Controls on gut phosphatisation : the trilobites from the Weeks Formation Lagerstätte (Cambrian; Utah)

Despite being internal organs, digestive structures are frequently preserved in Cambrian Lagerstätten. However, the reasons for their fossilisation and their biological implications remain to be thoroughly explored. This is particularly true with arthropods--typically the most diverse fossilised organisms in Cambrian ecosystems--where digestive structures represent an as-yet underexploited alternative to appendage morphology for inferences on their biology. Here we describe the phosphatised digestive structures of three trilobite species from the Cambrian Weeks Formation Lagerstätte (Utah). Their exquisite, three-dimensional preservation reveals unique details on trilobite internal anatomy, such as the position of the mouth and the absence of a differentiated crop. In addition, the presence of paired pygidial organs of an unknown function is reported for the first time. This exceptional material enables exploration of the relationships between gut phosphatisation and the biology of organisms. Indeed, soft-tissue preservation is unusual in these fossils as it is restricted to the digestive structures, which indicates that the gut played a central role in its own phosphatisation. We hypothesize that the gut provided a microenvironment where special conditions could develop and harboured a source of phosphorus. The fact that gut phosphatization has almost exclusively been observed in arthropods could be explained by their uncommon ability to store ions (including phosphorous) in their digestive tissues. However, in some specimens from the Weeks Formation, the phosphatisation extends to the entire digestive system, suggesting that trilobites might have had some biological particularities not observed in modern arthropods. We speculate that one of them might have been an increased capacity for ion storage in the gut tissues, related to the moulting of their heavily-mineralised carapace

Complete Primate Skeleton from the Middle Eocene of Messel in Germany: Morphology and Paleobiology

The best European locality for complete Eocene mammal skeletons is Grube Messel, near Darmstadt, Germany. Although the site was surrounded by a para-tropical rain forest in the Eocene, primates are remarkably rare there, and only eight fragmentary specimens were known until now. Messel has now yielded a full primate skeleton. The specimen has an unusual history: it was privately collected and sold in two parts, with only the lesser part previously known. The second part, which has just come to light, shows the skeleton to be the most complete primate known in the fossil record.We describe the morphology and investigate the paleobiology of the skeleton. The specimen is described as Darwinius masillae n.gen. n.sp. belonging to the Cercamoniinae. Because the skeleton is lightly crushed and bones cannot be handled individually, imaging studies are of particular importance. Skull radiography shows a host of teeth developing within the juvenile face. Investigation of growth and proportion suggest that the individual was a weaned and independent-feeding female that died in her first year of life, and might have attained a body weight of 650-900 g had she lived to adulthood. She was an agile, nail-bearing, generalized arboreal quadruped living above the floor of the Messel rain forest.Darwinius masillae represents the most complete fossil primate ever found, including both skeleton, soft body outline and contents of the digestive tract. Study of all these features allows a fairly complete reconstruction of life history, locomotion, and diet. Any future study of Eocene-Oligocene primates should benefit from information preserved in the Darwinius holotype. Of particular importance to phylogenetic studies, the absence of a toilet claw and a toothcomb demonstrates that Darwinius masillae is not simply a fossil lemur, but part of a larger group of primates, Adapoidea, representative of the early haplorhine diversification

The anatomy, phylogenetic relationships, and autecology of the carnivorous lizard "Saniwa" feisti Stritzke, 1983 from the Eocene of Messel, Germany

