Fossil Bones Research Articles

Mammoth Fauna Remains From Late Pleistocene Deposits of the Dmitry Laptev Strait South Coast (Northern Yakutia, Russia)

The Yedoma Ice Complex in northern Yakutia provides perfect preservation conditions for frozen remains of vertebrate animals. Even complete mummified specimens of the late Pleistocene Beringian Mammoth fauna such as woolly mammoth, woolly rhinoceros, horse, and bison are occasionally found in permafrost deposits across eastern Siberia, i.e., in West Beringia, although bones are much more commonly found. The present study characterizes mammal bones from late Pleistocene and Holocene permafrost deposits exposed on the Oyogos Yar coast, part of the southern shore of the Dmitry Laptev Strait that connects the Laptev and East Siberian seas. The study applies a method to characterize fossil bone samples by the location of their discovery and by the accuracy of their relation to a depositional horizon. We analyzed a total of 38 finite radiocarbon ages of bone material from mammoth, horse, and musk ox, spanning from about 48.8 to 4.5 ka BP and including both our own data and data from the literature, in addition to previous publications that reported numerous bones with infinite ages from the Oyogos Yar coast. The distribution of bones and tooth along the coastal permafrost exposure is not uniform; it depends upon whether the material was found in situ, on thermo-terraces, or on the shore. The overall bone collection consists of 13 species of which Mammuthus primigenius (woolly mammoth, 41%), Bison priscus (bison, 19%), Equus ex gr., caballus (horse, 19%), and Rangifer tarandus (reindeer, 16%) predominate. The fossil bone species distribution is similar to those of other prominent Yedoma outcrops in the region, i.e., on Bykovsky Peninsula and on Bol’shoy Lyakhovsky Island. Correlation analysis shows that the Oyogos Yar bone sampling sites of different geomorphological settings are similar to each other but not to all sampling sites within the other two locations on Bykovsky Peninsula and on Bol’shoy Lykahovsky Island. High similarities in terms of correlation coefficients between specific sampling sites are often not represented in the cluster analysis.

A 16S rRNA Gene-Based Metabarcoding of Phosphate-Rich Deposits in Muierilor Cave, South-Western Carpathians.

Muierilor Cave is one of Romania’s most important show caves, with paleontological and archeological deposits. Recently, a new chamber was discovered in the cave, with unique yellow calcite crystals, fine-grained crusts, and black sediments. The deposits in this chamber were related to a leaking process from the upper level that contains fossil bones and a large pile of guano. Samples were taken from the new chamber and another passage to investigate the relationship between the substrate and microbial community. Chemical, mineralogical, and whole community 16S rRNA gene-based metabarcoding analyses were undertaken, and the base of the guano deposit was radiocarbon dated. Our study indicated bacteria linked to the presence of high phosphate concentration, most likely due to the nature of the substrate (hydroxyapatite). Bacteria involved in Fe, Mn, or N cycles were also found, as these elements are commonly identified in high concentrations in guano. Since no bat colonies or fossil bones were present in the new chamber, a high concentration of these elements could be sourced by organic deposits inside the cave (guano and fossil bones) even after hundreds of years of their deposition and in areas far from both deposits. Metabarcoding of the analyzed samples found that ∼0.7% of the identified bacteria are unknown to science, and ∼47% were not previously reported in caves or guano. Moreover, most of the identified human-related bacteria were not reported in caves or guano before, and some are known for their pathogenic potential. Therefore, continuous monitoring of air and floor microbiology should be considered in show caves with organic deposits containing bacteria that can threaten human health. The high number of unidentified taxa in a small sector of Muierilor Cave indicates the limited knowledge of the bacterial diversity in caves that can have potential applications in human health and biotechnology.

A ‘large and valuable’ Siwalik fossil collection in the archives of the Oxford University Museum of Natural History

ABSTRACT This article describes results from a review of South Asian fossils in the Oxford University Museum of Natural History. These materials include two early 19th century collections of fossils from the Siwalik Hills in India. While this assemblage was summarised in 1837 by William Buckland as ‘large and valuable collections of fossil bones’, it has remained largely unstudied and unpublished in any detail since collection. Here, as a precursor to a comprehensive re-evaluation, we establish a chronological and geographical context of one collection event, provide details of its donor, and outline its history after arrival in Oxford. We then describe select taxa in the collection, including a well-preserved maxilla and toothrow of the large extinct giraffid, Sivatherium giganteum, as a basis to justify our current understanding of the biostratigraphic affinity of the assemblage. Conservatively, the collection is a ‘classic’ Upper Siwalik Plio-Pleistocene fauna, possibly the first to be transported to the UK. While further analyses will realise the scientific potential of the fossils, the narrative of their journey from India to Oxford remains incomplete. Further investigation of the hidden history of the collection is warranted.

