Paleontological Record Research Articles

The Foraminifera Fossil Record of the Sedimentary Rock at Kotadjawa, Lampung, Indonesia: The Significance of Marine Paleontological Insight

Kotadjawa, located on the west coast of Lampung, directly faces the Indian Ocean. Lithified calcareous sedimentary beds are prevalently outcropped along this coastline. These beds likely belong to the Simpangaur Formation, which may be associated with the paleocoastal depositional environment and tectonic uplift of the Indian Ocean. Therefore, we investigated the paleontological record, focusing on foraminifera as potential indicators of the paleoenvironment. This study aimed to identify, record, and calculate the relative abundance of benthic foraminifera in the sedimentary beds of Kotadjawa, Lampung. The samples were prepared via chemical treatment of 10% H2O2 for 48 hours. Our results revealed a diversity of benthic foraminiferal fossils within the sedimentary rock. Notably, 11 benthic foraminifera genera were fossilized in the observed outcrop: Textularia (18.4%), Sigmoilopsis (16.5%), Rectobolivina (15.4%), Uvigerina (15.5%), Nodosaria (14.5%), Elphidium (11.5%), Lenticulina (7.7%), Hormosina (6.8%), Bolivina (6.8%), and Globobulimina (5.8%). These results suggested that the sedimentary beds exposed in our study area ranging from the foreshore to the deep ocean floor ecosystem. This suggests that a sediment mixing event, possibly triggered by a paleocatastrophic event, influenced the deposition of these beds. This study provides new insights into marine paleoenvironmental conditions and paleocatastrophic events along the west coast of Lampung, Sumatra.

The Early to Late Cretaceous (Albian–Cenomanian) transition in Putumayo, Colombia: a biostratigraphic and carbon isotope stratigraphic correlation for northwestern South America

Despite the rich geological and paleontological record of Colombia, the Putumayo region near Ecuador remains one of the least explored regions in the equatorial Neotropics, mainly due to its thick vegetation, deep rock weathering, soil formation, and ground cover, geographic remoteness, and inaccessibility of well-exposed outcrops. This has resulted in limited comparisons with neighboring basins and thus the generation of more comprehensive biostratigraphic correlations with western and northern South America, as well as other paleobiogeographic regions (e.g., Tethys, Western Interior Seaway). Here, we present 67 occurrences of uppermost Lower Cretaceous to lowermost Upper Cretaceous ammonoids and other macrofossils (e.g., bivalves, decapod crustaceans, osteichthyan fish remains, plant remains), as well as a δ13Corg chemostratigraphic curve derived from 105 samples from the middle Albian of the uppermost Caballos Formation and the upper Albian to lower Cenomanian lower Villeta Formation, collected in situ from a stratigraphic section exposed along the Mocoa–San Francisco Road, Putumayo, Colombia, here called the San Francisco section. The chemostratigraphic, carbon-isotope curve for the region shows a great similarity with the shape of the accepted curve for the late Albian Oceanic Anoxic Event 1d, which is characterized by a worldwide long positive δ13C excursion anomaly. The new biostratigraphic and isotopic data serve as a point of reference to compare the Putumayo Basin with neighboring basins (e.g., Marañon Basin in Perú, Oriente Basin in Ecuador, Upper Magdalena Valley Basin in Colombia), and thus the generation of more comprehensive upper Lower Cretaceous and lower Upper Cretaceous biostratigraphic and chemostratigraphic correlations for northwestern South America.

Unraveling the interplay between humans and carnivores in El Olivo Cave during the Middle and Upper Paleolithic period (Llanera, Asturias, Spain)

El Olivo Cave (Llanera, Asturias, Spain) is a small karst cave within the Aboño River watershed. It holds a significant archaeological and paleontological record dating from the Middle and late Upper Paleolithic, featuring several lithic artifacts and faunal remains in each archaeological level. The study of the faunal remains reveals a high representation of ungulates, with Cervus elaphus and Equus ferus being the main ones. Carnivores are also represented by diverse species such as Vulpes vulpes and Canis lupus, among others. The taphonomic analysis evidenced the presence of human activity, accompanied by a significant incidence of tooth marks across all stratigraphic units and water-related processes in the lower part of the sequence. During this temporal range, there were faunal accumulations of anthropogenic origin altered by the action of other agents, especially carnivores. A diverse array of carnivore used the same space and taking advanced of the anthropogenic residues as scavengers. Moreover, we suggest a commensal synanthropic behavior exhibited by foxes. Consequently, El Olivo Cave is an illustrative case to explore the carnivore action in levels with human presence, something unusual at the late Upper Paleolithic sites in Northern Iberia.

