Cephalopods from reef limestone of the Vasalemma Formation, northern Estonia (latest Sandbian, Upper Ordovician) and the establishment of a local warm-water fauna

The cephalopods of the reef limestones of the Vasalemma Formation, northern Estonia, are highly diverse and comprise 22 species belonging to 10 families and seven orders in a sample of >300 specimens. Most of the specimens were collected from shell concentrations in synsedimentary cavities and are interpreted as parautochthonous, washed in from nearby habitats. Nearly all of the shells are fragmented and nearly 15% are partially encrusted by epibionts. The assemblage is dominated by small (mostly less than 30mm wide), straight-shelled actinocerids and orthocerids; in addition, coiled tarphycerids are common. The high-level taxonomic composition of the Vasalemma cephalopod assemblage, with a dominance of actinocerids and an absence of endocerids, is in agreement with deposition in a warm-water (tropical or subtropical), shallow, subtidal regime. At the species level the assemblage is highly endemic, but the generic composition allows for a statistical comparison with other faunas. A cluster analysis of contemporary assemblages reveals a high degree of similarity with late Sandbian cephalopod faunas of epicontinental Laurentia. The palaeogeographical distribution pattern is similar to that of brachiopods, which supports earlier interpretations of these clusters as mainly controlled by water temperature and depositional depth. Several of the Vasalemma genera became conspicuous elements of epicontinental Laurentia during the Katian, which emphasizes that immigration towards Laurentia was an important factor in Late Ordovician diversity dynamics. Of the described taxa, the following are new: Beloitoceras cautis sp. nov., Curtoceras abditus sp. nov., Hemibeloitoceras arduum sp. nov., H. molis sp. nov., Hoeloceras muroni sp. nov., Isorthoceras cavi sp. nov., I. maris sp. nov., I. padisense sp. nov., I. vexilli sp. nov., Ordogeisonoceras tartuensis sp. nov., Orthonybyoceras isakari sp. nov., O. moisense sp. nov., Pleurorthoceras organi sp. nov., Rummoceras rummuensis gen. et sp. nov. and Trocholites gennadii sp. nov.http://zoobank.org/urn:lsid:zoobank.org:pub:E5211305-A5D0-4366-AAB1-08F96F817122Peer reviewe

Vybraní hlavonožci (Cephalopoda) ordoviku pražské pánve a Baltiky(Estonsko a Švédsko): taxonomie, paleobiogeografie a paleoekologie

Předkládaná dizertační práce shrnuje pět článků publikovaných v recenzo- vaných, impaktovaných odborných časopisech. Články jsou taxonomickými re- vizemi dříve neznámých nebo málo známých kolekcí fosilních hlavonožců ze spodního paleozoika Čech, Estonska a Švédska. Práce shrnují a zpřesňují pa- leogeografické a stratigrafické rozšíření jednotlivých taxonů a srovnávají jej s rozšířením podobně starých hlavonožcových tafocenóz známých z jiných oblastí. Tafocenózy jsou následně analyzovány a paleoekologicky interpretovány. Dizertační práce se sestává ze tří hlavních částí. První část je zaměřena na morfologii hlavonožců a uvádí základní diagnostické znaky, které se při popisu hlavonožců používají. Shrnuje také dosavadní názory na systematiku hlavonožců a stručně představuje hlavní skupiny významné pro období ordoviku. Druhá část práce charakterizuje geologické podmínky a vývoj oblastí, ze kterých studovaní hlavonožci pocházejí. Třetí a poslední část pak shrnuje výsledky publikovaných studií. Ze středního ordoviku pražské pánve byli studováni rod Bactroceras a dále zástupci řádu Lituitida. Rod Bactroceras Holm, 1898 je stratigraficky nejstarším známým zástupcem...This dissertation thesis is a summary of five studies published in peer- reviewed, impacted scientific journals. All of the publications are taxonomic revisions of previously unknown or little known collections of fossil cephalopods from the Early Paleozoic strata of Bohemia, Estonia and Sweden. Paleogeogra- phical and stratigraphical distributions of the respective taxa were summarized, refined and compared with contemporary fossil assemblages known from other regions. Implications on the paleoecology of the cephalopods and original envi- ronmental conditions were made. The text of the thesis is divided into three main parts. In the first part, the morphology of cephalopods is explained, stressing out the most important diagnostic characters used for their descriptions. The current systematics of the Cephalopoda is overviewed and the main cephalopod groups during the Ordovician are briefly introduced. The second part of the thesis describes the geological development and settings of the regions, from which the studied fossil cephalopods originate. The third and final part of the thesis provides a discussion and interpretation of the results of the published studies in the context of the previously published research. The genus Bactroceras Holm, 1898 and some members of the order Litui- tida were studied...Ústav geologie a paleontologieInstitute of Geology and PaleontologyPřírodovědecká fakultaFaculty of Scienc

