Cesare Andrea Papazzoni

The middle to late Eocene evolution of nummulitid foraminifer Heterostegina in the Western Tethys

Megalospheric forms of Western Tethyan late Bartonian to late Priabonian involute Heterostegina from numerous localities, marking different ecological conditions, were morphometrically investigated. They belong to three species, H. armenica, H. reticulata, and H. gracilis based on the presence/absence of granulation, on the chamberlet characteristics and on the relative size of proloculus. Within these species a very rapid evolution could be observed in the reduction of the number of operculinid chambers, in the increase of the number of chamberlets and partially in the increase of the proloculus size. This evolution is demonstrated by stratigraphic superpositions in several localities (especially in the Mossano section), and is supported also by the change of co-occurring fossils, starting with the disappearance of large-sized Nummulites, then followed by the appearance of the genus Spiroclypeus and then by the disappearance of orthophragmines of middle Eocene acme. Based on the reduction of operculinid chambers, two chronosubspecies of Heterostegina armenica and seven of H. reticulata are defined biometrically (four of them: H. armenica tigrisensis, H. reticulata tronensis, H. r. hungarica, and H. r. mossanensis are introduced here). This allows to subdivide the Shallow Benthic Zone (SBZ) 18 into three and SBZ 19 into two subzones. The extremely rapid evolution of H. reticulata allows to calibrate larger foraminiferal events around the middle/late Eocene boundary. The extinction of large-sized Nummulites seems to be heterochronous in the late Bartonian in having migrated eastward, while the first appearance of Spiroclypeus is shown to be synchronous at the base of the Priabonian. The middle/upper Eocene (= Bartonian/Priabonian) boundary is to be placed at the base of the Priabona marls in the Mossano section corresponding to the SBZ 18/19 limit, to the first appearance of genus Spiroclypeus, to that of Nummulites fabianii and of Heterostegina reticulata mossanensis. It falls into the upper part of both the P 15 and NP 18 planktic zones. The Western Tethyan Eocene involute Heterostegina became extinct, apparently with no Oligocene successors.

A new genus and subfamily of mosasaurs from the Upper Cretaceous of northern Italy

ABSTRACT A new genus and two new species of mosasaurs are described from five specimens collected during quarrying operations in the ‘Lastame’ lithotype located in the mountains of northern Italy just to the north of Verona (lower Turonian—lower Santonian). These mosasaurs share some anatomical characters with the North American taxon Russellosaurus coheni, but the presence of distinctive features suggests placement into two new species within a new genus (e.g., forked distal tip of suprastapedial process of quadrate; suture between maxilla and premaxilla extends to point above third tooth position [cf. second in Russellosaurus]). We conducted two phylogenetic analyses of the Mosasauroidea (37 ingroup taxa, 131 characters), the first one with equally weighted characters and the second after successive weighting in order to reduce homoplastic noise and amplify the signal in the data. The first analysis (equal weights) resulted in 96 most parsimonious trees, whereas the second produced a single shortest tree. Both analyses consistently placed the new genus as the sister taxon to Russellosaurus, and these two taxa were placed together with Yaguarasaurus, in a clade that is the sister group of the Tethysaurinae (Tethysaurus and Pannoniasaurus). A new clade of mosasaurs, the Yaguarasaurinae, is here defined as comprising the most recent common ancestor of Russellosaurus, Romeosaurus, and Yaguarasaurus, and all of its descendants. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

Deep-water coral banks: an example from the “Calcare di Mendicino” (Upper Miocene, Northern Calabria, Italy)

