Book reviewFishes of the North-eastern Atlantic and the Mediterranean: Volume II. P.J.P. Whitehead, M.-L. Bauchot, J.-C. Hureau, J. Nielsen, E. Tortonese (Editors). UNESCO Press, Paris, 1986, pp. 510–1007, FF 250, Dfl 105.00, ISBN 92-3-002308-6

Many benthic marine invertebrates develop by means of free-living, dispersive larval stages. The presumed advantages of such larvae include the avoidance of competition for resources with adults, temporary reduction of benthic mortality while in the plankton, decreased likelihood of inbreeding in the next generation, and increased ability to withstand local extinction. However, the direction of evolutionary change appears generally biased toward the loss of larvae in many clades, implying that larvae are somehow disadvantageous. Possible disadvantages include dispersal away from favorable habitat, mismatches between larval and juvenile physiological tolerances, greater susceptibility to environmental stresses, greater susceptibility to predation, and various costs that may be associated with metamorphosing in response to specific chemical cues and postponing metamorphosis in the absence of those cues. Understanding the forces responsible for the present distribution of larval and non-larval (aplanktonic) development among benthic marine invertebrates, and the potential influence of human activities on the direction of future evolutionary change in reproductive patterns, will require a better understanding of the following issues: the role of macro-evolutionary forces in selecting for or against dispersive larvae; the relative tolerances of encapsulated embryos and free-living larvae to salinity, pollutant, and other environmental stresses; the degree to which egg masses, egg capsules, and brood chambers protect developing embryos from environmental stresses; the relative magnitude of predation by planktonic and benthic predators on both larvae and early juveniles; the way in which larval and juvenile size affect vulnerability to predators; the extent to which encapsulation and brooding protect against predators; the amount of genetic change associated with loss of larvae from invertebrate life cycles and the time required to accomplish that change; and the degree to which continued input of larvae from other populations deters selection against dispersive larvae. The prominence of larval development in modern life cycles may reflect difficulties in losing larvae from life cycles more than selection for their retention.

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On the advantages and disadvantages of larval stages in benthic marine invertebrate life cycles

Taphonomy plays diverse roles in paleobiology. These include assessing sample quality relevant to ecologic, biogeographic, and evolutionary questions, diagnosing the roles of various taphonomic agents, processes and circumstances in generating the sedimentary and fossil records, and reconstructing the dynamics of organic recycling over time as a part of Earth history. Major advances over the past 15 years have occurred in understanding (1) the controls on preservation, especially the ecology and biogeochemistry of soft-tissue preservation, and the dominance of bi- ological versus physical agents in the destruction of remains from all major taxonomic groups (plants, invertebrates, vertebrates); (2) scales of spatial and temporal resolution, particularly the relatively minor role of out-of-habitat transport contrasted with the major effects of time-averaging; (3) quantitative compositional fidelity; that is, the degree to which different types of assemblages reflect the species composition and abundance of source faunas and floras; and (4) large-scale var- iations through time in preservational regimes (megabiases), caused by the evolution of new bod- yplans and behavioral capabilities, and by broad-scale changes in climate, tectonics, and geochem- istry of Earth surface systems. Paleobiological questions regarding major trends in biodiversity, major extinctions and recoveries, timing of cladogenesis and rates of evolution, and the role of environmental forcing in evolution all entail issues appropriate for taphonomic analysis, and a wide range of strategies are being developed to minimize the impact of sample incompleteness and bias. These include taphonomically robust metrics of paleontologic patterns, gap analysis, equal- izing samples via rarefaction, inferences about preservation probability, isotaphonomic compari- sons, taphonomic control taxa, and modeling of artificial fossil assemblages based on modern an- alogues. All of this work is yielding a more quantitative assessment of both the positive and neg- ative aspects of paleobiological samples. Comparisons and syntheses of patterns across major groups and over a wider range of temporal and spatial scales present a challenging and exciting agenda for taphonomy in the coming decades.

