Vertebrate Taphonomy Research Articles

Vertebrate taphonomy and taphofacies of the Capianga Member, Aliança Formation (Jurassic), Jatobá Basin, Brazil

In addition to the study of sedimentary facies, the reconstruction of paleoenvironments depends on a detailed understanding of the taphonomy of a fossil accumulation. The Capianga Member of the Aliança Formation (Middle to Late Jurassic of the Jatobá Basin, northeastern Brazil) reveals vertebrate fossil accumulations composed predominantly of disarticulated bone and osteoderms, scales, spines and isolated teeth from a lacustrine paleoenvironment. However, the taphonomic history of the accumulation has not yet been studied extensively. The present work aims to interpret taphonomic facies based on lithological data and the systematic collection of fossils from the Capianga Member of the Aliança Formation, located in the northeastern portion of the Jatobá Basin, mainly in the municipality of Ibimirim. Six lithofacies were identified: Fm – massive claystones, Fl – Shale laminated Lt – calcilutites, Lc – calcarenites, Gf – fibrous gypsum and Scl – calciferous sandstones. Two primary taphonomic classes were recognized, consisting essentially of disarticulated elements, including (1) incomplete, semi-complete, or rarely complete bioclasts (such as osteoderms and fish scales) and (2) small-sized, occasionally complete bioclasts (osteoderms and scales) that sometimes compose bonebeds. According to the vertebrate taphonomy characteristics, three taphofacies were identified, with the Taphofacies A and B occurring in calcarenites and the Taphofacies C in calcilutites. The interpretation of these taphofacies reveals a multi-episodic history of the lacustrine environment. The integrated model suggests that the genesis of the identified taphofacies is linked to the action of lowering the water level of the paleolake, as well as the agents responsible for transport and disarticulation. These agents are related to pre-burial sub-aerial exposure, the action of unidirectional turbidity currents in shallow waters, and the likely influence of storms.

Fossilized anuran soft tissues reveal a new taphonomic model for the Eocene Geiseltal Konservat-Lagerstätte, Germany

The Eocene Geiseltal Konservat-Lagerstätte (Germany) is famous for reports of three dimensionally preserved soft tissues with sub-cellular detail. The proposed mode of preservation, direct replication in silica, is not known in other fossils and has not been verified using modern approaches. Here, we investigated the taphonomy of the Geiseltal anurans using diverse microbeam imaging and chemical analytical techniques. Our analyses confirm the preservation of soft tissues in all body regions but fail to yield evidence for silicified soft tissues. Instead, the anuran soft tissues are preserved as two layers that differ in microstructure and composition. Layer 1 comprises sulfur-rich carbonaceous microbodies interpreted as melanosomes. Layer 2 comprises the mid-dermal Eberth–Katschenko layer, preserved in calcium phosphate. In addition, patches of original aragonite crystals define the former position of the endolymphatic sac. The primary modes of soft tissue preservation are therefore sulfurization of melanosomes and phosphatization of more labile soft tissues, i.e., skin. This is consistent with the taphonomy of vertebrates in many other Konservat-Lagerstätten. These findings emphasize an emerging model for pervasive preservation of vertebrate soft tissues via melanosome films, particularly in stagnation-type deposits, with phosphatization of more labile tissues where tissue biochemistry is favorable.

NOT ENTIRELY ICHTHYOSAUR: A MYSTERIOUS LAMNIFORM AND ICHTHYOPTERYGIAN-FALL ASSOCIATION FROM THE ABYSSAL UPPER CRETACEOUS OF THE NORTHERN APENNINES (ITALY)

