tauber, 1974). In certain areas, however, a somewhat lower activity seems to occur; trus has been noted for areas along the east coast of Greenland (Fonselius & Ostlund, 1959; Hjort, 1973).

scholarly journals Spider crabs of the Western Atlantic with special reference to fossil and some modern Mithracidae

PeerJ ◽  
2015 ◽  
Vol 3 ◽  
pp. e1301 ◽  
Author(s):  
Adiël A. Klompmaker ◽  
Roger W. Portell ◽  
Aaron T. Klier ◽  
Vanessa Prueter ◽  
Alyssa L. Tucker
Keyword(s):  
Fossil Record ◽  
Early Pleistocene ◽  
Caribbean Region ◽  
Deep Time ◽  
Western Atlantic ◽  
Extant Species ◽  
Length Width ◽  
The Caribbean ◽  
Abundance And Diversity ◽  
First Time

Spider crabs (Majoidea) are well-known from modern oceans and are also common in the western part of the Atlantic Ocean. When spider crabs appeared in the Western Atlantic in deep time, and when they became diverse, hinges on their fossil record. By reviewing their fossil record, we show that (1) spider crabs first appeared in the Western Atlantic in the Late Cretaceous, (2) they became common since the Miocene, and (3) most species and genera are found in the Caribbean region from the Miocene onwards. Furthermore, taxonomic work on some modern and fossil Mithracidae, a family that might have originated in the Western Atlantic, was conducted. Specifically,Maguimithraxgen. nov. is erected to accommodate the extant speciesDamithrax spinosissimus, whileDamithraxcf.pleuracanthusis recognized for the first time from the fossil record (late Pliocene–early Pleistocene, Florida, USA). Furthermore, two new species are described from the lower Miocene coral-associated limestones of Jamaica (Mithrax arawakumsp. nov. andNemausa windsoraesp. nov.). Spurred by a recent revision of the subfamily, two known species from the same deposits are refigured and transferred to new genera:Mithrax donovanitoNemausa, andMithrax unguistoDamithrax. The diverse assemblage of decapods from these coral-associated limestones underlines the importance of reefs for the abundance and diversity of decapods in deep time. Finally, we quantitatively show that these crabs possess allometric growth in that length/width ratios drop as specimens grow, a factor that is not always taken into account while describing and comparing among taxa.

scholarly journals Salishicetus meadi , a new aetiocetid from the late Oligocene of Washington State and implications for feeding transitions in early mysticete evolution

2018 ◽  
Vol 5 (4) ◽  
pp. 172336 ◽  
Author(s):  
Carlos Mauricio Peredo ◽  
Nicholas D. Pyenson
Keyword(s):  
North Pacific ◽  
Fossil Record ◽  
Feeding Strategy ◽  
Washington State ◽  
Late Oligocene ◽  
Baleen Whales ◽  
The North ◽  
Occlusal Wear ◽  
Basal Clade ◽  
The North Pacific

Living baleen whales, or Mysticeti, lack teeth and instead feed using keratinous baleen plates to sieve prey-laden water. This feeding strategy is profoundly different from that of their toothed ancestors, which processed prey using the differentiated dentition characteristic of mammals. The fossil record of mysticetes reveals stem members that include extinct taxa with dentition, illuminating the morphological states that preceded the loss of teeth and the subsequent origin of baleen. The relationships among stem mysticetes, including putative clades such as Mammalodontidae and Aetiocetidae, remain debatable. Aetiocetids are among the more species-rich clade of stem mysticetes, and known only from fossil localities along the North Pacific coastline. Here, we report a new aetiocetid, Salishicetus meadi gen. et sp. nov, from the late Oligocene of Washington State, USA. Salishicetus preserves a near-complete lower dentition with extensive occlusal wear, indicating that it processed prey using shearing cheek teeth in the same way as its stem cetacean ancestors. Using a matrix with all known species of aetiocetids, we recover a monophyletic Aetiocetidae, crownward of a basal clade of Mammalodontidae. The description of Salishicetus resolves phylogenetic relationships among aetiocetids, which provides a basis for reconstructing ancestral feeding morphology along the stem leading to crown Mysticeti.