Feeding habits of the Middle Triassic pseudosuchian Batrachotomus kupferzellensis from Germany and palaeoecological implications for archosaurs

AbstractBite traces on fossil bones are key to deciphering feeding ecology and trophic interactions of vertebrate past ecosystems. However, similarities between traces produced by different carnivorous taxa with similar dentitions, and misidentifications due to equifinality, hinder confident identifications of the bite makers. Here, we correlate bite traces with macroscopic wear and microanatomy of the teeth of the pseudosuchian archosaur Batrachotomus kupferzellensis from the Triassic Lower Keuper fossil lagerstätten (southern Germany), untangling its feeding habits and shedding light on the bite traces generated by ziphodont teeth (teeth with serrated carinae). Individually, bite traces reflect tooth morphology, whereas composite bite traces and their frequency are related to feeding behaviour and explain tooth macroscopic wear and microanatomy. Therefore the identification of the bite maker is possible by analysing composite bite traces, their location on bones, and their relative abundance. In addition, tooth macroscopic wear and microanatomy are proven as independent lines of evidence of feeding ecology. Comparing bite traces on fossil and present‐day bone assemblages, we observe that bone modifications by the crocodylomorph lineage (from Triassic pseudosuchian archosaurs to extinct and extant crocodylians) are strikingly similar, including taxa with and without ziphodont teeth. Such a set of features differs from bone modification assemblages produced by taxa with similar ziphodont teeth outside the pseudosuchian lineage, such as theropod dinosaurs and the Komodo monitor, suggesting phylogeny is a better predictor of feeding ecology among saurian reptiles than tooth morphology.

FOSSIL BONES FROM THE NORTH SEA: RADIOCARBON AND STABLE ISOTOPE (13C/15N) DATA

ABSTRACTThe North Sea is considered a unique heritage site that yielded a huge amount of zoological and archaeological data. More than 200 palaeozoological and archaeological fossil bone samples from the North Sea bed are dated by 14C. About 2/3 of these dated bones are Pleistocene in age; the majority of the bones are from extinct species (in particular woolly mammoth); about 1/3 of the sample date to the Holocene. The presented dataset is important in its kind, but interpretation is limited because of a lack of context of the finds. The stable isotopes (13C, 15N) of the dated samples provide additional information on palaeoenvironmental conditions and dietary habits in the past. We present primarily a Groningen list of data; a few fossils dated in other laboratories are included for completeness.

Effect of yeast culture supplementation on blood characteristics, body development, intestinal morphology, and enzyme activities in geese.

The objective of this experiment is to evaluatethe effects of yeast culture (YC) supplementation on blood characteristics, body size, carcass characteristics, organ weights, intestinal morphology, and enzyme activities. Five groups of geese were randomly assigned to five dietary treatments: the basal diet (control) and basal diets plus 0.5%, 1.0%, 2.0%, or 4.0% YC. Compared with the controls, YC supplementation at 0.5% and 1.0% increased the serum total protein (TP), albumin (ALB), and globulin (GLO) and decreased the uric acidand creatine kinase (CK) contents (p < 0.05). YC supplementation at 2.0% and 4.0% increased the CK, growth hormone, catalase and glutathione reductase contents, and relative proventriculus weights, and decreased the TP, ALB, and GLO contents, relative liver, gizzard, jejunum, ileum, and thymus weights (p < 0.05). YC supplementation at 2.0% improved fossil bone length, breast muscle percentage, jejunal villus height, ileal and jejunal villus height/crypt depth ratios, pepsin, lipase, amylase and pancreatic trypsin activities, and decreased abdominal fat percentage (p < 0.05). Furthermore, YC inclusion increased the body slope length (linear, p = 0.002; quadratic, p = 0.02), breast width (quadratic, p = 0.02), ileal (linear, p = 0.04; quadratic, p = 0.01) and duodenal villus height (cubic, p = 0.04), and decreased the relative gizzard (quadratic, p = 0.04) and thymus (linear, p = 0.002; quadratic, p = 0.02; cubic, p = 0.02) weights, liver (linear, p = 0.002; quadratic, p = 0.02), and serum (linear, p = 0.006; quadratic, p = 0.03) malondialdehyde contents, and jejunal crypt depth (quadratic, p = 0.03). The findings indicated that the YC supplementation had a positive effect on the growth and development of geese, with 2% YC being the most effective.

