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Tytuł:
Mat-forming coccoid cyanobacteria from Early Silurian marine deposits of Sudetes, Poland
Autorzy:
Kremer, B
Powiązania:
https://bibliotekanauki.pl/articles/22597.pdf
Data publikacji:
2006
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
organic matter
marine environment
Cyanoprokaryota
Early Silurian
nitrogen fixation
marine deposit
Polska
Silurian
remains
coccoid cyanobacteria
Sudetes Mountains
paleontology
Opis:
Mass occurrence of mats comprised of benthic coccoid cyanobacteria is reported from early Silurian black radiolarian cherts exposed at Żdanow village (Bardzkie Mountains, Sudetes, southwestern Poland). The cherts contain laminated organic matter representing degraded benthic coccoid cyanobacterial mats. The remains of cyanobacteria occur as laminated agglomerations of variously preserved subglobular colonies composed of spherical cells of variable size and numbers. The morphology of remnants of cells and their mucilaginous envelopes, structure of colonies, and particularly the presence of small granular structures resembling reproductive cells known in extant coccoid cyanobacteria as baeocytes, permit to compare the Silurian microbiota with modern cyanobacteria assigned to the genera Stanieria or Chroococcidiopsis.
Źródło:
Acta Palaeontologica Polonica; 2006, 51, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On generation and regeneration of cladia in some Upper Silurian monograptids
O rozwoju i regeneracji gałązek w koloniach pewnych górno-sylurskich Monograptidae
O razvitii i regenereracii vetok v kolonijakh verkhne-silurijjskikh Monograptidae
Autorzy:
Urbanek, A.
Powiązania:
https://bibliotekanauki.pl/articles/23490.pdf
Data publikacji:
1963
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
generation
regeneration
Upper Silurian
monograptid
Linograptinae
structure
development
paleontology
Źródło:
Acta Palaeontologica Polonica; 1963, 08, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Agastograptus, a synonym of Plectograptus [Retiolitidae, Graptolithina]
Autorzy:
Kozlowska-Dawidziuk, A
Powiązania:
https://bibliotekanauki.pl/articles/22767.pdf
Data publikacji:
2002
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Agastograptus robustus
synonym
Retiolitidae
Graptolithina
Silurian
Agastograptus
taxonomy
Plectograptus
paleontology
Opis:
Agastograptus robustus Obut and Zaslavskaya, 1983, the type species of the genus Agastograptusis herein recognized as a species of Plectograptus. Large proximal lateral orifices are one of the significant characters of Plectograptus. P. robustus differs from the type species, Plectograptus macilentus Törnquist, 1887, in possessing paired apertural processes. Other species of Agastograptus have been assigned to three different genera: Spinograptus, S. clathrospinosus (Eisenack, 1951), S. munchi (Eisenack, 1951), Neogothograptus, N. balticus (Eisenack, 1951), and Cometograptus, C. nevadensis (Berry and Murphy, 1975). The main diagnostic feature used for Agastograptus, the spinoreticular paired apertural processes, is recognized as a species feature, characteristic mostly for Spinograptus, whereas the generic features are the arrangement of the proximal end, ventral walls, and ancora sleeve of the rhabdosome. Therefore the genus Agastograptus is a synonym of Plectograptus.
Źródło:
Acta Palaeontologica Polonica; 2002, 47, 3
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Silurian thelodonts from the Niur Formation, central Iran
Autorzy:
Hairapetian, V
Blom, H.
Miller, C.G.
