Laura J. Cotton

First report of amber with spider webs and microbial inclusions from the earliest Cretaceous ( c . 140 Ma) of Hastings, Sussex

Abstract: Early Cretaceous amber resins with macroscopic inclusions are extremely rare, as are ambers with inclusions from the parent plant. Here, we report earliest Cretaceous amber resins found within alluvial soils of the Ashdown Formation near Hastings in Sussex. In contrast to younger Cretaceous examples, this Hastings amber was arguably deposited shortly before the emergence of the earliest flowering plant communities c. 140 Ma BP. Preliminary studies reveal plentiful organic inclusions, including vascular tissues, tracheid cells and putative resin ducts of the parent coniferous trees. We also report remarkably preserved soil microbes, including structures comparable with actinobacterial colonies, putative fungal or cyanobacterial filaments, and the earliest examples of spider silk webs. The last includes threads that are twisted, paired and coated with sticky fluid droplets, comparable with those of araneoid spider webs studied by us in modern cherry tree resins. Together, these Hastings amber inclusions became entombed within resins that seeped through the charred bark of coniferous trees subjected to severe fire damage, whose logs were then swept onto fluvial wetlands by floods. Embalming resins of this kind may have evolved to combat damage associated with insects, fungi and widespread forest fires.

A new Eocene lineage of reticulate Nummulites (Foraminifera) from Kilwa district, Tanzania; a place for Nummulites ptukhiani?

Reticulate Nummulites are a widespread and distinctive group of Nummulites, frequently used in biostratigraphy, but their evolution is poorly understood. Studies from the Western Tethys suggest they form a single lineage, the Nummulites fabianii lineage, with an increasing proloculus size over time. This has led to their use as one of the diagnostic taxa for larger benthic foraminiferal biostratigraphy. However, outside of this region, additional taxa have been recorded. The most widely discussed example is Nummulites ptukhiani, which was described from Armenia, whose morphology does not fit with the N. fabianii lineage. This raises the question whether reticulate Nummulites are monophyletic, or the result of multiple independent convergent evolutionary lineages. Here we present data from three newly identified populations of Lutetian to Bartonian reticulate Nummulites from the stratigraphically well-constrained Tanzania Drilling Project records, which shed new light on the ancestry of these aberrant forms. These populations are characterized by extremely large proloculi and unusual morphology. We demonstrate that the populations are consistent with an evolutionary lineage that is morphologically distinct but contemporaneous with the N. fabianii lineage of the Tethys. These forms are remarkably similar in external and internal morphology to the Armenian Nummulites ptukhiani. We therefore refer to them as the N. ptukhiani lineage. The existence of a second lineage of reticulate Nummulites indicates that their evolution is more complex than previously thought and raises questions as to whether they evolved from a common ancestor, or independently. It also underlines the importance of carrying out thorough studies of larger benthic foraminifera with independent stratigraphical control from outside of the Tethyan region to more fully understand their evolution and to enable accurate biostratigraphy.

Remarkable preservation of brain tissues in an Early Cretaceous iguanodontian dinosaur

Abstract It has become accepted in recent years that the fossil record can preserve labile tissues. We report here the highly detailed mineralization of soft tissues associated with a naturally occurring brain endocast of an iguanodontian dinosaur found in c. 133 Ma fluvial sediments of the Wealden at Bexhill, Sussex, UK. Moulding of the braincase wall and the mineral replacement of the adjacent brain tissues by phosphates and carbonates allowed the direct examination of petrified brain tissues. Scanning electron microscopy (SEM) imaging and computed tomography (CT) scanning revealed preservation of the tough membranes (meninges) that enveloped and supported the brain proper. Collagen strands of the meningeal layers were preserved in collophane. The blood vessels, also preserved in collophane, were either lined by, or infilled with, microcrystalline siderite. The meninges were preserved in the hindbrain region and exhibit structural similarities with those of living archosaurs. Greater definition of the forebrain (cerebrum) than the hindbrain (cerebellar and medullary regions) is consistent with the anatomical and implied behavioural complexity previously described in iguanodontian-grade ornithopods. However, we caution that the observed proximity of probable cortical layers to the braincase walls probably resulted from the settling of brain tissues against the roof of the braincase after inversion of the skull during decay and burial. Supplementary material: Information regarding associated fossil material, and additional images, can be found at https://doi.org/10.6084/m9.figshare.c.3519984

Three dimensional reconstructions of Nummulites tests reveal complex chamber shapes

Larger benthic foraminifera (LBF) are important and prolific carbonate producers both in modern and ancient shallow tropical seas. During the Paleogene the genus Nummulites was particularly abundant with a global distribution, leading it to be frequently used in biostratigraphy. However, their evolution is poorly understood as classification is Europe-centered and mostly based on external characters and equatorial thin sections. New occurrences from regions outside the northern Tethys which poorly fit in thus reference frame, show that a more rigid framework for the classification of Nummulites is needed. Here we apply micro computed-tomographical scanning, a tool that recently has become available, to visualise 3D chamber shape of Nummulites djokdjokartae and compare these to traditional morphometrical characters. We find that despite the regular shape in equatorial and axial thin section the irregular 3D chamber shape is not predicted by these sections. We argue that 3D reconstructions of Nummulites tests will be a great aid in improving our understanding of lineages within the genus Nummulites, and to elucidate its evolutionary and biogeographical history.

