Medusa's gaze: Cell traces and fibrils but no collagen in permineralized Jurassic ichthyosaur bone.

Bone is formed by specialized cells whose activity allows bone to grow, change shape, and repair itself. Its composite structure of collagen fibrils and bioapatite nanocrystals gives bone exceptional mechanical strength. Using scanning electron microscopy, we show in fossil ichthyosaurs, 150 to 200 million years old, from the Jurassic of France and the UK, abundant and direct evidence of cellular activity on the fossilized forming, resting, and resorbing surfaces of bone trabeculae, as well as bone fibrils, Sharpey fibers, and cartilage fibers.

The dentition of the Late Jurassic dwarf sauropod from northern Germany: ontogeny, function, and implications for a rhamphotheca-like structure in Sauropoda.

The basal macronarian sauropod is known only from the Late Jurassic of the Langenberg Quarry near Goslar, Lower Saxony, Germany. has been identified as an insular dwarf and shows a clear resemblance to and . This study provides a detailed description of the dentition of based on an array of fossils outstanding in their abundance, variety of preservation, and ontogenetic range.

A new pseudosuchian from the Favret Formation of Nevada reveals that archosauriforms occupied coastal regions globally during the Middle Triassic.

Recent studies suggest that both stem- and crown-group Archosauria encompassed high ecological diversity during their initial Triassic radiation. We describe a new pseudosuchian archosaur, gen. et sp.

The dinosaurs that weren't: osteohistology supports giant ichthyosaur affinity of enigmatic large bone segments from the European Rhaetian.

Very large unidentified elongate and rounded fossil bone segments of uncertain origin recovered from different Rhaetian (Late Triassic) fossil localities across Europe have been puzzling the paleontological community since the second half of the 19th century. Different hypotheses have been proposed regarding the nature of these fossils: (1) giant amphibian bones, (2) dinosaurian or other archosaurian long bone shafts, and (3) giant ichthyosaurian jaw bone segments. We call the latter proposal the 'Giant Ichthyosaur Hypothesis' and test it using bone histology.

Puberty in a Mesozoic reptile.

The histology of bone can be preserved virtually unaltered for hundreds of millions of years in fossils from all environments and all vertebrate taxa, giving rise to the flourishing field of paleohistology. The shafts of long bones are formed by the apposition of periosteal bone tissue, similar to the growth of wood, and preserve, an often cyclical, record of the growth of the individual and events in its life history. One such event is sexual maturation or puberty, during which hormonal changes transform the juvenile into a sexually mature adult.

Plesiosaurs.

In the early 19th century, long before the discovery of the dinosaurs, scientists and the public alike were faced with the realization that strange beasts, wholly extinct, were once populating Earth's ancient oceans. In no small part, this realization was through the discovery of the first plesiosaurs (and ichthyosaurs) along the Dorset coast of England in the seaside town of Lyme Regis. There was this large marine reptile resembling a large sea turtle, but with four evenly shaped flippers and looking as though a large snake had been pulled through its carapace.

Heads or tails first? Evolution of fetal orientation in ichthyosaurs, with a scrutiny of the prevailing hypothesis.

According to a longstanding paradigm, aquatic amniotes, including the Mesozoic marine reptile group Ichthyopterygia, give birth tail-first because head-first birth leads to increased asphyxiation risk of the fetus in the aquatic environment. Here, we draw upon published and original evidence to test two hypotheses: (1) Ichthyosaurs inherited viviparity from a terrestrial ancestor. (2) Asphyxiation risk is the main reason aquatic amniotes give birth tail-first.

Sauropods.

This article begins as many others on sauropods before it: "Sauropod dinosaurs were the largest animals to ever walk the Earth, by far". The largest sauropods were easily four times heavier than the largest land mammals (and the largest other dinosaur species, for that matter). The iconic body plan of sauropods is dominated by their very long neck, in some species exceeding 14 meters in length, provided with a relatively small head (Figure 1).

Bone abnormalities in the middle Anisian marine sauropsids from Winterswijk.

