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Tytuł:
The earliest known Kinnella, an orthide brachiopod from the Upper Ordovician of Manitoulin Island, Ontario, Canada
Autorzy:
Stott, C A
Jin, J.
Powiązania:
https://bibliotekanauki.pl/articles/23034.pdf
Data publikacji:
2007
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Kinnella laurentiana
Manitoulin Island
brachiopod
Canada
Orthida
Ordovician
Upper Ordovician
Ontario
Brachiopoda
paleontology
Enteletoidea
Opis:
A new species of the orthide brachiopod genus Kinnella is described from the Upper Member of the Georgian Bay Formation (Upper Ordovician) of Manitoulin Island, Ontario, Canada. This species, herein designated as Kinnella laurentiana sp. nov., occurs in strata of Richmondian (mid−Ashgill; Katian) age, most likely correlative with the eastern North American Dicellograptus complanatus Zone. This occurrence extends the known stratigraphic range of Kinnella downward considerably from its previously inferred basal Hirnantian inception. The new species is characterized by a moderately convex dorsal valve and an apsacline ventral interarea rarely approaching catacline. This is the third reported occurrence of Kinnella in North America, and is the only species known to have inhabited the epicontinental seas of Laurentia. The associated benthic shelly fauna indicates a depositional environment within fair weather wave base (BA 2). The ancestry of Kinnella and this species appears most likely to lie among older, morphologically similar members of the Draboviidae which were seemingly confined to higher latitude faunal provinces prior to the Hirnantian glacial event. Thus, the mid−Ashgill occurrence of Kinnella laurentiana in the palaeotropically located Manitoulin Island region suggests the mixing of a probable cooler water taxon with the warmer water epicontinental shelly fauna of Laurentia, as well as a possible earlier episode of low−latitude oceanic cooling. Cluster analysis of Kinnella−bearing brachiopod faunas reveals a sharp differentiation between the K. laurentiana−associated brachiopod fauna and all other known (Hirnantian–lower Rhuddanian) occurrences mainly represented by the type species K. kielanae.
Źródło:
Acta Palaeontologica Polonica; 2007, 52, 3
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Palaeoecological significance of coral-encrusting foraminiferan associations: a case-study from the Upper Eocene of Northern Italy
Autorzy:
Bosellini, F R
Papazzoni, C.A.
Powiązania:
https://bibliotekanauki.pl/articles/22069.pdf
Data publikacji:
2003
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Eocene
Italy
reef
encrusting foraminiferan
Upper Eocene
paleoecology
coral
foraminiferal fossil
paleontology
Opis:
Encrusting foraminiferans, although representing an important component of the so−called cryptic assemblages in both modern and ancient reef environments, are in general poorly described and little is known as regards their association with corals.In this paper, we describe coral−encrusting foraminiferan associations in the different facies that characterize the shallowing upward parasequences of the Nago Limestone (Upper Eocene, Trentino, northern Italy).From a relatively deep reef slope up to the shallow shelf−edge, corals have been recognized to be encrusted by different types of foraminiferan assemblages that differ on the basis of relative abundance of species, growth form and type of encrusted coral surface.The succession of encrusting foraminiferan assemblages is interpreted as controlled mainly by light, competition with coralline algae, hydrodynamic energy, and coral growth fabric.
Źródło:
Acta Palaeontologica Polonica; 2003, 48, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pneumaticity and soft-tissue reconstructions in the neck of diplodocid and dicraeosaurid sauropods
Autorzy:
Schwarz, D
Frey, E.
Meyer, C.A.
