Three-dimensional Preservation Research Articles

An Exquisitely Preserved Skeleton Representing a Primitive Sturgeon from the Upper Cretaceous Judith River Formation of Montana (Acipenseriformes: Acipenseridae: N. Gen. and Sp.)

A new species of sturgeon (Acipenseridae), †Psammorhynchus longipinnisn. gen. and sp., is described based on a single well-preserved specimen from the Upper Cretaceous Judith River Formation of Montana. Although based on only a single individual, the osteological detail we are able to describe for this species is extensive because of the completeness of the specimen, the relatively three-dimensional preservation, and the soft, loosely consolidated sandstone matrix in which it was contained (allowing some dissection of the specimen to reveal the internal bones of the head region). We prepared the specimen completely out of the matrix, and described the head region in stages of “dissection.” †Psammorhynchus longipinnisis the only fossil sturgeon to date that provides a relatively complete, reliable look at its osteology. Although there have previously been numerous and widespread reports of fossil sturgeons, the material is notoriously fragmentary and poorly preserved, consisting mostly of isolated scutes or pectoral spines (summarized here in an appendix) and it is of very limited use to phylogenetic studies of living sturgeon taxa. The only other described articulated skeleton of a fossil sturgeon is †Protoscaphirhynchus squamosusWilimovsky from the Upper Cretaceous Hell Creek Formation of Montana. That specimen (the only one known for the species) is a badly preserved, very poorly prepared skeleton showing little detail of the head region. It is interesting to note that the only known articulated fossil sturgeon skeletons (†Psammorhynchus longipinnisn. gen. and sp.; †Protoscaphirhynchus squamosusWilimovsky; and a third, yet undescribed specimen) were apparently each independently discovered in the abdominal regions of hadrosaurian dinosaurs (as was the Cretaceous paddlefish †Paleopsephurus wilsoniMacAlpin). Perhaps hadrosaur carcasses provided the right combination of taphonomic factors to protect acipenseriform carcasses from damage in high energy aquatic environments predominantly preferred by sturgeons. In any case, based on known specimens, sediments within hadrosaurs appear to have been the main preservational medium for articulated fossil sturgeon skeletons in North America.†Psammorhynchus longipinnisappears to be the sister taxon to the rest of Acipenseridae based on our preliminary analysis here. We will reevaluate this relationship elsewhere in our (Hilton, Grande, and Bemis) ongoing study of fossil and living Acipenseridae.

Two remarkable Permian petrified forests: correlation, comparison and significance

Abstract Two outstanding Permian petrified forests, those of Chemnitz, in Germany, and northern Tocantins, in Brazil, contribute to the understanding of the composition, peculiarities and dynamics of Early Permian wetland ecosystems. These assemblages represent seasonally influenced, essentially contemporaneous but quite comparable, tree-fern-dominated plant communities in the Northern and Southern Hemispheres. The Chemnitz fossils are embedded in coarse-grained pyroclastics of the Zeisigwald Tuff Horizon (Leukersdorf Formation, Erzgebirge Basin), whereas those of Tocantins occur in different lithofacies of a cyclic alluvial succession (Pedra de Fogo/Motuca formations, Parnaiba Basin). The outstanding three-dimensional preservation of particularly large fossil remains, made possible by siliceous permineralization, provides the opportunity to study the gross morphology, anatomy and internal organization of plant tissues, as well as taphonomical and ecological aspects of late Palaeozoic plants in a way not allowed by other preservational states. Recent studies of newly collected material permit a re-evaluation of the popular reconstructions of Early Permian floras. Various plant-plant and plant-animal interactions add to our understanding of two diverse lowland ecosystems that, irrespective of their different palaeogeographic position and taphonomic modes, show striking similarities.

