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The affinities of Liassic and later ichthyosaurs
... The Lower Lias ichthyosaurs in the Moore Collection had (and many still have) chalk numbers on the matrix, but were assigned temporary accession numbers when they were moved to the AC-NMW (Table 1; AC-NMW archives). Appleby (1979) subsequently used the temporary numbers in his publication that erected a new genus, Protoichthyosaurus, but we are not aware of the temporary numbers appearing elsewhere in the paleontological literature. The BRLSI register shows a break in the numbering from M3549 to M3581, with a note in Pickford's handwriting: "use these reg numbers for the Ichthyosaurs from the Moore Coll. ...
... Ichthyosaurus, Protoichthyosaurus, Leptonectes, and Temnodontosaurus. Taxonomic identifications were taken from the literature when the specimen was referred to a genus or species (e.g., Appleby, 1979;McGowan, 1989, and determined by JAM and DRL when they were not. We have opted to discuss the specimens by genus rather than in numerical order by accession number. ...
... We have opted to discuss the specimens by genus rather than in numerical order by accession number. The collection includes the holotype and paratypes of Protoichthyosaurus prostaxalis Appleby, 1979, as well as the holotype and only specimen of Ichthyosaurus prosostealis Appleby, 1979, a species of questionable validity . Most importantly, the collection provides several skeletons, some nearly complete, of each genus, facilitating comparisons to each other and to contemporaneous taxa. ...
Charles Moore (1815-1881) amassed a large, scientifically significant collection of fossils from southwestern England and displayed them in a public museum at the Bath Royal Literary and Scientific Institution. The collection included more than two dozen slab mounts of nearly complete or partial skeletons of Lower Lias (Lower Jurassic) ichthyosaurs, most of which are currently on loan to Amgueddfa Cymru-National Museum of Wales. Multiple specimens of Temnodontosaurus, Leptonectes, Ichthyosaurus, and Protoichthyosaurus allow comparisons of different individuals within each genus and among genera. Although research on ichthyosaurs in the collection has increased in the last decade, the potential for additional studies of intraspecific variation, taphonomy, stratigraphy, and taxonomy still remains. The specimens are readily accessible thanks to a recent investment in specialized shelving, not mounted high on a wall nor behind glass. To aid with future research, a brief description of each specimen is provided herein.
... Recent work has shown that the Lower Jurassic genus Protoichthyosaurus Appleby, 1979, is valid and can be distinguished from the more common and better known genus Ichthyosaurus De la Beche and Conybeare, 1821, on the basis of a unique forefin . Without the presence of a forefin, determining the identification of an isolated skull or other elements of the postcranial skeleton as either Protoichthyosaurus or Ichthyosaurus can be difficult. ...
... The genus has two species: Protoichthyosaurus prostaxalis, first described by Appleby (1979), and P. applebyi, recently recognized by . Differences in skull morphology can distinguish the two species from each other and from species of Ichthyosaurus. ...
... Individual species of each genus, however, have unique combinations of characters that distinguish them from each other, and sometimes species can be more readily identified than the genus, thus allowing assignment to Ichthyosaurus or Protoichthyosaurus (see below). Appleby, 1979 Holotype─BRLSI M3553 (formerly B. 1963'5/OS), a partial skull, pectoral girdle, and both forefins, preserved in ventral view. ...
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.
... INTRODUCTION Appleby (1979) proposed a new Lower Jurassic genus of ichthyosaur, Protoichthyosaurus, based on an unusual forefin morphology that displayed both latipinnate and longipinnate characteristics, major subdivisions of the Ichthyosauria at the time (McGowan, 1972). The genus and Family Protoichthyosauridae were diagnosed by forefins displaying one of two morphologies: (1) three distal carpals and an anterior digital bifurcation in the forefin or (2) a supernumerary bone contacting the intermedium anteroproximally. ...
... The former, however, is distinctly different from Ichthyosaurus, with which Protoichthyosaurus has been synonymized (Maisch and Hungerb€ uhler, 1997). Appleby (1979) noted that although both genera have a digital bifurcation anterior to the primary axis of the forefin, Protoichthyosaurus has only three elements in the distal carpal row, whereas Ichthyosaurus has four (Fig. 1). ...
... Although not intended to be deceptive, this practice led to the notion that fins of Ichthyosaurus are more variable within an individual than is actually the case. Appleby (1979) must have been aware of the variation because his diagnosis specified that either the left or right fin have three distal carpals, the Protoichthyosaurus pattern, although he did not recognize the specimens as composites. The 'individual variation' caused by composite specimens with a forefin from each genus may have also led Maisch and Hun-gerb€ uhler (1997) to synonymize the two genera because the forefins were too variable, and thus unreliable, to distinguish the genera. ...
The validity of the parvipelvian ichthyosaur genus Protoichthyosaurus was evaluated by examining the type material and recently recognized specimens. Protoichthyosaurus has a wide forefin with at least five primary digits, an anterior digital bifurcation in the forefin, a humerus that is nearly equal in width distally and proximally, and a coracoid with well-developed anterior and posterior notches, features it shares with the more common genus Ichthyosaurus. Previously, Protoichthyosaurus was synonymized with Ichthyosaurus because of an incomplete understanding of forefin variation in the latter taxon. However, Protoichthyosaurus has several features in the forefin that distinguishes it from Ichthyosaurus, including the presence of three elements in the distal carpal row, a contact between distal carpal 3 and the ulnare, a bifurcation of distal carpal 2 to form two elements in the metacarpal row, the proximal element of the bifurcation nearly separating distal carpal 2 from distal carpal 3, distal carpal 3 separating the intermedium from contact with distal carpal 4, and the absence of digit V. A phylogenetic analysis confirms that Protoichthyosaurus is the sister taxon of Ichthyosaurus and is nested in Ichthyosauridae. We recognize two species, P. prostaxalis and P. applebyi, sp. nov., but not P. prosostealis. Protoichthyosaurus is unequivocally from the Hettangian but might be present in the Rhaetian to lower Sinemurian. The genus is geographically widespread across the U.K.
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Citation for this article: Lomax, D. R., J. A. Massare, and R. T. Mistry. 2017. The taxonomic utility of forefin morphology in Lower Jurassic ichthyosaurs: Protoichthyosaurus and Ichthyosaurus. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1361433.
