scholarly journals OnProphocaandLeptophoca(Pinnipedia, Phocidae) from the Miocene of the North Atlantic realm: redescription, phylogenetic affinities and paleobiogeographic implications

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3024 ◽  
Author(s):  
Leonard Dewaele ◽  
Olivier Lambert ◽  
Stephen Louwye
Keyword(s):  
North America ◽  
Middle Miocene ◽  
New Combination ◽  
Phylogenetic Position ◽  
Appendicular Skeleton ◽  
Original Diagnosis ◽  
Sediment Samples ◽  
The North ◽  
The North Sea ◽  
Phylogenetic Affinities

BackgroundProphocaandLeptophocarepresent the oldest known genera of phocine seals, dating from the latest early to middle Miocene. Originally,Prophoca rousseauiandProphoca proximawere described based on fragmentary remains from the Miocene of Belgium. However, several researchers contested the union ofProphoca rousseauiandProphoca proximainto one genus, without providing evidence. The stratigraphic context ofProphocaremained poorly constrained due to the lack of precise data associated with the original specimens collected in the area of Antwerp (north of Belgium).MethodsProphocaandLeptophocaare redescribed and their phylogenetic position among Phocidae is reassessed using PAUP. Dinoflagellate biostratigraphy has been carried out on sediment samples associated with specimens fromProphocaandLeptophocato elucidate their approximate ages.ResultsWhereas the speciesProphoca rousseauiis redescribed,Prophoca proximais considered synonymous toLeptophoca lenis, with the proposal of a new combinationLeptophoca proxima(Van Beneden, 1877). Sediment samples from specimens of both taxa have been dated to the late Langhian–early Serravallian (middle Miocene). Following a reinvestigation ofLeptophoca amphiatlantica, characters from the original diagnosis are questioned and the specimens ofLeptophoca amphiatlanticaare consideredLeptophocacf.L. proxima. In a phylogenetic analysis,Prophoca rousseauiandLeptophoca proximaconstitute early branching stem-phocines.DiscussionLeptophoca proximafrom the North Sea Basin is younger than the oldest known find ofLeptophoca proximafrom North America, which does not contradict the hypothesis that Phocinae originated along the east coast of North America during the late early Miocene, followed by dispersal to Europe shortly after. Morphological features of the appendicular skeleton indicate thatProphoca rousseauiandLeptophoca proximahave archaic locomotory modes, retaining a more prominent use of the fore flipper for aquatic propulsion than extant Phocidae.

scholarly journals Reappraisal of the extinct seal “Phoca”vitulinoidesfrom the Neogene of the North Sea Basin, with bearing on its geological age, phylogenetic affinities, and locomotion

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3316 ◽  
Author(s):  
Leonard Dewaele ◽  
Eli Amson ◽  
Olivier Lambert ◽  
Stephen Louwye
Keyword(s):  
Phylogenetic Analysis ◽  
North Sea ◽  
Comparative Anatomy ◽  
Phylogenetic Position ◽  
The North ◽  
Early Diversification ◽  
Geological Age ◽  
The North Sea ◽  
Phylogenetic Affinities ◽  
Stratigraphic Range

