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Leptopterygius tenuirostris and other long-snouted ichthyosaurs from the English Lower Lias
Abstract
One of the commonest ichthyosaurs from the English Lower Lias is the long-snouted species Leptopterygius tenuirostris, known principally from Street, Somerset. Because of the vagaries of preservation there are few complete skeletons, and the problem is exacerbated by the occurrence of composite specimens. The authenticity of a quarter of the specimens studied here is in doubt, and hence caution is needed when working on material from Somerset. The occurrence of a tail bend in L. tenuriostris is confirmed by the presence of wedge-shaped centra in the caudal region of several skeletons. The vertebral column was probably not steeply downturned, and may have been essentially straight in life. Eurhinosaurus, unusual for its abbreviated mandible, may be closely related to L. tenuriostris and is therefore of interest here. The suggestion that it occurs in the Upper Lias of England is confirmed. The contention that Eurhinosaurus lacked a tail bend is questioned because a wedge-shaped centrum has been identified in one specimen. -from Author
... 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. ...
... Leptonectes tenuirostris is by far the most common of the three species of the genus. The skull morphology is distinctive, characterized by a very long, thin rostrum, large orbit, and very short post-orbital region (McGowan, 1989;McGowan, 1996b;McGowan and Motani, 2003). The species has high morphologic variability and a long stratigraphic range (Maisch and Reisdorf, 2006). ...
... Leptonectes tenuirostris is easily distinguished from other Lower Jurassic ichthyosaurs by the humerus and forefin morphology. The humerus is much wider distally than proximally, with a narrow shaft; the radius is always notched, even in young individuals (Lomax and Massare, 2012); and the phalanges are typically round and widely spaced (McGowan, 1989). The other two species of Leptonectes, L. moorei and L. solei, are known from one and three specimens, respectively (McGowan, 1993;McGowan and Milner, 1999;Lomax and Massare, 2018a). ...
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.
... The wealth of Lower Jurassic ichthyosaur specimens in the UK has significantly contributed to our understanding of ichthyosaurs from this time interval (e.g. McGowan 1974McGowan , 1989aMcGowan , 1993McGowan , 1996Benton & Taylor 1984;Delair 1969). ...
... The tip of the snout extends beyond the tip of the mandible by approximately 4.5 cm, forming a noticeable overbite, although both the tip of the premaxilla and dentary may be missing À but probably no more than a centimetre (Fig. 2B). The overbite is not as extensive as in Eurhinosaurus and Excalibosaurus (McGowan 1989b, 1994a), but is more apparent than in some specimens of Leptonectes tenuirostris, which sometimes display an overbite (McGowan 1989a;Motani 1999b;McGowan & Milner 1999). Only one small tooth crown can be positively identified in the snout beyond the dentary. ...
... Ichthyosaur tooth shape varies from slender and sharply pointed to large and robust, although most have the form of small, slightly curved cones (Massare 1987). The needle-like crown morphology in the studied specimen is most similar to leptonectids but it is also comparable to the anteriormost teeth seen in Ichthyosaurus conybeari (McGowan 1989a(McGowan , 1996(McGowan , 2003 Maisch & Matzke 2000; pers obs: BGS 956). However, the large and relatively long maxillary teeth and the unusual morphology of the dentary teeth of the studied specimen are not found in those species. ...
Thousands of ichthyosaurs have been discovered from the rich Lower Jurassic deposits of the UK, with the majority collected from along the Lyme Regis-Charmouth area of the Dorset coast. Here, I describe a new leptonectid ichthyosaur, Wahlisaurus massarae gen. et sp. nov., based on a partial skull and an incomplete skeleton collected from the Lower Jurassic (Hettangian) of Nottinghamshire, England. Wahlisaurus can be referred to the Leptonectidae through the possession of an extremely slender and delicate snout, and a mandible shorter than snout which produces an overbite. This referral is supported by a phylogenetic analysis. The new taxon is distinguished from other ichthyosaurs through a unique combination of characters and autapomorphies of the pectoral girdle including the presence of both a scapular-coracoid foramen and a large and roughly ovoid coracoid foramen. A coracoid foramen has only previously been reported in the Triassic ichthyosaur Cymbospondylus. The peculiar coracoid morphology further highlights the taxonomic utility of coracoids in ichthyosaurs. The aforementioned features demonstrate that W. massarae cannot be referred to any currently recognised leptonectid. With the identification of W. massarae, it is the ninth Lower Jurassic ichthyosaur genus to be recognised worldwide, and it is the fifth documented in the lower Lias Group.
... The wealth of Lower Jurassic ichthyosaur specimens in the UK has significantly contributed to our understanding of ichthyosaurs from this time interval (e.g. McGowan 1974McGowan , 1989aMcGowan , 1993McGowan , 1996Benton & Taylor 1984;Delair 1969). ...
