Ichthyosaurs Research Papers - Academia.edu (original) (raw)

Durante el año 2003, Shultz y colaboradores informaron sobre un esqueleto de ictiosaurio fragmentario que se colectó en el PN Torres del Paine, sur de Chile. El espécimen fósil fue descubierto dentro de un bloque errático, y dado lo fragmentario de los restos, no podían ser asignados a una especie, menos datarse con precisión, ni ligar a una formación específica (Shultz et al., 2003). Durante el mismo año, un grupo de glaciólogos magallánicos tomaron las primeras fotos de los huesos in situ en estratos expuestos en la base del Glaciar Tyndall. Estos especímenes descubiertos en Torres del Paine representan los ictiosaurios más meridionales conocidos hasta la fecha y amplían la distribución de este grupo de reptiles marinos unos 1500 - 2000 km al sur del material previamente descrito para la cuenca de Neuquén en Argentina (Gasparini y Fernández, 1997, 2005; Fernández y Aguirre-Urreta, 2005). Desde 2008, un grupo de investigación Chileno-Alemán estudia el ensamble fósil y la geología de este depósito. En un área de menos de 10 km2 se ha detectado sobre numerosos especímenes de ictiosaurios articulados y, a veces prácticamente completos, los que han sido tentativamente asignados a diferentes especies de Ophtalmosauridae. A ello se suman huesos aislados de ictiosaurios y cocodrilos, bien conservados, peces teleósteos ganoídeos, belemnites, amonites, inocerámidos y restos de plantas son también abundantes.

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- Paleontology, Cretaceous life, Patagonia, Ichthyosaurs

The rostrum fragment of an ichthyosaur from Northland in New Zealand is described. The specimen appears to belong to the genus Platypterygius. It is the first Mesozoic marine vertebrate fossil reported from Northland and the first cranial element of a Cretaceous ichthyosaur from New Zealand. The fragment is, unfortunately, of uncertain provenance and could have come from the widespread Northland Allochthon (Early Cretaceous–Oligocene) or the allochthonous Houhora Complex (late Early Cretaceous) or Whatuwhiwhi Formation (latest Early to Late Cretaceous), perhaps by way of initial erivation from the Early Miocene Omapere Conglomerate.

- by Sven Sachs
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- Paleontology, Vertebrate Palaeontology, Vertebrate Paleontology, Cretaceous life

Lower Triassic marine deposits, which can potentially provide important information on the diversity and trophic structure of marine ecosystems following the end-Permian mass extinction, are rarely exposed in the world. Given the sparse body fossil record from the Lower Triassic, non-body fossil evidences, such as trace fossils for example, may provide additional windows on fossil ecosystems. Herein, the authors recently found dark, amorphous lumps of various sizes, ranging from a few millimetres to 8 cm in maximum dimension, from the offshore marine deposit of upper Osawa Formation (Spathian, Lower Triassic) in the South Kitakami Terrane of northeast Japan. Compared with the surrounding siliciclastic sediments, the lumps are rich in phosphate and organic carbon, and poor in silicates. Shape, mode of occurrence, bone inclusion and geochemical signatures of these lumps confirm that these are coprolites, produced not by benthic sediment feeders, but most likely by nektonic animals. Bone inclusion also suggests that carnivorous fish and/or marine reptiles, constituting the higher part of the food chain, produced at least a part of the specimens. Despite the low diversity of the known fossil vertebrates from the Osawa formation, coprolites first shed light on the predator–prey interactions in the marine ecosystem in South Kitakami Terrane 5 Myr after the end-Permian mass extinction.

- by Yasuhisa Nakajima
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- Marine Ecology, Coprolite analysis, Triassic, Ichthyosaurs

The Early Jurassic ichthyosaur Ichthyosaurus displays a variety of bony features surrounding the external naris: a small triangular process on the lacrimal protruding into the external naris; a raised edge on the posterior portion of the naris formed by the lacrimal; or an arc-shaped bone at the posterior end of the naris. These features demarcate a circular, posterior region of the external naris. Similar features also occur in the narial region of other Early Jurassic taxa, including Temnodontosaurus, Leptonectes, Excalibosaurus, and Hauffiopteryx. Additionally, Leptonectes tenuirostris displays a protrusion or flange on the nasal that extends over the external naris. In the more derived ophthalmosaurid ichthyosaurs, bony structures around the naris are more pronounced. Large processes on the nasal almost separate the naris into two openings in Sveltonectes and Muiscasaurus. In other taxa (e.g., Simbirskiasaurus birjukovi, Arthropterygius thalassonotus) the naris is completely subdivided into two openings. A subdivided naris occurred in ophthalmosaurine ophthalmosaurids as early as the Oxfordian (Late Jurassic) in Baptanodon natans, as described here. Recent work interprets the complete partitioning of the naris as separate openings to accommodate the functions of air exchange and salt excretion. The bony structures seen in Early Jurassic taxa are probably precursors to the complete bony subdivision of the naris and might be related to the presence of nasal salt glands.

