Trilobite biostratigraphy of the Králův Dvůr Formation (upper Katian, Prague Basin, Czech Republic): global faunal changes or facies-related distribution?

Eight trilobite associations and sub-associations have been distinguished in the late Katian Králův Dvůr Formation. Spatial distribution of these associations reflects lithology but their succession was dictated also by global climatic changes and palaeogeographical positioning. Locally developed “Podolí Ore Horizon” trilobite association contains low-diversity but specific forms showing survivals from the underlying Bohdalec Formation combined with the late Katian taxa (Chlustinia, Duftonia, Onnia, etc.). The Amphitryon – Kloucekia Association is newly established for the lower two thirds of the formation. It is characterized by abundant benthic scavenger-predators accompanied by filter feeders and common pelagic/nektic predators. Within Amphitryon –Kloucekia Association can be distinguished four sub-Association 1) the newly established Onnia ultima sub-Association is characterized by a dominance of Onnia and Flexicalymene; it is developed at the lowermost levels of the formation, 2) the deeper-water Nankinolithus granulatus sub-Association (originally established as horizon), 3) rather shallow-water, brachiopod-dominated Dedzetina-Tretaspis sub-Association with rare trilobites and 4) the trilobite-dominated Tretaspis anderssonni sub-Association (originally horizon). Last three sub-associations are considered as rather facies-related, with limited stratigraphical applicability only. Impure bioclastic limestone below top of the formation contains a rich shallow- and temperate-water Marekolithus kosoviensis Association, which better corresponds with the original horizon concept. This association is dominated by small benthic scavenger-predator trilobites, which are associated by the filter feeder Marekolithus. The Mucronaspis Association of medium-sized scavenger-predators is characteristic for the uppermost portion of formation and persisted till the early onset of the glaciation at the base of Hirnantian. Minute detritus feeders are rare but present in all the above-discussed associations excluding the last one

Fossiles cambriens de la région barrandienne (République tchèque) conservés au Musée d'Histoire Naturelle de Lille

A complete list of fossils originating from the Cambrian of the Barrandian area and housed in the Musée d'Histoire Naturelle de Lille is compiled. The collection includes two agnostids, ten trilobites, one brachiopod and one echinoderm species, all collected at ten outcrops in the Buchava Formation of the Skryje-Týřovice Basin and most probably also at two outcrops in the Jince Formation of the Příbram-Jince Basin. A large part of the material was collected by Prof. Charles Barrois and Dr. Louis Dollé (both University of Lille) during the excursion organised before the Ninth International Geological Congress in Vienna in 1903. Other, poorly documented specimens were purchased from the enterprise Krantz towards the end of the 19th century and in the first years of 20th century. The geographic position and stratigraphy of outcrops, from which the material originates, are briefly discussed.Une liste complète des fossiles provenant du Cambrien de la région barrandienne déposés au Musée d'Histoire Naturelle de Lille a été établie. La collection comprend deux espèces d'agnostidés, dix trilobites, un brachiopode et un échinoderme ; les fossiles récoltés dans dix affleurements proviennent tous de la Formation Buchava du bassin de Skryje-Týřovice et probablement également de deux affleurements de la Formation Jince du bassin de Příbram-Jince. Une grande partie du matériel a été récoltée par le Professeur Charles Barrois et par le Dr. Louis Dollé (de l'Université de Lille) au cours de l'excursion organisée avant le VIIIème Congrès géologique national à Vienne en 1903. Les autres spécimens, mal documentés, ont été achetés à l'entreprise Krantz à la fin de 19ème siècle et dans les premières années du 20ème siècle. La situation géographique et la stratigraphie des affleurements d'où provient le matériel sont brièvement discutées

Cambrian and Ordovician Fossil-Lagerstätten in the Barrandian area

Exceptionally preserved fossils showing typical characters of the so called Konservat-Lagerstätten are shortly mentioned from Cambrian and Ordovician sediments of the Barrandian area. Fossils with well preserved soft parts were ascertained in several different levels of two Cambrian units of the Příbram-Jince Basin as well as in diverse levels of the Skryje-Týřovice Basin. Other exceptionally preserved fossils are shortly discussed from numerous Lower to Upper Ordovician levels of the Prague Basin

Photometry of the Didymos System across the DART Impact Apparition

On 2022 September 26, the Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, the satellite of binary near-Earth asteroid (65803) Didymos. This demonstrated the efficacy of a kinetic impactor for planetary defense by changing the orbital period of Dimorphos by 33 minutes. Measuring the period change relied heavily on a coordinated campaign of lightcurve photometry designed to detect mutual events (occultations and eclipses) as a direct probe of the satellite’s orbital period. A total of 28 telescopes contributed 224 individual lightcurves during the impact apparition from 2022 July to 2023 February. We focus here on decomposable lightcurves, i.e., those from which mutual events could be extracted. We describe our process of lightcurve decomposition and use that to release the full data set for future analysis. We leverage these data to place constraints on the postimpact evolution of ejecta. The measured depths of mutual events relative to models showed that the ejecta became optically thin within the first ∼1 day after impact and then faded with a decay time of about 25 days. The bulk magnitude of the system showed that ejecta no longer contributed measurable brightness enhancement after about 20 days postimpact. This bulk photometric behavior was not well represented by an HG photometric model. An HG 1 G 2 model did fit the data well across a wide range of phase angles. Lastly, we note the presence of an ejecta tail through at least 2023 March. Its persistence implied ongoing escape of ejecta from the system many months after DART impact