Powiązania:
https://bibliotekanauki.pl/articles/20388.pdf
Data publikacji:
2008
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
thelodont
Loganelliiformes
paleontology
Silurian
Phlebolepidiformes
paleobiogeography
Thelodonti
Niur Formation
Iran
Opis:
Thelodont scales are described from the Silurian Niur Formation in the Derenjal Mountains, east central Iran. The material studied herein comes from four stratigraphic levels, composed of rocks formed in a shallow water, carbonate ramp environment. The fauna includes a new phlebolepidiform, Niurolepis susanae gen. et sp. nov. of late Wenlock/?early Ludlow age and a late Ludlow loganelliiform, Loganellia sp. cf. L. grossi, which constitute the first record of these thelodont groups from Gondwana. The phlebolepidiform Niurolepis susanae gen. et sp. nov. is diagnosed by having trident trunk scales with a raised medial crown area separated by two narrow spiny wings from the lateral crown areas; a katoporodidtype histological structure distinguished by a network of branched wide dentine canals. Other scales with a notch on a smooth rhomboidal crown and postero−laterally down−stepped lateral rims have many characters in common with Loganellia grossi. Associated with the thelodonts are indeterminable acanthodian scales and a possible dentigerous jaw bone fragment. This finding also provides evidence of a hitherto unknown southward dispersal of Loganellia to the shelves of peri−Gondwana.
Źródło:
Acta Palaeontologica Polonica; 2008, 53, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Diversity of tissues in acanthodians with Nostolepis-type histological structure
Autorzy:
Valiukevicius, J
Burrow, C.J.
Powiązania:
https://bibliotekanauki.pl/articles/22517.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
histology
acanthodian
dentine
Devonian
Acanthodii
Silurian
bone
Nostolepis
tissue
paleontology
mesodentine
Opis:
Acanthodian scales with Nostolepis−type histological structure are separated into five groups based on the presence/absence and extent of stranggewebe, odontocytic and syncitial mesodentine networks, cellular unipolar mesodentine, bone−like mesodentine and durodentine in scale crowns. Two new families of acanthodians are erected, based primarily on histological structure of scales: the Vesperaliidae (stranggewebe extending throughout the scale crown) and the Acritolepidae (bone−like mesodentine in the scale crown). The latter family includes species erected for articulated fish. The families Tchunacanthidae and Lenacanthidae are united in the single family Tchunacanthidae, characterized by having scale crowns with mesodentine formed mainly by unipolar cells. A sixth group, which we exclude from the Nostolepis−type, has scale crowns composed of dentine without lacunae, plus durodentine, and bases with only rare osteocyte cavities. The new groups promote the revision and reassignment of many “nostolepid” taxa, in particular removing many species from the genus Nostolepis. Four new genera are erected: Pechoralepis (including part of Nostolepis), assigned to Acritolepidae nov.; and three genera assigned to an indeterminate family, which scales are composed of only odontocytic mesodentine without stranggewebe: Nostovicina (including part of Nostolepis), Nobilesquama (including part of Nostolepis), and Peregrinosquama (including part of Watsonacanthus). Histological structures are considered the primary characters of taxonomical value when based on isolated scales. Unfortunately, scale histology is unknown for most articulated acanthodians.
Źródło:
Acta Palaeontologica Polonica; 2005, 50, 3
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The brachiopod succession through the Silurian–Devonian boundary beds at Dnistrove, Podolia, Ukraine
Autorzy:
Balinski, A.
Powiązania:
https://bibliotekanauki.pl/articles/23447.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
brachiopod
succession
Silurian
Devonian
boundary bed
Podolia
Ukraine
Brachiopoda
paleontology
paleoenvironment
Opis:
In the classic section across the Silurian–Devonian boundary at Dnistrove (Podolia, Ukraine) the brachiopod fauna has never been studied in detail. This paper presents results of research on brachiopods from this important locality and time interval. Bed−by−bed collecting has enabled the detailed distribution of brachiopod taxa through the boundary beds to be revealed. Generally, the reference section at Dnistrove yields rather scarce but often well preserved brachiopods. Dayia bohemica and Dnestrina gutta can be regarded as characteristic species for the uppermost Silurian. A relatively high−diversity but low−abundance brachiopod fauna occurs in the lowest 1.8 m of the earliest Devonian. Only three forms have been found to cross the Silurian–Devonian boundary: the strophomenide Plectodonta (Plectodonta) mariae pantherae subsp. nov., the atrypide Gracianella (Sublepida) paulula sp. nov., and the spiriferide Howellella (Howellella) latisinuata. A relatively narrow brachiopod−rich interval at 5.5 m above the Silurian–Devonian boundary yields 16 brachiopod species which probably indicate a setting near the lower limit of the photic zone equivalent to the Benthic Assemblage 3–4 boundary. Two new species and one new subspecies are described: Skenidioides tatyanae, Plectodonta (Plectodonta) mariae pantherae, and Gracianella (Sublepida) paulula.