21st Century Rex: maximising access to a privately owned Tyrannosaurus rex skeleton in the digital age

A ~60-70% complete Tyrannosaurus rex skeleton known as Stan recently sold for 31.8 million US dollars to an unknown buyer (announced in March 2022 as the Natural History Museum Abu Dhabi), pushing up the price of all such skeletons way beyond the budget of most museums. Wealthy private individuals who purchase expensive fossil specimens sometimes put them on public display but leave them in an intellectual limbo, unable to be studied and published. However, a partial T. rex skeleton known as Titus was excavated in Montana in 2018, shipped to the UK in 2020, and had casts of Stan's bones added to complete the skeleton during mounting. It was loaned to the Nottingham Natural History Museum, Wollaton Hall, as the centrepiece to a temporary exhibition called Titus: T. rex is King. This was the first time a mounted T. rex skeleton containing fossil bones had been on display in England for many decades. Importantly, before the mounting process began, all the real bones were 3D scanned in detail using photogrammetry. The resulting digital 3D models were sent to palaeontologists in America who studied them and produced a paper describing the palaeopathology before the mounting process was even complete. Replicas of all the identifiable bones were 3D printed for display in the exhibition and were accessioned into the museum collections, along with the 3D digital models and all associated data. This ensured that physical as well as digital replicas of the bones would remain accessible, and in theory publishable, forevermore.

Abdominal contents reveal Cretaceous crocodyliforms ate dinosaurs

Crocodylians are among Earth’s most successful hyper-carnivores, with their crocodyliform ancestors persisting since the Triassic. The diets of extinct crocodyliforms are typically inferred from distinctive bite-marks on fossil bone, which indicate that some species fed on contemporaneous dinosaurs. Nevertheless, the most direct dietary evidence (i.e. preserved gut contents) of these interactions in fossil crocodyliforms has been elusive. Here we report on a new crocodyliform, Confractosuchus sauroktonos gen. et sp. nov., from the Cenomanian (92.5–104 Ma) of Australia, with exceptionally preserved abdominal contents comprising parts of a juvenile ornithopod dinosaur. A phylogenetic analysis recovered Confractosuchus as the sister taxon to a clade comprising susisuchids and hylaeochampsids. The ornithopod remains displayed clear evidence of oral processing, carcass reduction (dismemberment) and bone fragmentation, which are diagnostic hallmarks of some modern crocodylian feeding behaviour. Nevertheless, a macro-generalist feeding strategy for Confractosuchus similar to extant crocodylians is supported by a morphometric analysis of the skull and reveals that dietary versatility accompanied the modular assembly of the modern crocodylian bauplan. Of further interest, these ornithopod bones represent the first skeletal remains of the group from the Winton Formation, previously only known from shed teeth and tracks, and may represent a novel taxon.

Understanding the Impact of Trampling on Rodent Bones

Experiments based on the premise of uniformitarism are an effective tool to establish patterns of taphonomic processes acting either before, or after, burial. One process that has been extensively investigated experimentally is the impact of trampling to large mammal bones. Since trampling marks caused by sedimentary friction strongly mimic cut marks made by humans using stone tools during butchery, distinguishing the origin of such modifications is especially relevant to the study of human evolution. In contrast, damage resulting from trampling on small mammal fossil bones has received less attention, despite the fact that it may solve interesting problems relating to site formation processes. While it has been observed that the impact of compression depends on the type of substrate and dryness of the skeletal elements, the fragility of small mammal bones may imply that they will break as a response to compression. Here, we have undertaken a controlled experiment using material resistance compression equipment to simulate a preliminary experiment, previously devised by one of us, on human trampling of owl pellets. Our results demonstrate that different patterns of breakage can be distinguished under wet and dry conditions in mandibles, skulls and long bones that deform or break in a consistent way. Further, small compact bones almost always remain intact, resisting breakage under compression. The pattern obtained here was applied to a Pleistocene small mammal fossil assemblage from Wonderwerk Cave (South Africa). This collection showed unusually extensive breakage and skeletal element representation that could not be entirely explained by excavation procedures or digestion by the predator. We propose that trampling was a significant factor in small mammal bone destruction at Wonderwerk Cave, partly the product of trampling caused by the raptor that introduced the microfauna into the cave, as well as by hominins and other terrestrial animals that entered the cave and trampled pellets covering the cave floor.

