Hasil untuk "Paleontology"

Diego Hernández-Sandoval, Marisol Montellano-Ballesteros, Ricardo Vasconcelos-Ginzo et al.

We present a multi-proxy geochemical analysis of proboscidean and equid teeth from a newly-documented Blancan (Pliocene–Pleistocene) locality in north-western Mexico. Eleven dental elements (six from equids and five from gomphotheres) were analysed by electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and isotope ratio mass spectrometry (IRMS) to assess preservation and reconstruct palaeoecological and palaeoclimatic patterns. All specimens show excellent microstructural integrity, with stable Ca/P and F/P ratios indicating near-stoichiometric hydroxyapatite and excellent preservation. Trace-element concentrations (Sr, Ba) and flat, PAAS-normalised REE+Y profiles indicate minimal diagenetic overprint, permitting the retention of biogenic signals. Stable carbon isotope values (δ13Cdiet,meq) reveal predominantly mixed C3–C4 feeding strategies, with proboscideans consuming proportionally more C4 vegetation than equids. The latter exhibit higher Ba/Ca and Sr/Ca ratios despite lower δ13Cdiet,meq enrichment, suggesting selective feeding or height-related browsing. Mean annual precipitation (MAP ≈ 125 mm/year), derived from δ13Cdiet,meq values, indicates arid conditions within the envelope expected for semi-arid to arid ecosystems documented for the late Neogene–early Quaternary across North America and other regions worldwide. Oxygen isotope compositions (δ18O) imply similar climatic settings amongst taxa, with interindividual variability linked to physiology, mobility or access to distinct water sources. Mean annual temperature (MAT ≈ 15 °C) agrees with independent proxies and is consistent with late Pliocene conditions warmer than present. These results provide the first quantitative reconstruction of Blancan terrestrial climate in north-western Mexico, offering new insights into mammalian ecological adaptations and environmental dynamics during the Pliocene–Pleistocene transition.

Martin Pickford, Christian De Muizon

Re-interpretation of the holotype and only known speci-men of Afrophoca libyca reveals that it represents a me-dium -sized anthracothere, Afromeryx zelteni, a species that is common in the basal Middle Miocene deposits at Gebel Zelten, Libya. This re-identification affects several recently published papers that have accepted it as the earliest known phocid, with repercussions on biogeographic scenarios and phylogeny reconstructions.

Kun-sheng Du, Jin Guo, Sarah R Losso et al.

Euarthropods are an extremely diverse phylum in the modern, and have been since their origination in the early Palaeozoic. They grow through moulting the exoskeleton (ecdysis) facilitated by breaking along lines of weakness (sutures). Artiopodans, a group that includes trilobites and their non-biomineralizing relatives, dominated arthropod diversity in benthic communities during the Palaeozoic. Most trilobites – a hyperdiverse group of tens of thousands of species - moult by breaking the exoskeleton along cephalic sutures, a strategy that has contributed to their high diversity during the Palaeozoic. However, the recent description of similar sutures in early diverging non-trilobite artiopodans means that it is unclear whether these sutures evolved deep within Artiopoda, or convergently appeared multiple times within the group. Here, we describe new well-preserved material of Acanthomeridion, a putative early diverging artiopodan, including hitherto unknown details of its ventral anatomy and appendages revealed through CT scanning, highlighting additional possible homologous features between the ventral plates of this taxon and trilobite free cheeks. We used three coding strategies treating ventral plates as homologous to trilobite-free cheeks, to trilobite cephalic doublure, or independently derived. If ventral plates are considered homologous to free cheeks, Acanthomeridion is recovered sister to trilobites, however, dorsal ecdysial sutures are still recovered at many places within Artiopoda. If ventral plates are considered homologous to doublure or non-homologous, then Acanthomeridion is not recovered as sister to trilobites, and thus the ventral plates represent a distinct feature to trilobite doublure/free cheeks.

BOTOND LÁZÁR, MOSTAFA FALAHATGAR, MEHDI SARFI et al.

Lower Miocene sediments from a previously not investigated outcrop of the Qom Formation (Central Iranian Basin) were studied for their foraminiferal and calcareous nannofossil content. The studied stratigraphic record is assigned to the upper part of calcareous nannofossil NN2 Zone/CN1c Subzone and to the benthic foraminiferal Borelis melo melo Zone of Burdigalian age. The diversity indices, benthic foraminiferal morphogroups, and quantitative analyses of assemblages (principal component and cluster analysis) suggest an overall shallow-marine depositional environment. This interpretation is well constrained based on the dominance of the B1 benthic foraminifera morphotype with biconvex, trochospiral calcareous test, and epifaunal habitat. The identified six cluster groups of benthic foraminiferal assemblages are confirmed by the principal component analysis too, and their distribution along the studied section argue for dynamic changes of the environment. This is well exemplified by a more or less constant shallowing, then deepening trend of the environment as revealed by the shifting from the high diversity, shallow-shelf assemblages of Cluster 5 and 6 toward the low diversity, near-shore Ammonia tepida and Porosononion subgranosus assemblage (Cluster 1), and back.

