Journal of Taphonomy VOLUME 4 (ISSUE 3)

PROMETHEUS PRESS/PALAEONTOLOGICAL NETWORK FOUNDATION (TERUEL) 2006 Available online Fernández-López at www.journaltaphonomy.com Journal of Taphonomy VOLUME 4 (ISSUE 3)

Taphonomic Alteration and Evolutionary Taphonomy

Sixto R. Fernández-López* Departamento de Paleontología, Facultad de Ciencias Geológicas (UCM) and Instituto de Geología Económica (CSIC-UCM), Universidad Complutense de Madrid, E-28040 Madrid, Spain

Journal of Taphonomy 4 (3) (2006),111-142. Manuscript received 2 May 2005, revised manuscript accepted 12 March 2006. Every process of taphonomic alteration implies change and modification of the affected taphonomic elements, but it does not necessarily lead to the destruction of taphonomic elements. Taphonomic alteration can be of four types: elementary, populational, taphonic and taphocladal. In order to interpret the differential preservation of fossils and fossilization mechanisms it is necessary to take in mind not only the original architecture of taphonomic elements and the environmental changes, but also the successive changes in architecture of taphonomic elements and the activities carried out by taphonomic elements, as well as the evolutionary modifications of taphons and taphoclades. This systemic and evolutionist procedure allows to explain how the representatives of some taphons or taphoclades have been able to end up being preserved outside of the limits of tolerance of the originally produced taphonomic elements.

Keywords: PRESERVATION POTENTIAL, TAPHONOMIC DURABILITY, FOSSILIZATION POTENTIAL, FOSSILIZATION THEORY, AMMONITES

Introduction traces of lower physical resistance, chemical stability or durability. The only entities or Most of the current taphonomic units of taphonomic alteration usually investigated interpretations consider that taphonomic are biological remains and traces, as well as alteration has acted during fossilization thanatocoenosis or taphocoenosis (Efremov, processes like a filter or a sieve, eliminating 1940, 1950) and fossil assemblages. From this a large amount of the originally produced point of view, the alteration cannot produce biological remains and traces, which were new elements, which represent new taphonomic non-preservable or of smaller durability due to groups. Taphonomic alteration cannot generate their composition and structure. The destructive new taphonomic entities. It can only role of taphonomic alteration is currently deteriorate or destroy and retain deteriorated accepted in research, and it is considered parts of the initially produced biological that taphonomic alteration can deteriorate remains and traces. Taphonomic alteration is and eliminate the biological remains and a destructive or negative force, which does

Article JTa045. All rights reserved. * E-mail: [email protected]

111 Taphonomic alteration not contribute to preservation, being only taphonomic variability, and the regulation responsible for the destruction of biological of such variability by taphonomic alteration. remains and traces. The destructive action The second of these components may be of the taphonomic alteration or the relative regarded as an extrinsic principle of behaviour of the biological remains and regulation, which is able to fix the direction traces cannot serve as causal argument to of evolutionary taphonomic processes. explain the fossilization mechanisms or Representatives of new taphonomic groups processes. Taphonomic alteration can only appear during fossilization processes. eliminate the non-preservable remains and Components of these taphonomic groups traces, and some other cause should play the show different composition and structure positive role of producing or maintaining from those biogenically produced, and they the preservable remains and traces. From increase diversity of the fossil record. In this point of view, the composition and every fossilization stage, the persisting structure of original biological remains and taphonomic groups (or taphons) will be traces, not the external environment or the those whose preserved elements have been differential behaviour of taphonomic stabilized, transformed, and replicated with entities, play a causal role in the changes a higher effectiveness in the prior stages, happened during fossilization. From a but not the most resistant or those preserved different approach, however, an alternative elements less affected by environmental model to that traditionally used in factors. taphonomy can be developed: the model of Taphonomic alteration deteriorates taphonomic modification and differential and eliminates the taphonomic elements of retention vs. the model of palaeobiological smaller durability, but it is also able to modification and selective destruction. cause favourable modifications for the The purpose of the present work is to preservation and to produce new elements show that taphonomic alteration acts at that represent new taphonomic groups, and different levels of organization and, as a it can be considered as a factor responsible consequence, it is convenient to employ a for the fossilization. Some of the taphonomic systemic and evolutionary approach in alteration processes are of destructive taphonomic analyses and interpretations. effect, and some are of conservative effect Several new concepts of evolutionary (cf. Skelton, 1993: 574). Biological remains taphonomy, such as taphon and taphoclade, and traces, fossils or taphonomic elements, allow to give a non-tautological meaning to are not the only entities or units of the concept of preservability or preservation taphonomic alteration. Alteration affects potential. taphonomic entities at different level of organization, and can generate new entities, no longer limited to act as a sieve or filter Evolutionary taphonomy destroying the taphonomic elements of smaller physical resistance, chemical stability Taphonomic preservation is the result of a or durability. Taphonomic alteration causes process, fossilization, where two favourable modifications for the preservation interrelated components are involved: the and produces new taphonomic entities, biogenic and taphogenic production of besides sieving and retaining modified parts

112 Fernández-López of the initially produced taphonomic inhibit or prevent the preservation, but they elements. From this point of view, it is can also condition, channel, facilitate, considered that taphonomic alteration is a intensify, favour, enhance, activate or promote modifier force, not necessarily negative, the alteration processes and the trends or the that can become a generating force paths of fossilization processes. Taphonomic responsible for the appearance of new alteration causes the change and, as a result, taphonomic elements of different chemical taphonomic entities are preserved. composition, representing new taphonomic groups and new taphons. Taphonomic alteration can be considered as a positive Taphonomic alteration force and, therefore, as the primary cause of changes during fossilization. Functionality Differential destruction of taphonomic and evolution of taphonomic entities also entities is just a particular case of have a relative importance as causal taphonomic alteration that can be argument. From this point of view, the distinguished with the name of taphonomic modifier action of the taphonomic sieve. Other cases of taphonomic alteration alteration, the external environment and the correspond to the differential modification relative behaviour of the taphonomic of taphonomic entities, by causal interaction entities can be causal arguments to explain among the components and the external the mechanisms of fossilization. Not only environment, giving rise to the selective the original architecture (composition and preservation. Changes in differential preservation structure) of the taphonomic entities and of two or more taphonomic entities during their external environments, but also their fossilization depends on both intrinsic and modified architectures, the successive changes extrinsic taphonomic factors. Every taphonomic of the external environment and the functional entity is subjected to the action of physical, or evolutionary activities carried out, have a chemical and biological agents from the causal role in the changes happened during external environment. Any component of fossilization. the external environment able to act directly This second approach is evolutionary on taphonomic elements is an extrinsic or and systemic, allowing to develop a theory environmental taphonomic factor. However, of the fossilization denominated theory of the external environment is not the only taphonomic evolution (Fernández-López, source of taphonomic change or selection. 1982, 1984, 1988, 1989, 1991a,b, 1995, Actual properties of taphonomic entities 1999, 2000). Taphonomic changes, selective (such physical or real properties as their preservation during fossilization and the composition, structure and behaviour with resultant differential preservation occur as a respect to environmental changes) also consequence of taphonomic alteration, as intervene during taphonomic alteration. taphonomic entities are fitted to the changes of Biological remains and traces or, in their external environment. The composition general, taphonomic elements are not the only and structure of taphonomic entities, as well entities or units of alteration. Taphonomic as their functional or evolutionary activities alteration also acts at supra-elementary and the environmental changes, can limit, levels, on entities or units of different restrict, hinder, attenuate, damage, diminish, duration. From a functional point of view, it

113 Taphonomic alteration is accepted the existence of taphonomic modifications in the taphonomic entities of entities of different level of organization: different level of organization. For example, taphonomic elements, taphonic populations dispersion of taphonomic elements can and taphonic associations (also called modify their geographic location, mechanical preserved associations; Fernández-López, position, orientation and removal degree. 1982, 2000). From an evolutionary point of However, dispersion of taphonomic elements view, it is accepted the existence of taphons, can also cause changes in the density of which can constitute units of higher order taphonomic elements of each taphonic called taphoclades (groups of taphons of population or taphon, and in its geographic common taxonomic origin). Taphonomic distribution, as well as in the proportions of elements are basic entities of the representatives of each taphon, and it can taphonomic hierarchy and those of smaller modify the composition and structure of duration (Fig. 1). The concepts of taphonomic taphons and taphonic associations. During element, taphonic population, taphon, taphonic processes of taphonomic dispersion, which association and taphoclade show increasing separate and disseminate the taphonomic generality. Taphonomic alteration acts elements, representatives of some taphons simultaneously on individuals (entities or have been destroyed while others have units) at different levels of organization, and reached new areas and environments, it causes changes and different results according favouring the persistence of taphons to the levels. The same environmental constituted by allochthonous elements. factors of alteration determine different

Figure 1. Characters of taphonomic individuals at different levels of organization of the taphonomic hierarchy.

114 Fernández-López

Figure 2. The composition and structure of taphonomic elements and the external environment are constraints of elementary alteration. Nevertheless, activities or functional properties of the taphonomic elements are also constraints of elementary alteration influencing their selective preservation. Many taphonomic elements have been destroyed by elementary alteration, but this alteration has also increased the variability of other taphonomic elements and has given rise to taphonomic elements of new architecture (composition and structure).

In fossilization, as in organic evolution of two types: functional and evolutionary (Gould, 2002: 636), changes at the different modifications. levels of the taphonomic hierarchy are Actual (physical, real or non- allometric, nonfractal, and asymmetric. dispositional) properties of taphonomic Changes at a low level may or may not have entities and their interactions with the an effect at higher levels (upward external environment allow to distinguish causation), but alteration at upper levels alteration processes at different levels. must become extensive to the units included Taphonomic alteration can be of four types: in the lower levels (downward causation; cf. elementary, populational, taphonic and Campbell, 1974). Production or alteration of taphocladal. taphonomic entities can also be a consequence of modifications happened in a Elementary alteration lower level or in a higher level of complexity. Among such processes should Every taphonomic element is constituted by be differentiated those of aggregation or molecules of a certain class (organic and/or disgregation of taphonomic entities and the inorganic), and it is possible to determine its evolutionary processes. Taphonomic systems chemical, mineralogical or petrological composition, of any level of organization have been able but such constituents are not fossil if they lack to arise during fossilization by a process of (para-)taxonomic signification. Therefore, being aggregation or disintegration of pre-existent fossil or fossilized is an emergent property, not taphonomic entities, or by an evolutionary an aggregate trait, of the taphonomic process (Fernández-López, 1989). This approach elements with respect to their components. increases the possibilities of analysis and Taphonomic elements are the entities and synthesis in taphonomic research, justifying the units of smaller level of organization the distinction between taphonomic modifications constituting the fossil record. In turn, taphonomic

