Hasil untuk "Paleontology"

Bernat Josep Vázquez López, Albert Sellés, Albert Prieto-Márquez et al.

Abstract Paleoenvironmental preferences for Cretaceous dinosaurs at a regional scale have been mainly assessed in North America. In south-western Europe, the dinosaur-bearing formations ranging the late Campanian to the latest Maastrichtian encompass coastal and lowland environments that produced hundreds of fossil localities with evidence of titanosaurian sauropods, maniraptoran and abelisauroid theropods, and nodosaurid ankylosaurs, together with rhabdodontid and hadrosauroid ornithopods. In order to study environmental associations of dinosaur taxa, we have revised, updated, and expanded upon an existing database that compiles the occurrence and minimum number of individuals for the dinosaur-bearing formations spanning the upper Campanian to the uppermost Maastrichtian of South-Western Europe. Based on this database, the habitat preferences of dinosaur groups in the region were determined by means of statistical tests of independence. All chi-square tests showed positive, mostly moderate-to-strong, and statistically significant associations between the studied groups and the environment they inhabited. The analysis of the residuals indicated that most dinosaur groups preferred lowland environments (including, contrary to previous studies, nodosaurids). The only exception were abelisauroids, which showed no habitat preference. Our results concur with recent works indicating that titanosaur sauropods and hadrosauroids preferred inland environments but clearly disagree with others suggesting that the latter as well as nodosaurid ankylosaurs were positively associated with marine or coastal settings. Considering the changes in occurrence distribution throughout the Maastrichtian turnover in the region, both titanosaurians and nodosaurids probably stablished a feeding strategy-based niche partitioning with ornithopods, although additional data is required to confidently confirm this relationship.

Zoë A. Roseby, Katherine Southall, Fermin Alvarez-Agoues et al.

We demonstrate the utility and reproducibility of the saltmarsh foraminifera-based ‘geological tide gauge’ (GTG) approach by developing two independent records of relative sea-level (RSL) change for Dublin, Ireland. Our records, recovered from two different saltmarshes, indicate that RSL rose at a century-scale rate of 1.5 ± 0.9 mm yr–1 over the last 200 years. This compares favourably with the shorter, but more precise, mean sea level (MSL) record from the Dublin Port tide gauge, which indicates long-term (1953–2016 CE) rise at a rate of 1.1 ± 0.5 mm yr–1. When corrected for the influence of glacio-isostatic adjustment our saltmarsh-based reconstruction suggests sea levels in Dublin rose at a rate of 1.6 ± 0.9 mm yr–1 since the start of the 19th century, which is in excellent agreement with the regional value of MSL rise over the same period (1.5 ± 0.2 mm yr–1) calculated from a compilation of tide gauge records around Britain. Whilst our record has decadal-scale temporal resolution (1 sample every 8 years), we are currently unable to resolve multidecadal-scale variations in the rate of sea-level rise which are masked by the size of the vertical uncertainties (± 20 cm) associated with our reconstruction of palaeomarsh-surface elevation. We discuss the challenges of applying the GTG approach in the typically minerogenic saltmarshes of the NE Atlantic margin and outline potential solutions that would facilitate the production of Common Era RSL reconstructions in the region.

Daniel Lima, Damares R. Alencar, William Santana et al.

Abstract Direct evidence of paleo-parasitism in crustaceans is very scarce. Epicaridean isopods are obligatory parasites of crustaceans, including decapods such as crabs, shrimps, and lobsters. Their interaction with hosts is known from fossils as far back as the Jurassic through deformations of the branchial cuticle on the hosts. Their small size and low fossilization potential, outside of those larvae that have been found in amber, makes understanding the group’s evolution challenging. Here, we report the oldest evidence of paleo-parasitism in marine shrimps and an imprint of a putative adult parasite that appears to be an epicaridean isopod. Our results suggest that the parasite–host interaction between epicaridean isopods and marine shrimps started at least 110 million years ago, and the Tethys Sea was a possible dispersal pathway for this lineage of parasites during the Jurassic and Cretaceous, as known for other marine organisms through most of the Mesozoic and Cenozoic. The oldest fossil records of bopyrid swellings associated with a large number of decapods from the Jurassic in Europe suggest that the Tethys region was a center of epicaridean distribution as a whole. Recent parasitic isopods found on dendrobranchiate shrimps are restricted to the Indo-Pacific and may represent a relict group of a lineage of parasites more widely distributed in the Mesozoic.