SummaryThe “Calcare di Mendicino” is a mixed carbonatesiliciclastic informal unit of Miocene (Late Tortonian-Early Messinian age), that crops out extensively in the northwestern part of the Calabria. In the Scannelle quarry near Belsito (Cosenza), four stratigraphic sections were studied to define the sedimentological and paleoecological setting. The carbonate body records the development of a deep-water coral bank characterized by a low-diverse community of azooxanthellate scleractinian (Oculina andDendrophyllia) and stylasterine hydrozoans colonies. Two main stages of bioconstruction development can be distinguished: a thicket and a bank stage. Among the biostromal dwellers the more common are bryozoans, echinoids, benthic foraminifers, gastropods, and bivalves. A higher content of planktonic foraminifers occur in the thicket stage. The coral bank flourished within the aphotic zone, with deep currents loaded with nutrients and siliciclastic sediments.The upper part of the “Calcare di Mendicino” carbonate body has been affected by a pervasive dolomitization destroying almost completely the sedimentary structures and the biofacies. The lower part, the main object of this paper, preserves the microfacies but it experienced a widespread recrystallization obliterating the primary geochemical characteristics. The diagenetic history, partly hidden, reveals three main stages: primary marine with isopachous fibrous cements, deep burial with cavities infilled by sparry calcite, and meteoric-phreatic with dog-tooth cements.

Coralgal buildups associated with the Bolca Fossil-Lagerstätten: new evidence from the Ypresian of Monte Postale (NE Italy)

The Monte Postale and Pesciara di Bolca sites are well-known Eocene Fossil-Lagerstätten. The origin of these deposits has been previously related to a lagoon environment, protected from the open sea by a barrier formed by some kind of reef. However, no detailed description of a bioconstructed system has ever been reported in the area. This study provides the first detailed characterization of the upper Ypresian Monte Postale reef, made of in situ corals, calcareous algae, and encrusting foraminifera. Three main facies associations have been recognized: (1) a coralgal rim, roughly E/W oriented, (2) lagoon deposits in the south and (3) fore-reef sediments towards the north. The coralgal rim is represented by a wave-resistant framework made of heavily calcified organisms associated to Alveolina accumulations; the adaptation of most of these organisms to the euphotic zone promoted their growth in proximity to the sea level, allowing this structure to act as an effective barrier. In particular, during relative sea-level lowstands or highstands, the coralgal rim could have limited the water exchange between the lagoon and the open sea, reducing the oxygenation in the lagoon and allowing the formation of the Fossil-Lagerstätten. During relative sea-level transgressions, the water could have risen well above the margin, establishing normal oxygenation and hampering the fossils’ preservation. The Monte Postale succession represents one of the few examples of lower Eocene bioconstructions. The description of this biotic assemblage provides new data for the characterization of reef communities during a crucial climatic phase, near the end of the early Eocene climatic optimum global warming.

New results on the hydrodynamic behaviour of fossil Nummulites tests from two nummulite banks from the Bartonian and Priabonian of northern Italy.

Settling velocities of 58 well-preserved tests of fossil Nummulites were experimentally determined using a settling tube. The tests were collected from the nummulite banks of Pederiva di Grancona (A forms of N. lyelli and N. striatus, Middle Eocene) and San Germano dei Berici (A and B forms of N. fabianii, Late Eocene), both in the Berici Mts. (Veneto, northern Italy). The data were compared with estimated settling velocities that the same specimens might have had in life conditions. This was done by reconstructing their densities simulating water-filled condition and, to simulate post-diagenetic effects, under calcite-filled condition. These simulations show that A and B forms, even if they greatly diverge in shape, volume and size, still possess comparable settling velocities, and that each nummulite bank is characterized by specific hydrodynamic parameters. The use of settling velocity as a parameter to quantify the hydrodynamic behaviour of particles in seawater enables estimation of palaeoenvironmental conditions such as depth, substrate and the energy scenario. Such information is useful in obtaining further insights into the genesis of nummulite banks, the autochthony or allochthony of which is still being debated. Our results point to an autochthonous interpretation.

INTEGRATING SHALLOW BENTHIC AND CALCAREOUS NANNOFOSSIL ZONES: THE LOWER EOCENE OF THE MONTE POSTALE SECTION (NORTHERN ITALY)

Abstract: The Monte Postale section (Bolca, northern Italy), one of the most famous Lagerstätten of the Eocene, has been investigated to reconstruct the sedimentary succession and to determine both the larger foraminiferal and the calcareous nannofossil biozones. The results allowed us to ascribe the Monte Postale limestones to the Shallow Benthic Zone 11 and to the calcareous nannofossil Zone CNE 5-?6 (= NP 13-?14a). The direct correlation of the SB and CNE Zones is consistent with the current biostratigraphic schemes and allows assignment of the deposition of the succession to the interval between 50.7 and 48.9 Ma, in the late Ypresian (early Eocene). According to the available biostratigraphic data, the uppermost portion of the Monte Postale section should correlate with the Pesciara limestones.