While the occurrence of skeletal pathologies in Middle Triassic marine reptiles has been poorly documented until now, massive accumulations of bone remains from the Germanic Basin provide the opportunities for documentation. Herein, we describe skeletal abnormalities in the Middle Triassic bone material from the Vossenveld Formation of Winterswijk, the Netherlands. The aim of the study is to distinguish in the studied bones pathologies resulting from malady or trauma and taphonomic alterations.

A globally distributed durophagous marine reptile clade supports the rapid recovery of pelagic ecosystems after the Permo-Triassic mass extinction.

Marine ecosystem recovery after the Permo-Triassic mass extinction (PTME) has been extensively studied in the shallow sea, but little is known about the nature of this process in pelagic ecosystems. Omphalosauridae, an enigmatic clade of open-water durophagous marine reptiles, potentially played an important role in the recovery, but their fragmentary fossils and uncertain phylogenetic position have hindered our understanding of their role in the process. Here we report the large basal ichthyosauriform Sclerocormus from the Early Triassic of China that clearly demonstrates an omphalosaurid affinity, allowing for the synonymy of the recently erected Nasorostra with Omphalosauridae.

To be or not to be heavier: The role of dermal bones in the buoyancy of the Late Triassic temnospondyl amphibian Metoposaurus krasiejowensis.

Stereospondyli are a clade of large aquatic temnospondyls known to have evolved a large dermal pectoral girdle. Among the Stereospondyli, metoposaurids in particular possess large interclavicles and clavicles relative to the rest of the postcranial skeleton. Because of the large size of these dermal bones, it was first proposed that they served as ballast during hydrostatic buoyancy control which assisted metoposaurids to live a bottom-dwelling mode of life.

Determination of muscle strength and function in plesiosaur limbs: finite element structural analyses of humerus and femur.

Background: The Plesiosauria (Sauropterygia) are secondary marine diapsids. They are the only tetrapods to have evolved hydrofoil fore- and hindflippers. Once this specialization of locomotion had evolved, it remained essentially unchanged for 135 Ma.

Early Triassic ichthyopterygian fossils from the Russian Far East.

Ichthyopterygia is a major clade of reptiles that colonized the ocean after the end-Permian mass extinction, with the oldest fossil records found in early Spathian substage (late Olenekian, late Early Triassic) strata in the western USA. Here, we describe reptilian remains found in situ in the early Spathian Neocolumbites insignis ammonoid zone of South Primorye in the Russian Far East. Specimen NSM PV 23854 comprises fragmentary axial elements exhibiting a combination of morphological characteristics typical of Ichthyopterygia.

Early giant reveals faster evolution of large body size in ichthyosaurs than in cetaceans.

Body sizes of marine amniotes span six orders of magnitude, yet the factors that governed the evolution of this diversity are largely unknown. High primary production of modern oceans is considered a prerequisite for the emergence of cetacean giants, but that condition cannot explain gigantism in Triassic ichthyosaurs. We describe the new giant ichthyosaur sp.

Chemistry of porphyrins in fossil plants and animals.

Porphyrins are macrocyclic tetrapyrrole derivatives that are widely distributed in nature. They are often complexed with a metal ion located in the center of the ring system and may be modified by various substituents including additional rings, or by ring opening, which leads to a plethora of different functions. Due to their extended conjugated aromatic ring system, porphyrins absorb light in the visible range and therefore show characteristic colors.

Palaeontological evidence reveals convergent evolution of intervertebral joint types in amniotes.

The intervertebral disc (IVD) has long been considered unique to mammals. Palaeohistological sampling of 17 mostly extinct clades across the amniote tree revealed preservation of different intervertebral soft tissue types (cartilage, probable notochord) seen in extant reptiles. The distribution of the fossilised tissues allowed us to infer the soft part anatomy of the joint.

Pentadactyl manus of the Metoposaurus krasiejowensis from the Late Triassic of Poland, the first record of pentadactyly among Temnospondyli.

Temnospondyli are commonly believed to have possessed four digits in the manus and five in the pes. However, actual finds of articulated autopodia are extremely rare. Therefore, an articulated, slightly incomplete forelimb skeleton with preserved manus of Metoposaurus krasiejowensis from the Late Triassic of Poland is important in providing new details about the structure and ossification sequence in the temnospondyl limb.