Yan Zheng, Haiyan Hu, Dong Chen et al.

The present corrigendum corrects errors that occurred in: Zheng Y., Hu H., Chen D., Chen J., Zhang H. & Rasnitsyn A.P. 2021. New fossil records of Xyelidae (Hymenoptera) from the Middle Jurassic of Inner Mongolia, China.  European Journal of Taxonomy 733: 146–159. https://doi.org/10.5852/ejt.2021.733.1229

Patrick L. Jambura, Eduardo Villalobos-Segura, Julia Türtscher et al.

The Late Jurassic elasmobranch <i>Protospinax annectans</i> is often regarded as a key species to our understanding of crown group elasmobranch interrelationships and the evolutionary history of this group. However, since its first description more than 100 years ago, its phylogenetic position within the Elasmobranchii (sharks and rays) has proven controversial, and a closer relationship between <i>Protospinax</i> and each of the posited superorders (Batomorphii, Squalomorphii, and Galeomorphii) has been proposed over the time. Here we revise this controversial taxon based on new holomorphic specimens from the Late Jurassic Konservat-Lagerstätte of the Solnhofen Archipelago in Bavaria (Germany) and review its skeletal morphology, systematics, and phylogenetic interrelationships. A data matrix with 224 morphological characters was compiled and analyzed under a molecular backbone constraint. Our results indicate a close relationship between <i>Protospinax</i>, angel sharks (Squatiniformes), and saw sharks (Pristiophoriformes). However, the revision of our morphological data matrix within a molecular framework highlights the lack of morphological characters defining certain groups, especially sharks of the order Squaliformes, hampering the phylogenetic resolution of <i>Protospinax annectans</i> with certainty. Furthermore, the monophyly of modern sharks retrieved by molecular studies is only weakly supported by morphological data, stressing the need for more characters to align morphological and molecular studies in the future.

Kumiko Matsui, Yuri Kimura

Vertebrates developed tooth replacement over 400 million years ago. Then, 200 million years later, the combination of vertical tooth replacement with the thecodont implantation (teeth in bone sockets) appeared a key morphological innovation in mammalian evolution. However, we discovered that an extinct fish taxon, <i>Serrasalmimus secans</i>, showed the same innovation in the lineage Serrasalmimidae, which survived the end Cretaceous mass extinction event. The carnassial teeth are known in both mammals and pycnodont fish, but these teeth do not share the same tissues or developmental processes. Therefore, this serrasalmimid pycnodont fish might have independently acquired mammal-like tooth replacement and implantation, indicating that the fish and mammals convergently evolved the carnassial dental morphologies at about the same time, approximately 60 My ago, in separate ecosystems.

Danielle Fraser, Amelia Villaseñor, Anikó B. Tóth et al.

Biotic homogenization, which is increased similarity in the composition of species among communities, is rising due to human activities. Using North American mammal fossil records from the past 30,000 years, this study shows that this phenomenon is ancient, beginning between 12,000 and 10,000 years ago with the extinction of the mammal megafauna.

Minaev Alexander P.

This work introduces a collection of stone-made architectural details and decorations found in the course of archaeological research of the Golden Horde town of Azak. When analyzing the architectural decorations, the main attention was paid to the search for analogies in the regions which were part of the Azak's trade and cultural relations. The work describes the peculiarities of ornamentation, construction methods and chronological attribution of the complexes where the finds were discovered. Close cultural connections were revealed between the local masters and the builders from the Golden Horde Crimea who, in turn, adopted the traditions from Seljuk architects who moved to the peninsula in the middle of the 13th century. It became possible to identify a local tradition of stone carving with no analogies in other Golden Horde towns and neighboring regions.

LUCIA CAPRARA, EDUARDO GARZANTI, MARIO GNACCOLINI et al.