The evolution and interrelationships of carnivorous squamates (mosasaurs, snakes, monitor lizards, Gila Monsters) are a contentious part of reptile systematics and go to the heart of conflict between morphological and molecular data in inferring evolutionary history. One of the best-preserved fossils in this motley grouping is “Saniwa” feisti Stritzke, 1983, represented by complete skeletons from the early-middle Eocene of Messel, Germany. We re-describe it on the basis of superficial examination, stereoradiography, and high-resolution X-ray computed tomography of new and published specimens. The scalation of the lizard is unique, consisting of small, keeled scales on the head (including a row of enlarged medial supraorbitals) and large, rhomboidal, keeled scales (invested by osteoderms) that covered the rest of the body. Two paired longitudinal rows of enlarged scales ran down the neck. The head was laterally compressed and box-shaped due to the presence of a strong canthal-temporal ridge; the limbs and tail were very long. Notable osteological features include: a toothed, strap-like vomer; septomaxilla with a long posterior process; palpebral with a long posterolateral process; a lacrimal boss and a single lacrimal foramen; a well-developed cultriform process of the parabasisphenoid; two hypoglossal (XII) foramina in addition to the vagus; a lack of resorption pits for replacement teeth; and possibly the presence of more than one wave of developing replacement teeth per locus. There are no osteological modifications suggestive of an intramandibular hinge, but postmortem displacement of the angular-prearticular-surangular complex in multiple specimens suggests that there might have been some degree of mobility in the lower jaw based on soft-tissue modifications. Using phylogenetic analyses on a data-set comprising 473 morphological characters and 46 DNA loci, we infer that a monophyletic Palaeovaranidae Georgalis, 2017, including Eosaniwa Haubold, 1977, lies on the stem of Varanidae Merrem, 1820, basal to various Cretaceous Mongolian taxa. We transfer feisti to the new genus Paranecrosaurus n. gen. Analysis of gut contents reveals only the second known specimen of the cryptozoic lizard Cryptolacerta hassiaca Müller, Hipsley, Head, Kardjilov, Hilger, Wuttke & Reisz, 2011, confirming a diet that was at least partly carnivorous; the preservation of the teeth of C. hassiaca suggests that the gastric physiology of Paranecrosaurus feisti (Stritzke, 1983) n. comb. had high acidity but low enzyme activity. Based on the foregoing and linear discriminant function analysis, we reconstruct P. feisti n. comb., as a powerful, widely roaming, faunivorous-carnivorous stem monitor lizard with a sensitive snout. If the molecular phylogeny of anguimorphs is correct, then many of the features shared by Helodermatidae Gray, 1837 and Varanidae must have arisen convergently, partly associated with diet. In that case, a reconciliation of morphological and molecular data would require the discovery of equally primitive fossils on the helodermatid stem.L’évolution et la phylogénie des squamates carnivores (mosasauriens, serpents, lézards monitor, monstres de Gila) font partie du contentieux qui règne dans la systématique des reptiles et sont au cœur du conflit entre données morphologiques et moléculaires, en éclairant l’histoire évolutive de ce groupe. L’un des fossiles les mieux conservés de ce groupement composite est “Sawina” feisti Stritzke, 1983, représenté par des squelettes complets dans l’Eocène inférieur et moyen de Messel, en Allemagne. Nous le redécrivons sur la base d’un examen superficiel, de la stéréoradiographie et de la tomodensitométrie X haute résolution. Son type d’écailles est unique, consistant en de petites écailles carénées sur la tête (incluant une rangée de supraorbitales médianes élargies) et en de larges écailles carénées rhomboïdales (investies par des ostéodermes) qui recouvrent le reste du corps. Deux paires de rangées longitudinales d’écailles élargies descendent le long du cou. La tête est compressée latéralement et en forme de boîte, en raison de la présence d’une crête canthale-temporale ; les membres et la queue sont très longs. Des traits ostéologiques notables consistent en un vomer denté en forme de sangle ; un manchon lacrimal et un foramen lacrimal unique ; un processus ­cultriforme bien développé du parabasisphénoïde ; deux foramens hypoglossaux (XII) en plus du vagus ; une absence de trous de résorption pour les dents de remplacement ; et la présence possible de plus d’une vague de développement de dents de remplacement per locus. Il n’y a pas de modifications osétéologiques suggérant une charnière intra-mandibulaire, mais un déplacement post mortem du complexe angulaire-­préarticulaire-surangulaire chez de nombreux specimens suggère qu’il pourrait y avoir eu un certain degré de mobilité de la mâchoire inférieure, sur la base de modifications du tissu mou. En utilisant des analyses phylogénétiques sur une base de données comportant 473 ­caractères morphologiques et 46 locus DNA, nous déduisons qu’un Palaeovaranidae Georgalis, 2017 monophylétique, incluant Eosawina ­Haubold, 1977, existe sur la tige des Varanidae Merrem, 1820 à la base de nombreux taxons crétacés mongoliens. Nous transférons feisti dans le nouveau genre Paranecrosaurus n. gen. L’analyse de contenus de l’intestin révèle seulement le second spécimen connu du lézard cryptozoïque, Crypto­laceria hassiaca Müller, Hipsley, Head, Kardjilov, Hilger, Wuttke & Reisz, 2011, confirmant une alimentation au moins partiellement carnivore ; la préservation des dents de C. hassiaca suggère que la physiologie gastrique de Paranecrosaurus feisti (Stritzke, 1983) n. comb. ait eu une forte ­acidité, mais une faible activité enzymatique. En nous fondant sur la forme des dents et sur une analyse discriminante linéaire, nous reconstituons P. feisti n. comb. comme étant un lézard monitor puissant, largment errant, de souche faunivore-carnivore et à museau sensible. Si la phylogénie moléculaire des angimorphes est correcte, de nombreux ­caractères partagés par les Helodermatidae Gray, 1837 et les Varanidae doivent être apparus de manière convergente, en partie associés à l’alimentation. Dans ce cas, une réconciliation entre données morphologiques et données moléculaires devrait requérir la découverte de fossiles également primitifs sur la tige des Helmodermatidae