Bone histology and microanatomy of Edaphosaurus and Dimetrodon (Amniota, Synapsida) vertebrae from the Lower Permian of Texas.

Here we describe the histology and microanatomy of vertebral centra of the iconic pelycosaur-grade synapsids Edaphosaurus boanerges and Dimetrodon spp. Vertebrae from different axial positions and, in the case of Dimetrodon, from different ontogenetic stages were selected. For the histological description, we produced histological petrographic thin sections ground to a thickness of 50-80 μm of the vertebrae in the sagittal and transversal cutting planes.

Hematological convergence between Mesozoic marine reptiles (Sauropterygia) and extant aquatic amniotes elucidates diving adaptations in plesiosaurs.

Plesiosaurs are a prominent group of Mesozoic marine reptiles, belonging to the more inclusive clades Pistosauroidea and Sauropterygia. In the Middle Triassic, the early pistosauroid ancestors of plesiosaurs left their ancestral coastal habitats and increasingly adapted to a life in the open ocean. This ecological shift was accompanied by profound changes in locomotion, sensory ecology and metabolism.

Neck mobility in the Jurassic plesiosaur : finite element analysis as a new approach to understanding the cervical skeleton in fossil vertebrates.

The sauropterygian clade Plesiosauria arose in the Late Triassic and survived to the very end of the Cretaceous. Plesiosauria evolved the greatest species diversity of any marine reptile clade, attaining a global distribution. Plesiosauria consist of two clades, Rhomaleosauridae and Neoplesiosauria.

Humerus osteology, myology, and finite element structure analysis of Cheloniidae.

Adaptation of osteology and myology lead to the formation of hydrofoil foreflippers in Cheloniidae (all recent sea turtles except Dermochelys coriacea) which are used mainly for underwater flight. Recent research shows the biomechanical advantages of a complex system of agonistic and antagonistic tension chords that reduce bending stress in bones. Finite element structure analysis (FESA) of a cheloniid humerus is used to provide a better understanding of morphology and microanatomy and to link these with the main flipper function, underwater flight.

Structure and evolutionary implications of the earliest (Sinemurian, Early Jurassic) dinosaur eggs and eggshells.

One of the fossil record's most puzzling features is the absence of preserved eggs or eggshell for the first third of the known 315 million year history of amniote evolution. Our meagre understanding of the origin and evolution of calcareous eggshell and amniotic eggs in general, is largely based on Middle Jurassic to Late Cretaceous fossils. For dinosaurs, the most parsimonious inference yields a thick, hard shelled egg, so richly represented in the Late Cretaceous fossil record.

Fossilization transforms vertebrate hard tissue proteins into N-heterocyclic polymers.

Vertebrate hard tissues consist of mineral crystallites within a proteinaceous scaffold that normally degrades post-mortem. Here we show, however, that decalcification of Mesozoic hard tissues preserved in oxidative settings releases brownish stained extracellular matrix, cells, blood vessels, and nerve projections. Raman Microspectroscopy shows that these fossil soft tissues are a product of diagenetic transformation to Advanced Glycoxidation and Lipoxidation End Products, a class of N-heterocyclic polymers generated via oxidative crosslinking of proteinaceous scaffolds.

Dinosaurs: Four Legs Good, Two Legs Bad.

The quadrupedal Sauropods - the biggest dinosaurs to walk the Earth - evolved from bipedal ancestors. Two new early sauropodomorphs from South Africa and Argentina indicate that very large, flexed-limbed sauropodomorphs coexisted with early columnar-limbed sauropods for 20 million years.

Fossil eggshell cuticle elucidates dinosaur nesting ecology.

The cuticle layer consisting mainly of lipids and hydroxyapatite (HAp) atop the mineralized avian eggshell is a protective structure that prevents the egg from dehydration and microbial invasions. Previous ornithological studies have revealed that the cuticle layer is also involved in modulating the reflectance of eggshells in addition to pigments (protoporphyrin and biliverdin). Thus, the cuticle layer represents a crucial trait that delivers ecological signals.