Development and evolution of tooth renewal in neoselachian sharks as a model for transformation in chondrichthyan dentitions

A defining feature of dentitions in modern sharks and rays is the regulated pattern order that generates multiple replacement teeth. These are arranged in labio‐lingual files of replacement teeth that form in sequential time order both along the jaw and within successively initiated teeth in a deep dental lamina. Two distinct adult dentitions have been described: alternate, in which timing of new teeth alternates between two adjacent files, each erupting separately, and the other arranged as single files, where teeth of each file are timed to erupt together, in some taxa facilitating similarly timed teeth to join to form a cutting blade. Both are dependent on spatiotemporally regulated formation of new teeth. The adult Angel shark Squatina (Squalomorphii) exemplifies a single file dentition, but we obtained new data on the developmental order of teeth in the files of Squatina embryos, showing alternate timing of tooth initiation. This was based on micro‐CT scans revealing that the earliest mineralised teeth at the jaw margin and their replacements in file pairs (odd and even jaw positions) alternate in their initiation timing. Along with Squatina, new observations from other squalomorphs such as Hexanchus and Chlamydoselachus, together with representatives of the sister group Galeomorphii, have established that the alternate tooth pattern (initiation time and replacement order) characterises the embryonic dentition of extant sharks; however, this can change in adults. These character states were plotted onto a recent phylogeny, demonstrating that the Squalomorphii show considerable plasticity of dental development. We propose a developmental‐evolutionary model to allow change from the alternate to a single file alignment of replacement teeth. This establishes new dental morphologies in adult sharks from inherited alternate order

Comment on the letter of the Society of Vertebrate Paleontology (SVP) dated April 21, 2020 regarding “Fossils from conflict zones and reproducibility of fossil‑based scientific data”: Myanmar amber

Non peer reviewe

The first skeletal record of the Cretaceous Enigmatic Sawfish genus Ptychotrygon (Chondrichthyes: Batoidea) from the Turonian (Cretaceous) of Morocco

A new fossil batoid (ray) Ptychotrygon rostrispatula sp. nov. is described from five exceptionally well-preserved, three-dimensional skeletal remains from the Turonian (Late Cretaceous) of Morocco. These specimens represent the first known skeletal remains for the genus Ptychotrygon and allow an almost complete description of the genus providing a new insight to its phylogenetic relations and validate its taxonomic status as a member of the Sclerorhynchoidei. Mechanical preparation of the fossil remains revealed a relatively large batoid species (estimated total length beyond 1 meter). Overall morphology resembles that of sclerorhynchoids with a robust hypertrophied rostrum that lacks enlarged rostral denticles with enlarged paddle-like pectoral proximal elements (propterygium, mesopterygium and metapterygium). Never seen before details of the branchial skeleton are presented (large second hypobranchial without anterior process which was probably fused to the basibranchial and no evidence of articulation with other branchial element). To assess the phylogenetic relations of these specimens within the sclerorhynchoids a parsimonious analysis using TNT and PAUP software packages was performed. These analyses included Asflapristis cristadentis that along with Ptychotrygon rostrispatula sp. nov. were used as representatives of Ptychotrygonidae and also includes six other genera of sclerorhynchoids with relatively good skeletal remains. Both analyses recovered two monophyletic groups within sclerorhynchoids: the first contains Ischyrhiza, Onchopristis and Schizorhiza and a second that includes Micropristis, Sclerorhynchus, Libanopristis and Ptychotrygonidae

Design for remanufacturing in China : a case study of electrical and electronic equipment

As global demand for consumer goods continues to rise, the problem of waste electrical and electronic equipment (or e-waste) increases. E-waste is of particular concern to the world’s governments and environmentalists alike, not just because of the sheer quantity that is being produced annually, but also because e-waste often contains both hazardous materials and scarce or valuable materials. Much research is now focused upon how this waste can be treated safely, economically, and in an environmentally sound manner. This paper presents the findings from a literature review and case study research conducted as a small part of the Globally Recoverable and Eco-friendly E-equipment Network with Distributed Information Service Management (GREENet) project. The GREENet project aims to share knowledge and expertise in e-waste treatment across Europe (in this case, the UK) and China. The focus of this particular study was upon ‘design for remanufacture’ and e-waste in China: as a remanufacturing industry begins to emerge, are Chinese original equipment manufacturers (OEMs) prepared to design more remanufacturable products and could electrical and electronic products become a part of this industry? Findings presented in this paper suggest that design for remanufacture could become more relevant to Chinese OEMs in the near future, as environmental legislation becomes increasingly stringent and a government remanufacturing pilot scheme expands. However, findings from case studies of Chinese e-waste recyclers would suggest that electrical and electronic products are not presently highly suited to the remanufacturing process

A parautochthonous shallow marine fauna from the Late Burdigalian (early Ottnangian) of Gurlarn (Lower Bavaria, SE Germany) : Macrofaunal inventory and paleoecology.

