Fossil Molluscs Research Articles

Gastropod, cephalopod, and tentaculitid fauna from the Takche Formation (Ordovician-Silurian), Tidong Valley, Kinnaur Himalaya

ABSTRACT We describe a small collection of Late Ordovician gastropods Holopea? sp. Hormotoma sp. Poleumita? sp. Gyronema rupestre; cephalopod Discoceras sp. unidentified Nautiloids, and rare Tentaculites sp. from the Takche Formation (Ordovician-Silurian) exposed in the Tidong Valley (Kinnaur) of the Tethyan Himalaya. This is the first report of mollusc fossils from the Ordovician-Silurian successions of the Tidong Valley, Kinnaur. The reported Late Ordovician gastropods are also known from Baltica, suggesting a probable oceanic link between these remote regions. Tentaculites from the Takche Formation does not resemble any Baltic or North American tentaculitoids and show greater resemblance to the tentaculitoids from the other Gondwanan regions.

Non-destructive Analytical Study of Raman Spectra Variations and Mechanisms of Calcite and Aragonite in Modern and Fossilized Oysters.

Oyster fossils are some of the most common bivalve mollusk fossils found all over the world, they are different from other fossils because the oyster is still alive in the present day, and the body structure of modern oyster is almost the same as that of ancient one. Therefore, we designed a control experiment comparing the Raman spectra of minerals from both modern oysters and fossil oysters to explore the mechanism of oyster's fossilization process, which is considered to be helpful for investigating biological evolution or paleoenvironment. The oyster fossil sample was found in Nagi-Cho, Okayama Prefecture, Japan. We focused on the variations of band position and full width half-maximum of ν1 Raman band (symmetric stretching mode) of calcite (CaCO3) from modern and fossil oysters and the mineral conversion between calcite and aragonite (CaCO3) around the adductor muscle inside the oyster. Compared to modern oysters, the ν1 band at around 1086 cm-1 of calcite from oyster fossils shifted to a high wavenumber region, and the possible reason for this phenomenon is considered an elemental substitution between Ca2+ and Mg2+. As for aragonite around adductor muscle in fossil oysters, it has been found by Raman spectra that most of the aragonite has been converted into calcite because calcite has a relatively more stable structure.

A new species of Lysinoe (Gastropoda: Helicoidea) from the Oligocene of Mexico

In her 1945 study on the Tertiary fossil mollusks of northeastern Mexico, Gardner listed only 2 taxa of land snails: Holospira eva Gardner, 1945 and “Helix” sp. The latter is recognized here as a new species of Lysinoe Adams & Adams, 1855 (Helicoidea, Xanthonychidae). The new species can be diagnosed from its congeners by its flattened shell profile, a lower body whorl with a faint angulation on its median portion, a ridge-like angulation around the umbilicus, and a likely wide umbilicus. The species is known to occur in 2 nearby Upper Middle Oligocene outcrops in the eastern part of the state of Nuevo León.

Paleodepositional Environment of Kaliwangu Formation based on Mollusc Fossils Assemblage in Ciwaringin River, Leuwimunding Area, Majalengka, West Java, Indonesia

Abstract The Kaliwangu Formation in the Leuwimunding area, Majalengka Regency, West Java Province, Indonesia is exposed in the Ciwaringin River and its tributaries. This location contains abundant mollusc fossils. However, it has not been mentioned in the Javan Mollusk Neogen Stages. The exposed rocks are Pliocene sandstones and claystones layers. The purpose of this study was to determine changes in the paleodepositional environment at the study site based on the mollusc fossils content. Data was collected from fieldwork by measured section in 8 observation locations containing mollusc fossils along the Ciwaringin River. The mollusc fossils of the rework results were separated, then an association was made for the molluscs based on the abundant fossils found in each layer. The results of the preparation of fossils on 11 rock samples obtained 309 individuals from 63 specimens of molluscs. From these samples, there are 11 mollusc association were determined. The sequence from bottom to top are: Marginella ventricosa sangiranensis association, Arca nodosa association, Paphia sp. association, Turritella simplex – Placuna sp. associations, Natica zebra – Bicorbula tjiguhanensis association, Timoclea bataviana – Turritella bantamensis association, Nassaria suturalis tjemoroensis association, Ostrea sp. association, Timoclea bataviana association, Arca nodosa – Columbella sp. association, and Turritella djadjariensis – Turritella javana association. The mollusc fossils association shows 3 paleodepositional environments and there are 6 changes in the paleodepositional environment, namely from intertidal – subtidal to intertidal, shallow marine, subtidal, shallow marine, subtidal, and returning to shallow marine. In general, there was a rise in sea level at this location.

