The term "genal caeca" refers to branching and anastomosing ridges developed with varying intensity on free and fixed cheeks and preglabellar field in many trilobites, including the trilobites from Barrandian area of the Czech Republic. This diploma thesis presents the first detailed study of the morphology of genal caeca preserved on cephalons of Cambrian trilobite genera Ptychoparia Hawle & Corda, 1847, Mikaparia Kordule, 2006 and Conocoryphe Hawle & Corda, 1847 from Příbram-Jince and Skryje-Týřovice basins of the Barrandian area. Based on a detailed morphological description and measurements, separate fields of genal caeca occurrence were defined and frequency of their preservation on the studied specimens was compared. The variability of the number of ridges in each field and the frequency of their preservation do not show any convincing connection with cranidial size of the specimens or the locality. Keywords: trilobites, Barrandian area, genal caeca

A morphometric analysis of Cambrian trilobites shows that extinction events sharply reduced the morphological diversity of ptychopariid trilobites living on the shelf at the lower boundaries of the Marjumiid, Pterocephaltid, and Ptychaspid biomeres (Middle to Upper Cambrian). These extinction events not only separate the trilobite assemblages that characterize each biomere, but they also separate similar sequences of morphological diversification. During the initial deposition of each biomere, the shelf was repopulated by a limited number of ptychopariid species that had similar morphologies of very limited range and type. These initial faunas then underwent a morphological diversification evolving similar morphologies during the deposition of the remainder of each biomere. This pattern of repeating episodes that begin with similar morphologies of trilobites which then undergo similar morphological diversifications suggests that the extinction events at the base of each biomere limited the range of morphologies from which new taxa could evolve. Each new biomere assemblage was unable to build upon the adaptations of the specialized taxa of the previous biomere. Only the limited range of similar morphologies of the initial repopulating trilobites was the source from which new taxa could evolve. As a result, new taxa “reevolved the wheel” each time they became adapted to the vacated habitats that were previously occupied in the underlying biomere. In contrast, near the Cambrian-Ordovician boundary, the extinction event at the base of the Lower Ordovician Symphysurinid biomere did not reduce the range of morphologies as drastically as the previous biomere extinctions in the Cambrian. A more diverse initial fauna occurs in the Symphysurinid biomere. This fauna did not undergo a morphological diversification during deposition of the biomere and some regions of morphospace previously occupied in the Cambrian were not reoccupied in this biomere. Taxa of the lower Ordovician were relatively canalized in their morphology. In the Marjumiid biomere (Middle to lower Upper Cambrian), the morphological diversification of ptychoparid trilobites was not significantly influenced by either paleogeography, depositional settings, or migration of taxa from outside North America. The morphological diversification of the ptychopariid assemblage is also seen in a subset of ptychopariids that consists of the Superfamilies Raymondinacea, Asaphiscacea, and Marjumiacea. These superfamilies are the numerically abundant and most diverse taxonomic groups in the Marjumiuid biomere. The patterns of morphological diversification in both the Order Ptychopariida and the combined assemblages of the Superfamilies Raymondinacea, Asaphiscacea, and Marjumiacea were relatively consistent among different paleogeographic regions and were not influenced by general lithofacies. The consistency of the regional patterns and the lack of influence of general lithofacies on these patterns indicate that the overall pattern of morphological diversification is the result of in situ evolution of taxa within the North American Craton and not the result of shifting biofacies or the migration of taxa from outside North America. The morphological diversification of ptychoparids in the Marjumiid Biomere is composed of two distinct phases. The morphological expansion of the Superfamily Ptychopariacea (the ehmaniellids) in the Ehmaniella Biozone is an early phase of diversification. The morphological expansion of the Superfamilies Norwoodiacea, Solenopleuracea (exclusive of the Family Solenopleuracea), Asaphiscacea, Raymondinacea, and Marjumiacea in the Bolaspidella to Crepicephalus biozones represent the later phase of diversification. This second phase is also composed of two morphological expansions, an early expansion in the Superfamilies Norwoodiacea and Solenopleuracea in the Bolaspidella and Cedaria biozones, and a later expansion in the Superfamilies Asaphiscacea, Raymondinacea, and Marjumiacea in the Cedaria and Crepicephalus biozones. The ptychopariid assemblages of the younger Ptychaspid biomere (Upper Cambrian) also display a two-phase morphological diversification. / Ph. D.