... The species was recognized at more localities than I. communis (Owen 1840, p. 112), and was more common than I. communis at Somerset locations, whereas the reverse occurred at Dorset locations (Owen 1840;Lydekker 1889). McGowan (1974) synonymized I. intermedius with I. communis, although Appleby (1979), Maisch (1997) and Maisch & Matzke (2000a) disagreed. McGowan & Motani (2003) argued that the characters proposed to distinguish the species were too variable to be useful. ...
... McGowan (1974) concluded that these differences are too small to warrant a taxonomic distinction. Appleby (1979), however, disagreed, and argued that the high variation in relative skull size and the differences in the forefins were too great to be considered a single species. Recent work (Lomax & Massare 2017) has demonstrated that many of the Somerset specimens are a new species, I. somersetensis. ...
... McGowan (1974) acknowledged that forefin morphology was different between specimens from Somerset and Dorset, but attributed it to intraspecific variation over time. Appleby (1979) argued that these were valid species differences. The problem is complicated by the frequent incompleteness of the forefin (Fig. 4), especially in recognizing a second or third digital bifurcation; and by unrecognized composites in historical collections (Massare & Lomax 2016b). ...
Ichthyosaurus communis De la Beche & Conybeare, 1821 De la Beche, H. T. & Conybeare, W. D. 1821. Notice of the discovery of a new fossil animal, forming a link between the Ichthyosaurus and crocodile, together with general remarks on the osteology of the Ichthyosaurus. Transactions of the Geological Society of London, 5, 559–594.[CrossRef] [Google Scholar] and I. intermedius Conybeare, 1822 Conybeare, W. D. 1822. Additional notices on the fossil genera Ichthyosaurus and Plesiosaurus. Transactions of the Geological Society of London, 1, 103–123.[CrossRef] [Google Scholar] 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 I. 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.
... The genus Protoichthyosaurus was established by Appleby (1979), who recognized a unique forefin morphology. Unrecognized composite specimens and a rare co-ossification in Ichthyosaurus forefins that mimics the Protoichthyosaurus morphology led to a misunderstanding of the range of individual variation within Ichthyosaurus . ...
... Protoichthyosaurus prostaxalis Appleby, 1979 Diagnosis. From emended diagnosis in : Distinguished from P. applebyi by the following features: large, dorsoventrally tall triangular maxilla with a long anterior process that extends beyond nasals in lateral view; dorsoventrally short, Skull roof of Protoichthyosaurus but anteroposteriorly wide, almost rectangular, postorbital (anteroposteriorly narrow but dorsoventrally tall (crescentic) in P. applebyi); lacrimal dorsal process longer than anterior process (roughly equal in P. applebyi); postorbital makes up half or less of posterior orbit margin (makes up more than half in P. applebyi); rectangular squamosal with triangular process extending ventrally from the posteroventral edge (unknown in P. applebyi); robust humerus with small dorsal process that is centrally located and does not extend far down the shaft (plate-like dorsal process forms a narrow ridge in P. applebyi); and hindfin with three elements in distal tarsal (third) row (unknown in P. applebyi). ...
A previously unrecognized specimen of Protoichthyosaurus prostaxalis , LEICT G142.1991, from the Lower Jurassic of Barrow-upon-Soar, Leicestershire, UK, includes an almost complete three-dimensional skull that provides new information on the configuration of the skull roof. The position of the pineal foramen (between the frontals and the parietals) and an elongated internasal foramen in a depression along the midline of the nasals are clearly shown. The maxilla makes up a significant portion of the external naris ventral margin, an unusual character for the genus/species. This reflects intraspecific variation, not evidence of a new taxon. The specimen enables comparisons of skull roof morphology with Ichthyosaurus and Stenopterygius , two common Early Jurassic taxa. In particular, the position of the pineal foramen is similar to Stenopterygius , but distinguishes Protoichthyosaurus from Ichthyosaurus . The lack of a frontal–prefrontal contact and the posteriorly wide nasals distinguishes Protoichthyosaurus from Stenopterygius . We also present a revised reconstruction of the skull roof morphology of Ichthyosaurus . Three additional specimens of Protoichthyosaurus are referred to the genus: another partial skull, referred to P. prostaxalis , and two isolated forefins, identified by their unique morphology.
... In this paper, we use CT scanning of a large ichthyosaur skull along with careful examination of the original specimen to formally describe BMT 1955.G35.1. Based on this description we reassign the specimen to Protoichthyosaurus prostaxalis Appleby, 1979, a genus recently shown to be distinct from Ichthyosaurus based on multiple characters (Lomax, Massare & Mistry, 2017;Lomax & Massare, 2018). Furthermore, the studied specimen has an estimated maximum body length of 3.2-4 m, greater than any other known specimen of Protoichthyosaurus or Ichthyosaurus. ...
... More recently, Larkin et al. (2016) tentatively identified the specimen as Ichthyosaurus, based on available information at the time. Since then, a revised diagnosis of Ichthyosaurus has been published , along with a redescription of Protoichthyosaurus (Lomax, Massare & Mistry, 2017), a genus first described by Appleby (1979), which was later synonymized with Ichthyosaurus (Maisch & Hungerbühler, 1997). Lomax, Massare & Mistry (2017) provided an emended diagnosis of Protoichthyosaurus, which included several autapomorphies of the forefin. ...
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.
... Therefore, only elements of the forelimb, in which the humerus bears a distal facet for the intermedium (which was considered a unique feature of Brachypterygius at that time), were chosen as the holotype of the new species (Arkhangelsky, 1998). In the article of Efimov, attention was focused on the distal contact of the intermedium with one distal carpal ("longipinnate" type), which many researchers of the 20th century considered a taxonomically important "high-rank" character (e.g., Huene, 1922;McGowan, 1972;Appleby, 1979). Therefore, he compared the new taxon only with other "longipinnate" ichthyosaurs ("Leptopterygius", Temnodontosaurus, Stenopterygius, Platypterygius, and Plutoniosaurus), even though he noted that "a similar feature of the intermedium was previously recorded (Huene, 1956) only for the genus Brachypterygius from the Kimmeridgian of Northern (sic!) England, which, however, belongs to latipinnate superfamily" (Efimov, 1998, p. 82; translation from the original Russian version, as the published English translation is imprecise). ...