Middle Eocene molluscan fossils from the Siju Formation of the Garo Hills, Meghalaya, India

Bivalves and Gastropoda are collected from the Siju Formation of South Garo Hills, Meghalaya, India. Eighteen molluscan taxa are recorded, that is, nine taxa of bivalves and nine taxa of gastropods. These are comprising Ostrea ( Ostrea) adbasaensis, Lucina rakhiensis, Lucina ( Lucina) yawensis, Trachycardium minbuense, Mactra ( Mactra) protoreevesii, Pitar ( Calpitaria) carteri, Paphia ( Callistotapes) pseudoliratus, Tellina ( Peronaea) planta, Corbula ( Bicorbula) praexarata, Natica coxi, Seila stracheyi, Euspira soriensis, Semicassis mekranica, Oliva ( Strephona) australis var. indica, Conus ( Lithoconus) kyudawonensis. Dolium ( Eudolium) arabicum, Gistortia ( Vicetia) depressa and Planorbis sp. The detailed systematic description of the present molluscan fossils is studied. One zone is established, that is, Lucina yawensis– E. soriensis zone, for correlation purpose and dating. Overall, the zone is based on the total range of molluscan species and name accordingly. The present zone has been assigned to Middle Eocene in age.

Amplified seasonality in western Europe in a warmer world.

Documenting the seasonal temperature cycle constitutes an essential step toward mitigating risks associated with extreme weather events in a future warmer world. The mid-Piacenzian Warm Period (mPWP), 3.3 to 3.0 million years ago, featured global temperatures approximately 3°C above preindustrial levels. It represents an ideal period for directed paleoclimate reconstructions equivalent to model projections for 2100 under moderate Shared Socioeconomic Pathway SSP2-4.5. Here, seasonal clumped isotope analyses of fossil mollusk shells from the North Sea are presented to test Pliocene Model Intercomparison Project 2 outcomes. Joint data and model evidence reveals enhanced summer warming (+4.3° ± 1.0°C) compared to winter (+2.5° ± 1.5°C) during the mPWP, equivalent to SSP2-4.5 outcomes for future climate. We show that Arctic amplification of global warming weakens mid-latitude summer circulation while intensifying seasonal contrast in temperature and precipitation, leading to an increased risk of summer heat waves and other extreme weather events in Europe's future.

Large theropod teeth from the Upper Cretaceous of Guangdong Province, Southern China

Cretaceous dinosaur and other terrestrial tetrapod fossils are common throughout Guangdong Province (southern China), with the greatest documented concentrations in the Heyuan and Nanxiong basins and the Ganzhou area. Further south, the Sanshui Basin has a continuous Lower Cretaceous-Eocene sequence. Within the Sanshui Basin, abundant ostracod and mollusk fossils have been documented from the Upper Cretaceous sediments, but vertebrae fossils are rare. Here we report four isolated teeth collected from the Maastrichtian of the Sanshui Basin. Although fragmentary, the teeth can be confidently referred to the Tyrannosauroidea. These teeth constitute the first record of large theropods in southern Guangdong and are also the southernmost record of tyrannosauroids in China.