Evidence of Fire Use by Homo erectus pekinensis: An XRD Study of Archaeological Bones From Zhoukoudian Locality 1, China

Zhoukoudian Locality 1 is well known both for the discovery of Homo erectus fossils and for the presence of early evidence of controlled use of fire by hominins; However, the nature of the latter had been seriously questioned since mid-1980s. To obtain substantial evidence of fire use by hominins, we combine macroscopic observations and XRD analysis on 23 fossil bones from new excavations in Layers 4 and 5. The crystalline index shows that at least 15 fossil bones were heated above 600°C, and this is partly consistent with macroscopic observations. The high intensity burning of bones may indicate strong evidence of hominin-controlled use of fire at Layer 4. Future work should focus on archaeological materials from lower layers to improve our understanding of the nature of colored bones and gain more solid evidence of fire use by early humans at Zhoukoudian.

Modern human teeth unearthed from below the ∼128,000-year-old level at Punung, Java: A case highlighting the problem of recent intrusion in cave sediments

The emergence of modern humans in the eastern edge of the Eurasian Continent is debated between two major models: early (∼130−70 ka) and late (∼50 ka) dispersal models. The former view is grounded mainly on the claims that several cave sites in Southeast Asia and southern China yielded modern human fossils of those early ages, but such reports have been disputed for the lack of direct dating of the human remains and insufficient documentation of stratigraphy and taphonomy. By tracing possible burial process and conducting direct dating for an early Late Pleistocene paleontological site of Punung III, East Java, we here report a case that demonstrates how unexpected intrusion of recent human remains into older stratigraphic levels could occur in cave sediments. This further highlights the need of direct dating and taphonomic assessment before accepting either model. We also emphasize that the state of fossilization of bones and teeth is a useful guide for initial screening of recent intrusion and should be reported particularly when direct dating is unavailable. Additionally, we provide a revised stratigraphy and faunal list of Punung III, a key site that defines the tropical rainforest Punung Fauna during the early Late Pleistocene of the region.

Oxygen Isotope Analysis of Pygmy Hippo's Fossil Bone and Tooth Apatite from Aghia Napa, Cyprus

Oxygen Isotope Analysis of Pygmy Hippo's Fossil Bone and Tooth Apatite from Aghia Napa, Cyprus

Cells and soft tissues in fossil bone: A review of preservation mechanisms, with corrections of misconceptions

Cells and soft tissues in fossil bone: A review of preservation mechanisms, with corrections of misconceptions

Variation, mosaicism and degeneracy in the hominin foot.

The fossil record is scarce and incomplete by nature. Animals and ecological processes devour soft tissue and important bony details over time and, when the dust settles, we are faced with a patchy record full of variation. Fossil taxa are usually defined by craniodental characteristics, so unless postcranial bones are found associated with a skull, assignment to taxon is unstable. Naming a locomotor category based on fossil bone morphology by analogy to living hominoids is not uncommon, and when no single locomotor label fits, postcrania are often described as exhibiting a 'mosaic' of traits. Here, we contend that the unavoidable variation that characterises the fossil record can be described far more rigorously based on extensive work in human neurobiology and neuroanatomy, movement sciences and motor control and biomechanics research. In neurobiology, degeneracy is a natural mechanism of adaptation allowing system elements that are structurally different to perform the same function. This concept differs from redundancy as understood in engineering, where the same function is performed by identical elements. Assuming degeneracy, structurally different elements are able to produce different outputs in a range of environmental contexts, favouring ecological robusticity by enabling adaptations. Furthermore, as degeneracy extends to genome level, genetic variation is sustained, so that genes which might benefit an organism in a different environment remain part of the genome, favouring species' evolvability.

