Ichthyosaurian relationships illuminated by new primitive skeletons from Japan

  title={Ichthyosaurian relationships illuminated by new primitive skeletons from Japan},
  author={Ryosuke Motani and Nachio Minoura and Tatsuro Ando},
The Ichthyosauria is a group of reptiles with fish-shaped bodies from the Mesozoic (65–250 million years ago),. Their secondary adaptations to aquatic life have obscured their ancestral features,, and basal ichthyosaurs, which would be expected to retain these ancestral features (plesiomorphies), are poorly represented in the fossil record. As a result, their relationships to other amniotes have been controversial for over 180 years,. New specimens of Utatsusaurus hataii from the Lower Triassic… Expand
Abstract Omphalosaurus is a marine reptile known from the latest Early Triassic to the Middle Triassic. It has a wide distribution in the northern hemisphere, occurring in the eastern Pacific realm,Expand
Osteohistology of the Early Triassic Ichthyopterygian Reptile Utatsusaurus hataii: Implications for Early Ichthyosaur Biology
The first osteohistological data concerning the most basal ichthyopterygian yet known, Utatsusaurus hataii, from the Lower Triassic of Japan is presented, and the cancellous bone structure suggests adaptation to active swimming in an open marine environment. Expand
A New Triassic Primitive Ichthyosaur from Yuanan, South China
: Based on the systematic study of two fossil skeleton specimens collected from the top of the third member of the marine Lower Triassic Jialingjiang Formation of Yuanan, Hubei Province, SouthExpand
Reinterpretation of the Cranial Morphology of Utatsusaurus hataii (Ichthyopterygia) (Osawa Formation, Lower Triassic, Miyagi, Japan) and its Systematic Implications
The first complete description of the skull of UHR 30691 and the incorporation of data derived from it into a phylogenetic analysis retrieves a monophyletic Ichthyopterygia that is supported by 18 unambiguous synapomorphies and recovers Utatsusaurus in a basal clade with Parvinatator (united by one unambiguous feature). Expand
A New Ophthalmosaurid (Ichthyosauria) from Svalbard, Norway, and Evolution of the Ichthyopterygian Pelvic Girdle
The Slottsmøya Member Lagerstätte ichthyosaurs are significant in that they represent a diverse assemblage of ophthalmosaurids that existed immediately preceding and across the Jurassic–Cretaceous boundary, and expand the known range in size variation of pelvic girdle elements in the clade. Expand
Cranial Morphology and Relationships of a New Grippidian (Ichthyopterygia) from the Vega-Phroso Siltstone Member (Lower Triassic) of British Columbia, Canada
ABSTRACT In 1989, TMP 89.127.3, a basal ichthyopterygian, was collected as a counterpart slab from the Vega-Phroso Siltstone Member (Lower Triassic) of the Sulphur Mountain Formation inExpand
Cranial morphology of Platypterygius longmani Wade, 1990 (Reptilia : Ichthyosauria) from the Lower Cretaceous of Australia.
Preparation of specimens using acetic acid and application of high-resolution X-ray computed tomographic analyses has revealed many previously unrecorded anatomical details, including the absence of a coronoid and squamosal, and the presence of well-developed epipterygoids facets on the pterygoid and parietal. Expand
New Mixosaurid Ichthyosaur Specimen from the Middle Triassic of SW China: Further Evidence for the Diapsid Origin of Ichthyosaurs
Abstract Recent cladistic analyses have all suggested a diapsid origin of ichthyosaurs. However, an intermediate evolutionary stage of the lower temporal region of ichthyosaurian skull between basalExpand
The origin of squamates revealed by a Middle Triassic lizard from the Italian Alps
Divergence time estimates show that lepidosaurs and most other diapsids originated before the Permian/Triassic extinction event, indicating that the Triassic was a period of radiation, not origin, for several diapsid lineages. Expand
The Enigmatic Marine Reptile Nanchangosaurus from the Lower Triassic of Hubei, China and the Phylogenetic Affinities of Hupehsuchia
It is found that four lineages of marine reptiles are recognized almost regardless of which of these features were included in the analysis: Hupehsuchia-Ichthyopterygia-Saurosphargidae clade, Thalattosauria, and Helveticosaurus, and the interrelationships among these four depended on the combination of aquatic adaptations to be included. Expand


Eel-like swimming in the earliest ichthyosaurs
The most complete specimen of the oldest known ichthyosaur, Chensaurus, is reported, representing a transition between the two body plans, and seems to be an evolutionary intermediate between the shorter-bodied terrestrial stock from which the group evolved, and advanced thunniform ICHthyosaurs. Expand
The affinities and ecology of Triassic ichthyosaurs
The resolution of the problem of ichthyosaurian affinities has been complicated and prolonged by an emphasis on the morphology of Jurassic ichthyosaurs, some 30 to 40 m.y. younger than the earliestExpand
Hupehsuchus, an Enigmatic Aquatic Reptile from the Triassic of China, and the Problem of Establishing Relationships
The difficulty in determining the relationship of the Hupehsuchia may be attributed to the limited knowledge of the fossil record of diapsid reptiles in the late Permian and early Triassic, as well as the great amount of convergence exhibited by secondarily aquatic reptiles. Expand
The importance of the critical fossils seems to reside in their relative primitive‐ness, and the simplest explanation for their more conservative nature is that they have had less time to evolve. Expand
Turtles as diapsid reptiles
The result robustly supports the diapsid affinities of turtles, and so requires reassessment of the use of turtles as 'primitive' reptiles in phylogenetic reconstruction, and illustrates the difficulties of treating groups that have extant members with peculiar morphologies that mask phylogenetic affinity. Expand
An ichthyosaur skull from the Cretaceous of Wyoming
An ichthyosaur skull from the Mowry Shale of Wyoming--the only good ichthyosaur skull so far known from the Cretaceous--is described and figured. Study of the well-preserved temporal region leads toExpand
A case against a diapsid origin of the Ichthyosauria
The case for the diapsid origin of ichthyosaurs made by TARSITANO (1982,1983) is revisited. The skull on which TARSITANO'S original observations and hypotheses were mainly based is rediscussed andExpand
Reptile relationships turn turtle⃛
The data are corrected and reanalysed, and it is found that Rieppel and deBraga's data actually support, rather than challenge, the traditional view. Expand
Osteology of the Reptiles
This update is designed to give, in outline form, an account of the nature of the skeletal system of numerous reptile types both living and extinct. Expand
Interpretation of tectonically deformed fossils
Abstract Taxonomic information can be recovered from tectonically deformed fossils by analysing the strain and then restoring the fossils to their original shapes. Trilobites and graptolites are usedExpand