A 3D model of the Middle Jurassic ammonoid Normannites with an apertural modification from Thürnen, Switzerland, was constructed using physical–optical tomography. It tested to determine whether formation affected shell orientation, estimate buoyancy regulation and reconstruct mode life this ammonoid. No drastic postural changes occurred between models that excluded included lappets, suggesting lappets were not formed change syn vivo orientation and, in turn, locomotion. We speculate these...

Molluscs such as ammonoids record their growth in accretionary shells, making them ideal for the study of evolutionary changes ontogeny through time. Standard methods usually focus on two-dimensional data and do not quantify empirical shell chamber volumes ontogeny, which can possibly be important to disentangle phylogeny, interspecific variation palaeobiology these extinct cephalopods. Tomographic computational offer opportunity empirically volumetric major ammonoid sub-clades three...

Abstract Predator–prey relationships are considered a major driver for the evolution of organisms, and thus contributed to shaping morphology, ecology, diversity. During Late Cretaceous North America, ammonoid cephalopods were one most abundant diverse marine invertebrates. Despite frequent reports shell breakage in ammonoids, little is known pertaining frequency, position, size break through stratigraphic succession. In this study, we analyze an extensive collection scaphitid Hoploscaphites...

Owing to their great diversity and abundance, ammonites belemnites represented key elements in Mesozoic food webs. Because of extreme ontogenetic size increase by up three orders magnitude, position the webs likely changed during ontogeny. Here, we reconstruct number eggs laid large adult females these cephalopods discuss developmental shifts ecologic roles. Based on similarities conch morphology, size, habitat suggest that similar niches occupied Cretaceous juvenile were vacated extinction...

Abstract Reconstructing the physiology of extinct organisms is key to understanding mechanisms selective extinction during biotic crises. Soft tissues are rarely preserved and, therefore, a proxy for physiological aspects needed. Here, we examine whether cephalopod conchs yield information about their by assessing how formation chambers respond external stimuli such as environmental changes. We measured chamber volume through ontogeny detect differences in pattern development nautilids,...

Abstract Understanding the mechanism of selective extinction is important in predicting impact anthropogenic environmental changes on current ecosystems. The externally shelled cephalopods at Cretaceous-Paleogene (K-Pg) mass event (ammonoids versus nautiloids) often studied, but its still debated. We investigate differences metabolic rate between these two groups to further explore causes extinction. use a novel proxy—the fraction carbon stable isotope ratio shell material (Cmeta)—to...

Nautilus remains of great interest to palaeontologists after a long history actualistic comparisons and speculations on aspects the palaeoecology fossil cephalopods, which are otherwise impossible assess. Although large amount work has been dedicated ecology, conch geometry volumes shell parts chambers have studied less frequently. In addition, although focus volumetric analyses for ammonites increasing recently with development computed tomographic technology, intraspecific variation...

Tajika, A. & Wani, R. 2011: Intraspecific variation of hatchling size in Late Cretaceous ammonoids from Hokkaido, Japan: implication for planktic duration at early ontogenetic stage. Lethaia, Vol. 44, pp. 287–298. variations the shell dimensions (ammonitella and protoconch diameters) two (earliest Campanian) ammonoid species (Gaudryceras tenuiliratum Hypophylloceras subramosum) Haboro Ikushumbetsu areas, Japan, show no significant difference between these areas that are approximately 110 km...

Abstract Intraspecific variation of organisms is great importance to correctly carry out taxonomic work, which a prerequisite for key disciplines in paleontology such as community paleoecology, biostratigraphy, and biogeography. However, intraspecific rarely studied ectocochleate cephalopods (ammonoids nautiloids), an excessive number taxa was established during the past centuries. Because fossilized suffers from various biases (time averaging taphonomy), extant example needed actualistic...

Recent advancements in tomographic techniques allow for detailed morphological analysis of various organisms, which has proved difficult the past. However, time and cost required post-processing highly resolved data are considerable. Cephalopods an ideal group to study ontogeny using tomography as entire life history is preserved within a conch. Although increasing number studies apply cephalopod conchs, conch measurements needed adequately characterize remains unknown. Therefore, effect...