- by Judy Massare
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- Marine Reptiles, Ichthyosaurs
- by Luca Jaselli
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- Jurassic, Germany, Ichthyosaurs

The Early Cretaceous ichthyosaurs graveyard at the Tyndall Glacier in the Parque Nacional Torres del Paine, South Chile, is an outstanding locality both nation and worldwide. During two field campaigns in the years 2009 and 2010 40 articulated and semi-articulated ichthyosaur skeletons were discovered, comprising adults, juveniles, babies and embryos. The majority of the ichthyosaur specimens preserve diagnostic features permitting their identification to species level. Until now four different ichthyosaur species were identified in the field: Platypterygius hauthali (v. Huene, 1927) (Pardo et al. 2010 in preparation), ? Platypterygius platydactylus (Broili, 1907), ? Caypullisaurus bonapartei Fernández, 1997 and another hitherto unknown species that is different to the other three. This diversity is highly important for the understanding of the diversity in paleocommunities of ichthyosaurs during the Early Cretaceous. The taxonomic and the palaeobiogeographic analysis of the Tyndall ichthyosaur graveyard will throw new light on the evolutionary history of Cretaceous ichthyosaurs prior to their final extinction at the beginning of the Late Cretaceous. The abundance of near complete articulated ichthyosaur skeletons in the Tyndall area suggests mass mortalities caused by high-energy mudflows travelling down along submarine canyons. The ichthyosaurs were either caught directly by these mudflows or were dragged down into the abyss by the suction wave behind them. Their bodies ended up in an abyssal anoxic environment and were rapidly covered by fine sediment, which explains the excellent preservation.
The finding potential of the site as well as the quality of preservation and the quantity of specimens are unique for South America and place the Tyndall ichthyosaur locality among the best fossil sites for marine vertebrates worldwide.

- by Judith Pardo-Pérez
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- Ichthyosaurs, Early Cretaceous Marine Reptiles

Cretaceous ichthyosaurs have typically been considered a small, homogeneous assemblage sharing a common Late Jurassic ancestor. Their low diversity and disparity have been interpreted as indicative of a decline leading to their Cenomanian extinction. We describe the first post-Triassic ichthyosaur from the Middle East, Malawania anachronus gen. et sp. nov. from the Early Cretaceous of Iraq, and re-evaluate the evolutionary history of parvipelvian ichthyosaurs via phylogenetic and cladogenesis rate analyses. Malawania represents a basal grade in thunnosaurian evolution that arose during a major Late Triassic radiation event and was previously thought to have gone extinct during the Early Jurassic. Its pectoral morphology appears surprisingly archaic, retaining a forefin architecture similar to that of its Early Jurassic relatives. After the initial latest Triassic radiation of early thunnosaurians, two subsequent large radiations produced lineages with Cretaceous representatives, but...

- by Darren Naish
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- Marine Biology, Paleontology, Middle East History, Morphological evolution

During the Late Jurassic, important palaeogeographic events occurred in Eurasia, North America and Gondwana. Continental rift, subduction and orogeny produced different levels of marine inundation of terrestrial systems, with rising sea level. Shallow epicontinental seaways started to separate North America from Eurasia, Gondwana, and also between segments of Gondwana itself. Tethys, the east-west seaway, expanded and at times covered large parts of the continental interior of Eurasia. The aperture of new seaways such as the Greenland-Norwegian seaway and the Mezen-Pechora strait system in the northern hemisphere; the Hispanic Corridor, between North and South America; and the Trans-Erythrean seaway (or South Africa/Rocas Verdes seaway) in the southern hemisphere allowed for intermittent interchange of invertebrate and marine vertebrate faunas.
During the past five years, the ichthyosaur fossil record has provided a way to describe new species so as to complement diagnoses of species that for a long time had been either synonymised or considered invalid. These taxonomic studies allow us now to understand the paleo-distribution of the ichthyosaurs around the world better as the relationships between the realms of the northern-southern hemisphere and boreal regions. The present report is a generic-level analysis of the dispersal routes of ichthyosaurs during the Late Jurassic compared with one of its top predators, Pliosaurus, and the palaeogeographic significance of high-latitude species such as Arthropterygius spp., Undorosaurs spp., Cryopterygius spp, Janusaurus and non-ubiquitous ichthyosaurs.

- by Judith Pardo-Pérez and +2
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- Palaeobiogeography, Ichthyosaurs, Lower Jurassic

"Ichthyosaurs were highly adapted to a marine lifestyle, as shown by their fish-like body shape and their assumed active swimming abilities and high metabolic rates. However, the processes of adaptation to an aquatic life in the early stages of this lineage remain poorly understood. Here, we present the first osteohistological data concerning the most basal ichthyopterygian yet known, Utatsusaurus hataii, from the Lower Triassic of Japan. The cancellous bone structure suggests adaptation to active swimming in an open marine environment. Moreover, the possible occurrence of rapidly deposited bone tissue, in a fibrolamellar complex, suggests a higher metabolic rate than in modern poikilothermic reptiles, and therefore a trend toward homeothermy. This basal ichthyosaur, with its elongate body, was already more adapted to an aquatic lifestyle than expected from its morphology, and the process of adaptation to a marine lifestyle was already well advanced by the Early Triassic.
http://www.app.pan.pl/article/item/app20120045.html

- by Yasuhisa Nakajima
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- Paleobiology, Vertebrate Paleontology, Fossil Bone Histology, Triassic
- by Cristiano Dal Sasso and +3
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- Earth Sciences, Vertebrate Paleontology, Triassic, Triassic vertebrates

A large partial forefin (YORYM 2005.2411) from the Lower Jurassic of Yorkshire is assigned to Ichthyosaurus on the basis of the humerus shape, two digits originating from the intermedium, and an anterior digital bifurcation. The humerus is 11.7 cm long and the forefin is 38.5 cm long, but incomplete, probably missing more than 1/3 of its length. Regression analyses suggest that the individual had a jaw length of 56 cm and a total length to the tail bend of almost 3 m. This individual represents the largest Ichthyosaurus reported from the U.K. Although interest in the reptiles of the Yorkshire coast dates back to the early 1800s, specimens of Ichthyosaurus from the area are rare.