Many ichthyosaur researchers consider the Late Jurassic genera Grendelius and Brachypterygius synonymous, but do not take into account species of the genus Otschevia (synonym of Grendelius) described from Russia, which is partly due to their brief initial descriptions. We provide a detailed description and photographs of the bones of Grendelius pseudoscythicus and Grendelius zhuravlevi holotypes and compare them with the other species of the genus; several new specimens belonging to the genus Grendelius from European Russia are also described. Grendelius pseudoscythicus and G. zhuravlevi differ from each other and from the other species of the genus in the morphology of some cranial bones (quadrate and stapes), pectoral girdle,
and forelimbs, and they should be considered as valid species. Therefore, at least three species of the genus Grendelius were present in the Middle Russian Sea in the Middle Volgian. Some of the new specimens described in this paper differ from the known species, which suggests the presence of other species of the genus Grendelius in European Russia. Based on the available data, there is still insufficient evidence for synonymy between the genera Brachypterygius and Grendelius.
... In the studied specimen, however, there is a very small anterior bifurcation from distal carpal 2 in the metacarpal (fourth) row, thus bringing the total digit count to four. The only ichthyosaur having three elements in the third row with a bifurcation of distal carpal 2 is Protoichthyosaurus (Appleby, 1979;Lomax et al. 2017). In Protoichthyosaurus, however, the first element of the bifurcation is always proximodistally long, hexagonal and is always positioned between distal carpal 2 and distal carpal 3 where it almost separates them. ...
Composite fossils can distort our evaluation of the morphology and variation of a species if unrecognised or misidentified. Many Early Jurassic ichthyosaurs collected during the 19th century have been identified as composites, but the problem is not restricted to historic specimens. More recently collected material, including some specimens for sale on the fossil market, are also composites or have been modified. One such specimen (RNHM F5672), said to be from the Lower Lias of Dorset, England, appears to be an almost complete skeleton, but comprises at least three individuals along with a carefully reconstructed and carved skull, and an apparent replica coracoid and forefin. The forefin, if a cast of a genuine specimen, shows a unique set of characters not previously observed in any ichthyosaur. Additionally, various caudal and dorsal vertebrae of indeterminate ichthyosaurs were pieced together to give the appearance of a complete , articulated vertebral column. One authentic block, containing the hindfins, the pelvic girdle and some ribs, can be assigned to Ichthyosaurus conybeari, based on characters of the hindfins. It comes from the Lower Jurassic (Sinemurian) of the Charmouth-Lyme Regis area, Dorset. The entire 'skeleton' is set into a large block of matrix which is from the Lower Jurassic (Toarcian) Posidonia Shale of Holzmaden, Germany. Therefore, this fossil represents a composite of material from multiple specimens belonging to perhaps two different genera, collected from two different countries and from two different geological stages.
... Pickford made crates for each one, and they were sent to Cardiff for study and conservation. This was to result in a paper describing two new species of the genus Protoichthyosaurus (Appleby 1979), with the two holotypes and two paratypes being part of this collection. The National Museum of Wales agreed to house all the specimens for safe keeping for the duration of his research, keeping them stacked in several piles on the floor of the Palaeontology store. ...
Amgueddfa Cymru - National Museum of Wales (AC-NMW) holds a large collection of fossil ichthyosaurs on long term loan from the Bath Royal Literary and (1814-1881) in the mid-19th Century, mostly from Somerset, although it now also includes Lyme Regis specimens obtained from Mary Anning and previously donated to the BRLSI. Historically they have suffered many moves, and sometimes less than ideal storage, so in 2017, a new shelving system was acquired by the AC-NMW to maximize safe access whilst minimizing damage to the specimens. This paper has been expanded from a poster displayed at the seminar 'Making the most of a move' in Dublin, November 2017.
... Ces caractères permettent de l'attribuer aux Ichthyosauridae. La rangée des carpes présente quatre éléments, une caractéristique propre au genre Ichthyosaurus, contrairement au genre Protoichthyosaurus qui n'en a que trois (Appleby, 1979 ; (Agassiz, 1837) ; J, étiquette correspondante. K-L, Dorsetichthys bechei (Agassiz, 1837) ; L, étiquette correspondante. ...
The Boutillier Collection, which is housed at the University of Caen Normandy (France), is one of the few palaeontological collections built up in Normandy during the 19th century to be still preserved, at least in part. This article presents a first biography of Louis Boutillier and details the historical context in which his collection was built up. A first review of the Mesozoic vertebrates kept in this collection is proposed. Alongside a set of pieces from renowned foreign sites such as Lyme Regis in England, Holzmaden in Germany or Sunderland in the United States, this inventory highlights several French regional faunal ensembles, some of which come from formations that are today inaccessible. The specimens in the Boutillier collection come in particular from the Upper Muschelkalk (Upper Anisian/Ladinian) limestones of the Lunéville area in Lorraine or Oberbronn in Alsace, the Lower Toarcian Argiles à Poissons of La Caine, the Callovo-Oxfordian formations of the Calvados coast, the Kimmeridgian Marnes et Calcaires à Nanogyra virgula of Alligny-Cosne, the Kimmeridgian clays of Le Havre region, the Upper Jurassic formations of Boulogne-sur-Mer, the Albian formations of Eastern France and the Upper Cretaceous Chalk of Normandy and the Paris region. Among the most remarkable pieces that have been found in the collection is one of the vertebrae of the “Alligny Megalosaurus”, discovered by the physician and naturalist Charles Roussel de Vauzème and reported by Paul Gervais in 1848, which turned out to belong to a colymbosaurine plesiosaur. It was also rediscovered one of the first remains of pterosaurs found in France. This specimen, found by Louis Boutillier himself in the Kimmeridgian of the Le Havre region, was first reported by Gustave Lennier in a book published in 1868. -- Résumé -- La collection Boutillier conservée à l'Université de Caen Normandie (France) fait partie des rares collections paléontologiques consti-tuées en Normandie au XIX e siècle à avoir été sauvegardées, tout au moins en partie, jusqu'à aujourd'hui. Cet article présente une pre-mière biographie de Louis Boutillier et détaille le contexte historique dans lequel sa collection fut constituée. Une première revue des vertébrés mésozoïques qu'elle contient est proposée. A côté d'un ensemble de pièces provenant de sites étrangers réputés comme Lyme Regis en Angleterre, Holzmaden en Allemagne ou Sunderland aux Etats-Unis, cet inventaire met en évidence plusieurs ensembles fau-niques régionaux français, dont certains proviennent de formations aujourd'hui difficiles d'accès, voire inaccessibles. Les spécimens de la collection Boutillier proviennent notamment des calcaires du Muschelkalk supérieur (Anisien supérieur/Ladinien) de la région de Lunéville en Lorraine ou d'Oberbronn en Alsace, des Argiles à Poissons du Toarcien inférieur de La Caine, des formations cal-lovo-oxfordiennes des côtes du Calvados, des Marnes et Calcaires à Nanogyra virgula du Kimméridgien d'Alligny-Cosne, des argiles kimméridgiennes de la région du Havre, des formations du Jurassique supérieur de Boulogne-sur-Mer, des formations albiennes de l'est de la France et de la craie du Crétacé supérieur de Normandie et de la région parisienne. Parmi les pièces les plus remarquables qui ont pu être retrouvées est à signaler une des vertèbres du « mégalosaure d'Alligny », découvertes par le médecin et naturaliste Charles Roussel de Vauzème et signalées par Paul Gervais en 1848, qui s'avèrent appartenir à un plésiosaure colymbosaurine. A été également redécouvert un des premiers restes de ptérosaures trouvés en France, identifiable de manière incontestable. Ce spécimen, trouvé par Louis Boutillier en personne dans le Kimméridgien de la région du Havre, fut signalé pour la première fois par Gustave Lennier dans un ouvrage publié en 1868.