Trilobites were a successful group of marine arthropods that thrived for much of the Palaeozoic Era. Akey innovation of trilobites involved the capacity to enrol their biomineralized exoskeletons for protection; a trait that appeared early in their evolutionary history during the Cambrian Period. However, even though there has been much interest in the description of enrolment-related anatomical adaptations, and different styles of enrolment, the kinematic aspect has just begun to be explored—not just as means of understanding trilobite movements, but also as a potential driver of evolution. In this study, with the use of the open-source software Blender, four models of three different species of Ordovician trilobites(two phacopines and two illaenines) were constructed and later submitted to enrolling simulations. Different angle metrics were measured and then compared between simulations to analyse the performance of the developed methodology, and between the different models to reveal potential evolutionary or developmental trends. Results suggest a clear relationship between the kind of higher-level taxonomic groups analysed and the angle arrangement of the trunk elements in an enrolled position. In contrast, the same was not as evident when comparing the measured angle metrics against the total number of segments. Illaenina models consistently resulted in lower angles between segments required to enrol, suggesting a more efficient enclosure of the body favoured by bigger and more spherical proportions of cephalon and pygidium. This study contributes to a growing field in palaeontology and provides new, detailed enrolment data for several trilobite species. In future, such data should be synthesized with those from previous and future studies to analyse the evolutionary and developmental history of trilobites from this novel perspective.

<p>Arthropods have a rich fossil record spanning the Phanerozoic. Biomineralized forms such as the extinct trilobites are particularly common and are proven index fossils for biostratigraphy. Forms with an unmineralized cuticle are more rare, preserved only in so called <i>konservat lagerstätten</i>. Cambrian strata of Greenland have yielded rich trilobite faunas with potential for intercontinental correlation of Cambrian strata, but also an exceptionally preserved fauna, the Sirius Passet Lagerstätte. The first part of this thesis is concerned with trilobite biotratigraphy of the provisional Cambrian Series 2 in Greenland. The second part is concerned with exceptionally preserved arthropods from the Sirius Passet Lagerstätte, but also from 'Orsten' deposits from the Cambrian of Sweden.</p><p><i>Perissopyge phenax occurs</i> in the Henson Gletscher and Paralleldal formations spanning the Series 2 and 3 boundary interval in North Greenland. It also occurs in the Sekwi Formation of Yukon Territory, demonstrating that the species may hold potential for correlation within Laurentia. An indeterminate species of <i>Perissopyge</i> is shown to occur in the Ella Island Formation of North-East Greenland together with <i>Olenellus</i> cf. <i>hanseni</i>, which is similar to <i>Olenellus</i> cf. <i>truemani</i> described from the Henson Gletscher Formation. If this correlation is further corroborated it would offer a first tie-point for the An t'Sron Formation of North-West Scotland which yields <i>Fritzolenellus</i> <i>lapworthi</i>, herein reported for the first time from the Bastion Formation which underlies the Ella Island Formation.</p><p><i>Oelandocaris</i> <i>oelandica</i> from ‘Orsten’ deposits in the Cambrian series 3 and 4 boundary interval in Sweden is an early representative of the Crustacean stem lineage. <i>Kiisortoqia</i> <i>avannaarsuensis</i> is a new arthropod from the Sirius Passet Lagerstätte with robust antennulae strikingly similar to the 'raptorial' limb of the problematic anomalocaridids. The ventral morphology of the 'bivalved' <i>Isoxys</i> <i>volucris</i> is described for the first time and compared with other species assigned to <i>Isoxys</i> from Cambrian lagerstätten around the world. Finally, <i>Siriocaris</i> <i>trolla</i>, is a new arthropod that similarities with trilobites and certain ‘trilobitomorphs’ but seems to lack important synapomorphies of these taxa, though this may be due to preservational limitations in the material at hand.</p>

