Eduardo Mayoral

Trace fossil assemblages on Miocene rocky shores of southern Iberia

The use of rocky palaeoshore bioerosion analysis in the study of palaeontological and geological questions is beginning to bear fruit. Five southern Iberian Neogene rocky shores have been analysed and their bioerosion structures have been identified. The observed ichnodiversity is rather low; eleven ichnospecies were identified. These include bioerosion structures produced by polychaete annelids (Caulostrepsis, Maeandropolydora), clionaid sponges (Entobia), echinoids (Circolites), and endolithic bivalves (Gastrochaenolites). The different ichnoassemblages present in Miocene rocky shores in both Portuguese and Spanish sectors correspond to the Entobiaichnofacies. Comparison with the northeastern counterparts of these shores has also been carried out. The study of southern Iberian Miocene rocky shores made it possible to correlate them with the regional tectonic evolution and the main Neogene transgressive events affecting the region.

A new occurence of the genus Tonkinella in northern Spain and the Middle Cambrian intercontinental correlation

The genus Tonkinella is a typical polimeroid trilobite in lower Middle Cambrian rocks from Vietnam, Canada, U.S.A., India, Korea, Siberia, China and Argentina. It has recently been found in the Mediterranean region (Iberian Chain, northeastern Spain). In this paper we refer the finding of Tonkinella aff. breviceps in the Leonian (lower Middle Cambrian) of the Cantabrian Mountains (northern Spain), analysing its stratigraphical position, fossil assemblages, biochronology and utility for intercontinental correlation. The presence of this taxon allows us to make a more accurate correlation between the Middle Cambrian biochronological scales of Laurentia, the Mediterranean area and China.

Extreme habitat adaptation by boring bivalves on volcanically active paleoshores from North Atlantic Macaronesia

A bstractExtensive bivalve borings are described in detail for the first time from basalt rockgrounds in the North Atlantic volcanic islands of Macaronesia. They occur on a Middle Miocene rocky shore of a small islet of Porto Santo (Madeira Archipelago of Portugal), as well as on Plio-Pleistocene rocky shores on Santiago Island (Cape Verde). A basalt substrate is widely penetrated by clavate-shaped borings belonging to the ichnogenus Gastrochaenolites interpreted as dwelling structures of suspension-feeding bivalves. Some of these borings still retain evidence of the alleged trace-makers preserved as body fossils, while others are filled with their casts. The ichnofossil assemblage present on these bioeroded surfaces belongs to the Entobia ichnofacies. Recognition of Gastrochaenolites borings in volcanic rocks provides useful paleoenvironmental information regarding an expanded strategy for hard-substrate colonization. Preliminary results from fieldwork in the Cape Verde Archipelago indicate that such borings are more widespread through Macaronesia than previously thought.

Macanopsis plataniformis nov. ichnosp. from the Lower Cretaceous and Upper Miocene of the Iberian Peninsula

Shallow sublitoral marine facies of the Lower Cretaceous in the Iberian Range (central aera, Josa, Teruel, NE Spain) and the Upper Miocene in the SW aera of the Guadalquivir Basin (Lepe-Ayamonte area, Huelva, SW Spain) have revealed the presence of the trace fossil Macanopsis plataniformis nov. ichnosp. The most characteristic feature of this ichnospecies is the presence of a subvertical shaft at the top ending in an elongated, slightly curved chamber that is subhorizontal/horizontal to the bedding plane. The new ichnospecies is interpreted as a domichnion constructed by a decapod crustacean (probably brachyuran). Cretaceous specimens are found in carbonate facies, in a shallow marine environment, low -to-moderate in energy. In Found contrast, Miocene specimens are typically in silt facies. The marine environment is confined to semi-confined, of low energy, rich in organic matter with muddy, semi-consolidated, intersively bioturbated bottom sediment.

What Darwin did not see: Pleistocene fossil assemblages on a high-energy coast at Ponta das Bicudas, Santiago, Cape Verde Islands

Funding for fieldwork on Santiago Island in June 2011 was provided under grant CGL2010-15372-BTE from the Spanish Ministry of Science and Innovation to project leader Eduardo Mayoral (University of Huelva). Financial support to A. Santos came from the Spanish Ministry of Science and Technology (Juan de la Cierva subprogram, Ref: JCI-2008-2431). Additional support by the Junta de Andalucia (Spanish government) to the Research Group RNM276 is also acknowledged. Partial funding to J. Ledesma-Vazquez on this project came from the Programma Integral de Fortalecimiento Institucional 2010. We thank Christopher K. Pham, Department of Oceanography and Fisheries, University of the Azores, Portugal, for help with identification of the fossil barnacles and Ricardo Ramalho, Institut fur Geophysik, Westphalishe-Wilhelms Universitat, Germany, for discussions about bioerosion by sea urchins on basalt surfaces.