TOWARDS A CALIBRATED LARGER FORAMINIFERA BIOSTRATIGRAPHIC ZONATION: CELEBRATING 18 YEARS OF THE APPLICATION OF SHALLOW BENTHIC ZONES

Abstract: The Shallow Benthic Zonation is one of the most important achievements of biostratigraphy in the last twenty years. Here we summarize the state of the art in the field of Larger Benthic Foraminifera (LBF) and sketch the main lines of research that are improving the precision and usefulness of this scale. The goal of updating the zonation requires a wealth of data coming not only from biostratigraphic investigations but also from paleoenvironmental analyses, biological knowledge, rigorous taxonomic determination, and understanding of paleobiogeography. The papers collected for this special issue are contributions to this broad research program.

A PLIOSAURID TOOTH FROM THE ARGILLE VARICOLORI FORMATION NEAR CASTELVECCHIO DI PRIGNANO (MODENA PROVINCE, NORTHERN ITALY)

The first discovery of a Cretaceous pliosaurid tooth in Italy is reported. It comes from the Cenomanian-lower Campanian Argille Varicolori Formation near Castelvecchio di Prignano (Modena Province, northern Italy). Excepting this new specimen, Italys only reported pliosaurid is a humerus from the Upper Cretaceous of Zavattarello near Pavia. The tooth morphology allows it to be ascribed to Polyptychodon interruptus Owen, 1841, a species only reported thus far from northern-central Europe (England, Germany, and the Czech Republic). This suggests the presence of marine reptile remains in the northern Apennines may have been underestimated.

SHEAR VERSUS SETTLING VELOCITY OF RECENT AND FOSSIL LARGER FORAMINIFERA: NEW INSIGHTS ON NUMMULITE BANKS

Abstract: The genesis of nummulite banks remains a poorly understood topic and the aim of this work is to shed light on it by observing the hydrodynamic behavior of selected larger foraminifera collected from both bank and non-bank deposits. Entrainment and settling velocity of both recent and fossil larger foraminifera were measured using a flume channel and settling tube. Both velocities give information about the reaction of foraminiferal shells to different hydrodynamic conditions affecting their capability to build bank-like sedimentary structures. To assess entrainment, experiments were performed on different substrates to simulate bed load transport on smooth surfaces, fine sand, coarse sand, and bioclastic substrates. Thirty-four recent and 49 fossil shells of foraminifera were used; recent taxa used are Operculina ammonoides, Heterostegina depressa, and Palaeonummulites venosus and fossil taxa used are Nummulites perforatus, N. fabianii, and N. tavertetensis (only A forms were used in this study). Our results seem to differentiate the hydrodynamic behavior of shells collected from banks from those collected from non-bank deposits. The latter possess settling velocities significantly lower than their entrainment velocities, while for taxa collected from nummulite banks, settling velocities are always close to entrainment velocities. Therefore, the relation between hydrodynamics and shape and size may explain why modern larger foraminifera, consistently of smaller size than fossil forms, cannot produce banks and that transport as bed load in moving water was possibly the main trigger for the production of nummulite banks.

Correlation Between Shallow Benthic Zones and Calcareous Plankton Zones at the Bartonian–Priabonian Transition: Preliminary Results from the Varignano Section (Trento Province, Northern Italy)

The Varignano section (Trento province, northern Italy), the sediments of which were deposited in a bathyal palaeoenvironment, contains eight resedimented bioclastic levels with larger foraminifera, thus providing an excellent opportunity to directly correlate the shallow benthic zones (SBZs) with the standard calcareous planktonic zones around the Bartonian–Priabonian transition. Moreover, this section is located only 80 km from the Alano di Piave section (Veneto region), a candidate to host the GSSP of the base of Priabonian, where this direct correlation is hampered by the absence of resedimented levels across the critical interval. The preliminary results of the integrated study of calcareous plankton and larger foraminifera reveal that the extinction of morozovellids and large acarininids (E13–E14 boundary) occurs within SBZ18 and not at the SBZ18–SBZ19 boundary as usually considered.