ABSTRACT Axial remains of a large ichthyosaur and a medium-sized anacoracid shark from the deep-water sediments of the Cenomanian of the Northern Apennines (Northern Italy) are described in detail. The specimens were found closely associated (less than 0.3 m apart), and offer an invaluable window into the taphonomy and dead-fall stages of pelagic vertebrates in a Mesozoic abyssal plain. The anacoracid shark remains, initially misinterpreted as an ichthyosaur, consist of eight articulated vertebrae embedded in a block of dark arenaceous matrix, and represent the first occurrence of an articulated shark from the Northern Apennines. The ichthyosaur remains consist of seven discoidal vertebrae and several unidentified fragments. Due to the absence of diagnostic skeletal elements, both specimens are assigned only at higher taxonomic levels. The two fossils, which come from the same outcrop and possibly from the same stratigraphic horizon, share a common taphonomic history, in terms of both their preservation and diagenesis. Mineralogy of the matrices of both is dominated by manganese micro-nodules, consistent with the deposition of polymetallic nodules in bathyal-abyssal settings. Biostratinomic processes that impacted the two specimens also provide insight on the development of Mesozoic marine vertebrate-falls in the deep-sea. Localized pyrite framboids inside the bone spongiosa are possible evidence of the sulfophilic stage (microbially mediated sulfur mobilization during lipid decay) in the ichthyosaur fall. Burrows assigned to Taenidium on the surface of the shark block, interpreted as worm-like feeding burrows or arthropod locomotion and feeding trails, might represent evidence of the enrichment opportunistic stage. Although intriguing, we have no evidence to support the hypothesis that this peculiar association of two pelagic predators is due to ecological interaction between the two animals.

Vertebrate Taphonomy and Diagenesis: Implications of Structural and Compositional Alterations of Phosphate Biominerals

Biominerals are recorders of evolution and palaeoenvironments. Predation is one of the most frequent modes leading to the concentration of small vertebrates in fossil assemblages. Consumption by predators produces damages on bones and teeth from prey species, and one of the greatest challenges to taphonomists is differentiating original biological and secondary, geologically altered attributes of fossils. Excellent morphological preservation is often used to assume that the structure and composition of fossils are not modified. Nevertheless, during predation and fossilization, both the physical structure and chemical composition of enamel, dentine and bone are altered, the degree and extent of which varies from site to site, depending on the nature of the burial environment. A relationship between the surficial alterations and the compositional changes which take place during fossilization has yet to be established. Herein, I present a review of old and recent taphonomic studies that collectively reveal the wide diversity of microstructural and chemical changes that typically take place during fossilization of vertebrate remains, including common taphonomic biases and the challenges inherent to reconstructing the history of vertebrate fossil assemblages.

Taphonomy of marine vertebrates of the Pisco Formation (Miocene, Peru): Insights into the origin of an outstanding Fossil-Lagerstätte.

The Miocene Pisco Formation, broadly exposed in the Ica Desert of southern Peru, is among the most outstanding Cenozoic marine Fossil-Lagerstätten worldwide. It is renowned for its exceptional preservation and abundance of vertebrate fossils, including a rich assemblage of whales and dolphins (Cetacea). Here, we integrate taphonomic data on 890 marine vertebrate fossils, gathered through 16 different localities. Our observations range from the taxonomic distribution, articulation, completeness, disposition and orientation of skeletons, to the presence of bite marks, associations with shark teeth and macro-invertebrates, bone and soft tissue preservation, and the formation of attendant carbonate concretions and sedimentary structures. We propose that the exceptional preservation characterising many Pisco vertebrates, as well as their exceptionally high abundance, cannot be ascribed to a single cause like high sedimentation rates (as proposed in the past), but rather to the interplay of several favourable factors including: (i) low levels of dissolved oxygen at the seafloor (with the intervention of seasonal anoxic events); (ii) the early onset of mineralisation processes like apatite dissolution/recrystallisation and carbonate mineral precipitation; (iii) rapid burial of carcasses in a soupy substrate and/or a novel mechanism involving scour-induced self-burial; and (iv) original biological richness. Collectively, our observations provide a comprehensive overview of the taphonomic processes that shaped one of South America’s most important fossil deposits, and suggest a model for the formation of other marine vertebrate Fossil-Lagerstätten.