... The tip of the snout extends beyond the tip of the mandible by approximately 4.5 cm, forming a noticeable overbite, although both the tip of the premaxilla and dentary may be missing À but probably no more than a centimetre (Fig. 2B). The overbite is not as extensive as in Eurhinosaurus and Excalibosaurus (McGowan 1989b, 1994a), but is more apparent than in some specimens of Leptonectes tenuirostris, which sometimes display an overbite (McGowan 1989a;Motani 1999b;McGowan & Milner 1999). Only one small tooth crown can be positively identified in the snout beyond the dentary. ...
... Ichthyosaur tooth shape varies from slender and sharply pointed to large and robust, although most have the form of small, slightly curved cones (Massare 1987). The needle-like crown morphology in the studied specimen is most similar to leptonectids but it is also comparable to the anteriormost teeth seen in Ichthyosaurus conybeari (McGowan 1989a(McGowan , 1996(McGowan , 2003 Maisch & Matzke 2000; pers obs: BGS 956). However, the large and relatively long maxillary teeth and the unusual morphology of the dentary teeth of the studied specimen are not found in those species. ...
Thousands of ichthyosaurs have been discovered from the rich Lower Jurassic deposits of the UK, with the majority collected from along the Lyme Regis-Charmouth area of the Dorset coast. Here, I describe a new leptonectid ichthyosaur, Wahlisaurus massarae gen. et sp. nov., based on a partial skull and an incomplete skeleton collected from the Lower Jurassic (Hettangian) of Nottinghamshire, England. Wahlisaurus can be referred to the Leptonectidae through the possession of an extremely slender and delicate snout, and a mandible shorter than the snout which produces an overbite. This referral is supported by a phylogenetic analysis. The new taxon is distinguished from other ichthyosaurs through a unique combination of characters and autapomorphies of the pectoral girdle including the presence of both a scapular-coracoid foramen and a large and roughly ovoid coracoid foramen. A coracoid foramen has only previously been reported in the Triassic ichthyosaur Cymbospondylus. The peculiar coracoid morphology further highlights the taxonomic utility of coracoids in ichthyosaurs. The aforementioned features demonstrate that W. massarae cannot be referred to any currently recognized leptonectid. Wahlisaurus is the ninth Lower Jurassic ichthyosaur genus to be recognized worldwide, and the fifth documented in the Lower Lias Group.
http://zoobank.org/urn:lsid:zoobank.org:pub:EE500E11-66AB-43C8-BB59-F21654763241
... In fact, many were donated, not sold, to museums. However, researchers need to carefully examine historic specimens, especially complete or nearly complete skeletons to verify that it is a single individual (McGowan 1989(McGowan , 1990Taylor, 1989;Buttler and Howe, 2002;Massare and Lomax, 2014b). ...
... The matrix is covered by a patterned plaster wash, going up to the edge of the bones, with little of the matrix exposed. McGowan (1989) suggested that such a feature warrants close examination of the specimen. It looks authentic, although there is a discontinuity between the anterior block and the vertebral column immediately posterior to it, so that the neural spines and centra are upside down relative to the anterior skeleton (Fig. 18). ...
... Many of the composite and 'suspicious' specimens described herein are from the Thomas Hawkins and the Charles Moore collections, both among the largest private collections of ichthyosaurs amassed. McGowan (1989;1990) also found several composite specimens of Leptonectes tenuirostris from those collections. Specimens from those collections should initially be viewed with skepticism. ...
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.
... As there may be one or two cervical vertebrae missing, single-headed ribs would have begun at the 22 nd or 23 rd vertebra. McGowan (1989) gave a presacral count of 45 for L. tenuirostris, thus the change from doubleheaded to single-headed ribs on this specimen is at least 20 vertebrae, or almost half of the trunk length, anterior to the pelvis. This would be highly unusual for a parvipelvian ichthyosaur (e.g., Ichthyosaurus, Ophthalmosaurus; Buchholtz, 2001). ...
... A gradual increase in length of the centra can be seen from the anterior to the posterior of the preserved column, with perhaps a decrease in length beginning at the 35 th centrum (accounting for a missing atlas and axis but not for missing posterior dorsals). This would be anterior to the pelvis using McGowan's (1989) presacral count of 45 for Leptonectes tenuirostris. ...
... L. tenuirostris, however, has a similarly shaped ischium and pubis, and they can be fused (McGowan, 1989). The pelvis of L. moorei is unknown (McGowan and Milner, 1999). ...
A large but incomplete skeleton of an ichthyosaur (CAMSM J 13579) from Street, Somerset, in the Sedgwick Museum collection is associated with two embryos. The morphology of the pelvis and humerus indicate that the adult is Leptonectes. The elongated external naris, exclusion of the maxilla from the border of the external naris, notched radius of the embryo, and large size of the adult indicate that these specimens are most likely L. tenuirostris, a fairly common species from the Street location. The size of the head relative to the body in the more complete small skeleton (CAMSM J 35178), and its total length relative to the adult suggest that the small individuals are late term embryos rather than neonates.
... The complete ones are ascribed to the first digit, as they have clearly defined notches along their anterior margins. They are too small to represent the radius, which is usually notched in L. tenuirostris (McGowan, 1974McGowan, , 1989) whereas the rest of the phalanges of the forefin are rounded. Given that the radius was also notched as usually in leptonectids , It must thus be assumed, that the specimen had at least three notches along the leading edge of the forefin. ...
