Jordi Martinell

Bio: Jordi Martinell is an academic researcher from University of Barcelona. The author has contributed to research in topics: Bioerosion & Trace fossil. The author has an hindex of 20, co-authored 64 publications receiving 1070 citations.

Age and Date for Early Arrival of the Acheulian in Europe (Barranc de la Boella, la Canonja, Spain)

Abstract: The first arrivals of hominin populations into Eurasia during the Early Pleistocene are currently considered to have occurred as short and poorly dated biological dispersions. Questions as to the tempo and mode of these early prehistoric settlements have given rise to debates concerning the taxonomic significance of the lithic assemblages, as trace fossils, and the geographical distribution of the technological traditions found in the Lower Palaeolithic record. Here, we report on the Barranc de la Boella site which has yielded a lithic assemblage dating to ,1 million years ago that includes large cutting tools (LCT). We argue that distinct technological traditions coexisted in the Iberian archaeological repertoires of the late Early Pleistocene age in a similar way to the earliest sub-Saharan African artefact assemblages. These differences between stone tool assemblages may be attributed to the different chronologies of hominin dispersal events. The archaeological record of Barranc de la Boella completes the geographical distribution of LCT assemblages across southern Eurasia during the EMPT (Early-Middle Pleistocene Transition, circa 942 to 641 kyr). Up to now, chronology of the earliest European LCT assemblages is based on the abundant Palaeolithic record found in terrace river sequences which have been dated to the end of the EMPT and later. However, the findings at Barranc de la Boella suggest that early LCT lithic assemblages appeared in the SW of Europe during earlier hominin dispersal episodes before the definitive colonization of temperate Eurasia took place.

Insect Taphonomy Experiments. Their Application to the Cretaceous Outcrops of Lithographic Limestones from Spain