Contextual taphonomy for zooarchaeology: Theory, practice and select Levantine case studies

Contextual taphonomy is an archaeological approach that integrates taphonomic variables with stratigraphy and context, often at the intra-site level. A majority of zooarchaeological research explores vertebrate taphonomy broadly by entire temporal levels of sites, thus aggregating multiple contexts by time period. Yet, an increasing number of high-resolution studies go beyond this level to explore taphonomy per context or by other meaningful intra-site divisions. This approach marshals the rich information offered by the well-established discipline of taphonomy to build depositional histories of site features that contain bones, thereby revealing their formation and use. Here, we aim to better formalize the definition of contextual taphonomy for zooarchaeology and demonstrate its great applicability through select case studies in Israel. In this summary of the approach for the Special Issue on “Contextual Taphonomy in Zooarchaeological Practice”, we lay out the main requirements for multi-scalar contextual analysis and caution against potential pitfalls. Ultimately, archaeofaunal taphonomic studies at the context level are pertinent for myriad research questions, including those of refuse maintenance, camp organization and feasting.

Bioerosion on vertebrate remains from the Upper Cretaceous of the Haţeg Basin, Romania and its taphonomic implications

Bioerosion on fossil bones offers significant insights into both trophic relationships of ancient ecosystems and vertebrate taphonomy. Here we report six distinct trace fossil categories identified on isolated turtle, crocodyliform and dinosaur remains from the Upper Cretaceous Sînpetru Formation of the Haţeg Basin (Romania), for which five different probable tracemakers are identified: (1) termites, (2) dermestid beetles, (3) multituberculate mammals, (4) ziphodont theropod dinosaurs or crocodyliforms, and (5) plants. This extraordinary diversity of bioerosional trace fossils on vertebrate remains reveals insect-vertebrate as well as vertebrate-vertebrate interactions previously undocumented in the continental uppermost Cretaceous of Romania. The association between different traces, especially since many of these are superimposed on top of each other, allows the reconstruction of the detailed taphonomic history of the specimens, indicating four different taphonomic pathways. The vertebrate remains with trace fossils described here were most likely exposed to post-mortem biotic interactions for a prolonged time period before they were transported and/or trampled and finally buried. In the palaeoenvironmental context of a heterogeneous braided river system with low-lying wetlands and more elevated drylands, the death of the vertebrates as well as the scavenging likely occurred on the drylands.

Porcupine gnaw marks on a Late Pliocene bone from the Upper Siwaliks exposed near Village Khetpurali (Haryana, India).

Bone accumulation by porcupines at archaeological sites is well known. However, in paleontological sites such a taphonomical occurrence is rather rare. We here report porcupine (Hystrix sp.) gnaw marks on an unidentified bone fragment, dated to ~2.6 Ma from the Upper Siwalik deposits exposed near Khetpurali (Haryana), India. The present gnaw marks are very distinct and are characterized by visible edges and grooves making clear broad and shallow furrows. The present find adds to our knowledge of Siwalik vertebrate taphonomy where most of the accumulations reported earlier were either fluvial or made by carnivores.

Overlapping paleoichnology, paleoecology and taphonomy: Analysis of tooth traces in a Late Pleistocene-early Holocene megafaunal assemblage of Brazil and description of a new ichnotaxon in hard substrate

Tooth traces are key evidence in vertebrate taphonomy, paleoecology and paleoichnology. They are product of feeding behavior of vertebrates and can also be evaluated in biostratinomic perspective. Regarding the Quaternary fossil record of vertebrates in Brazil, the taphonomic-paleoecological information of tooth traces has been underexplored. Recently, features of this sort were identified in Quaternary mammals fossils recovered from Lajedo da Escada caves, state of Rio Grande do Norte, northeastern Brazil, consisting in an opportunity to unveil taphonomic, paleoichnological and paleoecological aspects of the Quaternary megafauna. The ichnospecies Machichnus bohemicus and M. fatimae are recorded in the Late Pleistocene-early Holocene age. The latter is a new ichnospecies of Machichnus described herein. The traces M. fatimae and M. bohemicus observed in Glyptotherium sp. were generated outside the cave by an adult individual of the large-sized canid Protocyon troglodytes during event of predation. Nonetheless, M. bohemicus recognized in Eremotherium laurillardi and Smilodon populator was generated by either a juvenile individual of P. troglodytes or an adult of the small-sized canid Cerdocyon thous, in a scavenging context, outside the cave. Probably, other tooth traces previously reported to the Quaternary of Brazil (in the states of Ceará and Minas Gerais) can be assigned to Machichnus.

