Fossil Gastropods Research Articles

Fossil nutlets of Boraginaceae from the continental Eocene of Hamada of Méridja (southwestern Algeria): The first fossil of the Borage family in Africa.

The Paleogene deposits of the Hamada of Méridja, southwestern Algeria, are currently dated as lower-to-middle Eocene in age based on fossil gastropods and charophytes. Here we report the presence of fruits that can be assigned to the Boraginaceae s.str., apparently representing the first fossil record for this family in Africa, shedding new light on the historical biogeography of this group. Microscopic studies of the fossil nutlets were carried out and compared to extant Boraginaceae nutlets, and to types reported in the literature for this family. The fossils are strikingly similar in general size and morphology, particularly in the finer details of the attachment scar and ornamentation, to nutlets of extant representatives of the Boraginaceae tribe Echiochileae, and especially the genus Ogastemma. We believe that these nutlets represent an extinct member of this lineage. The Ogastemma-like fossils indicate that the Echiochileae, which are most diverse in northern Africa and southwestern Asia, have a long history in this region, dating back to the Eocene. This tribe corresponds to the basal-most clade in Boraginaceae s.str., and the fossils described here agree well with an assumed African origin of the family and the Boraginales I, providing an important additional calibration point for dating the phylogenies of this clade.

Radiocarbon dating of late quaternary sediments using fossil gastropod shells

Radiocarbon dating of late quaternary sediments using fossil gastropod shells

Fossil gastropods from Miocene Lake Randeck Maar and its hinterland (SW Germany)

Fossil gastropods from Miocene Lake Randeck Maar and its hinterland (SW Germany)

EXCEPTIONALLY PRESERVED LATE JURASSIC GASTROPOD EGG CAPSULES

Exceptionally preserved, phosphatized gastropod egg capsules from the uppermost Jurassic (upper Volgian) in Central Russia are reported. The egg capsules were attached to the inner side of the shell wall of empty body chambers of two ammonites. Due to phosphatization, the egg capsules retained their original morphology preserving both the lower attachment base and upper hemispherical cover. Comparison with recent and fossil gastropod egg capsules indicates that these were not produced by neritimorphs, the egg capsules of which are known from the Lower Jurassic and Upper Cretaceous. Since these fossil egg capsules share many similarities with those produced by some recent rissoids and muricid neogastropods, it is evident that they were produced by some representatives of Caenogastropoda. The abundant filamentous microbial structures, as well as micron-sized apatite globules, preserved inside the egg capsules suggest that phosphatization processes were mediated by microbial consortia under anaerobic and low-pH conditions.

A Terrestrial Gastropod Community from the Early Pliocene (Neogene) of Mendoza, Argentina, with Description of a New Species ofRadiodiscusPilsbry and Ferriss, 1906 (Mollusca: Pulmonata: Charopidae)

Numerous fossil gastropods have been recorded in an edaphic level of the middle section of the the Aisol Formation (Mendoza Province, Argentina). This stratigraphic section bears an association of fossil mammals suggesting an early Pliocene age (possible Montehermosan SALMA). Up to four taxa of gastropods have been identified, belonging in Succinea Draparnaud (Succineidae), Gastrocopta Wollaston (Vertiginidae), Bostryx Troschel (Bulimulidae), and a new species of Radiodiscus Pilsbry and Ferriss (Charopidae). The fossil record of terrestrial pulmonate mollusks in Argentina is scarce and mainly restricted to the Quaternary. Thus, the record of these taxa is of paramount importance because it constitutes the oldest record of Gastrocopta and Succinea in Argentina, the first record of Bostryx in Mendoza Province, and the first record of the family Charopidae (Radiodiscus sanrafaelensis nov. sp.) in Pliocene deposits of Argentina.

Peeling out predation intensity in the fossil record: A test of repair scar frequency as a suitable proxy for predation pressure along a modern predation gradient

Predation represents a major cause of death within marine ecosystems, acting as a major agent of natural selection and evolution. Crushing predation in particular is important, as increasing intensity of durophagy through the Phanerozoic has been argued to influence evolution. Repair frequency (RF) is a common palaeoecological metric used to infer crushing predation pressure within the fossil record, yet whether repair frequency variation accurately represents attack frequency or predator success remains uncertain. To determine if repair frequency variation tracks attack frequency or predator success, repair scar frequency for eight, modern intertidal populations of the gastropod Chlorostoma funebrale was calculated along an environmental energy gradient in Barkley Sound, Canada. Attack frequency within intertidal settings is thought to decrease with environmental energy, as crab size, abundance, and intertidal foraging time are greater in sheltered settings than in exposed settings. Spearman's rank correlation of C. funebrale repair frequencies along the energy gradient produced a strong inverse correlation (p≪0.0001) regardless of metric used. These results suggest that repair frequency within crab–gastropod systems serves as a proxy for predator attack frequency. Therefore, the inferences of predation pressure between morphologically similar fossil gastropod populations drawn from repair frequency data are likely accurate.