Powiązania:
https://bibliotekanauki.pl/articles/22875.pdf
Data publikacji:
2007
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Dicraeosauridae
pneumaticity
cervical ligament
morphology
dicraeosaurid sauropod
diplodocid sauropod
sauropod
Diplodocidae
body length
muscle
ontogenesis
tomography
soft tissue reconstruction
cervical musculature
vertebral pneumaticity
paleontology
functional morphology
Opis:
The axial soft−tissue system in the neck of Dicraeosauridae and Diplodocidae, including pneumatic diverticula, ligaments, and muscles, is reconstructed on the basis of phylogenetic and functional morphological comparisons with extant crocodylians and birds and compared with other soft−tissue reconstructions for sauropods. Bifurcation of the neural spines separated the paired supraspinal ligament into two sheets. A paired interspinal septum was attached to the cranial and caudal margins of the neural spines. The dorsal and the lateral portions of the cervical musculature must have been strongly segmented, whereas the laterocostal portion was divided with one myoseptum per vertebral segment. The hypaxial cervical muscle was most probably small and only poorly segmented. In Diplodocidae and Dicraeosauridae, the distribution of external pneumatic structures is similar, whereas only Diplodocidae possess intraosseous pneumatic structures. Supravertebral pneumatic diverticula are reconstructed for both groups, which, together with dorsal ligaments filled the gap between the metapophyses of bifurcate neural spines. Comparisons between the vertebrae of juvenile and adult diplodocids strongly indicate that pneumatisation proceeded from the supramedullary diverticula into the neural arch and the neural spine. The regular branching pattern of the pneumatic cavities as well as the vertical I−beam construction of the vertebral corpora is interpreted as a consequence of the biomechanical constraints of the vertebral corpora in diplodocids. These reconstructions form the ground for functional morphological considerations in Diplodocidae and Dicraeosauridae while addressing the possible mechanical consequences of pneumatic structures for the integrity of the support system of the neck.
Źródło:
Acta Palaeontologica Polonica; 2007, 52, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mandibles of mastodonsaurid temnospondyls from the Upper Permian–Lower Triassic of Uruguay
Autorzy:
Pineiro, G.
Marsicano, C.A.
Damiani, R.
Powiązania:
https://bibliotekanauki.pl/articles/22097.pdf
Data publikacji:
2007
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Buena Vista Formation
Lower Triassic
Mastodonsauridae
South America
mastodonsaurid temnospondyl
Temnospondyli
Upper Permian
Uruguay
jaw
lower jaw
paleontology
morphology
Opis:
Partially preserved temnospondyl mandibles from the Late Permian–Early Triassic Buena Vista Formation of Uruguay are referred to the basal stereospondyl taxon Mastodonsauridae. These represent the earliest known members of this group for South America. In most cases, this assignment was based on the characteristic morphology of the postglenoid (= postarticular) area of the lower jaw together with the presence of a hamate process. Comparisons with basal mastodonsaurids indicate that the Uruguayan specimens are phenetically similar to Gondwanan and Laurasian Early Triassic taxa, such as Watsonisuchus, Wetlugasarus, and Parotosuchus. Nevertherless, they display some characters which have not previously been described in Mesozoic temnospondyls. The Permo−Triassic Uruguayan mastodonsaurids support a Gondwanan origin for the group, an event which probably occurred sometime during the latest Permian.
Źródło:
Acta Palaeontologica Polonica; 2007, 52, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The middle to Late Eocene evolution of nummulitid foraminifer Heterostegina in the Western Tethys
Autorzy:
Less, G
Ozcan, E.
Papazzoni, C.A.
Stockar, R.