Earliest Cretaceous cocoons or plant seed structures from the Wealden Group, Hastings, UK

Abstract Complete metamorphosis evolved in insects towards the end of the Palaeozoic Era. A wide range of pupation strategies existed and numerous biosedimentary structures associated with these have been described. The fossil record of endogenous materials associated with pupation, e.g. cocoons, is more limited. Here we report six amber-coloured specimens from the earliest Cretaceous of southern England that were tentatively identified on collection as insect cocoons. These were analysed by Fourier transform infrared spectrometry, stereomicroscopy and X-ray microtomography to elucidate their origin. The interpretation of the Fourier transform infrared spectrometry data was inconclusive because the spectra showed some differences from those of amber. A seed pod origin seems likely for at least two of the objects based on their size, shape and the lineations on their surfaces. Three specimens are more cocoon-like based on their overall morphology and a fibrous surface texture. Although plant megaspore membranes have features analogous with these specimens and cannot be ruled out, the similarity to and variability found within insect cocoons, coupled with the range of potential insect architects present at the time of origin, make an insect origin more likely. We review a number of hymenopteran clades whose extant members construct comparable cocoons. The possible cocoons may have been resin-coated to protect the larva inside from predation, or they may have passively come into contact with resin prior to burial. Supplementary material: All TIFF computed tomography slices from the scan, the computed tomography log file, a surface model of the specimen and digital visualizations of both the whole specimen and the perforations are available at https://doi.org/10.6084/m9.figshare.c.3704794

First bryozoan fauna from the Eocene-Oligocene transition in Tanzania

Records of Cenozoic tropical bryozoan faunas are sparse, particularly from Africa. Here we describe a previously unknown bryozoan ‘sand fauna’ from a drill core across the Eocene–Oligocene boundary from a hemipelagic clay succession in Tanzania. Although low in diversity, this well-preserved fauna includes four cheilostome species, all new to science: Heteractis tanzaniensis sp. nov., Bragella pseudofedora gen. et sp. nov., Lacrimula kilwaensis sp. nov. and L. crassa sp. nov. The four species vary in mineralogy, with H. tanzaniensis having an entirely aragonitic skeleton, B. pseudofedora being bimineralic and the two species of Lacrimula calcitic. These species have either free-living ‘lunulitiform’ (H. tanzaniensis) or rooted ‘conescharelliniform’ (B. pseudofedora, L. kilwaensis and L. crassa) colonies adapted to life on a soft, unstable seafloor. The peak occurrence of bryozoans in the core coincides with the Eocene–Oligocene Glacial Maximum (EOGM), characterized by global environmental change from a greenhouse to an icehouse world, sea-level fall, cooling of the oceans and changes in water circulation that may have led to enhanced nutrient levels favourable to bryozoans both in Tanzania and elsewhere. http://zoobank.org/urn:lsid:zoobank.org:pub:6E49FB4A-EB50-4BCE-9D3D-B139CB5D4C5A

TAPHONOMIC SIGNIFICANCE OF A DENSE INFESTATION OF ENSIS AMERICANUS (BINNEY) BY BALANUS CRENATUS BRUGIÈRE, NORTH SEA

ABSTRACT Ensis americanus (Binney) is an alien razor shell living infaunally in the southern North Sea. It is encrusted postmortem by the acorn barnacle Balanus crenatus Brugière. A remarkable shell of E. americanus was found densely infested by a single spatfall of B. crenatus on the inner and outer surfaces of both valves. The ligament was still attached and was pliant when collected, indicating that infestation was soon after death, probably only weeks or months before it was collected. The evidence of this specimen argues strongly against the common received wisdom that borings or encrustations on the inner surfaces of disarticulated fossil bivalves are an indication of a relatively long postmortem residence time on the seafloor.

Earth System Evolution and Early Life

Abstract It has become accepted in recent years that the fossil record can preserve labile tissues. We report here the highly detailed mineralization of soft tissues associated with a naturally occurring brain endocast of an iguanodontian dinosaur found in c. 133 Ma fluvial sediments of the Wealden at Bexhill, Sussex, UK. Moulding of the braincase wall and the mineral replacement of the adjacent brain tissues by phosphates and carbonates allowed the direct examination of petrified brain tissues. Scanning electron microscopy (SEM) imaging and computed tomography (CT) scanning revealed preservation of the tough membranes (meninges) that enveloped and supported the brain proper. Collagen strands of the meningeal layers were preserved in collophane. The blood vessels, also preserved in collophane, were either lined by, or infilled with, microcrystalline siderite. The meninges were preserved in the hindbrain region and exhibit structural similarities with those of living archosaurs. Greater definition of the forebrain (cerebrum) than the hindbrain (cerebellar and medullary regions) is consistent with the anatomical and implied behavioural complexity previously described in iguanodontian-grade ornithopods. However, we caution that the observed proximity of probable cortical layers to the braincase walls probably resulted from the settling of brain tissues against the roof of the braincase after inversion of the skull during decay and burial. Supplementary material: Information regarding associated fossil material, and additional images, can be found at https://doi.org/10.6084/m9.figshare.c.3519984