Hasil untuk "Paleontology"

Xavier Delclòs, Enrique Peñalver, Carlos Jaramillo et al.

Abstract Amber, a fossilised resin, became widespread during the Barremian ( ~ 122 Ma), marking the onset of the Cretaceous Resinous Interval (125–72 Ma). While common in the Northern Hemisphere, amber containing terrestrial arthropod inclusions had not previously been reported from the Mesozoic of South America. Here, we report the major occurrence of such amber from the early Albian ( ~ 112 Ma) Hollín Formation in Ecuadorian Napo region. Discovered at the Genoveva quarry, the amber is associated with coeval pollen and plant macrofossils deposited in fluvio-lacustrine environments. Geochemical analyses suggest araucariacean trees as the resin source, while palynological and macrofloral data indicate moderately diverse forests and the earliest known angiosperm leaf assemblage from north-western South America. Arthropods (hexapods and arachnids) representing at least six orders are well preserved. These findings provide direct evidence of a humid, resinous forest ecosystem and its arthropod fauna in equatorial Gondwana during the Cretaceous Resinous Interval.

Christopher J. Bae, Xiujie Wu

Roxanne M. W. Banker, Roxanne M. W. Banker, Ashley A. Dineen et al.

Ecosystem structure—that is the species present, the functions they represent, and how those functions interact—is an important determinant of community stability. This in turn affects how ecosystems respond to natural and anthropogenic crises, and whether species or the ecological functions that they represent are able to persist. Here we use fossil data from museum collections, literature, and the Paleobiology Database to reconstruct trophic networks of Tethyan paleocommunities from the Anisian and Carnian (Triassic), Bathonian (Jurassic), and Aptian (Cretaceous) stages, and compare these to a previously reconstructed trophic network from a modern Jamaican reef community. We generated model food webs consistent with functional structure and taxon richnesses of communities, and compared distributions of guild level parameters among communities, to assess the effect of the Mesozoic Marine Revolution on ecosystem dynamics. We found that the trophic space of communities expanded from the Anisian to the Aptian, but this pattern was not monotonic. We also found that trophic position for a given guild was subject to variation depending on what other guilds were present in that stage. The Bathonian showed the lowest degree of trophic omnivory by top consumers among all Mesozoic networks, and was dominated by longer food chains. In contrast, the Aptian network displayed a greater degree of short food chains and trophic omnivory that we attribute to the presence of large predatory guilds, such as sharks and bony fish. Interestingly, the modern Jamaican community appeared to have a higher proportion of long chains, as was the case in the Bathonian. Overall, results indicate that trophic structure is highly dependent on the taxa and ecological functions present, primary production experienced by the community, and activity of top consumers. Results from this study point to a need to better understand trophic position when planning restoration activities because a community may be so altered by human activity that restoring a species or its interactions may no longer be possible, and alternatives must be considered to restore an important function. Further work may also focus on elucidating the precise roles of top consumers in moderating network structure and community stability.

Selina Robson, Joshua A. Ludtke, Jessica M. Theodor

Leptoreodon is a basal member of the Protoceratidae, an extinct group of artiodactyls variably allied with the Camelidae and the Ruminantia. The basicranial morphology of other protoceratids (Leptotragulus, Protoceras, Syndyoceras) is similar to that of ruminants, supporting the hypothesis that the two clades are closely related. However, study of the basicranium of Leptoreodon major has revealed that protoceratid basicranial morphology is more variable than previously thought. Leptoreodon does share morphological features with some, if not all, other protoceratids, but the taxon also has some features not previously documented in the family. These previously undocumented features resemble the basicranial morphology of camelids rather than ruminants, suggesting that previous hypotheses of protoceratid relationships need to be reexamined.

Leandro Martín Pérez, Diego Brandoni, Sergio Martínez

The freshwater mussels of the family Hyriidae (Bivalvia) are widespread in the Neotropical region, including several fossil and living species of the genus Diplodon Spix. A specimen assigned to Diplodon sp., recovered from the “Conglomerado osífero” (late Miocene) at La Toma Vieja, north of Paraná City (Entre Ríos Province, Argentina), is described herein. The report of Diplodon sp. in the “Conglomerado osífero” would support the traditional interpretation of a fluvial paleoenvironment for this horizon. This is the first accurate fossil record of the genus for the Entre Ríos Province, extending the occurrence of the family Hyriidae to the late Miocene of the Mesopotamian region.