... Eurhinosaurus is characterised by the possession of a distinct overbite, i.e. an elongation of the upper jaw beyond the anterior end of the mandible. A slight overbite is also found as a variation in some of the English specimens of L. tenuirostris (McGowan, 1989), it is, however, never nearly as marked as in Eurhinosaurus. The Lower Liassic species E. costini (McGowan, 1986) from UK is characterised by a snout length which slightly exceeds the length of the entire mandible, which is never the case in L. tenuirostris. ...
... It is completely inconceivable that there was any marked overbite, and therefore the specimen not can be referred to Eurhinosaurus. The genus Leptonectes currently comprises three valid species , L. tenuirostris (Conybeare, 1822), the type species, which is known from the uppermost Rhaetian to Lower Sinemurian of UK (McGowan, 1974McGowan, , 1989) and the Lower Sinemurian of Southern Germany ( Maisch, 1999), L. solei (McGowan, 1993) from the Lower to Upper Sinemurian of UK and L. moorei (McGowan and Milner, 1999) from the Lower Pliensbachian of UK. L. solei is distinguished from the Swiss specimen by its much larger size (skull length exceeds 1000 mm) and much smaller orbit (orbital ratio 0.15 in the holotype). ...
A three-dimensional well-preserved ichthyosaur skull and parts of the postcranial skeleton are attributed to the species Leptonectes tenuirostris (Conybeare, 1822). It was found vertically embedded in Pliensbachian deposits representing three successive biozones (ibex to margaritatus Zone). The find is dated as early Late Pliensbachian (margaritatus Zone) by a rich ammonite and ostracod fauna. It is the first record of the genus Leptonectes from Switzerland and from the Late Pliensbachian. It is so far the best preserved and most complete ichthyosaur from this time interval worldwide. With diagnostic specimens known from the Rhaetian (Late Keuper) up to the early Late Pliensbachian (Middle Liassic), L. tenuirostris (Conybeare, 1822) has the most extensive stratigraphic range documented for any post-Triassic ichthyosaur so far.
... The tooth crowns are slightly recurved and markedly elongated: the apicobasal height / basal diameter ratio is 11 mm / 4 mm = 2.75 ( Figures 5, 6), very similar to some species of Stenopterygius (Maxwell, Fernández, et al., 2012), Hauffiopteryx (Maxwell and Cortés, 2020), and in leptonectids such as most species of Leptonectes (Fraas, 1892;Huene, 1922;McGowan, 1989McGowan, , 1993 (with the exception of Leptonectes moorei [McGowan and Milner, 1999]), Eurhinosaurus longirostris (Reisdorf et al., 2011), and Wahlisaurus massarae (Lomax, 2016) (Figure 6). This condition is clearly distinct from the stouter teeth seen in Temnodontosaurus spp. ...
... It should be stressed here that the presence of leptonectids in the Luxembourg-Trier basin (see also Godefroit, 1992) during the early Pliensbachian does not require the skeletal elements we describe here to (Table 1). Even if leptonectid neoichthyosaurians have been abundantly described (e.g., Fraas, 1891;Huene, 1922;McGowan, 1989McGowan, , 1993Godefroit, 1994;McGowan and Milner, 1999;Maisch and Matzke, 2003;Lomax, 2016), the details of the dental morphology of leptonectids are rarely documented, notably the concentric rings found towards the base of the tooth crown (but see Godefroit, 1994;Reisdorf et al., 2011;Lomax, 2016). These slightly concave rings, which we term here "annuli", clearly differ from the similarly positioned "enamel bands" of pliosaurids, which have a positive relief (Zverkov et al., 2018). ...
Despite abundant fossils, the quality of the fossil record of Early Jurassic marinereptiles strongly fluctuates with time and space. Pliensbachian strata have yielded veryfew marine reptile remains, especially outside of England, obscuring the evolution ofmarine reptiles during the middle part of the Early Jurassic. We report a new Pliensba-chian locality from Luxembourg that contains abundant marine fauna and ichthyosau-rian remains likely representing a single individual, composed of a partial snout, apossible surangular, two centra, and several ribs and gastralia. Ammonites and belem-nites place this locality within the Valdani-Luridum Ammonite subzones of the IbexAmmonite Zone, lower Pliensbachian. We assign the new ichthyosaur specimen to theclade Leptonectidae, using a combination of features from the snout and teeth. Thisspecimen indicates that large neoichthyosaurians were present in multiple places ofthe European archipelago in all stages of the Early Jurassic and suggests that the ich-thyosaurian faunae of western Europe remained essentially similar across the Sinemu-rian–Pliensbachian interval.
... Portions of the skull have multiple scalpel lines extending across it, which may have been intentional to provide 'detail' in the surface of the 'bones', but which do not match what is expected for an authentic specimen. The shape and structure of the skull suggest it was probably based on an original ichthyosaur skull, as the large eye and long snout are somewhat reminiscent of the Lower Jurassic genus Leptonectes (McGowan, 1989;1996), known primarily from Dorset and Somerset, England, and which would match the initial identification written on the label of the SMNS replica. ...