115 Taphonomic alteration elements are the basic components of taphonic element. During fossilization of a certain populations, taphons, taphonic associations taphon, the appearance of new taphonomic and taphoclades, which respectively possess elements can occur by simple replication, if an elementary, population or taphonic one element is generated, or by multiple composition. replication, when more than one elements Taphonomic alteration has changed are generated. The taphonomic elements that the composition and structure of have acquired a new chemical composition taphonomic elements of any taxonomic and a structure should be considered as group from its production until its current replicas, as new elements, and not as state (Fig. 2). Selective preservation of transformed elements. Concretionary internal taphonomic elements by destruction or moulds, pyritic moulds of ammonite shells, differential modification is conditioned by as well as impressions produced by some the external environment, but also by the shells in sedimentary surfaces are replicas actual characters of taphonomic elements of the original aragonitic shells. Calcitic such as the architecture (composition and aptychi, periostracal organic remains, structure) and the functional properties (i.e., phosphatic siphuncular tubes, aragonitic shells, stabilization, transformation and replication; pyritic moulds or concretionary internal Fernández-López, 1995, 2000: 87-90). moulds of the ammonite shells are taphonomic Taphonomic stabilization means elements of different chemical composition maintenance of the composition and structure and different structural characters, and they of taphonomic elements when they are represent different taphons. subjected to environmental changes, by Taphonomic analyses of the means of two strategies or mechanisms that functional properties mentioned before can be combined: (1) realization of new (stabilization, transformation and replication) functions or activities, counteracting the allow describing the activities and behaviour action of the external environment; and (2) of representatives of each taphonomic acquisition of new structural characters, group, which are characterized by some protecting the elements of the action exercised particular actual and dispositional properties. by the factors of taphonomic alteration In this kind of research, the functional (Fernández-López, 1995, 2000: 86, fig. 37). properties, the activities or the short-term Taphonomic transformation denotes any reactions of taphonomic elements should be process leading to changes in the properties distinguished from the dispositional of taphonomic elements. Taphonomic properties, such as durability and redundancy. elements undergoing transformation can Taphonomic durability means the acquire new preservation states, changing capacity or probability of any taphonomic the nature, the number or the disposition of element to persist as an element of the same their structural characters (by loss, taphonomic class, as an element of the same substitution, addition or reordering of these taphon, being subjected to environmental characters). Taphonomic replication is the changes (Fernández-López, 1982, 1991b, process by which a taphonomic element 2000). The term skeletal durability has been produces a copy of itself. It is the process by used by several authors to denote a capacity which one or more taphonomic elements are of the skeletal remains exclusively, whereas generated by a pre-existent taphonomic the concept of taphonomic durability is

116 Fernández-López applicable to any taphonomic element (cf. Although durability of taphonomic Chave, 1964; Behrensmeyer, 1978, 1984; elements is not a mensurable property, the Lawrence, 1979; Shipman, 1981, 2001; concept is useful in taphonomy because it Flessa & Brown, 1983; Brett, 1990; allows using the relative concept of degree Kowalewski, 1997; Butler & Schroeder, of durability of taphonomic elements of a 1998; Kershaw & Brunton, 1999; Best & certain class, taphon or taphoclade and Kidwell, 2000; Simões et al., 2000; Oyen & estimating its corresponding values taking Portell, 2001; Seilacher et al., 2001; in mind their actual properties. It is also Kidwell, 2002a,b; Nebelsick & Kroh, 2002; possible to predict the variation of the Pickering & Carlson, 2002; Behrensmeyer degree of durability of elements of a certain et al., 2003; Brand et al., 2003; Hoppe et taphonomic group after an environmental al., 2003; Kowalewski & Bambach, 2003; change, and it is possible to assess if the Kowalewski & Rimstidt, 2003; Robinson et degree of durability of representatives of a al., 2003; Smith, 2003; Zuschin et al., 2003; taphon is higher or lower with respect to Beavington-Penney, 2004; Hoffmeister et other, taking in account data obtained from al., 2004; Krause, 2004; Martínez-Delclòs the fossil record, as well as experimental et al., 2004; Meléndez Hevia, 2004; Palanti and natural setting observations. For et al., 2004; Rodland et al., 2004; Tomasovych, example, in the cases when destruction of 2004a,b; Harvey & Fuller, 2005; Holmes et taphonomic elements takes place by al., 2005). Durability should not be mistaken abrasion, it is possible predicting and testing with some actual properties of taphonomic that the degree of durability usually elements such as hardness, tenacity, physical diminishes with the increasing size or resistance or robustness. Possession of decreasing sorting of the abrasive particles. resistant hard parts is an obvious help for On the other hand, elements of the same preservation in some environments, although taphonomic group being more spheroidal, it is not a guarantee; and lack or loss of hard with finer and more compact microstructure, parts does not necessarily imply non- and with a smaller amount of organic matter preservation. Durability is a dispositional usually have higher degree of durability to property, showing different values under abrasion than discoidal elements, with porous different environmental conditions. microstructure. Nevertheless, other factors Durability of a taphonomic element depends such as the size of taphonomic elements, of environmental conditions, and in a their concentration, their packing pattern or particular environment can persist the the differential attack by alterative agents softest and fragile taphonomic elements, can also affect the degree of durability of whilst the elements of highest hardness and representatives of a taphonomic group. In robustness are destroyed. For example, in this sense, the concept of half-life or the euxinic and anoxic environments, mean value of the time in which taphonomic calcareous elements usually disappear elements of a certain taphonomic group before phosphatic or organic ones; on the remain as recognizable elements serves as contrary, in alkaline and oxic environments, indicator of the degree of durability of organic remains can become completely elements of such taphonomic group (cf. destroyed when inorganic (calcareous or Cummings et al., 1986; Meldahl, 1987; phosphatic) ones still persist. Davies et al., 1989; Kidwell ,1989, 2002a,b;

117 Taphonomic alteration

Fernández-López, 1991b, 2000; Petrovich, alteration, but their relative value. Elements 2001; Kowalewski & Bambach, 2003; of a particular taphonomic group will be Kowalewski & Rimstidt, 2003; favoured by alteration only if they are more Tomasovych, 2004b). durable and/or redundant than others. Biological redundancy is the Other relevant problems, different capacity of organisms to give rise to to those of analyzing the functional multiple evidence of their existence, properties of taphonomic elements, are whereas taphonomic redundancy is the those related to the use that elements have capacity of taphonomic elements to repeat made of their capacities, to the results or the same message or to give rise to multiple effects of the activities carried out by the evidence of their existence (cfr. Tasch, elements, or to the taphonomic role that has 1965, 1969, 1973; Lawrence, 1968; had a taphonomic property. The capacity Beerbower & Jordan, 1969; Holtzman, that have had the taphonomic elements to 1979; Fernández-López, 1982, 2000). perpetuate their characters, by stabilization, Taphonomic redundancy, as well as transformation and/or replication, as well as replication, does not imply that every the effects or results that the elements have resulting element is identical to the original achieved by their durability and redundancy, are element before being replicated, but only represented by their taphonomic effectiveness. that it is of the same taphonomic class and Taphonomic effectiveness is the use made by (para-)taxonomically significant. In taphonomic elements of their durability and accordance with these ideas, production of of their redundancy. Some elements have taphonomic elements can result from given rise to multiple evidence of their redundancy and replication of a pre-existent existence, whereas others have disappeared taphonomic entity. The concept of without leaving any evidence. Although it is redundancy is of taphonomic interest probable that the elements of the same because it allows estimating different taphonomic group being differentially degrees of redundancy in representatives of effective due to their structural and different taphonomic groups under behaviour differences, it is possible to particular environmental conditions, on the consider the taphonomic effectiveness of basis of their actual properties. It is also representatives of a certain taphonomic useful to predict the variations in the degree group or taphon, or the effectiveness that of redundancy of the elements of a certain they have had to be stabilized, transformed taphonomic group according to and/or replicated. Taphonomic effectiveness environmental changes, and it is possible to can be assess keeping in mind the assess if the degree of redundancy of taphonomic survival (i.e., the proportion of representatives of a taphon is higher or taphonomic elements persisting after an lower than the degree of another under environmental change). The degree of some particular environmental conditions, taphonomic effectiveness can be estimated keeping in mind data obtained from the by the proportion of elements preserved fossil record, in modern environments or by after an environmental change, with respect experimentation. It is not the absolute value to the total number of taphonomic elements of durability or redundancy of taphonomic before the change. However, it should be elements that is important in taphonomic remarked that a higher taphonomic effectiveness

118 Fernández-López of elements does not guarantee a better and in particular of replication, transformation preservation of the taphon or of the taphoclade. and stabilization, rather than of differential Taphons or taphoclades composed of destruction. The two main ways of elementary taphonomic elements that have had higher alteration observed in the fossil record result degree of durability and/or redundancy in a from differential durability and redundancy of phase of the fossilization process might not taphonomic elements. Secondary structural be the most preservable. The taphonomic characters, appeared by taphonomic alteration, effectiveness of representatives of a taphon due to processes of maximum stabilization or taphoclade in a particular environment and minimum transformation giving rise to can be expressed by their degrees of persistence of the original architecture of durability and redundancy, but taphonomic taphonomic elements represent the elementary effectiveness does not allow to interpret the changes of smallest magnitude, whereas differential preservation or the selective new architectures arisen by maximum preservation between representatives of transformation and simple replication different taphons or taphoclades. Moreover, correspond to the elementary modifications the range of tolerance and the degree of of greatest magnitude. taphonomic effectiveness of representatives of the same taphon can be different in Supra-elementary alteration different places of their area of geographic distribution. A certain taphon may be Applying principles of the theory of systems, eurytopic in their optimal environment and any taphonomic entity can be considered as stenotopic in another region where some constituted by entities pertaining to the restrictive factor plays the maximal adjacent lower organization level, but influence (Fernández-López, 1991b, 2000). anyone of these entities possesses at least an Taphonomic effectiveness can also vary emergent property (i.e., a property not within a taphon or taphoclade, when possessed by the entities of the adjacent undergoing evolutionary modifications. The lower organization level). As an example of process of taphonomic evolution allows emergent property in relation to taphonomic explaining the persistence of some elements can be mentioned the taphonomic taphonomic elements under environmental preservability or preservation potential of conditions beyond the limits of tolerance of taphonic populations, taphons and taphoclades. the biogenically produced taphonomic Each taphonic population, taphon or taphoclade elements. For example, in the Iberian Basin has a certain value of preservability or during the Middle Jurassic, some preservation potential, although the integrating reelaborated, concretionary internal moulds taphonomic elements have only durability. of ammonites persisted in supratidal Taphonomic populations, taphons and environments, beyond the limits of taphoclades have taphonomic preservability or tolerance of the aragonitic shells, and preservation potential independently of the formed local concentrations of moulds durability of their elements. Preservability or before being definitively buried. preservation potential, similarly as durability, Examples of elementary alteration is a relative and dispositional property. that can be observed in the fossil record However, preservability must be compared correspond to cases of differential modification, with respect to the successive environments

