Hasil untuk "Paleontology"

Jennifer Swerida, Eli N. Dollarhide, Eric Fouache et al.

The Bat landscape of northwestern Oman is one of intermittent archaeological remains and varied ecological conditions. The site has been a center for human activity since the Neolithic, most famously attested by the Early Bronze Age tombs, towers, and settlement of the UNESCO World Heritage zone. This paper presents recent research conducted by the Bat Archaeological Project in reconstructing the site’s third millennium BC cultural landscape and the human-environment interactions that led to its creation and long-term occupation. Three of Bat’s Early Bronze Age environs: the Settlement Slope, al-Khutm, and Rakhat al-Madrh are discussed in view of their ecological, geomorphological, and archaeological contexts. New archaeobotanical and 14C results are presented. These discoveries suggest Bat’s ancient inhabitants sought out and utilized diverse environments in order to establish cultural and ecological resilience within a localized area. Ultimately, we propose an expansion to the traditional oasis model of settlement and agricultural development in southeast Arabia, arguing for a systems-based approach that incorporates roles played by environs beyond the oasis.

Marcelo Adrián Martínez, María Virginia Bianchinotti, María Elina Cornou

Spores, conidiophores, and hyphae of fossil fungi recovered from nine outcropping siltstone and shale samples belonging to the Troncoso, Salto del Macho, and Río Foyel formations in the El Foyel Group at the Río Foyel Section, are described and illustrated. Representatives of 16 genera were recognized. Among the 26 species described, one is proposed as a new species, Inapertisporites lacrimaformis. Amerospores are the most abundant type of spores recovered. Based on the palynostratigraphical analysis of the non-pollinic (fungal) remains, a Paleogene age for the El Foyel Group is suggested. Of the three formations, Troncoso shows the highest abundance and diversity of fungal remains, which is believed to be representative of a period of optimal climatic conditions characterized as warm temperate and humid, probably related to the Middle Eocene Climate Optimum (MECO). Based on the paleoeological preferences of the specimens recovered from the El Foyel Group, a riparian or lacustrine environment in a woodland setting is inferred.

Robert Weis, Dominique Delsate, Christian Klug et al.

Abstract A re-examination of the early Toarcian fish fossils preserved in public paleontological collections in Luxembourg revealed 70 specimens of large Toarcian pachycormid fish with an excellent three-dimensional preservation within calcareous nodules. Six of them are associated with octobrachian coleoid gladii in their oesophagus or stomach, an association not previously described from Luxembourg. The pachycormids are ascribed to Pachycormus macropterus (Blainville, 1818) and Saurostomus esocinus Agassiz, 1843 while the octobrachian gladii are ascribed to Teudopsis bollensis Voltz, 1836, Teudopsis sp. indet. and Loligosepiidae indet. The position and orientation of the gladii provide direct evidence of these fishes feeding on coleoids and thus a teuthophagous diet, rather than an accidental joint burial. Together with evidence from coeval deposits in Germany, these findings suggest that teuthophagy was a widespread feeding strategy at the base of the clade that contains the suspension-feeding pachycormid giants of the Jurassic–Cretaceous.

Yan Wu, Yong Ge, Han Hu et al.

Abstract Angiosperms became the dominant plant group in early to middle Cretaceous terrestrial ecosystems, coincident with the timing of the earliest pulse of bird diversification. While living birds and angiosperms exhibit strong interactions across pollination/nectivory, seed dispersal/frugivory, and folivory, documentation of the evolutionary origins and construction of that ecological complexity remains scarce in the Mesozoic. Through the first study of preserved in situ dietary derived phytoliths in a nearly complete skeleton of the early diverging avialan clade Jeholornithidae, we provide direct dietary evidence that Jeholornis consumed leaves likely from the magnoliid angiosperm clade, and these results lend further support for early ecological connections among the earliest birds and angiosperms. The broad diet of the early diverging avialan Jeholornis including at least fruits and leaves marks a clear transition in the early evolution of birds in the establishment of an arboreal (angiosperm) herbivore niche in the Early Cretaceous occupied largely by birds today. Morphometric reanalysis of the lower jaw of Jeholornis further supports a generalized morphology shared with other herbivorous birds, including an extant avian folivore, the hoatzin.

A. D. AHLUWALIA, V.J. GUPTA, K. J. BUDUROV et al.

The present paper describes the lower Upper Devonian conodont fauna from the upper units of Muth Formation, Spiti Valley, Himalaya.