Classifying vertebrate assemblages preserved in Quaternary tank deposits: Implications for vertebrate taphonomy and paleoecology

Paleoecological interpretations require detailed taphonomic analyses which can reveal how fossil accumulations are related to the original site of life and death of organisms. In other words, only a taphonomic approach can unveil the quality of a fossil concentration and its potential for paleoecology. A frequent issue in vertebrate taphonomy and paleoecology is the definition of autochthony, parautochthony and allochthony. These terms are widely employed to translate the spatial quality of a fossil assemblage. However, its application in terrestrial vertebrate accumulations, especially in natural tank ones, is quite confused. This work proposes a form of classification of fossil vertebrate accumulations of natural tanks in relation to their proximity to the original place of death of the biocoenoses. The terms “autochthonous”, “parautochthonous” and “allochthonous”, originally defined based on the analysis of marine shelly faunas are reinterpreted in attempt to clarify their application to vertebrate assemblages preserved in natural tank deposits. This classification can also be applied to other trap assemblages, such as fissures, sinkholes and caves.

Sedimentology and vertebrate taphonomy of the Moradi Formation of northern Niger: A Permian wet desert in the tropics of Pangaea

Pangaean paleogeographic models place the Tim Mersoi basin of northern Niger in a 5000-km-wide corridor between Gondwana and Laurasia approximately 15 degrees south of the paleoequator. Late Permian paleoclimate models position this basin between tropical summer-wet to the north and desert to the south. Recent investigations of the fossil vertebrates and paleosols in the late Permian (Lopingian) Moradi Formation confirm that the climate was warm and hyperarid with highly seasonal monsoonal rainfall. Possibly as a result of these unusual “wet desert” conditions, the tetrapod fauna shows a high degree of endemism. This study tests existing paleoclimate models by providing additional data on sedimentary environments and vertebrate taphonomic processes. The Moradi red bed sequences accumulated in a gently subsiding sag basin to the west of the tectonically active Massif de l'Aïr. Low angle gravelly alluvial fans prograded westward from the massif and at times impinged on a large stable northward flowing meandering channel system. The interchannel mudrock sequences are over-thickened by the accumulation of loessic silts and preserve isolated skull and post crania of amphibians (Nigerpeton and Saharastega) as well as semi-articulated captorhinids (Moradisaurus). Detailed surface mapping of a fossil-rich exposure revealed an anastomosed network of loess-filled distributary channels incised into the floodplain mudrocks. This provided a locus for the accumulation and rapid burial of at least 15 associated skeletons of the pareiasaurian Bunostegos. Semi-permanent ponds are evidenced by patches of fissile red mudstone containing rare bivalves and spiral coprolites. In the distal floodplains away from the main river channels, the combination of a generally high groundwater table, warm mean annual temperatures, and deflation of fines from the floodplain surface promoted the formation of gypsiferous paleosols and end-point playa lakes. Carbonate-rich mud accumulated around the lake margins and provided ideal conditions for the imprinting and preservation of tetrapod trackways.

Geology and taphonomy of the base of the Taquaral Member, Irati Formation (Permian, Paraná Basin), Brazil

AbstractThe taphonomy of Early Permian vertebrates from a sandy facies at the base of the Taquaral Member, Irati Formation, was surveyed in order to acquire data for the interpretation of the sedimentary processes and paleoenvironment of deposition. Six outcrops from the Rio Claro municipality and surrounding areas, from the Brazilian State of São Paulo, were investigated. The vertebrate groups are Chondrichthyes (Xenacanthiformes, Ctenacanthiformes and Petalodontiformes), Osteichthyes (Actinopterygii and Sarcopterygii) and Tetrapodomorpha. They occur as loose teeth, scales, spines and bone remains. The sandy facies is characterized by fining upward deposition. The coarser sandstone immediately above the underlying Tatuí Formation is rich in Chondrichthyes. However, the fine sandstone above, immediately beneath the silty shale facies, is devoid of Chondrichthyes, though Osteichthyes scales, teeth and bones were present. The taphonomy is important for inferring sedimentary processes and then the paleoenvironments. The poor sorting of the sandstone and the presence of fossils that are mostly abraded or worn are indicative of a high energy environment. In contrast, the presence of fossils in a good state of preservation, some without abrasion and breakages are indicative of only limited transport. Differences of fossil spatial density, numbers of specimens and taxa may be explained by the dynamics of deposition, from details of the palaeoenvironment can be obtained.