119 Taphonomic alteration that temporarily range from the production 1978, 1984; Shipman, 1981, 2001; of the supra-elementary taphonomic entity Fernández-López, 1982, 1992, 2000; Janin, until the present evidence observed in the 1983; Behrensmeyer & Kidwell, 1985; geologic record, whereas durability of a Whittington & Conway Morris, 1985; Brett taphonomic element must be compared with & Baird, 1986; Peebles & Lewis, 1988; respect to its particular external environment. Wilson, 1988; Andrews, 1990; Allison & Taphonomic elements can vary or undergo Briggs, 1991; Donovan, 1991, 2002; Kidwell transformation (by changing their structural & Bosence, 1991; Berger & Strasser, 1994; characters) whereas taphonic populations or Lymann, 1994; Butterfield, 1995, 2003, taphons can evolve (by changing the 2005; Kidwell & Flessa, 1996; Meléndez et architecture of their taphonomic elements). al., 1996; Haglund & Sorg, 1997; Meléndez, For this reason, the durability of 1997; Perry, 1998, 1999; Powell et al., taphonomic elements can be interpreted 1998; Trapani, 1998; Martin, 1999; Moffat with functional criteria, using experimental & Bottjer, 1999; Nebelsick, 1999; Benton et data and observations in modern al., 2000; Brachert & Dullo, 2000; Harding environments, whereas the preservability of & Chant, 2000; Kidwell & Holland, 2000; taphonic populations, taphons and Zuschin et al., 2000, 2003; Bell et al., 2001; taphoclades must be interpreted with Bradshaw & Scoffin, 2001; Jones et al., 2001, evolutionary criteria. It may happen that the 2004; Zuschin & Stanton, 2001; taphons or the taphoclades represented by Bandyopadhyay et al., 2002; De Renzi et al., taphonomic elements more durable and/or 2002; Holz & Simões, 2002; Kidwell, 2002a,b; redundant in a phase of the fossilization Nebelsick & Kroh, 2002; Rickards & Wright, process are not the most preservable. On the 2002; Schieber, 2002; Badgley, 2003; Curran other hand, in any taphon or taphonic & Martin, 2003; Delvene, 2003; Greenstein association there will be elements with & Pandolfi, 2003; Harper, 2003; Kroh & higher durability and/or redundancy than Nebelsick, 2003; Lockwood, 2003; Mckinney, others in the face of physical, chemical and 2003; Nielsen & Funder, 2003; Noffke et biological factors responsible for their al., 2003; Smith & Nelson, 2003; Tsujita, alteration. The intra- and intertaphonic 2003; Trueman et al., 2003; Gupta & variability and the differential preservation Pancost, 2004; Martin et al., 2004; Martínez- observable in the fossil record are properties Delclòs et al., 2004; Messina & Labarbera, determined by alterative factors (i.e., by 2004; Schweitzer, 2004; Tapanila et al., extrinsic factors of regulation), but they are 2004; Terry, 2004; Tomasovych, 2004ab; also influenced by intrinsic factors (i.e., by Waugh et al., 2004; Wings, 2004; Gaines et palaeobiological, of production and al., 2005; Jensen et al., 2005; Smith et al., taphonomic factors that have previously 2005; Weissbrod et al., 2005; Zhu et al., acted). 2005). The taphonomic preservability or In taphonomy, the terms preservation potential cannot be reduced to preservability or preservation potential a qualitative concept, as the concept of (capacity or potential to be preserved) mean durable, resistant or robust used by some the probability of a certain taphonomic authors to distinguish among species, entity to be preserved in the geological record organisms or remains preservable and non- (cf. Müller, 1951, 1979; Behrensmeyer, preservable. It is a relative and dispositional

120 Fernández-López property of each taphon that must be characters (e.g., population size, density and compared with respect to an environment or diversity, or geographic distribution of the a group of environments that temporarily considered taphon). The cause of differential ranges from the appearance of the retention should be looked for in factors or taphonomic entity until the current forces that have promoted this result either obtention of evidence in the fossil record. If directly (by the properties of taphons) or preservability is understood exclusively as a indirectly (due to the properties of relative and dispositional property of taphonomic elements and taphonic taphonic populations, taphons or populations) and have given rise to taphoclades, not of taphonomic elements, processes that can be denominated of then this concept is no longer tautologic. In stabilizing or normalizing alteration. For accordance with this meaning, both example, some taphons are not destroyed or taphonomic effectiveness and preservability changed, or they make it in minimum depend on durability and redundancy, but degree, because they may stay in more they are not linked to each other by a stable environments, because they may have relationship of causality. Every taphonomic a more stable composition and structure, by modification representing an increase in some internal or functional inability to preservability implies an increase of change, because the taphonomic elements taphonomic effectiveness, but a higher undergo processes or carry out activities effectiveness may not be associated with an that counteract the action of the external increase in preservability. environment, because the taphonomic The selective preservation of some elements have acquired new structural taphons can be interpreted on the basis of characters protecting them of the action of the processes of taphonic retention and alterative factors and/or because the taphonization. The term taphonic retention elements have acquired new preservation denotes the processes by which the states by changing the nature, the number or composition and structure of taphons are the disposition of their structural characters. maintained unchanged, preventing their Environmental tracking, for example, is a destruction by environmental changes, as a strategy of taphons allowing them to consequence of the stabilization and counteract the destructive action of the transformation of its taphonomic elements. external environment and to achieve Taphonic retention should be understood as taphonic retention. It basically consists in a process, not as a mere persistence of reacting to adverse environmental conditions taphons. Maintenance of taphons during arisen in their area of geographic distribution taphonomic alteration (i.e., the taphonic going until more favourable environments, retention) take place by modification instead of being modified or destroyed in processes, such as the stabilization and the consonance with the environmental change. transformation of taphonomic elements. Dispersion of taphonomic elements or However, the degree or the rate of retention necrokinesis processes are not necessarily of a taphon and the differential retention destructive, and they can increase the among taphons cannot usually be reduced to degree of taphonic retention and the elementary properties or characters because preservability of taphons. they depend on supra-elementary structural

121 Taphonomic alteration

The formation of new taphonomic appearance and destruction of taphonomic groups is denominated taphonization, and it elements are the appearance and destruction is what allows the demarcation of taphons of taphons, that can be denominated taphonization (Fernández-López, 1989, 1991b, 2000). and taphonic destruction, respectively. Taphonic Taphonization is the production of one or destruction is the disappearance of a taphon more taphonic populations of a new taphon. without producing any new taphon. Taphons can be produced by Taphonization can be considered palaeobiological entities or by taphonomic as the analogous process, at the taphon entities. The origin of taphons by level, of the appearance of a new taphonomic alteration, the taphogenic taphonomic element. However, these taphonization, take place by processes of concepts present structural differences. The modification of taphonomic elements, such appearance of new taphonomic elements as the transformation and the replication. will be required in each case of taphogenic Taphons can be stable during long intervals production or replication, but such new of geologic time or undergo structural elements may have or not different modifications and even give rise to new architecture (composition and structure) and taphons constituted by taphonomic elements of may represent or not new mechanisms of different composition and structure. New taphons elementary behaviour. On the contrary, the arise during fossilization by transformation appearance of a new taphon by taphonomic and/or replication of taphonomic elements alteration, or every event of taphogenic belonging to previous population (sub)groups taphonization, implies some kind of (Fig. 3). It is possible to distinguish between differentiation in the composition and the taphonization due to accumulation of structure of the new generated, descendant changes or continuous modification of a taphon, with respect to the producer, taphon by transformation of their original taphon. On the other hand, the taphonomic elements (simple taphonization) appearance of new taphons may take place and the taphonization due to a process of either by a gradual change, or else by a division and appearance of one or more new punctuated, in frequencies and types of taphons by replication of their taphonomic characters of a taphonic population. Two elements (multiple taphonization) that have taphonic populations do correspond to taken place by directional alteration or by different taphons when they display some disruptive alteration, respectively. Nevertheless, properties promoting or involving different some taphons do not change or make it in behaviour with respect to the durability and/ minimum degree, and they are not destroyed, or redundancy of their constituent elements. as a result of processes of taphonic retention Consequently, taphons are spatio-temporally and stabilizing or normalizing alteration. limited (they have appeared and may be According to the ideas above, destroyed) being the taphonization what morphological characters of taphonomic allows to demarcate them. Each taphonomic elements are insufficient to explicit the element is unique, and each taphon is meaning of the term taphon; besides the unique too. Taphons or taphoclades could morphological criteria, other structural and be considered as abstractions but, as they genetic criteria are required. Analogous represent the natural order resultant of concepts at the level of taphon of the functional or evolutionary taphonomic

122 Fernández-López

Figure 3. Patterns of taphonization during fossilization. The formation of a new taphon from a previous one, or taphogenic taphonization, can be by continuous modification of a taphon in other (simple taphonization) or by multiplication of a taphon, appearing one or more new taphons (multiple taphonization). For example, in the case of ammonites, some periostraca were progressively carbonized or mineralized during fossildiagenesis, forming pseudomorphs of different composition, structure and durability, with respect to the original organic periostraca. These carbonized or mineralized periostraca represent new taphons, arose by simple taphonization. On the other hand, sedimentary internal moulds of ammonite shells formed at the beginning of the fossildiagenesis show different composition, structure and durability that aragonitic shells from which they have been formed by multiple taphonization. processes, they are not conventional or taphonic populations and the external arbitrary classes of similar elements. environment showing a constant change in No taphonomic element can be the same sense, will lead to directional preserved everywhere, but all taphons can alteration and, as concomitant process, to become preserved somewhere even beyond directional fossilization. This continuous the limiting constraints of the taphonomic evolutionary trend can result from repeated elements originally produced. The diversity retroactive interactions between preserved of interactions between taphonomic entities and altered taphonomic elements. and their external environment results in Diversification of an initially homogeneous taphonic alteration leading to change or to environment in turn, will lead to a constancy, depending on whether the subsequent diversification of interactions environment undergoes any change or not, between taphonic populations and their and depending on the nature of that change. respective environments. This will result in When relationships between taphonic a process of disruptive alteration and their populations of a certain taphon and their concomitant disruptive fossilization. When external environment remain stable, the the origin of the taphons take place by alteration is stabilizing or normalizing and, multiple taphonization and disruptive as concomitant process, the fossilization is alteration, it is possible to consider the new stabilizing or normalizing. A certain produced, descendant taphons as sequence of interactions between the evolutionary entities with real, non-

123 Taphonomic alteration conventional limits. In contrast, if the new preserved in a particular environment. taphons arise by simple taphonization Taphonic populations can be analyzed on (gradual modification by transformation) the basis of their elementary composition and directional alteration then the direction (i.e., of their integrating taphonomic of alteration in the taphonic populations and elements) and their structural properties: the pattern of temporal variation during the size, density, diversity, geographic period of existence of the taphon will reflect distribution and temporal structure of the the intrataphonic morphological changes in taphonic population (Fig. 1). Population the course of a genealogical trend, allowing size is the total number of taphonomic only a conventional delimitation, but not elements composing a taphonic population. necessarily arbitrary, of successive Population density is the average number of segments. taphonomic elements of a particular taphon per surface or volume unit in the area Populational alteration occupied by the taphonic population. Population diversity is the variety or Taphons are integrated by local taphonic dissimilarity of types of preservation state or populations, which can be preserved in taphomorphotypes (including taphomorphs particular environments. Specific taphons sensu Crampton, 2004) composing a are a particular class of taphons, in which taphonic population. It can be estimated by all constituent taphonic populations the values of the population richness (i.e., correspond to elements representing the the number of types of preservation state or same biological species and being able to be taphomorphotypes) and/or the population

Figure 4. Populational alteration represents the group effect on durability and redundancy of taphonomic elements of a same taphon. Populational alteration can cause destruction or local modification of taphonomic elements of the same taphon. Selective preservation by populational alteration has influenced in the formation of a great variety of taphonic associations that can be grouped in two categories, as effects of stabilization processes prevail on those of replication. These two categories of taphonic associations correspond respectively to the so-called conservation fossil-lagerstaetten and concentration fossil-lagerstaetten.