... Although a large portion of the forefin is reconstructed, it is clear that the intermedium contacts both distal carpals 3 and 4. This contact rules out any suggestion of the specimen being an example of Protoichthyosaurus (Appleby 1979;Lomax and Massare in press). ...
A formerly undescribed Ichthyosaurus specimen from the collection of the Niedersächsisches Landesmuseum (Lower Saxony State Museum) in Hannover, Germany, provides valuable new information. The skeleton was collected from the Lower Jurassic strata (lower Hettangian, Blue Lias Formation) of Doniford Bay, Somerset, UK. However, the specimen is a composite as almost the entire tail has been added and other parts are reconstructed. Regardless of the incomplete preservation, the estimated total length of this individual, based on the skull and precaudal length, is between 300 and 330 cm and it is thus the largest unequivocal example of the genus Ichthyosaurus. Cranial and postcranial characters, specifically from the maxilla, lacrimal, jugal, the humerus, and the ilium justify a referral to I. somersetensis. A fork-like shape of the proximal end of the ilium is unusual and has not been reported for any species of Ichthyosaurus. Likewise the presence of four elements in the third row of the hindfin, indicated by the presence of a bifurcation is novel for the species and has wider implications for the taxonomic utility of hindfins within the genus. The specimen also bears an embryo, which is only the third embryo known for Ichthyosaurus and the first to be positively identified to species level.
... g. MERRIAM, 1908, KuHN, 1934, VON HuENE, 1956, RoMER, 1956, APPLEBY, 1979, MAZIN, 1982, CARROLL, 1988, CALLAWAY & BRINKMAN, 1989). KuHN (1934, p. 21-24) united Mixosaurus, Phalarodon, and Grippia in the family Mixosauridae, but did not elaborate. ...
New material of Phalarodon from the Middle Triassic Sulphur Mountain Formation of Wapiti Lake, British Columbia, includes cranial elements with complete upper and lower dentitions, and associated postcranial material. Skulls with a Phalarodon-like dentition are associated with a Mixosaurus-type of postcranium, demonstrating that Pbalarodon fraasi is the junior synonym of Mixosaurus nordenskioeldi. The skull, however, differs significantly from that of the type species, Mixosaurus cornalianus, indicating that this species is not referable to the genus Mixosaurus. It is therefore referred to Pbalarodon MERRIAM (1910). Phalarodon nordenskioeldi is more derived than Mixosaurus cornalianus in the following characters: 1) anterior end of both jaws edentulous, 2) posterior crushing teeth laterally compressed domes, elongate anteroposteriorly, 3) skull with large parietal crest, extending forward between the orbits, 4) sixth digit present in the manus. It is more primitive than M. cornalianus in having multiple rows of teeth on the maxilla, in having teeth with open, plicated roots and in retaining the transverse flange on the pterygoid. A well preserved stapes confirms that this element was primitively long and slender in the Ichthyosauria. The cheek region in Phalarodon is formed by two large bones traditionally identified as the quadratojugal and the squamosal. The homologies of these elements are reinterpreted as the squamosal and the supratemporal.
... This leads to a "latipinnate" condition, which is exclusive for P. hauthali and differs from Caypullisaurus, P. platydactylus, P. ochevi, P. hercynicus, Maiaspondylus, P. australis, P. campylodon, and P. bedengensi. In these taxa, the intermedium has a single distal articular facet ("longipinnate" condition) (Appleby 1979;McGowan 1972). However, there are some differences that do not allow an unequivocal referral of CPAP-2011-0019 to P. hauthali: (1) the humerus of P. hauthali has a third distal facet for the anterior extrazeugopodial element, which is absent in CPAP-2011-0019; (2) the proximal margin of the humerus is straight in CPAP-2011-0019, but deeply convex in P. hauthali; according to Johnson (1977), this feature of the humerus in P. hauthali could be a sign of the mature state of the animal (Fernández and Aguirre-Urreta 2005); (3) CPAP-2011-0019 has one preaxial row and three or even four postaxial rows, while P. hauthali has at least three preaxial rows (specimen MLP 70-I-30-1); (4) the intermedium of CPAP-2011-0019 has a distal facet for the articulation with distal carpal four, which is twice as long as the distal articular facet for distal carpal three; in the intermedium of P. hauthali, these facets are of the Metacarpal three 21 12 ...
... Identification: Because the taxonomy of Early Jurassic ichthyosaurs is based traditionally on phenetic ratios and forefin architecture (McGowan, 1974a(McGowan, , b, 1979Appleby, 1979;McGowan & Motani, 2003;, skull features have received comparatively less attention (but see McGowan, 1973;Maisch, 1997bMaisch & Hungerbühler, 1997;Maisch & Matzke, 2002;Motani, 2005;). Ac- cordingly, autapomorphic cranial features have rarely been identified. ...