Larval ecology and morphology in fossil gastropods

AbstractThe shell of marine gastropods conserves and reflects early ontogeny, including embryonic and larval stages, to a high degree when compared with other marine invertebrates. Planktotrophic larval development is indicated by a small embryonic shell (size is also related to systematic placement) with little yolk followed by a multiwhorled shell formed by a free‐swimming veliger larva. Basal gastropod clades (e.g. Vetigastropoda) lack planktotrophic larval development. The great majority of Late Palaeozoic and Mesozoic ‘derived’ marine gastropods (Neritimorpha, Caenogastropoda and Heterobranchia) with known protoconch had planktotrophic larval development. Dimensions of internal moulds of protoconchs suggest that planktotrophic larval development was largely absent in the Cambrian and evolved at the Cambrian–Ordovician transition, mainly due to increasing benthic predation. The evolution of planktotrophic larval development offered advantages and opportunities such as more effective dispersal, enhanced gene flow between populations and prevention of inbreeding. Early gastropod larval shells were openly coiled and weakly sculptured. During the Mid‐ and Late Palaeozoic, modern tightly coiled larval shells (commonly with strong sculpture) evolved due to increasing predation pressure in the plankton. The presence of numerous Late Palaeozoic and Triassic gastropod species with planktotrophic larval development suggests sufficient primary production although direct evidence for phytoplankton is scarce in this period. Contrary to previous suggestions, it seems unlikely that the end‐Permian mass extinction selected against species with planktotrophic larval development. The molluscan classes with highest species diversity (Gastropoda and Bivalvia) are those which may have planktotrophic larval development. Extremely high diversity in such groups as Caenogastropoda or eulamellibranch bivalves is the result of high phylogenetic activity and is associated with the presence of planktotrophic veliger larvae in many members of these groups, although causality has not been shown yet. A new gastropod species and genus, Anachronistella peterwagneri, is described from the Late Triassic Cassian Formation; it is the first known Triassic gastropod with an openly coiled larval shell.

Fossil gastropods from the Late Paleocene Sepultura Formation, Baja California, Mexico

Fossil gastropods from the Late Paleocene Sepultura Formation, Baja California, Mexico

Phenotypic evolution in a fossil gastropod species lineage: Evidence for adaptive radiation?

Detecting speciation in the fossil record is a particularly challenging matter. Palaeontologists are usually confronted with poor preservation and limited knowledge on the palaeoenvironment. Even in the contrary case of adequate preservation and information, the linkage of pattern to process is often obscured by insufficient temporal resolution. Consequently, reliable documentations of speciation in fossils with discussions on underlying mechanisms are rare. Here we present a well-resolved pattern of morphological evolution in a fossil species lineage of the gastropod Melanopsis in the long-lived Lake Pannon. These developments are related to environmental changes, documented by isotope and stratigraphical data. After a long period of stasis, the ancestral species experiences a phenotypic change expressed as shift and expansion of the morphospace. The appearance of several new phenotypes along with changes in the environment is interpreted as adaptive radiation. Lake-level high stands affect distribution and availability of habitats and, as a result of varied functional demands on shell geometry, the distribution of phenotypes. The ongoing divergence of the morphospace into two branches argues for increasing reproductive isolation, consistent with the model of ecological speciation. In the latest phase, however, progressively unstable conditions restrict availability of niches, allowing survival of one branch only.