Nilay Govind, Mrutyunjaya Sahoo, Sankar Suresh Kumar Pillai et al.

The interest and importance of studying the reproductive strategies of Palaeozoic plants are growing. Fossil seeds play an essential role in this line of study, as they are widely described from different sedimentary formations throughout the Permian period. The Indian Permian Seed Database (IPSD) software will be an information system for ensuring the storage, safety, accessibility and recovery of the details of Indian Permian seed records in a selective manner. The current database includes 28 genera and 44 species of compressed seeds described from Lower Gondwana (Permian), with all the details for researchers. The software provides options for addition, deletion, modification and search facility. The search also includes different options (single or combination). It is a quick and organised way to look for seeds, especially on a data grid for information about seeds that have already been published in the same or different sediments. IPSD is a tool for the computer-based identification of seeds and distinguishing different genera or species within the same category. It is user-friendly and provides updated knowledge of seeds from the Lower Gondwana basins of India. It provides morphotaxonomical characters, distribution and photo documentation of seeds. The software increases accuracy through computerassisted identification of seeds. Hence, reducing and curtailing unnecessary information while describing a new species with inadequate earlier knowledge of Permian seeds.

Valentine Bouju, V. Perrichot

The paleontological interest for fossil plant resins (amber and copal) has greatly increased in the last decades, as field studies have resulted in the discovery of various new deposits worldwide. Yet, amber-rich deposits remain particularly scarce on continents from former Gondwana. Here we review the known occurrences of copal and amber from Africa, with a state-of-the-art regarding the age dating, the putative plant sources, the fossil content, as well as the paleoenvironmental settings. The first African ambers known to yield arthropods and other organismal inclusions, found recently from the early Cretaceous of Congo and the Miocene of Ethiopia, are briefly overviewed.

Christopher R.C. Paul

“Pan-dichoporites” (new informal term) is proposed to unite Cambrian blastozoans, such as Cambrocrinus, Ridersia, and Sanducystis, glyptocystitoid and hemicosmitoid rhombiferans, coronates, blastoids, and Lysocystites. Pan-dichoporite ambulacra have double biserial main axes with brachiole facets shared by pairs of floor (glyptocystitoids), side (blastoid) or trunk (hemicosmitoids, coronates) plates. These axial plates are the first two brachiolar plates modified to form the ambulacral axes. In glyptocystitoids the first brachiole facet in each ambulacrum is shared by an oral and another plate. Hence, these are also two modified brachiolar plates and part of the axial skeleton under the Extraxial Axial Theory (EAT). Pan-dichoporites are also characterized by thecae composed of homologous plate circlets. The unique glyptocystitoid genus Rhombifera bears ambulacral facets on five radial plates, which alternate with five orals. The oral area of Lysocystites (blastoid sensu lato) is very similar, which suggests that rhombiferan radials are homologous with “ambulacrals” of Lysocystites and hence with blastoid lancet plates. This implies derivation of blastoids from glyptocystitoids and suggests that blastoid and coronate radials and deltoids are homologous with rhombiferan infralaterals and laterals. Thus, homologous plate circlets occur in all pan-dichoporites, which strengthens the validity of a pan-dichoporite clade. Under Universal Elemental Homology (UEH), deltoids were homologized with rhombiferan orals, but this is inconsistent with the EAT. Deltoids bear respiratory pore structures and so are perforate extraxial skeletal plates, whereas rhombiferan orals are axial skeleton. The new plate homologies also explain why only five plates form the oral frames of coronates, blastoids and Lysocystites, whereas glyptocystitoids (except Rhombifera) have six oral frame plates; all glyptocystitoids have only five laterals. Hemicosmitoids arose by paedomorphic ambulacral reduction, but the paedomorphosis also affected the thecal plates and stem. Paedomorphosis poses special problems for cladistic character analysis, since the new characters often appear to be plesiomorphic.

