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Fantasticolithus isabelae, a new genus and species of trinucleid trilobite from the Lower Ordovician of Peru, developed anterior ventral cephalic 'props' that are unique in the Trilobita. Its broad and finely pitted genal prolongations are unlike those of any previously known trinucleid, and closely resemble those invariably present in the unrelated Family Harpetidae, supporting the hypothesis that the two families shared a similar mode of life, as 'trinucleimorphs'. Fantasticolithus was probably derived from an early trinucleid with a marginal girder, although it resembles younger genera such as Marrolithus in its enlarged anterolateral pits. The new genus provides a natural experiment to test the hypothesis of trinucleimorphs as filter feeders that used a ventral feeding chamber. The role of the pitted marginal fringe as an egress for feeding currents is discussed. Fantasticolithus had an unusual anterior vent that provided a simpler exit mechanism for feeding currents than the pitted fringe. However, the pits were probably important for trinucleids that lacked an anterior arch. [ABSTRACT FROM AUTHOR]

The Fezouata Lagerstätte, discovered in the Lower Ordovician rocks of Morocco, is a Konservat‐Lagerstätte of prime scientific importance. It provides access not only to the ‘shelly’ (skeletonized) part of its fossil assemblages, but also to non‐biomineralized to lightly sclerotized organisms and to exceptionally preserved soft tissues of a complex ecosystem, mixing elements of both the ‘Cambrian Explosion’ and the ‘Great Ordovician Biodiversification Event’ (GOBE). The Fezouata Lagerstätte occurs at different intervals in the Fezouata Shale, a formation ranging from the lower Tremadocian to the upper Floian (Lower Ordovician). In spite of recent major advances in the detailed biostratigraphy of the Fezouata Shale, there is currently no consensus on the precise age of the fossiliferous levels yielding exceptionally preserved assemblages. Consequently, all available biostratigraphical evidence based on several fossil groups is here critically reviewed and discussed. It can be concluded that exceptional preservation is restricted to a few thin, discontinuous, lens‐shaped horizons occurring in two distinct parts of the Fezouata Shale: a lower interval (260–330 m above the base of the formation) and an upper interval (570–620 m). Integrated biostratigraphical studies, essentially based on investigations of graptolites, acritarchs and conodonts, indicate that the lower interval can be correlated with the upper Tremadocian, whereas the upper interval corresponds to the middle Floian. [ABSTRACT FROM AUTHOR]

A Sandbian brachiopod association from the Calapuja Formation, in the Peruvian Altiplano, north-west of Lake Titicaca, has allowed a re-examination of the palaeobiogeographical relationships between Gondwana and Avalonia during the Late Ordovician, when the palaeocontinents are considered to be already very distant from one another. The brachiopod fauna includes the new species Onnizetina calapujensis sp. nov., Horderleyella chacaltanai sp. nov., Drabovinella minuscula sp. nov. and Tasmanella curtiseptata sp. nov., as well as Caeroplecia sp., Dinorthis cf. flabellulum and Tunariorthis cardocanalis. In addition, Colaptomena expansa expansa and Heterorthis retrorsistria, known from the British Burrellian Stage of the Caradoc Series (late Sandbian) in Wales and the Welsh Borderlands, have also been identified. The brachiopod collection is the most diverse known from a single locality in the whole Central Andean Basin. Within it, forms with clear Gondwanan links occur, such as the new species of Onnizetina, Drabovinella and Horderleyella, and typical representatives of the Avalonian faunas, such as the Welsh Colaptomena expansa expansa and Heterorthis retrorsistria. The brachiopod species exchange between the Proto- Andean margin of Gondwana and Avalonia, now believed to be possible during the late Sandbian, allows a reconsideration of the global taxonomic affinities of both regions. With this in mind, detrended correspondence analysis ( DCA) and cluster analysis have been applied to an updated rhynchonelliformean brachiopod matrix consisting of presence/absence data. The scatter plot resulting from the DCA allows a vivid visualization of the grouping and geographical trends of the South American localities with respect to Avalonia- Baltica and the Mediterranean margin of Gondwana during the Sandbian. Our results agree with previous palaeogeographical reconstructions, depicting Avalonia very close to Baltica and already distant from Gondwana. As a few brachiopod species, with low dispersal potential, would have been able to migrate between those distant palaeocontinents, the existence of intermediate islands in the Rheic Ocean, permitting the transit by island hopping of eurythermal species, must be considered. [ABSTRACT FROM AUTHOR]