Nautilid, coleoid and ammonite cephalopods preserving jaws soft tissue remains are moderately common in the extremely fossiliferous Konservat-Lagerstätte of Hadjoula, Haqel Sahel Aalma region, Lebanon. We assume that hundreds cephalopod fossils from this region with soft-tissues lie collections worldwide. Here, we describe two specimens Syrionautilus libanoticus (Cymatoceratidae, Nautilida, Cephalopoda) Cenomanian Hadjoula. Both preserve parts, but only one shows an imprint conch. The...

Abstract Assessing the taxonomic importance of suture line in shelled cephalopods is a key to better understanding diversity this group Earth history. Because fossils are subject taphonomic artifacts, an in-depth knowledge well-preserved modern organisms needed as important reference. Here, we examine morphology all known species Nautilus and Allonautilus . We applied computed tomography geometric morphometrics quantify well conch geometry septal spacing. Results reveal that useful...

Abstract Based on well‐preserved belemnites, the ontogenetic trajectories of septal spacing between succeeding chambers were analysed. In examined species ( Passaloteuthis laevigata , Parapassaloteuthis zieteni and Pseudohasitites longiformis ) that come from Buttenheim, Germany, Lixhausen, France, follow exponentially increasing trends with no decreasing phase crowding during earliest stage. The absence a trend at stage is unique character in contrast those modern cuttlefish ancient...

Modern nautilids ( Nautilus and Allonautilus ) have often been studied by paleontologists to better understand the anatomy ecology of fossil relatives. Because direct observations these animals are difficult, analysis light stable isotopes (C, O) preserved in their shells has employed reveal habitat life history. We aim (1) reconstruct depth macromphalus (2) decipher fraction metabolic carbon its shell analyzing oxygen (δ 18 O, δ 13 C) septa two specimens combination with analyses water...

The Salazac locality (Gard, southeastern France) is renowned for the richness of its cephalopod fauna (especially ammonites) from Mortoniceras fallax Zone (uppermost Albian, Lower Cretaceous). However, most ammonite species have paradoxically been scarcely illustrated up to now. Furthermore, rare assessments taxonomic diversity are presumably inaccurate, as they either result a drastic typological approach or could not benefit recent advances in modern concepts ammonoid intraspecific and...

We document an upper Albian ( Mortoniceras rostratum Zone) cephalopod assemblage from Clansayes (Drôme, south-eastern France). Although fossils are rare in local exposures and the single sampled level, a decade of intensive fossil collecting yielded 290 ammonite 5 nautilid specimens. In total, we describe 1 species 24 (within 17 genera) ammonites, including 13 heteromorphs. Only two these taxa were previously recorded at Clansayes, which demonstrates value this fauna with regard to taxonomy,...

Abstract The magnitude and ontogenetic patterns of intraspecific variation can provide important insights into the evolution development organisms. Understanding organisms is also a key to correctly pursuing studies in major fields palaeontology. However, has been largely overlooked ectocochleate cephalopods, particularly nautilids. Furthermore, little known regarding evolutionary pattern. Here, we present morphological data for Cretaceous nautilid Eutrephoceras dekayi (Morton) modern...

The impact of increasing atmospheric CO

Rhyncholites and Conchorhynchs are the calcitic elements of upper lower jaws cephalopods, respectively. conchorhynchs occur in relatively high abundance widely distributed, with a long geological range, extending from Triassic to Miocene. While rhyncholites common Europe, there only few reports North America. Here, we document 24 specimens 12 Upper Cretaceous Mount Laurel Formation Delaware. The were found isolation and, thus, identifying taxon which belong is difficult. However, nautilid...

Abstract The Aitamir Formation, situated in the Koppeh Dagh Basin northeast of Iran, is known for its well-exposed Albian-to-Cenomanian succession. Although geologists previously documented a number macro- and microfossils, no nautilids had been discovered until now to our knowledge. Here, we present lower Albian middle Cenomanian from first time. This discovery also record Cretaceous Iran. We identified specimens as Eutrephoceras clementianum (d’Orbigny 1840), E . sublaevigatum 1850),...