Źródło:
Acta Palaeontologica Polonica; 2012, 57, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Palaeobiology, ecology, and distribution of stromatoporoid faunas in biostromes of the mid-Ludlow of Gotland, Sweden
Autorzy:
Sandstrom, O
Kershaw, S.
Powiązania:
https://bibliotekanauki.pl/articles/21659.pdf
Data publikacji:
2008
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
paleoecology
deposit
Sweden
paleontology
Silurian
morphotype
stromatoporoid fauna
ecology
distribution
Gotland
Opis:
Six well exposed mid−Ludlow stromatoporoid−dominated reef biostromes in four localities from the Hemse Group in southeastern Gotland, Sweden comprise a stromatoporoid assemblage dominated by four species; Clathrodictyon mohicanum, “Stromatopora” bekkeri, Plectostroma scaniense, and Lophiostroma schmidtii. All biostromes investigated in this area (of approximately 30 km²) are interpreted to belong to a single faunal assemblage forming a dense accumulation of fossils that is probably the best exposed stromatoporoid−rich deposit of the Silurian. The results from this comprehensive study strengthen earlier interpretations of a combination of genetic and environmental control on growth−forms of the stromatoporoids. Growth styles are similar for stromatoporoids in all six biostromes. Differences in biostrome fabric are due to variations in the degree of disturbance by storms. The uniformity of facies and the widespread low−diversity fauna support the view that palaeoenvironmental conditions were similar across the area where these biostromes crop out, and promoted the extraordinary growth of stromatoporoids in this shallow shelf area.
Źródło:
Acta Palaeontologica Polonica; 2008, 53, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new type of colony in Silurian (upper Wenlock) retiolitid graptolite Spinograptus from Poland
Autorzy:
Kozlowska, A.
Dobrowolska, K.
Bates, D.E.B.
Powiązania:
https://bibliotekanauki.pl/articles/22266.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
new type
colony
Silurian
retiolitid graptolite
Spinograptus
Graptoloidea
Retiolitidae
Polska
paleontology
Opis:
The new retiolitid species, Spinograptus tubothecalis, is described from the Colonograptus praedeubeli and C. deubeli biozones from two localities in Poland: a borehole on the East European Platform and the Holy Cross Mountains. This was a recovery phase after the severe Silurian Cyrtograptus lundgreni Event. The new species has a unique, previously undescribed form of finite rhabdosome. Unlike the species Spinograptus reticulolawsoni and S. lawsoni, in which the fi− nite rhabdosomes taper distally, its rhabdosome is parallel−sided with the two distal thecae developed as isolated tubes without genicular processes, with a small appendix between them. The new species also has preserved membranes of the sicula, thecae and ancora sleeve, similar to a few species of Spinograptus from the lower Homerian. Spinograptus tubothecalis, like Spinograptus clathrospinosus and S. spinosus, has paired reticulofusellar genicular processes on the pre−thecal ventral orifices, similar to but shorter than thecal processes. Transverse rods, a rare character in post−Cyrto− graptus lundgreni Event retiolitids occur in the new species in rudimentary form.