Alpine travellers in the Carpathians: The story of two rock‐dwelling snails told by genes and fossils

AbstractAimVarious species distributed in the Alps have their disjunct occurrences in the Carpathians. Fossil evidence for some woodland snails of Alpine distribution suggests that they colonized the Carpathians during the Holocene forest optimum or later. Here, we focus on disjunct Carpathian populations of the rock‐dwelling alpine snail Pyramidula saxatilis. As it occupies very stable habitats, that is, high‐elevation limestone rocks, one can assume its potential survival in Carpathian refugia over the glacial period(s). For comparison, the more widespread and warm‐climate P. pusilla is analysed.LocationEurope.TaxonPyramidula saxatilis and P. pusilla.MethodsWe analysed the genetic diversity of P. saxatilis and P. pusilla populations across their entire ranges using mitochondrial DNA and nuclear DNA markers. Seven fossil mollusc successions from the area where P. saxatilis occurs in the Carpathians were analysed and dated using the radiocarbon method. Habitat suitability models of both species were calculated for selected time periods since the Last Glacial Maximum.ResultsAll Carpathian P. saxatilis populations were genetically homogeneous and similar to those from the Eastern Alps. In P. pusilla, we found a genetically distinct lineage in the southern Western Carpathians. Both species were found in three fossil profiles since the Middle Holocene, and in one already in the Late Glacial. Habitat suitability models suggested the fluctuations of suitable conditions in the Carpathians driven by summer precipitation, especially for P. saxatilis.Main ConclusionsOur results suggest that the Carpathian populations of P. saxatilis represent a post‐LGM colonization from the Eastern Alps triggered by climatic changes, mainly by the increase in summer precipitation during the Late Glacial interstadials and Middle Holocene. The evidence for P. pusilla is similar, but also suggests rare long‐term survival in the Carpathian microrefugia. The palaeoecological evidence indicates a possible threat to high‐elevation species from future fluctuations in precipitation regimes.

Estimating the amount of uplift from the current elevation of strata at the Middle Miocene Climatic Optimum: A case study of Kibi Plateau in Southwest Japan

AbstractThe Middle Miocene Climatic Optimum (MMCO) formed shallow marine strata on continents and island arcs at ~15 Ma, and some of the MMCO strata later experienced uplift. The amount of uplift corresponded to sea level rise after the MMCO period, but ancient sea level could not be observed. This study uses a deductive approach to estimate the amount of uplift. The elevation of the youngest marine sedimentary layer of the MMCO strata approximates the sea level at the MMCO. The current elevation was reconstructed by adding the amount of denudation from the MMCO to the current elevation of the denuded MMCO strata at the outcrops, considering isostatic compensation. The amount of denudation since the MMCO period was estimated to be 180 m based on the global average denudation rate (Willenbring et al., 2013), and the estimated isostatic rebound was 153 m. By comparing the current, albeit virtual, elevation of the youngest marine sedimentary layer in the MMCO strata with sea level at the MMCO, the amount of uplift was estimated. For the MMCO sea level, a 66 m ice‐free line was adopted. This method was applied to the Kibi Plateau in Southwest Japan, where the MMCO strata are distributed. The reliability of the denudation amount of 180 m for the MMCO strata was confirmed by paleo‐water depths estimated using benthic foraminifera and mollusk fossils. The largest uplift of 504 ± 27 m occurred at the Jinseki‐Kogen since 15 Ma. A positive correlation was observed between the amount of uplift and the current altitude of the Kibi Plateau. The Kibi Plateau's topography most likely evolved after the MMCO. It is concluded that a new perspective on estimating the uplift was obtained by taking denudation into account.

Laetoli, Tanzania: Extant terrestrial mollusc faunas shed new light on climate and palaeoecology at a Pliocene hominin site.