Wu, Ka Yan, Heuck, Jared, Varriale, Frank J. et al.

The Mesaverde Formation of the Wind River and Bighorn basins of Wyoming preserves a rich yet relatively unstudied terrestrial and marine faunal assemblage dating to the Campanian. To date, turtles within the formation have been represented primarily by isolated fragments diagnostic only to broader clades. A baenid specimen from the lower third of the Mesaverde Formation in the northwestern Bighorn Basin of Park County, Wyoming, includes a partial carapace and plastron and is the most complete turtle specimen yet described from the formation. The entire carapace would have been around 450 mm long and 380 mm wide, indicating a fairly large individual. The preserved portions of the carapace are smooth and unornamented, and the overall oval dorsal profile of the shell is similar to taxa such as Neurankylus spp. The anterior plastral lobe in the new specimen is squared off in profile as seen in Neurankylus spp., unlike the more rounded or triangular condition in Boremys spp., Eubaena hatcheri, and Baena spp., among others. The likely omega-shaped femoral-anal sulcus differs from the condition in Neurankylus spp., better matching the condition seen in many (but not all) Baenodda, although only one half of the fossil preserves the sulcus, and it may lie within expected variation for Neurankylus. Based on the overall combination of features in this Mesaverde Formation specimen, we tentatively assign it to Neurankylus sp., the first report for this taxon as well as Baenidae in the Mesaverde Formation of the Bighorn Basin.

Michael Krings

Windipila spinifera from the Rhynie cherts is a spheroidal microfossil enveloped in a hyphal mantle from which extend prominent spines and otherwise shaped projections. It is believed to be a reproductive unit of a fungus in the Glomeromycota or zygomycetes, but features to determine the systematic affinities have not hitherto been documented. This study describes a new specimen of W. spinifera that contains a single spherical structure from which a hypha arises that extends outside and terminates in what appears to be a sporangium. The specimen is reminiscent of germinated zygospores of the germ-sporangial type, and thus may suggest affinities of W. spinifera to the zygomycetes. However, the interior sphere and its outgrowth could also be a part of another organism that had invaded W. spinifera.

Kumiko Matsui, Kumiko Matsui, Yuri Kimura et al.

Recent innovations and cost reductions in photogrammetry-based 3D modeling have enabled museum visitors to create 3D models based on photographs exhibited in galleries without breaking museum policies. While several museums make 3D museum data available on sharing platforms, museum visitors publish unofficial 3D data belonging to museum exhibits using a photogrammetry-based approach. This study shows that photogrammetry-based 3D models can be generated without breaking conventional photo policies (i.e., no use of flash and tripods) and that museum visitors can create commercial products based on these models. 3D models certainly enhance scientific value and promote broader and deeper interests in the natural sciences; however, the rights of owners of museum pieces are ambiguous with regard to the dissemination of unofficial data. This also makes information attributable to the original specimen unclear, which can potentially lead to revenue loss. We propose a set of best practices for museum photo policies covering the data use of visitor-generated 3D models of displayed objects.

Beatrice Demarchi, Meaghan Mackie, Zhiheng Li et al.

Previously, we showed that authentic peptide sequences could be obtained from 3.8-Ma-old ostrich eggshell (OES) from the site of Laetoli, Tanzania (Demarchi et al., 2016). Here, we show that the same sequences survive in a >6.5 Ma OES recovered from a palaeosteppe setting in northwestern China. The eggshell is thicker than those observed in extant species and consistent with the Liushu Struthio sp. ootaxon. These findings push the preservation of ancient proteins back to the Miocene and highlight their potential for paleontology, paleoecology, and evolutionary biology.

Joseph E. Peterson, Z. Jack Tseng, Shannon Brink

Background Bite marks attributed to adult Tyrannosaurus rex have been subject to numerous studies. However, few bite marks attributed to T. rex have been traced to juveniles, leaving considerable gaps in understanding ontogenetic changes in bite mechanics and force, and the paleoecological role of juvenile tyrannosaurs in the late Cretaceous. Methods Here we present bite force estimates for a juvenile Tyrannosaurus rex based on mechanical tests designed to replicate bite marks previously attributed to a T. rex of approximately 13 years old. A maxillary tooth of the juvenile Tyrannosaurus specimen BMR P2002.4.1 was digitized, replicated in dental grade cobalt chromium alloy, and mounted to an electromechanical testing system. The tooth was then pressed into bovine long bones in various locations with differing cortical bone thicknesses at varying speeds for a total of 17 trials. Forces required to replicate punctures were recorded and puncture dimensions were measured. Results Our experimentally derived linear models suggest bite forces up to 5,641.19 N from cortical bone thickness estimated from puncture marks on an Edmontosaurus and a juvenile Tyrannosaurus. These findings are slightly higher than previously estimated bite forces for a juvenile Tyrannosaurus rex of approximately the same size as BMR P2002.4.1 but fall within the expected range when compared to estimates of adult T. rex. Discussion The results of this study offer further insight into the role of juvenile tyrannosaurs in late Cretaceous ecosystems. Furthermore, we discuss the implications for feeding mechanisms, feeding behaviors, and ontogenetic niche partitioning.

