Paleobiological Analyses Research Articles

The recent history of an insular bat population reveals an environmental disequilibrium and conservation concerns

With the global pandemic of Covid-19, the putative threats related to the increasing contact between wild animals, including bats, and human populations have been highlighted. Bats are indeed known to carry several zoonoses, but at the same time, many species are currently facing the risk of extinction. In this context, being able to monitor the evolution of bat populations in the long term and predict future potential contact with humans has important implications for conservation and public health. In this study, we attempt to demonstrate the usefulness of a small-scale paleobiological approach to track the evolution of an insular population of Antillean fruit-eating bats (Brachyphylla cavernarum), known to carry zoonoses, by documenting the temporal evolution of a cave roosting site and its approximately 250 000 individuals bat colony. To do so, we conducted a stratigraphic analysis of the sedimentary infilling of the cave, as well as a taphonomic and paleobiological analysis of the bone contents of the sediment. Additionally, we performed a neotaphonomic study of an assemblage of scats produced by cats that had consumed bats on-site. Our results reveal the effects of human-induced environmental disturbances, as well as conservation policies, on the bat colony. They also demonstrate that the roosting site is currently filling at a very fast pace, which may lead to the displacement of the bat colony and increased contact between bats and human populations in the near future. Our research outcomes advocate for a better consideration of retrospective paleobiological data to address conservation questions related to bat populations.

DeepBryo: A web app for AI‐assisted morphometric characterization of cheilostome bryozoans

AbstractBryozoans are becoming an increasingly popular study system in macroevolutionary, ecological, and paleobiological research. Members of this colonial invertebrate phylum display an exceptional degree of division of labor in the form of specialized modules, which allows for the inference of individual allocation of resources to reproduction, defense, and growth using simple morphometric tools. However, morphometric characterizations of bryozoans are notoriously labored. Here, we introduce DeepBryo, a web application for deep‐learning‐based morphometric characterization of cheilostome bryozoans. DeepBryo is capable of detecting objects belonging to six classes and outputting 14 morphological shape measurements for each object. The users can visualize the predictions, check for errors, and directly filter model outputs on the web browser. DeepBryo was trained and validated on a total of 72,412 structures in six different object classes from images of 109 different families of cheilostome bryozoans. The model shows high (> 0.8) recall and precision for zooid‐level structures. Its misclassification rate is low (~ 4%) and largely concentrated in two object classes. The model's estimated structure‐level area, height, and width measurements are statistically indistinguishable from those obtained via manual annotation. DeepBryo reduces the person‐hours required for characterizing individual colonies to less than 1% of the time required for manual annotation. Our results indicate that DeepBryo enables cost‐, labor,‐ and time‐efficient morphometric characterization of cheilostome bryozoans. DeepBryo can greatly increase the scale of macroevolutionary, ecological, taxonomic, and paleobiological analyses, as well as the accessibility of deep‐learning tools for this emerging model system.

Multi-proxy reconstruction of Holocene paleoenvironments from a sediment core retrieved from the Wadden Sea near Norderney, East Frisia, Germany

The coastal area of the southern North Sea passed through several stages of development during the Holocene starting with swamps and bogs on Pleistocene sands. These were covered due to the rising sea-level by brackish and intertidal sediments with intercalated peat layers indicating repeated shoreline replacements. Such sedimentary archives are excellent sources for environmental reconstructions and potentially suited to deliver a regional sea-level curve. We analysed a 4.6 m-long sediment core recovered south of the island of Norderney (East Frisia, Germany) using a multiproxy approach. The record comprises a vertical stack of changing sedimentary facies, including a basal peat and a second peat layer intercalated between marine sediments, which provides a sedimentological record of local coastal evolution since 7000 cal. BP. High-resolution stratigraphic, geochemical and paleobiological analyses enables reconstructing environmental variability in response to sea-level changes including a short-lived transgressive-regressive cycle. This took place around 6000 cal. BP and lasted only a few hundred years. Our multiproxy approach demonstrates that the combined analyses of geochemical and biological parameters in concert with statistical evaluation are indispensable for the reconstruction of coastal evolution and short-term sea-level fluctuations.