Laetoli, Tanzania is one of the most important palaeontological and palaeoanthropological localities in Africa. We report on a survey of the extant terrestrial gastropod faunas of the Laetoli-Endulen area, examine their ecological associations and re-examine the utility of Pliocene fossil molluscs in palaeoenvironmental reconstruction. Standardised collecting at 15 sites yielded 7302 individuals representing 58 mollusc species. Significant dissimilarities were found among the faunas of three broad habitat types: forest, woodland/bushland and open (grassland and scattered, xeric shrubland). Overall, more species were recorded in the woodland/bushland sites than in the forest sites. Open sites were less diverse. Environmental factors contributing most strongly to the separation of habitat types were aridity index and elevation. The results are supplemented with new mollusc data from the Mbulu Plateau south of Lake Eyasi, and compared to the list of species cumulatively recorded from the Ngorongoro area. Some regional variation is apparent and historical factors may explain the absence of some fossil taxa from Laetoli today. Differences in seasonality separated upland forest sites on the Mbulu plateau from those at Lemagurut at Laetoli. Indicator species were identified for each habitat. These included several large-bodied species analogous to the Laetoli Pliocene fossil species that were then used for palaeoenvironmental reconstruction. Based on the estimated aridity index, and adopting the widely used United Nations Environment Programme (UNEP) global climate classification, the four stratigraphic subunits of the Upper Laetolil Beds (3.6-3.85 Ma) would be placed in either the UNEP's Dry Sub-humid or Semi-arid climate classes, whereas the Upper Ndolanya Beds (2.66 Ma) and Lower Laetolil Beds (3.85-<4.36 Ma) would be assigned to the Humid and Semi-arid climate classes respectively. Pliocene precipitation at Laetoli is estimated as 847-965 mm per year, refining previous estimates. This is close or slightly higher than the present mean annual precipitation, and is likely to have corresponded to a mosaic of forest, woodland and bushland within a grassland matrix consistent with other reconstructions.

Predatory drilling on molluscan assemblages along the Patagonian shelf (southern Argentina)

Abstract Both present-day and fossil molluscan assemblages offer an opportunity for a better understanding of the structure and organization of both modern and past benthic communities. In this framework, drill holes are used widely to explore predator–prey interactions. This research focuses on predation marks, especially drill holes, recorded on modern molluscan assemblages in a Patagonian sector of the Argentinean continental shelf. Shelled molluscs (n = 2179) were recovered from 27 to 135 m depths covering a long latitudinal extent (between 39° and 54°S). For each station, taxonomic position, ecological composition and relative abundance of taxa were determined, and then drilling frequency (DF) was calculated to infer drilling intensity. The collected molluscs belong to 37 families, with Veneridae being the most abundant in terms of the number of specimens (n = 419). Specimens with drill holes (n = 226) belong to 21 families (with at least 33 different species). Most of them are suspension feeders (85.8%) and the remaining percentage comprised other trophic types. Naticids and muricids, as main potential predators, together account for 19.6% of the gastropods present in the molluscan assemblages. DF across all the stations was moderate (9.9%) but varied between low (0–2.4%) and high (28.9%). These results do not show a trend linked to latitude or depth, and the great variability of DF between stations suggests that other local ecological or environmental conditions would influence drilling predation at a small spatio-scale.

Holocene transformation of natural steppe into an agricultural landscape in the Polabí and Pojizeří Lowlands, Czech Republic, based on mollusc evidence

Recent zonal steppes of Eastern Europe and South-West Asia have their origin in the glacial steppe with its specific continental climate. The westernmost edge of the steppe belt in Central Europe has been climatically shifted from a continental course during the Last Glacial to a rather oceanic one during the Holocene. Steppe enclaves could survive only locally in the driest parts of this area, but as we have confirmed, early arrival of Neolithic agriculture played a significant role in their preservation as well. While pollen analyses can provide the main pattern of landscape development, mollusc successions provide more information about landscape details we need for a better understanding of a steppe transformation towards the recent agricultural ecosystems. Based on the study of 18 mollusc successions in two neighbouring lowlands in the chernozems and alluvial areas of Central and North Bohemia, we described a postglacial development of these two climatically different agricultural landscapes. Based on mollusc evidence, we illustrated the impoverishment of forest communities and the continual occurrence of open habitats throughout the forest climatic optimum of the Holocene. Since the Neolithic colonisation, several erosion events were observed in many profiles documented by a lack of preserved fossil molluscs and layer redeposition which are in excellent agreement with the reconstruction of the fluvial sedimentation and vegetation in the Elbe River floodplain and with the continual settlement of this area. Because we have evidence of a fully developed forest fauna in the Eem interglacial from the Polabí lowland we know that the impoverishment of forest communities and the occurrence of open habitats during the interglacial forest climatic optimum is characteristic only of the Holocene.