Identification methods of genetically related asteroids

In this thesis, I describe the main ideas and summarize the results of four refereed papers I contributed to (three times as the second author and once as the first author). The first step of each of these papers was the identification of genetically related asteroid and their membership confirmation. Since members of asteroid pairs and clusters have a very similar heliocentric orbits, we employed and further developed methods based on backward orbital integrations. The chronologically first paper Pravec et al. (2018) deals with asteroid clusters and their similarity to asteroid pairs. The second paper Pravec et al. (2019) is a complex study of 93 asteroid pairs with many interesting results, such as the existence of binary asteroids among asteroid pairs. The third paper Moskovitz et al. (2019) deals with an identification of asteroid pairs in the near-Earth population and a detail study of two probable asteroid pairs. The fourth paper, Fatka et al. (2020), studies the phenomenon of cascade disruption in asteroid clusters, which results in multiple generations (with different ages) of escaped secondaries in some asteroid clusters

Metody identifikace geneticky souvisejících planetek

V této práci popisuji hlavní myšlenky a shrnuji výsledky čtyř publikovaných článků na kterých jsem se podílel (třikrát jsem uveden jako druhý autor a jednou jako hlavní autor článku). Prvním krokem každého z těchto čtyř článků bylo vytipování geneticky spřízněných planetek a potvrzení jejich příslušnosti k danému planetkovému páru nebo klastru. Vzhledem k tomu, že členové jednotlivých planetkových párů a klastrů se nacházejí na velmi podobných drahách, použili jsme metody založené na zpětných dráhových integracích, které jsme přizpůsobili danému konkrétnímu problému. První článek (Pravec a kol., 2018 ) se zabývá planetkovými klastry a jejich podobností s planetkovými páry. Druhý článek (Pravec a kol., 2019) obsahuje rozsáhlou studii 93 planetkových párů s mnoha zajímavými výsledky, například výskyt binárních asteroidů v planetkových párech. Třetí článek (Moskovitz a kol., 2019) zkoumá možnosti nalezení planetkových párů v populaci blízkozemních planetek a obsahuje podrobnou studii dvou pravděpodobných blízkozemních párů. Čtvrtý článek (Fatka a kol., 2020) zkoumá výskyt kaskádních rozpadů v planetkových klastrech. Tyto rozpady vedou ke vzniku několika generací sekundárních těles.In this thesis, I describe the main ideas and summarize the results of four refereed papers I contributed to (three times as the second author and once as the first author). The first step of each of these papers was the identification of genetically related asteroid and their membership confirmation. Since members of asteroid pairs and clusters have a very similar heliocentric orbits, we employed and further developed methods based on backward orbital integrations. The chronologically first paper Pravec et al. (2018) deals with asteroid clusters and their similarity to asteroid pairs. The second paper Pravec et al. (2019) is a complex study of 93 asteroid pairs with many interesting results, such as the existence of binary asteroids among asteroid pairs. The third paper Moskovitz et al. (2019) deals with an identification of asteroid pairs in the near-Earth population and a detail study of two probable asteroid pairs. The fourth paper, Fatka et al. (2020), studies the phenomenon of cascade disruption in asteroid clusters, which results in multiple generations (with different ages) of escaped secondaries in some asteroid clusters.Matematicko-fyzikální fakultaFaculty of Mathematics and Physic

Sheltered preservation in Ordovician trilobites

Articulated holaspid specimens of Placoparia Hawle and Corda, 1847and Eoharpes Raymond, 1905 entombed inside cephalopod conchs and under the remainsof large illaenid, asaphid, cyclopygid and dalmanitid trilobites from theMiddle Ordovician Šárka Formation of the Prague Basin (CzechRepublic) are described and discussed. Two such samples were also found inthe overlying Dobrotivá Formation of Middle/Late Ordovician age. Fourarticulated juvenile exoskeletons of Placoparia preserved under a cephalon of thecyclopygid trilobite Degamella Marek, 1961 represent the first record of shelterstrategy of non-holaspid trilobites. The sheltered preservation oftrilobites could be explained by a hiding behaviour associated with thedanger of predation, storm disturbances, seeking for food or highvulnerability after moulting. It is obvious that Placoparia and Eoharpes deliberately enteredthe restricted space under skeletal parts of large trilobites or insidecephalopod conchs. These exceptional finds provide a new insight in the lifestrategy of some Ordovician benthic trilobites and are classified as casesof “frozen” behaviour

REMAINS OF THE ALIMENTARY TRACT IN THE LATE ORDOVICIAN TRILOBITE <em>DALMANITINA</em> (PRAGUE BASIN, BARRANDIAN AREA, CZECH REPUBLIC)

Preservation of digestive structures in trilobites is generally rare; remains of the alimentary tract have been documented in about eighty of more than twenty thousand described species. Several tens of specimens belonging to five Cambrian and nine Ordovician species from the Barrandian area, Czech Republic, have markedly contributed to the knowledge of the trilobite digestive system. Here, we describe seven exceptionally preserved late holaspid trilobite specimens of species of the genus Dalmanitina collected from Upper Ordovician strata of the Barrandian area. All studied specimens are preserved as internal moulds and exhibit a narrow strip-like structure that runs sagitally or sub-sagitally under the axial lobe of the thoracopygon. These strip-like structures are markedly different from scavenger burrows and are interpreted as remains of the alimentary canal. A slightly expanded anterior-most part of the digestive system is preserved in the cephalic shield of six specimens and is interpreted as a remainder of the anterior midgut. A dark area is seen in the glabellar lobes of three specimens. These dark areas do not represent pyrite concentrations in the hypostome–glabellar cavity, because they contain only small amounts of Fe and S. These areas are interpreted as the remainder of cephalic digestive midgut diverticula, or the “perigastric organ”. Quantitative chemical analyses show that in species of Dalmanitina the digestive system is preserved as dark matter containing partly digested food particles and most probably also a higher amount of clay minerals. The described specimens constitute the first well-documented example of digestive structures in the subfamily Dalmanitininae.