Fattaneh Zamani, Mehdi Yazdi, Ali Bahrami et al.

Abstract Devonian deposits of the Bahram Formation with a thickness of 300 m were studied based on conodont fauna in Shahzadeh Mohammad section (33 km east of Zarand, 95 km north of Kerman city) in central Iran structural Zone. According to 31 identified species and subspecies and their stratigraphic development, nine conodont biozones belonging to the middle Givetian to the lower Famennian age were identified. The presence of Polygnathus ansatus  determines the ansatus Zone and Icriodus arkonensis arkonensis, determines the age of middle Givetian for the base of the Bahram Formation, which is the oldest age determined for the base of the Bahram Formation. Based on conodont distributions and conodont biofacies, polygnathid-icrodid biofacies are the most abundant biofacies in the section, indicating the middle shelf environment for the studied deposits. Keywords: Devonian, Conodont, Bahram Formation, Givetian–Famennian, Biofacies.   Introduction The Devonian, one of the most important periods in the Paleozoic, was a time of major sea-level changes and catastrophic events (Sandberg et al. 2002). Besides, it was a time of exceptionally high sea-level stand. It inferred widespread equable climates, which resulted in the most significant carbonate production and diversity of marine fauna in the Paleozoic (Gradstein et al. 2005). The Late Devonian was a time of many sea-level changes, catastrophic events, and two mass extinctions, knowledge of which is gained mainly through a high-resolution conodont biochronology (Sandberg and Ziegler 1996). The Devonian is the time for the radiation of fish and the appearance of the first ammonoids, insects, and amphibians. Vascular plants and forests became established; plants took over the land and became so plentiful that the first coal deposits were formed in tropical swamps. Besides, before the end of the period, land tetrapods appeared. Due to the greenhouse climate condition and sea-level highstand, global reef growth reached an acme in the Middle Devonian (Gradstein et al. 2005). Due to the relative rise of sea level, Middle and Late Devonian sediments were deposited in the northern, eastern, and central parts of Iran. In Central Iran, Middle and Late Devonian succession are exposed in the Kerman, Tabas, Yazd, and Isfahan regions. In Kerman, these deposits are limited to the northern parts of the region and are introduced and studied as Sibzar and Bahram formations. The Sibzar Formation, has few occurrences and only in two disjunct areas can be traced (Wendt et al. 2002). This formation is placed between the Padeha and the Bahram formations. The Bahram Formation consists of siliciclastic and carbonate strata. There is a complete profile from Lower to Upper Devonian deposits in the Shahzadeh Mohammad section, east of Zarand. The studied section is part of the Kerman-Tabas Block, which constitutes one of the individual structural units of the Central-East-Iranian Microcontinent. In this study, the biostratigraphy, biofacies, and sea-level changes of the Bahram Formation in the Shahzadeh Mohammad section have been investigated based on conodont fauna.   Material & Methods In total, 300 m of the Middle–Upper Devonian successions (Bahram Formation) at the Shahzadeh Mohammad section has been measured. Forty samples, about 4–5 kg, were systematically collected and treated with conventional preparation methods. The samples were processed with diluted acetic/formic acid (20%). The residue was washed by sieving ((using sieve Mesh numbers 10, 30, 60, and 100). The conodonts were extracted from residues by hand picking.   Discussion of Results & Conclusions Ancyrodella, Icriodus, Pelekysgnathus, Polygnathus are the present genera in this section. Conodont biofacies and relative sea-level changes of the Middle–Upper Devonian Shahzadeh Mohammad section have been investigated and compared with the global sea-level curve. The biofacies interpretation is based on the distribution of the above four genera in the conodont biofacies presented by Sandberg and Dreesen (1984). Since the dominant genera of this section are Icriodus and Polygnathus, frequency changes of these genera determine conodont biofacies and relative sea-level changes. Polygnathus indicates an increase and Icriodus indicates a decrease in the relative sea-level. The following biofacies were identified: icriodid, icriodid-polygnathid, polygnathid-icriodid, and polygnathid biofacies. Polygnathid-icriodid biofacies is the most abundant biofacies. Due to the presence of shallow-water species, the abundance of Icriodus and Polygnathus, the absence of the genus Palmatolepis, the middle shelf environment is determined for the Bahram Formation in the Shahzadeh Mohammad section. In general, all of the Devonian succession  from the Kerman area have been deposited in a shallow-water environment, and generally indicates the shallow parts of the Paleotethys. Our examination has yielded new conodont data from the Bahram Formation in the Shahzadeh Mohammad section. The ansatus Zone to Palmatolepis glabra pectinata Zone (middle Givetian to lower Famennian) were assigned to the Bahram Formation within nine conodont zones (Zamani et al. 2020). Conodonts from the sample Sh7 (Polygnathus ansatus and Icriodus arkonensis arkonensis) indicate Givetian age for the basal part of the Bahram Formation; but Middle Frasnian age is reported in previous studies in this area. The first appearance of Ancyrodella rotundiloba pristina represents Givetian/Frasnian boundary at sample Sh12.