Re-Evaluation of Morphological Characters Questions Current Views of Pinniped Origins

Abstract The origin of pinnipeds has been a contentious issue, with opposite sides debating monophyly or diphyly. This review uses evidence from the fossil record, combined with comparative morphology, molecular and cytogenetic investigations to evaluate the evolutionary history and phylogenetic relationships of living and fossil otarioid and phocoid pinnipeds. Molecular investigations support a monophyletic origin of pinnipeds, but disregard vital morphological data. Likewise, morphological studies support diphyly, but overlook molecular analyses. This review will demonstrate that a monophyletic origin of pinnipeds should not be completely accepted, as is the current ideology, and a diphyletic origin remains viable due to morphological and paleobiological analyses. Critical examination of certain characters, used by supporters of pinniped monophyly, reveals different polarities, variability, or simply convergence. The paleontological record and our morphological analysis of important characters supports a diphyletic origin of pinnipeds, with otarioids likely arising in the North Pacific from large, bear-like animals and phocids arising in the North Atlantic from smaller, otter-like ancestors. Although members of both groups are known by Late Oligocene time, each developed and invaded the aquatic environment separately from their much earlier, common arctoid ancestor. Therefore, we treat the superfamily Otarioidea as being monophyletic, including the families Enaliarctidae, Otariidae (fur seals/sea lions), Desmatophocidae, and Odobenidae (walruses and extinct relatives), and the superfamily Phocoidea as monophyletic, including only the family Phocidae, with four subfamilies (Devinophocinae, Phocinae, Monachinae, and Cystophorinae).

Surface Model and Tomographic Archive of Fossil Primate and Other Mammal Holotype and Paratype Specimens of the Ditsong National Museum of Natural History, Pretoria, South Africa.

Nearly a century of paleontological excavation and analysis from the cave deposits of the Cradle of Humankind UNESCO World Heritage Site in northeastern South Africa underlies much of our understanding of the evolutionary history of hominins, other primates and other mammal lineages in the late Pliocene and early Pleistocene of Africa. As one of few designated fossil repositories, the Plio-Pleistocene Palaeontology Section of the Ditsong National Museum of Natural History (DNMNH; the former Transvaal Museum) curates much of the mammalian faunas recovered from the fossil-rich deposits of major South African hominin-bearing localities, including the holotype and paratype specimens of many primate, carnivore, and other mammal species (Orders Primates, Carnivora, Artiodactyla, Eulipotyphla, Hyracoidea, Lagomorpha, Perissodactyla, and Proboscidea). Here we describe an open-access digital archive of high-resolution, full-color three-dimensional (3D) surface meshes of all 89 non-hominin holotype, paratype and significant mammalian specimens curated in the Plio-Pleistocene Section vault. Surface meshes were generated using a commercial surface scanner (Artec Spider, Artec Group, Luxembourg), are provided in formats that can be opened in both open-source and commercial software, and can be readily downloaded either via an online data repository (MorphoSource) or via direct request from the DNMNH. In addition to providing surface meshes for each specimen, we also provide tomographic data (both computerized tomography [CT] and microfocus [microCT]) for a subset of these fossil specimens. This archive of the DNMNH Plio-Pleistocene collections represents the first research-quality 3D datasets of African mammal fossils to be made openly available. This simultaneously provides the paleontological community with essential baseline information (e.g., updated listing and 3D record of specimens in their current state of preservation) and serves as a single resource of high-resolution digital data that improves collections accessibility, reduces unnecessary duplication of efforts by researchers, and encourages ongoing imaging-based paleobiological research across a range of South African non-hominin fossil faunas. Because the types, paratypes, and key specimens include globally-distributed mammal taxa, this digital archive not only provides 3D morphological data on taxa fundamental to Neogene and Quaternary South African palaeontology, but also lineages critical to research on African, other Old World, and New World paleocommunities. With such a broader impact of the DNMNH 3D data, we hope that establishing open access to this digital archive will encourage other researchers and institutions to provide similar resources that increase accessibility to paleontological collections and support advanced paleobiological analyses.

Cladocera remains from sediments of Kilometrovoe and Kotovo lakes, Kharbey system (Bolshezemelskaya tundra)

The results of the paleobiological analyses of the Cladocera community of the Kilometrovoe and Kotovo lakes from Kharbey lakes' system (Bolshezemel'skaya tundra) are presented in our work. The dominant species, zoogeography and biotopic attachments are identified. The comparative analysis of the modern structure of the Cladocera from the lakes of the Kharbey system with remains of Cladocera from bental sediments is carried out.

