"CURRENT TOPICS ON TAPHONOMY AND FOSSILIZATION"
This book, entitled Current Topics on Taphonomy and Fossilization results from a general call for papers to be presented in the International Conference Taphos 2002. 3rd Meeting on Taphonomy and Fossilization, held in Valencia (February 14-16, 2002) and sponsored by the International University Menéndez Pelayo. Taphonomy has received progressively more attention since the 1940, when Russian palaeontologist Efremov defined its scope as the study of the processes of fossilization and how they affect the information locked in the rock record. During the last decades, taphonomy has undergone a dynamic field of research, with interest in many other scientific disciplines such as Archaeology or forensic science. In addition, interest on taphonomic approaches has increased since the seventies among the Spanish palaeontologists, as reflected in the high number of papers dealing on several taphonomic topics. This is the third of meetings held in Spain under the title Reunión de Tafonomía y Fosilización (Meeting on Taphonomy and Fossilization).
The first meeting was held in Madrid during September 1990. The second took place in Zaragoza in June 1996. Since the eighties, several Spanish palaeontologists have adhered around the theoretical work carried out under the heading evolutionary taphonomy, whose seminal paper was published in 1981 by Sixto Fernández-López, who developed this idea throughout successive papers; other Spanish palaeontologists contributed to this interesting theoretical development. Evolutionary taphonomy involves taphonomic systems, a particular kind of open systems that shares a common trait with all open systems: their information content increases throughout time. Such kind of information was called taphonomic information by Sixto Fernández-López. This issue changes the traditional concept of information losses involved in the fossilization processes (i.e., the information loss approach). In addition, Fernández-López considers three main factors ruling the fossil record: a historical factor, a production factor and an alteration factor. History sets in each moment of geological time the biotic (e.g., evolution and palaeobiogeography,...) and physical conditions (e.g., palaeogeography, sedimentary basins,...) for building new parts of the fossil record and destroying parts of it already existent. Production features set constraints to the possibilities of fossilization; thus, differential mineral stability will be the cause of different probability to be preserved of different skeletal remains. In each stage of fossilization processes, preservation can be enhanced or prevented (alterational factor). This interplay overcomes the traditional point of view of destruction associated to the processes studied in taphonomy and opens the possibility of considering an information gain approach in taphonomy.
Madrid and Zaragoza joined together not only Spanish specialists in taphonomy but also many foreign colleagues. The success of the later meetings induced us to give an international character to this third issue of the Spanish meeting on Taphonomy and Fossilization, and we encouraged foreign scientists to submit us communications. We also invited relevant foreign researchers to offer special contributions on taphonomic problems, in order to promote the international character of the meeting. Such contributions were four plenary lectures and five invited talks; this book includes extended abstracts of invited contributions by Adolph Seilacher, Anna Behrensmeyer, Susan Kidwell (with two contributions), Ronald Martin, Richard Fariña, Nicholas Butterfield and David Ferguson.
The book has nine main sections: (i) Theory of Taphonomy, (ii) Taphonomy and Palaeobiology, (iii) Taphonomy of Shell Concentrations, (iv) Special Preservation Cases, (v) Taphonomy of Vertebrates and other Chordates, (vi) Taphonomy and Palaeobotany, (vii) Taphonomy, Sedimentology and Biostratigraphy, (viii) Taphonomy and Archaeology, and (ix) Taphonomy in Didactics and Museums. The first two sections are prone to conceptual and general problems, whereas the next four sections are devoted to more specific problems. Finally, the three last sections are involved in applications of taphonomy.
Theory of Taphonomy deals with questions related with the logic structure of taphonomy; e.g., the limit between the fields of the two main classical subdivisions, biostratinomy and fossildiagenesis, involves contradictions with the definitions of such subdivisions and a non necessary sequential character of the processes studied by them (Fernández-López and Fernández-Jalvo). The term accumulation, as created by Efremov, is used in a multifarious sense and Fernández-López et al. recommend a restrictive use based on Efremovs definition, as well as the use of other alternative terms for several cases non coincident with that definition. The other three papers of this section deal with several features involving thermodynamics, information theory and self-organization in the genesis of the fossil record. Emig and Palmqvist et al. remark the influence of the biotic processes playing a taphonomic role; the former insists on the conditions and factors around the death of individuals and the latter on the information biotic vectors throughout taphonomic processes as carrying taphonomic information which may be decoded as palaeobiological information. Since the taphonomic systems are open systems, they are far from equilibrium; this is the necessary condition for taking place self-organization, something remarked by both Palmqvist et al. and Soutullo. The latter calls on the non lineal behaviour associated to systems far from equilibrium and the influence of the previous history of the preserved entities; this point of view is specific of the science of complexity and reflects the notion of hysteresis.