Sri Lanka’s Aruwakkalu fossil deposit dates to the Burdigalian Age

Aruwakkalu fossil bed is a part of Sri Lanka’s Jaffna limestone, which underlies the whole of Jaffna Peninsula and extends southwards mostly along the west coast. Previous authors have suggested that Aruwakkalu contains a rich assemblage of vertebrate and invertebrate fossils. We sought to confirm the Burdigalian age of this northwestern Miocene deposit at Aruwakkalu on the basis of the foraminifer Pseudotaberina malabarica, an index fossil of the Burdigalian stage. General and timeline collections were made at seven selected sites and the fossils collected were identified. The study sites contained six sedimentary layers of which, third and sixth from top were fossiliferous. The sixth (deepest) layer was dominated by gastropod fossils while the third was dominated by fossils of giant oysters. Fossils of P. malabarica were recovered both from timeline and general collections. In the timeline collection, samples of this index fossil were recovered only from the gastropod layer, suggesting that P. malabarica existed during the time the gastropod layer was being laid down, thus confirming a Burdigalian age for the latter, and helping to date a substantial portion of the Sri Lankan fossil fauna with confidence. Key words: Pseudotaberina malabarica; foraminifera; index fossil; Miocene; gastropod layer; oyster layer DOI: http://dx.doi.org/10.4038/cjsbs.v40i2.3933 CJSBS 2011; 40(2): 163-174

Radiocarbon ages of terrestrial gastropods extend duration of ice-free conditions at the Two Creeks forest bed, Wisconsin, USA

Analysis of terrestrial gastropods that underlie the late Pleistocene Two Creeks forest bed (~13,800–13,500calyr BP) in eastern Wisconsin, USA provides evidence for a mixed tundra-taiga environment prior to formation of the taiga forest bed. Ten new AMS 14C analyses on terrestrial gastropod shells indicate the mixed tundra-taiga environment persisted from ~14,500 to 13,900calyr BP. The Twocreekan climatic substage, representing ice-free conditions on the shore of Lake Michigan, therefore began near the onset of peak warming conditions during the Bølling–Allerød interstadial and lasted ~1000yr, nearly 600yr longer than previously thought. These results provide important data for understanding the response of continental ice sheets to global climate forcing and demonstrate the potential of using terrestrial gastropod fossils for both environmental reconstruction and age control in late Quaternary sediments.

Taphonomy and palaeoecology of the gastropod fauna from a Late Cretaceous rocky shore, Sweden

A gastropod fauna comprising 17 species, each represented by a limited number of specimens, is described from a Late Cretaceous, late early Campanian rocky shore at Ivö Klack, southern Sweden. The gastropod fauna is associated with the most diverse ancient rocky shore fauna ever found. However, the low gastropod species diversity compared to the faunas of modern rocky shores is ascribed to taphonomic factors, notably dissolution of the aragonitic shells, but the predominance of epifaunal herbivores is indicative of a guild structure similar to that found on modern rocky shores. The presence of drill holes assigned to the ichnospecies Oichnus simplex suggests the former presence of muricid gastropods which have not been found as body fossils. A single drill hole is referred to Oichnus paraboloides and was probably made by a naticid gastropod. The infaunal mode of life of naticids makes preservation of such drill holes difficult, since the majority of infaunal prey such as burrowing bivalves has aragonitic shells which are not preserved. The relatively high number of species in comparison to many other Late Cretaceous rocky shore faunas, offers an opportunity to compare gastropod guild structure at Ivö Klack with modern counterparts, even though taphonomic processes such as mechanical destruction and aragonite dissolution have played an important role in the fossil gastropod assemblage.

Assessing Open-System Behavior of 14C in Terrestrial Gastropod Shells

In order to assess open-system behavior of radiocarbon in fossil gastropod shells, we measured the 14C activity on 10 aliquots of shell material recovered from Illinoian (~190–130 ka) and pre-Illinoian (~800 ka) loess and lacustrine deposits in the Midwestern USA. Eight of the 10 aliquots yielded measurable 14C activities that ranged from 0.25 to 0.53 percent modern carbon (pMC), corresponding to apparent 14C ages between 48.2 and 42.1 ka. This small level of open-system behavior is common in many materials that are used for 14C dating (e.g. charcoal), and typically sets the upper practical limit of the technique. Two aliquots of gastropod shells from the Illinoian-aged Petersburg Silt (Petersburg Section) in central Illinois, USA, however, yielded elevated 14C activities of 1.26 and 1.71 pMC, which correspond to apparent 14C ages of 35.1 and 32.7 ka. Together, these results suggest that while many fossil gastropods shells may not suffer from major (>1%) open-system problems, this is not always the case. We then examined the mineralogy, trace element chemistry, and physical characteristics of a suite of fossil and modern gastropod shells to identify the source of contamination in the Petersburg shells and assess the effectiveness of these screening techniques at identifying samples suitable for 14C dating. Mineralogical (XRD) and trace element analyses were inconclusive, which suggests that these techniques are not suitable for assessing open-system behavior in terrestrial gastropod shells. Analysis with scanning electron microscopy (SEM), however, identified secondary mineralization (calcium carbonate) primarily within the inner whorls of the Petersburg shells. This indicates that SEM examination, or possibly standard microscope examination, of the interior of gastropod shells should be used when selecting fossil gastropod shells for 14C dating.