A Review of the Morid Fish Genus Lepidion of the North Atlantic With First Records of Lepidion eques from the Western North Atlantic

1970 ◽  
Vol 27 (3) ◽  
pp. 457-498 ◽  
Author(s):  
Wilfred Templeman
Keyword(s):  
North Atlantic ◽  
Sexual Maturity ◽  
Head Length ◽  
Western Atlantic ◽  
Morphometric Characters ◽  
Northeast Atlantic ◽  
West Greenland ◽  
Biological Station ◽  
The North ◽  
The North Atlantic

Seventeen specimens of Lepidion eques (Günther) taken by the Fisheries Research Board of Canada St. John's, Nfld., Biological Station are apparently the first records of the species from the western Atlantic west of West Greenland. Comparison with specimens from the northeast Atlantic shows some differences in averages of meristic and morphometric characters, but with overlapping ranges in these characters.Comparison of these North Atlantic L. eques with the Mediterranean Lepidion lepidion (Risso) revealed that although closely related, these species are separable on the bases of the smaller orbit diameter in relation to the head length and especially by the relatively larger postorbital length in L. lepidion. Lepidion guentheri (Giglioli) is distinctly different from these two species in some meristic and many morphometric characters. Lectotypes of L. eques and L. guentheri are designated. Various incorrect or doubtful records of Lepidion are discussed. Two giant lepidions reported recently from the northeast Atlantic as L. guentheri are tentatively assigned to Lepidion schmidti Svetovidov, a species hitherto known only from Japan.The distributions of the North Atlantic species of Lepidion are discussed and information is provided on sexual maturity.

Greenland halibut (Reinhardtius hippoglossoides) in the North Atlantic are genetically homogeneous

1997 ◽  
Vol 54 (8) ◽  
pp. 1813-1821 ◽  
Author(s):  
M L Vis ◽  
S M Carr ◽  
W R Bowering ◽  
W S Davidson
Keyword(s):  
North Atlantic ◽  
Gadus Morhua ◽  
Genetic Distances ◽  
Greenland Halibut ◽  
Western Atlantic ◽  
Grand Banks ◽  
The North ◽  
Greenland Halibut Reinhardtius Hippoglossoides ◽  
The North Atlantic ◽  
Reinhardtius Hippoglossoides

Greenland halibut (Reinhardtius hippoglossoides) have become of great importance to the Canadian fishery since the moratorium on northern cod (Gadus morhua), and an understanding of stock relationships among populations at the northern and southern extremes of their commercial range is crucial for proper management. We compared mitochondrial DNA sequence variation among fish taken from thoughout the Northwest Atlantic (Flemish Pass, the Grand Banks, Davis Strait, and Northwest Greenland) with samples from the Gulf of St. Lawrence, Iceland, and Norway. Within a 401 base pair portion of the cytochrome b gene, 22 genotypes were identified. Three of these occur at frequencies >10% and in the same relative abundances in all samples (except the Gulf of St.Lawrence). Genotype proportions do not differ significantly among samples, and genetic subdivision among samples (measured by the coancestry coefficient theta ) is nil. Genetic distances among samples are not related to geographic distribution: pairwise differences between the Gulf sample and other western Atlantic samples exceed those for trans-Atlantic comparisons. These data suggest that there is sufficient mixing of Greenland halibut, not only within the NAFO regulatory area, but among sites in the North Atlantic generally, to prevent the development or maintenance of genetically independent stocks.

scholarly journals Synoptic influences on springtime tropospheric O<sub>3</sub> and CO over the North American export region observed by TES

2009 ◽  
Vol 9 (11) ◽  
pp. 3755-3776 ◽  
Author(s):  
J. Hegarty ◽  
H. Mao ◽  
R. Talbot
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North American ◽  
East Coast ◽  
North Atlantic Ocean ◽  
Free Troposphere ◽  
The North ◽  
Circulation Patterns ◽  
The Us ◽  
Us East Coast