The real nature of marine reptile fossils found in England between the 1700s and the beginning of the 1900s remained enigmatic until Mary Anning’s incredible fossil discoveries and their subsequent study by eminent English and French scientists. In 1820, Georges Cuvier acquired several ichthyosaur specimens found by Mary Anning, now kept or displayed in the Palaeontology Gallery of the Muséum National d’Histoire Naturelle (MNHN) in Paris. Four years later, Cuvier obtained a plesiosaur specimen from Mary Anning, only the second ever discovered. Cuvier was fascinated by these fossils and their study allowed him to apply his comparative anatomical method and to support his catastrophist theory. We have re-examined these important specimens from a historical point of view, and describe them here taxonomically for the first time since Cuvier’s works. The Paris specimens belong to two different ichthyosaur genera (Ichthyosaurus and Leptonectes) and one plesiosaur genus (Plesiosaurus).
... This leads to a " latipinnate " condition, which is exclusive for P. hauthali and differs from Caypullisaurus, P. platydactylus, P. ochevi, P. hercynicus, Maiaspondylus, P. australis, P. campylodon, and P. bedengensi . In these taxa, the intermedium has a single distal articular facet ( " longipinnate " condition) (Appleby 1979; McGowan 1972). However, there are some differences that do not allow an unequivocal referral of CPAP-2011-0019 to P. hauthali: (1) the humerus of P. hauthali has a third distal facet for the anterior extrazeugopodial element, which is absent in CPAP-2011-0019; (2) the proximal margin of the humerus is straight in CPAP-2011-0019, but deeply convex in P. hauthali ; according to Johnson (1977), this feature of the humerus in P. hauthali could be a sign of the mature state of the animal (Fernández and Aguirre-Urreta 2005); (3) CPAP-2011-0019 has one preaxial row and three or even four postaxial rows, while P. hauthali has at least three preaxial rows (specimen MLP 70-I-30-1); (4) the intermedium of CPAP-2011-0019 has a distal facet for the articulation with distal carpal four, which is twice as long as the distal articular facet for distal carpal three; in the intermedium of P. hauthali, these facets are of the same length. ...
Expeditions to the Tyndall Glacier (Torres del Paine National Park, South Chile) in 2009 and 2010 recov-ered an articulated ichthyosaurian forefin that displayed traits consistent with Platypterygius. The combination of features observed in this forefin has not been observed in other Platypterygius species, i.e.: (1) one preaxial row and three or even four postaxial rows; (2) the distal articulation of ulna with metacarpal five; (3) the shape and the articula-tion context of distal carpal three, metacarpal three and four; (4) the hexagonal shape of the intermedium; and (5) the presence of only two distal articular facets on the humerus. Nevertheless, the forefin is not referred to a new species, because it was found isolated and no other diagnostic skel-etal elements are present. The forefin presented here is the first complete and articulated forefin of a Platypterygius from the South Pacific margin, and together with other ichthyosaurs from the Tyndall area, represents the southern-most occurrence of Early Cretaceous ichthyosaurs in the Americas.
Switzerland is an ichthyosaur country: it has a rich record of marine reptile fossils, particularly the fish-shaped ichthyosaurs, and the according research. Here, we provide an overview over the 12 or more genera and at least 13 species plus numerous fragmentary remains of ichthyosaurs from the Triassic to the Cretaceous that have been discovered in twelve cantons thus far, of which four species are based on Swiss holotypes. This wealth of ichthyosaur species can be explained by their abundance in the Middle Triassic conservation deposits (Konservat Lagerstätte) of Monte San Giorgio, as well as occasional discoveries in strata of Middle Triassic to Early Cretaceous age. The moderate abundance of outcrops in reasonable conditions in combination with the long history of palaeontological research in Switzerland explains this good fossil record. In addition to this unique overview, we provide more data for further studies and update the knowledge of these taxa.
In Part 2, ichthyosaur taxa of the Late Jurassic are described; three taxa are considered valid: Brachypterygius extremus, Nannopterygius enthekiodon, and Macropterygius sp. indet. (Ichthyosauria: Ophthalmosauridae). These taxa are best represented from the Kimmeridge Clay Formation. Grendelius mordax is rejected as a junior subjective synonym of Brachypterygius extremus based on skull and limb morphology. Material referred to Macropterygius is too incomplete to erect a species, but is considered different enough to retain the genus as separate. Ichthyosaurus aequalis, Ichthyosaurus dilatatus, Ichthyosaurus ovalis, Ichthyosaurus thyreospondylus, and Ichthyosaurus trigonus are considered nomina dubia. Ichthyosaurus advena, Ichthyosaurus chalarodeirus, Ichthyosaurus hygrodeirus, and Ichthyosaurus megalodeirus are considered nomina nuda. Comparisons are drawn with other ichthyosaur taxa, focusing particularly on Neoichthyosauria and Ophthalmosauridae. Evidence is presented for Ophthalmosaurus in the Kimmeridge Clay Formation, but the material is not complete enough to be certain of its specific affinities. Ophthalmosaurus icenicus and Ophthalmosaurus natans are considered separate species, but within the same genus based on several shared autapomorphies. However, re-evaluation of the material of Ophthalmosaurus natans is required.
Les ichtyosaures du jurassique moyen et supérieur britannique. 2ème Partie. Brachypterygius, Nannopterygius, Macropterygius et Taxa invalida
RÉSUMÉ
Dans la 2ème partie, les taxons d’ichtyosaures du jurassique supérieur sont décrits: trois taxons sont considérés valides: Brachypterygius extremus, Nannopterygius enthekiodon, et Macropterygiu sp. indet. (Ichthyosauria: Ophthalmosauridae). Ces taxons sont mieux représentés dans la formation du Kimmeridge Clay. Grendelius mordax est abandonné comme synonyme subjectif plus recent de Brachypterygius extremus sur la base de la morphologie du crâne et des membres. Le matériel identifié comme Macropterygius est trop incomplet pour l’érection d’une espèce nouvelle, mais est considéré suffisamment différent pour séparer le genre. Ichthyosaurus aequalis, Ichthyosaurus dilatatus, Ichthyosaurus ovalis, Ichthyosaurus thyreospondylus, et Ichthyosaurus trigonus sont traités comme nomina dubia. Ichthyosaurus advena, Ichthyosaurus chalarodeirus, Ichthyosaurus hygrodeirus, et Ichthyosaurus megalodeirus sont traités comme nomina nuda. Des comparaisons sont effectuées avec d’autres taxons d’ichtyosaures, et en particulier Neoichthyosauria et Ophthalmosauridae. Ophthalmosaurus est présent dans la formation de Kimmeridge Clay, mais le matériel n’est pas suffisamment complet pour une affinité spécifique précise. Ophthalmosaurus icenicus et Ophthalmosaurus natans sont considérés comme étant des espèces séparées, mais appartenant au même genre sur la base de plusieurs autapomorphies communes. Cependant, une réévaluation du matériel d’Ophthalmosaurus natans est nécessaire. [Translation by Yves Candela.]
