The Early Toarcian mass extinction event represented the most important Mesozoic and Cenozoic turnover of the population of brachiopods and severely affected other benthic fauna. Two main hypotheses have been proposed to explain the synchronous and global mass extinction: an oceanic anoxic event or a warming episode. To test both hypotheses, the dynamics of the brachiopod assemblages below and above the extinction boundary are analyzed and compared with the seawater paleotemperature variations, calculated from the δ 18 O data recorded in belemnite rostra. Five sections from Northern and Central Spain, well dated with ammonites, have been selected for this study. The sections show no indication of sedimentary breaks and contain abundant brachiopods, which have been grouped into four assemblages. The changes observed in the brachiopod assemblages show a close correlation with the changes in the seawater paleotemperatures. The oldest assemblage (assemblage 1) coincides with a cooling interval recorded to have taken place in the latest Pliensbachian. Paleobiogeographical reconstruction shows that this assemblage was distributed at paleolatitudes between 30 and 45°N, with a preference for relatively cool waters. With the rise of temperatures that took place during the earliest Toarcian Tenuicostatum Zone, assemblage 1 was substituted by assemblage 2, which composed of different species of the same genera but considerably restricted to the warmer waters of lower paleolatitudes, between 28 and 35°N. Coinciding with the rapid and pronounced increase in seawater temperature, recorded at the Tenuicostatum-Serpentinum zonal boundary, all of these brachiopod species disappeared in the studied localities, marking clearly the extinction boundary. Predominant southward currents through the Laurasian Seaway precluded the possible migration of the brachiopods to cooler northern waters. The brachiopods' disappearance is independent from the oxygenation degree of the sea bottom, and therefore the rapid warming seems to be the most plausible cause of the mass extinction. After the extinction event, the recovery of the brachiopods was uneven. Subsequent to a brief pause, recovery was rapid in Central Spain and in other southern areas of Western Tethys, whereas in northern Spain and in the whole of Europe north of the French Central Massif, brachiopods did not recover until the Mid to Late Toarcian times.

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In the present paper we describe the distribution of brachiopods in the proposed Toarcian GSSP (Global Boundary Stratotype Section and Point) at Peniche. We differentiated four assemblages in the stratigraphic interval from the upper Emaciatum Zone of the Pliensbachian to the Levisoni Zone of the Toarcian. Assemblage 1 clearly presents Northwestern European affinities, with many species that are also present in Southern England. In the last levels of the Pliensbachian and in the Mirabile Subzone (the first level of the Toarcian), Assemblage 2 contains taxa that still present Northwestern European affinities, but with a more restricted, even endemic, distribution. The majority of the species in these levels are known from the Iberian Range in Spain and other neighboring basins. An important faunal change takes place in the Semicelatum Subzone, coinciding with the base of the Cabo Carvoeiro Formation, giving rise to Assemblage 3. In this assemblage we observed a clear decrease in the size of the specimens, coinciding with the establishment of the "Koninckella Fauna"; this fauna is found in several localities in both Northwestern European and Mediterranean areas where the paleoenvironment is relatively deep or poorly oxygenated. Brachiopods disappear in Peniche just above the Polymorphum-Levisoni zonal boundary, as has been observed in several other localities in Western Tethys. Their renewal is marked by the presence of Soaresirhychia bouchardi several meters above the extinction level, constituting Assemblage 4.

The assemblages of Early Jurassic brachiopods (Pliensbachian -Toarcian) from Sierra Espuña (Murcia Province, SE Spain) are described.

Changes in brachiopod body size prior to the early Toarcian (Jurassic) mass extinction. Palaeo (2018),

The Pliensbachian-Toarcian transition was a period of changes in long-term environmental conditions leading up to the Early Toarcian Mass Extinction Event (ETMEE), which resulted in a noticeable extinction and turnover in the marine biota. The westernmost Tethyan basins, especially the peri-Iberian platforms, provide an exceptional brachiopod record to better understand the adaptive strategies and the severe ecological effects of these faunas within the marine ecosystems. This event marks a critical interval in the evolutionary history of the Phylum Brachiopoda as two orders, the Athyridida and Spiriferinida, became extinct. Evolutionary patterns displayed by several taxa from these groups and some rhynchonellids typifying deep-water habitats are analyzed across this biotic crisis spanning several Mediterranean and NW-European basins. New work performed in La Cerradura section, a deep pelagic trough from the South-Iberian palaeomargin, reveals two new taxa (Koninckodonta sumuntanensis and Atychorhynchia falsiorigo) herein described. This newly documented fauna supports pre-extinction dwarfing and resilience in deep refugia linked to the ETMEE, and an episode of speciation which is interpreted in terms of a pre-extinction radiation. In the ETMEE repopulation phase an opportunistic strategy occurs typified by Soaresirhynchia bouchardi, and a case of homoplasy involving post-extinction pioneers (Elvis taxon) is detected. Similar adaptive strategies occurred associated with other mass extinctions such as the Permian/Triassic and the Cretaceous/Paleocene events, supporting a possible standard pattern in the response of the brachiopod fauna to such biotic crises and shedding light on the ecological effects of the mass extinction events. •

The order Spiriferinida represented a significant group whose extinction is linked to the early Toarcian mass extinction event. The genusCisnerospiraManceñido, 2004, conspicuous representative of this group in the Early Jurassic of the western Tethys, is analyzed from a systematic standpoint, grounded mainly on evidence from the Subbetic domain, and its initial diagnosis is revised accordingly. A definitive suprageneric position within the subfamily Paralaballinae is formally proposed in the light of new data herein provided. Both external and internal diagnostic features and the generic and intraspecific variability are described through the analysis of theCisnerospiraspecies recorded in the easternmost Subbetic area, i.e.,Cisnerospira adscendens(Deslongchamps, 1858), C. aff.adscendens, C. angulata(Oppel, 1861), andC.?sylvia(Gemmellaro,1882). In addition, their interrelation with other records from several Tethyan basins is addressed, and the generic spectrum has been extended to include several species with high morphological affinity. This characterization thus contributes to clarify certain ambiguities in the systematics of the spiriferinids, which entails a complex taxonomy mainly based on the external features, where the ribbing pattern was given foremost classificatory value due to the lack of more reliable generic diagnostic criteria. Furthemore, a morphofunctional analysis performed inCisnerospirareveals a presumable epibenthonic libero-sessile way of life, and two alternative adaptive strategies are discussed: resting on and/or sticking in substrates with different degree of consolidation, providing a significant hydrodynamic stability to the shell.

The Global Boundary Stratotype Section and Point (GSSP) for the Aalenian Stage, formally defined at the base of bed FZ107 in the Fuentelsaz section, Castilian Branch of the Iberian Range (Spain), has been ratified by the IUGS. Multidisciplinary biostratigraphical data, based on ammonites, brachiopods, ostracods, bivalves, foraminifera, calcareous nannofossils assemblages and palynomorphs, assure worldwide correlations; magnetostratigraphic data increase this correlation power. The position of the boundary coincides with the first occurrence of the ammonite assemblage characterized by Leioceras opalinum and Leioceras lineatum and corresponds with a normal polarity interval correlated with the up-to-date Jurassic magnetic polarity time scale (Gradstein and others, 1994;Ogg, 1995).