Abstract. The relationship between synoptic circulation patterns over the western North Atlantic Ocean in spring (March, April, and May) and tropospheric O3 and CO was investigated using retrievals from the Tropospheric Emission Spectrometer (TES) for 2005 and 2006. Seasonal composites of TES retrievals reprocessed to remove the artificial geographic structure added from the a priori revealed a channel of slightly elevated O3 (>55 ppbv) and CO (>115 ppbv) at the 681 hPa retrieval level between 30° N and 45° N extending from North America out over the Atlantic Ocean. Ozone and CO in this region were correlated at r=0.22 with a slope value of 0.13 mol mol−1 indicative of the overall impact of photochemical chemical processes in North American continental export. Composites of TES retrievals for the six predominant circulation patterns identified as map types from sea level pressure fields of the NCEP FNL analyses showed large variability in the distribution of tropospheric O3. Map types MAM2 and MAM3 featuring cyclones near the US east coast produced the greatest export to the lower free troposphere with O3>65 ppbv and a relatively well-defined O3-CO correlation (slope values near 0.20 mol mol−1). The ensembles of HYSPLIT backward trajectories indicated that the high O3 levels were possibly a result of pollutants lofted to the free troposphere by the warm conveyor belt (WCB) of a cyclone. An important finding was that pollutant export occurred in the main WCB branch to the east of the cyclone and in a secondary branch circling to the back of the cyclone center. Conversely, a map type featuring a large anticyclone dominating the flow over the US east coast (MAM6) restricted export with O3 levels generally <55 ppbv and CO levels generally <110 ppbv. There was also evidence of stratospheric intrusions particularly to the north of 45° N in the 316 hPa composites predominately for MAM1 which featured a large cyclone near Newfoundland. However, the concurrence of these intrusions with pollutant export, specifically in the southwestern North Atlantic Ocean, made it difficult to delineate their respective contributions to the 681 hPa O3 composites.

Decadal Relationship between European Blocking and the North Atlantic Oscillation during 1978–2011. Part I: Atlantic Conditions

2015 ◽  
Vol 72 (3) ◽  
pp. 1152-1173 ◽  
Author(s):  
Dehai Luo ◽  
Yao Yao ◽  
Aiguo Dai
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Western Europe ◽  
Storm Track ◽  
Western Atlantic ◽  
Atlantic Sector ◽  
The North ◽  
Nao Index ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract Both the positive and negative phases of the North Atlantic Oscillation (NAO+ and NAO−, respectively) and atmospheric blocking in the Euro-Atlantic sector reflect synoptic variability over the region and thus are intrinsically linked. This study examines their relationship from a decadal change perspective. Since the winter-mean NAO index is defined as a time average of instantaneous NAO indices over the whole winter, it is unclear how the activity of European blocking (EB) events can be related to the variation of the positive mean NAO index. Here, this question is examined by dividing the winter period 1978–2011 into two decadal epochs: 1978–94 (P1) with an increasing and high NAO index and 1995–2011 (P2) with a decreasing and low NAO index. Using atmospheric reanalysis data, it is shown that there are more intense and persistent EB events in eastern Europe during P1 than during P2, while the opposite is true for western Europe. It is further shown that there are more NAO+ (NAO−) events during P1 (P2). The EB events associated with NAO+ events extend more eastward and are associated with stronger Atlantic mean zonal wind and weaker western Atlantic storm track during P1 than during P2, but EB events associated with NAO− events increase in western Europe under opposite Atlantic conditions during P2. Thus, the increase in the number of individual NAO+ (NAO−) events results in more EB events in eastern (western) Europe during P1 (P2). The EB change is also associated with the increased frequency of NAO− to NAO+ (NAO+ to NAO−) transition events.

Geochronology and continental drift—the North Atlantic

1965 ◽  
Vol 258 (1088) ◽  
pp. 180-191 ◽  
Keyword(s):  
North Atlantic ◽  
East Coast ◽  
Continental Drift ◽  
Oceanic Islands ◽  
Northern Europe ◽  
Mean Square ◽  
The West ◽  
The North ◽  
The North Atlantic ◽  
Centre Of Rotation

A geometrical fit of the land masses of northern Europe, Canada and Greenland has been constructed by Dr A. G. Smith using the method devised by Sir Edward Bullard and M r J. E. Everett. The method involves taking points of latitude and longitude on the 500 fm. line at intervals of about 30 miles along the two coasts to be fitted. Young features such as oceanic islands are ignored. By a method of successive approximation, the computer ‘homes in ’ on to the centre of rotation which gives the minimum root mean square misfit between the rotated coastlines j the misfit being measured as the discrepancy of longitude relative to the centre of rotation. In this manner the 500 fm. line along the east coast of Greenland has been fitted to that of northwestern Europe to form one unit. This unit, that is, the 500 fm. line of the west coast of Greenland and the Channel approaches have been fitted on to the 500 fm. line of Canada. Maps of this fit drawn as a conical projection with two standard parallels of latitude will be presented and will show the geochronological patterns across the reconstructed land masses.

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