A new species of Mene (Perciformes: Menidae) from the Paleocene of South America, with notes on paleoenvironment and a brief review of menid fishes

ABSTRACT A new species of menid fish, †Mene purdyi, is described from northwestern Peru. A Paleocene age (late Thanetian) is estimated for the specimen based on biostratigraphic analysis of planktonic foraminifers recovered from the surrounding matrix. Possible explanations for discrepancies between this result and previous interpretations of an Oligocene age are explored. Stable isotopic analysis of foraminifers associated with the fossil allows for general characterization of the thermal profile of the depositional environment. The small temperature gap between distinct depth-ecological foraminifer assemblages inferred from δ18O values indicates a low vertical temperature gradient, possibly reflecting a depositional environment dominated by upwelling. Although incomplete, the three-dimensional preservation of this specimen allows for detailed description of much of the skull, the first two vertebrae and the posttemporals. Numerous characters distinguish the new taxon from previously described menids, the most conspicuous being its exceptionally large size. Comments on the relationships of this new taxon to other menid fishes are premature until the osteology of fossil and living forms are better documented. Extinct species are briefly reviewed in order to facilitate future studies of Menidae. An examination of the distribution of fossil menids reveals that the group was once widespread, demonstrating a circum-global pattern during much of the Tertiary, consistent with the historical Tethys.

NEW CHANCELLORIIDS FROM THE EARLY CAMBRIAN SEKWI FORMATION WITH A COMMENT ON CHANCELLORIID AFFINITIES

Articulated scleritomes of the chancelloriids Archiasterella fletchergryllus new species and Chancelloria cf. eros Walcott, 1920 are described from the Early Cambrian (Branchian) Sekwi Formation, Mackenzie Mountains, Northwest Territories, Canada. Early diagenetic, microbially mediated lithification has resulted in unusual three-dimensional preservation of the body surface, which potentially allows consideration of the evolutionary affinities of these enigmatic organisms. Sclerites are mounted on short stalks of the integument, connected to the undersurface of the central disc, and are external to the body surface.

JURASSIC ISOPOD (MALACOSTRACA: PERACARIDA) FROM RANVILLE, NORMANDY, FRANCE

A single specimen of a likely sphaeromatoid isopod is described from the Upper Bathonian of northern France at Ranville, Normandy. The remarkable three-dimensional preservation consists of only the head and first pereionite, but clearly constitutes a new genus and species, Reboursia ranvillensis.

A PLANT HOPPER (NOGODINIDAE) FROM THE UPPER PALAEOCENE OF ARGENTINA: SYSTEMATICS AND TAPHONOMY

Abstract: A new taxon of plant hopper, Celinapterixini, is erected based on Celinapterix bellissima gen. et sp. nov. from the Upper Palaeocene Maíz Gordo Formation, north-west Argentina. Its phylogenetic relationships within the Fulgoroidea and Nogodinidae are discussed. The Danish Eocene species Hammapterix paucistrata (Henriksen) is transferred to the Nogodinidae and placed in a new genus, Henriksenopterix, based on wing-venation characters. The new plant hopper is an unusual case of articulated preservation from the Maíz Gordo Formation. The palaeoenvironment is interpreted as a carbonate mudflat subenvironment with a low flow of energy, created during a period of contraction of the lacustrine system. The plant hopper is considered to have sunk and been buried in a soupy substrate. Early fossil-diagenesis seems to have occurred over an extended period of time, because although the specimen preserves all original soft-body parts, these occur as an amorphous mass owing to tissue decomposition. The occurrence of three-dimensional preservation suggests the absence of fossil-diagenetic compression; the sediments seem to preserve more-or-less their original thickness.

Preservation of soft tissues in Silurian graptolites from Latvia

The contractile stalks of graptoloid zooids are preserved as organic carbon residues in thecae of the middle Llandovery graptoloid graptolites Rastrites geinitzii and Neolagarograptus? sp. from the Aizpute‐41 core, Latvia. The contractile stalks are surrounded by equant pyrite crystals, resulting in three‐dimensional preservation of the graptolite rhabdosomes, and are associated with sediment of similar composition to, and derived from, the adjacent matrix. Matrix entered the thecae after pyrite crystal growth and filled some of the space left by collapse of the contractile stalks and some intercrystalline cavities; other space is partially infilled by diagenetic minerals. The contractile stalks are parallel‐sided and occupy up to one‐half the metathecal width, which is not inconsistent, assuming post‐mortem shrinkage, with the suggestion that graptoloid zooids filled their thecal tubes in life. The location of the preserved soft tissues, towards the distal ends of the metathecae, is very different from that predicted by decay experiments on the extant pterobranch hemichordate Rhabdopleura; the latter's soft tissues may thus not be a reliable analogue for those of these Silurian graptoloids.

