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Wyszukujesz frazę "graptolite" wg kryterium: Temat


Wyświetlanie 1-5 z 5
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
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:
New and unusual upper Llandovery graptolites from Arctic Canada
Autorzy:
Lenz, A C
Kozlowska, A.
Powiązania:
https://bibliotekanauki.pl/articles/20163.pdf
Data publikacji:
2007
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
graptolite
Mirorgraptus arcticus
Silurian
Llandovery
skeleton
morphology
Arctic Canada
Pseudoplegmatograptus cf.obesus
stratigraphy
systematics
Giganteograptus giganteus
biostratigraphy
paleontology
Graptoloidea
Pileograptus pileatus
Opis:
Three isolated and well−preserved retiolitid taxa, two of them new, and one taxon of unknown affinity, are described from the upper Llandovery of Arctic Canada. All taxa display unusual characteristics The three retiolitids display extraordinary morphological features: Pseudoplegmatograptus cf. obesus preserves very delicate and lacey or cobweb−like list structures external to the main skeletal lists, structures previously seen only rarely on flattened material; Pileograptus pileatus gen. et sp. nov. possesses a thecal framework typical of retiolitines, particularly Stomatograptus, but its thecal orifices possess broad, meshwork genicular hoods similar to those in the plectograptines; and Giganteograptus giganteus, formerly attributed to Pseudoplegmatograptus, with its very coarse and relatively simple skeletal framework, well−developed paired thecal apertural spines, and a pustulose micro−ornamentation on the lists. The latter feature suggests an assignment to the subfamily Plectograptinae, rather than to the Retiolitinae as has been previously presumed. The presence of pustulose lists in Giganteograptus adds a further complication to understanding of retiolitid evolution. Mirorgraptus arcticus gen. et sp. nov., the fourth taxon and of unknown systematic affinity, lacks the proximal end, but preserves lists with seams and some fusellar material suggestive of some type of new retiolitid. Unlike known retiolitids or other graptolites, however, the skeletal list development is apparently confined to a narrow region along one side of the nema.
Źródło:
Acta Palaeontologica Polonica; 2007, 52, 3
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phyletic evolution and iterative speciation in the persistent Pristiograptus dubius lineage
Autorzy:
Urbanek, A.
Radzevicius, S.
Kozlowska, A.
Teller, L.
Powiązania:
https://bibliotekanauki.pl/articles/22649.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
phyletic zob.phylogenetic
phylogenetic evolution
iterative speciation
Pristiograptus dubius
lineage
graptolite
Graptolithina
stem lineage
new subspecies
Pristiograptus dubius magnus
Pristiograptus dubius paezerensis
Pristiograptus dubius praelodenicensis
Pristiograptus dubius postfrequens
Pristiograptus dubius postmagnus
Silurian
East European Platform
Polska
Lithuania
Opis:
The paper focuses on patterns of the evolution of the simplest and longest−ranging (approximately 18 Ma) Silurian graptolite Pristiograptus dubius. The Pristiograptus dubius species group consists of the P. dubius stem lineage represented by a sequence of a number of subspecies displaying only small morphological changes as well as derivative species produced from the stem lineage by means of iterative speciation. This long raging graptolite lineage is the only one, apart of one retiolitid, which survived the most severe environmental event for graptolites, the Cyrtograptus lundgreni Event. Based on three−dimensional, isolated material two P. dubius groups taxa are distinguished. One group has an obtuse angle between the thecal lip and the succeeding thecal wall, the second group has a right or acute angle. Other characters differentiating P. dubius forms are: the shape of the apertural lips, differences in rhabdosome shape and size, and a different number of sicular rings. Sixteen species and subspecies of Pristiograptus from the East European Platform, Poland and Lithuania are discussed. Five new subspecies P. dubius magnus, P. dubius paezerensis, P. dubius praelodenicensis, P. dubius postfrequens, and P. dubius postmagnus are proposed.
Źródło:
Acta Palaeontologica Polonica; 2012, 57, 3
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-5 z 5

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