124 Fernández-López evenness (i.e., the similarity of types of higher concentration of skeletal remains preservation state or taphomorphotypes in increases the degree of cohesion and relative abundance). permeability of the sediment, hinders the Alteration of taphonic populations activity of the burrowing macroorganisms, can be due to destruction or modification of and can favour the differential taphonomic elements (by upward causation) mineralization of the remains constituting as well as to destruction or modification at an association (Kidwell & Jablonski, 1983). the population level (populational alteration). Consequently, some fossiliferous concretions Populational alteration represents the group can result from processes of populational effect on the capacity or aptitude to be alteration, by differential mineralization of preserved (durability and redundancy) of taphonic populations of higher size and taphonomic elements of the same taphon density. However, regroupment processes (Fig. 4). The degree of durability and the increasing the concentration of taphonomic degree of redundancy of the representatives elements conditioned by their own of a taphon can be conditioned by intrinsic structural properties (for example, the populational factors such as size, density, discoid form) can also promote the diversity and populational geographic differential destruction of elements of the distribution. For example, interactions same taphon, when they hinder or prevent among taphonomic elements have the sedimentary filling of internal cavities or influenced in the taphonic populations, as the sedimentary replication by means of well as in the composition and structure of external moulds of the taphonomic taphonic associations. During taphonomic elements. alteration, the density of a taphonic population Taphonomic alteration by differential or the regional density of a taphonic durability, differential redundancy or selective association (average of taphonomic elements destruction of taphonomic elements in relation per surface or volume unit in the area with some structural character of the occupied by the taphonic association) can taphonomic population represents a genuine be a limiting constraint of its geographic populational alteration. Modification or distribution, if it reaches very high or very destruction of taphonic populations low values. An increase in the concentration conditioned by such characters as population of organic remains can locally reduce the density or geographical distribution, cannot concentration of available oxygen and be attributed to elementary alteration, inhibit the processes of aerobic because taphonomic elements do not have biodegradation (Allison & Briggs, 1991). population density. Neither can the geographic Some cases of differential preservation distribution of a taphonic population be observed in common graves among the correlated with the size of the component elements being located in a more internal elements. Nevertheless, destruction of taphonic position in the group are due to the greater populations can be explained in many cases as concentration of taphonomic elements, and consequence of a mere destruction of some cases of differential preservation taphonomic elements, and can be causally among the common graves of greater reduced to the elementary level. In general, any population size and density result from taphonomic character of a taphonic population populational alteration. On the other hand, a conferring it a capacity or aptitude irreducible

125 Taphonomic alteration

Figure 5. Taphonic alteration acts on taphons and can cause their destruction or their microevolutionary modification. Actual properties of taphons (composition, structure, function and evolution) and successive external environments determine their preservation potential. Taphonic alteration can destroy some anatomical elements of a certain taxonomic group (species or genre, for example), at the same time that retains or replicates other anatomical elements of the same taxonomic group. Taphonic alteration can stabilize and transform elements of some taphons, as well as it can generate new taphons, of different composition and structure, and of higher preservation potential.

to elementary properties by interaction with population can be preserved. Populational the external environment allows a process alteration is important because it can of populational alteration, being or not promote intrataphonic trends, as well as emergent the character in question. channel the diversity and the differential The two main ways of populational preservation of populations of the same or of alteration observable in the fossil record are different taphon. The selective preservation due to differences in durability and by populational alteration has influenced in redundancy. Populational alteration will the formation of a great variety of taphonic favour the taphonic populations and the associations, that can be included in two taphons that (a) generate stabilized or categories, in accordance with the transformed taphonomic elements in prevailing effects of stabilization or changing local conditions, that maintain replication processes. These two categories their composition and structure (bias of of taphonic associations correspond persistence by differential durability) and/or respectively to the so-called conservation (b) produce more replicated taphonomic and concentration fossil-lagerstätten (cf. elements, of the same or of different Seilacher et al., 1985; Seilacher, 1992). composition and structure (bias of multiplication by differential redundancy). In Taphonic alteration general, the more different the architecture of stabilized, transformed or replicated elements Taphons can be analyzed on the basis of of a taphonic population, the greater their their population composition (the variability, and the higher will be the number composition of taphonic populations of environments in which the taphonic composing the taphon) or their elementary

126 Fernández-López composition (the composition of destruction of taphonomic elements. taphonomic elements composing the However, the selective destruction of taphon) and their structural properties: size, taphons or the rate and degree of destruction density, diversity, geographic distribution of a taphon are not reducible to elementary and temporal structure of the taphon. characters if they depend on supra- Taphonic size is the total number of elementary characters (e.g., population or taphonomic elements composing a taphon. taphonic size, density, diversity and Taphonic density is the average of geographic distribution). taphonomic elements of a particular taphon Taphogenic taphonization and per unit of surface or volume in the area taphonic retention require the modification occupied by them. Taphonic diversity is the of taphonomic elements. However, relative variety or dissimilarity of types of values of these properties (differential preservation state, taphomorphotypes or taphogenic taphonization among taphons or subtaphons of a taphon. It can be estimated selective taphonization, rate of taphonization by means of the taphonic richness and/or or degree of taphonization of a taphon, as the taphonic evenness. Taphonic richness is well as differential taphonic retention, rate of the number of types of preservation state, taphonic retention or degree of taphonic taphomorphotypes or subtaphons of a retention) usually are not reducible to taphon. Taphonic evenness is the similarity elementary characters because they depend of types of preservation state, on supra-elementary structural characters taphomorphotypes or subtaphons of a such as population or taphonic size, density, taphon in relative abundance. diversity and geographic distribution. Alteration of taphons can be due to In consequence, taphonic destruction destruction or modification of taphonomic and selective modification at the taphon elements (by upward causation), as well as level, as well as preservability, should be analyzed by destruction or modification processes at as properties dependent on supra-elementary taphonic level (taphonic alteration). Taphonic characters, not reducible to elementary characters. alteration means selective preservation of Changes during fossilization by taphonic entities or evolutionary units (taphonic retention, taphonization or taphonic destruction populations, taphons and taphoclades) due to related with some supra-elementary structural supra-elementary actual properties conferring property represent a genuine taphonic alteration. them different capacity (differential taphonic Alteration of taphons due to supra- retention, differential taphonization and elementary properties, such as the geographic preservability) to interact with the respective distribution of a taphon or the population external environments (Fig. 5). density, should be distinguished from, and Taphonic destruction, the cannot be attributed to, elementary alteration. disappearance of a taphon without producing In the case of ammonites, selective new taphons, implies the disappearance of all preservation of ammonite shells of a certain the taphonomic elements, anatomical species or genus correlated with structural components or parts with a certain architecture differences at the taphon level, such as the representing one or more species and, different geographic distribution of each accordingly, the corresponding supraspecific taphon, implies processes of taphonic taxa. Destruction of taphons can result from alteration. Taphonic alteration implies

127 Taphonomic alteration correlation between a supra-elementary does not guarantee their preservation in any character, being or not emergent, and the circumstance, and if the external environment capacity to be preserved or the aptitude at undergoes rapid and deep changes, these the taphon level. alterations can exceed the preservation Taphonomic alteration also acts on potential and result in the destruction of taphons and, in such cases, tends to taphons. If the taphonic valence is defined as eliminate those of smaller preservability. the result of the capacity of any taphon to be Constraints due to the architecture preserved in different environments, or the (composition and structure) of taphonomic result of the activities developed by elements influence on the alteration of taphons, then the taphonic valence is the taphons and in the fossilization processes. expression of the preservability that have However, characters increasing the durability had the different taphonic populations of and/or the redundancy of taphonomic one taphon when they have been in different elements do not necessarily increase the environmental conditions. A taphon of weak preservability, cause the taphonic retention taphonic valence has been able to resist only and/or taphonization or prevent the small variations of limiting environmental destruction of taphons and taphoclades. To factors, and will be called stenoic. For the explain the fossilization processes and same reasons, those taphons that have been taphonomic trends it is necessary to keep in able to be preserved in very variable or mind the different capacities of taphonomic different environments will called euryoic. elements (durability and redundancy), but Taphons of high taphonic valence, euryoic also the different capacities of taphons taphons, will be able to present a wide (preservability, differential retention and geographic distribution and they will be differential taphonization). Elementary eurycore, whereas the stenoic ones will alteration and taphonic alteration should be probably occupy restricted geographical treated as different processes that can act in areas and will be stenocore. Taphonic opposite directions. Elementary alteration valence allows characterizing taphons, but can act against taphons, worsening the the concept of taphonic valence cannot architecture of taphonomic elements and explain the geographical distribution of reducing the longevity of taphons. In other taphonomic elements or taphons (Fernández- cases, however, elementary alteration may López, 1991b, 2000; De Renzi, 1995). contribute to increase the longevity of Concepts of taphonomic effectiveness and of taphons (improving the architecture of taphonic valence allow setting out problems taphonomic elements, for example) or it referring to the factors of preservation of a may not affect them. In consequence, taphon in an area or region. They are useful elementary alteration can affect or not the concepts to describe and treat problems taphons. related to preservability. The present concept of taphonomic Main ways of taphonic alteration alteration assumes that every new specific observable in the fossil record result from taphon is produced and maintained due to differential preservation by taphonic retention and some advantage on the remaining ones, taphonization. Secondary characters appeared by whilst the less favoured forms are taphonic alteration and taphonic retention resulting destroyed. However, taphonomic alteration from maximum stabilization or minimum

128 Fernández-López transformation represent supra-elementary reaction to environmental changes. The changes of smaller magnitude, whereas variability of taphonomic entities changes characters resulting from taphonization by due to the introduction of novelties and/or maximum transformation or by simple by taphonomic alteration of the existent replication correspond to the taphonic variants. Alterative or functional taphonomic modifications of highest magnitude. The modifications take place by stabilization, magnitude of changes in the architecture transformation and/or replication of (composition and structure) of taphonomic taphonomic elements, as well as by elements during fossilization is correlated development, aggregation or disgregation of with the magnitude of taphonization taphonomic entities. Evolutionary taphonomic processes. Taphonic alteration will favour modifications take place by taphonic retention taphonic populations, taphons or and/or taphogenic taphonization of taphoclades producing more novel taphons taphonomic groups. Novelties arisen in the (bias of multiplication by differential organic evolution correspond to mutations and taphonization) and/or generating preservable adaptations, whereas novelties appeared during types under changing local conditions (bias fossilization originate from taphogenic production of persistence by differential retention of and taphonomic alteration. Functional properties taphons and subtaphons). As a general rule, of taphonomic entities depend on, or result from, the more different the variability of taphonic structural properties. And the taphonomic role populations of a taphon or the variability of played by every taphonomic entity is the result of taphons of a taphoclade, the greater the the interactions maintained with the external number of environments in which the environment. But what determines the taphonomic group will be able to be behaviour of each taphonomic entity is a preserved. The importance of taphonic complex of actual conditions resulting from alteration lies in its power to promote the previously happened taphonomic modifications. intertaphonic trends and to channel the Therefore, within taphonomic analyses and diversity and the differential preservation interpretations a distinction should be made between taphons of the same or of different between changes in composition and structure, taphoclade. changes in behaviour or function, and From the systemic and evolutionist evolutionary modifications. Among evolutionary point of view, presented and defended here, taphonomic modification, in turn, it is it is also possible to distinguish functional possible to discern between micro- and or alterative taphonomic factors from macroevolutionary taphonomic processes. evolutionary taphonomic factors, taking into account their effects on taphonomic entities. Alterative or functional factors influence on Taphocladal alteration functional properties of taphonomic elements and the geographical distribution A taphoclade is a group of taphons of of taphons, leading even to their common (para)taxonomic origin (Fig. 6). disappearance, whereas evolutionary factors Taphoclades can present genetically promote the appearance of evolutionary differentiated parts, called subtaphoclades, and modifications, favouring the durability and/ constitute taphocladal groups. A subtaphoclade or redundancy of taphonomic elements as a is a biogenically produced taphon and, as