Łucja Fostowicz-Frelik, Łucja Fostowicz-Frelik, Łucja Fostowicz-Frelik et al.

Jerzy Fedorowski, E. Wayne Bamber, Barry C. Richards

Colonies of the rugose corals Nemistium liardense sp. nov. and Heritschioides simplex sp. nov. were collected from limestone in the upper member of the Mattson Formation in the Liard Range in the Northwest Territories and are the only known identifiable coral species from the Mattson Fm. The Mattson Fm., deposited in the Liard Basin west of the syndepositional Bovie reverse fault, comprises sandstone with subordinate shale and carbonates deposited during several delta cycles. The close morphological similarity and identical mode of offsetting in N. liardense colonies from the Mattson Fm. and the allochthonous Stikine Terrane of British Columbia indicate they belong in the same species. This and the morphological similarity between H. simplex and the late Serpukhovian to early Bashkirian H. columbicum allow assignment of the coral-bearing part of the upper Mattson Fm. to Bashkirian Foraminiferal Biozone 20. Widespread occurrence of the genus Nemistium confirms open communication between the Liard Basin region and the western European and northern African seas.

Song Xing, Kristian J. Carlson, Pianpian Wei et al.

Background Regional diversity in the morphology of the H. erectus postcranium is not broadly documented, in part, because of the paucity of Asian sites preserving postcranial fossils. Yet, such an understanding of the initial hominin taxon to spread throughout multiple regions of the world is fundamental to documenting the adaptive responses to selective forces operating during this period of human evolution. Methods The current study reports the first humeral rigidity and strength properties of East Asian H. erectus and places its diaphyseal robusticity into broader regional and temporal contexts. We estimate true cross-sectional properties of Zhoukoudian Humerus II and quantify new diaphyseal properties of Humerus III using high resolution computed tomography. Comparative data for African H. erectus and Eurasian Late Pleistocene H. sapiens were assembled, and new data were generated from two modern Chinese populations. Results Differences between East Asian and African H. erectus were inconsistently expressed in humeral cortical thickness. In contrast, East Asian H. erectus appears to exhibit greater humeral robusticity compared to African H. erectus when standardizing diaphyseal properties by the product of estimated body mass and humeral length. East Asian H. erectus humeri typically differed less in standardized properties from those of side-matched Late Pleistocene hominins (e.g., Neanderthals and more recent Upper Paleolithic modern humans) than did African H. erectus, and often fell in the lower range of Late Pleistocene humeral rigidity or strength properties. Discussion Quantitative comparisons indicate that regional variability in humeral midshaft robusticity may characterize H. erectus to a greater extent than presently recognized. This may suggest a temporal difference within H. erectus, or possibly different ecogeographical trends and/or upper limb loading patterns across the taxon. Both discovery and analysis of more adult H. erectus humeri are critical to further evaluating and potentially distinguishing between these possibilities.

ELISABETTA ERBA

The Aptian-Albian Scisti a Fucoidi Formation from Central Italy represents a spectacular example of pelagic cyclic sedimentation. It consists of a varicolored sequence of marlstone, marly claystone, and marly limestone, with subordinate limestone. Several black shale layers are scattered throughout the formation. In order to clarify the mechanisms responsible for the rhythmicity, the Scisti a Fucoidi Formation was multidisciplinarly investigated in detail in the Piobbico core (Marche, Central Italy). Calcareous nannofossil assemblages were quantitatively analyzed, in three segments of the core in order to discern paleoceanographic fluctuations. These intervals were selected as representative lithologic end members characterized by three different types of cyclicity. On the basis of nannofossil assemblages, the following indices were identified: a Diagenesis Index (dissolution and overgrowth during burial), a Primary Dissolution Index (dissolution mainly at the sediment/water interface), Paleoecological Indices of higher and moderate fertility, of carbonate productivity, and of warmer and cooler waters. Within the Scisti a Fucoidi, the Upper Aptian, consisting of red lithotypes with interbedded green layers, is strongly affected by diagenesis. However, nannoconids still record fluctuations of carbonate productivity probably in a cooler more oxygenated paleoenvironment. Lowermost Albian maroon claystones with frequent interbedded black shales, are affected by extremely sever dissolution but a few episodes of increased carbonate productivity are recorded by changes in nannoconid abundance. Upper Albian greenish-gray marly limestones with cyclically modulated black shales, record slight rhythmic fluctualions in surface water fertility. Correlations between the distribution of nannofossil indices and lithology along with foraminifer and trace fossil patterns point to a response to orbital perturbations capable of triggering changes in ocean circulation, chemistry, and ecology. The rhythmic black shales of this interval probably accumulated because of an increase in stratification or decrease in oxygenation related to weaker temperature gradients and warmer waters, respectively.