Powiązania:
https://bibliotekanauki.pl/articles/21939.pdf
Data publikacji:
2008
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
biometry
Heterostegina
nummulitid foraminifer
paleontology
Foraminifera
stratigraphy
Eocene
evolution
Late Eocene
Western Tethys
Nummulitidae
Opis:
Megalospheric forms of Western Tethyan late Bartonian to late Priabonian involute Heterostegina from numerous localities, marking different ecological conditions, were morphometrically investigated. They belong to three species, H. armenica, H. reticulata, and H. gracilis based on the presence/absence of granulation, on the chamberlet characteristics and on the relative size of proloculus. Within these species a very rapid evolution could be observed in the reduction of the number of operculinid chambers, in the increase of the number of chamberlets and partially in the increase of the proloculus size. This evolution is demonstrated by stratigraphic superpositions in several localities (especially in the Mossano section), and is supported also by the change of co−occurring fossils, starting with the disappearance of large−sized Nummulites, then followed by the appearance of the genus Spiroclypeus and then by the disappearance of orthophragmines of middle Eocene acme. Based on the reduction of operculinid chambers, two chronosubspecies of Heterostegina armenica and seven of H. reticulata are defined biometrically (four of them: H. armenica tigrisensis, H. reticulata tronensis, H. r. hungarica, and H. r. mossanensis are introduced here). This allows to subdivide the Shallow Benthic Zone (SBZ) 18 into three and SBZ 19 into two subzones. The extremely rapid evolution of H. reticulata allows to calibrate larger foraminiferal events around the middle/late Eocene boundary. The extinction of large−sizedNummulitesseems to be heterochronous in the late Bartonian in having migrated eastward, while the first appearance of Spiroclypeus is shown to be synchronous at the base of the Priabonian. The middle/upper Eocene (= Bartonian/Priabonian) boundary is to be placed at the base of the Priabona marls in the Mossano section corresponding to the SBZ 18/19 limit, to the first appearance of genus Spiroclypeus, to that of Nummulites fabianii and of Heterostegina reticulata mossanensis. It falls into the upper part of both the P 15 and NP 18 planktic zones. The Western Tethyan Eocene involute Heterostegina became extinct, apparently with no Oligocene successors.
Źródło:
Acta Palaeontologica Polonica; 2008, 53, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The diversity of cimolestan mammals within the White River Group of South Dakota and Nebraska
Autorzy:
Boyd, C.A.
Weiler, M.W.
Householder, M.L.
Schumaker, K.K.
Powiązania:
https://bibliotekanauki.pl/articles/22320.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Opis:
The synonymization of the cimolestan taxa Cymaprimadon and Chadronia from the Late Eocene Chadron Formation is consistently upheld, despite a lack of supporting evidence. Here we show that the synonymization is unjustified, owing to distinct differences between these taxa in the mandibular tooth count (1-1-3-3 vs. ?-1-4-3), the identity of the enlarged anterior mandibular tooth (incisor versus canine), and the morphology of the crown of m3 (e.g., paraconid on m3 in Cymaprimadon). We also refer a specimen recently collected from the Early Oligocene Brule Formation within the Badlands National Park (BADL 16917) to Chadronia sp., thus making it the youngest occurrence of a pantolestan from North America. Examination of an additional specimen (FMNH UC 349) revealed the presence of a further cimolestan taxon in the White River Group of South Dakota, although the poor quality of the locality and stratigraphic data associated with this specimen precludes erecting a formal name. In total, this study doubles the number of cimolestans from the Late Chadronian and Orellan (Ch4 to Or1) of North America from two to four, and extends the biostratigraphic range of Pantolesta into the North American Oligocene.
Źródło:
Acta Palaeontologica Polonica; 2014, 59, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Distinguishing Quaternary glyptodontine cingulates in South America: How informative are juvenile specimens?
Autorzy:
Luna, C.A.
Cerda, I.A.
Zurita, A.E.
Gonzalez, R.
Prieto, M.C.
Mothe, D.
Avila, L.S.
Powiązania:
https://bibliotekanauki.pl/articles/20747.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Opis:
The subfamily Glyptodontinae (Xenarthra, Cingulata) comprises one of the most frequently recorded glyptodontids in South America. Recently, the North American genus Glyptotherium was recorded in South America, in addition to the genus Glyptodon. It has been shown that both genera shared the same geographic distribution in central-north and eastern areas of South America (Venezuela and Brazil, respectively). Although some characters allow differentiation between adult specimens of both genera, the morphological distinction between these two genera is rather difficult in juvenile specimens. In this contribution, a detailed morphological, morphometric and histological survey of a juvenile specimen of Glyptodontinae recovered from the Late Pleistocene of northern Brazil is performed. The relative lower osteoderms thickness, the particular morphology of the annular and radial sulci and the distal osseous projections of the caudal osteoderms suggest that the specimen belongs to the genus Glyptotherium. In addition, the validity of some statistical tools to distinguish between different ontogenetic stages and in some cases between genera is verified. The osteoderm microstructure of this juvenile individual is characterized by being composed of a cancellous internal core surrounded by a compact bone cortex. Primary bone tissue mostly consists of highly vascularized, woven-fibered bone tissue. Unlike that observed in adult Glyptodontinae, both the Sharpey fibers and the fibrous and laminar parallel bone tissue as secondary bone are absent. This study enhances our knowledge about those morphological and histological changes that occur through the ontogeny in glyptodonts.