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Taphonomy and paleobiology

Ichnology is the study of traces created in the substrate by living organisms. This is the first book to systematically cover basic concepts and applications in both paleobiology and sedimentology, bridging the gap between the two main facets of the field. It emphasizes the importance of understanding ecologic controls on benthic fauna distribution and the role of burrowing organisms in changing their environments. A detailed analysis of the ichnology of a range of depositional environments is presented using examples from the Precambrian to the recent, and the use of trace fossils in facies analysis and sequence stratigraphy is discussed. The potential for biogenic structures to provide valuable information and solve problems in a wide range of fields is also highlighted. An invaluable resource for researchers and graduate students in paleontology, sedimentology and sequence stratigraphy, this book will also be of interest to industry professionals working in petroleum geoscience.

Ichnology: Organism-Substrate Interactions in Space and Time

Palaeoecology and evolution of marine hard substrate communities

Taphonomy, the understanding of fossilization processes in paleontology and archeology

Fossil bioerosion traces at a new site of Les Bez (Jura Department) and those already known from Verrieres-de-Joux (Doubs Department) in the central French Jura record an ancient Miocene cliffed shoreline cut into Lower Cretaceous limestones. Both localities are at about 900 m above the present sea level. Caulostrepsis, Gastrochaenolites and Circolites are the ichnogenera identified at Les Bez, whereas only Gastrochaenolites is present at Verrieres-de-Joux. This ichnoassociation identifies the Entobia ichnofacies, which corresponds to the upper infralittoral marine environment, biologically associated with the biocenosis of photophilic algae. By means of digital analysis of high-resolution field images, the percentage of the surface affected by the erosive activity of polychaete worms, bivalves and echinoids has been calculated. This information permits a better evaluation of their biological activity, thus complementing the data on the number of specimens per surface area. The cliff preserved at Les Bez was more affected, showing Gastrochaenolites with diameters smaller than those at Verrieres. The Circolites–Caulostrepsis association is well developed at Les Bez, where polychaete borings are located within echinoid bowl-shaped pits with particular patterns, suggesting an ecological relationship between involved organisms. Moreover, the distribution of the borings along this outcrop is not uniform and digital analysis at three sections (A, B and C) suggests a lower and an upper zone developed on the outcrop under slightly different environmental conditions within the upper infralittoral. The exceptional preservation of the Les Bez fossil cliff-site demands protection in order to ensure its future existence and accessibility.

Early Miocene (Burdigalian) marine rocky shores in the French Jura Massif: a palaeoecological and palaeoenvironmental analysis

En la literatura paleontológica, las formas del genero Cyclope del Plioceno son consideradas, en general, como C. neritea (Linnaeus, 1758), nombre de la especie viviente en el Mediterráneo. Esto es debido a la casi total similitud entre los adultos de ambas formas. Los representantes de este género, al llegar al estado adulto, seccionan el ápice de su concha (protoconcha y primeras vueltas de la teleoconcha), por lo cual los adultos nunca presentan la protoconcha. En sedimentos del Plioceno Inferior de Monteu Roero (Piemonte, NO de Italia) se han hallado ejemplares juveniles del genero Cyclope que conservan la protoconcha. La protoconcha de los individuos fósiles es multispiral, mientras que la protoconcha de los actuates C. neritea es paucispiral. Este dato es suficiente para considerar ambas formas como especies distintas. La especie pliocénica debe designarse como C. migliorinii (Bevilacqua, 1928). Estas son especies gemelas que se diferencian básicamente por la morfología de su protoconcha, lo cual indica desarrollos embrionario-larvario distintos, sin modificaciones en la forma juvenil-adulta. Se comentan los caracteres más relevantes del género, se hace una descripción detallada de C. migliorinii fósil y se realiza la comparación con C. neritea actual. La única diferencia que parece constante entre las formas adultas de ambas especies es el mayor recubrimiento de la última vuelta sobre las anteriores en C. migliorinii. También desde el punto de vista autoecológico las dos especies coinciden ampliamente. 