Using U-Pb detrital zircon systematics to constrain the architecture and provenance of the Ronda peridotites’ crustal hanging wall, S Spain

Detrital zircon geochronology is frequently used for sediment provenance analysis in orogenic belts, but it can also be applied to locate the boundary between basement and sedimentary cover in successions and tectonometamorphic units where the paleontological record is missing, and primary stratigraphic relationships have been erased by intense deformation and/or metamorphism. This is critical to differentiate metamorphic mineral associations, P-T conditions and deformational events associated with superposed orogenic cycles. In this work, detrital zircon geochronology has been applied to the Ronda peridotites’ crustal hanging wall (hinterland of the Alpine Betic Cordillera, southern Spain), apparently made up of two major tectonic units – the Jubrique unit and the Maláguide complex – separated by a major Alpine tectonic contact camouflaged in between low-grade metamorphic rocks.Our results show that pre-Paleozoic peaks (c. 650, 1000, 2000, and 2600 Ma) are common along the entire studied crustal sequence, and Paleozoic ages are only recorded in the upper part of the Jubrique unit (c. 290, 350, and 475 Ma) and in the Maláguide complex (c. 350 and 475 Ma). Thus, the Paleozoic rocks of the Maláguide complex, constituting the highest crustal unit overlying the Ronda peridotites, represent syn-to-late orogenic Variscan sediments deformed and slightly metamorphosed prior to the Alpine cycle. In contrast, the underlying Jubrique unit is made of a post-Variscan sedimentary cover deposited on a Variscan basement, with the contact between both (hidden unconformity?) located within low- to medium-grade schists. These data support the presence of a major tectonic contact between the Maláguide complex (Late Carboniferous maximum depositional ages) and the Jubrique unit (Early Permian maximum depositional ages), i.e. the Maláguide complex would have overthrust the Jubrique unit during the Alpine orogeny. These results indicate a Permian or younger exhumation/emplacement up to crustal levels of the Ronda peridotites subcontinental mantle slab.Altogether, these detrital zircon age spectra support a relatively, but not entirely local derivation of the studied crustal sequences (fragments of the Iberian Massif) and suggest some Mesozoic drifting with respect to its present position. Nonetheless, the different age distribution of the Paleozoic populations between the Jubrique (Alpujárride complex) and Maláguide samples suggests that the former deposited relatively close to other samples from the eastern-central Alpujárride complex and Nevado-Filábride complex, which, in turn, show strong similarities with the Cantabrian zone and NE Iberia (Iberian Massif). In contrast, the Maláguide samples were probably deposited close to the Ossa-Morena Zone (Iberian Massif) . Thus, Alpujárride/Nevado-Filábride and Maláguide complexes would have been juxtaposed during the Triassic-Cretaceous Neotethys rifting/drifting and/or the subsequent Alpine collisional events.

Sedimentological evolution of the Quibas site: High-resolution glacial/interglacial dynamics in a terrestrial pre-Jaramillo to post-Jaramillo sequence from southern Iberian Peninsula

The sedimentary infill of the Quibas karstic site (Early Pleistocene, southern Spain) represents the only continuous succession with remains of continental vertebrates in Europe from pre-Jaramillo to post-Jaramillo age. The Quibas site, with a significant paleontological record, is dated between 1.1 and 0.9 Ma and offers a unique opportunity to carry out a paleoclimatic reconstruction of the time period immediately after the arrival of the first humans to western Europe. For this reason, defining the dominant sedimentary processes in the different stratigraphic units and the associated paleoenvironment is essential. The Quibas site is made up of two karstic features with two stratigraphic sequences: Quibas-Cueva, containing six lithostratigraphic units, and Quibas-Sima, which contains seven lithostratigraphic units. The detailed description and analyses of the stratigraphic sections have allowed the characterization of various autochthonous and allochthonous facies of cave deposits. Paleoclimatic proxies, inferred from sedimentological analyses, reveal a record of several alternating humid and arid phases resulting from the Early Pleistocene glacial-interglacial cycles, allowing correlation to the marine oxygen isotope record. The lowermost units (pre-Jaramillo) were deposited during a long-lasting interglacial, correlated to MIS 33–31. It was followed by an increase in aridity in the intermediate units of Quibas-Sima and uppermost unit of Quibas-Cueva (Jaramillo), revealing the beginning of a glacial period at the start of the Jaramillo subchron (1 Ma), which can be correlated to MIS 30. The upper Jaramillo and post-Jaramillo units suggest these were deposited in alternating periods of aridity and humid conditions, although less humid than the pre-Jaramillo period, probably representing the MIS 29 interglacial, the MIS 28 glacial and the MIS 27 interglacial.