Thomas M. Claybourn, Christian B. Skovsted, Marissa J. Betts et al.

Cambrian Series 2 shelly fossils from thick carbonate successions in East Antarctica have received limited systematic treatment through the 20th century. Described here are the East Antarctic camenellan tommotiids from the Shackleton Limestone in the Central Transantarctic Mountains and the Schneider Hills limestone in the Argentina Range. This material comes from both newly sampled collections and incompletely described material from older collections. The assemblage supports correlation to the Dailyatia odyssei Zone and Pararaia janeae Trilobite Zone of South Australia, with the newly examined specimens of Dailyatia decobruta from the Shackleton Limestone providing direct correlation to the Mernmerna Formation of the Ikara-Flinders Ranges and White Point Conglomerate of Kangaroo Island. These East Antarctic assemblages include five species referred to Dailyatia, in addition to an undetermined kennardiid species and fragments of the problematic Shetlandia multiplicata. The results further corroborate the notion that fossiliferous carbonate clasts found on King George Island were sourced from the same carbonate shelf as the Shackleton Limestone, with the taxon S. multiplicata found in both units. The Schneider Hills limestone in the Argentina Range has yielded sclerites of Dailyatia icari sp. nov., currently only known from this location.

Saeedeh Senemari, Farah Jalili

Abstract Data obtained from the calcareous nannofossils, distributed in the upper part of the Pabdeh Formation (Priabonian–Rupelian) and the lower part of the Asmari Formation (Chattian) in the Bid-Zard section, were used to investigate the Eocene to Oligocene palaeoenvironmental conditions in the southwest of Izeh, southwestern Iran (eastern Tethys). The upper part of the Pabdeh Formation was composed of shale, thin-bedded pelagic limestone and dolostone, which is disconformably overlain by the Asmari Formation. For the first time, 29 species of calcareous nannofossils belonging to 13 genera were identified in the studied section. The calcareous nannofossils in the upper part of the Pabdeh Formation indicate the Isthmolithus recurvus Zone/Sphenolithus pseudoradians Zone (combined zone), Ericsonia subdisticha Zone, Helicosphaera reticulata Zone and Sphenolithus praedistentus Zone, from the Priabonian to the Rupelian. The Sphenolithus ciperoensis Zone of the Chattian was identified in the lower part of the Asmari Formation. Calcareous nannofossil stratigraphy across the upper Eocene–Oligocene interval also reveals a disconformity at the Rupelian/Chattian transition due to a bio-event. Shallowing of the basin and environmental changes in this part of the Tethyan domain could have led to the lithostratigraphic and biostratigraphic changes. In fact, during the late Eocene to late Oligocene, marine phytoplankton was sensitive to climate changes such as decreasing temperature, as well as possibly to a nutrient increase and changes in basin depth.

