Taphonomic Modifications Research Articles

Metamorphism obscures primary taphonomic pathways in the early Cambrian Sirius Passet Lagerstätte, North Greenland

Abstract Correct interpretation of soft-bodied fossils relies on a thorough understanding of their taphonomy. While the focus has often been on the primary roles of decay and early diagenesis, the impacts of deeper burial and metamorphism on fossil preservation are less well understood. We document a sequence of late-stage mineral replacements in panarthropod fossils from the Sirius Passet Lagerstätte (North Greenland), an important early Cambrian Burgess Shale–type (BST) biota. Muscle and gut diverticula were initially stabilized by early diagenetic apatite, prior to being pervasively replaced by quartz and then subordinate chlorite, muscovite, and chloritoid during very low- to low-grade metamorphism. Each new mineral replicates the soft tissues with different precision and occurs in particular anatomical regions, imposing strong biases on the biological information retained. Muscovite and chloritoid largely obliterate the tissues’ original detail, suggesting that aluminum-rich protoliths may have least potential for conserving mineralized soft tissues in metamorphism. Overall, the fossils exhibit a marked shift toward mineralogical equilibration with the matrix, obscuring primary taphonomic modes. Sequential replacement of the phosphatized soft tissues released phosphorus to form new accessory monazite (and apatite and xenotime), whose presence in other BST biotas might signal the prior, more widespread, occurrence of this primary mode of preservation. Our results provide critical context for interpreting the Sirius Passet biota and for identifying late-stage overprints in other biotas.

Exceptionally preserved hyolithids from the middle Cambrian of North China

AbstractHyoliths are extinct enigmatic organisms of early lophotrochozoan affinity known globally from the Palaeozoic Era and were especially diverse and abundant in the Cambrian Period. However, the commonly incomplete preservation of hyolith exoskeletons and our limited knowledge of their soft anatomy makes their ecological and biological aspects unclear. Konservat-Lagerstätte are crucial windows to unlock the mysteries of hyoliths. Here we report a new occurrence of exceptionally preserved hyolithid hyoliths from the middle Cambrian Mantou Formation (Miaolingian, Wuliuan) in Shandong Province, North China. The preserved soft organs of the new species Novakotheca weifangensis sp. nov. include a U-shaped gut and possible pharynx, oesophagus, stomach and digestive gland, which provide significant new information for the reconstruction of the digestive system of hyolithids. Two taphonomic modes of hyoliths described herein are recognized: soft tissue preservation through pyritization and three-dimensional shell preservation through phosphatization. Morphological variations due to different preservational pathways in the same species are revealed, highlighting the taphonomic bias on taxonomy. The ecological association between hyoliths and small brachiopod epibionts is a direct example of species interactions, providing insights into the ecological structures and adaptability of early animals during Cambrian time.

Muknalia is a Collared Peccary (Pecari tajacu): A Reply to Stinnesbeck et al.

Several years ago, a new genus and species of peccary, “<em>Muknalia minima</em>”, was described from the Pleistocene of Mexico. We previously examined that specimen and concluded that it was synonymous with the extant collared peccary, <em>Pecari tajacu</em>, but that taxonomic revision is rejected by the authors of the original study (this volume). Here, we provide further analysis of “<em>Muknalia</em>” and expand on previous evidence from both morphology and taphonomy that support synonymy with <em>P. tajacu</em>. We argue that morphological features, both in terms of size and shape, that were used to diagnose “<em>Muknalia</em>” all fall within the range of variation of the extant <em>P. tajacu</em>, or are a consequence of taphonomic modification, including human handling.

The influence of volcanic activity and trophic state on plant taphonomic processes in Triassic lacustrine-deltaic systems of western Gondwana

The impact of volcanic activity and trophic state on the preservation of plant remains from two Triassic palaeolake deposits in western Gondwana is investigated. Six taphonomic modes are identified for the Potrerillos–Cacheuta sequence and the Los Rastros Formation, along with proposed taphonomic pathways for each mode. The taphonomic pathways were compared with those proposed for the Agua de la Zorra Formation, a coeval lacustrine-deltaic succession. In all three cases, plant preservation in off-shore lacustrine facies was enhanced by anoxic bottom conditions. In the more proximal near-shore facies, a high sedimentation rate would have been factor that enhanced the preservation. Variation in relative abundance and taxonomic diversity between the three successions are attributed to ecological differences rather than taphonomic differences among the lake systems. No evidence was recorded that the preserved plant material was produced by volcanic trauma. The preservation of the cuticle recorded in the Cacheuta Formation was likely enhanced by the apparently low thermal maturation of the rock and the presence of tuffaceous horizons. In the three successions, the abundance and distribution of remains throughout the sections suggest that the trophic state of the lake did not influence the preservation of the plant.