Nitrogen isotope gradient on continental margins during the late Paleoproterozoic

The late Paleoproterozoic was a key period in the evolution of Earth’s surface environments and life. It is generally accepted that during the 2.43–2.06 Ga Great Oxidation Episode, the atmospheric oxygen level rose to an intermediate state (0.1% to 10% of the present atmospheric level) and the chemical composition of the oceans changed significantly. The paleontological record indicates that eukaryotes appeared during the late Paleoproterozoic. Nitrogen, an essential nutrient for life, is thought to have been one of the key factors in eukaryote evolution. However, nitrogen bioavailability and spatial heterogeneity in nitrogen cycle in the late Paleoproterozoic oceans remain controversial. Here, we examine carbon and nitrogen cycling in the late Paleoproterozoic ocean, via analysis of redox-sensitive element contents and organic carbon and nitrogen isotope compositions of black shales of the ca. 1.9 Ga Nuvilic Formation of the Povungnituk Group, Cape Smith Belt, Canada. Two diamond drill-holes (DDHs) 718–3333 (∼50 m-long) and 4G8069 (∼90 m-long) investigated in this study contain turbiditic greywackes and black shales deposited on the northern margin of the Archean Superior craton below the storm wave-base. Sedimentary rocks of DDH 4G8069 might have been deposited closer to the continental source area, as indicated by sandstone abundance, than those of DDH 718–3333. Redox-sensitive element (V, U, and Mo) contents in black shales of DDH 4G8069 are low and show positive correlation with Al contents, whereas those of DDH 718–3333 are irregularly elevated. Fe/Al ratios of DDH 718–3333 are low, which likely reflect Fe loss from sediments under anoxic water-column conditions. Depositional environment is inferred to be above and below the redoxcline for DDHs 4G8069 and 718–3333, respectively. Organic carbon isotope values of DDH 718–3333 are approximately 1.7‰ lighter than those of DDH 4G8069, which might reflect methane cycling at the redoxcline. Nitrogen isotope values are positive (> +3‰) for all the black shale samples, corresponding to aerobic nitrogen cycling and presence of bioavailable nitrate on the northern margin of the Superior craton during the late Paleoproterozoic. Furthermore, nitrogen isotope values for DDH 718–3333 are approximately 2‰ heavier than those for DDH 4G8069. The observed isotopic heterogeneity is similar to that in modern oxygen-minimum zones and could represent intense denitrification at the redoxcline. Although no ca. 1.9 Ga microfossils reported to date are considered unambiguously eukaryotic, the aerobic nitrogen cycling inferred for the Nuvilic Formation, as well as for the previously studied Rove, Virginia, and Menihek formations, suggests that nitrogen limitation was unlikely to have inhibited biological evolution during the late Paleoproterozoic, a finding that is consistent with molecular clock studies suggesting that the emergence of eukaryotes occurred during the Paleoproterozoic.

An Updated Review of The Quaternary Hippopotamus Fossil Records from the Iberian Peninsula

This work presents a comprehensive review of the Quaternary fossil records of hippopotamuses from the Iberian Peninsula, unveiling biogeographical insights of global significance. The results presented herein include the inference of a delayed arrival of Hippopotamus (Hippopotamus antiquus) populations onto the Iberian Peninsula compared to other European Mediterranean regions, with an estimated age of ca. 1.7 Ma, in contrast to 2.1–2.2 Ma elsewhere. Moreover, we hypothesize the possibility of a short-lived coexistence between H. antiquus and Hippopotamus amphibius, close to the extinction of the former taxon (ca. 0.45 Ma). The local extinction of all hippopotamus populations on the Iberian Peninsula between MIS 5 and 3 is suggested here, mirroring proposals made for the Italian peninsula. Notable aspects of this fossil record include the abundance of specimens, previously undocumented anatomical elements, and partially complete individuals with articulated body segments. The remains analyzed herein also present different ontogenetic stages and sexual dimorphism. Moreover, the presence of specimens displaying paleopathologies provides valuable insights into ethological and paleoecological studies. The exceptional record of at least three events of human exploitation of hippopotamus stands out, with this being a rarity in the broader context of the archaeological and paleontological record of the European continent.