- by Dean Lomax
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- Paleontology, Taxonomy, Palaeontology, Ichthyosaurs

- by Judith Pardo-Pérez
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- Palaeobiogeography, Marine Reptiles, Ichthyosaurs, Late Jurassic

Mesozoic marine reptiles went through a severe turnover near the end of the Triassic.

- by Stijn Goolaerts
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- Paleontology, Vertebrate Palaeontology, Vertebrate Paleontology, France

Three isolated, partial skulls from historic collections, previously identified as Ichthyosaurus communis are herein assigned to Protoichthyosaurus prostaxalis. A fourth, nearly complete skull is referred to Protoichthyosaurus applebyi, only the second known specimen of the species. It provides additional information on the posterior portion of the skull and mandible. The diagnosis of P. applebyi is emended to include a postorbital that is dorsoventrally long but anteroposteriorly narrow relative to its length. It separates most of the jugal dorsal ramus from the orbit margin and makes up much more than half of the orbit posterior margin. The genus Protoichthyosaurus can be most easily distinguished from its sister taxon, Ichthyosaurus, by the forefin morphology, with three primary digits (II-IV) in the former and four primary digits (II-V) in the latter. In addition, the pineal in Protoichthyosaurus is bordered posteriorly by the parietals rather than being entirely enclosed by the frontals as in Ichthyosaurus. Many skull features, although not unique to Protoichthyosaurus, can together distinguish it from Ichthyosaurus. These include: a low-crowned skull with a long, slender rostrum; a large, posteriorly high, triangular external naris; an asymmetric maxilla with a long anterior process; a dorsoventrally long prefrontal anterior process that separates the dorsal process of the lacrimal from the orbit margin; and tooth roots with deep grooves that extend to the base of the crown. However, these characters vary among individuals and are often difficult to assess because of orientation, completeness, or preservation. Characters that distinguish individual species of Protoichthyosaurus from individual species of Ichthyosaurus are less subjective and often more easily evaluated.

- by Dean Lomax and +1
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- Jurassic, Ichthyosaurs, Ichthyosauria

Se resumen los registros de ictiosaurios (Reptilia: Ichthyosauria) conocidos hasta la fecha en Chile. Los
hallazgos en el norte del país incluyen abundantes registros desde el Triásico tardío hasta el Jurásico
Medio, sin embargo, el material es hasta ahora fragmentario y poco diagnóstico, correspondiendo
en todos los casos a Ichthyosauria indet. Por otro lado, los hallazgos en el extremo sur del país han
proporcionado abundantes restos articulados, los que al presente permiten documentar la presencia del
género Platypterygius y de la familia Ophthalmosauridae. El conjunto de hallazgos en Chile cuenta
con el registro más antiguo del grupo en Sudamérica e incluye uno de los yacimientos con preservación
excepcional de ictiosaurios del Cretácico Inferior, representando un importante potencial para la
comprensión del grupo y su distribución durante dicho lapso.

- by Judith Pardo-Pérez
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- Paleontology, Chile, Vertebrate Paleontology, Marine Reptiles

A partial ichthyosaur skeleton is described from the Grayson Marl (Late Cretaceous: Early Cenomanian, ~97 Ma) from Tarrant County, Texas. Prior to this discovery, the Cretaceous record of Texas ichthyosaurs consisted of isolated vertebrae. The new specimen consists of a partial disarticulated skull and postcranial elements including a postfrontal, parietal, quadrate, angular, surangular, several teeth, and several vertebrae including the atlas-axis complex, coracoid, and articulated partial forelimb. The forelimb is diagnostic in having a zeugopodial element anterior to the radius, rectangular phalanges, and an intermedium that does not make contact with the humerus allowing referral to Platypterygius von Huene 1922. This occurrence is the youngest of that taxon in Texas and is consistent with late European occurrences of the genus Platypterygius.

- by Thomas L Adams and +1
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- Vertebrate Paleontology, Ichthyosaurs

Ichthyosaurs rapidly diversified and colonised a wide range of ecological niches during the Early and Middle Triassic period, but experienced a major decline in diversity near the end of the Triassic. Timing and causes of this demise and the subsequent rapid radiation of the diverse, but less disparate, parvipelvian ichthyosaurs are still unknown, notably be-cause of inadequate sampling in strata of latest Triassic age. Here, we describe an exceptionally large radius from Lower Jurassic deposits at Penarth near Cardiff, south Wales (UK) the morphology of which places it within the giant Triassic shastasaurids. A tentative total body size estimate, based on a regression analysis of various complete ichthyosaur skele-tons, yields a value of 12–15 m. The specimen is substantially younger than any previously reported last known occur-rences of shastasaurids and implies a Lazarus range in the lowermost Jurassic for this ichthyosaur morphotype.