More on the identification of fish bones from southeast Arabia

AbstractIdentification of fish bones from archeological sites in southeast Arabia requires access to an extensive reference collection. This is often not possible, and repeated use of these resources when they are available ultimately damages bones. This paper provides a platform from which high‐resolution images of 60 species of marine fishes from southeast Arabia can be downloaded, aiding identification and providing illustrations that other researchers can modify to produce graphics to highlight taphonomic modification to bones or illustrate measurements taken.

Neurocranial abnormalities in the Middle Pleistocene Homo erectus fossils from Hexian, China

AbstractThe Middle Pleistocene Homo erectus cranium from Hexian (Hexian 1, PA 830), in central eastern China, has been studied fairly extensively with respect to its evolutionary position. However, analysis of a series of neurocranial abnormalities identified on the Hexian fossil has never been attempted. Here, we present the first study of these abnormalities identified on the Hexian cranium, including (1) multiple breakages (including cracking) that fracture radially across the whole vault, caused by taphonomic modifications; (2) postmortem erosional lacunae with a matrix layer on the external surface of the supraorbital torus; (3) and two healed lesions with resorption and new bone formation on the back of the head, likely the result of trauma (tensile trauma to the scalp or partial scalp removal) or burning (with damage to the scalp and superficial neurocranium). The Hexian 1 individual was a young adult and had experienced multiple neurocranial alterations of antemortem traumatic lesions and postmortem taphonomic damage. The Hexian 1 specimen adds to the growing list of examples of bone surface modifications on Pleistocene hominin fossils across the Old World—a list that documents clearly the high level of risk experienced by Middle Pleistocene hominins.

An Early Triassic small shelly fossil-style assemblage from the Virgin Limestone Member, Moenkopi Formation, western United States

Small shelly fossils (SSFs) are minute fossils moulded or replaced by apatite, and less commonly, other minerals like glauconite and iron oxides. This taphonomic mode is best known from Cambrian deposits, though some occurrences occur across geological time. Instances of small shelly-style preservation were found in insoluble residues from the Lower Triassic Virgin Limestone Member exposed in southern Nevada, the western United States, a second such occurrence known from this unit. Fossil steinkerns of tiny brachiopods, echinoid spines and ophiuroids are fluorapatite, with scarce phosphatic internal moulds of bivalves and two replaced ostracods. In contrast, the crinoid ossicles, almost all of which are >1000 µm, are preserved as stereomic moulds of silica or dolomite. Though the style of preservation is similar to another Virgin Limestone small shelly fossils-style assemblage, this assemblage preserves greater diversity, likely reflecting the variation in palaeocommunities across the shelf. The size selectivity of phosphatization is clear, as the majority of the fossils <1000 µm are phosphatized. Importantly, the original skeletal material does not exert the strongest control on style of preservation: crinoid ossicles are replaced or moulded by silica whilst ophiuroid and echinoid fragments are phosphatized. It is likely that the underlying phosphatization mechanisms are related to the small particle size of the skeletons or skeletal elements coupled with the local pore water environment. Early Triassic equatorial seas characterized by warm temperatures and lower oxygen levels likely fostered small shelly fossil-style preservation across the shelf during this time.

Soft part preservation in hyolithids from the lower Cambrian (Stage 4) Guanshan Biota of South China and its implications

Hyoliths, known globally from the Cambrian to the Permian are generally recognized as early lophotrochozoan animals of uncertain phylogenetic position. The calcareous exoskeleton of hyolithids, one of the two subgroups of hyoliths, consist of four elements including a conical conch, an external operculum, and a pair of curved enigmatic helens, but their ecology and internal morphology have long been considered controversial. Here we present for the first time, remarkably preserved hyolithids with helens and interior soft tissues from the Guanshan Biota (Cambrian, Stage 4) of Shijiangjun section, Wuding County in eastern Yunnan Province of South China. Preserved soft tissues and organs encompass the digestive tract, muscle scars and connective tissues between the operculum and conch. Three modes of soft part preservation in hyolithids from the Guanshan Biota are described: (1) preservation through pyritization, (2) sediment-infilling of guts, and (3) bacterial biofilm pseudomorphs (expressed as large internal hollow cavities), resulting from endogenous bacterial decay of soft parts. Such differential preservation of hyolith guts indicates different taphonomic modes for the soft parts of Cambrian animals in the Guanshan Biota. The newly collected material yields the oldest preserved guts in hyolithids from Konservat-biotas, and reveals new evidence for reconstructing hyolithid anatomy, such as the articulation mechanism of the opercula and the internal structures in the conch. Comparisons with younger well-preserved hyolithid specimens indicate that the gut anatomy of hyolithids was evolutionarily conservative from the early Cambrian through to at least the Ordovician.