The second section, Taphonomy and Palaeobiology, has two main subsections: Evolutionary Palaeobiology, on the one hand, and Palaeoecology and Palaeobiogeography, on the other. The former deals with how preservation could affect observed patterns of evolution and extinction. Molina et al. discuss problems related to the analysis of extinction patterns around the Cretaceous-Tertiary boundary. They remark the important question of reelaborated fossils (i.e., reworked from older strata) of planktic forams from deep sequences, in which samples are closely spaced, as well as the possible techniques for detecting reelaborated microfossils. Recognition of reelaborated fossils could alter the perception of the catastrophic pattern of the K-T extinction. De Renzi and Ros study an old question: the rate of evolution of bivalves from the point of view of their preservational potential. Mineralogical composition or mode of life are considered as influencing preservation. Statistical analysis concludes that preservational factors might bias the estimated rate of evolution of bivalves at the family level. In addition, evolution and preservation are related, as shown in the extended abstract of Martins lecture referred to the question of how trophic resource availability increased through geologic time; this modified directionally the biosphere in several biotic ways promoting taphonomic trends, such as increased production of marine hardpart and packing in shelly assemblages. Thus, an interplay between specific evolutionary trends in plankton and taphonomic trends is suggested.
The next subsection is concerned with the need of taphonomic studies in assessing the palaebiogeographic distribution of old organisms and their palaeoecology. Ammonoids and mammals are the object of this subsection. Taphonomic analysis of assemblages of passendorferiid ammonoids are involved in testing mechanisms and processes of distribution of recorded associations (DArpa and Meléndez). Authors relate preservational features of the shells caused by taphonomic processes to sedimentary environments, specially with their degree of turbulence; regressive episodes favoured the arrival of dead animal shells in shallower distal areas. Mammals occupy the main part of the subsection. Gröcke et al. show coherence among isotopic ratios and trace-elements from collagen and bone hydroxylapatite in order to reconstruct dietary niches of extinct mammals from early Pleistocene deposits from Southern Spain. They conclude that the original composition of the studied materials was not altered during diagenesis. Marra and Bonfiglio describe a Late Pleistocene fossil cave association from Sicily. The taphonomic traits of the assemblage studied show this as the remains of a hyaena den in an insular environment. Other two papers study the important fossiliferous site of Dmanisi (Plio-Pleistocene of the Republic of Georgia) in which the presence of hominins has been evidenced. Tappen et al. remark the central role of taphonomy on questions such as the carnivory by hominins and the relationship of hominins with other predators. They pose several questions that remain unanswered; e.g., are hominins or other biotic and/physical processes the cause of the coincidence of tools and butchered animal remains? Palmqvist studies the community structure of the large mammals of Dmanisi using the model of size-abundance patterns proposed in the early eighties by Damuth. This methodology allows to infer that the main losses of palaeobiologic information took place when the bones were exposed on the surface before burial, and that information loss affected predominantly those species of small body size. Finally, the abstract of Fariñas invited talk gives a survey on palaeoecology and taphonomy of the giant mammals of South American Pleistocene, a very interesting group characterised by the unusual large size of its members, that has set important palaeobiological and evolutionary questions. Lack of original analogues obliges to use non comparative approaches, such as biomechanics, biogeochemistry and ecomorphology. However, taphonomy can supply new insights to the palaeobiological knowledge of this group and an attempt is made by the author with some case studies.
The next section, Taphonomy of Shell Concentrations, contains two invited contributions by Kidwell: one deals with the ecological fidelity of abundance data from time-averaged assemblages, in which the main problem is the reliability of data gathered from these associations. An actualistic approach in modern systems is proposed as the way to understand ancient systems. Features such as the species rank order show a significant agreement between live and dead time-averaged assemblages. The stratigraphy of fossil concentrations (vertebrate and invertebrate concentrations) and their systematic change in the stratigraphic record is the subject of her other invited contribution. She distinguishes different features in which concentrations might change throughout time: e.g., frequency and size of skeletal concentrations or style of concentration (biogenic or hydraulic). Other papers are due to Di Geronimo et al., Farinati et al., and Parras and Casadío. They work with Cenozoic benthic mollusc associations from a sedimentological and palaeoecological point of view supported by taphonomic analysis; ways of producing the concentration, bioerosion and corrosion, dissolution of hardparts or taphophacies are the aspects considered. Márquez and Ros give a survey of the Spanish record of Triassic bivalves, which is rather poor and scarce. The authors deal with the different kinds of associations and modes of preservation. Finally, shell concentrations of ammonoids are studied by Oloriz et al., and Sandoval and Checa. These Mesozoic concentrations show different taphophacies, and are associated to discontinuities.