Paco Cárdenas

Siliceous spicules in demosponges exist in a variety of shapes, some of which look like minute spheres of glass. They are called “sterrasters” when they belong to the Geodiidae family (Tetractinellida order) and “selenasters” when they belong to the Placospongiidae family (Clionaida order). Today, the Geodiidae represent a highly diverse sponge family with more than 340 species, occurring in shallow to deep waters worldwide, except for the Antarctic. The molecular phylogeny of Geodiidae is currently difficult to interpret because we are lacking morphological characters to support most of its clades. To fill this knowledge gap, the surface microornamentations of sterrasters were compared in different genera. Observations with scanning electron microscopy revealed four types of surfaces, which remarkably matched some of the Geodiidae genera: type I characteristic of Geodia, type II characteristic of Pachymatisma, Caminus, and some Erylus; type III characteristic of other Erylus; type IV characteristic of Caminella. Two subtypes were identified in Geodia species: warty vs. smooth rosettes. These different microornamentations were mapped on new Geodiidae COI (Folmer fragment) and 28S (C1–D2) phylogenetic trees. The monophyly of the Geodiidae was once again challenged, thereby suggesting that sterrasters have evolved independently at least three times: in the Geodiinae, in the Erylinae and in Caminella. Surface microornamentations were used to review the fossil record of sterrasters and selenasters through the paleontology literature and examination of fossils. It was concluded that “rhaxes” in the literature may represent mixes of sterrasters and selenasters: while Rhaxella spicules may belong to the Placospongiidae, Rhaxelloides spicules belong to the Geodiidae. The putative Geodiidae fossil genera, Geoditesia, and Geodiopsis, are reallocated to Tetractinellida incertae sedis. Isolated Miocene-Pliocene fossil sterrasters Hataina (Huang, 1967), Silicosphaera (Hughes, 1985) and Conciliaspongia (Robinson and Haslett, 1995) become junior synonyms of Geodia (Lamarck, 1815). Overall, the fossil record suggested that Geodiidae was present at least since the Middle Jurassic (163–166 Mya), while Geodia sterrasters were present since the Santonian/Campanian boundary, Late Cretaceous (83.6 Mya).ZooBank Article Registrationurn:lsid:zoobank.org:pub:91B1B3AC-8862-4751-B272-8A3BDF4DEE77.

Peter J. Bishop, Scott A. Hocknull, Christofer J. Clemente et al.

This paper is the last of a three-part series that investigates the architecture of cancellous bone in the main hindlimb bones of theropod dinosaurs, and uses cancellous bone architectural patterns to infer locomotor biomechanics in extinct non-avian species. Cancellous bone is highly sensitive to its prevailing mechanical environment, and may therefore help further understanding of locomotor biomechanics in extinct tetrapod vertebrates such as dinosaurs. Here in Part III, the biomechanical modelling approach derived previously was applied to two species of extinct, non-avian theropods, Daspletosaurus torosus and Troodon formosus. Observed cancellous bone architectural patterns were linked with quasi-static, three-dimensional musculoskeletal and finite element models of the hindlimb of both species, and used to derive characteristic postures that best aligned continuum-level principal stresses with cancellous bone fabric. The posture identified for Daspletosaurus was largely upright, with a subvertical femoral orientation, whilst that identified for Troodon was more crouched, but not to the degree observed in extant birds. In addition to providing new insight on posture and limb articulation, this study also tested previous hypotheses of limb bone loading mechanics and muscular control strategies in non-avian theropods, and how these aspects evolved on the line to birds. The results support the hypothesis that an upright femoral posture is correlated with bending-dominant bone loading and abduction-based muscular support of the hip, whereas a crouched femoral posture is correlated with torsion-dominant bone loading and long-axis rotation-based muscular support. Moreover, the results of this study also support the inference that hindlimb posture, bone loading mechanics and muscular support strategies evolved in a gradual fashion along the line to extant birds.

Hesham M. Sallam, Erik R. Seiffert

The Fayum Depression of Egypt has yielded fossils of hystricognathous rodents from multiple Eocene and Oligocene horizons that range in age from ∼37 to ∼30 Ma and document several phases in the early evolution of crown Hystricognathi and one of its major subclades, Phiomorpha. Here we describe two new genera and species of basal phiomorphs, Birkamys korai and Mubhammys vadumensis, based on rostra and maxillary and mandibular remains from the terminal Eocene (∼34 Ma) Fayum Locality 41 (L-41). Birkamys is the smallest known Paleogene hystricognath, has very simple molars, and, like derived Oligocene-to-Recent phiomorphs (but unlike contemporaneous and older taxa) apparently retained dP4∕4 late into life, with no evidence for P4∕4 eruption or formation. Mubhammys is very similar in dental morphology to Birkamys, and also shows no evidence for P4∕4 formation or eruption, but is considerably larger. Though parsimony analysis with all characters equally weighted places Birkamys and Mubhammys as sister taxa of extant Thryonomys to the exclusion of much younger relatives of that genus, all other methods (standard Bayesian inference, Bayesian “tip-dating,” and parsimony analysis with scaled transitions between “fixed” and polymorphic states) place these species in more basal positions within Hystricognathi, as sister taxa of Oligocene-to-Recent phiomorphs. We also employ tip-dating as a means for estimating the ages of early hystricognath-bearing localities, many of which are not well-constrained by geological, geochronological, or biostratigraphic evidence. By simultaneously taking into account phylogeny, evolutionary rates, and uniform priors that appropriately encompass the range of possible ages for fossil localities, dating of tips in this Bayesian framework allows paleontologists to move beyond vague and assumption-laden “stage of evolution” arguments in biochronology to provide relatively rigorous age assessments of poorly-constrained faunas. This approach should become increasingly robust as estimates are combined from multiple independent analyses of distantly related clades, and is broadly applicable across the tree of life; as such it is deserving of paleontologists’ close attention. Notably, in the example provided here, hystricognathous rodents from Libya and Namibia that are controversially considered to be of middle Eocene age are instead estimated to be of late Eocene and late Oligocene age, respectively. Finally, we reconstruct the evolution of first lower molar size among Paleogene African hystricognaths using a Bayesian approach; the results of this analysis reconstruct a rapid latest Eocene dwarfing event along the lineage leading to Birkamys.