Anatomically preserved early Cretaceous lycophyte shoots; enriching the paleontological record of Lycopodiales and Selaginellales

Anatomically preserved lycophytes of the Lycopodiales and Selaginellales have been discovered among a diverse assemblage of plants and fungi in carbonate marine concretions at the Apple Bay locality along the shore of Holbert Inlet near the northern end of Vancouver Island, British Columbia, Canada. Lycopodialean stems are plectostelic and actinostelic, branch dichotomously, and are similar to both Lycopodicaulis oellgaardii and Lycoxylon spp. The Selaginella specimens represent the first anatomically preserved Selaginellales with excellent internal cellular preservation in the fossil record, and are described as Selaginella quatsinoense Rothwell et Stockey sp. nov. Stems have three and five exarch, monarch stelar segments, each of which is surrounded by an aerenchymatous endodermis with trabeculae. The leaf base is indented on the adaxial surface, suggesting the position of a ligule. These fossils document that species with diagnostic internal anatomy of modern Lycopodiales and Selaginellales evolved no later than the Valanginian of the early Cretaceous.

The palaeontological heritage of the Capo Vaticano – Monte Poro area (Vibo Valentia, Italy): research, protection, and management

The Late Miocene successions of the Capo Vaticano-Monte Poro (Southern Italy) area, well exposed at Cessaniti – Cava Gentile, preserve a palaeontological record particularly relevant for phylogenetic studies and paleogeographic reconstructions as well as for the popular scientific divulgation and museology. The rich record of Sirenians highly contributed to the knowledge of phylogeny and intraspecific variability of Metaxytherium serresii. The exclusive terrestrial mammal association, having African and Greco-Iranian affinities, allows intriguing suggestions in the paleogeography of the Central Mediterranean. New taphonomic analyses on invertebrates and vertebrates, here presented, suggest that the good fossil preservation is due to the rapid burial of skeletons in a semipermeable mixture of sandy/muddy sediments which were quickly cemented. Late partial dissolution of the carbonate cement among particles made the fossils easy to extract from the sediment. The collaboration among palaeontology researchers, fossil collectors, and local administrators, under the direction of Superintendence and the control of Carabinieri Command for the Protection of Cultural Heritage, allowed the recovery, study, and promotion of this precious paleontological record. The area has a good flow of tourists for the pleasant seaside, and fossiliferous sites could attract cultural tourism, through educational trails and a museum network which valorize the palaeontological and archaeological heritage of the hinterland.

Geomorphology, Geoarchaeology, and Geochronology of the Upper Pleistocene Archaeological Site of El Olivo Cave (Llanera, Asturias, Northern Spain)

El Olivo Cave (Pruvia de Arriba, Llanera, Asturias, Spain) is a small karst cave located in the Aboño River basin and formed in the Cretaceous limestone of the Mesozoic cover of the Cantabrian Mountains (north of the Iberian Peninsula). It contains an important upper Pleistocene sedimentary, archaeological, and paleontological record, with abundant technological evidence and faunal remains. The archaeological record shows a first occupation that could correspond to the Middle Paleolithic and a second occupation in the Middle Magdalenian. The stratigraphic sequence inside and outside the cave was studied with geoarchaeological methodology. In this paper, the lithostratigraphic sequence is analyzed, and the data from the granulometric, mineralogical, edaphological, and radiometric analyses are presented. The results of these analyses enable an accurate interpretation of both the lithostratigraphy of the deposit and the processes responsible for its formation and subsequent evolution. The available numerical dates allow us to locate the first sedimentation episode in the cave in OIS 7a, in the Middle Pleistocene, the base of the outer fluvial sedimentation in the cold OIS 3a stage of the Upper Pleistocene and the Magdalenian occupation in the Last Glacial Maximum (OIS 2) at the end of the Late Pleistocene.