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.
... The external naris has a typical droplet shape ( Leptonectes (Maisch & Matzke, 2003;McGowan, 1989). The anterior extremity is thinner than the posterior border which is exclusively formed by a shallow notch of the lacrimal. ...
Parvipelvia is a major clade of ichthyosaurians that diversified during the Triassic-Jurassic transition. The interrelationships of early parvipelvians remain unclear and many genera are loosely diagnosed, such as Temnodontosaurus, an ecologically important genus from the Early Jurassic of Western Europe. One taxon concentrates many taxonomic issues: ‘Ichthyosaurus’ acutirostris was previously assigned to Temnodontosaurus and for which ‘Ichthyosaurus’ zetlandicus represents a junior synonym. We redescribe the holotype of ‘Ichthyosaurus’ zetlandicus (CAMSM J35176) and a new specimen probably attributable to this taxon (MNHNL TU885) from the Toarcian of Luxembourg. We find that Temnodontosaurus zetlandicus comb. nov. is a valid species that should be referred to the genus Temnodontosaurus, sharing a number of traits with Temnodontosaurus nuertingensis and Temnodontosaurus trigonodon, despite having a distinct cranial architecture. Our phylogenetic analyses under both implied weighting maximum parsimony and Bayesian inference recover T. zetlandicus as closely related to several species currently assigned to Temnodontosaurus. Species included in Temnodontosaurus form a polyphyletic yet well-clustered group among basal neoichthyosaurians, demonstrating that the monophyly of this genus needs to be thoroughly investigated.
... The external naris has a typical droplet shape ( Leptonectes (Maisch & Matzke, 2003;McGowan, 1989). The anterior extremity is thinner than the posterior border which is exclusively formed by a shallow notch of the lacrimal. ...
Parvipelvia is a major clade of ichthyosaurians that diversified during the Triassic-Jurassic transition. The interrelationships of early parvipelvians remain unclear and many genera are loosely diagnosed, such as Temnodontosaurus, an ecologically important genus from the Early Jurassic of Western Europe. One taxon concentrates many taxonomic issues: 'Ichthyosaurus' acutirostris was previously assigned to Temnodontosaurus and for which 'Ichthyosaurus' zetlandicus represents a junior synonym. We redescribe the holotype of 'Ichthyosaurus' zetlandicus (CAMSM J35176) and a new specimen probably attributable to this taxon (MNHNL TU885) from the Toarcian of Luxembourg. We find that Temnodontosaurus zetlandicus comb. nov. is a valid species that should be referred to the genus Temnodontosaurus, sharing a number of traits with Temnodontosaurus nuertingensis and Temnodontosaurus trigonodon, despite having a distinct cranial architecture. Our phylogenetic analyses under both implied weighting maximum parsimony and Bayesian inference recover T. zetlandicus as closely related to several species currently assigned to Temnodontosaurus. Species included in Temnodontosaurus form a polyphyletic yet well-clustered group among basal neoichthyosaurians, demonstrating that the monophyly of this genus needs to be thoroughly investigated.
... Within the genus Leptonectes, besides the type species L. tenuirostris Conybeare, 1822, there are two other valid species: L. solei McGowan, 1993and L. moorei McGowan and Milner, 1999(McGowan and Motani, 2003Lomax, 2016). Leptonectes tenuirostris is well known by several specimens (McGowan, 1989), and it has the longest stratigraphic range (probably from the Rhaetian up to the late Pliensbachian, Maisch and Reisdorf, 2006), and the widest geographic occurrence among leptonectids, including records from England (McGowan, 1996), Belgium (Godefroit, 1992, Germany (Maisch, 1999) and Switzerland (Maisch and Reisdorf, 2006). In contrast, L. solei and L. moorei are geographically restricted to Dorset (England), and stratigraphically to the Sinemurian (Obtusum Zone) (McGowan, 1993), and early Pliensbachian (McGowan and Milner, 1999), respectively. ...
... Unambiguous examples of pathological (non-congenital) ankylosis are relatively rare. In L. tenuirostris, co-ossification of the humerus, radius and ulna has been described in four specimens, with co-ossification limited to the radius and ulna in one individual (Delair, 1974;McGowan, 1989). Fr€ obisch, Sander & Rieppel (2006) reported zygopophyseal fusion, with accompanying bone rugosity and malformation, in cervical vertebrae 6-9 in the holotype of Cymbospondylus nichollsi from the Middle Triassic (Anisian) of Nevada. ...
Pathological studies in palaeontology represent a useful tool for understanding the behavior and interactions
between species or individuals as the possible causes of injuries. Such studies, however, are not
common in fossil vertebrates. We considered ichthyosaur fauna from the Posidonienschiefer Formation
(Early Jurassic: Toarcian) from Southwestern Germany to determine if taxonomy, adult body size, ontogeny
or stratigraphy influences the presence of osteopathologies in ichthyosaurs.