Źródło:
Acta Palaeontologica Polonica; 2018, 63, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Feeding habits and habitat of herbivorous mammals from the Early–Late Hemphillian (Miocene) of Costa Rica
Autorzy:
Perez-Crespo, V.A.
Laurito, C.A.
Arroyo-Cabrales, J.
Valerio, A.L.
Morales-Puente, P.
Cienfuegos-Alvarado, E.
Otero, F.J.
Powiązania:
https://bibliotekanauki.pl/articles/21193.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Opis:
Carbon and oxygen stable isotope values in the dental enamel of fossils were used to infer the diet and habitat of the extinct equids Calippus hondurensis, Dinohippus mexicanus, and Protohippus gidleyi, the gomphothere Gomphotherium hondurensis, and the llama Hemiauchenia vera of the Early–Late Hemphillian (Hh2) from San Gerardo de Limoncito, Puntarenas province, Costa Rica. The results suggest that these mammals fed mainly on C₃ plants and lived in clearings of rainforests. This contrasts with previous studies from North America that indicated that the same species lived in forest savannas and fed mainly on C₄ plants, but it is similar to the results obtained from the palynological record of the area, as well as with several vegetation models suggesting the presence of humid tropical forest during the Miocene in Central America.
Źródło:
Acta Palaeontologica Polonica; 2018, 63, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
New sauropodomorph and cynodont remains from the Late Triassic Sacisaurus site in southern Brazil and its stratigraphic position in the Norian Caturrita Formation
Autorzy:
Marsola, J.C.A.
Bittencourt, J.S.
Da Rosa, A.A.S.
Martinelli, A.G.
Ribeiro, A.M.
Ferigolo, J.
Langer, M.C.
Powiązania:
https://bibliotekanauki.pl/articles/21152.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Opis:
Sacisaurus agudoensis is the only silesaurid known from the Triassic beds of the Santa Maria Supersequence and the correlation of its type locality to the other Triassic deposits of south Brazil has always been controversial. In an attempt to improve this, a handful of dinosaur and cynodont remains found associated to S. agudoensis are here described and compared. The anatomy of the sauropodomorph is more similar to that of Norian forms such as Pantydraco caducus and Unaysaurus tolentinoi than to that of Carnian taxa such as Saturnalia tupiniquim and Pampadromaeus barberenai. The cynodonts recovered based on isolated teeth include a brasilodontid and a Riograndia-like form. This assemblage is consistent with a Norian age, as is also suggested by local stratigraphic correlation, which positions the site in the Caturrita Formation.
Źródło:
Acta Palaeontologica Polonica; 2018, 63, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The brachiopod Lingula in the Middle Miocene of the Central Paratethys
Autorzy:
Emig, C C
Bitner, M.A.
Powiązania:
https://bibliotekanauki.pl/articles/20475.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Lingula dregeri
Miocene
brachiopod
Middle Miocene
deposit
Lingula dumortieri
paleontology
Lingula
Opis:
In the Middle Miocene deposits of the Central Paratethys, lingulides, because of their low taphonomic potential, are very rare and difficult to identify. Two species of Lingula, L. dumortieri Nyst, 1843 and L. dregeri Andreae, 1893, have been recorded from the Badenian (Middle Miocene) of Poland. Re−examination of the specimens has shown that none of them can be referred to Lingula dumortieri (now Glottidia dumortieri). The rounded outline of the scar of the posterior adductor muscle and the lack of the septa indicate that all the specimens must be referred to the genus Lingula. Their valves appear to be slightly more convex than in other species of Lingula and closely resemble the Recent L. tumidula Reeve, 1841. We assign all the specimens of Lingula found in the Miocene of Poland to L. dregeri. Because our specimens are juveniles and some are broken we cannot adequately redescribe this species. Lingula dregeri was distributed in the Middle Miocene of the Central Paratethys (Austria, Poland, Ukraine, Romania), while Glottidia dumortieri occurs in the Pliocene of Northern Europe (Atlantic Province).