Thermogravimetric and Raman spectroscopic investigations on different coals in comparison to dispersed anthracite found in permineralized tree fern Psaronius sp.

Permineralized samples of the tree fern Psaronius sp. belong to the spectacular discoveries of the Lower Permian Rotliegend ‘Petrified forest of Chemnitz’, one of the most famous palaeontological sites in the world. The cellular tissues of the 280 million years old fossil fern show a delicate three-dimensional preservation by permineralization. Moreover, anatomical detail can be distinguished very well because of the black coloured former cell walls. By means of Raman spectroscopy this fossilised tissue of the adventitious roots is revealed to be carbon which structure seems to correspond to anthracite. The aim of this work is the experimental confirmation of the carbon structure by means of thermogravimetry and Raman spectroscopy on coal samples of different rank, especially anthracite samples from different times and localities. Coal maturation involves the sequence peat–lignite–coal–anthracite-microcrystalline graphite by incresasing the density and specific energy. The loss of in situ moisture (typically up to 200 °C) and volatile organic matter (up to 600 °C) has been acquired by thermogravimetry. The increasing carbon content, density resp. structure results in Raman spectra with typical band shape of the D- and G-peaks. We used these methods to characterise and compare the separated coal samples to the dispersed carbon inclusions in permineralized Psaronius.

Taphonomic Features of a Lower Permian Beached Cephalopod Assemblage from Central Texas

Abstract A taphonomic investigation of a fossil assemblage near Coleman, Texas, U.S.A., has revealed a rarely seen part of the cephalopod taphonomic pathway. The cephalopods occur in a brown shale with a low-diversity, gastropod-dominated fauna that is mixed together with a conifer-seed fern-dominated terrestrial flora. All of the cephalopod shells (n=2000+) are damaged. The brown shale is interpreted as representing a brackish-water or quiet, muddy beach environment, based in part on the delicate three-dimensional preservation of the terrestrial plant debris and the absence of stenohaline benthic marine fauna. Most upper Paleozoic cephalopods (especially ammonoids) are thought to have lived in offshore (middle to outer shelf) environments. The environmental interpretation and the massive damage observed on the cephalopod shells support the interpretation that this cephalopod fauna has been transported from one or more distant offshore biotopes. These cephalopods had shells with positively buoyant conchs ...

Exceptional Fossil Preservation and the Cambrian Explosion

Exceptionally preserved, non-biomineralizing fossils contribute importantly to resolving details of the Cambrian explosion, but little to its overall patterns. Six distinct "types" of exceptional preservation are identified for the terminal Proterozoic-Cambrian interval, each of which is dependent on particular taphonomic circumstances, typically restricted both in space and time. Taphonomic pathways yielding exceptional preservation were particularly variable through the Proterozoic-Cambrian transition, at least in part a consequence of contemporaneous evolutionary innovations. Combined with the reasonably continuous record of "Doushantuo-type preservation," and the fundamentally more robust records of shelly fossils, phytoplankton cysts and trace fossils, these taphonomic perturbations contribute to the documentation of major evolutionary and biogeochemical shifts through the terminal Proterozoic and early Cambrian.Appreciation of the relationship between taphonomic pathway and fossil expression serves as a useful tool for interpreting exceptionally preserved, often problematic, early Cambrian fossils. In shale facies, for example, flattened non-biomineralizing structures typically represent the remains of degradation-resistant acellular and extracellular "tissues" such as chaetae and cuticles, whereas three-dimensional preservation represents labile cellular tissues with a propensity for attracting and precipitating early diagenetic minerals. Such distinction helps to identify the acuticular integument of hyolithids, the chaetae-like nature of Wiwaxia sclerites, the chaetognath-like integument of Amiskwia, the midgut glands of various Burgess Shale arthropods, and the misidentification of deposit-feeding arthropods in the Chengjiang biota. By the same reasoning, putative lobopods in the Sirius Passet biota and putative deuterostomes in the Chengiang biota are better interpreted as arthropods.