ADRIANA LÓPEZ-ARBARELLO, MARTIN EBERT

Late Jurassic marine vertebrates are extraordinarily well preserved in several Plattenkalk Lagerstätten in central Europe. Among them, the Solnhofen Archipelago has yielded the very rare fish Coccolepis bucklandi, which was the first fossil chondrostean to be found in sediments younger than the Triassic. The type specimen of this species was lost, but it was rediscovered recently, prompting the alpha taxonomic revision of this iconic fish. A new species Coccolepis solnhofensis has been identified among the specimens referred to C. bucklandi. The two species differ in the distinctive distribution of scutes and fringing fulcra. Based on the available evidence, C. bucklandi is restricted to the Eichstätt Basin and the Lithacoceras eigeltingense ß Horizon of the Lithacoceras riedense Subzone (Hybonoticeras hybonotum Zone), and C. solnhofensis sp. nov. is limited to the Solnhofen Basin and the slightly younger Subplanites rueppellianus Subzone (Hybonoticeras hybonotum Zone). Therefore, the two species are geographically and stratigraphically separated. The diagnosis of Coccolepis is improved with the addition of new characters, and the genus is here restricted to the two early Tithonian species from the Solnhofen Archipelago. Among the four species previously described or referred to Coccolepis, the generic assignment of “Coccolepis” australis and “Coccolepis” liassica, remains unclear. Sunolepis yumenensis is here returned to its original genus, and the new combination Condorlepis woodwardi is proposed for this Early Cretaceous coccolepidid from Australia.

PAOLO MIETTO

A slab with the tetrapod footprints Rhynchosauroides cf. schochardti (R. von Lilienstern, 1939) is described from the Werfen Fm. of Recoaro area (Vicentinian Alps). The slab is coming from red siltitic facies of the "Monte Naro Breccias" (Upper Scythian — Lower Anisian ? sedimentary cicles).

Jens C.D. Kosch, Lindsay E. Zanno

Dietary habits in extinct species cannot be directly observed; thus, in the absence of extraordinary evidence, they must be reconstructed with a combination of morphological proxies. Such proxies often include information on dental organization and function such as tooth formation time and tooth replacement rate. In extinct organisms, tooth formation times and tooth replacement rate are calculated, in part via extrapolation of the space between incremental lines in dental tissues representing daily growth (von Ebner Line Increment Width; VEIW). However, to date, little work has been conducted testing assumptions about the primary data underpinning these calculations, specifically, the potential impact of differential sampling and data extrapolation protocols. To address this, we tested a variety of intradental, intramandibular, and ontogentic sampling effects on calculations of mean VEIW, tooth formation times, and replacement rates using histological sections and CT reconstructions of a growth series of three specimens of the extant archosaurian Alligator mississippiensis. We find transect position within the tooth and transect orientation with respect to von Ebner lines to have the greatest impact on calculations of mean VEIW—a maximum number of VEIW measurements should be made as near to the central axis (CA) as possible. Measuring in regions away from the central axis can reduce mean VEIW by up to 36%, causing inflated calculations of tooth formation time. We find little demonstrable impact to calculations of mean VEIW from the practice of subsampling along a transect, or from using mean VEIW derived from one portion of the dentition to extrapolate for other regions of the dentition. Subsampling along transects contributes only minor variations in mean VEIW (<12%) that are dwarfed by the standard deviation (SD). Moreover, variation in VEIW with distance from the pulp cavity likely reflects idiosyncratic patterns related to life history, which are difficult to control for; however, we recommend increasing the number of VEIW measured to minimize this effect. Our data reveal only a weak correlation between mean VEIW and body length, suggesting minimal ontogenetic impacts. Finally, we provide a relative SD of mean VEIW for Alligator of 29.94%, which can be used by researchers to create data-driven error bars for tooth formation times and replacement rates in fossil taxa with small sample sizes. We caution that small differences in mean VEIW calculations resulting from non-standardized sampling protocols, especially in a comparative context, will produce inflated error in tooth formation time estimations that intensify with crown height. The same holds true for applications of our relative SD to calculations of tooth formation time in extinct taxa, which produce highly variable maximum and minimum estimates in large-toothed taxa (e.g., 718–1,331 days in Tyrannosaurus).