Investigating Past and Present Carpometacarpus Morphology in Mimidae: A Multi-Methods Approach to Evidence from the Guadeloupe Islands

Past bird communities are still under-studied in several Caribbean regions, including the Lesser Antilles. In order to improve our understanding of this area’s avifauna, we explore morphometrical variations of the carpometacarpus (CMC) within West Indies Mimidae species. We combine geometric morphometric (GMM) and conventional osteology focusing on characters of the entire or distal portion of the CMC. Morphological variation related to their phylogenetic history is investigated using uni- and multi-variate statistics, and the expression of certain osteological characters. Fossil bone remains from the Guadeloupe Islands were included in the datasets to test the applicability of these results to the archaeological and paleontological record.Our results are consistent with the known phylogeny of Mimidae. The GMM analysis clearly differentiated taxa at both inter- and intra-generic levels, which when combined with osteological characters, allow fossil specimens to be determined to species. For the fossil record of Guadeloupe Islands, this concerns three taxa: the Scaly-breasted Thrasher Allenia fusca, the Gray Catbird Dumetella carolinensis, the first fossil occurrence of this bird in the Greater and Lesser Antilles, and the Brown Trembler Cinclocerthia ruficauda in Desirade and Marie-Galante, where the bird is now extirpated. These results are of particular interest for tracking the impact of environmental changes on the composition of West Indian bird communities.

Putative fossil blood cells reinterpreted as diagenetic structures.

Red to red-orange spheres in the vascular canals of fossil bone thin sections have been repeatedly reported using light microscopy. Some of these have been interpreted as the fossilized remains of blood cells or, alternatively, pyrite framboids. Here, we assess claims of blood cell preservation within bones of the therizinosauroid theropod Beipiaosaurus inexpectus from the Jehol Lagerstätte. Using Raman spectroscopy, Energy Dispersive X-ray Spectrometry, and Time of Flight Secondary Ion Mass Spectroscopy, we found evidence of high taphonomic alteration of the bone. We also found that the vascular canals in the bone, once purported to contain fossil red blood cell, are filled with a mix of clay minerals and carbonaceous compounds. The spheres could not be analyzed in isolation, but we did not find any evidence of pyrite or heme compounds in the vessels, surrounding bone, or matrix. However, we did observe similar spheres under light microscopy in petrified wood found in proximity to the dinosaur. Consequently, we conclude that the red spheres are most likely diagenetic structures replicated by the clay minerals present throughout the vascular canals.

TIPZOO: a Touchscreen Interface for Palaeolithic Zooarchaeology. Towards making data entry and analysis easier, faster, and more reliable

Zooarchaeological studies of fossil bone collections are often conducted using simple spreadsheet programs for data recording and analysis. After quickly summarizing the limitations of such an approach, we present a new software solution, TIPZOO, which uses a FileMaker touchscreen interface combined with R scripts and QGIS files. This tool was specifically designed for zooarchaeologists needs, and is freely available at http://tipzoo.cnrs.fr. In this article, the key features of TIPZOO are highlighted, and we present some of the tools developed in order to (1) simplify the use of recently published complex coding systems, (2) better control intra- and inter-analyst variation, and (3) allow faster and more reliable data entry, analysis and visualization in Palaeolithic zooarchaeology.

Whole‐body endothermy: ancient, homologous and widespread among the ancestors of mammals, birds and crocodylians

ABSTRACTThe whole‐body (tachymetabolic) endothermy seen in modern birds and mammals is long held to have evolved independently in each group, a reasonable assumption when it was believed that its earliest appearances in birds and mammals arose many millions of years apart. That assumption is consistent with current acceptance that the non‐shivering thermogenesis (NST) component of regulatory body heat originates differently in each group: from skeletal muscle in birds and from brown adipose tissue (BAT) in mammals. However, BAT is absent in monotremes, marsupials, and many eutherians, all whole‐body endotherms. Indeed, recent research implies that BAT‐driven NST originated more recently and that the biochemical processes driving muscle NST in birds, many modern mammals and the ancestors of both may be similar, deriving from controlled ‘slippage’ of Ca2+ from the sarcoplasmic reticulum Ca2+‐ATPase (SERCA) in skeletal muscle, similar to a process seen in some fishes. This similarity prompted our realisation that the capacity for whole‐body endothermy could even have pre‐dated the divergence of Amniota into Synapsida and Sauropsida, leading us to hypothesise the homology of whole‐body endothermy in birds and mammals, in contrast to the current assumption of their independent (convergent) evolution. To explore the extent of similarity between muscle NST in mammals and birds we undertook a detailed review of these processes and their control in each group. We found considerable but not complete similarity between them: in extant mammals the ‘slippage’ is controlled by the protein sarcolipin (SLN), in birds the SLN is slightly different structurally and its role in NST is not yet proved. However, considering the multi‐millions of years since the separation of synapsids and diapsids, we consider that the similarity between NST production in birds and mammals is consistent with their whole‐body endothermy being homologous. If so, we should expect to find evidence for it much earlier and more widespread among extinct amniotes than is currently recognised. Accordingly, we conducted an extensive survey of the palaeontological literature using established proxies. Fossil bone histology reveals evidence of sustained rapid growth rates indicating tachymetabolism. Large body size and erect stature indicate high systemic arterial blood pressures and four‐chambered hearts, characteristic of tachymetabolism. Large nutrient foramina in long bones are indicative of high bone perfusion for rapid somatic growth and for repair of microfractures caused by intense locomotion. Obligate bipedality appeared early and only in whole‐body endotherms. Isotopic profiles of fossil material indicate endothermic levels of body temperature. These proxies led us to compelling evidence for the widespread occurrence of whole‐body endothermy among numerous extinct synapsids and sauropsids, and very early in each clade's family tree. These results are consistent with and support our hypothesis that tachymetabolic endothermy is plesiomorphic in Amniota. A hypothetical structure for the heart of the earliest endothermic amniotes is proposed. We conclude that there is strong evidence for whole‐body endothermy being ancient and widespread among amniotes and that the similarity of biochemical processes driving muscle NST in extant birds and mammals strengthens the case for its plesiomorphy.