Abstract: The study of necrobiotic and biostratinomic processes affecting insects on being trapped in water are described. Specially conditioned aquariums were used for the laboratory experiments. The results obtained have been used to interpret the fossilization processes of insects found in the lithographic limestones of the Lower Cretaceous in Spain. Introduction The "post-mortem" floating of fossil remains (marine or terrestrial) has been studied by several authors (DENTON & GILPIN-BROWN 1966, CHAMBERLAIN et al. 1981, FERGUSON 1985, SAUNDERS & SHAPIRO 1986, HAMMANN et al. 1986, REYMENT 1986, etc.). The agony and death of insects is not a subject that would normally interest the biologist. The only studies that can be cited for a description of actualistic observations on the behavior of insects trapped on the water surface are those of LUTZ (1984,1990). Our biostratinomic observations help to explain the fossilization process of insects and the environmental conditions.The present experiments were initiated to determine the nature of the taphonomic processes which had caused the excellent state of preservation of the insects of the Lower Cretaceous of Spain (MARTINEZ-DELCLOS 1991). These insects are found in lithographic limestone outcrops of lacustrine origin. They are located in two distinct areas. The first being at "La Serra del Montsec, Lleida province" in the outcops of "La Pedrera de Rubies" and "La Cabrua" of Berriasian-Valanginian age (MARTINEZ-DELCLOS et al. 1991a) and the other being at "La Serrania de Cuenca, Cuenca province" in the outcrop of "Las Hoyas" of Barremian age (SANZ et al. 1988) (Fig. 1). Insect Buoyancy The present investigation has studied the behaviour of different kinds of terrestrial insects on being trapped on the water surface by the surface tension and the physical conditions that permit submersion and thus the settling on the bottom and later fossilization. Therefore, the necrobiotic and biostratinomic processes have been studied exclusively. Observations of the same characteristics have also been made on aquatic insects (principally Heteroptera) or on those which during a period of their life may live in this habitat (odonate and mayflies nymphs). For these studies a series of experiments were carried out in the laboratory with aquariums of various sizes, the largest being of 250 litres and the smallest being of 25 litres (MARTINELL & MARTINEZDELCLOS 1990). In some of these, natural conditions were simulated by the incorporation of species from rivers and lakes of different life habits (fish, amphibia, crustaceans, insect nymphs, etc.). Evidently, the fauna and flora which populated the lacustrine ecozones during the Cretaceous are not at ones disposal. Yet, the performance may be considered comparable in global terms, bearing in mind that the direct application of actualism must in some cases be done with caution. In other tanks no disturbing agent of organic nor inorganic nature was introduced, except the microorganisms that the water may have contained or which developed therein. A tank of 1500 litres was also installed (surface area of 3 m) in the open air to facilitate the study of those insects which through natural causes fell into the experimental tank. All experiments were carried out with still, oxygenated freshwater. These experiments were carried out during the spring, summer and autumn of 1990 and 1991, and 134 Xavier Martinez-Delclos & Jordi Martinell Fig. 1: Geographical location of the lithographic limestones outcrops of Spain (Lower Cretaceous) and brief description of the evolution of the different lithofacies. were suspended in winter due to the decrease in the number of insects. The effects of rain, wind and waves on the insect remains were also observed. At times these elements were created artificially. Both dead and living insects were introduced into the tanks. The necrobiotic behaviour of these and also the behaviour of the other individual inhabitants of the tanks was observed. Experimental Observations Observations were made periodically on each of the aquariums and in the large tank. With respect to the terrestrial insects, observations were made constantly from the beginning of agony until death and afterwards until the definite sinking. This method was used to study those organisms that died in the water and also those introduced into the water already dead. With respect to the aquatic species, observations were made from the time of definite death onwards. Insects of the following orders were controlled during the experiment: Blattodea, Orthoptera, Homoptera, Heteroptera, Ephemeroptera, Diptera, Hymenoptera, Coleoptera, and Neuroptera. All these fossilized in the lithographic limestones at "Las Hoyas" and / or Montsec. The behaviour of Lepidoptera and Dermaptera was also observed even though they were not present in the deposits studied. To explain the observations made on terrestrial insects three stages were differentiated with all the processes that function in each one of them: On the water surface. During the sinking process. On the tank bottom. Insect Taphonomy Experiments 135 On the water surface On falling into the water the insect is trapped by the surface tension. The struggle to reach a solid surface and thus to be able to leave the water now begins. Behaviour varies according to insect group. Two types of behaviour patterns are demonstrated by wingless insects when falling into the water: A) The first group includes those organisms with a low specific weight, inferior to that of water. The behaviour of individuals of this type has been studied solely with worker ants. On falling into the water they move around freely on the surface. As they go forward the abdomen is raised in a rythmic movement which may be interpreted as a means to achieve respiration. They arrive at the edges of the tanks without difficulty and leave without any problem. B) The second group includes those organisms with a high specific weight, greater than that of water. Tests here were carried out on earwigs (Pl.l, Fig. A) and/or cockroaches. On falling into the water they overcome the surface tension without difficulty and descend directly to the bottom still

An ethological framework for animal bioerosion trace fossils upon mineral substrates with proposal of a new class, fixichnia

Abstract: Animal bioerosion trace fossils upon mineral substrates are analyzed from the point of view of the Seilacherian ethological classification. Several of the currently accepted ethological classes: cubichnia, fugichnia, repichnia, fodinichnia, agrichnia, calichnia and aedificichnia are not represented in these substrates. This fact points out a lower behavioral diversity of hard substrate trace fossils when compared with soft sediment trace fossils. Bioerosion traces can be classified in just five classes: domichnia, pascichnia, equilibrichnia, praedichnia and fixichnia. Fixichnia is here erected to gather superficial etching scars resulting from the anchoring of fixation of sessile epiliths by means of a soft or skeletal body part. Praedichnia and fixichnia are exclusive of the bioerosion realm.

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

Abstract: 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.

Taphonomy and paleobiology

Abstract: 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.

Ichnology: Organism-Substrate Interactions in Space and Time

Abstract: 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.