Another Approach to our Knowledge of Early Neogene South American Biomes

Charles Darwin, the English naturalist and father of evolutionary theory, was the first scientist to have dealt with fossils from the Santa Cruz Formation of Argentine Patagonia. However, our understanding of the history of the early Miocene continental vertebrates from Santa Cruz Province is closely tied to two sustained collaborative efforts separated by more than a century. The first occurred near the end of the 19th century between two pioneering giants of Argentine paleontology, the Ameghino brothers, Florentino the biologist and Carlos the geologist; and the second has been unfolding over the last decade and a half between colleagues from Duke University (USA) and the Museo de La Plata (Argentina). In addition, the contributions made near the end of the 19 and early part of the 20 centuries by the Princeton University paleontologists J.B. Hatcher in the field and W.B. Scott through comprehensive monographs on fossil vertebrates, form an important intermediate step between the work of the Ameghinos and the Duke University-Museo de La Plata collaboration. The fauna represented by the diverse, abundant, and generally very well-preserved remains of vertebrate mammals recovered from the Santa Cruz is the basis of the early Miocene Santacrucian South American Land Mammal Age (ca. 19–14 Mya). The forests and grasslands present in this area during this period supported the presence of extinct and surviving lineages of mammals, reptiles, and birds. Thus, Sergio F. Vizcaino and M. Susana Bargo, specialists in the paleobiology of South American mammals, and Richard F. Kay, a specialist in South American fossil primates, undertook to spearhead a long-term program that follows and expands upon the trail of Carlos Ameghino in search of Santacrucian fossils under difficult conditions. Their efforts involved the collaboration of numerous international scientists and graduate students, as well as additional staff, from several institutions. Their results have so far included recovery of some 1600 new specimens, including several nearly complete vertebrate skeletons, mainly from the beach deposits of Santa Cruz Province between the Rios Coyle and Gallegos. This wealth of new remains, combined with precise stratigraphic control, has allowed both the revision of numerous taxa based initially on (often) less well-preserved remains of older collections, as well as the opportunity to conduct rigorous paleobiological analyses, including but not limited to ecological interactions and paleoenvironmental conditions. It is this latter discipline that is the main focus of the contribution under review, which probably represents the first overarching, comprehensive, and broad-based set of paleobiological analyses for South American mammals. There is great uniformity among the paleobiological chapters, which results in a high degree of balanced coverage among the different groups treated. This is clearly intentional and the editors are to be commended for implementing a protocol and seeing to it that it was followed. This is a main strength of this book and is, in large part, what distinguishes it from many other texts on paleobiology. This multi-authored book comprises a detailed study involving 43 paleontologists, both students and established researchers, including anthropologists, biologists, and geologists from Argentina and the USA a wonderful example of scientific and international cooperation. From the outset, it is F. Pujos Instituto Argentino de Nivologia Glaciologia y Ciencias Ambientales (IANIGLA), CCT-CONICET-Mendoza, Avda.Ruiz Leal s/n, Parque Gral. San Martin, Mendoza 5500, Argentina

New Middle Palaeolithic Hominin Dental Remains from Qafzeh, Israel

The present report is a description and paleobiological analysis of human dental remains, found during excavations conducted at Qafzeh in Lower Galilee by R. Neuville and M. Stekelis in the 1930s and, later by a team led by B. Vandermeersch during the 1960s and 1970s, never published. To this tooth sample is added an isolated tooth and a small fragment of child jaw, both found during a short season carried out under the auspices of the municipal council of Nazareth in 1996 in order to clean the site. The whole sample was unearthed from Middle Palaeolithic layers which have been previously dated to ca 90-100 ka BP, marine isotope stage 5b-c. The new human remains represent a minimum number of six adult individuals and three children. Evidence of Linear Enamel Hypoplasia is found on two teeth, one of them documenting the fi rst child case reported from the site. The Middle Palaeolithic skeletal record unearthed at Qafzeh represents today the largest early modern human sample from the Levant.