Illaenid trilobites were relatively scarce in south-polar peri-Gondwanan areas during the Ordovician, with all their African occurrences restricted to the Middle and Upper Ordovician of Morocco. At a specific level, only the Bohemian form Ectillaenus benignensis (Novák) has been positively identified from the Middle Ordovician of that region. In the present work we add the discovery of the new form Caudillaenus nicolasi gen. et sp. nov., occurring in a single bed of late Darriwilian 2 age within the Taddrist Formation of the Rahiat region (south of Alnif), in the central Moroccan Anti-Atlas. The new genus is characterized by a large and subtriangular pygidium, a cephalon with relatively large eyes, a broad rostral plate with a short upwardly and forwardly turned posterior flange, and a globose hypostome. It shows a spheroidal enrolment type previously unknown in illaenids, with the pygidium protruding beyond the cephalon, and the cephalic margin fitting into a shallow and wide coaptative furrow on the pygidial doublure. [ABSTRACT FROM AUTHOR]

Paleovalleys and their infilling successions are described from outcrops and drill cores of the Cantabrian Range (northern Spain). A Hirnantia fauna and associated diamictites with striated lonestones indicate that the paleovalleys are related to the Hirnantian (latest Ordovician) glacial event. Based on overall geometry, depositional facies, and associated deformation structures, the paleovalleys are interpreted as subglacial tunnel valleys. They were most likely related to the North Gondwana ice sheet. The ice sheet therefore reached the Ibero-Armorican domain that was still attached to the Gondwana landmass at least until the latest Ordovician. [ABSTRACT FROM AUTHOR]

Large quarrying surfaces of roofing slate in the Arouca Geopark (northern Portugal), formed under oxygen-depleted conditions, have yielded a unique Ordovician fossil lagerstätte that reveals new information on the social behavior of trilobites. It provides several of the world's largest trilobite specimens (some reaching 70 cm), showing evidence of possible polar gigantism in six different species, as well as numerous examples of monotaxic and polytaxic size-segregated autochthonous trilobite clusters, some of which contain as many as 1000 specimens. These reveal a very diverse social behavior, which includes temporary refuge from predation and synchronous molting and reproduction, demonstrated for the first time in five contemporary families of three different trilobite orders from a single formation. [ABSTRACT FROM AUTHOR]

Trilobites were one of the most successful groups of marine arthropods during the Palaeozoic era, yet their soft-part anatomy is only known from a few exceptionally-preserved specimens found in a handful of localities from the Cambrian to the Devonian. This is because, even if the sclerotized appendages were not destroyed during early taphonomic stages, they are often overprinted by the three-dimensional, mineralised exoskeleton. Inferences about the ventral anatomy and behavioural activities of trilobites can also be derived from the ichnological record, which suggests that most Cruziana and Rusophycus trace fossils were possibly produced by the actions of trilobites. Three specimens of the asaphid trilobite Megistaspis (Ekeraspis) hammondi, have been discovered in the Lower Ordovician Fezouata Konservat-Lagerstätte of southern Morocco, preserving appendages and digestive tract. The digestive structures include a crop with digestive caeca, while the appendages display exopodal setae and slight heteropody (cephalic endopods larger and more spinose than thoracic and pygidial ones). The combination of these digestive structures and the heteropody has never been described together among trilobites, and the latter could assist in the understanding of the production of certain comb-like traces of the Cruziana rugosa group, which are extraordinarily abundant on the shallow marine shelves around Gondwana. [ABSTRACT FROM AUTHOR]