Vertebrate taphonomy and paleoecology in an Upper Pleistocene tank deposit of Paraíba, Brazil: Taphonomic modes, evidence of temporal and spatial resolutions and paleoecological patterns of the Brazilian Intertropical Region

Curimatãs Paleontological Site (CPS) preserved one of the most iconic fossil assemblages of Late Pleistocene vertebrates of Brazil. Fossils were collected in a tank deposit,a singular type of Quaternary vertebrate-bearing deposit of South America. In this work, a detailed taphonomic study of the tank assemblage of CPS is presented. This analysis also provides taphonomic and paleoecological data obtained through the application of common multivariate techniques and provides estimates of time- and spatial resolution for tank deposits. The results show that, although the CPS assemblage has experienced an array of taphonomic processes, the long-distance transport was the main process controlling the taphonomic pathway of the thanatocoenosis during the biostratinomic phase, and was responsible for the co-occurrence of other processes, such as abrasion, fragmentation and bioclastic sorting. The origin of the taphonomic modes of vertebrates in the tank deposit of CPS may have been controlled by three major taphonomic phenomena: (i) a taphonomic bias towards the large-bodied size; (ii) long time span of transportation towards the final burial environment; and (iii) some degree of reworking. Furthermore, the analysis of these taphonomic modes supports a previous hypothesis: although taphonomic biases affect the origin of tank assemblages, paleoecological patterns can be preserved with considerable fidelity. The time resolution in tank accumulations is of the order of 10- 3 to 104 years and their spatial resolution seems to be from local to regional.

Taphonomy of large marine vertebrates in the Upper Cretaceous (Cenomanian-Turonian) Tropic Shale of southern Utah

Sediments from the Upper Cretaceous (Cenomanian-Turonian) Tropic Shale were deposited along the western margin of the Western Interior Seaway, in present-day southern Utah. Marine vertebrates from this formation include plesiosaurs, mosasaurs, bony fish, sharks, and turtles. They are concentrated in the lower portion of the Tropic Shale, mostly between Bentonites B and D. Study of the taphonomic condition of these vertebrates has contributed to an understanding of how they were preserved as well as a detailed paleoenvironment for the Tropic Shale. Physical factors played the dominant role in their preservation, with robust and durable skeletal elements, such as teeth and vertebrae, being most common within the shale. Isolated bones and teeth are also relatively common within the formation, while complete and nearly complete skeletons are more rare. Biological factors played a less dominant role, with no evidence of epifaunal or infaunal activity preserved with any of the skeletal remains. In addition, scavenging marks (both bite and gnaw marks) are relatively uncommon, typically only being found on more complete specimens. A signature of post-burial alteration can be recognized as low levels of abrasion, weathering, and compression and high levels of fracturing of vertebrate skeletal material. Slightly higher levels of abrasion and weathering occur to the west, closer to the ancient shoreline, suggesting some pre-burial alteration. The preservation of marine vertebrates in the Tropic Shale suggests a low energy marine environment with some weak bottom currents and low levels of benthic oxygen. The substrate ranged from soft and soupy to firm, with moderate sedimentation rates resulting in relatively rapid burial.

Terrestrial vertebrates from the Sarmatian (late Serravallian) of the Central Paratethys – the fossil site of Gratkorn (Styrian Basin, Austria)