A Class Project for Investigating Possible Future Local Effects of Global Climate Change through Student Analysis of Fossil Faunas

A common question posed to environmental scientists by nonscientists, particularly policymakers, is the following: In a world that is globally warmer, what will the new climate be like in specific geographical regions? This question has been and continues to be addressed by computer modeling, a technique that is out of reach for vast majority of students. However, an alternate approach to investigating this issue exists that is more practical for students. Past climates can be inferred for specific regions from fossils, utilizing climate tolerances of related modern organisms. When these inferred past climates correspond to periods of the Earth’s history where levels of carbon dioxide were as high or higher than today, these data can be used to extrapolate possible future local climates in a globally warmer world. The last Pleistocene interglacial period (known as the Eemian), which occurred approximately 120,000 years ago, is an ideal time period for studies of this kind for the following reasons. First, carbon dioxide levels were elevated at this time to levels approximating modern global conditions, and the world was warmer as evidenced by a much higher sea level than exists today. Secondly, most Eemian-age animals (especially mollusks) still exist, have known climate tolerances, and are relatively common as fossils. Students examining fossil mollusk faunas have applied this methodology to infer the Eemian climates of South Florida and coastal Virginia and found unexpectedly that for both regions the Eemian climate did not greatly differ from the modern one. The methodology described here can be used to address other important questions and puts such authentic and potentially valuable scientific research within practical reach of student scientists.

Paramagnetic characterization of fossil mollusc shells at eastern part of the old Konya lake: its importance for EPR dating.

Fossil mollusc shells are used for dating geological materials because they are well preserved throughout geological time. In this study, the radicals in the structure of fossil mollusc shells (Dreissena iconica, Valvata piscinalis, Bithynia tentaculate, Unio pictorum) collected from the Eastern Part of Old Konya Lake in Türkiye were investigated by EPR technique. For all fossil shells, microwave and temperature dependence of the signals were examined, and the signals suitable for dating are discussed. Characteristic features of intrinsic and impurity-related radicals were identified and the importance of paleontological evaluation of molluscs to get a reliable equivalent dose in EPR dating studies was emphasised.

Global Crystallographic Texture of Pyrite in Fossil Wood (Jurassic, Oryol Region, Russia)

Many works are devoted to the study of the crystallographic texture of primary skeletal minerals of animals. But how the directions of mineral crystals that replace the organic matter in the fossil state are oriented is unknown. Here we investigated the crystallographic texture of pyrite grown on an organic matrix and without it. Jurassic pyritized wood (Middle Jurassic, Callovian) was studied by the neutron diffraction method. The global crystallographic texture of pyrite in nodules and fossil wood is compared. It was found that in both cases, the isoline patterns of pole figures and texture sharpness are similar to the same characteristics of abiogenic calcite. But the orientations of pyrite crystals in wood are more ordered, the isolines are closer, and the regions of maximum pole density are wider. That is, the pyrite crystals that replaced the petrified wood are more ordered. This was influenced by the organic matrix on which the crystals grew. Repetition of a fossil mollusk shell shape without using its shell as a matrix for crystal growth does not lead to an increase in the crystallographic texture sharpness. This is illustrated by an example of the inner core calcite shell of the gastropod mollusk Bellerophon sp.

The Clacton-on-Sea (Essex, UK) GCR site and SSSI: New data and continuing importance