Ichthyosaurier des britischen Mittel- und Oberjura. Zweiter Teil. Brachypterygius, Nannopterygius, Macropterygius und Taxa invalida
ZUSAMMENFASSUNG
In Teil 2 werden Ichthyosaurier Taxa des späten Jura beschrieben; drei Taxa werden als zulässig betrachtet: Brachypterygius extremus, Nannopterygius enthekiodon, und Macropterygius sp. indet. (Ichthyosauria: Ophthalmosauridae). Diese Taxa werden am vollständigsten in der Kimmeridge Tonformation repräsentiert. Basierend auf der Morphologie des Schädels und der Extremitäten wird Grendelius mordax als jüngeres subjektives Synonym von Brachypterygius extremus zurückgewiesen. Funde, die Macropterygius zugerechnet werden, sind zu unvollständig, um eine eigene Spezies zu beschreiben. Sie werden jedoch als andersartig genug angesehen, um den Status einer eigenen Gattung beizubehalten. Ichthyosaurus aequalis, Ichthyosaurus dilatatus, Ichthyosaurus ovalis, Ichthyosaurus thyreospondylus, und Ichthyosaurus trigonus werden als Nomina dubia betrachtet, Ichthyosaurus advena, Ichthyosaurus chalarodeirus, Ichthyosaurus hygrodeirus, und Ichthyosaurus megalodeirus werden als Nomina nuda betrachtet. Vergleiche, welche sich besonders auf Neoichthyosauria und Ophthalmosauridae konzentrieren, werden mit anderen Ichthyosaurier Taxa gezogen. Hinweise für Ophthalmosaurus in der Kimmeridge Tonformation werden präsentiert, doch die Funde sind nicht vollständig genug, um eine spezifische Verwandtschaft sicherstellen zu können. Ophthalmosaurus icenicus und Ophthalmosaurus natans werden als unterschiedliche Spezies aufgefasst, die jedoch aufgrund gemeinsamer Autapomorphien zur selben Gattung gezählt werden können. Jedoch ist eine Neubewertung der Ophthalmosaurus natans Funde notwendig. [Translated by David Schlaphorst.]
Ихтиозавры британского среднего и верхнего юрского периода. Часть вторая: Brachypterygius, Nannopterygius, Macropterygius, и Taxa invalida
РЕЗЮМЕ
Во второй части описываются таксоны ихтиозавров поздней юры. Три таксоны считаются действительными: Brachypterygius extremus, Nannopterygius enthekiodon, и Macropterygius sp. indet. (Ichthyosauria: Ophthalmosauridae). Все эти таксоны лучше всего представляются в форме глины Киммередж. Grendelius mordax отклоняется как младший субъективный синоним Brachypterygius extremus на основе морфологии черепа и конечностей. Материал, относящийся к Macropterygius является слишком неполным, чтобы составить вид, но считается достаточно разным, чтобы сохранить род отдельным. Ichthyosaurus aequalis, Ichthyosaurus dilatatus, Ichthyosaurus ovalis, Ichthyosaurus thyreospondylus, и Ichthyosaurus trigonus считаются nomina dubia. Ichthyosaurus advena, Ichthyosaurus chalarodeirus, Ichthyosaurus hygrodeirus, и Ichthyosaurus megalodeirus считаются nomina nuda. Сравниваются с другими таксонами ихтиозавра, особенно с Neoichthyosauria и Ophthalmosauridae. Представляется доказательство о Ophthalmosaurus в форме глины Киммередж, но материал не является достаточно полным, чтобы быть уверенным в его видовом сродстве. Ophthalmosaurus icenicus и Ophthalmosaurus natans считаются отдельными видами, находящиеся в одном роде на основе некоторых общих автапоморфий. aОднако, требуются повторный анализ материала Ophthalmosaurus natans. [Translation by Anastasia Reynolds.]
ABSTRACT
The ichthyosaur material of the British Middle and Upper Jurassic is revisited and re-described. Three valid species are present: Ophthalmosaurus icenicus, Brachypterygius extremus, and Nannopterygius enthekiodon. Macropterygius sp. indet., with affinities to Platypterygiinae, formerly referred to Ichthyosaurus trigonus, is noted based on humeral material. Grendelius mordax is synonymized with Brachypterygius extremus. Ophthalmosaurus monocharactus is synonymized with Ophthalmosaurus icenicus. Ichthyosaurus advena, Ichthyosaurus chalarodeirus, and Ichthyosaurus hygrodeirus are rejected as nomina nuda, while Ichthyosaurus aequalis, Ichthyosaurus dilatatus, Ichthyosaurus ovalis, Ichthyosaurus thyreospondylus, and Ichthyosaurus trigonus are rejected as nomina dubia. The majority of remains are from the Oxford Clay and Kimmeridge Clay formations, but ichthyosaur material is found throughout the Aalenian–Portlandian interval. The affinities of Baptanodon are considered, and it appears to represent a species of Ophthalmosaurus: Ophthalmosaurus natans. Diagnostic characters are considered important to separate this from Ophthalmosaurus icenicus at only the species level. The palaeobiogeographical distribution of Ophthalmosauridae suggests an early Middle Jurassic origin in the south-eastern Pacific Ocean, with a rapid spread to the Tethys Ocean by the Bathonian.
Les ichtyosaures du jurassique moyen et supérieur britannique.