Źródło:
Acta Palaeontologica Polonica; 2013, 58, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Concentrations of Silurian nautiloid cephalopods from Russia and Kazakhstan
Autorzy:
Bogolepova, O K
Holland, C H
Powiązania:
https://bibliotekanauki.pl/articles/22316.pdf
Data publikacji:
1995
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Cephalopoda
cephalopod
Silurian
concentration
Russia
living population
Kazakhstan
paleontology
nautiloid cephalopod
Opis:
Silurian cephalopod limestones known from northern Asia are usually singular beds or horizons of nodules. They range in their taphonomic character from the Mojero river type, with postmortem concentration from rich living populations by relatively gentle bottom currents into a submarine low, to that of the Karabutak Formation of the South Urals, where there has been concentration by strong wave or current action.
Źródło:
Acta Palaeontologica Polonica; 1995, 40, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Strophomenide and orthotetide Silurian brachiopods from the Baltic Region, with particular reference to Lithuanian boreholes
Autorzy:
Musteikis, P
Cocks, L.R.M.
Powiązania:
https://bibliotekanauki.pl/articles/22973.pdf
Data publikacji:
2004
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Strophomenoidea
brachiopod
Plectambonitoidea
Silurian
Orthotetoidea
Lithuania
Baltic region
Brachiopoda
paleontology
borehole
Opis:
Epeiric seas covered the east and west parts of the old craton of Baltica in the Silurian and brachiopods formed a major part of the benthic macrofauna throughout Silurian times (Llandovery to Pridoli). The orders Strophomenida and Orthotetida are conspicuous components of the brachiopod fauna, and thus the genera and species of the superfamilies Plectambonitoidea, Strophomenoidea, and Chilidiopsoidea, which occur in the Silurian of Baltica are reviewed and reidentified in turn, and their individual distributions are assessed within the numerous boreholes of the East Baltic, particularly Lithuania, and attributed to benthic assemblages. The commonest plectambonitoids are Eoplectodonta (Eoplectodonta) (6 species), Leangella (2 species), and Jonesea (2 species); rarer forms include Aegiria and Eoplectodonta (Ygerodiscus), for which the new species E. (Y.) bella is erected from the Lithuanian Wenlock. Eight strophomenoid families occur; the rare Leptaenoideidae only in Gotland (Leptaenoidea, Liljevallia). Strophomenidae are represented by Katastrophomena (4 species), and Pentlandina (2 species); Bellimurina (Cyphomenoidea) is only from Oslo and Gotland. Rafinesquinidae include widespread Leptaena (at least 11 species) and Lepidoleptaena (2 species) with Scamnomena and Crassitestella known only from Gotland and Oslo. In the Amphistrophiidae Amphistrophia is widespread, and Eoamphistrophia, Eocymostrophia, and Mesodouvillina are rare. In the Leptostrophiidae Mesoleptostrophia, Brachyprion, and Protomegastrophia are common, but Eomegastrophia, Eostropheodonta, Erinostrophia, and Palaeoleptostrophia are only recorded from the west in the Baltica Silurian. In the Eopholidostrophidae, Mesopholidostrophia is common and Eopholidostrophia rare, and within the Shaleriidae the genus Shaleria is revised and found to be the only genus within the family Shaleriidae and to contain three subgenera, S. (Shaleria), S. (Shaleriella) and S. (Janiomya). In the Strophonellidae Strophonella was widespread and Eostrophonella rare. Within the Orthotetoidea, Coolinia and Morinorhynchus(with the new Ludlow and Pridoli species M. rubeli from the Lithuanian boreholes erected) are common, and Fardenia, Saughina, and Valdaria again only known from the west Baltic. Most of the genera and many of the speciesreviewed were very widespread and many found in the adjacent Avalonia and Laurentia: a few were even more cosmopolitan.