The Paratethys Sea represents a huge landlocked water body of western Eurasia, which evolved during the Cenozoic era from open to restricted marine conditions towards brackish and lacustrine basins (Rogl and Steininger 1983). Due to the endemic evolution of Paratethyan biota and the tectonics of the Alpine orogeny, chronostratigraphic correlations and basin evolution are still partly a matter of debate and a subject of intense scientific research. Despite the mainly marine or lacustrine sedimentation (Steininger et al. 1985), fossils of continental biota are not rare in deposits in the Paratethyan realm. Notably, terrestrial vertebrates have been known for a long time (e.g. Eichwald 1835), but well-documented excavations and faunas are rare or absent from many stratigraphic stages and basins. This is especially true for the Sarmatian regional stage when the Paratethys was becoming isolated from the world oceans (Piller et al. 2007). This chronostratigraphic stage is crucial, because the Sarmatian sensu stricto (=Volhynian and early Bessarabian) represents the last period with a uniform marine biofacies in the entire Paratethys, extending from the Styrian Basin in the west to the Lake Aral in the east (Steininger and Wessely 2000). While the deposits cover a huge area, terrestrial biota are still a rarity, and those from the early to late Sarmatian transition (Volhynian–Bessarabian transition) virtually unknown. The discovery of the Gratkorn fossil site due to geologic mapping in 2005 gives a unique opportunity to study continental ecosystems of this specific time horizon (12.2– 12.0 Ma, early to late Sarmatian transition). Systematic palaeontologic excavations starting in 2006 have been carried out in a cooperation between the Universalmuseum Joanneum (Graz), the Ludwig Maximillians Universitat Munchen, and the Eberhard Karls Universitat Tubingen. Besides abundant fossils of plants (leafand carpoflora), molluscs (gastropods and mussels), and arthropods (insects, ostracodes, and crabs), more than 1,500 specimens of vertebrates have so far been excavated. These fossils cover all major groups of vertebrates, namely fishes, amphibians, reptiles, birds, and mammals, rendering Gratkorn a benchmark locality for continental biota from the Sarmatian of the Central Paratethys. This special issue is dedicated to Prof. Dr. Friedrich Franz Steininger on the occasion of his 75th birthday in 2014, and in honour of his noteworthy scientific contributions to chronostratigraphy, palaeogeography, and biofacies of the Paratethys Sea. Twelve publications have been brought together summarising the first nearly 10 years of research at Gratkorn. They deal with the geology of the Gratkorn locality, the vertebrate taphonomy, and selected aspects of vertebrate taxonomy and ecology. Further scientific contributions to Gratkorn, e.g. the macro-flora and the carnivore mammals, are in preparation and will shortly be published in a forthcoming issue of Palaeobiodiversity and Palaeoenvironments. This article is a contribution to the special issue “The Sarmatian vertebrate locality Gratkorn, Styrian Basin.”

Reconstructing a Miocene pitfall trap: Recognition and interpretation of fossiliferous Cenozoic palaeokarst

The middle Miocene cave deposit at AL90 Site in the Riversleigh World Heritage Area of Queensland, Australia, is the largest excavated palaeokarst deposit within the extensive Cenozoic freshwater limestones of the region. Stratigraphic relationships between various lithological components of the cave deposit indicate a dynamic, complex depositional history including dissolution, infill and reworking of cave materials. Euhedral spar, shelf-stone, calcite rafts and desiccation cracks on cave sediments suggest standing water was variably present in the cave environment. The AL90 Local Fauna is moderately diverse comprising at least 20 vertebrate families and 32 species, yet is taphonomically biased towards large marsupial herbivores (families Diprotodontidae, Macropodidae, and Balbaridae) and cave-dwelling hipposiderid bats. Fossil material is generally exceptionally well-preserved with, in many cases, articulated skeletons recovered. The cave entrance appears to have acted as a natural pit-fall trap. The complex (unconformable) depositional structure and lithology, vertebrate taphonomy and faunal composition at AL90 Site are typical of deposits and assemblages formed in the inner environment of the upper vadose zone. In the past, some similar unroofed cave deposits have been interpreted as clastic fluvio-lacustrine sedimentary deposits formed by surface processes. Analysis of characteristic palaeokarst features at AL90 Site has enabled the identification of other less well-preserved, poorly-exposed or relict cave deposits at Riversleigh and has facilitated interpretation of the depositional and palaeoenvironmental history of those deposits. The findings presented here confirm earlier interpretations that specific, highly-fossiliferous early Miocene to early Pliocene fossil deposits at Riversleigh represent relict caves whose roofs and walls are no longer intact.