RÉSUMÉ
Le matériel d’ichtyosaure du Jurassique moyen et supérieur de la Grande-Bretagne est examiné et décrit de nouveau. Trois espèces valides sont présentes: Ophthalmosaurus icenicus, Brachypterygius extremus et Nannopterygius enthekiodon. Macropterygius sp. indet., avec des affinités de Platypterygiinae, autrefois dénommé Ichthyosaurus trigonus, est reconnu sur la base du matériel huméral. Grendelius mordax devient synonyme de Brachypterygius extremus. Ophthalmosaurus monocharactus devient synonyme d’Ophthalmosaurus icenicus. Ichthyosaurus advena, Ichthyosaurus chalarodeirus et Ichthyosaurus hygrodeirus sont rejetés comme nomina nuda. Ichthyosaurus aequalis, Ichthyosaurus dilatatus, Ichthyosaurus ovalis, Ichthyosaurus thyreospondylus et Ichthyosaurus trigonus sont rejetés comme nomina dubia. La plupart des restes proviennent des formations Oxford Clay et Kimmeridge Clay, mais on trouve du matériel d’ichtyosaure dans tout l’intervalle Aalénien–Portlandien. Les affinités de Baptanodon sont envisagées, et il semble représenter une espèce d’Ophthalmosaurus, à savoir Ophthalmosaurus natans. Les caractères diagnostiques sont considérés importants au niveau de l’espèce seulement pour le séparer d’Ophthalmosaurus icenicus. La distribution paléogeographique d’Ophthalmosauridae suggère une origine au début du Jurassique moyen dans le sud-est de l’océan Pacifique, avec l’extension rapide de l’océan Téthys au Bathonien. [Translation by Yves Candela.]
Ichthyosaurier des britischen Mittel- und Oberjura.
ZUSAMMENFASSUNG
Das Material über Ichthyosaurier des britischen Mittel- bis Spätjura wird hier erneut aufgegriffen und beschrieben. Es gibt drei gültige Arten: Ophthalmosaurus icenicus, Brachypterygius extremus und Nannopterygius enthekiodon. Macropterygius sp. indet., das Ähnlichkeiten zu den Platypterygiinae aufweist und zuvor Ichthyosaurus trigonus genannt wurde, wird auf Basis von Oberarmknochenmaterial vermerkt. Grendelius mordax wird mit Brachypterygius extremus synonymisiert. Ophthalmosaurus monocharactus wird mit Ophthalmosaurus icenicus synonymisiert. Ichthyosaurus advena, Ichthyosaurus chalarodeirus und Ichthyosaurus hygrodeirus werden als nomina nuda abgelehnt. Ichthyosaurus aequalis, Ichthyosaurus dilatatus, Ichthyosaurus ovalis, Ichthyosaurus thyreospondylus und Ichthyosaurus trigonus werden als nomina dubia abgelehnt. Die grosze Mehrheit an Resten stammt aus den Oxford und Kimmeridge Tonerde Formationen, doch Ichthyosaurier werden in der gesamten Zeitspanne des Aalenium bis Portlandium gefunden. Die Ähnlichkeiten bei Baptanodon werden berücksichtigt und es scheint, dass diese eine Art von Ophthalmosaurus darstellen: Ophthalmosaurus natans. Bestimmende Eigenschaften werden als wichtig erachtet, diese Art von Ophthalmosaurus icenicus ausschlieszlich auf der Spezies-Ebene abzugrenzen. Die paläobiogeografische Verteilung der Ophthalmosauridae lässt eine Herkunft aus dem südöstlichen pazifischen Ozean des frühen Mitteljuras, gefolgt von einer schnellen Ausbreitung gen Tethysmeer bis zum Bathonium vermuten. [Translation by David Schlaphorst.]
Ихтиозавры среднего и верхнего британского юрского периода.
РЕЗЮМЕ
В этой статьи останки ихтиозавров Британского среднего и верхнего юрского периода пересматриваются и снова описываются. Появляются три валидные виды: Ophthalmosaurus icenicus, Brachypterygius extremus и Nannopterygius enthekiodon. Macropterygius sp. indet. (раньше названный Ichthyosaurus trigonus), что является подобным группе Platypterygiinae, замечается в связи с плечевым образцом. Grendelius mordax приравнивается к Brachypterygius extremus. Ophthalmosaurus monocharactus приравнивается к Ophthalmosaurus icenicus. Ichthyosaurus advena, Ichthyosaurus chalarodeirus и Ichthyosaurus hygrodeirus отвергаются в качестве nomina nuda. Ichthyosaurus aequalis, Ichthyosaurus dilatatus, Ichthyosaurus ovalis, Ichthyosaurus thyreospondylus и Ichthyosaurus trigonus отвергаются в качестве nomina dubia. Большинство останков происходит из формаций глины Оксфордского и Киммериджского яруса, но останки ихтиозавров находятся по целому Ааленскому–Портландскому ярусу. Сходства рода Baptanodon рассматриваются и по-видимому является видом рода Ophthalmosaurus: Ophthalmosaurus natans. Определяющие характеристики считаются важными, чтобы различать его от Ophthalmosaurus icenicus только на уровне вида. Палеобиогеографическое распределение семейства Ophthalmosauridae указывает на происхождение на юго-востоке Мирового океана во время раннего среднего юрского периода, с последующим быстрым распространением на Тетис к Батскому ярусу. [Translation by Anastasia Reynolds.]
Ichthyosaurs were a highly successful group of marine reptiles that first appeared in the Early Triassic, around 248 million years ago, and became extinct about 90 million years ago, in the Late Cretaceous. They are often referred to as ‘swimming dinosaurs’, but they are not dinosaurs. They were fully aquatic marine tetrapods that lived in the seas, whilst their more famous counterparts, the dinosaurs, roamed the land (Fig. ). They achieved a world‐wide distribution, and well over a hundred species are known, with thousands of specimens having been found. Ichthyosaurs evolved similar body plans to sharks, dolphins and whales, and are great examples of convergent evolution.
The ichthyosaur material of the British Middle and Upper Jurassic referable to Ophthalmosaurus icenicus (Ichthyosauria: Ophthalmosauridae) is revisited and re-described; this is the most completely known post-Liassic British ichthyosaur. Much of this material derives from the Callovian Oxford Clay Formation, particularly from the Peterborough Area of Cambridgeshire, UK, deposited in the Leeds Collections. Pre-Callovian ichthyosaur remains are infrequent, incomplete, and non-diagnostic. Material referred to Ophthalmosaurus icenicus shows high variability in the extent of ossification. Based on examination of the type and referred material, Ophthalmosaurus monocharactus, and Ophthalmosaurus pleydelli are rejected as junior subjective synonyms of Ophthalmosaurus icenicus due to a lack of diagnostic characters and pathology of specimens. Ichthyosaurus megalodeirus is rejected as a nomen nudum and the type material is referred to Ophthalmosaurus icenicus. Ophthalmosaurus icenicus is considered a separate species from Ophthalmosaurus natans based on several autapomorphies, but requires re-evaluation of the material.