The Generification of the Fossil Record

Many modern paleobiological analyses are conducted at the generic level, a practice predicated on the validity of genera as meaningful proxies for species. Uncritical application of genera in such analyses, however, has led—perhaps inadvertently—to the unjustified reification of genera in an evolutionary context. While the utility of genera as proxies for species in evolutionary studies should be evaluated as an empirical issue, in practice it is increasingly assumed (rather than demonstrated) that genera are suitable proxies for species. This is problematic on both ontological and epistemological grounds. Genera are arbitrarily circumscribed, non-equivalent, often paraphyletic, and sometimes polyphyletic collections of species. They are useful tools for communication but have no theoretical or biological reality of their own and, whether monophyletic or not, cannot themselves operate in the evolutionary process. Attributes considered important for understanding macroevolution—e.g., geographic ranges, niche breadths, and taxon durations—are frequently variable among species within genera and will be inflated at the generic level, especially in species-rich genera. Consequently, the meaning(s) of results attained at the generic level may not “trickle down” in any obvious way that elucidates our understanding of evolution at the species level. Ideally, then, evolutionary studies that are actually about species should be pursued using species-level data rather than proxy data tabulated using genera. Where genera are used, greater critical attention should be focused on the degree to which attributes tabulated at the generic level reflect biological properties and processes at the species level.

Dinosaur Footprints from Northeastern Brazil: Taphonomy and Environmental Setting

The Brazilian Cretaceous basins located at the northeastern region of Brazil present a wide distribution of dinosaur tracks and isolated footprints in many environmental settings: alluvial fans, braided and meandering fluvial floodplains, marginal lake borders and tidal flats. They are mainly theropod and sauropod footprints of Neocomian and Cenomanian ages that are found in Sousa, Uiraúna-Brejo das Freiras, Araripe, Cedro, Malhada Vermelha, Lima Campos and São Luís Basins. The vertebrate ichnofossils are important biogenic sedimentary structures, a picture of the interaction between dinosaur's behavior and the substrate nature, allowing the paleobiological analysis and inferences about the palaeoenvironments.

Time-averaged molluscan death assemblages: Palimpsests of richness, snapshots of abundance

Field tests that compare living communities to associated dead remains are the primary means of estimating the reliability of biological information in the fossil record; such tests also provide insights into the dynamics of skeletal accumulation. Contrary to expectations, molluscan death assemblages capture a strong signal of living species' rank-order abundances. This finding, combined with independent evidence for exponential postmortem destruction of dead cohorts, argues that, although the species richness of a death assemblage may be a time-averaged palimpsest of the habitat (molluscan death assemblages contain, on average, ∼25% more species than any single census of the local live community, after sample-size standardization), species' relative-abundance data from the same assemblage probably constitute a much higher acuity record dominated by the most recent dead cohorts (e.g., from the past few hundred years or so, rather than the several thousand years recorded by the total assemblage and usually taken as the acuity of species-richness information). The pervasive excess species richness of molluscan death assemblages requires further analysis and modeling to discriminate among possible sources. However, time averaging alone cannot be responsible unless rare species (species with low rates of dead-shell production) are collectively more durable (have longer taphonomic half-lives) than abundant species. Species richness and abundance data thus appear to present fundamentally different taphonomic qualities for paleobiological analysis. Relative- abundance information is more snapshot-like and thus taphonomically more straightforward than expected, especially compared to the complex origins of dead-species richness.

Systematic patterns of time-averaging in the terrestrial vertebrate record: A Cretaceous case study

What is the range of time-averaging in the terrestrial vertebrate record? How are time-averaged assemblages distributed within the terrestrial vertebrate record? What are the implications of time-averaging for vertebrate paleobiological analysis?

