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Genetic control undoubtedly plays the most decisive role in the development of characters in rhynchonellides, especially in those structural features such as shell microstructure and brachidial architecture. However, considering the relationship between shell microstructure and type of crura in post-Palaeozoic rhynchonellides supported by recent growing research, the present study links this striking matching to the distribution of rhynchonellide morphogroups around the main post-Palaeozoic mass extinction and diversification events, innovatively introducing the ribbing pattern as a feature widely argued as indicator of deeper/shallower habitats and particular ecological conditions. The analyses performed on the Western Tethys rhynchonellide database and, directly on 28 species from the peri-Iberian margins around selected post-Palaeozoic extinction/diversification episodes, reveal a recurrent distribution pattern according to the habitat considered (epicontinental vs. epioceanic). The smooth, eurinoid, septifal/arcual body plan is the distinctive inhabitant of deeper epioceanic environments, also being the last to withdraw from the epicontinental platforms when the environmental conditions were adverse, and the pioneers or opportunistic taxa conducting repopulation of these epicontinental habitats when the conditions were re-established after crises. The ribbed, eurinoid, falciform morphogroup seems to be the more resilient stock on epicontinental platforms in relation to ecological crises. Conversely, the ribbed, leptinoid, raducal group is typical inhabitant of epicontinental seas when normal conditions prevail and shows an uneven distribution unlinked to critical events, suggesting a more specialist pattern with a diversification related with a secondary differentiation. It is suggested that this distribution dynamic of morphogroups was controlled by the availability of requirements to generate each type of crura and microstructure in epicontinental/epioceanic habitats, such as metabolic or oxygen restrictions, or the filter-feeding efficiency of the lophophore. A research line starting-point is thus herein introduced which can lead to shed light into the adaptive strategies of rhynchonellides, relating particular morphotypes with potential triggering factors of mass extinction events. ; This research is a contribution to the IGCP-655 Toarcian Oceanic Anoxic Event: Impact on marine carbon cycle and ecosystems, and was supported by project CGL2015-66604-R (MINECO, Government of Spain), and the Research Group VIGROB-167 (University of Alicante).

Herein we analyze the shell length as estimation of the body size of several brachiopod assemblages recorded into the extinction interval prior to the Early Toarcian Mass Extinction. They were collected from representative localities around the Iberian Massif (Spain and Portugal) presenting different paleoenvironmental conditions. The analysis performed has revealed two different trends of spatial and temporal changes in body size. (1) Mean size decreases in the assemblages following an anticlockwise pattern from Iberian to Lusitanian basins, in relation to the progressive environmental stress caused by shifts on terrigenous input and in depth. This diminution results from changes in the relative abundance of bigger or smaller species in each area rather than from miniaturization of the taxa. (2) Some new evolved or more resilient species show increasing sizes over time along the extinction interval. This increase affects both big spiriferinides in the Iberian Basin and small rhynchonellides and koninckinides in the Lusitanian Basin, and runs in parallel to the drop in diversity and the progressive warming of the sea water in this interval in all the localities. This increase in body size has been related to the changes in diversity that could have favored the access to resources for resilient or new evolved species. The observed patterns are comparable with those detected in the end-Permian Crisis, and might indicate a generalizable response to similar biotic crises. ; This research is a contribution to the IGCP-655 Toarcian Oceanic Anoxic Event: Impact on marine carbon cycle and ecosystems, and was supported by projects CGL2015-66604-R (MINECO, Government of Spain), and to Research Groups PBM-910431 (Complutense University of Madrid) and VIGROB-167 (University of Alicante).

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. ; This research is a contribution to the IGCP-655 Toarcian Oceanic Anoxic Event: Impact on marine carbon cycle and ecosystems and was also supported by projects RYC-2009-04316 (Ramón y Cajal Program), P11-RNM-7408 (Junta de Andalucía), CGL2015-66604-R (MINECO, Government of Spain), and the Research Group VIGROB-167 (University of Alicante).

Multiple approaches, mainly focused on assessing the depositional environments, paleotemperature, chronostratigraphical and paleobiogeographical data, morphometrical analyses and the study of the internal structure of spiriferinide brachiopods assigned to the genus Calyptoria, have revealed that this brachiopod fauna migrated from their Arab-Madagascan homeland along the North-Gondwana paleomargin into the peri-Iberian epicontinental platform system, in the same well-known spreading episode suffered by the Arab-Madagascan Bouleiceras ammonite fauna over the worldwide-distributed early Toarcian platforms. This brachiopod fauna has been so far overlooked as potential Arab-Madagascan immigrant fauna, as it was integrated together with diverse assemblages well-established in the peri-Iberian basins. Dispersal of Calyptoria stock was conditioned by the interplay of several factors, such as the tectonic framework, the development of epicontinental seas on both Tethyan margins, the early Toarcian transgression, the prevailing ocean current pattern, and their limited ability for dispersal. The revised chronostratigraphical framework of this dispersal episode reveals the coincidence with the thermal maximum recorded prior to the Early Toarcian Mass Extinction Event (ETMEE) in the westernmost Tethys Ocean. The concurrence of these factors played a significant role in the Calyptoria spreading, showing an inter-tropical distribution between 0° and 30° in both hemispheres. The taxonomical updating performed in the light of the current systematic trends support this adaptive strategy carried out by Calyptoria species, consisting of a sudden and practically synchronous dispersal without outstanding morphological changes instead of the diverse evolution of different brachiopod taxa in response to the environmental changes related to the ETMEE. Updating and rearranging of the species attributed to the genus Calyptoria suggest a new systematic scheme for several former attributions, supporting that lower Toarcian occurrences of L. undulata from westernmost Tethyan areas belong to Calyptoria, thus pointing towards the dispersal from the Northern peri-Gondwana seas to the westernmost Tethyan epicontinental platforms. Similar adaptive strategies were linked to other extinction events, supporting a possible pattern in the response of certain brachiopod populations to such biotic crises. ; This research is a contribution to the IGCP-655 Toarcian Oceanic Anoxic Event: Impact on marine carbon cycle and ecosystems, and was also supported by projects CGL2015-66604-R (MINECO, Government of Spain), and the Research Group VIGROB-167 (University of Alicante).