Arthropods have a rich fossil record spanning the Phanerozoic. Biomineralized forms such as the extinct trilobites are particularly common and are proven index fossils for biostratigraphy. Forms with an unmineralized cuticle are more rare, preserved only in so called konservat lagerstätten. Cambrian strata of Greenland have yielded rich trilobite faunas with potential for intercontinental correlation of Cambrian strata, but also an exceptionally preserved fauna, the Sirius Passet Lagerstätte. The first part of this thesis is concerned with trilobite biotratigraphy of the provisional Cambrian Series 2 in Greenland. The second part is concerned with exceptionally preserved arthropods from the Sirius Passet Lagerstätte, but also from 'Orsten' deposits from the Cambrian of Sweden. Perissopyge phenax occurs in the Henson Gletscher and Paralleldal formations spanning the Series 2 and 3 boundary interval in North Greenland. It also occurs in the Sekwi Formation of Yukon Territory, demonstrating that the species may hold potential for correlation within Laurentia. An indeterminate species of Perissopyge is shown to occur in the Ella Island Formation of North-East Greenland together with Olenellus cf. hanseni, which is similar to Olenellus cf. truemani described from the Henson Gletscher Formation. If this correlation is further corroborated it would offer a first tie-point for the An t'Sron Formation of North-West Scotland which yields Fritzolenellus lapworthi, herein reported for the first time from the Bastion Formation which underlies the Ella Island Formation. Oelandocaris oelandica from ‘Orsten’ deposits in the Cambrian series 3 and 4 boundary interval in Sweden is an early representative of the Crustacean stem lineage. Kiisortoqia avannaarsuensis is a new arthropod from the Sirius Passet Lagerstätte with robust antennulae strikingly similar to the 'raptorial' limb of the problematic anomalocaridids. The ventral morphology of the 'bivalved' Isoxys volucris is described for the first time and compared with other species assigned to Isoxys from Cambrian lagerstätten around the world. Finally, Siriocaris trolla, is a new arthropod that similarities with trilobites and certain ‘trilobitomorphs’ but seems to lack important synapomorphies of these taxa, though this may be due to preservational limitations in the material at hand.