We surveyed 238 specimens of ichthyosaurs from the Posidonienschiefer Formation referable to five
genera: Temnodontosaurus, Eurhinosaurus, Suevoleviathan, Hauffiopteryx and Stenopterygius. We
classified the presence and absence of pathologies according to five variables (genus, anatomical region,
size, ontogeny, stratigraphy) and analyzed the data using logistic regression.
The model indicated that the incidence of pathologies was dependent on both taxon and anatomical
region, but the interaction term was not significant. Large genera do not show a significantly higher incidence
of pathology than small genera, suggesting that body size alone is not a factor directly related
to the frequency of pathologies in ichthyosaurs. For the ontogenetic and stratigraphic analyses, we
considered only Stenopterygius for reasons of sample size. There were significantly more pathologies
in the largest adults than in neonates, juveniles, and small adults, and significantly fewer pathologies in
mid-sized adults than in all other size classes. Stratigraphic horizon did not influence the frequency of
pathologies in Stenopterygius in the Posidonienschiefer Formation.
Our study represents the first comprehensive analysis of palaeopathologies in a palaeocological context
in marine reptiles and will serve as a model for future work on palaeopathologies.
Acknowledgments: we acknowledge the museum curators from the collections visited for permitting
access. This research was funded by DFG project MA 4693/4-1.
... McGowan's identification is almost certainly correct, given his extensive research on that genus (e.g., McGowan, 1989McGowan, , 1996 that specimen is presently missing and was never figured. Additionally, the specimen number provided by Storrs (1994) does not correspond with the BRSMG accession register and the specimen cannot presently be located (DRL, pers. ...
The holotype of Wahlisaurus massarae is known only from a partial skull and postcranial skeleton from the Lower Jurassic, collected near Normanton on Soar, Nottinghamshire, UK. It is diagnosed relative to other ichthyosaurs on the basis of autapomorphies of the coracoid and a unique combination of characters. Here, we report a second specimen of W. massarae. The new specimen comprises a practically complete right coracoid that clearly shows the unique morphology of W. massarae. This specimen was collected in situ from a quarry in Somerset, from the base of the Blue Lias Formation, which corresponds to the Triassic–Jurassic boundary (uppermost Rhaetian or lowermost Hettangian), extending the geographic and stratigraphic range of the species. Furthermore, the coracoid of the new specimen is 20% anteroposteriorly longer than in the holotype, representing a larger individual. In light of preparation and the identification of additional fragments of the holotype, a redescription of the skull morphology of the holotype, as well as comparison with the skull roof of Leptonectes tenuirostris, is included.
... Unambiguous examples of pathological (non-congenital) ankylosis are relatively rare. In L. tenuirostris, co-ossification of the humerus, radius and ulna has been described in four specimens, with co-ossification limited to the radius and ulna in one individual (Delair, 1974;McGowan, 1989). Fr€ obisch, Sander & Rieppel (2006) reported zygopophyseal fusion, with accompanying bone rugosity and malformation, in cervical vertebrae 6-9 in the holotype of Cymbospondylus nichollsi from the Middle Triassic (Anisian) of Nevada. ...
The documented record of ichthyosaurian paleopathologies reveals an array of injury-related bone modifications and instances of disease evidenced through multiple clades, skeletal regions and body-size classes from the Middle Triassic to middle Cretaceous. Examples include traumatic injuries, as well as a high incidence of articular diseases, including avascular necrosis. Forelimb pathologies are particularly abundant (65% of total reported), and the glenoid region seems to have been especially prone to articular disease. In contrast, pathologies affecting the vertebral column are comparatively underrepresented (6% of reported pathologies). Also notable is the disproportionate commonality of osteopathologies in ichthyosaurian taxa between 2 and 6 m in length (54%), as opposed to demonstrably larger (31%) or smaller bodied (15%) species. Furthermore, osteopathologies are almost exclusively described from skeletally mature individuals, and are best known from taxa of Jurassic age (78%), versus those from the Triassic (15%) or Cretaceous (7%); this likely reflects biases in the ichthyosaurian fossil record through time. Ichthyosaurs evince remarkable similarities in the types of observed skeletal damage relative to other ecologically similar marine amniotes – especially cetaceans and mosasaurid squamates, all of which potentially exhibited equivalent palaeoecological and/or behavioural adaptations for life in aqueous environments. Notably, however, the unusually low frequency of vertebral pathologies in ichthyosaurs is peculiar, and requires further investigation to establish significance.
... Yet, the small overbite in Pervushovisaurus campylodon raises questions regarding its function—if any. Moderate to large overbite evolved among leptonectid ichthyosaurs during the Early Jurassic (Huene, 1951; McGowan, 1986; McGowan, 1989; McGowan, 2003; Lomax, 2016). Overbite is not recorded in ichthyosaurs after the Toarcian; this feature thus re-evolved in Pervushovisaurus campylodon (or its ancestor if this feature is also present in Pervushovisaurus bannovkensis) after a 73 million years hiatus. ...