129 Taphonomic alteration appropriate, the ulterior phyletically derived taphons. Subtaphoclades can represent types of anatomical components or parts of past organisms. In turn, a taphocladal group is a group of taphoclades of common (para) taxonomic origin. Taphoclades and taphocladal groups can be of specific or supraspecific category, according to the (para)taxonomic level of reference. Every unit of these types, with the sole exception of the smallest one, includes subordinate units and (except for the largest) is in turn included in a higher order unit. A specific taphoclade includes a group of taphons representing the same species, whereas a specific taphocladal group includes a group of specific taphoclades of the same genus. For example, the different taphons of the ammonite species Trimarginia iberica constitute a specific taphoclade, whereas the different taphoclades of the species of the genus Trimarginia constitute a specific taphocladal group. Taphoclades can be analysed on the basis of their taphonic composition and structural properties: size, density, diversity, geographical distribution and temporal structure. Taphocladal size is the number of taphonomic elements composing a taphoclade. Taphocladal density is the average number of taphonomic Figure 6. Schema of the taphoclade of the order elements of a taphoclade per unit of surface Ammonitida (Triassic-Cretaceous). At the present time, or volume in the area occupied by them. more than 30 ammonite taphons are known, from Taphocladal diversity is the variety or pseudomorphs of soft parts or organic periostraca more dissimilarity of taphons composing a or less carbonized until external moulds of aptychi. Taphons represented in this figure correspond to 5 taphoclade. Taphocladal diversity can be subtaphoclades (i.e., soft-parts, periostraca, siphuncular estimated according to the taphocladal tubes, shells and aptychi). These subtaphoclades and richness (i.e., the number of taphons) and/or taphons represented in the figure constitute a the taphocladal evenness (i.e., the similarity paraphyletic group, because some subtaphoclades and taphons that correspond for example to anaptychi, of taphons in relative abundance). In describing stomach contents or ammonite coprolites observed in and interpreting some taphoclades it can be also the fossil record are not included. useful the concept of subtaphocladal diversity, understood as the variety or dissimilarity of Every taphoclade has a taphonic subtaphoclades composing a taphoclade. composition, being constituted by taphons,

130 Fernández-López and some structural characters, which can taphoclades generated by each ammonite influence on the capacity of preservation of species or genus is conditioned by the area the taphons that compose it or in the of distribution of the corresponding aptitude at the taphon level (differential taphoclade, not by the particular geographic taphonic retention and/or differential distribution of some of the integrating taphonization). Taphocladal alteration implies taphons. Taphocladal alteration will favour destruction or modification of taphoclades those taphons and taphoclades producing (Fig. 7). Taphocladal destruction means the more elementary taphons (bias of disappearance of one or more taphoclades multiplication by differential taphonization) without producing new taphons. The and/or generating preservable types under taphocladal destruction implies the changing local conditions (bias of disappearance of all the taphonomic elements persistence by differential retention of representing one or more species and, in such taphons and subtaphoclades). Taphocladal case, the corresponding supraspecific taxa. The alteration can promote intrataphocladal taphonomic alteration by taphonic retention, trends, or else channel the diversity and the taphonization or taphonic destruction related differential preservation among taphoclades with some structural character of a taphoclade of the same or a different taphocladal group. represents a process of taphocladal alteration. From the theoretic and Examples of taphocladal alteration are those methodological point of view, it is useful to cases of selective preservation correlated distinguish between alteration of with the area of distribution of the taphonomic elements of the same or taphoclade or of the taphocladal group, and different taphon, and alteration of taphons not with the particular distributions of the of the same or different taphoclade. integrating elementary taphons. For Alteration of taphonomic elements of the example, the selective preservation of same or of different taphon is conditioned

Figure 7. Taphocladal alteration directly affects to taphoclades, causes macroevolutionary taphonomic modifications, and can modify or destroy all the taphonomic elements of a species or of a supraspecific taxon. The composition and structure of taphoclades impose conditions on the preservation potential of taphons and can channel stabilizing, di- rectional or disruptive taphonomic trends, giving rise to “unaltered fossils” and “altered or varied fossils”.

131 Taphonomic alteration by the respective values of elementary dissolution of aragonitic shells, decreased destruction, durability and redundancy. the geological longevity and preservability Alteration of taphons of the same or of of the corresponding taphoclades during the different taphoclade is conditioned by the early fossildiagenesis. Consequently, respective values of taphonic destruction, marine environments of high sedimentary taphonic retention and taphonization. rate were unfavourable for the preservation Taphonic alteration and microevolutionary of ammonite taphoclades. taphonomic changes are impelled by The concept of evolutionary differential durability and redundancy (the taphonomic trend can be used in a wide sense differential success) of taphonomic elements. to denote any supra-elementary change in a On the other hand, taphocladal alteration and particular direction during fossilization. It is macroevolutionary taphonomic changes are important to distinguish between (intra- or impelled by differential taphonic retention inter-)taphonic trends and (intra- or inter-) and taphonization (the differential success) of taphocladal trends. Intrataphonic trends taphons. Taphocladal, macroevolutionary result from changes in taphonic populations processes can be a result of differential rates of the same taphon or taphonomic lineage. of taphonic retention, taphonization and Intertaphonic trends are produced by taphonic destruction, but not of intrataphonic changes in taphons of the same changes (such as stabilization, transformation, subtaphoclade or taphonomic phyletic replication or destruction of elements). group. Intra- and intertaphonic trends can be Consequently, macroevolutionary (or taphocladal) the result of processes of elementary and microevolutionary (or taphonic) taphonomic destruction and/or differential replication, changes and processes can work in opposite and they represent microevolutionary directions. During taphonomic alteration, some taphonomic processes. Taphocladal trends trends can harm to taphoclades although they in turn are due to changes in subtaphoclades favour the preservation of integrating of the same taphoclade (intrataphocladal taphons. For example, marine environments trends) or in taphoclades of the same of high sedimentation rate favoured the taphocladal group (intertaphocladal trends). rapid burial of ammonite remains, Taphocladal trends can be the result of biases diminished the effects of the biostratinomic of taphonization and/or taphonic destruction, alteration, and promoted the preservation of and they represent macroevolutionary soft parts, periostraca and organic taphonomic processes. Taphonization biases siphuncular tubes, as well as the or directional taphonization can generate maintenance of jaw-elements in their trends in two different ways, depending on original position and the integrity of the whether taphons with a certain architecture aragonitic shells during the biostratinomic (i.e., subtaphoclades or taphoclades) either phase and at the beginning of the multiply more frequently to become more fossildiagenesis; therefore, they were common or multiply in a preferent favourable environments for the direction. Taphocladal trends due to biases preservation of some ammonite taphons. of taphonic destruction occur when taphons However, these sedimentary environments or lineages of a particular architecture (i.e., hindered the formation of sedimentary subtaphoclades or taphoclades) disappear internal moulds of shells and, after the more rapidly and become scarcer.

132 Fernández-López

From the evolutionary point of view, The capacity that have had the taphoclades trends developed by taphocladal alteration to perpetuate their characters, by taphonic can be due to the production and differential retention and/or taphonization, as well as destruction of taphons, being caused by the effects or the results achieved by the taphonization processes and taphonic preservability of their integrating taphons destruction, not by transformation of are represented by their effectiveness. taphonomic elements. Taphonomic trends at Taphocladal effectiveness is the use carried the taphocladal level can result from out by the taphoclades, the use that they processes of taphonization and/or have made, of their taphonic retention and/ differential taphonic destruction, not from or taphonization. The taphocladal mere transformation of taphonomic effectiveness can be assessed keeping in elements. As components of taphocladal mind the taphonic survival (that is to say, evolutionary trends, the role of taphons in the proportion of taphons of a taphoclade such trends will be comparable to that of the persisting after an environmental change taphonomic elements as units of change with respect to the number of taphons within a taphonic population or a taphon before the change) and the subtaphocladal subjected to alteration. If taphons act as survival (i.e., the proportion of entities or units, then taphocladal subtaphoclades of a taphoclade persisting evolutionary trends and general paths of after an environmental change in relation to fossilization processes can be due to the number of subtaphoclades before the processes of alteration of superior order change). The concepts of taphocladal (i.e., macroevolutionary processes) by effectiveness, taphonic survival and differential taphonization and/or taphonic subtaphocladal survival can be useful to destruction, and they are not a consequence describe and interpret the preservability of of intrataphonic modifications or of taphoclades. elementary alteration (stabilization, Differential durability of taphonomic transformation, replication or destruction of elements can be estimated by experimental elements). For example, the reelaborated, methods and by observation in natural concretionary, internal moulds of environments. However, preservability of ammonites of some stratigraphical intervals taphons or taphoclades, similarly as in the Jurassic of the Iberian Range adaptability of biological species, cannot be represent the only persisting taphon among estimated by experimental methods or by a varied group of taphons, and it is not the observation in natural environments. result of a progressive transformation of the Preservability of taphons and taphoclades originally produced ammonite remains. neither can be tautologically estimated by The different values of taphocladal the differential preservation observed or diversity can serve as a relative indicator of achieved in the fossil record. Taphonomic macroevolutionary success of each evolution means cumulative change in the taphoclade of the same taphocladal group. properties of taphonic populations generated Similarly, the number of taphons of each by taphonomic elements. The study of subtaphoclade can serve as a relative taphonomic evolution is necessarily indicator of macroevolutionary success of historical, and ideas about what happened, each subtaphoclade of the same taphoclade. and how, can only be inferred from the

133 Taphonomic alteration remaining evidence (cf. Skelton, 1993: taphoclades, or the cases of stabilizing 511). Preservability of taphons and fossilization, correspond to the so-called taphoclades can only be assessed and tested “unaltered fossils", which have stayed in a retrospective way keeping in mind the apparently unchanged or showing minimum actual properties of the successive taphonic changes in their properties. Taphonomic populations and the successive taphons of elements without apparent changes, as some each taphoclade. This procedure allows Quaternary frozen remains, or some explaining the way representatives of some Cenozoic remains included in asphalt or in taphoclades (for example, the ammonite peat-bog deposits, as well as the Recent remains) have been able to be preserved, mummified remains, should be understood even being abundant in supratidal as representatives of taphonomic groups environments and in continental facies (as with minimum taphonization degrees, rather reelaborated internal moulds) beyond the than as unmodified taphonomic elements. limits of tolerance of the originally “Unaltered fossils” are usually scarcer produced taphonomic elements (i.e., the among the oldest taphons and, as a general aragonitic shells). rule, show relatively smaller changes in From a determinist approach, their primary characters. They usually macroevolutionary trends of fossilization present the maximum proportion of processes can be attributed, after being taphonomic characters in primitive state and tested, to some particular causes such as the minimum proportion in derived state. environmental changes, interactions Stable taphons or taphoclades, or “unaltered between taphons or the appearance of fossils", are taphonomic groups persistently evolutionary taphonomic novelties staying with a low population, taphonic or increasing the preservability of taphons and taphocladal diversity. Longevity of taphons taphoclades. From a probabilistic approach, has not influenced this result, because the however, it is necessary to take into account necessary condition is that the number of that macroevolutionary trends in taphons stays low, without undergoing fossilization processes may have been taphonization processes. Such taphonomic randomly achieved. Anyway, the different groups cannot be common, because low ways of change, as well as the taphocladal diversity values increase the probabilities of trends and paths of fossilization processes, destruction of a taphoclade. In contrast, resulting from the taphocladal alteration, “altered or varied fossils” correspond to can be classified into three categories: taphons or taphoclades that have reached, stabilizing or normalizing fossilization, by taphonization, higher values of taphonic directional fossilization and disruptive and taphocladal diversity than “unaltered fossilization. fossils". Cases of directional fossilization Stabilizing or normalizing comprise the fossils altered preferably in fossilization of a taphon or taphoclade, some sense, which represent taphons and similarly as taphonic retention, does not taphoclades of a certain composition and mean temporary invariance of actual structure. Disruptive fossilization comprises properties, but rather their composition and fossils altered simultaneously in several structure remaining with relatively similar senses, giving rise to taphons and values during fossilization. Stable taphoclades of different composition and