Tafonomía de Vertebrados Del Cretácico Superior de la Formación Loncoche en Calmu-Co (Mendoza, Argentina): Implicancias Paleoambientales y Paleogeográficas

VERTEBRATE TAPHONOMY OF UPPER CRETACEOUS VERTEBRATES FROM THE LONCOCHE FORMATION IN CALMU-CO (MENDOZA, ARGENTINA): PALEOENVIRONMENTAL AND PALEOGEOGRAPHICAL IMPLICATIONS. This paper presents a taphonomic study of vertebrate fossils from the Loncoche Formation (late Campanian—early Maastrichtian) found in the Calmu-Co area in Mendoza, Argentina. Four environmental stages were recognized in this site, (1) saline lacustrine systems; (2) fluvial systems; (3) deltaic systems; (4) shallow fluvial and lacustrine systems. The vertebrates found in the deltaic environment comprise disarticulated parautochthonous—allochthonous concentrations (taphofacies 1) of fishes (Chondrichthyes, Teleostei, Lepisosteidae and Ceratodontidae), turtles (Chelidae), dinosaurs (Titanosauria) and plesiosaurs (Plesiosauria). The disarticulated and fragmentary feature of these mixed concentrations (terrestrial, freshwater, marine) suggest a mixture of remains from littoral environments and fluvial systems. The above interpretation is based on the taphonomic attributes of these concentrations, which showed a high degree of weathering, abrasion and time-averaging. On the other hand, disarticulated parautochthonous concentrations (taphofacies 2) of dinosaurs were registered in the fluvial environment. These remains showed processes of fragmentation and abrasion due to hydraulic transport. Fossil-diagenetic processes include events of permineralization and cementation of vascular canals and fractures, phenomena of deformation and lithostatic compression. These evidences indicate that the Atlantic marine ingression (Maastrichtian—Paleocene) which covered northern Patagonia, spread until Calmu-Co, in the western Neuquén Basin.

Introduction to Zooarchaeological Method and Theory: a Special Issue Honoring R. Lee Lyman

The Society for American Archaeology presented R. Lee Lyman with the Fryxell award for Interdisciplinary Excellence in Zooarchaeology in 2011. Lyman has produced over 120 journal articles or book chapters, and four single-authored books on the topic, and this issue honors his contributions to zooarchaeological method and theory with six original pieces by his peers. Arguably, his greatest impact has been in the field of vertebrate taphonomy and the development of a means to measure density-mediated bone attrition, but of equal importance was emphasis in the discipline that unit selection, or what one measures, should be linked to a particular research question. Lyman's work has also stressed the importance of making zooarchaeology relevant to modern issues of conservation biology.

Vertebrate taphonomy of the Ischigualasto Formation

ABSTRACT Trends of preservation are established on the basis of 385 fossil occurrences in the Ischigualasto Formation. The distribution and preservational quality of vertebrate fossils are related to sedimentary facies and stratigraphic position and follow trends in basin evolution and paleoclimate. Fossils in the Ischigualasto Formation are mainly concentrated along the margins of the basin. Floodplain deposits preserve ca. 88% of fossils, which range from unidentifiable fragments to articulated skeletons. The remaining fossil occurrences (ca. 12%) come from coarser-grained fluvial channel deposits and exhibit variable preservational quality, including some well-preserved cynodont skulls. Fossils in the basal La Peña Member (ca. 4% of occurrences) are generally highly weathered and disarticulated with hematitic permineralization. The majority of collected specimens (ca. 65% of occurrences) come from the overlying Cancha de Bochas Member and range from isolated bones to articulated skeletons. Calcite, rather than hematite, is the predominant agent of permineralization. The succeeding Valle de la Luna Member (ca. 30% of occurrences) preserves an association between vertebrate fossils and plant remains. Fossil preservation suggests prolonged exposure prior to burial under wetter conditions with superficial and penetrating precipitation of hematite. The uppermost Quebrada de la Sal Member of the Ischigualasto Formation is nearly barren of fossil remains. RESUMEN—Se establecieron las tendencias en la preservación de restos de paleovertebrados a lo largo de la Formación Ischigualasto en base a 385 fósiles. La distribución y la calidad de preservación de los fósiles de vertebrados en esta unidad está relacionada con las facies sedimentarias y la posición estratigráfica de los mismos, variando según la evolución de la cuenca y del paleoclima. Los fósiles en la Formación Ischigualasto están principalmente concentrados en los márgenes de la cuenca. Paleoambientalmente, los depósitos de llanura de inundación preservan alrededor del 88% de los fósiles de la unidad, los cuales van desde fragmentos inidentificables hasta esqueletos articulados. Las restantes ocurrencias de fósiles (alrededor del 12%) provienen de depósitos de canal de grano grueso y también exhiben variables calidades de preservación, incluyendo algunos pequeños cráneos de cinodontes en excelente estado de preservación. Estratigráficamente, los fósiles en el miembro basal La Peña (alrededor del 4% de los hallazgos) están generalmente muy meteorizados, desarticulados y permineralizados con hematita. La mayoría de los especímenes colectados (alrededor del 65% de los hallazgos) provienen del suprayacente Miembro Cancha de Bochas, los cuales van desde huesos aislados hasta esqueletos articulados completos. Estos restos están permineralizados principalmente con calcita en lugar de hematita. En el siguiente, Miembro Valle de la Luna (alrededor del 30% de los hallazgos), se preserva una peculiar asociación de restos fósiles de vertebrados y plantas. La preservación de los fósiles en esta unidad sugiere una prolongada exposición bajo un clima más húmedo, con la consecuente precipitación de abundante hematita en la superficie y en el interior. Por último, en el techo de la Formación Ischigualasto, el Miembro Quebrada de la Sal carece casi completamente de restos fósiles.