The dawn of the Late Villafranchian: Paleoenvironment and age of the Pantalla paleontological site (Italy; Early Pleistocene)

Biochronology is the most widely used method for organizing the successions of continental vertebrate faunas in geological time and for allowing the correlation of continental deposits. However, due to the fragmentary nature of the paleontological record and the diachronicity of first and last occurrences of vertebrate taxa in different areas (i.e., bioevents), it is difficult to precisely define the temporal boundaries between biochronological units. That is why it is crucial to calibrate biochronological data with independent proxies wherever possible. Here, thanks to an interdisciplinary approach that combines sedimentology and stratigraphy, vertebrate paleontology, micropaleontology (ostracods), palynology, and geochronology, we provide a chronological framework and a paleoenvironmental reconstruction of the paleontological site of Pantalla (Central Italy). The combination between biochronological/biostratigraphic and geochronological (U-series/ESR dating and paleomagnetism) data allows us to refer the site to c. 2.2 Ma, i.e., in the transition phase between the Middle and Late Villafranchian in the European biochronological scheme. We reconstruct the environment as a fluvial area with a frequently flooded wet floodplain and marked (probably seasonal) variations of the water level of the channel river. The depositional system was surrounded by a conifer-dominated forest, which is suggestive of a glacial phase.

The shrews (Soricidae, Mammalia) of the Early and Middle Pleistocene of Gran Dolina (Atapuerca, Spain): reassessing their paleontological record in the Iberian Peninsula

Soricids are small mammals with a mainly invertebrate diet. They are generally termed insectivores and are part of the mammalian Order Eulipotyphla. Soricids of the Early-Middle Pleistocene postdating the Jaramillo subchron are poorly known in the Iberian Peninsula, except for Dolinasorex glyphodon, endemic to north Spain, and scattered records of Sorex minutus, Crocidura russula, Crocidura kornfeldi and indeterminate species of Crocidura, Sorex and Neomys. This is mainly due to the scarcity of sites and the fragmentary fossil remains. In contrast, the record of soricids in the rest of Europe during this period is wide: there are sites with up to ten different species in the same stratigraphic level. As Gran Dolina (Atapuerca, Spain) provides one of the best anthropological, archaeological and faunal records of the late-Early (post-Jaramillo) to early-Middle Pleistocene, and as this occurs in an excellent, well-studied stratigraphic sequence documenting terrestrial environments, we here undertake an exhaustive revision of 200 fragmentary mandibles of this group of small mammals. Nine soricid taxa were identified in this archaeo-paleontological site: Sorex minutus, Sorex ex gr. runtonensis-subaraneus, Sorex (Drepanosorex) ex gr. margaritodon-savini, Dolinasorex glyphodon, Asoriculus gibberodon, Neomys cf. newtoni, Neomys cf. fodiens, Neomyni cf. Macroneomys and Crocidura kornfeldi. This is the first record of Neomys cf. newtoni in the Iberian Peninsula, the second specimen of Neomyni cf. Macroneomys, and the youngest record of A. gibberodon worldwide. Some of these taxa exhibit particularities when compared to their counterparts in the rest of the continent, adding to the variability of the species. Relict populations of Asoriculus gibberodon endured in the Iberian Peninsula into post-Jaramillo times, even after they had already disappeared from the rest of Europe.

Describing a Newly Excavated Packrat Midden Near Natural Trap Cave, Wyoming to Help Assess Biases in Fossil Microfaunal Accumulation

Microfauna communities resulting from packrat accumulation provide crucial information about how natural communities respond to environmental changes. However, fossil accumulation mechanisms can be complex, making it difficult to interpret these community responses. Natural Trap Cave (NTC) is an open-mouth cave with an 85-foot drop that often lies unseen by passing animals, making it a major location for fossil accumulation. NTC, located in the Bighorn Mountains of Wyoming, has accumulated a paleontological record of the local community’s biota dating back to the Late Pleistocene, 25,000 years ago. The rim of the cave’s mouth is home to packrat middens located directly above the major deposits of microvertebrate (<5 kg) fossils. It is hypothesized that middens along the rim have accumulated seeds, bones, teeth, and bird pellets from the local communities over time and have periodically washed into the cave below. We seek to assess the bias in microvertebrate community composition introduced by packrat accumulation. We identified bones and teeth collected from a 9-section grid of a modern midden located adjacent to the cave, which allow us to see which species dominate the NTC environment. We calculate species evenness, richness, and relative abundances using MNI. To assess local bias resulting from packrat accumulation, we compare the modern midden with live-and camera-trap data of small mammal communities. To assess which NTC fossils result from packrat accumulation, we compare the modern midden with fossil material from within the cave, ranging in age from 2 to 20 ka. Once we understand these biases present in the fossil accumulation, we can associate species’ relative abundances with changes in climate, such as drought, increasing temperatures, and flooding. By knowing how climate has affected NTC species’ abundances through time, we will be prepared to aid in conservation efforts by predicting how species numbers will be affected by future climate change.