Special Preservation Cases is open by Seilachers invited abstract. He takes the taphonomic analysis of coprolites and cololites as a pretext for talking about the main problems of taphonomy. Therefore, the question of the non linear character of fossilization processes or the taphonomic entities as systems far from equilibrium are issues that come back. Constructional morphology would be the explanatory framework of the living bodies which will become taphonomic entities by production processes (this could be envisaged as a convergent approach to the production factor considered by Fernández-López; see above). Seilacher sees recycling as a negative unifying feature for taphonomy, as well as fossilization potential taken in a relative sense (i.e., high or low as a function of the lithotopes; there may be processes that upgraded it, a new coincidence with evolutionary taphonomy) would be a fruitful concept. The other invited contribution is that of Butterfield on the two disparate modes of preservation in Burgess Shale fossils. Non mineral structures are selectively preserved, as well as there are biominerals with different stability and thus, they exhibit differential preservation in the same environment. Cuticles are mechanically and chemically resilient, and they make up the main bulk of the Burgess Shale record, but soft tissues such as epithelia are hardly preservable. Therefore, flattened structures due to fossildiagenetic compression are the most frequent in this record. However, there is also evidence of guts or organs associated in a minor frequency. They show tridimensional aspect because they have an early diagenetic phosphate filling. The strong reactivity of midgut glands is the cause of an early diagenetic mineralization that prevented flattening. In addition, external acellular cuticles have no reactivity and they underwent the usual compression taking place in very fine grained sediments. The other contributions in this section are referred to insect preservation associated to taphonomic sequences in lacustrine Paleocene materials in Argentina, with the specific problems posed by lacustrine environments (Petrulevicius) or the evidence of microbial mats inferred by the disarticulation patterns of Miocene fossil insects in Spain (Peñalver et al.). Concretions produced in early diagenetic stage are described from two disparate ages and environments: from Miocene lacustrine sediments (Barrón et al.) and Upper Devonian marine shales from Spain (Pardo and De Renzi). In both cases, there are beautiful tridimensional fossils (insects, coal fragments in the Miocene; cephalopods and/or pelagic bivalves in the Devonian). Genesis of these concretions are discussed by the authors. Finally, Gil-Cid et al. present several cases from the Spanish Lower Palaeozoic (Cambrian and Ordovician) in which are considered several animal groups (trilobites, echinoderms, molluscs,...) and different taphonomic aspects that they show.
The fifth section of this book, Taphonomy of Vertebrates and other Chordates (conodonts), is open with the Behrensmeyers abridged survey on the influence of biotic and abiotic processes associated to the genesis of the vertebrate fossil record. The fate of vertebrate remains is governed by the characteristics of these remains and the biological and physical agents interacting with them. Behrensmeyer emphasises the importance of biotic processes and reactions biologically mediated. Palmqvist et al. give an overview on the taphonomic and sedimentary contexts of vertebrate assemblages. They see the need of a quantitative approach in order to understand the large amount of data derived from actualistic studies (e.g., size, density and spatial arrangement of bone concentrations; evidence of transport, modification and chemical alteration, as well as other features discussed in the paper). The rest of the section deals with several topics of vertebrate taphonomy: a technique for the study of 3D orientations of fossil bones, with possible applications in taphonomic and sedimentologic research (Alcalá et al.); a case of special preservation of complete skeletons of whales in Neogene diatomites of Peru, with special emphasis on several pre-burial features (Esperante et al.); a study of fossil concentrations of reptiles in Quaternary volcanic caves (Canary islands), in which two sources of taphonomic processes are distinguished: pre-burial conditions on the lava surface of the caves and initial burial within the sediment deposited on floor of the caves (Castillo et al.); Bernáldez presents a research on an actualistic case: the analysis of biostratinomic factors at work on macromammal carcasses in a Spanish National Park (Doñana); she develops a method for discerning pre-depositional traits from anthropic actions. Studies on diagenetic features of phosphatic chordate remains (mammals and conodonts) have been carried out by Marín et al., with a petrographic study of fossil bones of mammals from the Spanish Miocene, and an analysis of several diagenetic features of Spanish Triassic conodonts, considering different preservation stages in recorded associations, microstructural changes and other diagenetic traits (Plasencia et al.).