J. Baross, S. Hoffman

Timothy P. Cleland, Elena R. Schroeter

Christopher J. Dunmore, G. Wollny, M. Skinner

Paleontological research increasingly uses high-resolution micro-computed tomography (μCT) to study the inner architecture of modern and fossil bone material to answer important questions regarding vertebrate evolution. This non-destructive method allows for the measurement of otherwise inaccessible morphology. Digital measurement is predicated on the accurate segmentation of modern or fossilized bone from other structures imaged in μCT scans, as errors in segmentation can result in inaccurate calculations of structural parameters. Several approaches to image segmentation have been proposed with varying degrees of automation, ranging from completely manual segmentation, to the selection of input parameters required for computational algorithms. Many of these segmentation algorithms provide speed and reproducibility at the cost of flexibility that manual segmentation provides. In particular, the segmentation of modern and fossil bone in the presence of materials such as desiccated soft tissue, soil matrix or precipitated crystalline material can be difficult. Here we present a free open-source segmentation algorithm application capable of segmenting modern and fossil bone, which also reduces subjective user decisions to a minimum. We compare the effectiveness of this algorithm with another leading method by using both to measure the parameters of a known dimension reference object, as well as to segment an example problematic fossil scan. The results demonstrate that the medical image analysis-clustering method produces accurate segmentations and offers more flexibility than those of equivalent precision. Its free availability, flexibility to deal with non-bone inclusions and limited need for user input give it broad applicability in anthropological, anatomical, and paleontological contexts.

İZZET HOŞGÖR, İSMAİL ÖMER YILMAZ

The finding of Aphrodina dutrugei (Cocquand, 1862) in a rich collection of non-rudist bivalve fauna from the famous Cenomanian-Turonian carbonates of the Afro-Arabian Plate has permitted the reevaluation of venerid bivalves during an important period of their evolution. The genus Aphrodina Conrad, 1869, Family Veneridae Rafinesque, 1815, embraces several Tethyan Cretaceous species that range from Cenomanian to Santonian. During the late Albian-Maastrichtian ‘Aphrodiniid’ venerids, were distributed along the western margin of the Atlantic (North and South America), the Afro-Arabian Plate (Jordan, SE Turkey, Morocco, Algeria and Egypt), the eastern Tethys, and the Southern Ocean (India, Japan, western Australia and New Zealand). They are also known in the Turonian-Santonian Trans-Saharan Seaway (Gabon). Until now these fossils have been unknown in any Upper Cretaceous localities of southeastern Turkey. In this paper, we report the first record of one of the most common and widespread shallow infaunal species, Aphrodina dutrugei, in the Cenomanian Derdere Formation in the Mardin-Mazıdağı area, SE Turkey, which is in the extreme northeastern part of its known range.

Da-Qing Li, Chang-Fu Zhou, Lan Li et al.

Chronostratigraphic correlation of terrestrial Early Cretaceous biotas in China is highly problematic due to the lack of marine deposits, few absolute dates, and limited number of index fossils. This often leaves vertebrate faunas as one of the few potential tools for a preliminary biostratigraphy. Taxonomic identity of fragmentary fossils is, however, often uncertain and many faunas are insufficiently sampled. Turtles are one of the most common elements of Early Cretaceous biotas of Asia and their skeleton is frequently preserved more completely than that of other vertebrates- they yet receive little attention from vertebrate paleontologists. We here record the presence of the sinemydid turtle Ordosemys leios from the Lower Cretaceous Mengyin Formation of Shandong Province, China, best known for the first dinosaurs and Mesozoic turtles described from the country. Ordosemys is the third turtle reported from the Mengyin Formation along with Sinemys lens and Sinochelys applanata and the only other formation where Ordosemys is known to co-occur with Sinemys is the Luohandong Formation of the Ordos Basin (Inner Mongolia), the type and so far only horizon of Ordosemys leios. The presence of the crocodyliform Shantungosuchus may further define a fauna that is so far only known from these two formations. The stratigraphic position of the Luohandong Formation is poorly controlled and it has been placed anywhere between the Valanginian and Aptian. Published absolute dates from the Mengyin Formation and the numerous shared vertebrate and invertebrate taxa (now also including turtles) implies a Valanginian—early Hauterivian age for the Luohandong Formation—in contrast to late Hauterivian-Albian as previously proposed using the temporal distribution of Psittacosaurus. The new specimen of Ordosemys leios preserves the only known manus of this species and ecomorphological analysis of limb proportions implies that it was a less capable swimmer compared to Ordosemys liaoxiensis coming from the younger Jehol Biota.

Laurence Bourguignon, J. Crochet, R. Capdevila et al.

A. Drummond, O. Pybus, A. Rambaut et al.

O. H. Walliser

Shufang Wang, D. Dong, Yuman Wang et al.

H. Poinar, M. Höss, J. Bada et al.