Precambrian–Cambrian Transition at the Igarka Uplift (Northwestern Siberian Platform)

Abstract —The Precambrian–Cambrian transition is one of the most fundamental evolutionary turnovers in the Earth’s history. However, in many cases precise identification and correlation of this crucial boundary in lithologically contrasting sections is complicated, even if the whole spectrum of biostratigraphic and chemostratigraphic methods is applied. The Precambrian–Cambrian transitional strata of the Igarka Uplift (Sukharikha Formation) perfectly illustrate this problem. This unit has arguably one of the most detailed carbonate carbon isotope curves for this time interval (at least within the Siberian Platform). However, an extremely poor paleontological record previously reported from the Sukharikha Formation makes identification of major stratigraphic boundaries highly debatable. We present a detailed study of the Sukharikha and overlying Krasnyi Porog formations in three sections (Sukharikha River, Kulyumbe River, and Khantaisko-Sukhotungusskaya-1 well). Our chemostratigraphic and biostratigraphic data provide a correlation basis for these sections and identify the Cambrian boundary in terms of both the International Chronostratigraphic Chart and General Stratigraphic Scale of Russia. We show that lithologic boundaries and levels of the local first appearance of Tommotian small skeletal fossils are diachronous within the Igarka paleobasin. The latter is putatively caused by paleoecology of the early Cambrian biota and by taphonomic factors. Our data specify the location of the Tommotian Stage (sensu lato)/Cambrian Stage 2 boundary in other key Precambrian–Cambrian transitional sections of the Siberian Platform.

First magnetostratigraphic results in the Aïn Beni Mathar-Guefaït Basin, Northern High Plateaus (Morocco): The Pliocene-Pleistocene Dhar Iroumyane composite section

The Aïn Beni Mathar-Guefaït Basin, in the High Plateau Region (Morocco), is dissected by the Za River, the main eastern tributary of the Moulouya, which incises more than 150 m into Plio-Pleistocene sediments. The main goal of the present study is to provide an initial geochronologic framework for such basin infill based on a combination of magnetostratigraphy and electron spin resonance (ESR). The combined results have implications on the age of the paleontological record, the evolution of the Moulouya River, and the activity of the faults that delimit the basin. We have studied sedimentary rocks that are essentially flat-lying and of an alluvial and lacustrine/palustrine origin. An approximately 140 m-thick section has been sampled at an average of 2.5 m per site, allowing to build a local magnetic polarity stratigraphy that includes nine geomagnetic reversals. Although no fold test is available, the presence of dual polarities and rockmagnetic analysis give us confidence that magnetization directions are primary. We then anchored the obtained magnetozones to the Geomagnetic Polarity Timescale (GPTS) using the biostratigraphic data as well as local geological observations. Our proposed magnetostratigraphy-based chronology reveals a Plio-Pleistocene sedimentary infill spanning from Gauss to Olduvai Chrons. The lower, detrital formations mostly fall within the normal Gauss Chron, whereas the upper lacustrine and palustrine carbonates, which are almost widespread to the top of the sedimentary fill, are Olduvai in age. These results provide the first chronological constraints for the basin fill in one of the largest intermontane basins of the High Plateaus. The new magnetostratigraphy also reveals that the major environmental change that triggered a switch from alluvial to lacustrine-palustrine conditions in Northern Maghreb occurred near the Gauss-Matuyama reversal, ca. 2.6 Ma. In addition, it shows that the age of the paleontological site Guefaït-4 is approximately 1 myr older than the ESR ages obtained from the quartz grains. The possible sources for this underestimation are discussed. However, we also acknowledge and discuss other possible chronostratigraphic interpretations of the current data, although less likely.