The cephalopods of the Kullsberg Limestone Formation, Upper Ordovician, central Sweden and the effects of reef diversification on cephalopod diversity

The cephalopods collected from the mud mounds of the Kullsberg Limestone Formation, late Sandbian-earliest Katian(?), south central Sweden, are highly diverse and comprise 26 identifiable species of 12 families and six orders in a sample of c. 180 specimens. The assemblage is strongly dominated by orthocerids in abundance and diversity. In contrast, the time-equivalent assemblage of the reef limestone of the Vasalemma Formation of Estonia is dominated by actinocerids and less diverse. Only one-third of the species co-occur in these two palaeogeographically relatively close assemblages. The taxonomic composition of the Kullsberg assemblage is, on the order level, more similar to that of the late Katian-early Hirnantian Boda Limestone Formation of south central Sweden, which represents a similar relatively deep depositional environment. The high local differentiation of cephalopod reef faunas exemplifies the importance of the emergent Baltic reef habitats in diversification processes during the early Late Ordovician. Of the described taxa, the following are new: Beloitoceras thorslundi sp. nov., Cameroceras motsognir sp. nov., Clothoceras thornquisti gen. et sp. nov., Danoceras skalbergensis sp. nov., Discoceras amtjaernense sp. nov., D. nilssoni sp. nov., Endoceras naekki sp. nov., Furudaloceras tomtei gen. et sp. nov., Isbergoceras consobrinum gen. et sp. nov., I. niger gen. et sp. nov., Isorthoceras nikwis sp. nov., I. sylphide sp. nov., I. urdr sp. nov., I. verdandi sp. nov., Kullsbergoceras nissei gen. et sp. nov., Ordogeisonoceras uppsalaensis sp. nov. and Valkyrioceras dalecarlia gen et sp. nov.Peer reviewe

Three-dimensionally preserved siphuncle in an actinoceratid cephalopod from the late Katian of Bohemia