Źródło:
Acta Palaeontologica Polonica; 2004, 49, 3
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Evolution of retiolitid graptolites - a synopsis
Autorzy:
Kozlowska-Dawidziuk, A
Powiązania:
https://bibliotekanauki.pl/articles/23196.pdf
Data publikacji:
2004
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Holoretiolites
Ludlow
Retiolitidae
retiolitid graptolite
paleobiology
Silurian
evolution
Graptoloidea
paleontology
rhabdosome reduction
Opis:
Twenty million years of retiolitid evolution reflect environmental changes, the most severe being the Silurian Cyrtograptus lundgreni Event. Five biostratigraphically and morphologically constrained retiolitid faunas are distinguished and characterized according to their rhabdosomal modifications: (1) the oldest and long−ranging Llandovery group of mostly large and morphologically complex rhabdosomes, (2) the less diverse Telychian−Sheinwoodian group, (3) the Cyrtograptus lundgreni Biozone varied group of intermediate size, and two short−ranged (4) late Homerian, and (5) early Ludlow groups with small rhabdosomes. Although the evolutionary history of retiolitids was complex and not linear, a common tendency toward reduction of rhabdosome size in most lineages is observed. The greatest reduction in both number and volume of thecae, and in skeletal elements is demonstrated in the Gothograptus and Plectograptusfaunas. Contrary to the thecal decrease, a distinctive increase of sicula size is observed in retiolitids. Two types of colonies are distinguished: L−colonies with a small sicula and numerous large thecae of similar size, and S−colonies with a long sicula and a few, small thecae. These changes imply modification of the soft body: an increase in siculozooid length and a decrease in the size of the zooids. Thus, the siculozooid probably produced great amounts of morphogen inhibiting zooid growth. In consequence the phenomenon of colony reduction occurred. The most extreme stages of rhabdosome reduction in Ludlow retiolitids can be seen in Plectodinemagraptus gracilis of the Plectograptuslineage and in the new species Holoretiolites helenaewitoldi, possibly representing the last stage of skeletal reduction in the Gothograptus lineage; the next hypothetical stage would be its total loss. The sicula length of Holoretiolites, about 2 mm, is reported herein for the first time.
Źródło:
Acta Palaeontologica Polonica; 2004, 49, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Silurian synziphosurine horseshoe crab Pasternakevia revisited
Autorzy:
Krzeminski, W.
Krzeminska, E.
Wojciechowski, D.
Powiązania:
https://bibliotekanauki.pl/articles/20993.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Silurian
horseshoe crab
arthropod
Pasternakevia
paleontology
Arthropoda
Xiphosura
Bunodidae
phylogenesis
Ukraine
stratigraphy
Opis:
The synziphosurine horseshoe crab Pasternakevia was until now known only from a single specimen. Herein we describe three new specimens from the outcrop close to the type locality of monotypic P. podolica that show several features that were unknown or only assumed in this genus. These characters include: a smooth surface of the carapace; an opisthosoma composed of ten segments, the first one being a microtergite (strongly reduced first opisthosomal segment usually hidden under the carapace), two or three last segments fused into a metasoma, and the telson. Pasternakevia is included in Bunodidae due to a hypertrophied tergite 2, but it is linked to the Pseudoniscidae by the shape of the opisthosoma.
Źródło:
Acta Palaeontologica Polonica; 2010, 55, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Minute Silurian oncocerid nautiloids with unusual colour patterns
Autorzy:
Manda, S
Turek, V.
Powiązania:
https://bibliotekanauki.pl/articles/22242.pdf
Data publikacji:
2009
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Silurian
paleontology
oncocerid nautiloid
nautiloid
colour pattern
Cephalopoda
Nautiloidea
taxonomy
shell size
shell malformation
Opis:
A minute Silurian oncocerid Cyrtoceras pollux, from the Prague Basin is assigned here to the genus Pomerantsoceras. The only so far known species of this genus comes from the Upper Ordovician (Hirnantian) of Estonia. Pomerantsoceras thus represents, except for un−revised poorly understood taxa, the single known oncocerid genus surviving the end−Ordovician extinction events. Cyrtoceras pollux is unusual among the Silurian nautiloids because of its small shell. Colour pattern characterised by a few longitudinal bands on the entire circumference of the shell is here reported in oncocerids. Longicone and only slightly curved small shells as in Pomerantsoceras are unusual among nautiloids and resemble straight shells of orthocerids and pseudorthocerids, in which the colour pattern consists of straight colour bands. Consequently the shell shape as well as the colour pattern should be regarded as adaptive convergence with orthocerids and pseudorthocerids. It supports the hypothesis that colour pattern functioned as camouflage and its evolution was under adaptive control. In addition, several types of the shell malformations including anomalous growth of septa, shell wall and pits on an internal mould are described.