BackgroundDiscovered on the southern margin of the North Sea Basin, “Phoca”vitulinoidesrepresents one of the best-known extinct species of Phocidae. However, little attention has been given to the species ever since its original 19th century description. Newly discovered material, including the most complete specimen of fossil Phocidae from the North Sea Basin, prompted the redescription of the species. Also, the type material of “Phoca”vitulinoidesis lost.Methods“Phoca”vitulinoidesis redescribed. Its phylogenetic position among Phocinae is assessed through phylogenetic analysis. Dinoflagellate cyst biostratigraphy is used to determine and reassess the geological age of the species. Myological descriptions of extant taxa are used to infer muscle attachments, and basic comparative anatomy of the gross morphology and biomechanics are applied to reconstruct locomotion.ResultsDetailed redescription of “Phoca”vitulinoidesindicates relatively little affinities with the genusPhoca, but rather asks for the establishment of a new genus:Nanophocagen. nov. Hence, “Phoca”vitulinoidesis recombined intoNanophoca vitulinoides. This reassignment is confirmed by the phylogenetic analysis, grouping the genusNanophocaand other extinct phocine taxa as stem phocines. Biostratigraphy and lithostratigraphy expand the known stratigraphic range ofN. vitulinoidesfrom the late Langhian to the late Serravallian. The osteological anatomy ofN. vitulinoidesindicates a relatively strong development of muscles used for fore flipper propulsion and increased flexibility for the hind flipper.DiscussionThe extended stratigraphic range ofN. vitulinoidesinto the middle Miocene confirms relatively early diversification of Phocinae in the North Atlantic. Morphological features on the fore- and hindlimb of the species point toward an increased use of the fore flipper and greater flexibility of the hind flipper as compared to extant Phocinae, clearly indicating less derived locomotor strategies in this Miocene phocine species. Estimations of the overall body size indicate thatN. vitulinoidesis much smaller thanPusa, the smallest extant genus of Phocinae (and Phocidae), and than most extinct phocines.

Capitalizing on the Talents of Retirees

2007 ◽  
Vol 01 (02) ◽  
pp. 19-20
Author(s):  
Deborah Stockwell
Keyword(s):  
North America ◽  
North Sea ◽  
Early Retirement ◽  
Oil Industry ◽  
The North ◽  
The North Sea ◽  
Personnel Shortages ◽  
Retention Policies

HR Perspective - The big crew change, which has been looming over the oil industry for years, is now upon us. The average age of offshore workers in the North Sea and North America is over 50. Cutbacks in recruitment, lack of active retention policies, early retirement, and streamlining measures all have played a part in causing chronic personnel shortages. The challenge now is, who will replace today's workforce?

Clay mineralogy of the Tertiary onshore and offshore strata of the British Isles

Clay Minerals ◽  
2006 ◽  
Vol 41 (1) ◽  
pp. 5-46 ◽  
Author(s):  
J. M. Huggett ◽  
R. W. O'B. Knox
Keyword(s):  
North Sea ◽  
Volcanic Ash ◽  
Middle Miocene ◽  
Clay Mineralogy ◽  
British Isles ◽  
Subsequent Increase ◽  
The North ◽  
Clay Deposits ◽  
The North Sea ◽  
Clay Formation

AbstractTertiary sediments are of restricted occurrence in the onshore British Isles but occur extensively offshore, attaining thicknesses of ~4 km in the Faroe—Shetland Basin and ~3 km in the North Sea Basin. Clay mineral stratigraphic studies of the North Sea Paleocene to Lower Miocene successions show a dominance of smectite (and smectite-rich illite-smectite) with minor illite, kaolin and chlorite. Abundant smectite in the Paleocene and Eocene reflects alteration of volcanic ash derived from pyroclastic activity associated with the opening of the North Atlantic between Greenland and Europe. However, the persistence of high smectite into the Oligocene and Middle Miocene indicates that smectite-rich soils on adjacent land areas may also have been an important source of detrital clays. An upwards change to illite-dominated assemblages in the Middle Miocene reflects higher rates of erosion and detrital clay supply, with a subsequent increase in chlorite reflecting climatic cooling. The persistence of smectite-rich assemblages to depths of >3000 m in the offshore indicates little burial-related diagenesis within the mudstone succession, possibly as a consequence of over-pressuring. Despite the importance of Paleocene and Eocene sandstones as hydrocarbon reservoirs in the North Sea and Faroe-Shetland basins, there are few published details of the authigenic clays. The principal clay cements in these sandstones are kaolin and chlorite, with only minor illite reported.The offshore successions provide a valuable background to the interpretation of the more intensively studied, but stratigraphically less complete, onshore Tertiary successions. The most extensive onshore successions occur in the London and Hampshire basins where sediments of Paleocene to earliest Oligocene age are preserved. Here clay assemblages are dominated by illite and smectite with subordinate kaolin and chlorite. The relatively large smectite content of these successions is also attributed primarily to the alteration of volcanic ash. Associated non-smectitic clays are largely detrital in origin and sourced from areas to the west, with reworking of laterites and “china clay” deposits developed over Cornish granites. Authigenic clays include glauconite (sensu lato), early diagenetic kaolin that has replaced muscovite (principally in the London Clay Formation of the London Basin) and smectite that has replaced ash. Pedogenesis has extensively modified the assemblages in the Reading Formation and Solent Group. Tertiary sediments are largely missing from onshore northern and western Britain, but clays and sands of Eocene and Oligocene age are locally preserved in small fault-bounded basins. Here, clay assemblages are dominated by kaolin with minor illite.