The Ordovician to Carboniferous cephalopods of the order Actinoceratida (Teichert, 1933) are distinguished from all other cephalopods by their large siphuncles, which typically contain heavy, calcareous deposits enclosing a complex system of canals. These peculiar structures were already recognised in the 19th century, but it was only in the 20th century that they were properly described and interpreted in a more systematic manner with respect to the phylogeny and palaeoecology of the group. In the present study, we investigate a uniquely preserved actinoceratid cephalopod from the late Katian part of the Králův Dvůr Formation (Prague Basin, Central Bohemia), in order to address the magnificent works of C. Teichert, R. H. Flower, M. Wade and H. Mutvei. The specimen, tentatively assigned to the ormoceratidan genus Adamsoceras, consists of four isolated fragments of the siphuncle (nine siphuncular segments) and small remains of phragmocone chambers. All original calcareous parts of the conch were dissolved during diagenesis and fossilisation processes, while the spaces left by decayed soft tissues were filled with pyrite (secondarily converted into limonite). In other words, the specimen is a cast of the axial canal, radial canals and perispatium, plus some remains of phragmocone chambers. Cavities inside the cast mirror the shape of dissolved endosiphuncular deposits and ectosiphuncle; nothing is preserved of the outer shell wall and septa. The remains of phrag­mocone chambers are diagenetically flattened, but the siphuncle is undeformed, supposedly because it was protected against compaction by the extensive endosiphuncular deposits and possibly by the filling of the endosiphuncular canals with pyrite. The preservation of the specimen enabled the application of the micro-CT scanning. This non-destructive method has proved invaluable for studying fossils that cannot be otherwise studied using standard oriented sectioning. It also enabled the construction of a virtual model of the specimen, which facilitated the investigation of the siphuncular structure in 3D. Preliminary results show that the endosiphuncular deposits grew unevenly, resulting in highly irregular shapes and distribution of the radial canals, and an irregularly flattened form of the central canal. The flattening of the central canal is interpreted as reflecting the dorso-ventral plane of sym­metry of the siphuncle. Furthermore, the endosiphuncular structures did not form symmetrically and their appearance depends on the selected median section. This suggests that the distinction between several types of endosiphuncular systems sensu Teichert and Flower and the taxonomy derived from these distinctions might be, at least in some actinoceratids, artificial, resulting from studying specimens in 2D median sections. The studied specimen represents the only unequivocal actinoceratid from the Ordovician of the high-palaeolatitude Prague Basin. Since actinoceratid cephalopods were abundant during the Ordovician mainly in low-palaeolatitude carbonate environments, the presence of this specimen in the Prague Basin supports previous indications of a faunal connection between the high and low palaeolatitudes during the late Katian age

Early cephalopod evolution clarified through Bayesian phylogenetic inference

Background: Despite the excellent fossil record of cephalopods, their early evolution is poorly understood. Different, partly incompatible phylogenetic hypotheses have been proposed in the past, which reflected individual author's opinions on the importance of certain characters but were not based on thorough cladistic analyses. At the same time, methods of phylogenetic inference have undergone substantial improvements. For fossil datasets, which typically only include morphological data, Bayesian inference and in particular the introduction of the fossilized birth-death model have opened new possibilities. Nevertheless, many tree topologies recovered from these new methods reflect large uncertainties, which have led to discussions on how to best summarize the information contained in the posterior set of trees. Results: We present a large, newly compiled morphological character matrix of Cambrian and Ordovician cephalopods to conduct a comprehensive phylogenetic analysis and resolve existing controversies. Our results recover three major monophyletic groups, which correspond to the previously recognized Endoceratoidea, Multiceratoidea, and Orthoceratoidea, though comprising slightly different taxa. In addition, many Cambrian and Early Ordovician representatives of the Ellesmerocerida and Plectronocerida were recovered near the root. The Ellesmerocerida is para- and polyphyletic, with some of its members recovered among the Multiceratoidea and early Endoceratoidea. These relationships are robust against modifications of the dataset. While our trees initially seem to reflect large uncertainties, these are mainly a consequence of the way clade support is measured. We show that clade posterior probabilities and tree similarity metrics often underestimate congruence between trees, especially if wildcard taxa are involved. Conclusions: Our results provide important insights into the earliest evolution of cephalopods and clarify evolutionary pathways. We provide a classification scheme that is based on a robust phylogenetic analysis. Moreover, we provide some general insights on the application of Bayesian phylogenetic inference on morphological datasets. We support earlier findings that quartet similarity metrics should be preferred over the Robinson-Foulds distance when higher-level phylogenetic relationships are of interest and propose that using a posteriori pruned maximum clade credibility trees help in assessing support for phylogenetic relationships among a set of relevant taxa, because they provide clade support values that better reflect the phylogenetic signal.Peer reviewe

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

Selected cephalopods from the Ordovician of the Prague Basin (Bohemia) and Baltica (Estonia and Sweden): taxonomy, paleobiogeography and paleoecology