Źródło:
Acta Palaeontologica Polonica; 2009, 54, 3; 503-512
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An atypical Silurian myodocope ostracod from the Armorican Massif, France
Autorzy:
Perrier, V.
Powiązania:
https://bibliotekanauki.pl/articles/22621.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Silurian
paleontology
myodocope ostracod
ostracod
Armorican Massif
France
Arthropoda
Crustacea
Ostracoda
Myodocopa
Entomozoidae
taxonomy
Opis:
A new myodocope ostracod Sineruga insolita gen. et sp. nov. is herein described from the Armorican Massif (France). Sineruga resembles Silurian myodocopes (i.e., bolbozoids and cypridinids) in having anterior features (thinner carapace) possibly related to vision. On the other hand, it resembles entomozoid ostracods in having a bean−shaped outline along with a deep adductorial sulcus and a simple muscle spot, but lacks their characteristic ribbed ornament. The data available suggest that Sineruga insolita was probably an atypical, non−ribbed member of the entomozoids thus indicating that early entomozoids may have had smooth representatives. Comparisons with other Recent and fossils ostracods show that the presence of a rostrum and/or symmetrical vision related carapace features (i.e., indicating lateral eyes) can be used as diagnostic characters for myodocope ostracods. The position and shape of the dorsal connection and to a lesser extent that of the sulcus and the adductorial muscle scar can be used to discriminate the higher groups of Silurian myodocopes (bolbozoids, cypridinids, and entomozoids).
Źródło:
Acta Palaeontologica Polonica; 2012, 57, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Silurian retiolitid graptolite Plectograptus: New observations and new species
Autorzy:
Bates, D.E.B.
Kozlowska, A.
Maletz, J.
Kirk, N.H.
Lenz, A.
Powiązania:
https://bibliotekanauki.pl/articles/20525.pdf
Data publikacji:
2006
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Graptoloidea
Plectograptus
Retiolitidae
rhabdosome
Silurian
graptolite
new species
paleontology
retiolitid graptolite
Ludlow
morphology
terminology
systematics
Opis:
The Ludlow genus Plectograptus, with the type species Retiolites macilentus Törnquist, 1887, collected from Thuringia (Germany), has been a widely−identified, monospecific, but poorly understood taxon for almost one hundred years. This was due to poor and incomplete preservation of the type material, and misidentification by subsequent authors up to 1995. The original, and only, type specimen of P. macilentus collected by Törnquist being lost, a neotype is herein selected from a small collection of Thuringian material. The genus has now been redefined and based on this, and SEM studies of isolated material, the defining characteristics of the genus are (i) the possession of a simple ancora umbrella with five radial lists with an incompletely developed rim; (ii) an ancora umbrella separated from lateral ancora sleeve walls by exceptionally large lateral orifices; (iii) the possession of mid−ventral lists; (iv) simple, orderly zigzag lateral wall ancora sleeve lists. Recently, two additional species, P. robustus and P. wimani, previously placed in different genera, were assigned to Plectograptus. This study recognizes three new species: P. mobergi, P. toernquisti, and P. trijunctus, bringing the total number of species to six. Species are distinguished by the presence or absence of genicular processes, inclination of the thecal ventral walls and mid−ventral lists, presence or absence of reticular lists, and three−way or four−way sleeve/lateral rod/apertural lip junctions.
Źródło:
Acta Palaeontologica Polonica; 2006, 51, 3
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 22

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