Fischer 2016. Taxonomy of Platypterygius campylodon and the diversity of the last ichthyosaurs. PeerJ 4:e2604; DOI 10.7717/peerj.2604. Freely available here: peerj.com/articles/2604/?td=bl
A complex and confusing taxonomy has concealed the diversity dynamics of Cretaceous ichthyosaurs (Reptilia) for decades. The near totality of Albian-Cenomanian remains from Eurasia has been assigned, by default, to the loosely defined entity Platypterygius campylodon, whose holotype was supposed to be lost. By thoroughly examining the Cenomanian ichthyosaur collections from the UK, I redescribe the syntypic series of Platypterygius campylodon. This material, along with a handful of other coeval remains, is diagnostic and seemingly differs from the vast majority of Cretaceous remains previously assigned to this taxon. A lectotype for Platypterygius campylodon is designated and I reassign this species to Pervushovisaurus campylodon nov. comb. The feeding ecology of this species is assessed and conforms to the scenario of an early Cenomanian diversity drop prior to the latest Cenomanian final extinction.
... The Early Jurassic fauna of Lyme Regis, England, has yielded about a half-dozen ichthyosaur species, ranging in size from the 1.5-m-long Ichthyosaurus breviceps to the 9-m-long Temnodontosaurus platyodon (McGowan, 1974a(McGowan, , b, 1989a(McGowan, , 1994a. Two other species, Excalibosaurus costini and Leptopterygius solei are also known from the lower Liassic of the region (McGowan, 1986(McGowan, , 1989b(McGowan, , 1993. The ichthyosaurs occupied four of the six feeding guilds (Massare, 1987). ...
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http://www.sciencedirect.com/science/article/pii/B9780121552107500211
... It was collected from the Lower Jurassic Preplanorbis beds (lowermost Hettangian) of Barnstone and was tentatively identified as ?Leptopterygius tenuirostris (now Leptonectes tenuirostris; McGowan, 1996). Upon examination of the illustration figured by Delair (1974), the specimen resembles many forefins that are currently regarded as Leptonectes and specifically L. tenuirostris (McGowan, 1989(McGowan, , 1990Vincent et al., 2014), but without firsthand examination we refer the specimen to Leptonectes sp. As the specimen cannot currently be traced it is not discussed further. ...
The occurrence of ichthyosaurs from Nottinghamshire is poorly documented. Here, we report on at least 67 specimens from museum and university collections. The specimens range from isolated elements to nearly complete skeletons. Preservation varies, but some are three-dimensional. The identification of both Ichthyosaurus and Temnodontosaurus in the county adds additional localities for the occurrence of those genera. Nottinghamshire is one of only a few counties to have yielded a fairly substantial number of ichthyosaur specimens. They are from localities in the Upper Triassic (Penarth Group) and Lower Jurassic (Lower Lias Group) that can no longer be accessed.
... I therefore refrain from erecting a new genus, but I remove the species Ichthyosaurus acutirostris from Temnodontosaurus, to which I had previously referred it in 1997. MCGOWAN (1974aMCGOWAN ( , 1989bMCGOWAN ( , 19931996b); GODEFROIT (1992) MCGOWAN (2003) has since then described new and more complete material (a complete skeleton) of the taxon which was only known from a skull and some postcrania before. This new fi nd provides evidence, that a generic separation of the species from both Leptonectes and Eurhinosaurus can be justifi ed. ...
A historical overview and a synopsis of the current knowledge on the phylogeny, systematics, and phylogenetic position of the Ichthyosauria are presented. All known ichthyosaur taxa are listed, new taxa are discussed and diagnosed. The following new taxa are erected: Thaisauridae n. fam., Wimaniidae n. fam., Barracudasauroides n. gen. with Mixosaurus panxianensis JIANG et al., 2006 as type species, as well as the species Omphalosaurus merriami n. sp. Merriamosaurus MAISCH & MATZKE, 2003 is a junior synonym of Pessopteryx WIMAN, 1910. “Ichthyosaurus” acutirostris OWEN, 1840 probably represents a genus of its own. Based on this summary of our current understanding of the group as a whole, ichthyosaurs are included in two of the largest and more widely used phylogenetic analyses of the Amniota. Character codings and their justifi cations are discussed. No clear signal on the phylogenetic position of the Ichthyosauria results from these analyses. Instead, they are in one case nested within the Diapsida, but with the anapsid Mesosauria as their sister group. In the other case they are nested within Parareptilia, with Procolophonia (Testudines, Pareiasauria) as sister group. In contrast to previous assumptions, the inclusion of ichthyosaurs in these large-scale analyses always changes the original topology of the resulting cladograms so that turtles and pareiasaurs become sister groups. This underlines the importance
of the taxon Ichthyosauria for any future large-scale phylogenetic analyses of amniotes. At the present state of knowledege, a defi nite decision on the origin and phylogenetic position of ichthyosaurs is still impossible, but descent from primarily anapsid ancestors and an origin from among the Parareptilia can not be excluded as an alternative to a diapsid origin of the group.