This dissertation thesis is a summary of five studies published in peer- reviewed, impacted scientific journals. All of the publications are taxonomic revisions of previously unknown or little known collections of fossil cephalopods from the Early Paleozoic strata of Bohemia, Estonia and Sweden. Paleogeogra- phical and stratigraphical distributions of the respective taxa were summarized, refined and compared with contemporary fossil assemblages known from other regions. Implications on the paleoecology of the cephalopods and original envi- ronmental conditions were made. The text of the thesis is divided into three main parts. In the first part, the morphology of cephalopods is explained, stressing out the most important diagnostic characters used for their descriptions. The current systematics of the Cephalopoda is overviewed and the main cephalopod groups during the Ordovician are briefly introduced. The second part of the thesis describes the geological development and settings of the regions, from which the studied fossil cephalopods originate. The third and final part of the thesis provides a discussion and interpretation of the results of the published studies in the context of the previously published research. The genus Bactroceras Holm, 1898 and some members of the order Litui- tida were studied..

The use of diatoms (Bacillariophyta) in paleolimnology

This thesis is a literature review summarizing methodology and the possibility of use of diatoms (Bacillariophyta) for paleoecological reconstructions of extinct lacustrine ecosystems. In addition, the theoretical part of the thesis is devoted to basic characteristics, evolutionary history and ecology of the group, lakes and the fossil record. In the practical part, two samples of sediments of a fossil lake that has been discovered and studied within the Morava Project in Strážnické Pomoraví are compared

Taxonomic position of the species Bactroceras sandbergeri (Barr.,1867) from the Czech Ordovician

Taxonomic position of the cephalopod Bactroceras sandbergeri (Barr., 1867) from the Ordovician of the Prague Basin was subjected to wide discussions and disputes in the past. The species was first classified within the genus Bactrites. Later, a separate, monotypic genus Eobactrites was defined. At present, the species is assigned to the genus Bactroceras. It belongs to the family Baltoceratidae, the genera of which are supposed to represent the oldest orthoceridans. The order Orthocerida is one of the most successful and most diversified cephalopod groups of the Paleozoic Era. In this thesis, a revision of Bactroceras sandbergeri has been made after a detailed study of about one hundred specimens. Attention was paid to those features, that are missing in the original species descriptions or that were neglected in the past. Special attention was paid mainly to muscle scars, structure of the siphuncle and morphology of the embryonic shell. The embryonic shell was originally described as Tretoceras parvulum Barrande, 1868. In addition, Orthoceras naufragum Barrande, 1870 was synonymized with the studied species and the species Orthoceras interpolatum Barrande, 1870 was assigned to the genus Bactroceras. Key words: Cephalopoda, Ordovician, Czech Republic, Barrandian are

Selected cephalopods from the Ordovician of the Prague Basin (Bohemia) and Baltica (Estonia and Sweden): taxonomy, paleobiogeography and paleoecology

This dissertation thesis is a summary of five studies published in peer- reviewed, impacted scientific journals. All of the publications are taxonomic revisions of previously unknown or little known collections of fossil cephalopods from the Early Paleozoic strata of Bohemia, Estonia and Sweden. Paleogeogra- phical and stratigraphical distributions of the respective taxa were summarized, refined and compared with contemporary fossil assemblages known from other regions. Implications on the paleoecology of the cephalopods and original envi- ronmental conditions were made. The text of the thesis is divided into three main parts. In the first part, the morphology of cephalopods is explained, stressing out the most important diagnostic characters used for their descriptions. The current systematics of the Cephalopoda is overviewed and the main cephalopod groups during the Ordovician are briefly introduced. The second part of the thesis describes the geological development and settings of the regions, from which the studied fossil cephalopods originate. The third and final part of the thesis provides a discussion and interpretation of the results of the published studies in the context of the previously published research. The genus Bactroceras Holm, 1898 and some members of the order Litui- tida were studied..