During Serravallian time, a shallow—water shelf mantled by northward migratine sand waves occupied the eastern part of the Tertiary Piedrnont Basin (Serravalle Sandstone, Gavi area). Towards the west, the shelf graded into a basinal zone through a series of steps probably controlled by synsedimentary faults. The autochthonous sediments of the shelf—basin transition were sandy siltstones, which are interbedded in the stratigraphical column with sands carried from near—shore arcas by tectonically—triggered sediment gravity flows. On the Proxima] "steps traction currents could rework these sands and re—form sand waves, while in deeper water they were buried without further reworking. Finally, at the western edge of the study area (Cassinasco), "high—dcnsity" turbidity currents flowing towards the ENE depositcd the sands of the Cassinasco Fm. onto the deep bottoni of the basmal zone. Riv. IC. Paleont. Strat. 90   pp. 545—564 Marzo 1985 Two distinct petrofacies characterize the Serravalle hybrid arenites (bioclastic lithic arkoses) and the Cassinasco sandstones (litharenites), pointing to different source terranes. The Cassinasco Fm. was fed by the Alpine fold—thrust belt, comprising Carboniferous metasediments, Permlan igneous rocks, Mesozoic sediments and the Ligurid Allochthon. The paragencsis of lithic fragrnents and the heavy mineral assemblage show that the source rocks bave undergone blueschist facies (eoalpine) and greenschist facies (rnesoalpine) polyphase rnetarnurpllism. The Serravalle arenites bave a similar "aphanite" rock fragment population, but detritus frorn granitoid bodies is prominent and the detrital modes are closer to the Tertiary clastic units of the Apennines.

Artem Kouchinsky

The following specimen/sample accession numbers and accompanying information are updated

Victoria M. Arbour, Lindsay E. Zanno, Derek W. Larson et al.

Dakotaraptor steini is a recently described dromaeosaurid dinosaur from the Upper Cretaceous (Maastrichtian) Hell Creek Formation of South Dakota. Included within the D. steini hypodigm are three elements originally identified as furculae, one of which was made part of the holotype specimen. We show that the elements described as D. steini ‘furculae’ are not theropod dinosaur furculae, but are rather trionychid turtle entoplastra referable to cf. Axestemys splendida. The hypodigm of D. steini should be adjusted accordingly.

P. Skrzycki

The paper refines the taxonomic assignment of the only representative of the dipnoan genus <i>Gnathorhiza</i> from the Lower Triassic of Poland. It is assigned here to <i>Gnathorhiza otschevi</i> on the basis of morphological and biometrical similarity with the tooth plates from coeval strata of the European part of Russia. The material is comprised solely of tooth plates, both the upper and the lower ones. It comes from karst deposits of the Czatkowice 1 locality (southern Poland) dated to late Olenekian, Lower Triassic. The presence of <i>G. otschevi</i> in southern Poland widens its palaeobiogeographic Triassic record by more than 2000 km to the west. Czatkowice 1 locality is the only known occurrence of gnathorhizids within the Germanic Basin. <i>G. otschevi</i> from Czatkowice 1 shows petrodentine in the tooth plate. Its presence is proved for the first time in a Triassic gnathorhizid. <i>Gnathorhiza</i> was most widely distributed during the Permian and restricted to Europe in the Triassic. Tooth plates of both Early Triassic European and Late Permian Brazilian gnathorhizids are more similar to each other than to Permo-Carboniferous American ones.

Marcelo A. Reguero, Sergio F. Vizcaíno, Francisco J. Goin et al.