M. BOCCALETTI, R. GELATI, G. MORATTI et al.

The present study has been carried out in the eastern part of the Alpujarran corridor (Betic Chain), an E-W trending basin, 80 km long, of Neogene-Quaternary age. In particular, the Ugijar and Canjayar basins (respectively named Basin 1 and Basin 2), controlled by an E-W trending left stepping right lateral strike­slip system, associated with NE-SW trending thrust faults, have been investigated. The stratigraphic sequence of the forementioned two basins, which can be up to 2000 m thick, is mainly due to tectonic subsidence and is here interpreted in terms of Sequence Stratigraphy. The age of the whole sequence, dated by means of planktonic foraminifera, is Late Serravallian-Pliocene.

PAUL A. SELDEN, JASON A. DUNLOP, LUCA SIMONETTO

A new and well-preserved fossil whip scorpion (Arachnida: Uropygi: Thelyphonida) is described from the Late Carboniferous of the Carnic Alps, Friuli, Italy. It is referred to Parageralinura marsiglioi n. sp. The new specimen is the first Carboniferous arachnid to be described from mainland Italy and is possibly the youngest Palaeozoic thelyphonid.

Kenshu Shimada, David J. Ward

The megamouth shark (Lamniformes: Megachasmidae) has sporadic occurrences both in the present-day oceans and in the fossil record. In this paper, we describe a new megachasmid, Megachasma alisonae sp. nov., on the basis of a morphologically distinct tooth collected from the Pyt Member of the late Eocene Søvind Marl Formation at Moesgård Strand in Denmark, that represents the geologically oldest known Megachasma. The tooth likely came from an individual that measured somewhere between 1.3 and 3.5 m long, and its morphology and chipped cusp tips suggest that it possibly fed on macro-zooplankton and small fishes that had hard skeletal components. Its occurrence in the mid-Priabonian Pyt Member at least suggests that the shark inhabited a relatively deep, open marine environment about 36 Ma ago. This Eocene specimen is significant because it illustrates the dental condition of early megachasmids, which is distinctively odontaspidid-like morphologically.