... The taxonomic diversity of Cretaceous ichthyosaurs is now equivalent to or greater than that of their Jurassic ancestors, both at the generic and specific levels, contrary to previous assumptions [4,129,130]. Indeed, the diversity frequently reaches four to five genera and seven to eight species whenever fossil-rich sediments occurring in distinct basins are found, such as the Hettangian-Sinemurian [69,[131][132][133][134][135] of western Europe, the Tithonian of England (top of the Kimmeridge Clay Formation; [136,137], Germany [72,100,138,139] and South America [107,108,140], and several periods during the Albian [22]. The extremely abundant material from the Toarcian (possibly several thousands of specimens [141]) certainly biases the record. ...
Background:
Ichthyosaurs are reptiles that inhabited the marine realm during most of the Mesozoic. Their Cretaceous representatives have traditionally been considered as the last survivors of a group declining since the Jurassic. Recently, however, an unexpected diversity has been described in Upper Jurassic-Lower Cretaceous deposits, but is widely spread across time and space, giving small clues on the adaptive potential and ecosystem control of the last ichthyosaurs. The famous but little studied English Gault Formation and 'greensands' deposits (the Upper Greensand Formation and the Cambridge Greensand Member of the Lower Chalk Formation) offer an unprecedented opportunity to investigate this topic, containing thousands of ichthyosaur remains spanning the Early-Late Cretaceous boundary.
Methodology/principal findings:
To assess the diversity of the ichthyosaur assemblage from these sedimentary bodies, we recognized morphotypes within each type of bones. We grouped these morphotypes together, when possible, by using articulated specimens from the same formations and from new localities in the Vocontian Basin (France); a revised taxonomic scheme is proposed. We recognize the following taxa in the 'greensands': the platypterygiines 'Platypterygius' sp. and Sisteronia seeleyi gen. et sp. nov., indeterminate ophthalmosaurines and the rare incertae sedis Cetarthrosaurus walkeri. The taxonomic diversity of late Albian ichthyosaurs now matches that of older, well-known intervals such as the Toarcian or the Tithonian. Contrasting tooth shapes and wear patterns suggest that these ichthyosaurs colonized three distinct feeding guilds, despite the presence of numerous plesiosaur taxa.
Conclusion/significance:
Western Europe was a diversity hot-spot for ichthyosaurs a few million years prior to their final extinction. By contrast, the low diversity in Australia and U.S.A. suggests strong geographical disparities in the diversity pattern of Albian-early Cenomanian ichthyosaurs. This provides a whole new context to investigate the extinction of these successful marine reptiles, at the end of the Cenomanian.
CORRECTION TO TABLE 1: NHMUK R 11801 is now NHMUK R 38005 _________________________________________________________________________________.
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.
Ilminster-born Charles Moore (1815-1881) was an indefatigable West Country geologist
who made significant and wide-ranging contributions to the science, both in terms of the material he collected and his publications. Following his permanent move to Bath in 1853, Moore collected extensively in Late Triassic rocks, amassing a rich haul of fossil vertebrate specimens. A pioneer of bulk sampling, his fossil vertebrate collection from the Rhaetian fissure infills at Holwell, Somerset has provided much research material for subsequent study; Holwell is now the type locality for several Late Triassic mammaliaforms, reptiles (lepidosaurs) and chondrichthyans. His collection of vertebrate remains from the Arden Sandstone Formation (Carnian Age) at Ruishton has never been fully described, but contains some significant material including isolated xenacanth and hybodont shark's teeth, dorsal fin spines and cephalic spines. The objective of this present paper is to raise the profile of Moore's work on late Triassic vertebrate fossils, to highlight his innovative approach to bulk collecting, and to assess the scientific importance of his collections in both historical and modern contexts.
An almost complete ichthyosaur from the historically significant collection of fossils amassed by Somerset geologist, Charles Moore, is described. Available information suggests that it was collected from the Lower Lias of Somerset, UK. However, inspection of the surrounding matrix, which seems to be a nodule, indicates that the specimen may instead hail from the Upper Lias (Toarcian) Strawberry Bank Lagerstätte of Ilminster, Somerset. The specimen had previously been identified as Leptonectes tenuirostris. Herein, further analysis of the skull and forefin, reveals closer affinities to Stenopterygius triscissus, to which the specimen is tentatively assigned. Therefore, the specimen represents one of the most complete ichthyosaurs collected from the Strawberry Bank Lagerstätte.
For the first time, a three-dimensionally preserved skull of the Lower Jurassic leptonectid ichthyosaur Leptonectes cf. tenuirostris is described. The specimen reveals a wealth of new data on the cranial anatomy of basal leptonectid neoichthyosaurs. The osteology of the skull roof differs fundamentally from other well-known post-Triassic ichthyosaurs and is highly autapomorphic. The structure of the sclerotic ring, which is well preserved in situ, is described and it appears plausible that L. cf. tenuirostris was capable of stereoscopic vision. Inadequate description makes comparison to other leptonectids difficult. It can be demonstrated, however, that L. cf. tenuirostris is most similar to L. tenuirostris among known leptonectids. It is fundamentally different from the Upper Liassic Eurhinosaurus longirostris in the osteology of the skull roof and the size and orientation of the major skull openings, making generic distinction of these two species a necessity. At the moment, no autapomorphies are known of the genus Leptonectes, which therefore must be considered as a metataxon that comprises basal leptonectids from the Lower to Middle Liassic.