The complex Geological Conservation Review (GCR) site at Clacton-on-Sea, Essex, was notified in 1986 as a Site of Special Scientific Interest. It is an internationally important geosite and Britain's only Lower Palaeolithic type locality, giving its name to the Clactonian stone-tool industry. Fossil- and artefact-bearing channel-fill deposits laid down by the River Thames ~420,000 years ago, during the Hoxnian Interglacial (Marine Isotope Stage 11c), have been observed in foreshore and cliff exposures, and beneath developed and open ground in an inland arcuate footprint. These sediments provide a record of the lower reaches and estuary of the Thames during this lengthy and warm interglacial, an important partial analogue for the Holocene. Palaeoclimatic and palaeoecological evidence has been obtained from assemblages of fossil molluscs, ostracods and vertebrates, together with pollen and plant macrofossils; Clacton is also the type locality for several of the represented animal taxa, including the biostratigraphically significant ostracod Scottia browniana and a large subspecies of fallow deer, Dama dama clactoniana. This paper provides an overview of the continuing importance of the Clacton GCR site and Site of Special Scientific Interest (SSSI), summarizing recently acquired data that have enhanced understanding of the Hoxnian and the palaeoenvironments that prevailed at the time of deposition. The wider geosite has benefitted from sustained Palaeolithic archaeological interest, with the local planning authority mandating investigation of the sediments as a condition for development projects. SSSI status ensures that the significant collections of palaeontological and archaeological material amassed from the Clacton deposits over almost two centuries can be related to their context, and studies of both these archived collections and new material from the protected in situ sediments continue to provide new data and contribute to the development of cutting-edge techniques.

SALINITY-RELATED PRESERVATION OF MOLLUSKS IN SHALLOW LAKES: IMPLICATIONS FOR THE UNDERSTANDING OF THE LACUSTRINE PAMPEAN FOSSIL RECORD

ABSTRACT Premortem and postmortem processes significantly influence the formation of the molluscan fossil record in freshwater environments. Despite their importance for paleoenvironmental studies, they remain poorly understood. In Pampean shallow lakes, Holocene shell deposits of the euryhaline snail Heleobia parchappii show a relation with salinity, as preservation seems to be favored by brackish-saline water conditions. To explore if this pattern may respond to ecological (i.e., differential survival and reproduction) or taphonomic processes acting differently in freshwater and brackish-saline environments, we conducted a field-based study comparing premortem (abundance, length, width/length ratio, and crushing resistance in living and dead shells) and postmortem (fragmentation, fine-scale surface alteration, and loss of periostracum of dead shells) attributes along a modern lacustrine salinity gradient (0.5–40 ppt) in the Pampa plain of Argentina. Snails from saline lakes were smaller and more rotund than those from freshwater lakes, exhibiting higher abundances and resistances in death assemblages. They showed the highest fidelity in shell length and the best states of preservation, which were similar to values recorded in fossil shells. We concluded that shells deposited in saline lakes are better preserved than those deposited in freshwater lakes, giving rise to highly abundant shell concentrations, analogues to those shell-rich fossil levels recorded in Pampean lakes. Such abundance does not reflect the natural abundances of living snails, but rather is the result of the combined influence that less destructive environments and better shell intrinsic properties have on preservation.

Putative hydroid symbionts recorded by bioclaustrations in fossil molluscan shells: a revision and reinterpretation of the cecidogenus Rodocanalis

AbstractThe fossil record yields a peculiar phenomenon in different kinds of molluscan shells: bioclaustrations formed around (epi)symbionts during growth of the hosts' shell margin. Four morphologies, two of them formerly considered bioerosion traces, are here united in the parataxonomy of bioclaustration structures under the revised cecidogenus Rodocanalis. These are: (1) simple linear grooves (Rodocanalis linearis csp. nov.) formed below the periostracum in Pleistocene to Recent endobenthic bivalves; (2) series of distally ramifying grooves (Rodocanalis runicus) in Silurian orthoconic nautiloids; (3) irregular networks of grooves (Rodocanalis reticulatus) in Jurassic to Cretaceous bivalves and gastropods; and (4) regular reticulate networks (Rodocanalis geometricus csp. nov.) in Jurassic to Cretaceous gastropods. The linear grooves might be associated with commensal worms, while multiple lines of reasoning point towards hydrozoan symbionts in the case of the branched and anastomosing grooves. After the hydrozoan larva settles and the first polyp becomes fixed on the calcareous ostracum at the shell margin, the process of bioclaustration commences when the periostracum surrounds the base of the polyp, which moves towards the external shell surface, while the hydrorhizae develop in the only possible direction: towards the shell growth margin. This enables new polyps to originate at the shell edge by budding, while the bioclaustration of the stolonial hydrorhizae advances. We consider the nature of this symbiotic relationship as mutualism, with the hydrozoan symbiont taking advantage of the host's feeding current or food debris, and the molluscan host profiting from the defensive capability of the hydrozoan's cnidocysts.