The game of models: Dietary reconstruction in human evolution

Despite substantial additions to the paleontological record and unanticipated improvements in analytical techniques since the Journal of Human Evolution was first published, consensus on the diet of early hominin species remains elusive. For instance, the notable advances in the analyses of hominin dental microwear and stable isotopes have provided a plethora of data that have in some instances clouded what was once ostensibly a clear picture of dietary differentiation between and within hominin taxa. In the present study, we explore the reasons why the retrodiction of diet in human evolution has proven vexing over the last half century from the perspective of both ecological and functional-mechanical models. Such models continue to be indispensable for paleobiological reconstructions, but they often contain rigid or unstated assumptions about how primary paleontological data, such as fossils and their geological and taphonomic contexts, allow unambiguous insight into the evolutionary processes that produced them. In theoretical discussions of paleobiology, it has long been recognized that a mapping function of morphology to adaptation is not one-to-one, in the sense that a particular trait cannot necessarily be attributed to a specific selective pressure and/or behavior. This article explores how the intrinsic variability within biological systems has often been underappreciated in paleoanthropological research. For instance, to claim that derived anatomical traits represent adaptations related to stereotypical behaviors largely ignores the importance of biological roles (i.e., how anatomical traits function in the environment), a concept that depends on behavioral flexibility for its potency. Similarly, in the paleoecological context, the underrepresentation of variability within the ‘edible landscapes’ our hominin ancestors occupied has inhibited an adequate appreciation of early hominin dietary flexibility. Incorporating the reality of variation at organismal and ecological scales makes the practice of paleobiological reconstruction more challenging, but in return, allows for a better appreciation of the evolutionary possibilities that were open to early hominins.

BONE MODIFICATION FEATURES RESULTING FROM BARNACLE ATTACHMENT ON THE BONES OF LOGGERHEAD SEA TURTLES (Caretta caretta), CUMBERLAND ISLAND, GEORGIA, USA: IMPLICATIONS FOR THE PALEOECOLOGICAL, AND TAPHONOMIC ANALYSES OF FOSSIL SEA TURTLES

Abstract Sea turtles are characterized by a wide variety of invertebrate ectoparasites. Few of these ectoparasites leave a permanent indication of their presence on the skeletal remains of their host taxa and thus represent ecological information doomed to be lost in the paleontological record. Some barnacle taxa provide an exception to this, in that they cause the formation of small, subcircular to circular divots, pits, and holes on the skull, mandible, carapace or plastron of sea turtles. Loggerhead Sea Turtle (Caretta caretta) skeletons from Cumberland Island, Georgia, USA were examined to assess the presence, frequency, and loci of occurrence of barnacle pits, and to establish which taxa are involved in pit development. Six types of divot and pit attributed to barnacles are identified in this study. Type I traces are shallow, oval/semi-circular in outline, with smooth, gently sloped bases. Type II traces are deep, hemispherical pits with smooth bases. Type III traces are deep, circular to subcircular pits with flat bases. Type IV traces are deep, circular to subcircular pits with multiple (4–6) small sub-pits on their bases. Type V traces are cylindrical, penetrative holes. Type VI traces comprise shallow ring-shaped grooves on the surface of the bone. Type I through III traces are identical to the ichnotaxon Karethraichnus lakkos. Type IV traces have not, as yet, been described in the rock record. Type V traces are identical to K. fiale. Type VI traces are identical to Thatchtelithichnus holmani. Barnacle taxa identified as emplacing non-penetrative divots and pits on C. caretta skulls, mandibles, and shell bones include Chelonibia caretta (Type I), Platylepas hexastylos (Types I–IV), Calyptolepas bjorndalae (Types I and II), and Stomatolepas elegans (Types I and II). Type V traces were most likely emplaced by either Stephanolepas muricata or Chelolepas cheloniae. Type VI traces reflect the former attachment of balanid or lepadid barnacles. Embedded barnacles were observed in epidermal material associated with Types I through IV traces but not for Type V and VI traces and thus the relationship is inferred for these latter traces. Barnacle-related pits, divots, and holes are believed to result from barnacle mediated chemical corrosion into the outer surface of sea turtle bone. The occurrence of these traces provides one of the few preservable lines of evidence of barnacle interactions with sea turtle hosts. Identification of definitive barnacle borings in fossil material will provide evidence of the evolution of platylepadid barnacles and the development of their commensal relationship with chelonid turtles.

Paleobiogeography of Crown Deer

The article describes the paleobiogeographic history of the modern subfamilies so-called “crown deer” of the family Cervidae (Artiodactyla, Mammalia) in the world from the late Miocene to the late Pleistocene. The study overviews the taxonomic diversity and evolutionary radiation of Cervidae from all zoogeographic realms where this systematic group is present in the paleontological record. The evolutionary diversification of the fossil Cervidae is based on the estimations of species body masses that are regarded here as a proxy of occupied ecological niches. The study reveals two important evolutionary radiations of Cervidae during the late Miocene of Eurasia that gave the origin of the modern subfamilies Cervinae and Capreolinae. The evolutionary radiation of Capreolinae during the Pleistocene in South America shows a range of diversity comparable to the late Miocene radiations of Old World deer and provides multiple examples of evolutionary convergences with Eurasian Pleistocene cervids. The article discusses factors that shaped the modern biogeographic distribution of representatives of the subfamilies Cervinae and Capreolinae.