Exploring the potential of TEM analysis for understanding cooking at prehistoric feasting sites

This study explores the utility of transmission electron microscopy (TEM) analysis of bone collagen for investigating prehistoric cooking. Approaches to cooking practices have relied principally on artefactual evidence, macroscopic bone modification, and organic residue analysis. However, direct evidence for cooking of bone has been limited. Richter and Koon successfully applied TEM analysis of collagen to determine heating to modern and medieval bones, but this method has yet to be experimentally tested using prehistoric remains. Collagen will denature at relatively low temperatures, such as during roasting, boiling, or baking. The denaturation of collagen causes predictable structural changes that can be viewed through TEM. Zooarchaeological remains of sheep and pig with minimal taphonomic modifications were analysed from four later prehistoric (c. 800–500BC) sites in Britain (n = 33). Humeri and phalanges were selected to compare elements with high and low meat yields. Samples were classified into ‘Heated’ and ‘Unheated’ groups consistent with previous studies, and variable patterns were observed between different sites and taxa. Analytical limitations have hindered the study of cooking in the past, but this study demonstrates the potential of this taphonomic method for exploring prehistoric cooking practices and provides a springboard for wider studies.

The human remains from the Lumentxa cave (Lekeitio, Biscay, Northern Iberian Peninsula): Paleobiology, Taphonomy and Chronology

Lumentxa is a classic site in Basque Prehistory, excavated in three different phases during the 20th century, which has yielded evidence of both Pleistocene and Holocene occupations. In this article, we present a detailed study of the human remains from this site including paleobiological, taphonomic, biomechanical and chronological perspectives. The human assemblage comprises of a minimum number of seven individuals: three subadult and four adults, with both sexes represented, although part of the human collection is currently lost. We have obtained C14 dates from 4 of these 7 individuals indicating a prolonged funerary use of the cave from the Early Neolithic until the Bronze Age. We observed some biases in the skeletal representation which could be due to differences in the excavation methods between field seasons and/or the action of carnivores, the latter being evident in at least three of the individuals. The taphonomic modifications are typical off those found in the post-abandonment phases in cave funerary contexts. The relatively low number of individuals compared with other sites in the region and extended timespan over which the remains were deposited suggest that the cave was used only sporadically for funerary purposes. We report the first biomechanical data for a Neolithic individual from the Iberian Peninsula, which show greatest overall similarity to the Neolithic sample from France and Italy. Finally, the broad time period covered by the direct dates and the more complex taphonomic history than was previously assumed for such sites indicate that caution is warranted when assigning sepulchral caves to cultural periods in the Western Pyrenees when no direct radiocarbon dates have been obtained.

Disentangling biological variability and taphonomy: shape analysis of the limb long bones of the sauropodomorph dinosaur Plateosaurus.

Sauropodomorph dinosaurs constitute a well-studied clade of dinosaurs, notably because of the acquisition of gigantism within this group. The genus Plateosaurus is one of the best-known sauropodomorphs, with numerous remains from various localities. Its tumultuous taxonomic history suggests the relevance of addressing its intrageneric shape variability, mixed with taphonomic modifications of the original bone shape. Here we investigate quantitatively the morphological variation of Plateosaurus occurring at the genus level by studying the shape variation of a sample of limb long bones. By means of 3D geometric morphometrics, the analysis of the uncorrelated variation permits separation of the variation estimated as obviously taphonomically influenced from the more biologically plausible variation. Beyond the dominant taphonomic signal, our approach permits interpretation of the most biologically plausible features, even on anatomical parts influenced by taphonomic deformations. Those features are thus found on a quantitative basis from the variation of samples containing fossil specimens, by taking the impact of taphonomy into account, which is paramount in order to avoid making biologically ambiguous interpretations.