- by Cindy Howells
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- Evolutionary Biology, Geology, Ecology, Mass extinctions

Mesozoic marine reptile fossils are known from numerous localities in Australia. The vast majority come from epicontinental marine rocks of Cretaceous age (Berriasian-Maastrichtian); however rare fragmentary specimens have also been recovered from Lower-middle Jurassic (Upper Liassic-Bajocian) freshwater and marine deposits. A tentative report of ichthyosaur material from the Lower Triassic (Spathian) of Western Australia is not yet rigorously substantiated. Because the Jurassic record is poor, meaningful biogeographic comparisons are limited largely to Early Cretaceous faunas. These currently include several cosmopolitan (ichthyosaur Platypterygius, pliosauroid Leptocleidus and Kronosaurus) and endemic (chelonians Notochelone and Cratochelone) genera, all represented by local regional species. Interestingly, the earliest and latest representatives of several family-level clades (e.g. Polycotylidae, Rhomaleosauridae and possibly the Pachypleurosauridae) are present, perhaps indicating that the Australian region was both a centre of origin and refuge for many groups. Marine reptile faunas from Australia and elsewhere show common changes in taxonomic diversity and faunal composition during the mid-late Mesozoic. For example, ichthyosaurs dominate Early Jurassic (Hettangian-Toarcian) assemblages but are replaced by a rapid radiation of plesiosaurs and marine mesosuchian crocodilians in the Callovian (middle Jurassic). During the Early Cretaceous (Aptian), plesiosaurs formed the major component, at least in the Australian faunas, with ichthyosaurs (and elsewhere marine mesosuchians) undergoing a significant drop in diversity. By the Albian (middle Cretaceous), chelonioid turtles had emerged as a major new faunal element that persisted throughout the Late Cretaceous (Cenomanian- Maastrichtian), by which time ichthyosaurs had become extinct and mosasaurs rapidly evolved to dominate most marine reptile assemblages.

- by Benjamin P. Kear
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- Vertebrate Paleontology, Sea Turtles, Ichthyosaurs, Plesiosauria
- by Arthur Chubur
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- Vertebrate Paleontology, Cretaceous, Ichthyosaurs, Plesiosauria

Ichthyosaurus communis De la Beche & Conybeare, 1821 and I. intermedius Conybeare, 1822 have been considered synonymous by some researchers, but distinct species by others. The distinction between the two species was originally based on tooth morphology, which has been shown to vary ontogenetically as well as within an individual. Subsequent literature of the nineteenth century did not propose adequate diagnostic features to distinguish the two species. In addition, illustrations suggest that both species were confused with I. breviceps, which was defined over 50 years later. The type specimens of both species are missing, making the problem unresolvable. However, a neotype was designated for I. communis to retain the widely used species name and to stabilize the taxonomy. The species can be recognized by a symmetric, triangular maxilla with long processes and a large, broad, triradiate lacrimal, as well as a unique combination of other characters. The neotype shares numerous features with the intermedius ‘type figure’, including the morphologies of the maxilla, prefrontal, lacrimal, jugal and postorbital, such that the two are nearly indistinguishable. Thus I. intermedius must be considered a synonym of I. communis. Ichthyosaurus communis can be identified from the Lyme Regis-Charmouth coast, west Dorset; the ?Whitby coast of Yorkshire; and probably from Street, Somerset. The stratigraphical range of I. communis is at least lower Hettangian to lower Sinemurian.

- by Dean Lomax and +1
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- Marine Reptiles, Ichthyosaurs, Ichthyosauria, Jurassic Marine Reptiles

An ichthyosaur specimen, presumably of Ophthalmosaurus natans, was discovered with gastric material preserved between the ribs of the skeleton. The specimen is from the Redwater Shale Member of the Sundance Formation, Natrona County, Wyoming. The specimen is comprised of numerous vertebrae and ribs, a partially articulated forelimb, and other unidentified bones within a calcite concretion. A portion of the gastric mass is visible between the ribs within one concretion block. The friable, low density mass appears to be located in the central or posterior torso, with a smaller amount of material more anteriorly located. The gastric material consists of badly fragmented coleoid cephalopod hooklets, loosely cemented by calcite crystals. The stomach contents are comparable to those reported from ichthyosaurs from the Lower Jurassic of England and Germany, although the mode of preservation is not.

- by Judy Massare
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- Ichthyosaurs, Ichthyosauria

Ichthyosaurs first appear in the Early Triassic with an elongate, lizard-shaped anatomy. The most derived ichthyosaurs, including the Late Triassic to Early Jurassic Eurhinosauria and the Late Triassic to Mid Cretaceous Thunnosauria, evolved more streamlined fish-shaped bodies. A species-level cladistic analysis of this derived group of ichthyosaurs, using 60 characters for 17 outgroup taxa and one ingroup taxon, was conducted using PAUP* (Swofford, 1998). The new analysis is compared to that of genus-level analysis of ichthyosaurs by looking at the clade-defining character state changes in each. I use a total evidence approach, meaning a detailed phylogenetic analysis plus data on stratigraphic and geographic occurrences, to answer two questions. First, is it more plausible to place Stenopterygius as a sister to the Ophthalmosauria or to permit the longer ghost lineage for Ophthalmosauria that would be required if Ichthyosaurus is its sister taxon, a question suggested by Motani (1999b)? A phylogenetic tree incorporating known stratigraphic ranges was constructed, based on the species-level cladistic analysis, to help quantify the stratigraphic debt using the relative completeness index (RCI), stratigraphic congruency index (SCI) and the gap excess ratio (GER). When a species-level analysis was performed, four previously defined clades fell apart, including Leptonectes, Stenopterygius, Eurhinosauria and Ophthalmosauria.

