Growth, age and size of the Jurassic pachycormid Leedsichthys problematicus (Osteichthyes: Actinopterygii)

The Jurassic pachycormid osteichthyan Leedsichthys problematicus is renowned for having been able to achieve prodigious size for a bony fish. Building on work of MARTILL (1986a), a thorough examination of all known material was conducted in order to constrain estimates of the size of this animal and examine its rate of growth. Important specimens of Leedsichthys are described for the first time. The histology of Leedsichthys is reviewed, and the presence of growth annuli is used to establish ages for five specimens. Age and growth data were obtained from gill rakers (n = 4) and lepidotrichia (n = 2). Lepidotrichia show upward curvilinear growth profiles and ages ranging from 21 to 40 annuli, which are assumed to represent years. Both growth profiles start at a small size (0.26 and 0.33 mm radial distance), which is assumed to represent age 1. However, annuli can be lost near the margins of the elements. Gill rakers exhibit a sigmoidal growth profile. Age of gill rakers was estimated by adjusting the alignment of the inflection points of the growth profiles thereby giving adjusted ages. Gill rakers ranged in age from 19–38 annuli, but all show evidence of reabsorption of annuli near the focal points and at the margins of most elements. Sizes for the five individuals range from 8.0-16.5 m for ages of 19-40 years. Growth rate (0.01-0.05 K) was relatively slow as expected for a large, long-lived fish. At age 1, individuals were 1.6 m in length. Estimates for the length of L. problematicus compare well with published lengths of other large suspension feeders such as those for basking and whale sharks

The first definitive Middle Jurassic atoposaurid (Crocodylomorpha, Neosuchia), and a discussion on the genus Theriosuchus

Atoposaurids were a clade of semiaquatic crocodyliforms known from the Late Jurassic to the latest Cretaceous. Tentative remains from Europe, Morocco, and Madagascar may extend their range into the Middle Jurassic. Here we report the first unambiguous Middle Jurassic (late Bajocian–Bathonian) atoposaurid: an anterior dentary from the Isle of Skye, Scotland, UK. A comprehensive review of atoposaurid specimens demonstrates that this dentary can be referred to Theriosuchus based on several derived characters, and differs from the five previously recognized species within this genus. Despite several diagnostic features, we conservatively refer it to Theriosuchus sp., pending the discovery of more complete material. As the oldest known definitively diagnostic atoposaurid, this discovery indicates that the oldest members of this group were small-bodied, had heterodont dentition, and were most likely widespread components of European faunas. Our review of mandibular and dental features in atoposaurids not only allows us to present a revised diagnosis of Theriosuchus, but also reveals a great amount of variability within this genus, and indicates that there are currently five valid species that can be differentiated by unique combinations of dental characteristics. This variability can be included in future broad-scale cladistics analyses of atoposaurids and closely related crocodyliforms, which promise to help untangle the complicated taxonomy and evolutionary history of Atoposauridae

Revealing the Archetype: The Journey of a Trecento Madonna and Child at the National Museum of Scotland

The National Museums Scotland Madonna and Child project sought to uncover and document the history of a fine polychrome wood carving attributed to The Master of the Gualino St Catherine and to prepare it for display. A new body of knowledge has been assembled by the interdisciplinary team. The conservation treatment was informed by this work and led to further discoveries: the removal of overpaint exposing a previously hidden underdrawing. The ethics of the treatment decisions, including the removal of the Christ Child’s 1960s’ fingers required team dialogue and was opened up for the public to respond to in a series of blogs. The discovery of a rich polychromy including gold and glazed tin has led to further plans to produce a 3-D colour reconstruction. The collaborations developed during this project will facilitate future joint ventures for polychrome sculpture in Scottish collections

Chitinozoan biozonation in the upper Katian and Hirnantian of the Welsh Basin, UK