Preservation of latest Cretaceous (Maastrichtian)-Paleocene frogs (Eorubeta nevadensis) of the Sheep Pass Formation of east-central Nevada and implications for paleogeography of the Nevadaplano.

Here we report on exceptional preservation of remains of the frog Eorubeta nevadensis in deposits of the Sheep Pass Formation, ranging from Late Cretaceous to Eocene, in the south Egan Range, Nevada. This formation represents a lacustrine basin within the Sevier retroarc hinterland. The formation is subdivided into six members (A–F); of interest here are members B and C. The base of member B is ?uppermost Cretaceous-Paleocene, while member C is Paleocene. Member B frogs are preserved in three taphonomic modes. Mode 1 frogs are nearly complete and accumulated under attritional processes, with frogs settling on microbial mats, as evidenced by crenulated fabric of entombing limestone. Mode 2 involves accumulation of frogs as a result of attritional processes. These frogs are mostly complete with some showing evidence of invertebrate scavenging. Possible scavengers are gastropods, ostracods, and decapods. Mode 3 is represented by isolated, reworked remains of frogs as a result of storm activity, supported by the association of elements with disarticulated bivalves and mud rip-up clasts. Member C preserves frogs in two taphonomic modes. Mode 4 are nearly complete frogs that accumulated during discrete mass mortality events. Numerous individuals are preserved along bedding planes in identical preservational states. Mode 5 is beds of frog bone hash, which represent increased energy to the depositional system (likely tempestites) and reworking of previously buried frog remains. Taphonomy of the frogs, along with the associated fauna and flora, are consistent with preservation in a cool, temperate lake basin, supporting previous interpretations that the Nevadaplano was an elevated plateau during the late Cretaceous through the Eocene. This is a period of time coincident with a climatic thermal optimum, thus the most parsimonious explanation for a temperate lake at the latitude of east-central Nevada is to invoke high elevation, which is consistent with independent structural and clumped stable isotope studies.

PLANT TAPHONOMY IN A LAKE AFFECTED BY VOLCANISM (AGUA DE LA ZORRA FORMATION, UPPER TRIASSIC) MENDOZA, ARGENTINA

ABSTRACTVolcanic eruptions have an impact on the paleoecology of plant communities and their preservation in the fossil record. The aim of this contribution is to evaluate the influence of volcanism on plant preservation in lacustrine settings via systematic sampling and chemical analyses of fossil plants in the Upper Triassic Agua de la Zorra Formation, of the Argentinian Cuyana Basin. Plant remains are not uniformly preserved throughout the Agua de la Zorra Formation and their stratigraphic distribution reflects the original spatial pattern of the plant communities. SEM-EDX analyses was used to demonstrate how volcanism affected diagenesis of the plant remains. Eight taphonomic modes were determined from biostratinomic analysis, and three preservational modes from the chemical features observed in the SEM-EDX spectra. The three preservation modes recognized by SEM-EDX analysis are more likely linked to diagenesis and are not equivalent to the taphonomic modes described based on the biostratinomic features. The Agua de la Zorra paleolake preferentially preserved plant material because of anoxic conditions in deeper parts of the lake, and a high sedimentation rate in proximal near-shore facies. The plant remains are most abundant in sandy facies deposited by high-energy flows but there is no evidence that these flows were pyroclastic nor that the plant remains were generated by volcanic trauma.

New insights on the quaternary fossil record of Isla de la Juventud, Cuba

The fossil record of Isla de la Juventud, the second largest island in the Cuban archipelago, is very limited in the number of taxa and localities so far studied but can be key to further understand the biogeographical history and extinction of the fauna in the region. Here, we report the faunal assemblages of two recently discovered Quaternary deposits containing numerous vertebrates and land snails in northern Isla de la Juventud. The first locality, a marble breccia on the coast of Punta Bibijagua, contained remains of an extinct rodent and a sloth. The second locality, a dissolution fissure filled with fossil-bearing sediment in a marble quarry in Sierra de Casas, contained a rich assemblage of land snails and vertebrates. Nineteen species, 14 genera and nine families of gastropods were identified, of which 11 species and two genera are endemic. The snail fossil assemblage is similar to the community of living gastropods in the locality. Moreover, 12 taxa, four of them extinct, 11 genera from ten families of terrestrial vertebrates were recognized; including the first report of fossils frogs, toads, lizards, snakes, and tortoises from Isla de la Juventud. Because remains at Sierra de Casas were collected ex-situ, any possible stratigraphic relationship among them was lost, but we were able to determine the presence of at least two taphonomic modes that suggest different depositional histories. Furthermore, we found no evidence of extinction or extirpation among land snails in the region, but of the vertebrates’ assemblage two rodents, two sloths and a tortoise went extinct. These five taxa also disappeared in the mainland, suggesting that the extinction was in some cases taxonomic specific across the Cuban Archipelago.