- by Jessica Lawrence Wujek
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- Phylogeny/phylogenetics, Ichthyosaurs

Background Ichthyosauria is a diverse clade of marine amniotes that spanned most of the Mesozoic. Until recently, most authors interpreted the fossil record as showing that three major extinction events affected this group during its history: one during the latest Triassic, one at the Jurassic–Cretaceous boundary (JCB), and one (resulting in total extinction) at the Cenomanian-Turonian boundary. The JCB was believed to eradicate most of the peculiar morphotypes found in the Late Jurassic, in favor of apparently less specialized forms in ...

- by Darren Naish
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- Geography, Paleontology, Biology, Vertebrate Paleontology

What happens after the death of a marine tetrapod in seawater? Palaeontologists and neontologists have claimed that large lung-breathing marine tetrapods such as ichthyosaurs had a lower density than seawater, implying that their carcasses floated at the surface after death and sank subsequently after leakage of putrefaction gases (or ‘‘carcass explosions’’). Such explosions would thus account for the skeletal disarticulation observed frequently in the fossil record. We examined the taphonomy and sedimentary environment of numerous ichthyosaur skeletons and compared them to living marine tetrapods, principally cetaceans, and measured abdominal pressures in human carcasses. Our data and a review of the literature demonstrate that carcasses sink and do not explode (and spread skeletal elements). We argue that the normally slightly negatively buoyant carcasses of ichthyosaurs would have sunk to the sea floor and risen to the surface only when they remained in shallow water above a certain temperature and at a low scavenging rate. Once surfaced, prolonged floating may have occurred and a carcass have decomposed gradually. Our conclusions are of significance to the understanding of the inclusion of carcasses of lung-breathing vertebrates in marine nutrient recycling. The postmortem fate has essential implications for the interpretation of vertebrate fossil preservation (the existence of complete, disarticulated fossil skeletons is not explained by previous hypotheses), palaeobathymetry, the physiology of modern marine lung-breathing tetrapods and their conservation, and the recovery of human bodies from seawater.

- by Christian Klug
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- Taphonomy, Sea Level, Sea-level change, Ichthyosaurs

Many collections of Lower Jurassic ichthyosaurs from the U. K. include historic specimens collected during the 19th century, and often with poorly known origins. Here we describe nearly complete skeletons of the Lower Jurassic genus Ichthyosaurus that are probably composites or that, at least, require further examination to assess their authenticity. Specimens from the Thomas Hawkins and Charles Moore collections, in particular, should be examined carefully to determine if the entire specimen is a single individual. The most common elements added to skeletons of Ichthyosaurus are whole or partial forefins, hindfins, or posterior portions of the vertebral column. Historic and more recently collected specimens can also have reconstructed or rearranged portions, sometimes done so expertly that they are barely noticeable, if not for documentation in museum records. Composite, rearranged, and reconstructed specimens can provide valuable morphological data once the added or altered portions are recognized.

- by Judy Massare
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- Ichthyosaurs, Lower Jurassic, Ichthyosauria, Jurassic Marine Reptiles

Ichthyosaurs rapidly diversified and colonised a wide range of ecological niches during the Early and Middle Triassic period, but experienced a major decline in diversity near the end of the Triassic. Timing and causes of this demise and the subsequent rapid radiation of the diverse, but less disparate, parvipelvian ichthyosaurs are still unknown, notably because of inadequate sampling in strata of latest Triassic age. Here, we describe an exceptionally large radius from Lower Jurassic deposits at Penarth near Cardiff, South Wales (UK) the morphology of which places it within the giant Triassic shastasaurids. A tentative total body size estimate, based on a regression analysis of various complete ichthyosaur skeletons, yields a value of 12-15 m. The specimen is substantially younger than any previously reported last known occurrences of shastasaurids and implies a Lazarus range in the lowermost Jurassic for this ichthyosaur morphotype.

- by Cindy Howells and +1
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- Ichthyosaurs

Alfred Nicholson Leeds (1847–1917) is famous among vertebrate palaeontologists for amassing
an invaluable collection of fossil vertebrates from the Middle Jurassic aged ‘Oxford Clay’
deposits of the Peterborough district in the UK, throughout the late nineteenth and early twentieth
centuries. Part of his collection was acquired by the National Museum of Ireland—Natural
History in November 1893 but has not previously been described. This fossil material includes a
suite of Jurassic marine reptiles: crocodiles, plesiosaurs and ichthyosaurs. There are no examples,
however, of the giant fish Leedsichthys; the remains of which are commonly found among the
fauna of the Oxford Clay Formation. Despite representing only a very small fraction of the total
Leeds Collection, the specimens in Ireland are significant historically, and have scientific value in
their own right. For the first time, in this paper, a historical review of the Dublin Leeds Collection
is presented, the fossil specimens described and a long-lost piece of important documentation is
presented.