The detailed anatomy of Rhamphorhynchus : axial pneumaticity and its implications

Abstract An acid- and transfer-prepared, juvenile Rhamphorhynchus muensteri , despite some fragmentation, is in an excellent state of three-dimensional preservation, exposing exquisite anatomical details hitherto unknown in other pterosaurs. Here we describe the axial pneumatizations of the cervical and anterior dorsal vertebrae and the sternum. The interior of the cervical centra is subdivided into a pair of large camerae, presumably by air sacs entering by large pleurocoels in the sides of the centra. This so-called ‘camerate’ type of pneumatization is hitherto unknown in pterosaurs. Another excavation enters from the ventral side into the base of the neural arch and stretches between the pre- and postzygapophyses. This type of cavity also penetrates from the ventral side into the base of the first few transverse processes of the dorsal vertebrae, although these lack central pleurocoels. The cristospine also has a complex pneumatic foramen. Skeletal pneumaticity is most probably a result of a highly derived pulmonary system, as in extant birds. Morphologically similar pneumatic features are present in most saurischian dinosaurs and it is possible that they are the result of convergence. Because basal members of the various groups, including Triassic pterosaurs, appear to lack skeletal pneumaticity, convergence seems likely, although the stem-ornithodiran parsimoniously possessed a more bird-like than ‘reptile’-like pulmonary system, albeit non-invasive. This points to possible tachymetabolism in these forms, which is in accord with the distribution of other factors such as integumentary structures and bone histology. It is concluded that evolution of this suite of advanced features, surprisingly, was among the earliest events in the ornithodiran lineage soon after it split off from its crocodilian sister-group.

The Fossil Galliform Bird Paraortygoides from the Lower Eocene of the United Kingdom

A new fossil species assigned to the galliform genus Paraortygoides Mayr is described from the Lower Eocene (Ypresian Stage) London Clay Formation of the United Kingdom. Paraortygoides radagasti, n. sp., is referred to the genus on the basis of comparisons with other specimens from the Middle Eocene deposit of Messel (Hessen, Germany). Because of the three-dimensional preservation of this fossil material, P. radagasti contributes new information pertaining to the morphology of the genus Paraortygoides, in particular with regard to the thoracic vertebrae, tarsometatarsus, and toes. This genus, for example, is distinguished from other currently known fossil and extant galliform birds by the presence of deep pneumatic excavations in the lateral sides of the thoracic vertebrae. The results of a preliminary phylogenetic analysis suggest that Paraortygoides is basal within Galliformes (as already proposed by Mayr [2000]); monophyly of the order is supported with Megapodiidae as the basal sister taxon with respect to the Cracidae and Phasianidae. Paraortygoides radagasti is one of the oldest galliform birds described to date; its age and degree of preservation provide a reliable early phylogenetic constraint for the divergence of a basal clade within the order Galliformes.

Underground Vendobionta From Namibia

The late Precambrian fossils from Namibia have generally been regarded as soft‐bodied organisms whose three‐dimensional preservation resulted from smothering in fluidized sand. The sedimentological context of Pteridinium and Namalia within a sandstone bed, however, allows us to distinguish between two taphocoenoses: (1) winnowed, laterally collapsed, current‐transported specimens accumulated as a lag deposit of turbidite‐like flows, and (2) specimens ‘floating’ in the top part of an event bed with their vanes extending upwards to the upper bedding surface. The second taphocoenosis is interpreted as an in situ preserved ‘infaunal’ community. The immobile underground life habit and the bizarre modes of growth of Pteridinium and Namalia do not fit any extinct or modern group of multicellular organisms. Similar statements can be made for Ernietta and Rangea, thus reviving the Vendobionta hypothesis.