An integrative physical, mineralogical and ichnological approach to characterize underfilled lake‐basins

AbstractLakes are particularly sensitive to environmental fluctuations, which are recorded in their facies and stratigraphy. Ephemeral lakes reveal their sensitivity to palaeoenvironmental changes in the overprinting of the sedimentary features in every single bed. Tetrapod‐track taphonomic‐modes and ichnological taphonomic‐pathways can be used as sensitive indicators of environmental conditions of the track‐bearing beds during deposition and imprinting. The Middle Triassic Cerro de las Cabras succession (Cuyana Basin, Argentina) provides an excellent opportunity to these environmental indicators in an underfilled palaeolake. A model of ichnological preservation for underfilled lake systems is proposed and the role of the ichnology record in the sequence stratigraphy analysis is evaluated, based on the integration of tetrapod‐track modes, taphonomic‐pathways of playa‐lake ichnofauna, mineralogy and physical data. Soft‐ground suites include those dominated by invertebrate grazing traces and arthropod locomotion traces (Suite 1), and those overprinted by horizontal‐vertical dwelling burrows with tetrapod tracks preserved in taphonomic modes B and C (Suite 2). The firm‐ground suite (Suite 3) comprises tetrapod‐tracks with the best preservation styles (modes A and B) along less abundant invertebrate dwelling and feeding traces as found in Suite 2. Clay mineralogy (dominated by illite with subordinate smectite) suggests low plasticity of the layers, in agreement with low‐relief deformation structures observed in tetrapod‐track taphonomic‐modes. The well‐preserved track tetrapod features documented in the Cerro de las Cabras succession, together with the absence of pedogenic disturbance, trampling obliterating the footprints, and/or evidence of strong disturbance by wind, desiccation and/or precipitation, supports short periods of exposure of the imprinted surface particular to this succession. An integrated multiproxy approach is proposed to evaluate the evolutionary interpretation and identification of autogenic versus allogenic controls in underfilled lake‐basin histories. The observed aggradational‐trend suggests an equilibrium between rates of accommodation change and sediment supply, and that the basin‐centre did not experience prolonged sediment‐starved conditions.

The Middle Pleistocene hominin mandible from Payre (Ardèche, France)

Although Neandertals are the best-known fossil hominins, the tempo and evolutionary processes in their lineage are strongly debated. This is in part due to the scarcity of the fossil record, in particular before the marine isotopic stage (MIS) 5. In 2010, a partial hominin mandible was discovered at the Middle Paleolithic site of Payre (France) in a layer that is dated to the end of MIS 8/beginning of MIS 7, a time period for which very few fossils are known in Europe. The Payre 15 mandible retains the complete symphyseal region and right lateral corpus with heavily worn P4, M1, and M2 in situ. Taphonomic modifications in the form of three notches suggest that this individual was chewed by a carnivore. We provide here the first detailed description of this specimen and a comparative analysis that includes morphological features, linear mandibular dimensions, an elliptic Fourier analysis of the symphysis, and a morphometric analysis of the M1 roots (based on segmented CT scan data). Our comparative sample encompasses European Middle and Upper Pleistocene specimens attributed to Homo heidelbergensis and Homo neanderthalensis, Upper Pleistocene Homo sapiens, and Holocene Homo sapiens. The Payre 15 mandible shows a combination of primitive and Neandertal-like features, with a receding symphyseal profile without any element of the mentum osseum, a posterior location of the mental foramen and lateral prominence. Its mandibular body is tall and thick anteriorly. Payre 15 has mesotaurodont M1 roots and a three-rooted M2. By its dimensions and combination of features, Payre 15 aligns better with Middle Pleistocene European hominins than with MIS 6–3 Neandertals. Noteworthy, it falls well within the range of variation of the Sima de los Huesos sample. Our results underscore that the total pattern of Neandertal-derived morphology was not achieved at the beginning of the MIS 7 and suggest a low level of mandibular diachronic changes for the period MIS 11–7.