- by Adam S Smith and +2
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- Marine Biology, Paleobiology, Geology, Paleontology

Recent descriptions of new taxa and recognition of survivorship of Jurassic genera across the Jurassic-Cretaceous boundary bring the total number of Cretaceous ichthyosaur genera to eight. Taxa currently known from the Cretaceous include Ophthalmosaurus, Caypullisaurus, Aegirosaurus, Platypterygius, Maiaspondylus, Athabascasaurus, Sveltonectes, and Acamptonectes. This review summarizes the occurrence of all Cretaceous genera. A discussion of morphological diversity demonstrates the different, though overlapping, ecological niches occupied by the different taxa, while the comparison of phylogenetic hypotheses shows the problems inherent in understanding the evolutionary relationships between Cretaceous genera. The Late Jurassic radiation indicated in the competing phylogenetic hypotheses may correlate with the opening of the Atlantic Ocean or additional dispersal routes established by the breakup of Gondwana. Inclusion of the stratigraphically oldest Platypterygius species may aid in resolving these evolutionary relationships.

- by Maria Zammit
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- Phylogenetics, Vertebrate Palaeontology, Palaeoecology, Ecological Niche Modeling

Cretaceous marine amniote fossils have been documented from Australia for more than 150 years, however, their global significance has only come to the fore in the last decade. This recognition is a product of accelerated research coupled with spectacular new discoveries from the Aptian–Albian epeiric sequences of the Eromanga Basin – especially the opal-bearing deposits of South Australia and vast lagerstätten exposures of central-northern Queensland. Novel fragmentary records have also surfaced in Cenomanian and Maastrichtian strata from Western Australia. The most notable advances include a proliferation of plesiosaurian taxa, as well as detailed characterization of the 'last surviving' ichthyosaurian Platypterygius, and some of the stratigraphically oldest protostegid sea turtles based on exceptionally preserved remains. Compositionally, the Australian assemblages provide a unique window into the otherwise poorly known Early Cretaceous marine amniote faunas of Gondwana. Their association with freezing high latitude palaeoenvironments is also extremely unusual, and evinces a climate change coincident diversity turnover incorporating the nascent radiation of lineages that went on to dominate later Mesozoic seas.

- by Benjamin P. Kear
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- Vertebrate Paleontology, Sea Turtles, Marine Reptiles, Cretaceous

is the only valid reptilian taxon known from the Lower Triassic Osawa Formation in Minamisanriku Town, Miyagi Prefecture, which records the recovery of the marine ecosystem shortly after the end-Permian mass extinction. In this paper, we describe a fragmentary specimen of an indeterminate ichthyopterygian which is distinguished from Utatsusaurus hataii based on rib morphology. The discovery of a previously unknown ichthyopterygian implies that the taxonomic diversity of the reptilian fauna of this formation is higher than previously assumed.

- by Yasuhisa Nakajima and +1
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- Triassic, Triassic vertebrates, Ichthyosaurs

The Lower Cretaceous (Aptian-Albian) southern high latitude deposits of Australia have yielded a diverse range of marine
reptile fossils. Ichthyosaurs and at least five distinct plesiosaur taxa have been recorded. Most of the current marine reptile specimens are derived from the predominantly Aptian Bulldog Shale and Wallumbilla Formation. These units, famous for producing opal, represent shallow epicontinental marine depositional environments. Fragmentary plesiosaur remains have also been recovered from high latitude non-marine deposits of the Wonthaggi, Eumeralla, and Griman Creek formations. These are Aptian to middle Albian in age, and comprise fine-grained fluviatile/estuarine sediments laid down in inland rift valleys and coastal flood plains near the Cretaceous southern polar circle. Estimates of palaeolatitude place most of southern Australia at around 60o to 80o S during the late Early Cretaceous. Sedimentary structures, fossils, isotope data, and climatic modeling indicate highly seasonal cool-cold conditions possibly with winter freezing. This contrasts markedly with climate regimes typically tolerated by modern aquatic reptiles, but suggests that some Mesozoic forms may have possessed adaptations to cope with low average water temperatures.

- by Benjamin P. Kear
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- Vertebrate Paleontology, Marine Reptiles, Ichthyosaurs, Plesiosauria

The ichthyosaur fossil record is interspersed by several hiatuses, notably during the Cretaceous. This hampers our understanding of the evolution and extinction of this group of marine reptiles during the last 50 million years of its history. Several Cretaceous ichthyosaur taxa named in the past have subsequently been dismissed and referred to the highly inclusive taxon Platypterygius, a trend that has created the impression of low Cretaceous ichthyosaur diversity. Here, we describe the cranial osteology, reassess the stratigraphic age, and evaluate the taxonomy and phylogenetic relationships of two Cretaceous ichthyosaurs from western Russia: Simbirskiasaurus birjukovi from the early Barremian and Pervushovisaurus bannovkensis from the middle Cenomanian, both formerly regarded as nomina dubia, and allocated to Platypterygius sp. and Platypterygius campylodon, respectively. We show that Simbirskiasaurus birjukovi and Pervushovisaurus bannovkensis are valid platypterygiine ophthalmosaurids, notably characterized by a peculiar narial aperture. The cranial anatomy and phylogenetic relationships of these taxa illuminate the evolution of narial aperture anatomy in Cretaceous ichthyosaurs, clarify the phylogenetic relationships among platypterygiines, and provide further arguments for a thorough revision of Platypterygius.