134 Fernández-López structure. Such taphonomic groups are On the other hand, the fossilization potential usually common, because high taphocladal of a particular environment with respect to a diversity values and processes of particular taxonomic group can be taphonomic dispersion diminish the understood as directly proportional to the probabilities of destruction of a taphoclade. production and import rates, and inversely proportional to the export and destruction rates, of taphonomic elements of this taxonomic Fossilization potential group. For example, the fossilization potential of a Mesozoic epicontinental platform Properties, activities and capacities of regarding the ammonite shells could reach taphonomic entities should not be confused maximum values in the distal and deep with other properties of the taphonomic environments or in the proximal and shallow systems, of the external environments of environments. Production of ammonite taphonomic alteration or of the sedimentary remains took place in general in open and environments in which fossilization deep marine platforms, but accumulation of processes take place. Neither should they be these remains was carried out in the mistaken with properties of the (palaeo) production place and also in other far away biological entities. In particular, the and shallow areas to those shells arrived by preservability or preservation potential of necroplanktic drift. In consequence, taphonic populations, taphons or taphoclades, fossilization potential of an epicontinental should be distinguished from the fossilization platform regarding ammonite shells could potential of palaeobiological entities, reach maximum values in the distal and different external environments or different deep environments and also in the sedimentary environments (cf. Schopf, 1978; proximal and shallow environments. The Plotnick et al., 1988; Mackensen et al., abundance or the concentration of ammonite 1990; Palmqvist, 1991; Hayes et al., 1993; shells in epicontinental platform deposits Fernández-López, 1995, 2000; Bromham et cannot be used as a directly proportional al., 1998; Orr et al., 1998; Goldstein and bathymetric indicator of depth of the Watkins, 1999; Hesse et al., 1999; Alba et sedimentary environments. However, instead al., 2001; Blake, 2000; Conway Morris, of the abundance or the concentration of 2000; Nowak et al., 2000; Scout et al., taphonomic elements, it is possible to use 2000; Morigi et al., 2001; Seilacher et al., other taphonomic properties of ammonite 2001; Seilacher, 2002; Walker et al., 2002; taphonic populations, taphons and Cady et al., 2003; Curran & Martin, 2003; taphoclades, such as the taphonomic clines Kowalewski & Flessa, 2003; Maeda et al., (Fernández-López, 1995; Fernández-López 2003; Wani, 2003; Krause, 2004; Lazo, & Meléndez, 1995). 2004; Waugh et al., 2004; Zaton & The term taphocline denotes a Marynowski, 2004). The fossilization continuous gradation in some character across potential of a palaeobiological entity in a the range of a taphon or a group of particular environment depends on phyletically related taphons, associated with palaeobiological factors (palaeoecological, some environmental gradient, which allow palaeobiogeographical and evolutionary), interpret the corresponding palaeoenvironmental productive factors and taphonomic factors. trend where the gradation has been formed.

135 Taphonomic alteration

Conclusions Renzi (University of Valencia, Spain) for their constructive comments and suggestions Taphonomic alteration means change by on the manuscript. This work is a contribution destruction or modification of taphonomic to the Project CGL2004-0694/BTE (MEC- individuals (taphonomic elements, taphonic CSIC). populations, taphonic associations, taphons or taphoclades) due to their interaction with the external environment. Structural properties References of taphonomic individuals allow distinguishing alteration processes at different levels: Alba, D.M., Agustí, J. & Moyà-Sola, S. (2001). Completeness of the mammalian fossil record in the Iberian elementary, populational, taphonic and Neogene. Paleobiology, 27: 79-83. taphocladal. Elementary alteration acts on Allison, P.A. & Briggs, D.E.G., eds. (1991). Taphonomy. taphonomic elements, eliminating those of Releasing the data locked in the fossil record. smaller durability and redundancy. Plenum Press, New York. Andrews, P. (1990). Owls, caves and fossils. Natural Populational alteration represents the group History Museum, London. effect on preservation potential of Badgley, C. (2003). The multiple scales of biodiversity. taphonomic elements of a same taphon. Paleobiology, 29: 11-13. Taphonic alteration acts on taphons, Bandyopadhyay, S., RoyChowdhury, T.K. & Sengupta, D.P. (2002). Taphonomy of some Gondwana eliminating those of smaller preservation vertebrate assemblages of India. Sedimentary potential. Taphocladal alteration implies Geology, 147: 219-245. destruction or modification of taphoclades. Beavington-Penney, S.J. (2004). Analysis of the effects The architecture of taphonomic elements of abrasion on the test of Palaeonummulites venosus: Implications for the origin of influences on the alteration of taphons and nummulithoclastic sediments. Palaios, 19: 143-155. on the trends in fossilization processes. Beerbower, J.R. & Jordan, D. (1969). Application of However, trends in processes of fossilization information theory to paleontologic problems: at different levels of the taphonomic taxonomic diversity. Journal of Paleontology, 43: 1184-1198. hierarchy can work in opposite directions. Behrensmeyer, A.K. (1978). The habitat of Plio- The characters lowering durability and Pleistocene hominids in East Africa: taphonomic redundancy of taphonomic elements can and microstratigraphic evidence. In (Jolly, C.J., cause taphonic retention and taphonization, ed.) Early Hominids of Africa. London: Duckworth, pp. 165-189. increase preservation potential and prevent Behrensmeyer, A.K. (1984). Taphonomy and the fossil destruction of taphons and taphoclades. record. American Scientist, 72: 558-566. Accepting the existence of taphonomic Behrensmeyer, A.K. & Kidwell, S.M. (1985). Taphonomy's modifications at different level of organization, contributions to paleobiology. Paleobiology, 11: 105- 119. evolutionary taphonomy provides a new method Behrensmeyer, A.K., Stayton, C.T. & Chapman, R.E. that increases the possibilities of analysis and (2003). Taphonomy and ecology of modern synthesis in taphonomic researches. avifaunal remains from Amboseli Park, Kenya. Paleobiology, 29: 52-70. Bell, C.M., Angseesing, J.P.A. & Townsend, M.J. (2001). A chondrophorine (medusoid hydrozoan) from the Acknowledgments Lower Cretaceous of Chile. Palaeontology, 44: 1011-1023. I would like to thank G. Meléndez Benton, M.J., Wills, M.A. & Hitchin, R. (2000). Quality of the fossil record through time. Nature, (University of Zaragoza, Spain) and M. De 403: 534-537.

136 Fernández-López

Berger, J.P. & Strasser, A., eds. (1994). Symposium Chave, K.E. (1964). Skeletal durability and preservation. taphonomy: How to be preserved after death? In (Imbrie, J. & Newell, N.D., eds.) Approaches to Eclogae Geologicae Helvetiae, 88: 617-720. Paleoecology. New York: J. Willey & Sons, pp. Best, M.M.R. & Kidwell, S.M. (2000). Bivalve taphonomy 377-387. in tropical mixed siliciclastic-carbonate settings. II. Conway Morris, S. (2000). The Cambrian ‘‘explosion’’: Effect of bivalve life habits and shell types. Slow-fuse or megatonnage? Proceedings of the Paleobiology, 26: 103-115. National Academy of Sciences of the United States Blake, D.B. (2000). The Class Asteroidea (Echinodermata): of America, 97: 4426-4429. Fossils and the base of the Crown Group. Crampton, J.S. (2004). Shell composition, cryptic American Zoologist, 40: 316-325. costae, complex composite molds, and taphonomic Brachert, T.C. & Dullo, W.C. (2000). Shallow burial chicanery in Mytiloides (Inoceramidae, Bivalvia). diagenesis of skeletal carbonates: aragonite shell Journal of Paleontology, 78: 1091-1096. material (Miocene to Recent, Queensland and Cummings, H., Powell, E.N., Stanton, R.J.Jr. & Staff, Queensland Trough, NE Australia) - implications cool- G. (1986). The rate of taphonomic loss on modern water carbonates. Sedimentary Geology, 136: 169-187. benthic habitats: how much of the potentially Bradshaw, C. & Scoffin, T.P. (2001). Differential preservable community is preserved? Palaeogeography, preservation of gravelsized bioclasts in Alpheid- Palaeoclimatology, Palaeoecology, 52: 291-320. versus Callianassid-bioturbated muddy reefal Curran, H.A. & Martin, A.J. (2003). Complex decapod sediments. Palaios, 16: 185-191. burrows and ecological relationships in modern Brand, L.R., Hussey, M. & Taylor, J. (2003). Decay and Pleistocene intertidal carbonate environments, and disarticulation of small vertebrates in San Salvador Island, Bahamas. Palaeogeography, controlled experiments. Journal of Taphonomy, 1: Palaeoclimatology, Palaeoecology, 192: 229-245 69-95. Davies, D.J., Powell, E.N. & Stanton, R.J.Jr. (1989). Brett, C.E. (1990). Destructive taphonomic processes Taphonomic signature as a function of environmental and skeletal durability. In (Briggs, D.E.G. & process: shells and shell beds in a hurricane- Crowther, P.R., eds.) Palaeobiology: a synthesis. influenced inlet on the Texas coast. Palaeogeography, Oxford: Blackwell Scientific Publications, pp. 223- Palaeoclimatology, Palaeoecology, 72: 317-356. 226. Delvene, G. (2003). Middle and Upper Jurassic bivalve Brett, C.E. & Baird, G.C. (1986). Comparative taphonomy: a associations from the Iberian Range (Spain). key to paleoenvironmental interpretation based on Geobios, 36: 519-531. fossil preservation. Palaios, 1: 207-227. De Renzi, M. (1995). Crítica del estratotipo puro. Bromham, L., Rambaut, A., Fortey, R., Cooper, A. & Geogaceta, 17: 3-8. Penny, D. (1998). Testing the Cambrian explosion De Renzi, M., Pardo Alonso, M.V., Belinchón, M., hypothesis by using a molecular dating technique. Peñalver, E., Montoya, P. & Márquez-Aliaga, A. Proceedings of the National Academy of Sciences eds. (2002). Current topics on taphonomy and of the United States of America, 95: 12386-12389. fossilization. International Conference Taphos Butler, V.L. & Schroeder, R.A. (1998). Do digestive 2002. Universidad de Valencia, Valencia. processes leave diagnostic traces on fish bones? Donovan, S.K. (1991). The processes of fossilization. Journal of Archaeological Science, 25: 957-971. Belhaven Press, London. Butterfield, N.J. (1995). Secular distribution of Burgess Donovan, S.K. (2002). Taphonomy. Geology Today, Shale-type preservation. Lethaia, 28: 1-13. 18: 226-231. Butterfield, N.J. (2003). Exceptional fossil preservation Efremov, J. A. (1940). Taphonomy: new branch of and the Cambrian explosion. Integrative and paleontology. Pan-American Geologist, 74: 81-93. Comparative Biology, 43: 166-177. Efremov, J. A. (1950). Taphonomie et annales géologiques. Butterfield, N.J. (2005). Probable Proterozoic fungi. Annales du Centre d'Etudes et de Documentation Paleobiology, 31: 165-182. Paléontologiques, 4 (1953): 1-196. Cady, S.L., Farmer, J.D., Schopf, J.W. & Steele, A. Fernández-López, S. (1982). La evolución tafonómica (2003). Morphological biosignatures and the (un planteamiento neodarwinista). Boletín de la search for life on Mars. Astrobiology, 3: 351-368. Real Sociedad Española de Historia Natural, Campbell, D.T. (1974). "Downward causation" in (Geología), 79 (1981): 243-254. hierarchically organized biological systems. In Fernández-López, S. (1984). Nuevas perspectivas de la (Ayala, F.J. & Dobzhansky, T., eds.) Studies in the Tafonomía evolutiva: tafosistemas y asociaciones Philosophy of Biology: Reductionism and Related conservadas. Estudios Geológicos, 40 (1983): 215- Problems. New York, Macmillan, pp. 179-186. 224.