Koninckinids are a suitable group to shed light on the biotic crisis suffered by brachiopod fauna in the Early Jurassic. Koninckinid fauna recorded in the late Pliensbachian–early Toarcian from the easternmost Subbetic basin is analyzed and identified as a precursor signal for one of the most conspicuous mass extinction events of the Phylum Brachiopoda, a multi-phased interval with episodes of changing environmental conditions, whose onset can be detected from the Elisa–Mirabile subzones up to the early Toarcian extinction boundary in the lowermost Serpentinum Zone (T-OAE). The koninckinid fauna had a previously well-established migration pattern from the intra-Tethyan to the NW-European basins but a first phase with a progressive warming episode in the Pliensbachian–Toarcian transition triggered a koninckinid fauna exodus from the eastern/central Tethys toward the westernmost Mediterranean margins. A second stage shows an adaptive response to more adverse conditions in the westernmost Tethyan margins and finally, an escape and extinction phase is detected in the Atlantic areas from the mid-Polymorphum Zone onwards up to their global extinction in the lowermost Serpentinum Zone. This migration pattern is independent of the paleogeographic bioprovinciality and is unrelated to a facies-controlled pattern. The anoxic/suboxic environmental conditions should only be considered as a minor factor of partial control since well-oxygenated habitats are noted in the intra-Tethyan basins and this factor is noticeable only in the second westward migratory stage (with dwarf taxa and oligotypical assemblages). The analysis of cold-seep proxies in the Subbetic deposits suggests a radiation that is independent of methane releases in the Subbetic basin. ; This research is a contribution to the projects CGL2011-25894 and CGL2011-23947 (Ministry of Science and Innovation, Government of Spain) and to the Research Group VIGROB-167 (University of Alicante).

Abstract. The Global Boundary Stratotype Section and Point ol the Toarcian-Aalenian Boundary (Lower-Middle Jurassic) in Fuentelsaz Section is the first GSSP defined in Spain. Among the requirements ol the ICS lor the choice of the best boundary level are accessibility to the type-section and free access for research, and guarantees Irom the respective authority concerning to the free access and the permanent protection of the site. In our point of view, the most suitable protection ligure to safeguard the fulfilment of the ICS's requirements according to the Spanish Conservation Policy and Legislation is the Nacural Monument. This paper deals with the conservation management and classification of the Fuentelsaz area as a Natural Monument, being the Comunidad de Castilla-La Mancha Authorities the ones that have to take the necessary steps to protect the site. [RIASSUNTO] La Sezione e Punto Globale di Stratotipo per II limite Toarciano-Aaleniano (Giurassico inleriore-medio) nella Sezione di Fuentelsaz e il primo GSSP definite* in Spagna. Tra i requisiti dell'ICS per la scelta del miglior livello del limite ci sono la raggiungibilita della sezionc-tipo ed il libero accesso per la ricerca, e garanzie da parte delle rispettive autorita riguardo il libero accesso e la protezione permanente del sito. Secondo il nostro punto di vista, il profilo di protezione piti appropriate* per tutelare I'adempimento delle richieste ICS, in accordo con la Politica c Lcgislazione Spagnola di Conservazione, e il Monumento Naturale. Questo lavoro t r a i n la gesiione della conservazione e la classificazione dell'area di Fuentelsaz come un Monumento Naturale, dal niomcnio chc le Autorita di Comunidad de Castilla- La Mancha sono quelle chc devono intraprendere i passi necessari alia protezione del sito.

The Global Boundary Stratotvpe Section and Point of the Toarcian-Aalenien Boundary (Lower-Middle Jurassic) in Fueuntelsaz Section is the first GSSP defined in Spain. Among the requirements of the ICS for the choice of the best boundarv level are accessibilitv to the type-section and free access for research, and guarantees from the respective authority concerning to the free access and the permanent protection of the site. In our point of view, the most suitable protection figure to safeguard the fulfilment of the ICS's requirements according to the Spanish Conservation Policy and Legislation is the Natural Monument. This paper deals with the consevation management and classification of the Fuentelsaz area as a Natural Monuntent. being the Comunidad de Castilla-La Mancha Authorities the ones that have to take the necessary steps to protect the site.