- by Maxim Arkhangelsky
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- Zoology, Early Cretaceous, Russia, Marine Reptile Paleontology

Fossil reptiles from the Mesozoic are rarities in Nordrhein-Westfalen (western Germany), and the majority of specimens found are only fragmentarily preserved. The first report of a fossil reptile, parts of a mosasaur skeleton from the Upper Cretaceous (Cenoman) of Schöppingen, was published by W. von der Marck already in 1858. Another mosasaur from Halden (Senon) was described by Pompeckj (1910). Lommerzheim (1976) reported a nearly complete wing of an unidentified pterosaur from the Upper Cretaceous (Turon) of Dinslaken. The present repository of the poorly prepared remain is unknown. The Lower Cretaceous (Berriasian) clay-pit Gerdemann near Gronau yielded plesiosaurs, dinosaurs, and turtles. Wegner (1914) erected Brancasaurus brancai, an elasmosaurid plesiosaur represented by an almost complete skeleton and mentioned a second plesiosaur genus still to be described. Recently, two probably theropodan or crocodilian vertebrae (Sachs 1996) and a humerus of a nodosaurid (Sachs 1997) were reported. The most important finds of reptiles from Nordrhein-Westfalen have been excavated in the Lower Cretaceous (Aptium) near Nehden. Among the material are numerous remains of iguanodontids including a juvenile specimen, a possible hypsilophodont, an unidentified theropod, as weil as crocodilian and turtle remains (Norman et al. 1987). Wallücke is a rich locility in the Callovium. Michaelis et al. (1997) described plesiosaurs, an ichthyosaur, a marine crocodile, and two dinosaur genera (Lexovisaurus and Dryosaurus) from this locality, however, all designation are based on rather incomplete material. A large but incomplete ichthyosaur from the Early Jurassic (Toarcian) of Bielefeld was described by Hungerbühler & Sachs (1996) as Temnodontosaurus sp. A Middle Jurassic (Bathonian) specimen also from the Bielefeld area is too incomplete for proper identification, but could represent an ophthalmosaurid ichthyosaur (Sachs & Hungerbühler 1996).

- by Sven Sachs
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- Paleontology, Vertebrate Palaeontology, Vertebrate Paleontology, Dinosaur Paleontology

Outcrop of the oldest Cretaceous sequence in the Giralia Anticline and the Giralia No, 1 well, penetrating the same sequence, are described and biostratigraphically assessed in detail. The Cretaceous rocks lie on an erosion surface cut into Permian strata. A 10 m thick basal sand unit, the Birdrong Sandstone, is overlain by 56 m of carbonaceous siltstone-mudstone (Muderong Shale). The Birdrong Sandstone in the anticline belongs to the Muderongia australis Zone of late Hauterivian-Barremian age, as does the lower part of the Muderong Shale. The age of the upper Muderong Shale is uncertain, as is the age of a 10 m thick sandstone unit (probable Windalia Sand Member) which separates the Muderong Shale from the late Aptian Windalia Radiolarite. Abundant fossil conifer wood, much of it with Teredolites borings, is present in outcrop referred to the upper part of the Birdrong Sandstone. Scattered ichthyosauran bones, probable plesiosauran remains, and rare ammonites also are present at this level. A growth-ring analysis of the wood suggests that a seasonal humid mesothermal climate prevailed in the region. Changes in sediment composition, palynomorph assemblages, and foraminiferal biofacies reflect retrogradation of marine facies during deposition of the Birdrong Sandstone and lowermost Muderong Shale, followed by aggradation through most of the Muderong Shale with maximum water depths less than 50 m. Within the sequence, the Birdrong Sandstone and the lowermost Muderong Shale represent a transgressive systems tract, whereas most of the Muderong Shale belongs to a highstand systems tract. The sequence reflects a transgressive pulse that was part of the progressive submergence of vast areas of the Australian continent during the Early Cretaceous. This late Hauterivian-Barremian transgressive pulse is recognised in widely separated basins and may represent a synchronous continent•wide sea level rise.

- by Stephen McLoughlin
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- Ichnology, Paleobotany, Palynology, Dinoflagellates

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 cooperative relationship essential to the preservation of Scotland's fossil heritage.

- by Jeff Liston
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- Marine Biology, Geology, Vertebrate Paleontology, Palaeontology

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 mo...

- by Nigel R Larkin
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- Computed Tomography, Taxonomy, Palaeontology, Ichthyosaurs

The bone microstructure of Platypterygius americanus from the Mowry Shale of northeastern Wyoming was examined using thin-sections of paddle bones, vertebrae, and a poorly preserved limb from three individuals. P. americanus has a thin layer of cortical bone, with most of the bone being trabecular bone. The trabeculae define elongated or tubular vacuities. Porosity was greatest in the vertebrae, intermediate in the paddle bones, and least in the limb. Within an individual, the difference in bone porosity between different bones was statistically significant. Furthermore, among individuals, the porosity of paddle bones is significantly different, but the porosity of vertebrae is not. Bone porosity has been used to identify partitioning of the water column by mosasaurs. These specimens of P. americanus had bone porosities that varied from 46% to 64%, suggesting that the species frequented deeper portions of the water column.