Holocene molluscan successions from southeastern Spain (Galera, Andalusia): a palaeoenvironmental framework and a palaeobiogeographic resource of the Granada UNESCO Geopark

ABSTRACTIn Spain, Holocene deposits are widespread, and although they have been extensively investigated by quaternarists for several decades, their malacological content has remained scarcely studied. In the framework of a German–French–Spanish collaboration, alluvial and tufa sequences in the Baza Basin, Andalusia, Spain are analysed with a multidisciplinary approach, including the analysis of the molluscan successions. Holocene fossil molluscs of the studied sequences reveal a rich assemblage of 53 species, among which 33 are terrestrial. Between 10,000 and 9,000 cal. yr BP, the Galera succession indicates strong river dynamics that prevented the establishment of adjacent terrestrial habitats. The Early to Middle Holocene transition reflects the continuity of humid environments. The Middle Holocene fauna reveals a decrease in humidity accompanied by slight evidence of drier habitats in the near periphery of the floodplain/tufa deposits from 5,900 cal. yr BP onwards. Late Holocene deposits (around 3,000 to 300 cal. yr BP) point to dry and open biotopes indicated by the appearance of xero-resistant and mesophilous gastropods. The palaeoenvironmental reconstruction inferred from the malacocenoses allows discussing local to regional responses of the malacofauna to environmental changes and is consistent with past regional environmental and climatic trends identified in southeastern Spain. The fossil record at Galera offers new evidence to question and clarify the modern range of endemic taxa whose distributions are fragmented. By following a ‘conservation paleobiology’ approach, the analysis of the mollusc fossil record at Galera provides (1) baselines to determine the natural variability of ecosystems and their response to environmental changes, (2) data to discuss and clarify species distribution evolution and (3) arguments to support conservation priorities.

Gastropods Colour Patterns in Cassiopids and Naticids from Romualdo Formation, Araripe Basin, Northeast Brazil

The phylum Mollusca includes one of the most beautiful examples of colour patterns in present-day shells. However, they are rare in the fossil record because they demand excellent fossilization. In Brazil, colour patterns in fossil mollusk shells are recorded in gastropods Natica aff. bulbulus White, 1887 from the Riachuelo Formation (Aptian-Albian), Sergipe-Alagoas Basin. This paper presents the first gastropod shells from the Romualdo Formation with colour patterns, visible under natural and UV light, belonging to the families Naticidae and Cassiopidae, collected at Santo Antônio outcrop municipality of Exu, Pernambuco and, Pinheiro and Serra do Mãozinha sites, municipality of Missão Velha and Romualdo site, municipality of Crato, Ceará. Among the cassiopids more than 100 specimens were tested, with 1/3 of them showing a residual colour pattern under UV light exposure, after chemical preparation. They correspond to the species Paraglauconia (Diglauconia) araripensis (Beurlen, 1964), Paraglauconia (Diglauconia) lyrica Maury, 1934, Gymnentome (Gymnentome) carregozica (Maury, 1934) and Gymnentome (Gymnentome) romualdoi Beurlen, 1964. The colour pattern is virtually similar in both genera, with fluorescent stripes on a dark background, showing the taxonomic similarity between them. As for the naticids, about 20 specimens were collected and 15 show good preservation, observing the visible colour pattern under natural light in Natica sp. and Euspira sp.; both new taxa for the Araripe Basin. The residual colour pattern in naticids ranges from spiral stripes to sigmoidal lines and blotches of brown and yellowish tones on a paler background, as observed in fossil species of the same family in the Cenozoic. The new occurrences increase the fossiliferous diversity of mollusks of the Romualdo Formation and extend the understanding of the diversity of colouration patterns of Lower Cretaceous gastropods.