Late Holocene coastal land-use, site formation and site survival: Insights from five middens at Cape Leveque and Lombadina, Dampier Peninsula, Kimberley, Australia

This paper introduces primary data on site contents, chronology and stratigraphy for four subsurface middens, which formed through the late Holocene on the Dampier Peninsula. Data from one surface midden collection are also presented. In this monsoonal coastal locality, variations in dune stability and sand flux are critical to archaeological site formation and preservation. Site specific factors determining sand sequestration into topsoils interact with geomorphological processes and past human discard to determine the stratigraphy and chronology of individual sites. Taphonomic modes during the Anthropocene have shifted, such that middens are rapidly transformed by wind when exposed in back-beach areas. Processes of sand sequestration present management issues at midden sites, and their chances of survival into the future. The cultural assemblages from the middens are also discussed, with reference to the rich ethnoarchaeology of Bardi land-use and subsistence.

A Late Pleistocene fossil stork (Ciconiiformes: Ciconiidae) from the Santa Vitória Formation, Southern Brazil and its paleoenvironmental significance

The avian fossil record of southern Brazil is scarce, consisting of few isolated remains. Here is described a ciconiid fossil from the assemblage of mammalian remains of the Santa Vitoria Formation (SVF). The specimen is a cervical vertebra morphologically similar to Ciconia maguari (maguari stork), common in southern Brazil today. Nevertheless, its larger dimensions suggest that it could be either a morphotype of that species or another, extinct species. The taphonomic modifications of the vertebra result of a combination of autogenic and allogenic factors including the aquatic habit, shape and transportation by flowing water and burial in a shallow stream. The fossil-bearing sediment dated by luminescence was deposited during the late Pleistocene, at 37.9 ka b2k, and exhibits physical features indicating deposition under variable discharge and seasonal oscillations of the water table. The presence of an aquatic bird in these sediments indicates a period of increased precipitation, chronocorrelated to one of the millenial-scale warming pulses recorded in ice cores from Antarctica (Antarctic Isotope Maxima) that characterized the interstadial MIS 3. On the other hand, the dry and cold climate of the following glacial MIS 2 may have forced ciconiids and aquatic mammals to retreat to suitable areas (refugia), as indicated by their absence in the loess deposits (Cordao Formation) overlying the SVF, until returning during the Holocene when climate became wet and warm again. The results presented here increase the avian fossil record of southern Brazil and help understand the role of climate change on the distribution of ciconiid birds and other taxa during the Quaternary in southern South America.

Sesgo tafonómico en los datos de distribución de Cloudina en Siberia

En Siberia los morfotipos de Cloudina han sido tradicionalmente considerados como una variedad tafonómica de conchas de Anabarites, insertadas una dentro de otra, bajo condiciones hidrodinámicas específicas. Las asociaciones de conchas cónicas telescópicas son omnipresentes en el Grupode Kessyusa y en estratos contemporáneos a lo largo de Siberia, y no todos ellos pueden ser fácilmente interpretados como resultado de un simple apilamiento mecánico. Queda por ver si alguna de estas bioacumulaciones representa una asociación de vida de una estructura morfotípica de tipo Cloudina.

Differentiating trauma from taphonomic alterations

Differentiating traumatic injuries in bone from taphonomic damage in the postmortem period is a complex process requiring a systematic approach. Trauma by definition occurs while the individual is still living, but bone characteristics usually do not allow delineation of the moment of death. Thus, the anthropologist seeks characteristics that will associate a skeletal defect with the perimortem period, at or about the time of death. However, the anthropological designation of perimortem time period does not have precise boundaries. It refers to remains that lack any sign of remodeling or healing on the one hand, and which have not lost biomechanical elasticity and plasticity on the other hand, i.e., it refers to the condition of skeletal remains when they sustained the suspected injury. Fracture patterns that reflect biomechanical plasticity are lost gradually as the time since death increases, and this pace will depend on the environmental context. There are additional clues to identify postmortem status, including when the damaged feature fits a taphonomic pattern of scavenger modification or weathering, or physically overlies obvious postmortem modifications, or when the feature fits a known pattern of sharp force instruments or weapons. Damage due to recovery or the examination process must be ruled out. The timing of occurrence of a suspected perimortem injury can therefore extend for days or weeks into the time before the actual death, and it can extend for days to months after death. The anthropologist responds to the challenge of differentiating trauma and taphonomic modification by knowing the characteristics of healing bone, the features of biomechanical plasticity reflected in fracture morphology, the taphonomic patterns of scavenging and weathering, the environmental context of discovery and recovery, and the characteristics of the relevant regional taphonomy.