Taphonomic and Diagenetic Pathways to Protein Preservation, Part I: The Case of Tyrannosaurus rex Specimen MOR 1125.

Simple SummaryContrary to traditional views, fossil bones have been shown to occasionally retain original cells, blood vessels, and structural tissues that are still comprised, in part, by their original proteins. To help clarify how such remarkable preservation occurs, we explored the fossilization history of a famous Tyrannosaurus rex specimen previously shown to yield original cells, vessels, and collagen protein sequences. By analyzing the trace element composition of the femur of this tyrannosaur, we show that after death its carcass decayed underwater in a brackish, oxic, estuarine channel and then became buried by sands that quickly cemented around the bones, largely protecting them from further chemical alteration. Other bones yielding original proteins have also been found to have fossilized within rapidly-cementing sediments in oxidizing environments, which strongly suggests that such settings are conducive to molecular preservation.Many recent reports have demonstrated remarkable preservation of proteins in fossil bones dating back to the Permian. However, preservation mechanisms that foster the long-term stability of biomolecules and the taphonomic circumstances facilitating them remain largely unexplored. To address this, we examined the taphonomic and geochemical history of Tyrannosaurus rex specimen Museum of the Rockies (MOR) 1125, whose right femur and tibiae were previously shown to retain still-soft tissues and endogenous proteins. By combining taphonomic insights with trace element compositional data, we reconstruct the postmortem history of this famous specimen. Our data show that following prolonged, subaqueous decay in an estuarine channel, MOR 1125 was buried in a coarse sandstone wherein its bones fossilized while interacting with oxic and potentially brackish early-diagenetic groundwaters. Once its bones became stable fossils, they experienced minimal further chemical alteration. Comparisons with other recent studies reveal that oxidizing early-diagenetic microenvironments and diagenetic circumstances which restrict exposure to percolating pore fluids elevate biomolecular preservation potential by promoting molecular condensation reactions and hindering chemical alteration, respectively. Avoiding protracted interactions with late-diagenetic pore fluids is also likely crucial. Similar studies must be conducted on fossil bones preserved under diverse paleoenvironmental and diagenetic contexts to fully elucidate molecular preservation pathways.

A Cave Occupied by Cave Bears for Thousands of Years in the Sobrarbe-Pirineos UNESCO Global Geopark (Huesca, Aragon, Spain)

The Sobrarbe-Pirineos UNESCO Global Geopark shows an extremely well-developed underground karst relief as a result of the great abundance and thickness of its limestone formations. The most important Pleistocene vertebrate site within the Geopark is Coro Tracito Cave at Tella. The fossil association is made up exclusively of bones belonging to Ursus spelaeus from the upper Pleistocene, accumulated over several thousand years. Based on scientific analysis of the fossil bones, an interesting public outreach project has been organized, involving the refurbishment of the site within the cave and the creation of a permanent exhibition called the Tella Cave Bear Museum. These two infrastructures are visited by thousands of tourists each year and constitute the main geoscientific tourist attraction of the Sobrarbe-Pirineos Geopark.