137 Taphonomic alteration

Fernández-López, S. (1988). La Tafonomía: un Haglund, W.D. & Sorg, M.H., eds. (1997). Forensic subsistema conceptual de la Paleontología. taphonomy. The postmortem fate of human Coloquios de Paleontología, 41 (1986-1987): 9-34. remains. CRC Press, Washington. Fernández-López, S. (1989). La materia fósil. Una Harding, I.C. & Chant, L.S. (2000). Self-sedimented concepción dinamicista de los fósiles. In (Aguirre, diatom mats as agents of exceptional fossil E., ed.) Nuevas tendencias: Paleontología. Madrid: preservation in the Oligocene Florissant lake beds, Consejo Superior de Investigaciones Científicas, Colorado, United States. Geology, 28: 195-198. pp. 25-45. Harper, H.M. (2003). Assessing the importance of Fernández-López, S. (1991a). Taphonomic concepts drilling predation the Palaeozoic and Mesozoic. for a theoretical Biochronology. Revista Española Palaeogeography, Palaeoclimatology, Palaeoecology, de Paleontología, 6: 37-49. 210: 185-198. Fernández-López, S. (1991b). Sistemas tafonómicos: Harvey, E.L. & Fuller, D.Q. (2005). Investigating crop función y evolución. Revista Española de processing using phytolith analysis: the example of Paleontología, vol. extraordinario: 21-34. rice and millets. Journal of Archaeological Fernández-López, S. coord. (1992). Conferencias de la Science, 32: 739-752. Reunión de tafonomía y fosilización. Editorial Hayes, M.L., Johnson, M.E. & Fox, W.T. (1993). Complutense, Madrid Rocky-shore biotic associations and their fossilization Fernández-López, S. (1995). Taphonomie et potential: Isla Requeson (Baja California Sur, interprétation des paléoenvironnements. Geobios, Mexico). Journal of Coastal Research, 9: 944-957. M.S. 18: 137-154. Hesse, M., Weber, M. & Halbritter, H.M. (1999). Fernández-López, S. (1999). Tafonomía y Fosilización. Pollen walls of Araceae, with special reference to In (Meléndez, B., ed., 1998) Tratado de their fossilization potential. Grana, 38: 203-209. Paleontología. Madrid: Consejo Superior de Hoffmeister, A.P., Kowalewski, M., Baumiller, T.K. & Investigaciones Científicas, pp. 51-107. Bambach, R.K. (2004). Drilling predation on Fernández-López, S.R. (2000). Temas de Tafonomía. Permian brachiopods and bivalves from the Glass Departamento Paleontología, Universidad Mountains, west Texas. Acta Palaeontologica Complutense de Madrid. Polonica, 49: 443-454. Fernández-López, S. & Meléndez, G. (1995). Holmes, K.M., Robson Brown, K.A., Oates, W.P. & Taphonomic gradients in Middle Jurassic Collins, M.J. (2005). Assessing the distribution of ammonites of the Iberian Range (Spain): Geobios, African Palaeolithic sites: a predictive model of M.S. 18: 55-165. collagen degradation. Journal of Archaeological Flessa, K.W. & Brown, T.J. (1983). Selective solution Science, 32: 157-166 of macroinvertebrate calcareous hard parts: a Holtzman, R.C. (1979). Maximum likelihood estimation laboratory study. Lethaia, 16: 193-205. of fossil assemblage composition. Paleobiology, 5: Gaines, R.R., Kennedy, M.J. & Droser, M.L. (2005). A 77-89. new hypothesis for organic preservation of Burgess Holz, M. & Simões, M. (2002). Elementos fundamentais Shale taxa in the middle Cambrian Wheeler de tafonomia. Editora da Universidade, Formation, House Range, Utah. Palaeogeography, Universidade Federal do Rio Grande do Sul. Palaeoclimatology, Palaeoecology, 220: 193-205. Hoppe, K.A., Koch, P.L. & Furutani, T.T. (2003). Goldstein, S.T. & Watkins, G.T. (1999). Taphonomy Assessing the preservation of biogenic strontium in of salt marsh foraminifera: an example from coastal fossil bones and tooth enamel. International Georgia. Palaeogeography, Palaeoclimatology, Journal of Osteoarchaeology, 13: 20-28. Palaeoecology, 149: 103-114. Janin, B.T. (1983). Osnovy Tafonomii. Nedra, Moscow. Gould, S.J. (2002). The structure of evolutionary Jensen, S., Droser, M.L. & Gehling, J.G. (2005). Trace theory. The Belknap Press, Harvard University, fossil preservation and the early evolution of Cambridge. animals. Palaeogeography, Palaeoclimatology, Greenstein, B.J. & Pandolfi, J.M. (2003). Taphonomic Palaeoecology, 220: 19-29. alteration of reef corals: effects of reef Jones, B., Konhauser, K.O., Renaut, R.W. & Wheeler, environment and coral growth form II. The Florida R.S. (2004). Microbial silicification in Iodine Pool, Keys. Palaios, 18: 495-509. Waimangu geothermal area, North Island, New Gupta, N.S. & Pancost, R.D. (2004). Biomolecular and Zealand: implications for recognition and physical taphonomy of angiosperm leaf during identification of ancient silicified microbes. early decay: Implications for fossilization. Palaios, Journal of the Geological Society, London, 161: 19: 428-440. 983-993.

138 Fernández-López

Jones, B., Renaut, R.W. & Rosen, M.R. (2001). unifying theory of sedimentary particles. The Taphonomy of silicified filamentous microbes in Journal of Geology, 111: 427-439. Modern geothermal sinters - Implications for Krause, R.A.Jr. (2004). An assessment of morphological identification. Palaios, 16: 580-592. fidelity in the sub-fossil record of a terebratulide Kershaw, S. & Brunton, F.R. (1999). Palaeozoic brachiopod. Palaios, 19: 460-476. stromatoporoid taphonomy: ecologic and environmental Kroh, A. & Nebelsick, J.H. (2003). Echinoid significance. Palaeogeography, Palaeoclimatology, assemblages as a tool for palaeoenvironmental Palaeoecology, 149: 313-328. reconstruction - an example from the Early Miocene Kidwell, S.M. (1989). Stratigraphic condensation of of Egypt. Palaeogeography, Palaeoclimatology, marine transgressive records: origin of major shell Palaeoecology, 201: 157-177. deposits in the Miocene of Maryland. Journal of Lawrence, D.R. (1968). Taphonomy and information Geology, 97: 1-24. losses in fossil communities. Bulletin of the Kidwell, S.M. (2000). Major biases in the fossil record. Geological Society of America, 79: 1315-1330. In (Briggs, D.E.G. & Crowther, P.R., eds.) Lawrence, D.R. (1979). Taphonomy. In (Fairbridge, Palaeobiology II. London: Blackwell Scientific, R.W. & Jablonski, D., eds.) The Encyclopedia of pp. 297-333. Paleontology. Stroudsburg: Hutchinson & Ross, Kidwell, S.M. (2002a). Time-averaged molluscan pp. 793-799. death assemblages: Palimpsests of richness, Lazo, D.G. (2004). Bivalve taphonomy: Testing the snapshots of abundance. Geology, 30: 803-806. effect of life habits on the shell condition of the Kidwell, S.M. (2002b). Mesh-size effects on the Littleneck clam Protothaca (Protothaca) staminea ecological fidelity of death assemblages: a meta- (Mollusca: Bivalvia). Palaios, 19: 451-459. analysis of molluscan live-dead studies. Geobios, Lockwood, R. (2003). Abundance not linked to Mémoire spécial 24: 107-119. survival across the end-Cretaceous mass Kidwell, S.M. & Bosence, D.W.J. (1991). Taphonomy extinction: Patterns in North American bivalves. and time-averaging of marine shelly faunas. In Proceedings of the National Academy of Sciences (Allison, P.A. & Briggs, D.E., eds.) Taphonomy. of the United States of America, 100: 2478-2482. Releasing the data locked in the fossil record. New Lyman, R.L. (1994). Vertebrate Taphonomy. Cambridge York: Plenum Press, pp. 115-209. Manuals in Archaeology, Cambridge. Kidwell, S.M. & Flessa, K.W. (1996). The quality of Mackensen, A., Grobe, H., Kuhn, G. & Fütterer, D.K. the fossil record: populations, species and (1990). Benthic foraminiferal assemblages from communities. Annual Review Earth and Planetary the eastern Weddell Sea between 68 and 73ºS: Science, 24: 433-464. distribution, ecology and fossilization potential. Kidwell, S.M. & Holland, S.M. (2000). The quality of Marine Micropaleontology, 16: 241-283. the fossil record: Implications for evolutionary Mckinney, F. (2003). Preservation potential and paleoecological analyses. Annual Review of Ecology, Evolution, significance of epibenthic suspension feeder-dominated and Systematics, 2002, 33: 561-88. benthic communities (Northern Adriatic Sea). Palaios, 18: Kidwell, S.M. & Jablonski, D. (1983). Taphonomic 47-62. feedback. Geological consequences of shell Maeda, H., Mapes, R.H. & Mapes, G. (2003). accumulation. In (Tevesz, M.J.S. & McCall, P.L., Taphonomic features of a Lower Permian beached eds.) Biotic interactions in recent and fossil benthic cephalopod assemblage from Central Texas. communities. New York: Plenum Press, pp. 195-248. Palaios, 18: 421-434. Kowalewski, M. (1997). The reciprocal taphonomic Martin, D., Briggs, D.E.G. & Parkes, R.J. (2004). model. Lethaia, 30: 86-88. Experimental attachment of sediment particles to Kowalewski, M. & Bambach, R.K. (2003). The limits invertebrate eggs and the preservation of soft- of paleontological resolution. In (Harries, P.J., ed.) bodied fossils. Journal of the Geological Society, Approaches in High-Resolution Stratigraphic London, 161: 735-738. Paleontology. New York: Kluwer Academic / Martin, R.E. (1999). Taphonomy. A process approach. Plenum Publishers, pp. 1-48. Cambridge Paleobiology Series, 4: 1-508. Kowalewski, M. & Flessa, K.W. (2003). Improving Martínez-Delclòs, X., Briggs, D.E.G. & Peñalver, E. (2004). with age: The fossil record of lingulide Taphonomy of insects in carbonates and amber. brachiopods and the nature of taphonomic Palaeogeography, Palaeoclimatology, Palaeoecology, megabiases. Geology, 24: 977-980. 203, 19-64. Kowalewski, M. & Rimstidt, J.D. (2003). Average Mckinney, F.K. (2003). Preservation potential and lifetime and age spectra of detrital grains: toward a paleoecological significance of epibenthic