a) Occlusal surface of the last upper deciduous premolar (dP⁴) of the right side seen from its mesiolingual corner. b) Buccal aspect of the right dP₁.

<p>Scale of a and b = 5 mm.—Photo: Senckenberg Forschungsinstitut Frankfurt, Sven Tränkner.</p

Photograph with Scanning Electronic Microscope (SEM) of the yellow structure on the exposed side of the fetus.

<p>Notice the tiny rod-shaped bodies, which correspond in size and morphology with bacteria. Insert: arrow points to the sampling site. Scale = 1 μ.–SEM: Senckenberg Forschungsinstitut Frankfurt, Renate Rabenstein.</p

Identification of the uteroplacenta.

<p>The photograph of the original upper side of the fossil horse was taken before transfer into epoxy resin during preparation. It displays a black shadow (edged in white) covering the fetus. Arrows point to wrinkling structures, which appeared on the external wall of the uterine horn after accidental rupture. Scale = 5 cm. Right upper corner: for orientation, the outline of the uteroplacenta is shown on a micro-x-ray of the whole skeleton of the mare.—Photo: Senckenberg Forschungsinstitut Frankfurt, Sven Tränkner; micro-x-ray: Senckenberg Forschungsinstitut Frankfurt, Jörg Habersetzer.</p

Inferring echolocation in ancient bats

Laryngeal echolocation, used by most living bats to form images of their surroundings and to detect and capture flying prey1,2, is considered to be a key innovation for the evolutionary success of bats2,3, and palaeontologists have long sought osteological correlates of echolocation that can be used to infer the behaviour of fossil bats4,5,6,7. Veselka et al.8 argued that the most reliable trait indicating echolocation capabilities in bats is an articulation between the stylohyal bone (part of the hyoid apparatus that supports the throat and larynx) and the tympanic bone, which forms the floor of the middle ear. They examined the oldest and most primitive known bat, Onychonycteris finneyi (early Eocene, USA4), and argued that it showed evidence of this stylohyal–tympanic articulation, from which they concluded that O. finneyi may have been capable of echolocation. We disagree with their interpretation of key fossil data and instead argue that O. finneyi was probably not an echolocating bat