Revisión del género Cyclope risso, 1826 (gastropoda: nassariidae) en el Plioceno Mediterráneo

We start by acknowledging that comments are welcome and the ensuing discussion generally contributes to a better understanding of the scientific questions at stake, in the present case a paleoichnological study of a major Neogene bioeroded surface associated with an ancient rocky shoreline, which may be followed for about 1.5 km along the Oura sea cliffs on central Algarve, in southern Portugal. The aim of Cachão et al.’s (2009) paper was to show the geological significance of major bioeroded surfaces, their identification, and interpretation, by demonstrating the importance of the Oura hardground for the understanding of the stratigraphic record of the Neogene of southern Portugal and its correlation with Iberian tectonic development. For this purpose, a detailed paleoichnological study of the Oura hardground allowed to confirm the existence of an important intra-Miocene stratigraphic gap, represented by a razor-sharp erosional contact that separates the two main Neogene units in the Algarvian region (southern Portugal). The existence of these bioerosive structures allowed the reconstruction of the sequence of events related to this episode. At the same time, it was possible to state the relationship between this stratigraphic gap and the tectonic phase that took place in the Betic Chain and Alboran Sea domain and highlight the main differences between a foreland basin of the Betic orogen (the Oura bioeroded unconformity) and the Spanish unconformities in the inner sector of the Betic orogen (Santos et al. 2008). The Cachão et al. (2009) paper is a result of a line of research started by this international team more than 10 years ago (da Silva et al. 1999) dealing with the paleoichnology and the paleoecology of Neogene rocky shores in the Iberian and Eastern Atlantic Islands Neogene and their possible extra-paleontological implications (e.g., Domènech et al. 1999; Santos et al. 2008, 2010, 2011). We will continue by stressing that none of the comments produced by Pais and Legoinha (2010) directly dispute or even remotely refer to any of the major aspects focused on in our paper and as so stated in its title; namely, the occurrence of a bioeroded megasurface in the Oura region, the paleoichnological identification of the ichnofossils involved and their paleoenvironmental interpretation, as well as the existence of an intra-Miocene stratigraphical discontinuity (as shown by the bioeroded surface), and its regional tectonic implications. Thus, Pais and Legoinha (2010) statement ‘‘(...) to support very speculative and most likely, erroneous conclusions’’ without presenting any alternative interpretation or a paleogeographic and tectonic model that might contradict our conclusions is, at least astonishing. More specifically, Pais and Legoinha (2010) failed to interpret our Fig. 2 (Cachão et al. 2009) as a synthetic stratigraphical columnar section for the Oura Neogene sequence (as mentioned in its caption), i.e., of the Neogene sequence in the Oura region, and confused it with their own M. Cachão (&) C. M. da Silva Centro de Geologia e Dept. de Geologia, Faculdade de Ciências, Universidade de Lisboa, C6, Campo Grande, 1749-016 Lisbon, Portugal e-mail: mcachao@fc.ul.pt

The bioeroded megasurface of Oura (Algarve, south Portugal): implications for Neogene stratigraphy and tectonic evolution of southwest Iberia: reply to Pais and Legoinha (DOI 10.1007/s10347-011-0268-y)

Jordi Martinell

Papers

Taphonomy, the understanding of fossilization processes in paleontology and archeology

Early Miocene (Burdigalian) marine rocky shores in the French Jura Massif: a palaeoecological and palaeoenvironmental analysis

Revisión del género Cyclope risso, 1826 (gastropoda: nassariidae) en el Plioceno Mediterráneo

The bioeroded megasurface of Oura (Algarve, south Portugal): implications for Neogene stratigraphy and tectonic evolution of southwest Iberia: reply to Pais and Legoinha (DOI 10.1007/s10347-011-0268-y)

Remembering Dr. Jordi M. de Gibert