Eocene echinoids, the Suwannee Strait, and biogeographic taphonomy

Faunal similarity among regions is often used as a means of identifying regions of endemism in fossil faunas. At least two large-scale taphonomic effects can affect apparent faunal similarity: stratigraphic and facies mismatching. In stratigraphic mismatching, an unconformity represents removal of most or all of a complete assemblage zone in one region, and the constituent taxa are mistakenly interpreted as having never inhabited that region. In facies mismatching, environmental differences between two regions (possibly unrecognized) cause the inference of a barrier that never existed. The two types of mismatching can work in concert if a facies was originally represented in a single stratigraphic interval that has been completely removed from one region. Analysis of faunal similarity via multivariate analysis of individual localities, coupled with comparison of the regions as single samples, may indicate mismatching if the results differ significantly.We view these two problems as part of a suite of taphonomic effects that are not evident in paleobiological analyses of smaller geographic scope. First, there is ambiguity in the notion of “barrier,” even when a candidate is obvious. Second, barriers in paleobiogeography are often hidden and must be inferred from their effects rather than observed. Third, stratigraphic and facies mismatching produce effects on regional faunas similar to those produced by barriers. Anyone using barriers to explain faunal disruptions should address these three points.Upper Eocene faunas of central Florida seem taxonomically distinct from those of the remainder of the Gulf Coastal Plain. This has historically been attributed to a known paleogeographic feature, the Suwannee Strait, which acts as a barrier. The amount of dissimilarity of the echinoid faunas is greater than the amount predicted as a result of sampling problems. Comparison of the results of multivariate and whole-region analyses suggests that mismatching of the two faunas, rather than a true barrier, causes the distinction. Principally facies, but also strata are mismatched. Early Late Eocene faunas inhabited terrigenous sands to the north of the strait and carbonate sands to the south and show the highest distinctiveness. Middle Late Eocene faunas inhabited primarily carbonate sands to the south and both carbonate sands and muds to the north. Overall similarity is higher for both local and regional analyses, and the faunas of northern sands are more similar to those of the southern region than to the northern mud faunas. Overall similarity across the strait is highest in the late Late Eocene strata when both regions had carbonate mud and sand facies. The faunas exhibit greater similarity within facies than they do within regions. Upper Late Eocene strata are poorly preserved north of the strait because of post-Eocene erosion.

Analysis of Morphological Data

Taxonomic data analysis has benefited greatly from standardization of systematic and stratigraphic practices. In contrast, the unique features of each group of organisms and the specific nature of many workers' questions have helped make analysis of morphological data relatively less standardized and more idiosyncratic. In addition, paleobiological analysis of morphological data at larger (roughly, suprafamilial) scales seems to have lagged behind analysis, of taxonomic data because of the relative difficulty with which morphological data are collected (both from fossils themselves and from published sources). In this review, I will briefly touch upon some of the areas in which morphological analysis has contributed significantly to our understanding of life's history. Space limitations preclude a thorough treatment of all aspects of morphological analysis, and the decision to omit certain topics, such as functional morphology, is not a reflection of the importance of these fields.

Bootstrapping and the Fossil Record

A new statistical term has been cropping up in the literature of paleobiological analysis: bootstrapping. This term, which refers to a relatively new general-purpose statistical method, has appeared in papers on subjects as diverse as rates of morphological change (Kitchell et al., 1987), patterns of morphological difference (between dextral and sinistral snail shells, for instance; Gould et al., 1985), survivorship analysis (Gilinsky, 1988), mass extinctions (Hubbard and Gilinsky, in press), the shapes of diversity paths (Gilinsky and Bambach, 1986), and periodicity of extinction (Connor, 1986). Some other papers do not explicitly mention the word bootstrapping, but nonetheless use methods that are quite similar (e.g., Raup and Sepkoski, 1984). Jennifer A. Kitchell convened an entire symposium on the subject at the Fourth North American Paleontological Convention in 1986. What is bootstrapping, and why is it being so widely applied in analytical paleobiology?

Spatial resolution in subfossil molluscan remains: Implications for paleobiological analyses

The ability of paleobiologists to draw paleoecological inferences based on spatial faunal variability within a single stratigraphic interval depends ultimately on the spatial resolving power of the fossil record. This paper evaluates the potential spatial resolution of fossil assemblages by examining modern skeletal remains of molluscs on a benthic transect, along which there is a marked decrease in seagrass cover, in Smuggler's Cove, St. Croix, U.S. Virgin Islands. The sampling transect began in a Thalassia-covered area approximately three meters deep, extended into slightly deeper water with lighter seagrass cover, and ended on an open, bioturbated sandy tract at a depth of nearly six meters.Two-way cluster analysis and polar ordination of 37 samples of molluscan remains, taken at 10-meter intervals along the 360-meter transect, reveal patterns of variation that are shown by correlation analyses and consideration of the autecologies of individual species to be related to measured changes in vegetation. There is a transition from dominance primarily by epifaunal gastropods living on seagrass blades to dominance by infaunal, burrowing bivalves as grass cover becomes lighter. Some non-systematic variability exists in faunal distributional patterns within areas where the environment does not vary systematically, but this does not mask the regular faunal transitions related to environmental changes. Correspondence between the dead and live faunas is difficult to ascertain because of the scarcity of live fauna in collected samples.The results suggest that spatial faunal transitions in fossil remains at even the fine scale evaluated in this study are potentially preservable in the fossil record.