María Antonieta Sánchez Ríos, Pedro Salmerón Ureña

Las rocas sedimentarias del Paleógeno de México, ampliamente distribuidas en la Planicie Costera del Golfo de México, afloran en las proximidades de la Sierra Madre Oriental, así como escasamente, en la Provincia de Baja California, Coahulla y Chihuahua entre otros. Desde el punto de vista geológico, la cuenca Terciaria del Golfo de México es una unidad tectónica-sedimentaria, en la que se incluye el Golfo de México y una franja continental de aproximadamente 200m de ancho paralela a la costa. Uno de los límites de la franja es el contacto Cretácico-Paleógeno y el otro la actual línea costera del Golfo. Esta cuenca comprende la cuenca de Burgos, las cuencas de Tampico, Misantla, Veracruz, del Sureste y la plataforma de Yucatán. La columna estratigráfica del Paleógeno, en el este de la República Mexicana, incluye sedimentitas terrígenas y carbonatadas dispuestas en franjas paralelas a la línea de costa del Golfo de México, encontrándose las rocas más antiguas del Paleoceno hacia el occidente y las más recientes del Eoceno y Oligoceno hacia el oriente, sepultadas por un espesor considerable de rocas del Neógeno en las áreas de Burgos y Veracruz. En las cuencas del Sureste, las sedimentitas más antiguas se encuentran en el sur, próximas a la Sierra Madre del Sur y las más recientes se localizan en el norte, hacia el Golfo de México. El Paleoceno se encuentra representado por las biozonas de foraminíferos planctónicos: Globigerina eugubina, Morozovella pseudobulloides, M. trinidadensis, M. uncinata, M. angulata, Planorotalites pusilla pusilla, P. pseudomenardii, M. velascoensis. Mientras que por nanoplancton calcáreo, el Paleoceno Superior se caracteriza por la presencia de diferentes especies del género Fasciculithus. El Eoceno, bien representado fundamentalmente en las cuencas de Tampico-Misantla, Veracruz y en las cuencas terciarias del Sureste, se caracteriza por las biozonas de Morozovella subbotlnae, M. Formosa formosa, M. aragonensis, Acarinina pentacamerata, Hantkenina nuttalli, Globigerinatheka subconglobata, M. lehneri, Orbulinoides beckmanni, Truncorotaloides rohri, G. semiinvoluta y Globorotalia cerroazulensis, Ciertas especies de nanofósiles han sido utilizadas para subdividir el Eoceno; dentro de éstas se encuentran Discoaster lodoensis, Nanotetrina fulgens, D. saipanensis y D. barbadiensis. Las biozonas determinadas en el Oligoceno son las de Cassigerinella chipolensis, Pseudohastigerina micra, Globigerina ampliapertura, Globorotalia opima opima, Globigerina ciperoensis. La Biozona de Globorotalia kugleri de la cima del Oligoceno no se ha observado. No obstante el límite Oligo-Mioceno se ha establecido por la extinción de Sphenolithus ciperoensis. En las rocas carbonatadas del Paleógeno de la plataforma de Yucatán y de Chiapas se encuentran abundantes macroforaminíferos.

ZUOYU SUN, CRISTINA LOMBARDO, ANDREA TINTORI et al.

Two well preserved specimens of Fuyuanperleidus dengi Geng et al., 2012 are described from the Upper Member of the Guanling Formation (Pelsonian, Anisian, Middle Triassic) in Luoping County, Yunnan Province, South China. The attribution  to Perleidiformes is confirmed according to a combination of features such as the general skull pattern, with the large preoperculum showing a prominent infraorbital process, the maxilla with deep posterior region and a dentition made of  long and stout peg-like teeth with an acuminate apex, the deep mid-lateral flank scales and the caudal fin with epaxial fin rays. However, this taxon shows an unique arrangement of the squamation (here considered as autapomorphy) given by the insertion of several scales in each vertical row posterior to the pelvic fin, just below the scales carrying the lateral line, when their depth decreases abruptly. Owing to this unique character, and  in spite of the very recent description of this genus, the authors considered necessary the erection of a new family, Fuyuanperleididae offering also new insights on the evolutionary trends and morphological specializations of the “subholosteans”. A cladistic analysis of the well known perleidiformes, with this taxon included, supports a possible monophyly of the order, and matches well the paleobiogeographic relationships of the Gondwana fresh-water taxa. The specialized deep-bodied Gondwana and Tethyan perleidiformes are independently evolved, ascertained by the parsimony analysis.

Ana M. Zavattieri

Here are presented the first palynological data from the Triassic Santa Clara Arriba Formation, Santa Clara area, north of Mendoza province. 59 terrestrial species of spores and pollen grains have been identified, 9 of these species are recorded for the first time in the Triassic of Argentina.

Bert Didier, Delanoy Gérard

Research in the Feraudianus Subzone of the Sartousiana Zone of the Barremian stage led to the discovery of a new species of Pseudoshasticrioceras: P. bersaci nov. sp. Its study provides evidence concerning the developments of the latest Gassendiceratinae Bert et alii, 2006, and the relationship between the genus Pseudoshasticrioceras Delanoy, 1998, and Gassendiceras Bert et alii, 2006. In particular, this new species is derived from Pseudoshasticrioceras magnini (Delanoy, 1992) by a minor revision in the processes of ontogenesis (retardation of ornamentation - neoteny). However, the evolution towards Pseudoshasticrioceras autrani Delanoy, 1998, implies a "failure" in this process that may possibly be related to parallel changes in environmental conditions. On the other hand, the very closely defined stratigraphic position of Pseudoshasticrioceras bersaci nov. sp., and its position in the anagenetic lineage of Pseudoshasticrioceras, demonstrates its interest as a biostratigraphic marker: a new Bersaci Biohorizon is proposed; it is located between the Magnini and the Autrani biohorizons.