I. A. Starodubtseva, I. L. Soroka

Valeriyan (Valerian) Alexandrovich Kipriyanov (1818-1889) is one of the first national paleontologists. He published articles with descriptions and illustrations of the examined by him the remains of Chondrichthyes and Osteichthyes from the Upper Crelaceous of Kurskaya and Orlovskaya provinces. He became an author of four monographies about Jurassic and Cretaceous reptiles. His scientific biography has not been published up to the present moment despite his considerable scientific achievements. His biographic data was restricted by two issues [5, 9], the texts of which in many ways repeated each other. This article represents new facts of V.A. Kipriyanov biography, information about his collections. The full bibliography of his paleontological works is given in References.

Imran A. Rahman, Selena Y. Smith

‘Virtual paleontology’ entails the use of computational methods to assist in the three-dimensional (3-D) visualization and analysis of fossils, and has emerged as a powerful approach for research on the history of life. Three-dimensional imaging techniques allow poorly understood or previously unknown anatomies of fossil plants, invertebrates, and vertebrates, as well as microfossils and trace fossils, to be described in much greater detail than formerly possible, and are applicable to a wide range of preservation types and specimen sizes (Table 1). These methods include non-destructive high-resolution scanning technologies such as conventional X-ray micro-tomography and synchrotron-based X-ray tomography. In addition, form and function can be rigorously investigated through quantitative analysis of computer models, for example finite-element analysis.

Michael Manga, Matthew J. Hornbach, Anne Le Friant et al.

Using temperature gradients measured in 10 holes at 6 sites, we generate the first high fidelity heat flow measurements from Integrated Ocean Drilling Program drill holes across the northern and central Lesser Antilles arc and back arc Grenada basin. The implied heat flow, after correcting for bathymetry and sedimentation effects, ranges from about 0.1 W/m2 on the crest of the arc, midway between the volcanic islands of Montserrat and Guadeloupe, to <0.07 W/m2 at distances >15 km from the crest in the back arc direction. Combined with previous measurements, we find that the magnitude and spatial pattern of heat flow are similar to those at continental arcs. The heat flow in the Grenada basin to the west of the active arc is 0.06 W/m2, a factor of 2 lower than that found in the previous and most recent study. There is no thermal evidence for significant shallow fluid advection at any of these sites. Present‐day volcanism is confined to the region with the highest heat flow.

Luciano Fogaça de Assis Montag, Tiago Magalhães da Silva Freitas, Wolmar Benjamin Wosiacki et al.

In order to survey the poorly known fish fauna of the National Forest Caxiuanã, located in the municipalities of Melgaço and Portel, Pará State, Brazil, collections were made between 1999 and 2004, encompassing all distinguishable environments and employing different collecting methods. These methods included: blocking streams, enclosure nets for floating aquatic macrophytes, gill nets, snorkeling, and occasional collections. Among a total of 208 species collected, there was a predominance of Characiformes (81 species), followed by Siluriformes, Perciformes and Gymnotiformes with 46, 35and 25 species, respectively. These species were distributed in three main environments, (i) small streams, (ii) floating vegetation, and (iii) open waters of rivers and bays in Caxiuanã, showing that environmental complexity contributes to the highly diversified ichthyofauna in the study area. According with to Jackknife estimator of 1st order and the rarefaction curves, the number of estimated species was much higher for theses three types of environment, than the species observed, which for streams was estimate of at 51 of ± 6 species, 70 ± 5 for macrophyte banks and 160 ± 11 for the edges of rivers and bays. These results demonstrate the relative efficiency of the sampling, appointing the necessity of new collects for these environments.