Shallow marine Lower and Middle Miocene deposits at the southern margin of the North Sea Basin (northern Belgium): dinoflagellate cyst biostratigraphy and depositional history

2000 ◽  
Vol 137 (4) ◽  
pp. 381-394 ◽  
Author(s):  
S. LOUWYE ◽  
J. DE CONINCK ◽  
J. VERNIERS
Keyword(s):  
North Sea ◽  
Depositional Environment ◽  
Middle Miocene ◽  
Depositional History ◽  
Shallow Marine ◽  
Dinoflagellate Cyst ◽  
Southern North Sea ◽  
The North ◽  
Southern Margin ◽  
The North Sea

Detailed dinoflagellate cyst analysis of the Lower–Middle Miocene Berchem Formation at the southernmost margin of the North Sea Basin (northern Belgium) allowed a precise biostratigraphical positioning and a reconstruction of the depositional history. The two lower members of the formation (Edegem Sands and decalcified Kiel Sands) are biostratigraphically regarded as one unit since no significant break within the dinocyst assemblages is observed. The base of this late (or latest) Aquitanian–Burdigalian unit coincides with sequence boundary Aq3/Bur1 as defined by Hardenbol and others, in work published in 1998. A hiatus at the Lower–Middle Miocene transition separates the upper member (the Antwerpen Sands) from the underlying member. The greater part of the Antwerpen Sands were deposited in a Langhian (latest Burdigalian?)–middle Serravallian interval. The base of this unit coincides with sequence boundary Bur5/Lan1. Biostratigraphical correlation points to a diachronous post-depositional decalcification within the formation since parts of the decalcified Kiel Sands can be correlated with parts of the calcareous fossil-bearing section, up to now interpreted as Antwerpen Sands. The dinoflagellate cyst assemblages are dominated by species with a inner neritic preference, although higher numbers of oceanic taxa in the upper part of the formation indicate incursions of oceanic watermasses into the confined depositional environment of the southern North Sea Basin.

scholarly journals Resolving a 200-year-old taxonomic conundrum: neotype designation for Cephalothrix linearis (Nemertea: Palaeonemertea) based on a topotype from Bergen, Norway

2019 ◽  
Vol 39 ◽  
pp. 39-76 ◽  
Author(s):  
Hiroshi Kajihara
Keyword(s):  
Type Species ◽  
Original Description ◽  
Zoological Nomenclature ◽  
Valid Species ◽  
Phylogenetic Position ◽  
Nominal Species ◽  
28S Rrna ◽  
Original Material ◽  
The North ◽  
The North Sea