- by Judy Massare
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- Fossil Bone Histology, Ichthyosaurs

The fossil giant amphipod Rosagammarus minichiellus n. gen., n. sp. occurs in Triassic limestone (Luning Formation, west-central Nevada) in association with giant ichthyosaurs (Shonisaurus sp.) and the deep-water trace fossil Protopaleodictyon ichnosp. Fossil pereion and pereiopod morphology suggest affinities with the Acanthogammaridae, a freshwater amphipod family largely endemic to Lake Baikal. The large size (17 cm) of the Triassic amphipod shows that supergiant, deep marine amphipods comparable to modern Alicella gigantea Chevreux, 1899 were extant during the early Mesozoic. By analogy with Alicella gigantea, Rosagammarus minichiellus n. gen., n. sp. was a necrophagous, benthopelagic scavenger that fed on ichthyosaur and other sea floor carcasses. Rosagammarus minichiellus n. gen., n. sp. appears to be the oldest known fossil amphipod. This discovery extends the known geological range of Amphipoda by at least 170 million years.

- by Mark McMenamin
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- Invertebrate Paleontology, Amphipoda, Triassic, Deep sea ecology

The paleontological collection of the Comiso Natural History Museum (Sicily, Italy) includes two ichthyosaurian specimens from the Lower Jurassic Posidonia Shale (southwestern Germany). Based on comparative morphology, we refer them to... more

Here we report for the first time on the presence of ichthyosaurs in Sicily, southern Italy. The deposit of origin (Mufara Formation) can be dated to the upper Carnian (Tuvalian substage) based on a typical association of ammonites, one of which (Shastites sp.) is embedded in the sediment still encrusting one of the bone specimens recently found. The latter consist of two isolated vertebral centra that are referred to the Ichthyosauria thanks to their disk-like shape (i.e. they are much taller than long) combined with the amphicelous condition, lack of transverse processes, and presence of rib articulations on the central sides. The largest specimen is more precisely an anterior dorsal vertebra from an adult individual, ascribed to Shastasauridae indet. By the presence of elongated reniform diapophyseal facets, cranially not truncated, and absence of parapophyses. The smaller specimen represents an anterior cervical element from an immature individual of a likely smaller-sized, inde...

- by Gianni Insacco and +3
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- Earth Sciences, Vertebrate Paleontology, Triassic, Triassic vertebrates

- by Judy Massare
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- Ichthyosaurs, Lower Jurassic, Ichthyosauria

The Blanknuten Member of the Botneheia Formation preserves ichthyopterygians of various body-sizes. Due to the fragmentary nature of their remains, their systematic positions are controversial. The most complete skeleton of a mixosaur from Svalbard (PMO 219.250) described in this
paper adds new data to the Phalarodon-Mixosaurus controversy, which is directly connected to the Svalbard taxa, starting with the description of Ichthyosaurus nordenskioeldii by Hulke in 1873. The ratios of the posterior dorsal vertebrae to the mid caudal vertebrae are a mixture of what is
stated to be typical for P. callawayi, M. nordenskioeldii and M. cornalianus. We conclude that PMO 219.250 most likely should be assigned to the genus Phalarodon, but refrain from further assignment to a species.

- by Aubrey Jane Roberts and +1
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- Svalbard, Triassic, Ichthyosaurs, Triassic Svalbard

An unusual arrangement of ichthyosaur bones in central Nevada has perplexed paleontologists for decades. Originally thought to be a site of mass stranding in shallow water, more recent research results indicate that it represents a deep-water site. This paper reviews the geological and statistical evidence favoring the Triassic Kraken hypothesis, namely, the concept that the ichthyosaurs were dragged to their death by an ancient cephalopod of unusual size.

- by Mark McMenamin
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- Cephalopods, Octopus behavior, Triassic, Ichthyosaurs

The paleontological diversity of Mesozoic marine reptiles in northeastern Mexico shows an extensive fossil record, composed of different orders, including Ichthyosauria, a group with reports in Jurassic formations of the region. This paper presents two specimens collected in Galeana, Nuevo León, comprised by postcranial elements, from the La Caja Formation, of the Upper Jurassic. The mentioned specimens increase the fossil record of the area and contribute to the greater understanding of the fauna and paleoecological diversity of the Paleo-Gulf of Mexico during the Upper Jurassic.

- by Rogelio A Reyna-Hernández
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- Paleontology, Vertebrate Paleontology, Ichthyosaurs, Upper Jurassic

Reports of pathological ichthyosaur fossils are very rare. The identification of a series of healed cuts and an associated gouge on the lower jaw of an adult (ca 5 metres body length) Platypterygius specimen from the Lower Cretaceous of Australia is therefore significant, because it constitutes direct evidence of bite force trauma sustained during the life of the animal. Based on the close spacing and non-lethal facial positioning of the wounds, they were probably not inflicted by a predator. Alternative explanations might include an accidental aggressive encounter with another large vertebrate, or perhaps an intraspecific interaction such as during courtship or combat over food, mates or territory.

- by Maria Zammit
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- Evolutionary Biology, Geology, Ecology, Palaeopathology