The last two decades have seen a remarkable increase in the known diversity of basal avialans and their paravian relatives. The lack of resolution in the relationships of these groups combined with attributing the behavior of specialized taxa to the base of Paraves has clouded interpretations of the origin of avialan flight. Here, we describe Hesperornithoides miessleri gen. et sp. nov., a new paravian theropod from the Morrison Formation (Late Jurassic) of Wyoming, USA, represented by a single adult or subadult specimen comprising a partial, well-preserved skull and postcranial skeleton. Limb proportions firmly establish Hesperornithoides as occupying a terrestrial, non-volant lifestyle. Our phylogenetic analysis emphasizes extensive taxonomic sampling and robust character construction, recovering the new taxon most parsimoniously as a troodontid close to Daliansaurus, Xixiasaurus, and Sinusonasus. Multiple alternative paravian topologies have similar degrees of support, but proposals of basal paravian archaeopterygids, avialan microraptorians, and Rahonavis being closer to Pygostylia than archaeopterygids or unenlagiines are strongly rejected. All parsimonious results support the hypothesis that each early paravian clade was plesiomorphically flightless, raising the possibility that avian flight originated as late as the Late Jurassic or Early Cretaceous.

The largest reported ichthyosaurs lived during the Late Triassic (~235–200 million years ago), and isolated, fragmentary bones could be easily mistaken for those of dinosaurs because of their size. We report the discovery of an isolated bone from the lower jaw of a giant ichthyosaur from the latest Triassic of Lilstock, Somerset, UK. It documents that giant ichthyosaurs persisted well into the Rhaetian Stage, and close to the time of the Late Triassic extinction event. This specimen has prompted the reinterpretation of several large, roughly cylindrical bones from the latest Triassic (Rhaetian Stage) Westbury Mudstone Formation from Aust Cliff, Gloucestershire, UK. We argue here that the Aust bones, previously identified as those of dinosaurs or large terrestrial archosaurs, are jaw fragments from giant ichthyosaurs. The Lilstock and Aust specimens might represent the largest ichthyosaurs currently known.

The phylogenetic analysis is largely based on the character list and coding developed by , with a few modifications that are enumerated below.1. We have omitted taxa that were younger than Lower Jurassic and were less than 40% complete on the Fischer et al. ( 2013) matrix. This included Arthropterygius (33% complete), Maiaspondylus (36% complete), Athabascasaurus (35% complete), Chacaicosaurus (26% complete) and Mollesaurus (18% complete). We retained Malawania (27% complete), however, because it was recovered as a sister taxon to Ichthyosaurus by .2. We omitted Ophthalmosaurus natans and Platypterygius hercynicus because the genus was represented by a better known species, O. icenicus and P. australis, respectively. As with the previously mentioned genera, these are more derived forms.3. We used the character list and coding of Fischer et al. ( 2013), but modified seven characters: Character 2 (Fischer et al. 2013, character 7). Extent of nasals relative to anterior process of maxilla, lateral view: maxilla extends anteriorly as far as nasals or further anteriorly (0); nasals extend farther anteriorly than the maxilla (1) Character 11 (Fischer et al. 2013, character 16). Squamosal shape: square or rectangular (0); triangular (1); squamosal absent (2) Character 39 (Fischer et al. 2013, character 48). Radius with anterior notch: present (0); absent (1). Character 40 (Fischer et al. 2013, character 49). Postaxial accessory digits on forefin: absent (0); present (1). Character 44 (Fischer et al. 2013, character 54). Digital bifurcation: absent (0); present (1). Character 46 (Fischer et al. 2013, character 55). Manual digit V: absent (0); present (1). Character 55 (Fischer et al. 2013, character 65). Tibia with anterior notch: present (0); absent (1). These changes required recoding our characters 39, 40, 46 and 55 for all taxa.4. We removed the following characters from Fischer et al. (2013): 1, 2, 6, 31, 32, 51 and 52 for reasons stated in Ji et al. (2016). We also eliminated character 3 because it does not specify where the cross section is taken and character 4 as it depends on preservation and how much of the root is exposed. Also, both characters are not always exposed in laterally compressed specimens of Lower Jurassic ichthyosaurs. Both 44 and 45 were removed because they were unclear and character 56 because it depends on how complete the fore and hind fins are. 5. We added two new characters to the matrix to capture differences in forefin morphology: 42 and 45.6. We recoded Ichthyosaurus communis based on our own observations. 7. This is the first time that Protoichthyosaurus has been included in a phylogenetic analysis. The coding is based on our own observations. CHARACTER LISTThe character list and coding was based largely on . Characters are polarized using Mikadocephalus gracilirostris as the outgroup. All characters are unordered. Characters that are not referenced were developed as part of this study.

Ichthyosaur fossils are abundant in Lower Jurassic sediments with nine genera found in the UK. In this paper, we describe the partial skeleton of a large ichthyosaur from the Lower Jurassic (lower Sinemurian) of Warwickshire, England, which was conserved and rearticulated to form the centrepiece of a new permanent gallery at the Thinktank, Birmingham Science Museum in 2015. The unusual three-dimensional preservation of the specimen permitted computed tomography (CT) scanning of individual braincase elements as well as the entire reassembled skull. This represents one of the first times that medical imaging and three-dimensional reconstruction methods have been applied to a large skull of a marine reptile. Data from these scans provide new anatomical information, such as the presence of branching vascular canals within the premaxilla and dentary, and an undescribed dorsal (quadrate) wing of the pterygoid hidden within matrix. Scanning also revealed areas of the skull that had been modelled in wood, clay and other materials after the specimen’s initial discovery, highlighting the utility of applying advanced imaging techniques to historical specimens. Additionally, the CT data served as the basis for a new three-dimensional reconstruction of the skull, in which minor damage was repaired and the preserved bones digitally rearticulated. Thus, for the first time a digital reconstruction of the skull and mandible of a large marine reptile skull is available. Museum records show the specimen was originally identified as an example of Ichthyosaurus communis but we identify this specimen as Protoichthyosaurus prostaxalis. The specimen features a skull nearly twice as long as any previously described specimen of P. prostaxalis, representing an individual with an estimated total body length between 3.2 and 4 m.

Thousands of ichthyosaurs have been discovered from the rich Lower Jurassic deposits of the UK, with the majority collected from along the Lyme Regis-Charmouth area of the Dorset coast. Here, I describe a new leptonectid ichthyosaur, Wahlisaurus massarae gen. et sp. nov., based on a partial skull and an incomplete skeleton collected from the Lower Jurassic (Hettangian) of Nottinghamshire, England. Wahlisaurus can be referred to the Leptonectidae through the possession of an extremely slender and delicate snout, and a mandible shorter than snout which produces an overbite. This referral is supported by a phylogenetic analysis. The new taxon is distinguished from other ichthyosaurs through a unique combination of characters and autapomorphies of the pectoral girdle including the presence of both a scapular-coracoid foramen and a large and roughly ovoid coracoid foramen. A coracoid foramen has only previously been reported in the Triassic ichthyosaur Cymbospondylus. The peculiar coracoid morphology further highlights the taxonomic utility of coracoids in ichthyosaurs. The aforementioned features demonstrate that W. massarae cannot be referred to any currently recognised leptonectid. With the identification of W. massarae, it is the ninth Lower Jurassic ichthyosaur genus to be recognised worldwide, and it is the fifth documented in the lower Lias Group.