Źródło:
Acta Palaeontologica Polonica; 2005, 50, 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:
Soft-tissue attachment structures and taphonomy of the Middle Triassic nautiloid Germanonautilus
Autorzy:
Klug, C
Lehmkuhl, A.
Powiązania:
https://bibliotekanauki.pl/articles/21103.pdf
Data publikacji:
2004
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
soft tissue attachment
Nautiloidea
nautiloid
Triassic
structure
conch
taphonomy
Germany
Middle Triassic
paleoecology
Germanonautilus
paleontology
Opis:
New examinations of numerous steinkerns of the Middle Triassic nautiloid Germanonautilusfrom southern Germany revealed new anatomic, ecologic, and taphonomic details, which are compared with Recent Nautilus. The attachment structures of the cephalic retractor muscle (large scar) and of the dorsal (black layer) and the posterior mantle (posterior narrow scar, anterior band scar of the mantle and septal myoadhesive bands), some with tracking bands (recording the anteriorward movement of the soft body during ontogeny), were seen in several specimens. The shape and proportions of these soft−tissue attachment structures resemble those of Recent Nautilus macromphalus and indicate a similar soft part anatomy. Based on their conch geometry, the mode of locomotion of Germanonautilus is reconstructed. Owing to the wide whorl cross section and the high whorl expansion rate, drag of the conchs was high, the aperture was oriented at an oblique angle which made Germanonautilus a rather slow horizontal swimmer. Because of their large sizes and widths, conchs of Germanonautilus were often deposited on their broad venters, forming elevated “benthic islands” (secondary hardgrounds). A broad range of animals (fish, decapods, ophiurans, crinoids, brachiopods, bryozoans, bivalves, Spirorbis, foraminiferans) lived in and on these comparatively large secondary hardgrounds.
Źródło:
Acta Palaeontologica Polonica; 2004, 49, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Jurassic juvenile ammonites of the Jagua Formation, Cuba
jurajskie młodociane amonity z formacji Jagua na Kubie
Autorzy:
Kulicki, C.
Wierzbowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/21217.pdf
Data publikacji:
1983
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Opis:
Early ontogenetic stages of some Ammonitina (mostly Perisphinctidae) are described from the Oxfordian Jagua Formation of western Cuba. Fourty six percent of the sample are specimens attaining the nepionic swelling with more than four septa developed. Juvenile jaw apparatus found for the first time in specimens with only 2,25 whorls, displays primitive elements corresponding to conchorhynch and rhyncholit of nautiloids, litoceratids and phylloceratids. The fauna and sediment features evidence a low water energy and low oxigenated conditions at the bottom during the sedimentation. The juvenile ammonites occur together with numerous adults which are represented by corresponding micro- and macroconchs; it indicates for the proximity of a breeding place.