The mixed carbonate–siliciclastic Abrigo Formation of middle and late Cambrian age, which crops out in southeastern Arizona, was deposited during the Sauk transgression in the craton interior, landward of the passive margin of Laurentia. The Abrigo Formation consists of ten basic rock types: claystone, siltstone, sandstone, lime mudstone, wackestone, bioclastic grainstone, packstone, oolitic packstone, oncolitic packstone, and intraclastic conglomerate. These comprise fifteen lithofacies, which are grouped into eight facies associations. They represent an array of shallow-marine environments that were dominated by wave and storm activity. The interpreted paleoenvironments include lower offshore, upper offshore, offshore transition, and lower, middle and upper shoreface. One hundred eighty-two collections, yielding 940 trilobite remains have been found in the Abrigo Formation. They represent 69 species and 42 genera. Eight of the species are new. The fossil age ranges from early Marjuman to late Steptoean. Eight trilobite biofacies are defined from the generic relative abundance data: Ehmaniella, Olenoides–Bolaspidella, Blairella, Eldoradia, Modocia–Paracedaria, Cedaria, Coosella–Coosina, and Camaraspis. Trilobites collected and identified in this study are assigned to five biostratigraphic zones: Bolaspidella, Cedaria, Crepicephalus, Aphelaspis, and Elvinia zones. In addition, two subzones had been defined. Cedaria eurycheilos Subzone recognized in the upper part of Cedaria Zone and Coosella helena Subzone recognized in the upper part of Crepicephalus Zone. The stratigraphic succession was divided into six distinct phases associated with large-scale relative sea-level fluctuations. An initial flooding over the Bolsa Quartzite forming the transgressive systems tract was terminated by maximum flooding, and a subsequent highstand systems tract developed during Bolaspidella Biozone time. The second sequence starts with another transgressive systems tract, and is overlain by a final highstand systems tract during the Cedaria and Crepicephalus biozones. The uppermost part of the second sequence represents a falling stage systems tract that developed during Aphelaspis Biozone time. The presence of Elvinia Biozone trilobites near the base of the highest sandstone unit suggests that delivery and deposition of these sands took place during the lowstand that followed the protracted and widespread Sauk II–Sauk III hiatus. Sedimentary dynamics were controlled by storm-induced wave action and offshore flows. There are two carbonate factories that operated simultaneously in this Cambrian inner shelf region. Dominance of carbonate versus siliciclastic strata in the offshore transition setting is interpreted to reflect periods when siliciclastic input was depleted, such that increasing accommodation and reduction of clay and possibly nutrients promoted carbonate production. Clay and silt bypassed the nearshore carbonate-depositing zone. Siliciclastic sediment input and dispersal were not only restricted to the falls in sea level, but appear to have dominated the transgressive systems tract and late phase of the highstand. Thus, carbonate sedimentation does not dominate the entire highstand systems tract as is commonly held but, rather, only during the late phase of the transgressive and early highstand phase. The comparison of this Cambrian model with younger mixed carbonate-siliciclastic units will help reveal the subtleties of the carbonate factory and how it operated in response to biotic evolution.

This thesis deals with the ontogeny of trilobites and agnostids from the Cambrian of the Skryje-Týřovice and Příbram-Jince basins (Barrandian area, Bohemian Massif). Thesis is presented as a compilation of four papers that were published in scientific peer-reviewed journals. The introduction of the thesis serves as a general overview of the trilobite post- embryonic development and connects all published papers together. All four papers presented here are focussed on modern description of the post-embryonic development of Sao hirsuta, Ptychopariida sp. A, Ptychopariida sp. B, Ptychopariida sp. C, Ellipsocephalus hoffi, Ellipsocephalus polytomus, Hydrocephalus carens and Ecca- paradoxides pusillus. In addition, a discussion about the life-history strategies of early developmental trilobite stages is presented. It has been suggested that Sao hirsuta and Ptychopariida sp. A had benthic protaspides and that the early ontogenetic stages of Ptychopariida sp. B, Eccaparadoxides pusillus and Hydrocephalus carens were likely lecithortophic. Consequently, it has been documented that species with benthic protaspides show a strongly restricted geographic distribution and that lecithotrophic taxa seem to be associated with higher latitude areas. The developmental patterns of Ellipsocephalus hoffi and...

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The Solenopleurid trilobite Sao hirsuta Barrande, 1846 is known from "Middle" Cambrian sedimentary rocks of the Czech Republic, Germany and Spain. It is one of the first trilobites on which ontogenetic development was described in detail (Barrande, 1852). This diploma thesis is the first modern revision of the ontogeny of this species for more than fifty years. Thesis is primarily based on quantitative methods and a detailed study of morphology of the exoskeleton. Changes in the dorsal exoskeleton during ontogenetic development of S. hirsuta, including the discovery of intrainstar morphological and size variability and the transition from isometric growth to the alometric growth, were described in detail by using quantitative methods (biometric measurements and geometric morphometrics). In the protaspid period different instars of S. hirsuta were recognized. Detailed morphological studies revealed several different morphotypes of protaspid stages. Some of which may represent different taxa. The morphology and the condition of the hypostome was described, including changes of hypostome during ontogeny. The study of segmentation in the species S. hirsuta shows hypoprotomeric development with the initial accumulation phase, middle equilibrium phase and terminal depletion phases. Key words: Sao...