Based on a large part of a skeleton, a new species of the genus Otschevia (O. alekseevi) from the Volgian Stage (Dorsoplanites panderi zone) of the Volga Region near Ulyanovsk is described. The diagnoses of the family Undorosauridae, the subfamilies included in the family, and the genus Otschevia are emended.
Based on a large part of a skeleton, a new species of the genus Otschevia (O. alekseevi) from the Volgian Stage (Dorsoplanites panderi zone) of the Volga Region near Ulyanovsk is described. The diagnoses of the family Undorosauridae, the subfamilies included in the family, and the genus Otschevia are emended.
This chapter explores different aspects of Mixosaurus. The skulls of Mixosaurus cornalianus range in length from 185 mm to 270 mm. The skull is primitive in the relatively large size of the maxilla, the subequal lengths of the frontal and nasal bones, and the retention of the quadratojugal. Derived features are the large orbit, short cheek region, lacrimal excluded from the border of the external naris, very small upper temporal fenestra, elongated facial region, and exclusion of the postorbital from the temporal fenestra. The palate confirms the loss of the transverse flange of the pterygoid in mixosaurs as this is a derived character also belonging to M. cornalianus. There are only two bones in the posterior temporal region of ichthyosaurs, which is interpreted as being the squamosal and quadratojugal. The retention of the quadratojugal in the Mixosauridae would thus represent a primitive condition for ichthyosaurs. Neural spines of M. cornalianus are very high and straight-sided with dorsal tips sharply truncated. It has been found that the laterally flattened centra, plus the very tall anterior and middle caudal neural spines, and elongated chevrons, all serve to broaden the tail and produce an effective sculling organ.
The large ichthyosaur Leptopterygius disinteger v. HUENE, 1926 from the Lower Toarcian of Holzmaden is re-evaluated. It shows several autapomorphies of the cranial and postcranial skeleton and is consequently referred to a new genus, Suevoleviathan. The little known species Ichthyosaurus integer BRONN, 1844 is regarded as a possible second representative of Suevoleviathan, sharing its unique forefin structure. The phylogeny of post-Triassic ichthyosaurs is discussed. The reliability of forefin characters is questioned and a new phylogenetic argumentation scheme is based largely on cranial characters. Only two clades are clearly recognisable at present, the Leptonectidae n. fam., and Stenopterygiidae. Suevoleviathan can not yet be referred to any monophylum because of the lack of clear synapomorphies.
Postcranial axial anatomy of six Jurassic ichthyosaurs is described and used to define a generalized pattern of regional anatomy with four structural units (neck, trunk, tail stock, fluke). Functional interpretation of each unit predicts a generalized swimming mode that used a laterally compressed, laterally oscillating caudal fluke as the propulsive organ. Fluke displacement was accomplished by the undulation of a dorsoventrally compressed posterior tail stock acting on a stabilized anterior tail stock. The trunk was largely uninvolved in locomotion. Osteological predictors of postcranial flexibility in living aquatic axial locomotors are reviewed and used to identify the existence of a range of swimming styles within this generalized pattern among surveyed ichthyosaurs.
The study of the temporo-jugal region and of the fore fin of primitives Ichthyopterygia leads to some conclusions: the interpretation of A.S. Romer (1968) and C. Mc Gowan (1973) is confirmed; the Ichthyopterygia make a part of the Euryapsida which are re-defined and which derive from a diapsid level; the evolution of the fore fin disagrees with the latipinnate-longipinnate dichotomy. A phylogeny of the Ichthyopterygia is proposed.
Leptopterygius Huene, 1922, was erected for Leptopterygius tenuirostris, a fairly common long-snouted ichthyosaur from the English lower Liassic. Huene also referred eight other species to Leptopterygius, but these had little in common with L. tenuirostris, or with each another. These eight species have since been rejected, synonymized, or referred to other genera. Other species have also been referred to the genus since 1922, Leptopterygius having become something of a catchall for species not readily referred elsewhere. This unsatisfactory taxonomic situation is exacerbated by the recognition that the name Leptopterygius is preoccupied. A replacement name, Leptonectes, is proposed to replace Leptopterygius. Two species are referred to the new genus, L. tenuirostris (Conybeare, 1822), the type species, and Leptopterygius solei McGowan, 1993. The diagnostic features of the genus include the slenderness of the rostrum and mandible, and the wide distal expansion of the humeus, with its preaxial facet. The genus ranges from the uppermost Triassic to the Lower Jurassic.
A phylogenetic hypothesis for ichthyopterygians is proposed, based on a cladistic analysis of 105 discrete osteological characters coded for 27 ingroup and five outgroup taxa. The monophyly of Ichthyopterygia is established; at least nine characters support its basal node. The group contains two basal species and a clade formed by the Ichthyosauria and Grippidia. All ichthyosaurs from post-Triassic strata form an unnamed clade, which in turn forms the group Euichthyosauria (new taxon) with four Late Triassic genera. The traditional Shastasauridae is poly-phyletic, with Cymbospondylus forming the sistergroup of a clade containing mixosaurs, shastasaurs, and euichthyo-saurs. In addition, Californosaurus and Toretocnemus are not shastasaurs but euichthyosaurs. Two new generic names, Macgowania and Isfjordosaurus, are proposed.
Sufficient material has been assembled to restore the powerful pectoral girdle and large fore limbs of Platypterygius australis (M'Coy). A reasonable approximation to the line of action of dorsal and ventral muscles which principally affected the trim of the low-set fin-blades was along the middle of the fin. Increased tension brought the fin-blades nearer horizontal (to a diving position) and varying amounts of relaxation during forward movement allowed mainly water resistance to increase the tilt. The flexible blade edges were crucial in this. Unequal tension on the blades would have caused turning of the animal with whatever rapidity was desired. Allowing both fin-blades to rise together to stalling point could have checked the animal abruptly as it struck prey. Large relative and absolute increases in the portions of the coracoids adjacent to the median symphysis highlight the relative development of young individuals. Positive allometric growth in this area stopped quite suddenly as the animals approached 6 m total length, leaving only general size increase.
A re-examination of the fore-fin ofUtatsusaurus hataii leads to conclude that this Lower Triassic ichthyosaur possesses a particular tetradactyl limb. This type of limb is new among the Ichthyopterygia and can be interpreted as another attempt in the evolution of the ichthyosaurian paddle. av}AbbreviationsIGPS
Institute of Geology and Paleontology, Tohoku University, Sendai
KUJM
Department of Geology and Mineralogy, Kyoto University, Kyoto
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