Taphonomy in palaeobotanic studies is the subject of the sixth section. This section is open with the Fergusons invited paper on taphonomic processes affecting the plant fossil record. He analyses the causes by which the fossil record of plants is so poor; however, more information can be derived. Thus, catastrophic events concentrate large amounts of plant remains (see also the paper of Cladera and Cúneo; this same section, on a particular case); in normal conditions, such large concentrations of plant remains are not produced. By combining megafossils of plants and sporomorphs, new information is available. This section contains only one paper, that of Cladera and Cúneo, about fossil plants preserved in Lower Cretaceous volcanic ashes from Argentina. This seems to represent a catastrophic event produced by a sudden ash fall on the plants living on a palaeosol; the irregular orientations exhibited by the fossil plants of this site suggests this origin. Other observations support this hypothesis.
The three remaining sections are concerned with applications of taphonomy in other geological fields, such as sedimentology and biostratigraphy (seventh), archeology (eigth) and didactics and museums (ninth). The seventh section has four contributed papers. Meléndez et al. present a Callovian-Oxfordian succession of ammonoids, in which the taphonomic study of their assemblages casts light on sedimentologic (turbulence, bathymetric data) and palaeogeografic (situation of emerged lands) aspects. Yesares and Aguirre propose to take taphophacies and other taphonomic problems from a quantitative approach. They show the need of measurements and not purely qualitative observations charged of a subjective flavour. Since many variables are required, a multivariate approach is necessary. Monaco has contributed a taphonomic study of the burrow systems produced by decapods in carbonate platform parasequences from the Lower Jurassic of the Southern Alps. This has consequences for the palaeoichnology, sequence stratigraphy and palaeoenvironmental inference. Finally, Szydlo attacks from a taphonomic and palaeoecologic point of view the foraminiferal assemblages of the Tithonian in the Silesian basin; tectonic activity could be related to preservation of foraminifera in this particular case.
The eighth section is a set of papers dealing with different aspects of the role of taphonomic studies in archaeology. It ranges from taphonomic features of archaeological charcoal for characterizing the fuel used by men during hunter-gatherer occupations (Allué), or experimental approaches for comparison of breakage produced in fresh or heated bones (Cáceres et al.). Specific studies on archaeozoology are also present; therefore, the scavenger behaviour patterns of Ursus spelaeus and their taphonomic signatures (Pinto and Andrews). The use of the petrosum bone is envisaged by Bar-Oz and Dayan for discerning between taphonomic destruction and selective transport. Yravedra et al. study the pattern of anatomical representation and its implications for interpreting many archaeological sites. Neolithic bone assemblages are studied by Marciniak from a statistical and taphonomic approach; taphonomic processes influencing the archaeologic record are applied by Savanti in a regional framework: the lake Cardiel (Argentina); she considers variability in processes associated to different geomorphologic areas; Bernáldez develops a taphonomic approach to dumping sites. Lastly, taphonomic case studies on particular species are developed by Guillem Calatayud for Vulpes vulpes as a producer of bone concentrations of micromammals in karstic deposits, or for rabbit (Pérez Ripoll).
The ninth section has only one contribution by Martínez-Pérez et al., concerning with the collection of taphonomic cases of the Museu de Geologia de la Universitat de València, in Spain. They consider how to teach the different facts studied by taphonomy through the exhibited material at the museum: biostratinomic effects as illustrated by boring or epizoans, or fossildiagenetic cases (moulds or deformed fossils).
This publication has been made possible by the wholehearted support of the Town Councilor of Culture of the Valencia City Council, Ms. María José Alcón and her cultural adviser, Mr. Pedro Aracil. Likewise, we are very grateful to the invaluable help supplied by the Publishing Service of the Valencia City Council, specially to Mr. Manuel Montesinos and Ms. Rosa Albero, as well as the team of Juan and Lourdes (Gráficas Ronda). We must also thank to the management of the Universidad Internacional Menéndez Pelayo, specially Mr. Luís Moreno and Ms. Mabel López.
Lastly, we are heartily indebted to Dr. José Sanmartín, for his enthusiastic support that made possible to held this Meeting on Taphonomy and Fossilization.