Discovery of Paleogene Sporopollen from the Matrix Strata of the Naij Tal Group-Complex in the Eastern Kunlun Orogenic Belt

The Naij Tal Group-complex is a suite of tectonic-sedimentary melange aggregation of the Eastern Kunlun orogenic belt, which is composed of two parts, i.e. the exotic blocks of various ages and the matrix strata. On the basis of coral, brachiopod and gastropod fossils found in the exotic blocks, the age of this group-complex was once defined to the Late Ordovician or the Paleozoic. This paper reports for the first time 44 genera and 31 species of Mid-Late Oligocene sporopollen in samples from the matrix strata in this group-complex and the Paleogene Quercoidites-Persicarioipollis assemblage is named. The paper aims to provide some detailed evidence for determining the age of the matrix strata in this group-complex based upon a study at the Caiyuanzigou section, which would be of great geological significance for further understanding this group-complex as a suite of tectonic-sedimentary melange aggregation. The new finding will certainly benefit from now on the investigation of formation and evolution mechanism for the Eastern Kunlun orogenic belt.

Fossil hunting in the Neolithic: Shells from the Taurus Mountains at Çatalhöyük, Turkey

AbstractThe Neolithic site of Çatalhöyük in Turkey contains thousands of mollusk shells, among them about 200 fossils. About 25 fossil gastropods and bivalvesoriginate in a Miocene fauna from the Mediterranean Tethys province, and are known from several localities in the Taurus Mountains, dating to the Miocene. The rest are scaphopods belonging to two species of Dentalium and dating to the Pliocene. The gastropods and bivalves were likely collected in the Karaman‐Mut Basin at adistance of about 50km from Çatalhöyük, while the scaphopods were brought from the Hatay Basin. Most of the fossil mollusks at the site were discovered in the upper phases, that is, late in the Pre‐Pottery Neolithic B sequence, and are associated with feasting activities. They may have been collected and brought to the site by the inhabitants as part of transhumance activities, or by visitors. © 2010Wiley Periodicals, Inc.

Switching of early ontogeny type, its mechanism, and role in evolution of mollusca

The phenomenon of "switching" of the early ontogeny type (pelagic versus nonpelagic) is considered in the context of the presence of alternative modes of early ontogeny in recent and fossil gastropod mollusks. Possible environmental inducing mechanisms (decrease in salinity and/or water temperature), as well as the role of this phenomenon in the evolution of Gastropoda, are discussed. The concept of a "mesopoikilohaline" zone is introduced; it is interpreted as a biologically important barrier of salinity (presumably about 13-15 per hundred) which plays the key role in suppression of the free-living larval stage during the process of gradual water desalination. The change in strategy of early ontogeny is interpreted as a regulator of the adaptation process and, to some extent, as a speciation mode in Mollusca.

A fossil Potadoma (Gastropoda: Pachychilidae) from Pleistocene central Kalahari fluvio-lacustrine sediments

A shell of the gastropod Potadoma was discovered in fluvio-lacustrine sediments of the Kalahari (Botswana). A late Pleistocene age of the sediments of ca. 46,000 cal. years BP was established by radiocarbon dating. It is the first record of the freshwater genus Potadoma from southern Africa. Modern counterparts as well as other Pleistocene species of Potadoma had been reported elsewhere from (palaeo-) habitats located at least 2,000 km further in the north, e.g., in the Congo Basin. So far it can be only speculated about possible causes for such a disjunct distribution. The discovery of Potadoma and five more fossil gastropods from the same sediments was used to outline palaeolimnological features. Considering the geomorphological setting, the assemblage of fossil gastropods indicates that the nowadays mainly dry Boteti River was permanently flowing through the western Makgadikgadi Pans ca. 46,000 cal. years BP. The existence of such a riverine palaeoenvironment in the pans demonstrates that the so-called Lake Palaeo-Makgadikgadi was comparatively small during that time, not spanning the area of investigation.