139 Taphonomic alteration

suspension feeder-dominated benthic communities evaporitic carbonatic). Earth-Science Reviews, 62: (Northern Adriatic Sea). Palaios, 18: 47-62. 163-176. Meldahl, K.H. (1987). Sedimentologic and taphonomic Nowak, R.S., Nowak, C.L. & Tausch, R.J. (2000). implications of biogenic stratification. Palaios, 2: Probability that a fossil absent from a sample is 350-358. also absent from the paleolandscape. Quaternary Meléndez Hevia, G., coord. (1997). Tafonomía y Research, 54: 144-154. fosilización. Cuadernos de Geología Ibérica, 23: Orr, P.J., Briggs, D.E.G. & Kearns, S.L. (1998). 1-300. Cambrian Burgess shale animals replicated in clay Meléndez Hevia, G. (2004). La tafonomía evolutiva Minerals. Science, 281: 1173-1175. como un programa de investigación: aspectos Oyen, C.W. & Portell, R.W. (2001). Diversity patterns epistemológicos. In (Baquedano, E. & Rubio Jara, and biostratigraphy of Cenozoic echinoderms from S., eds.) Miscelánea en homenaje a Emiliano Florida. Palaeogeography, Palaeoclimatology, Aguirre, Volumen II, Paleontología. Zona Palaeoecology, 166: 193-218. Arqueológica, 4: 307-319. Palanti, S., Susco, D. & Torniai, A.M. (2004). The Meléndez Hevia, G., Blasco Sancho, Mª.F. & Pérez-Urresti, resistance of Dunarobba fossil forest wood to I., eds. (1996). II Reunión de Tafonomía y Fosilización. decay fungi and insect colonization. International Institución "Fernando el Católico" (CSIC), Zaragoza. Biodeterioration and Biodegradation, 53: 89-92. Messina, C. & Labarbera, M. (2004). Hydrodynamic Palmqvist, P. (1991). Differences in the fossilization behavior of brachiopod shells: experimental potential of bivalves and gastropod species related estimates and field observations. Palaios, 19: 441- to their life sites and trophic resources. Lethaia, 24: 450. 287-288. Moffat, H.A. & Bottjer, D.J. (1999). Echinoid Peebles, M.W. & Lewis, R.D. (1988). Differential concentration beds: two examples from the stratigraphic infestation of shallow-water benthic foraminifera spectrum. Palaeogeography, Palaeoclimatology, by microboring organisms: possible biases in Palaeoecology, 149: 329-348. preservation potential. Palaios, 3: 345-351. Morigi, C., Jorissen, F.J., Gervais, A., Guichard, S. & Perry, T.C. (1998). Grain susceptibility to the effects of Borsetti, A.M. (2001). Benthic foraminiferal microboring: implications for the preservation of faunas in surface sediments off NW Africa: skeletal carbonates. Sedimentology, 45: 39-51. relationship with organic flux to the ocean floor. Perry, T.C. (1999). Biofilm-related calcification, Journal of Foraminiferal Research, 31: 350-368. sediment trapping and constructive micrite envelops: Müller, A.H. (1951). Grundlagen der Biostratonomie. a criterion for the recognition of ancient grass-bed Abhandlungen aus dem deutsche Akademie der environments? Sedimentology, 46: 33-45. Wissenschaften zu Berlin, 1959: 1-147. Petrovich, R. (2001). Mechanisms of fossilization of Müller, A.H. (1979). Fossilization (Taphonomy). In the soft-bodied and lightly armored faunas of the (Robinson, R.A. & Teichert, C., eds.), Treatise on Burgess Shale and of some other classical lnvertebrate Paleontology, Part A, Introduction. localities. American Journal of Science, 3001: 683- Boulder, Colorado: Geological Society of America 726. and University of Kansas Press, pp. A2-A78. Pickering, T.R. & Carlson, K.J. (2002). Baboon Bone Nebelsick, J. (1999). Taphonomic comparison between Mineral Densities: Implications for the Taphonomy Recent and fossil sand dollars. Palaeogeography, of Primate Skeletons in South African Cave Sites. Palaeoclimatology, Palaeoecology, 149: 349-358. Journal of Archaeological Science, 29: 883-896. Nebelsick, J. & Kroh, A. (2002). The stormy path from Plotnick, R.E., Baumiller, T. & Wetmore, K.L. (1988). life to death assemblages: the formation and Fossilization potential of the mud crab, Panopeus preservation of mass accumulations of fossil sand (brachyura: Xanthidae) and temporal variability in dollars. Palaios, 17: 378-393. crustacean taphonomy. Palaeogeography, Nielsen, J.K. & Funder, S. (2003). Taphonomy of Palaeoclimatology, Palaeoecology, 63: 27-43. Eemian marine molluscs and acorn barnacles from Powell, E.N., Callender, W.R. & Stanton, R.J.Jr. (1998). eastern Arkhangelsk region, northern Russia. Can shallow- and deep-water chemoautotrophic and Palaeogeography, Palaeoclimatology, Palaeoecology, heterotrophic communities be discriminated in the 191: 139-168. fossil record? Palaeogeography, Palaeoclimatology, Noffke, N., Gerdes, G. & Klenke, T. (2003). Benthic Palaeoecology, 144: 85-114. cyanobacteria and their influence on the Rickards, R.B. & Wright, A.J. (2002). Lazarus taxa, sedimentary dynamics of peritidal depositional refugia and relict faunas: evidence of graptolites. systems (siliciclastic, evaporitic salty, and Journal of the Geological Society, London, 159: 1-4.

140 Fernández-López

Robinson, S., Nicholson, R.A., Pollard, A.M. & Skelton, P. (1993). Evolution. Addison-Wesley O’Connor, T.P. (2003). An evaluation of nitrogen Publishing Company, Wokingham. porosimetry as a technique for predicting Smith, A.M. & Nelson, C.S. (2003). Effects of early taphonomic durability in animal bone. Journal of sea-floor processes on the taphonomy of temperate Archaeological Science, 30: 391-403. shelf skeletal carbonate deposits. Earth-Science Rodland, D.L., Kowalewski, M., Carroll, M. & Reviews, 63: 1-31. Simões, M.G. (2004). Colonization of a ‘Lost Smith, C.I., Craig, O.E., Prigodich, R.V., Nielsen- World’: encrustation patterns in Modern Marsh, C.M., Jans, M.M.E., Vermeer, C. & subtropical brachiopod assemblages. Palaios, 19: Collins, M.J. (2005). Diagenesis and survival of 381-395. osteocalcin in archaeological bone. Journal of Schieber, J. (2002). Sedimentary pyrite: A window into Archaeological Science, 32: 105-113. the microbial past. Geology, 30. 531-534. Smith, G.M. (2003). Damage inflicted on animal bone Schopf, T. J. M. (1978). Fossilization potential of an by wooden projectiles: experimental results and intertidal fauna: Friday Harbor, Washington. archaeological implications. Journal of Taphonomy, Paleobiology, 4: 261-270. 1: 105-114. Schweitzer, M.H. (2004). Molecular paleontology: Tapanila, L., Roberts, R.M., Bouar, M. L., Sissoko, F. some current advances and problems. Annales de & O’Leary, M.A. (2004). Bivalve borings in Paléontologie, 90: 81-102. phosphatic coprolites and bone, Cretaceous- Scout, A.C., Cripps, J.A., Collinson, M.E. & Nichols, Paleogene, northeastern Mali. Palaios, 19: 565-573. G.J. (2000). The taphonomy of charcoal following Tasch, P. (1965). Communications theory and the a recent heathland fire and some implications for the fossil record of Invertebrates. Transactions of the interpretation of fossil charcoal deposits. Kansas Academy of Sciences, 68: 322-329. Palaeogeography, Palaeoclimatology, Palaeoecology, Tasch, P. (1969). Information theory applied to 164: 1-31. Invertebrate fossils. Transactions of the Kansas Seilacher, A. (1992). Dynamic taphonomy: The Academy of Sciences, 72: 195-201. process-related view of fossil-lagerstaetten. In: Tasch, P. (1973). Paleobiology of the Invertebrates. Conferencias de la Reunión de Tafonomía y Data retrieval from the fossil record. John Wiley Fosilización. S. Fernández-López, Coord. págs. and Sons, New York. 109-125. Editorial Complutense, Madrid. Terry, R. (2004). Owl pellet taphonomy: A preliminary Seilacher, A. (2002). Non olet: The strange taphonomy study of the post-regurgitation taphonomic history of coprolites and cololites. In: Current Topics on of pellets in a temperate forest. Palaios, 19: 497- Taphonomy and Fossilization. M. De Renzi; M.V. 506. Pardo Alonso; M. Belinchón; E. Peñalver; P. Tomasovych, A. (2004a). Effect of extrinsic factors on Montoya & A. Márquez-Aliaga, Eds., págs. 233- biofabric and brachiopod alteration in a shallow 240. Ajuntament de Valencia, Valencia. intraplatform carbonate setting (Upper Triassic, Seilacher, A., Reif, W.E. & Westphal, F. (1985). West Carpathians). Palaios, 19: 349-371. Sedimentological, ecological and temporal patterns Tomasovych, A. (2004b). Postmortem durability and of fossil Lagerstätten. Philosophical Transactions population dynamics affecting the fidelity of of the Royal Society of London, 311B: 5-23. brachiopod size-frequency distributions. Palaios, Seilacher, A., Marshall, C., Skinner, H.C.W. & 19: 477-496. Tsuihiji, T. (2001). A fresh look at sideritic Trapani, J. (1998). Hydrodynamic sorting of avian ‘‘coprolites’’. Paleobiology, 27: 7-13. skeletal remains. Journal of Archaeological Shipman, P. (1981). Life history of a fossil. Harvard Science, 25: 477-487. University Press, Cambridge. Trueman, C.N., Benton, M.J. & Palmer, M.R. (2003). Shipman, P. (2001). What can you do with a bone Geochemical taphonomy of shallow marine fragment? Proceedings of the National Academy of vertebrate assemblages. Palaeogeography, Sciences of the United States of America, 98: 1335- Palaeoclimatology, Palaeoecology, 197: 151-169. 1337. Tsujita, C.J. (2003). Smothered scampi: taphonomy of Simões, M.G., Kowalewski, M., Torello, F.F., lobsters in the Upper Cretaceous Bearpaw Formation, Ghilardi, R.P. & Mello, L.H.C. (2000). Early onset Southern Alberta. Journal of Taphonomy, 1: 187-206. of modern-style shell beds in the Permian Walker, S.E., Parsons-Hubbard, K., Powell, E. & Brett, sequences of the Paraná Basin: implications for the C.E. (2002). Predation on experimentally deployed Phanerozoic trend in bioclastic accumulations. molluscan shells from shelf to slope depths in a Revista Brasileira de Geociencias, 30: 495-499. tropical carbonate environment. Palaios, 17: 147-170.

141 Taphonomic alteration

Wani, R. (2003). Taphofacies models for Upper Zaton, M. & Marynowski, L. (2004). Konzentrat- Cretaceous ammonoids from the Kotanbetsu area, Lagerstätte-type carbonate concretions from the northwestern Hokkaido, Japan. Palaeogeography, uppermost Bajocian (Middle Jurassic) of the Palaeoclimatology, Palaeoecology, 199: 71-82. Czêstochowa area, South-Central Poland. Waugh, D.A., Feldmann, R.M., Crawford, R.S., Jakobsen, Geological Quarterly, 48: 339-350. S.L. & Thomas, K.B. (2004). Epibiont preservational Zhu, M., Babcock, L.E. & Steiner, M. (2005). and observational bias in fossil marine decapods. Fossilization modes in the Chengjiang Lagerst7tte Journal of Paleontology, 78: 961-972. (Cambrian of China): testing the roles of organic Weissbrod, L., Dayan, T., Kauffman, D. & Weinstein- preservation and diagenetic alteration in exceptional Evron, M. (2005). Micromammal taphonomy of el- preservation. Palaeogeography, Palaeoclimatology, Wad Terrace, Mount Carmel, Israel: distinguishing Palaeoecology, 220: 31-46. cultural from natural depositional agents in the Late Zuschin, M. & Stanton, R.J.Jr. (2001). Experimental Natufian. Journal of Archaeological Science, 32: 1-7. measurement of shell strength and its taphonomic Wilson, M.V.H. (1988). Taphonomic processes: information loss interpretation. Palaios, 16: 161-170. and information gain. Geoscience Canada, 15: 131-148. Zuschin, M., Hohenegger, J. & Steininger, F.F. (2000). Wings, O. (2004). Authigenic minerals in fossil bones A comparison of living and dead molluscs on coral from the Mesozoic of England: poor correlation reef associated hard substrata in the northern Red Sea with depositional environments. Palaeogeography, - implications for the fossil record. Palaeogeography, Palaeoclimatology, Palaeoecology, 204: 15-32. Palaeoclimatology, Palaeoecology, 159: 167-190. Whittington, H.B. & Conway Morris, S., eds. (1985). Zuschin, M., Stachowitsch, M. & Stanton, R.J.Jr. (2003). Extraordinary fossil biotas: their ecological and Patterns and processes of shell fragmentation in evolutionary significance. Philosophical Transactions modern and ancient marine environments. Earth- the Royal Society of London, B311: 1-192. Science Reviews, 63: 33-82.

142