The taxonomic identity of the palaeonemertean Cephalothrix linearis (Rathke, 1799) has been obscure for nearly two centuries, because its original description applies to almost any congeners, including Cephalothrix filiformis (Johnston 1828) and Cephalothrix rufifrons (Johnston, 1837), which occur commonly in the North Sea and adjacent waters. In this paper, I redescribe C. linearis based on two topotypes from Bergen, one herein designated as the neotype for C. linearis, because Rathke’s original material is not extant; I invoke Article 70.3.2 of the International Code of Zoological Nomenclature to fix Planaria linearis Rathke, 1799 as the type species of Cephalothrix Örsted, 1843 for the sake of stability. From the neotype, I determined sequences of the 28S rRNA, 16S rRNA, and cytochrome c oxidase subunit I (COI) genes. Using the COI sequence, I inferred the phylogenetic position of C. linearis along with 316 cephalotrichid sequences currently available in public databases. A tree-based species delimitation analysis detected 43 entities among them, with 34 in Cephalothrix and nine in eitherBalionemertes or Cephalotrichella. I apply valid species names to 12 of the 34 entities in Cephalothrix. I tabulated a total of 36 nominal species that are likely the members of the genus; the following five were excluded even though their specific names were originally combined with Cephalothrix: Cephalothrix armata Ulyanin, 1870 [Monostilifera, possibly Emplectonema gracile (Johnston, 1837)], Cephalothrix fragilis Bürger, 1892 [now Cephalotrichella signata (Hubrecht, 1879)], Cephalothrix signata Hubrecht, 1879 [now in Cephalotrichella], Cephalothrix unipunctata Parfitt, 1867 [now Tetrastemma melanocephalum (Johnston, 1837) (Monostilifera)], and Cephalothrix viridis Chapuis, 1886 [possibly Heteronemertea]. The five names cephalothrix Diesing, 1850 (as Borlasia cephalothrix), kroyeri Diesing, 1850 (as Cephalothrix kroyeri), linearis Diesing, 1850 (as Borlasia linearis), lineata Claparède, 1862 (as Cephalothrix lineata), and oerstedii Diesing, 1850 (as Cephalothrix oerstedii) aredeclared nomenclaturally unavailable.

scholarly journals We shall meet again - Genomics of historical admixture in the sea

2020 ◽  
Author(s):  
Xueyun Feng ◽  
Juha Merilä ◽  
Ari Löytynoja
Keyword(s):  
Local Adaptation ◽  
Source Population ◽  
Genetic Introgression ◽  
Genome Data ◽  
The North ◽  
Standing Variation ◽  
Genomic Landscape ◽  
The North Sea ◽  
Phylogenetic Affinities ◽  
The Impact

AbstractWe studied the impact of genetic introgression in evolution and on evolutionary studies with whole-genome data from two divergent lineages of sticklebacks. Our results reveal that the hybrid zone between the lineages ranges across the entire Baltic Sea and parts of the North Sea with the foreign ancestry decreasing with increasing distance to the source population. Introgression has also penetrated currently isolated freshwater populations. We identified footprints of selection on regions enriched for introgressed variants, suggesting that some of the introgression has been adaptive. However, the levels of introgression were in general negatively correlated with the recombination rate, suggesting that the introgression has been largely neutral and adaptive ancestral standing variation likely had a more important role in shaping the genomic landscape. Our results further suggest that overlooked introgression can mislead analyses of local adaptation and phylogenetic affinities, highlighting the importance of accounting for introgression in studies of local adaptation.

scholarly journals New Paleocene bird fossils from the North Sea Basin in Belgium and France

2019 ◽  
Vol 22 (1-2) ◽  
pp. 35-46 ◽  
Author(s):  
Gerald MAYR ◽  
Thierry SMITH
Keyword(s):  
North America ◽  
North Sea ◽  
Early Eocene ◽  
Fossil Assemblage ◽  
The North ◽  
The North Sea ◽  
Dispersal Events ◽  
Early Cenozoic

We describe new avian remains from Paleocene localities of Belgium and France. Four bones from the early to middle Selandian of Maret (Belgium) are among the earliest Cenozoic avian remains known from Europe and include the oldest temporally well constrained European records of the Gastornithidae, as well as tentative records of the palaeognathous Lithornithidae and the Ralloidea. A more comprehensive fossil assemblage from the middle Thanetian of Templeuve (France) contains multiple bones of the Lithornithidae as well as a record of the Pelagornithidae. Specimens from the latest Thanetian of Rivecourt-Petit Pâtis (France) are tentatively assigned to the Ralloidea and Leptosomiformes (cf. Plesiocathartes). Because of the fragmentary nature of the fossils, the taxonomic identity of a number of other specimens remains uncertain. We note, however, that Paleocene avifaunas of Europe and North America appear to have had different compositions and only a few taxa, such as the palaeognathous Lithornithidae, are known from both continents. This suggests that the very similar early Eocene avifaunas of Europe and North America are the result of early Cenozoic dispersal events.