Paleoecology of an Exceptionally Preserved Arthropod Fauna from Lake Deposits of the Miocene Barstow Formation, Southern California, U.S.A

Abstract A unique aquatic arthropod Konservat Lagerstatte occurs in lacustrine-derived carbonate concretions within the Miocene Barstow Formation of southern California. Faunal elements are primarily aquatic, salinity-tolerant, autochthonous predaceous diving beetle larvae, fly larvae and pupae, mosquito and thrip larvae, and fairy shrimp. Three-dimensional preservation of soft tissues is via replacement by silica-based minerals as well as calcite, celestite, apatite, and gypsum. The fauna occurs in three beds (each 1–3 m thick) within an approximately 100 m sequence of predominantly microlaminated mudstone deposited in a saline-alkaline lacustrine environment. Faunal composition is consistent between sites and concretion beds, but faunal composition and diversity changed significantly during lake history, corresponding to differences in brine chemistry as well as preservational facies, resulting from the shift toward a more nearshore regime. The changes in lake chemistry and subsequent changes in fauna i...

Signatures of hydrocarbon venting in a Middle Devonian Carbonate Mound (Hollard Mound) at the Hamar Laghdad (Antiatlas, Morocco)

The Middle Devonian Hollard Mud Mound is situated in the eastern Hamar Laghdad, which is a small mountain range in the Tafilalt in SE Morocco. In contrast to the well known Lower Devonian Kess-Kess mounds, the Hollard Mound is of Middle Devonian age. The facies in the core of this mud mound differs from that of the other parts of the mound, and exhibits signatures of ancient hydrocarbon venting. The carbonate phases of the core facies are derived from the oxidation of vent fluids and consist of clotted micrite, a cryptocrystalline carbonate associated with spheres of uncertain origin, and a calcitic rim cement (rim cement B). These vent carbonates show δ13C values in the range of −11 to −20% PDB indicating that some of their carbon is derived from isotopically light hydrocarbons. Fossiliferous micrite has been affected by hydrocarbon venting in the proximity of the vent site, which is indicated by intermediate δ13C values between vent carbonates and not affected sediments. Bivalves occur in dense populations within the core facies. They form autochthonous shell accumulations and are almost exclusively articulated. it is likely that these bivalves were dependent on chemosynthesis similar to their counterparts at modern vents. The vent deposits also exhibit an unusual prasinophyte assemblage, which might have been linked to the specific nutrient availability at the vent site. The ancient vent site is characterized by an enhanced carbonate precipitation and rapid lithification. The latter is corroborated by the three-dimensional preservation of phytoplankton (prasinophytes and acritarchs) and the occurrence of stromatactoid pores. An early phase of carbonate corrosion predating the formation of vent carbonates affected the fossiliferous micrite of the core facies and is thought to be related to a phase of H2S-rich venting.

Three-dimensional preservation of foot movements in Triassic theropod dinosaurs

Dinosaur footprints have been used extensively as biostratigraphic markers, environmental indicators, measures of faunal diversity and evidence of group behaviour1,2,3,4,. Trackways have also been used to estimate locomotor posture, gait and speed6,7,8,9,10,11, but most prints, being shallow impressions of a foot's plantar surface, provide little evidence of the details of limb excursion. Here we describe Late Triassic trackways from East Greenland, made by theropods walking on substrates of different consistency and sinking to variable depths, that preserve three-dimensional records of foot movement. Triassic theropod prints share many features with those of ground-dwelling birds, but also demonstrate significant functional differences in position of the hallux (digit I), foot posture and hindlimb excursion.