Taphonomic processes in terrestrial and marine environments

The focus of this special issue is on the taphonomy of fossil vertebrates, as well as on uniformitarian experimental studies. In a palaeontological sense, taphonomy has the focus on a very long time scale, with different taphonomic filters, that dumps high-frequency signals by causes of death, decomposition, embedding and early diagenesis (Briggs 2010; Efremov 1940; Lyman 2010; Martin 1999). Due to their highly differentiated anatomical bauplan, vertebrates are subject to complex mechanisms of decomposition which are linked with each other in manifold ways. Therefore, it must be the intention of taphonomical studies to differentiate basic mechanisms of decomposition and comprehend their sequence as well as their interactions with the deposition environment. The first key to understanding the taphonomy of vertebrates is therefore to reconstruct the context in which burial data are created (e.g. Roksandic 2002). Apart from climatic factors (e.g. temperature of environment), which, not least of all, also control the sedimentation regime, it is essential to the potential of fossilisation of organic remains whether the decomposition, as well as the bedding of a carcass, took place in a subaerial or subaquatic environment. However, the habitat, the place of dying, as well as the environment of the decomposition and bedding of vertebrates are rarely identical. Therefore, it is absolutely necessary for reconstructing the taphonomic history of vertebrates to make a conscientious documentation of the geological and palaeontological context. Last but not least, a critical evaluation of possible scenarios of the cause of death and the processes of decomposition and bedding, as well as their attendant circumstances, makes it possible to draw valuable conclusions concerning the environment of present and past habitats. Taphonomic aspects therefore have an explosive nature as far as economy and environmental politics are concerned, which has already been given attention at the time of the beginning of uniformitarian research (e.g. Wasmund 1935, 48 p.; Wiman 1914). In connection with this, an observation note of Monnett and Gleason (2006) about four dead polar bears floating in openwater of the Arctic Ocean in 2004 recently became a rallying point for campaigners seeking to blunt the impact of global warming (e.g. Morell 2011; Reardon 2011; Reich 2011). A second key to the reconstruction of the taphonomic fate of fossil vertebrates is their quality and quantity in the fossil record. A multitude of intrinsic and extrinsic factors which influenced a carcass up to its complete and final bedding can be deducted from the completeness, the degree of disarticulation and from the relative position as well as from the grade of scattering and modifications of the vertebrates’ skeletal elements (e.g. Lyman 1994). Uniformitarian experiments on the decomposition of vertebrates which give evidence of the timeline of decomposition and the hardiness of different tissues against decay may furnish suitable clues here. In our view, just in the research of the taphonomy of fossil vertebrates, too little attention has been given so far to the complex interactions between the anatomy of soft tissue and skeleton of a carcass. Vertebrates have certain taphonomic predispositions because of their specific bauplan, their This article is a contribution to the special issue “Taphonomic processes in terrestrial and marine environments”.