A History of Ideas in Ichnology

Abstract Although the concept of ichnology as a single coherent field arose in the nineteenth century, the endeavor of understanding traces is old as civilization and involved cultural areas worldwide. In fact, fossil and recent traces were recognized since prehistoric times and their study emerged from the European Renaissance. This progression, from empirical knowledge toward the modern concepts of ichnology, formed a major research field which developed on a global scale. This report outlines the history of ichnology by (1) exploring the individual cultural areas, (2) tracing a comprehensive bibliographic database, and (3) analyzing the evolution of ichnology semiquantitatively and in a graphical form (“tree of ichnology”). The results form a review and synthesis of the history of ichnology, establishing the individual and integrated importance of the different ichnological schools in the world.

BIOEROSION SCARS OF ACORN BARNACLES FROM THE SOUTHWESTERN IBERIAN PENINSULA, UPPER NEOGENE

New etching trace fossils produced by the attachment of balanid barnacles on fossil molluscs, mainly bivalves, from the Upper Miocene of Cacela (southern Portugal) and Lower Pliocene of Huelva (southwestern Spain) are described. These traces are named as Anellusichnus igen. n. due to the ring-like shape of the scars. Two ichnospecies are recognized: A. circularis n. isp., consisting in a circular scar defined by a discoloured area or by a circular to subcircular trench and A. undulatus n. isp. that has a sinuous perimeter reflecting the undulate pathway of the furrow and a flat shelf etched into the substrate. Within the outer furrow both can display a cluster of circular, oval or subpolygonal concentric lines. A. undulatus n. isp. shows several morphologies that correspond to different ontogenetic stages. SHORT NOTE

Lower Pliocene Decapod crustaceans from the Southwestern Iberian Peninsula (Guadalquivir basin, Sevilla, Spain)

Abstract A new Lower Pliocene crustacean assemblage is recorded in the southwestern region of the IberianPeninsula. This assemblage is of very low diversity, being represented almost exclusively (96%) by specimens of Goneplax gulderi Bachmayer , 1953 of the family Goneplacidae. Other families represented are Callianassidae (Callianassa sp.), Laomediidae (Jaxea cf. nocturna Nardo , 1847 ) and Calappidae (Calappa cf. saheliensis Van Straelen , 1936 ) as well as Portunidae (sp. indet.). The similarity between the decapod faunas of the Mediterranean Late Miocene suggests that some Late Miocene Mediterranean decapods were also present in nearby parts of the eastern Atlantic realm, thus surviving the Messinian crisis. Initially, this western realm comprised a sublitoral environment with relatively deep quiet waters near the shore. Subsequently, the conditions became more energetic in a very shallow sublittoral setting.

New Ichnospecies of Cardioichnus from the Miocene of the Guadalquivir Basin, Huelva, Spain

A new ichnospecies of Cardioichnus, Cardioichnus reniformis isp. nov., is documented and described from marine strata of the Late Miocene of southwestern Spain. It is a bilobate resting trace with a heart‐shaped outline and is related to the work of a wedge‐shaped irregular echinoid of the spatangoid group.

Diverse Macroids and Rhodoliths from the Upper Pleistocene of Baja California Sur, Mexico

Abstract BAARLI, B.G.; SANTOS, A.; DA SILVA, C.M.; LEDESMA-VÁZQUEZ, J.; MAYORAL, E.; CACHÃO, M., and JOHNSON, M.E., 2012. Diverse macroids and rhodoliths from the Upper Pleistocene of Baja California Sur, Mexico. Small multitaxonomical nodules, characterized as rhodoliths, balanuliths, coralliths, bryoliths, and nodules composed of vermetids “vermetuliths,” are described from one horizon in carbonate sand from the Upper Pleistocene Mulegé Formation at Playa La Palmita, Baja California Sur, Mexico. Such a diversity of fossil, free-rolling biota is seldom described in the literature. This is the first time vermetuliths are reported in the fossil record; in addition, the coral Astrangia has not been reported to constitute coralliths before. These nodules and their associated firm-ground were generated in a shallow bay near rocky shores. Break up of a firm-ground during a sedimentary hiatus provided fragments of loosely consolidated, carbonate sandstone for organic nucleation. Fast growers, like balanids, vermetids, and bryozoans, settled on these sandstone fragments or on bioclasts. Initial rapid growth of pioneer organisms was succeeded by a period of bioerosion, and finally, encrustation with a thin, crustose to lumpy cover of coralline red algae in the climax stage of succession. These were insipient rhodoliths, where the thin cover of coralline red algae reflects a short residence time. Also evident is a rich crypto- and endofauna that lived within and an epifauna that lived on the nodules.