Gastropod egg capsules preserved on bivalve shells from the Lower Jurassic (Hettangian) of Poland

Fossil gastropod egg capsules have rarely been reported from the fossil record. This paper describes gastropod egg capsules preserved exclusively on cardiniid bivalves from Lower Jurassic (Hettangian) deltaic deposits of the Holy Cross Mountains area, central Poland. In most instances, only the bases of the egg capsules are preserved as dark outer rings with hollow cavities inside. Some specimens, however, are preserved as dark circular spots or even shallow depressions on the bivalve molds. The general occurrence, morphology, size and composition of the egg capsules as revealed by Energy Dispersive Spectroscopy (EDS) analyses and elemental mapping point to neritimorphs as the most probable producers. The egg capsules are composed primarily of organic matter with some calcium. Recent neritid gastropods possess aragonitic spherules within the egg capsule walls composed of conchiolin or chitin, which strengthen them and increase their chance of fossilization compared to egg capsules of other gastropods. Recent neritids lay their egg capsules on mollusk shells as well. The occurrence of Early Jurassic egg capsules only on redeposited cardiniid bivalve shells may suggest that the shells were the best medium for egg-capsule deposition. The occurrence of egg capsule bases together with dark circular spots, interpreted as compressed unhatched capsules, suggests that these egg capsules either hatched or were deposited at different times in the same place. The Early Jurassic egg capsules were preserved due to the strengthening role of the carbonate phase within the wall and rapid burial coupled with limited bioturbation in deltaic settings. The prodelta-delta front depositional environment, with high rates of sedimentation by rivers and sediment redistribution by wave and current action, was favorable for preserving these fossils.

New stratigraphic markers in the late Pleistocene Palouse loess: novel fossil gastropods, absolute age constraints and non-aeolian facies

Four stratigraphic sections in the southern part of the Columbia Basin preserve a sequence of aeolian and non-aeolian sediments ranging in age from 9AE43 to >47AE0 14 C ka based on accelerator mass spectrometry radiocarbon dating of fossil molluscs, geochemistry of Cascade Mountain-sourced tephra and association with formally recognized pedostratigraphic units (the Washtucna and Old Maid Coulee soils). Study sections are interpreted as representing concurrent deposition of loess and distal Missoula Flood rhythmites in valleys tributary to main drainages backflooded during the Missoula Floods, and formation of carbonate and iron-rich soils. Sediments belong to the formally recognized L-1 and L-2 loess units established for the Palouse loess, which were deposited in the Columbia Basin subsequent to events of glacial outburst flooding. Sediments associated with the Mount Saint Helens set S and set C tephras in the study sections preserve a fauna of five species of gastropod mollusc which have not been reported previously from sediments of late Pleistocene age in the Palouse region. The fossils comprise two distinct faunules stratigraphically separated by the Mount Saint Helens So tephra. Accelerator mass spectrometry radiocarbon dating of the fossils collected above the tephra in two of the sections yielded ages of 12AE48 ± 0AE06 and 9AE43 ± 0AE05 14 C kyr. These ages suggest that independent determinations of the 13AE35 14 C kyr age of the So tephra in other areas where Missoula Flood sediments are preserved are probably accurate, and help to refine the age of the latest events in the most recent sequence of catastrophic glacial outburst flooding.

Palaeoecology of the Pleistocene (MIS 5.5) outcrops of Santa Maria Island (Azores) in a complex oceanic tectonic setting

Santa Maria is the oldest island of the Azores archipelago and the only one that possesses late-Miocene early-Pliocene and Pleistocene fossils. Two Pleistocene outcrops Lagoinhas and Prainha, from the Marine Isotopic Substage 5.5 (MIS 5.5) are known from Santa Maria Island. We studied the palaeoecology of the Lagoinhas fossil assemblages and we also provide detailed lithological sections from both outcrops, allowing for more detailed palaeoecological reconstruction. Ten bulk samples of approximately 1 kg each were collected from the sand facies at Lagoinhas. Most of the gastropod taxa represented in these samples occur on the present Azorean shores, the exceptions being Conus sp., Gibbula cf. umbilicalis, Polynices lacteus and Trachypolia nodulosa, which have locally disappeared from the Azorean malacofauna during the course of the last glaciation. Most of the fossil gastropods were epifaunal and crawlers. About half of them were herbivores, about one quarter was carnivores, and only a few (less than 10%) were detritivores or parasites. The preferred type of substrate was rocky substrate and/or algae. The palaeoecological evidence that results from the analysis of the fossiliferous beds (the bioerosion structures, the coralline algal and mollusc assemblages and their bathymetrical zonation) suggests a marine environment depositional setting from shallow infralittoral (shoreface) to foreshore/beach. A single highstand episode including minor oscillations is apparent during MIS 5.5 in the Azores.