Experimental dissolution of fossil bone under variable pH conditions.

Fossils exposed at the surface are an integral component of the paleontologic record and provide an archive of past life. However, it is widely known that fossils are not stable indefinitely upon exposure to surface conditions such as physical, chemical, and biological processes, and this last phase of taphonomy is poorly understood. Studies regarding the longevity of fossils subject to weathering, such as acidic precipitation, are absent in the literature. The goal of this study was to experimentally determine vertebrate fossil dissolution rates under variable pH conditions in a controlled laboratory setting. It was hypothesized that fossils would dissolve within acidic solutions and do so at an increasing rate when exposed to increasingly acidic solutions. The experiments were conducted on three fossil vertebrae in triplicate in closed reaction vessels at pH 4, 5, and 6. The fossils were completely submerged for 21 days in a tap water solution with the pH adjusted using 0.1N hydrochloric acid (HCl). Fossil dissolution was quantified by changes to: (1) fossil mass; (2) elemental chemistry of water and fossils with inductively coupled plasma mass spectrometry (ICP-MS); (3) fossil mineralogy with X-ray diffraction (XRD); and (4) histologic structures with thin section analyses. All fossils exhibited mass loss, which increased with decreasing pH conditions, and was greatest under pH 4 (477 to 803 mg loss). The elemental analyses with ICP-MS indicated an increase of both calcium (maximum increase of 315 ppm) and phosphorus (increase of 18 ppm) in aqueous solutions with increasing pH and a loss of those same elements from the fossils (maximum loss of 10 ppm Ca and 6 ppm P). XRD revealed loss of gypsum in all post-dissolution samples. Taken together, the results of ICP-MS and XRD suggest dissolution of the primary mineral phases, including hydroxylapatite, and secondary phases, particularly calcite and gypsum, resulting in an estimated mass loss at pH 4 of 23 to 28 mg per day. Thin section analysis showed degradation of both cortical and trabecular bone in all post-dissolution images, demonstrating physical changes to the fossils as a result of water-rock interactions. These findings constitute the first quantitative analysis of fossil dissolution rates and provide insights into this last stage of taphonomy, addressing a largely understudied potential bias in the vertebrate fossil record.

Description of new Pliocene to Early Pleistocene deer (Cervidae, Mammalia) remains from the Siwalik Hills in Pakistan with a discussion on paleobiogeography of cervids from the Indian subcontinent

This article presents a description of new antler remains from five fossiliferous sites (Sardhok, Panjan Sher Shahana, Puran, Jari Kas, and Potha) of the Upper Siwaliks in Pakistan. The systematic study of the antler material revealed the presence of six cervid forms: Metacervocerus punjabiensis, Rucervus sp., Panolia sp., Hyelaphus sp., Praesinomegaceros bakri, and a poorly represented large cervid that shows a certain affinity with “Eucladoceros sp.” from the Early Pleistocene of Kuruksai (Tajikistan). The remains of Panolia represent the earliest known paleontological record of this cervid lineage. Unlike Metacervocerus and Rucervus that have had phylogenetically closely related counterparts in east and north of the Alpine-Himalayan mountain belt, the evolution of Panolia took place in the Indian subcontinent. The entry of Panolia lineage into the Indian subcontinent marks its phylogenetic split from the main Cervus/Rusa evolutionary branch. The earliest dispersal events of cervids into the Indian subcontinent was preceded by the late Miocene evolutionary radiation and ecological diversification of the subfamily Cervinae in Southeastern Asia. Praesinomegaceros and Metacervocerus most probably entered the Indian subcontinent via Central Asia. Possibly, this is also the case of “Eucladoceros sp.” from Kuruksai (Tajikistan). The dispersal ways of Panolia and Rucervus remain unclear. The dispersals of small-sized cervids (Muntiacus and Hyelaphus) into the Indian subcontinent was triggered by the establishment of the 100-ky glaciation cycle during the Middle Pleistocene: the sea level dropped during glacial peaks and opened to them the dispersal route from Sundaland in the South.