Middle Miocene through Pliocene North American Vegetational History: 16.3-1.6 Ma

1999 ◽  
Author(s):  
Alan Graham
Keyword(s):  
North America ◽  
Sierra Nevada ◽  
North American ◽  
Middle Miocene ◽  
Middle Eocene ◽  
Alaska Range ◽  
Seasonally Dry ◽  
Middle Latitudes ◽  
The North ◽  
Dry Climates

During the Middle Miocene through the Pliocene the Appalachian Mountains underwent continued erosion and approached modern elevations. The Rocky Mountains had undergone uplift to half or more of their present elevation during the Late Cretaceous to Middle Eocene Laramide Revolution; after a lull during the Middle Eocene through the Early Miocene, there was increased tectonic activity beginning ~12 Ma and especially between 7 and 4 Ma. Locally some highlands may have approached or attained modern elevations. The increasingly high mountains and plateaus of Asia and North America deflected the major air streams southward, bringing colder polar air into the middle latitudes of North America. An extensive Antarctic ice sheet further cooled ocean waters and contributed to the spread of seasonally dry climates. The elimination of most of the Asian exotics from the North American flora dates to the Late Miocene-Pliocene as a result of a decline in summer rainfall. The Sierra Nevada attained about two-thirds of their present elevation within the past 10 Ma. They were appreciably elevated at ~5 Ma, stood at ~2100 m at 3 Ma, and have risen ~950 m since 3 Ma (Huber, 1981). The California Coast Ranges and Cascade Mountains attained significant heights by 3 Ma, and there was a rapid rise of the Alaska Range at ~6 Ma. Temperatures increased between ~18 and 16 Ma. In the absence of major plate reorganization and intense volcanic activity and with increased erosion from continued replacement of the dense evergreen forest by deciduous forest and shrubland (increasing albedo), atmospheric CO2 concentration decreased and a sharp lowering of temperature occurred in the Middle Miocene between 15 and 10 Ma. Eolian dust deposits increased in the Late Cenozoic, suggesting greater aridity (Rea et al., 1985). This is supported by kaolinite records from North Atlantic deep sea sediments (Chamley, 1979). At ~4.8~4.9 Ma global cooling and a marine regression of ~40~50 m combined to isolate the Mediterranean Basin from the ocean and to concentrate large volumes of salt as water evaporated. The biota was destroyed, giving rise to the term Messinian salinity crisis.

On the presence of North American clubmoss Huperzia lucidula (Lycopodiaceae) in China: An intercontinental disjunction or misidentification

Phytotaxa ◽  
2015 ◽  
Vol 219 (3) ◽  
pp. 243 ◽  
Author(s):  
Nawal Shrestha ◽  
Xian-Chun Zhang
Keyword(s):  
North America ◽  
American Literature ◽  
North American ◽  
Chinese Literature ◽  
Intergenic Spacer ◽  
Molecular Study ◽  
New Combination ◽  
Disjunct Distribution ◽  
Separate Species ◽  
The North

The North American shining clubmoss, Huperzia lucidula, was originally thought to be endemic to North America. However it was reported from China by Ren Chang Ching in 1981, and hence was believed to have a disjunct distribution in North America and Asia. Since then, in all Chinese literature H. lucidula has been described as a disjunct taxon, although in North American literature it has nearly always only been reported from eastern North America. The studies on the Chinese taxon are at present insufficient to address this taxonomical and biogeographical disparity. In this study we have attempted to unravel this issue using integrative morphological and molecular analyses. Morphological study included a thorough examination of specimens from the entire distribution range of H. lucidula in the USA, Canada and China following field collections. Molecular study included Maximum Likelihood and Bayesian inference phylogenetical analyses of three chloroplast markers: the genes rbcL and matK and the psbA-trnH intergenic spacer. The results showed distinct morphological differences between the North American and Chinese taxa, sufficient to recognize them as separate species. The molecular results corroborated these findings and supported the separation of the two taxa. Based on our results, the Chinese taxon is neither a variant of H. lucidula nor sister to it and therefore the supposed disjunct distribution of H. lucidula is erroneous and a result of misidentification. The Chinese taxon that was firstly reported by Ching as H. lucidula var. asiatica has been elevated to the species rank and a new combination has been made.

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