Organic membranous skeleton of the Precambrian metazoans from Namibia

Unlike the celebrated Ediacara fossils, those from the roughly coeval localities of the Kuibis Quarzite of Namibia are preserved not as imprints on the sandstone bedding plane, but three-dimensionally, within the rock matrix. The pattern of deformation and the presence of sand in lower parts of the bodies of Ernietta , the most common and typical of those organisms, indicate that their three-dimensional preservation is a result of a density-controlled sinking of sand-filled organic skeletons within hydrated mud layers. Specimens of Ernietta have preserved various stages of migration across the mud beds. Their wall material, as documented by the mode of deformation, was not only flexible, but also elastic, which makes it unlike chitin. The walls thus seem to be proteinaceous, built probably of a collagenous fabric. The Ernietta skeleton was built of series of parallel chambers, which excludes the possibility that these were external body covers. The chambers apparently represent walls of hydraulic skeleton units, resembling the basement membrane of chaetognaths or the notochord sheath of primitive chordates. Such chambers are widespread among the earliest fossil animals represented by fossils preserved in sandstone. The rise and fall of the Ediacaran faunas thus seem to be partially preservational artifacts. The range of its occurrence is a result of two successive evolutionary events: the origin of an internal hydraulic skeleton enclosed by a strong basement membrane, and the appearance of decomposers with abilities to disintegrate such collagenous sheaths.

Three-dimensional preservation of algae and animal embryos in a Neoproterozoic phosphorite

Phosphorites of the late Neoproterozoic (570 ± 20 Myr BP) Doushantuo Formation, southern China, preserve an exceptional record of multicellular life from just before the Ediacaran radiation of macroscopic animals. Abundant thalli with cellular structures preserved in three-dimensional detail show that latest-Proterozoic algae already possessed many of the anatomical and reproductive features seen in the modern marine flora. Embryos preserved in early cleavage stages indicate that the divergence of lineages leading to bilaterians may have occurred well before their macroscopic traces or body fossils appear in the geological record. Discovery of these fossils shows that the early evolution of multicellular organisms is amenable to direct palaeontological inquiry.

Beaks and radulae of Early Carboniferous goniatites

About one hundred goniatite beaks (jaws) and five radulae from the Late Mississippian (Early Carboniferous) of Arkansas wgere studied with light and scanning electron microscopy (SEM). Four beaks were found within the body chamber of the goniatite Girtyoceras. Owing to the three-dimensional preservation, these oldest known beaks could be studied in detail and compared with those in living coleoids. The beaks are univalved, and the lower one is larger than the upper. Each beak consists of an organic outer and inner lamella; only the rostrum is weakly calcified. In the lower beak the outer and inner lamellae are about the same length, but in the upper beak the outer lamella is considerably shorter than the inner lamella. The goniatite beaks resemble those in living coleoids in the relative length of the outer and inner lamellae in the upper beak, which probably indicates similarity in muscle insertion. Concerning the length of the inner and outer lamellae, the lower beak is similar to that in Vampyroteuthis and the pelagic octopod Tremoctopus. Late Mississippian goniatite beaks dealt with here are similar to those of Carboniferous and Permian goniatites in general morphology, but differ from those of Mesozoic ammonoids. In the latter ammonoids, the lower beak has a long outer lamella and a short inner lamella, whereas both lamellae have about equal length in the goniatites. Goniatite radulae remain stable during ammonoid evolution and demonstrate a more or less distinct similarity with those in living coleoids.

Mineralization of soft-bodied invertebrates in a Jurassic metalliferous deposit

The Jurassic marine biota of La Voulte-sur-Rhone, France, is characterized by three-dimensional preservation of soft-bodied animals and their internal organs. In contrast to other soft-bodied fossils, those from La Voulte are preserved in an unusual suite of minerals, dominated by apatite, calcite, gypsum, barite, and pyrite with accessory Cu, Pb, and Zn sulfides. These are thought to be sedimentary in origin. Fossilization occurred rapidly enough to be influenced by tissue composition and involved a diagenetic sequence: apatite → calcite ± gypsum → pyrite ± chalcopyrite → galena. The La Voulte fossils reveal the role of apatite as a “template” for calcification and pyritization in soft-tissue preservation.