W ciemnych konkrecjach wapiennych z formacji Jagua zaliczanej do oksfordu środkowego, w prowincji Pinar del Rio w zachodniej Kubie, występują masowo mikroskopijne muszle amonitów obok dużych, często dorosłych form. Na podstawie wyraźnej dominacji przedstawicieli Perisphinctidae wśród dużych okazów można sądzić, że również wśród form młodocianych grupa ta jest licznie reprezentowana. Badania przeprowadzono na płytkach cienkich i opracowano statystycznie ponad sto młodocianych okazów (fig. 1—2). Okazało się, że 46% całej próby stanowią okazy, których muszle osiągnęły stadium definitywnie wykształconego zgrubienia nepionicznego. Okazy takie posiadają średnio ponad cztery septa (proseptum i nakrosepta). Większość współczesnych badaczy uważa, że stadium to jest charakterystyczne dla świeżo wyklutych osobników. Masowość występowania takich okazów potwierdza tezę, iż po wykluciu następował kryzys fizjologiczny eliminujący znaczną część osobników. W dwóch młodocianych okazach znaleziono w komorze mieszkalnej szczątki aparatów szczękowych (fig. 3—4, pl. 7—8) stanowiące pierwsze znalezisko aparatów na tak wczesnym etapie rozwoju osobniczego. Szczęka dolna posiada organiczną blaszkę zewnętrzną o długości zbliżonej do wysokości ujścia komory mieszkalnej, podobnie jak w anaptychu i aptychu. Niestety, na podstawie przekrojów nie udało się stwierdzić, czy jest to twór parzysty czy nieparzysty. Obie szczęki posiadają wapienne elementy odpowiadające konchorynchowi w szczęce dolnej i ryncholitowi w szczęce górnej, dzięki czemu są podobne do aparatów szczękowych współczesnego łodzika oraz przedstawicieli górnokredowych Litoceratina i Phylloceratina. Występowanie aparatu szczękowego typu ‘nautilusowego’ u młodocianego przedstawiciela Ammonitina świadczy z jednej strony o pierwotności aparatu typu ‘nautilusowego’, a z drugiej o rekapitulacji w rozwoju aparatu szczękowego typu anaptychowego i aptychowego. Obecność aparatu szczękowego typu ‘nautilusowego’ u górnokredowych Litoceratina i Phylloceratina jest zatem cechą pierwotną. W świetle powyższych danych mało prawdopodobna wydaje się koncepcja Dzika (1981), w której wywodzi on formę dolnej szczęki współczesnego łodzika od operkulum ślimaków morskich, poprzez formy typu anaptych-aptych. Analiza paleoekologiczna zespołu skamieniałości występujących w osadach razem z amonitami wykazuje obfitość form nektonicznych i planktonicznych i ubóstwo form bentonicznych, ograniczonych do cementujących małży ostrygowatych, które zasiedlały leżące na dnie muszle amonitów. Ponadto, w osadzie uderza (1) brak składników ziarnistych, typowych dla wód o wysokiej energii, (2) obecność i równomierne rozmieszczenie drobnoziarnistego pirytu, (3) a także dobre zachowanie skamieniałości, które nie uległy niszczącemu działaniu czynników mechanicznych i biologicznych. Cechy te świadczą o niskiej energii środowiska sedymentacji i dominowaniu warunków redukcyjnych na powierzchni osadu. Warunki redukcyjne sprzyjały dobremu zachowaniu delikatnych muszli młodocianych amonitów, m.in. poprzez zwiększenie alkaliczności środowiska, co zapobiegało ich rozpuszczaniu w procesie sedymentacji i diagenezy. Najbardziej typowym elementem omawianych osadów jest stowarzyszenie form młodocianych i dymorficznych form dorosłych amonitów, reprezentowanych przez odpowiadające sobie mikro- i makrokonchy (Wierzbowski 1976); w analizowanych rodzinach Perisphinctidae i Glochiceratidae proporcje ilościowe występowania mikro- i makrokonch mogą być określone 1:1. Znaleziska te mogą być interpretowane jako wskaźnik bliskości miejsca lęgowego amonitów.
Źródło:
Acta Palaeontologica Polonica; 1983, 28, 3-4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The odonatan insects from the Paleocene of Menat, Central France
Autorzy:
Nel, A.
Jouault, C.
Powiązania:
https://bibliotekanauki.pl/articles/31341382.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
paleontology
insect
Insecta
Odonata
fossil
Macrogomphus menatensis
Menatagrion hervetae
Menatlestes palaeocenicus
Thanetophilosina menatensis
Valerea multicellulata
Anisoptera
Cephalozygoptera
Zygoptera
head
morphology
Paleocene
Menat town
France
Auvergne region
Źródło:
Acta Palaeontologica Polonica; 2022, 67, 3; 631-648
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
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