AbstractHere we present a chitinozoan biostratigraphical framework for the South Wales upper Katian and Hirnantian (Ashgill) succession. The current study indicates that three of the six Avalonian Ashgill chitinozoan biozones are recognised in the Welsh Basin; the bergstroemi, fossensis and umbilicata biozones. The Baltoscandian and Laurentian Hercochitina gamachiana biozone is suggested by the presence of Belonechitina cf. gamachiana and the Spinachitina taugourdeaui biozone is suggested by Spinachitina cf. taugourdeaui. Intervening between these is a newly erected lower Hirnantian regional biozone, the Belonechitina llangrannogensis n. sp. biozone. The late Katian (Cautleyan–Rawtheyan) Conochitina rugata biozone was not recognised, though the index taxon is recorded. The presence of B. cf. gamachiana below the lithological expression of the Hirnantian glacial maximum and alongside Rawtheyan graptolite and trilobite assemblages shows that the local base of the B. cf. gamachiana biozone lies beneath the Katian–Hirnantian boundary. Although at present in open nomenclature, the finds of B. cf. gamachiana and S. cf. taugourdeaui, from sites where these chitinozoans co-occur with graptolites, are potentially important; the area offers the potential to study how B. cf. gamachiana and S. cf. taugourdeaui are taxonomically and stratigraphically linked to the original index species. A composite Katian–Hirnantian chitinozoan biozonation for the Welsh Basin is presented and three new species are defined: Belonechitina llangrannogensis n. sp., Belonechitina ceregidionensis n. sp. and Spinachitina penbryniensis n. sp

Ichthyosaurs from the Jurassic of Skye, Scotland

Fossils of Mesozoic vertebrates are rare in Scotland, particularly specimens of marine reptiles such as plesiosaurs and ichthyosaurs. We describe a suite of ichthyosaur fossils from the Early to Middle Jurassic of Skye, which to our knowledge are the first ichthyosaurs from Scotland to be described and figured in detail. These fossils span approximately 30 million years, from the Sinemurian to the Bathonian, and indicate that ichthyosaurs were a major component of Scottish marine faunas during this time. The specimens include isolated teeth that could represent the most northerly known occurrences of the widespread Sinemurian species Ichthyosaurus communis, a characteristic component of the famous Lyme Regis faunas of England, suggesting that such faunas were also present in Scotland during the Early Jurassic. An associated humerus and vertebrae from Toarcian–Bajocian-aged deposits are named as a new genus and species of basal neoichthyosaurian, Dearcmhara shawcrossi. The taxonomic affinities of this taxon, which comes from a critical but poorly sampled interval in the fossil record, suggest that non-ophthalmosaurid neoichthyosaurians dominated European assemblages around the Early–Middle Jurassic boundary, and were later replaced by ophthalmosaurids, whose radiation likely took place outside Europe. Many of these specimens were collected by amateurs and donated to museum collections, a co-operative relationship essential to the preservation of Scotland’s fossil heritage

An unusual small-bodied crocodyliform from the Middle Jurassic of Scotland, UK, and potential evidence for an early diversification of advanced neosuchians

The Middle Jurassic is a poorly sampled time interval for non-pelagic neosuchian crocodyliforms, which obscures our understanding of the origin and early evolution of major clades. Here we report a lower jaw from the Middle Jurassic (Bathonian) Duntulm Formation of the Isle of Skye, Scotland, UK, which consists of an isolated and incomplete left dentary and part of the splenial. Morphologically, the Skye specimen closely resembles the Cretaceous neosuchians Pachycheilosuchus and Pietraroiasuchus, in having a proportionally short mandibular symphysis, shallow dentary alveoli and inferred weakly heterodont dentition. It differs from other crocodyliforms in that the Meckelian canal is dorsoventrally expanded posterior to the mandibular symphysis and drastically constricted at the 7th alveolus. The new specimen, together with the presence of Theriosuchus sp. from the Valtos Formation and indeterminate neosuchians from the Kilmaluag Formation, indicates the presence of a previously unrecognised, diverse crocodyliform fauna in the Middle Jurassic of Skye, and Europe more generally. Small-bodied neosuchians were present, and ecologically and taxonomically diverse, in nearshore environments in the Middle Jurassic of the UK

Polar front shift and atmospheric CO₂ during the glacial maximum of the Early Paleozoic Icehouse

Our new data address the paradox of Late Ordovician glaciation under supposedly high pCO2 (8 to 22× PAL: preindustrial atmospheric level). The paleobiogeographical distribution of chitinozoan (“mixed layer”) marine zooplankton biotopes for the Hirnantian glacial maximum (440 Ma) are reconstructed and compared to those from the Sandbian (460 Ma): They demonstrate a steeper latitudinal temperature gradient and an equatorwards shift of the Polar Front through time from 55°–70° S to ~40° S. These changes are comparable to those during Pleistocene interglacial-glacial cycles. In comparison with the Pleistocene, we hypothesize a significant decline in mean global temperature from the Sandbian to Hirnantian, proportional with a fall in pCO2 from a modeled Sandbian level of ~8× PAL to ~5× PAL during the Hirnantian. Our data suggest that a compression of midlatitudinal biotopes and ecospace in response to the developing glaciation was a likely cause of the end-Ordovician mass extinction