International audienc

A parautochthonous shallow marine fauna from the Late Burdigalian (early Ottnangian) of Gurlarn (Lower Bavaria, SE Germany) : Macrofaunal inventory and paleoecology.

International audienc

Palaeoecology and depositional environments of the Tendaguru Beds (Late Jurassic to Early Cretaceous, Tanzania)

The Late Jurassic to Early Cretaceous Tendaguru Beds (Tanzania, East Africa) have been well known for nearly a century for their diverse dinosaur assemblages. Here, we present sedimentological and palaeontological data collected by the German-Tanzanian Tendaguru Expedition 2000 in an attempt to reconstruct the palaeo-ecosystems of the Tendaguru Beds at their type locality. Our reconstructions are based on sedimentological data and on a palaeoecological analysis of macroinvertebrates, microvertebrates, plant fossils and microfossils (ostracods, foraminifera, charophytes, palynomorphs). In addition, we included data from previous expeditions, particularly those on the dinosaur assemblages. The environmental model of the Tendaguru Beds presented herein comprises three broad palaeoenvironmental units in a marginal marine setting: (1) Lagoon-like, shallow marine environments above fair weather wave base and with evidence of tides and storms. These formed behind barriers such as ooid bar and siliciclastic sand bar complexes and were generally subject to minor salinity fluctuations. (2) Extended tidal flats and low-relief coastal plains. These include low-energy, brackish coastal lakes and ponds as well as pools and small fluvial channels of coastal plains in which the large dinosaurs were buried. Since these environments apparently were, at best, poorly vegetated, the main feeding grounds of giant sauropods must have been elsewhere. Presumably, tidal flats and coastal plains were visited by dinosaurs primarily during periods of drought. (3) Vegetated hinterland. Vegetation of this environment can only be inferred indirectly from plant material transported into the other depositional environments. Vegetation was dominated by a diverse conifer flora, which apparently formed part of the food source of large herbivorous sauropods. Evidence from various sources suggests a subtropical to tropical palaeoclimate, characterised by seasonal rainfall alternating with a pronounced dry season during the Late Jurassic. In Early Cretaceous times, sedimentological and palaeontological proxies suggest a climatic shift towards more humid conditions. Die Tendaguru-Schichten von Tansania in Ostafrika (Oberjura bis Unterkreide) sind als Lagerstätte oberjurassischer Dinosaurier seit nahezu einem Jahrhundert weltweit bekannt. Anhand von sedimentologischen und paläontologischen Daten, die während der Deutsch-Tansanischen Tendaguru Expedition 2000 im Typus-Gebiet der Tendaguru-Schichten gewonnen wurden, werden Paläo-Ökosysteme rekonstruiert. Grundlage der Rekonstruktionen sind die Auswertung sedimentologischer Daten sowie die paläo-ökologische Analyse von Makroinvertebraten, Mikrovertebraten, pflanzlichen Fossilien und Mikrofossilien (Ostrakoden, Foraminiferen, Charophyten, Palynomorphen). Darüber hinaus werden Informationen über Dinosaurier berücksichtigt, die bei früheren Expeditionen gewonnen wurden. Das hier vorgestellte Ablagerungsmodell der Tendaguru-Schichten umfaßt drei Teilbereiche eines randlich marinen Sedimentationsraumes, die wie folgt gekennzeichnet werden können: (1) Lagunen-artige, marine Flachwasserbereiche, die oberhalb der Schönwetter-Wellenbasis lagen und unter deutlichem Einfluß von Gezeiten und Stürmen standen. Sie waren vom offenen Meer durch Barrieren, wie Ooidbarren und siliziklastischen Sandbarrenkomplexen, getrennt und wiesen einen leicht schwankenden Salzgehalt auf. (2) Ausgedehnte Wattgebiete und flache Küstenebenen. Dort befanden sich niedrig-energetische, brackische Strandseen und Teiche sowie Tümpel und kleinere Flußrinnen, in denen die großen Dinosaurier eingebettet wurden. Da diese Lebensräume bestenfalls dürftig bewachsen waren, müssen die Nahrungsquellen und der eigentliche Lebensraum der riesigen Sauropoden anderswo gelegen haben. Vermutlich wurden die Wattgebiete und Flachküsten von Dinosauriern vorrangig in den Trockenzeiten aufgesucht. (3) Bewachsenes Hinterland. Die Vegetation dieses Lebensraumes kann nur indirekt aus Pflanzenresten erschlossen werden, die in die anderen Ablagerungsraume transportiert wurden. Die Vegetation wurde von einer diversen Koniferenflora dominiert, die zumindest teilweise die Nahrungsgrundlage der großen, herbivoren Sauropoden bildete. Sedimentologische und paläontologische Indikatoren sprechen für ein subtropisches bis tropisches Klima wahrend der späten Jurazeit mit einem jahreszeitlichen Wechsel von Regenfällen und ausgeprägten Trockenzeiten. In der frühen Kreidezeit deutet sich ein Wechsel zu starker humiden Bedingungen an. doi:10.1002/mmng.20020050103</a