Abstract. A moderately diverse terrestrial biota is known from the Eocene - ?early Oligocene La Meseta Formation, Seymour Island, Antarctic Peninsula. The La Meseta Formation fills an incised valley and comprises sediments that represent deltaic, estuarine and very shallow marine environments. Forests of both deciduous and evergreen trees were dominated by Nothofagus, podocarps, and araucarian conifers. The La Meseta paleoflora is distinctive in having a predominance of Antarctic taxa; this suggests a seasonal, cold-temperate, rainy climate and a latitudinal gradient. Among the terrestrial vertebrates, there are at least nine mammal taxa, predominantly tiny marsupials (mostly endemic and new genera). The presence of these marsupials suggests the existence of some form of isolating barrier (climatic and/or geographic), which must have allowed development of this endemic fauna. Comparisons with faunas assigned to the Itaboraian (late Paleocene), Riochican (late Paleocene), Casamayoran (early Eocene), and Mustersan (tentatively assigned to the middle Eocene) ages of Patagonia were made. The assemblage of terrestrial vertebrates of the La Meseta Formation is unusual in the dominance of several endemic forms. The occurrence of protodidelphid and derorhynine marsupials, that had become extinct elsewhere in the Eocene of South America, on Seymour Island also indicates that isolation may have allowed extended survival of these taxa in the Eocene of Antarctica. The nature, distribution, and composition of the La Meseta fauna firmly suggest a latitudinal differentiation in the middle Eocene. Paleogeographic evidence suggests that the terrestrial mammals of the La Meseta Formation probably lived under crepuscular and even extended nocturnal conditions (assuming that the angle of the earth's spin axis was relatively the same as it is now) during part of the year. KEY WORDS. Antarctic Peninsula. Eocene. High latitude fauna. Mammals. Palaeobiogeography.    Resumen. VERTEBRADOS EOCENOS TERRESTRES DE ALTAS LATITUDES DE ANTÁRTIDA COMO EVIDENCIA BIOGEOGRÁFICA. Una biota moderadamente diversa es conocida en la Formación La Meseta (Eoceno-Oligoceno temprano?), isla Seymour, Península Antártica. La Formación La Meseta rellena un valle incidido y comprende sedimentos que representan ambientes estuáricos y marinos muy someros. Bosques con árboles deciduos y perennes estuvieron dominados por Nothofagus, y coníferas podocarpáceas y araucarias. La paleoflora de la Formación La Meseta es distintiva y predominan taxones antárticos que sugieren un clima templado frío, lluvioso, estacional y un gradiente latitudinal. Dentro de los vertebrados terrestres hay 9 taxones de mamíferos, predominantemente pequeños marsupiales, mayormente endémicos y novedosos, que sugieren que alguna forma de barrera de aislamiento, climática y/o geográfica, debió haber permitido el desarrollo de esta fauna endémica. Se realizaron comparaciones con las faunas asignadas a las edades mamífero Itaboraiense (Paleoceno tardío), Riochiquense (Paleoceno tardío), Casamayorense (Eoceno temprano) y Mustersense (tentativamente asignada al Eoceno medio). La fauna de la Fm. La Meseta es particular por el predominio de varias formas endémicas. La presencia de marsupiales protodidélfidos y derorhinchinos, los cuales ya no se registran en ninguna de las faunas del Eoceno de América del Sur, indica que el aislamiento pudo haber permitido la supervivencia de estos taxones en el Eoceno de Antártida. La naturaleza, distribución y composición de la fauna de la Fm. La Meseta firmemente sugiere una diferenciación latitudinal en el Eoceno medio. Finalmente, las evidencias paleogeográficas sugieren que los mamíferos terrestres de la Formación La Meseta probablemente vivieron bajo condiciones crepusculares, aún nocturnas (asumiendo que la oblicuidad del eje de la Tierra fue relativamente la misma que la actual), durante parte del año. PALABRAS CLAVE. Península Antártica. Eoceno. Fauna de alta latitud. Mamíferos. Paleobiogeografía.

Edgardo Ludueña

Historia del Museo Casa Ameghino de Luján

Y. Kubota, K. Kimoto, T. Itaki et al.

To understand bottom water variability in the subtropical northwestern Pacific, bottom water temperatures (BWTs), carbon isotopes (&delta;¹³C), and oxygen isotopes of seawater (δ¹⁸O_w) at a water depth of 1166 m were reconstructed from 26 kyr BP to present. A new regional Mg / Ca calibration for the benthic foraminifera <i>Cibicidoides wuellerstorfi</i> (type B) was established to convert the benthic Mg / Ca value to BWT, based on 26 surface sediment samples and two core-top samples retrieved around Okinawa Island. During the Last Glacial Maximum (LGM), the δ¹⁸O_w in the intermediate water in the northwestern South Pacific was ~0.4&permil; lower than in the deep South Pacific, indicating a greater vertical salinity gradient than at present. This salinity (and probably density) structure would have led to stratification in the intermediate and deep Pacific, which would, in turn, have greatly influenced carbon storage during the glacial time. The benthic Mg / Ca and δ¹⁸O_w records suggest changes that seem to follow Heinrich event 1 (H1) and the Bølling–Alleød (B/A) and Younger Dryas (YD) intervals, with BWT higher during H1 (~17 kyr BP) and YD (~12 kyr BP) and lower during B/A (~14 kyr BP). The warming in the bottom water during H1 suggests increased contribution of North Pacific Intermediate Water (NPIW) to the subtropical northwestern Pacific and decreased upwelling of cooler waters from the abyssal North Pacific. During the interval from 17 to 14.5 kyr BP, the BWT tended to decrease successively in association with a decrease in δ¹³C values, presumably as a result of increased upwelling of the abyssal waters to the intermediate depths of the North Pacific caused by shoaling and enhancement of the southward return flow of Pacific Deep Water (PDW). During the Holocene, the millennial- to sub-millennial-scale variations in the BWT generally correlate with the sea surface temperatures in the Okhotsk Sea, the source region of the NPIW, suggesting that changes in the BWT are linked to changes in the NPIW production rate.

R. Feldmann, M. Woodburne

Pedro R. Gutierrez

An Upper Paleozoic palynological assemblage from the Cerro Agua Negra Formation, Calingasta-Uspallata Basin, San Juan Province, Argentina, is described for the first time. The sporomorphs have been recovered at Las Leñas Creek from carbonaceous shales, which have been deposited in a subaerial environment corresponding to alluvial plain and interdistributary bays facies. The stratigraphic significance of the miospore assemblage is discussed.

J. Pojeta, B. Runnegar

J. Lipps