Estimating taxonomic diversity, extinction rates, and speciation rates from fossil data using capture-recapture models

Methods currently used to estimate taxonomic extinction probabilities from fossil data generally assume that the probability of encountering a specimen in a particular stratum, given that the taxon was extant in the time period and location represented by the stratum, either equals 1.0 or else is a constant for all strata. Methods used to estimate taxonomic diversity (number of taxa) and speciation rate generally assume that encounter probabilities equal 1.0. We suspect that these assumptions are often false. Capture-recapture models were historically developed for estimation in the face of variable and unknown sampling probabilities. These models can thus be used to estimate parameters of interest from paleobiological data when encounter probabilities are unknown and variable over time. These models also permit estimation of sampling variances, and goodness-of-fit tests are available for assessing the fit of data to most models. Here we describe capture-recapture models which should be useful in paleobiological analyses and discuss the assumptions which underlie them. We illustrate these models with examples and discuss aspects of study design. We conclude that these models should prove useful in paleobiological analyses.

Molluscan Assemblages from the Marine Middle Miocene of South Jutland and their Environments. Vol. I.

This is a study of the fossil record of marine Miocene beds in South Jutland, Denmark. The beds have been defined as the Arnum formation and referred to the middle Miocene Hemmoor stage as known in Northwest Germany. The object of the work is to increase knowledge of the Danish Miocene and to contribute data on the development of the North Sea Basin during Miocene time.The introduction deals with the history of Tertiary stratigraphy in Europe and some related problems. Discrepancies and uncertainties regarding the correlation and dating of beds in the separate basins have been particularly emphasized. It is often possible to trace disagreements to the acceptance of unsound fossil evidence. Therefore it is concluded that the lithologic and fossil records of the individual basins should be known in much greater detail before adequate inferences as to the contemporaneity of particular beds can be made. It is also suggested that guide fossils should only be designated when statistically justified.The chapters on the South Jutland Miocene contain an outline of the geo-graphic distribution of the formations, a lithologic description of the water well sections from which the fossil material was derived, and definitions of the Arnum formation (marine) and the underlying Ribe formation (non-marine). The following formations are now recognized in the Miocene sequence of South Jutland:Gram formation: late Miocene Arnum formation and Ribe formation: middle Miocene Klintinghoved formation: early Miocene.The chapters on paleontology consist of a description of the molluscan fauna of the Arnum formation, a discussion of the environmental relationships of recent mollusca, and a section on biostratigraphy and paleobiology.The description of species follows a rigid pattern. The intention being to include as many pertinent facts as possible while using a minimum of technical terms. The variation of shell properties is illustrated by diagrams in a few species, and in some families genetic features have been particularly discussed. The chapter is terminated by a short review and some conclusions regarding the significance of shell morphology.The chapter on environmental relationships of recent mollusca includes discussion of the effects of inanimate environments on shell morphology and the distribution of mollusca. It is maintained that the reaction of recent mollusca to variations in their environment should be known in greater detail in order to provide a sound basis for biostratigraphic conclusions depending on the evidence of fossil mollusca.A discussion of the commonly adopted correlation procedures initiates the chapters dealing with biostratigraphy and paleobiology. It is shown that the "percentage" method by which faunas are correlated on the basis of percentages of species in common should be regarded with much criticism. New correlation formulae, in which are included the total numbers of species in the faunas involved are suggested. It is shown by these formulae and other evidence that the fauna of the Arnum formation in its entirety is apparently in better agreement with the Reinbek and Hemmoor faunas of Germany than with any other fauna of the North Sea Basin.The paleobiological analysis of the fauna of the Arnum formation is based on: the biology of living species; the actual frequencies of the mollusca in the different drilled sections; and the environmental relationships of recent mollusca. It is inferred that a decrease in salinity took place during deposition of the formation. The faunules of the different fossiliferous levels are shown to be derivatives of one community: the Aporrhais alata - Nassa sp.sp. community which inhabited relatively shallow waters of the middle Miocene North Sea Basin.In conclusion some comments are made on the correlation of the well sections as supported by paleobiology. The Nassa cimbrica and N. Fuchsi zones are defined, and the different elevations of correlated levels in the drilled sections are related to structural displacements.