Cretaceous ichthyosaurs have typically been considered a small, homo- geneous assemblage sharing a common Late Jurassic ancestor. Their low diversity and disparity have been interpreted as indicative of a decline lead- ing 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 ana- lyses. 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 mor- phology 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 pro- duced lineages with Cretaceous representatives, but the radiation events themselves are pre-Cretaceous. Cretaceous ichthyosaurs therefore include distantly related lineages, with contrasting evolutionary histories, and appear more diverse and disparate than previously supposed.
All specimens of Ichthyosaurus from the Lower Jurassic of Somerset were previously identified as I. communis, an abundant and extremely variable species. Here, two new species of Ichthyosaurus are recognized from multiple specimens. The species are assigned to Ichthyosaurus on the basis of the humerus, pectoral girdle and forefin morphologies. I. larkini sp. nov. is distinguished by a broad jugal with a blunt anterior end that extends as far forward as the middle of the external naris, separating the maxilla and lacrimal; and a unique combination of other features. I. somersetensis sp. nov. is distinguished by a jugal with a nearly straight dorsal ramus that lacks a right-angle dorsal bend; a high, narrow, crescentic postorbital that forms almost all of the posterior margin of the orbit and separates the jugal dorsal ramus from the orbit; and an ilium that is wide relative to its length, more oblong than rib-like. The identifications are supported by a phylogenetic analysis which finds the new species more closely related to each other than to other species of the genus. We also identify a squamosal in both species, which confirms that it is present in the genus. This study suggests that hindfin morphology has some taxonomic utility, at least within the genus. The new species increases the diversity of Ichthyosaurus to six species, three of which are found in the Hettangian of Somerset.
A partial skeleton, including a skull with part of the axial skeleton, part of a second skull, and fragments of ribs have been recovered from the Sinemurian of the Sandilands Formation exposed at Kennecott Point in the northwestern Queen Charlotte Islands. This material is the most complete Early Jurassic collection from North America reported to date; other occurrences include a forefin from the Nordegg Formation (Sinemurian) of Alberta positively identified as Ichthyosaurus (McGowan, 1978) and vertebral centra from the Nicely Formation (Pliensbachian), Oregon, not assigned conclusively to a genus (McGowan, 1978). The discovery of ichthyosaurs in the allochthonous insular belt of British Columbia adds weight to the contention that ichthyosaurs were cosmopolitan in their distribution (McGowan, 1978; Orr, 1986).
The tailbend, a downward flexure of the vertebral column, is a prominent feature of post-Triassic ichthyosaurs. However, due to the vagaries of preservation and of preparation, its presence cannot be verified in all skeletons. Computed tomography offers a solution to the problem by identifying the wedge-shaped centra that contribute to the tailbend. Leptopterygius tenuirostris appears to have a tailbend, albeit slightly downturned. There is also evidence that its close relative Eurhinosaurus longirostris had a tailbend, too.
The ichthyosaur specimens from the so-called Alpha-Ölschiefer (Uppermost Lower Sinemurian) of Baden-Württemberg belong to the families Leptonectidae, represented by Leptonectes tenuirostris (CONYBEARE 1822) and generic and to specific indeterminate material, and Temnodontosauridae, represented by Temnodontosaurus cf. platyodon (CONYBEARE 1822), taxa that are well known from coeval strata in Southern England. The most common family of English lower Liassic ichthyosaurs, Ichthyosauridae, is not unequivocally recorded from the Alpha-Ölschiefer and, in fact, only known from a single, incomplete specimen in the entire Lias of Southern Germany. What is known of the lower Liassic ichthyosaur fauna of Southern Germany corresponds completely to the English occurrences, no regional differences as in the Upper Lias seem to exist.
The ichthyosaur fauna of the Lower Toarcian Posidonienschiefer (Lias epsilon) of South Western Germany is clearly less diverse than usually supposed. Only four genera with at maximum eight species can be recognised. Apart of the common taxa a rare, morphologically distinctive form, the genus Suevoleviathan, probably an inhabitant of the open sea, occurs. A new alphataxonomic subdivision of the problematic genus Stenopterygius is proposed. Only four species are accepted, S. quadriscissus, S. hauffianus, S. megalorhinus and S. longifrons for which new diagnoses are presented. The high diversity of that genus postulated by earlier authors is in part an artifact based on misinterpretation of incorrectly restored skeletons. All Toarcian temnodontosaurids from South Western Germany belong to the species Temnodontosaurus trigonodon, for which a new diagnosis is formulated. T. burgundiae (GAUDRY, 1892) is very probably a junior subjective synonym of T. trigonodon.
The Early Jurassic Toarcian Oceanic Anoxic Event is considered one of the most dramatic environmental perturbations of the Mesozoic. An elevated extinction rate among marine invertebrates accompanied rapid environmental changes, but effects on large vertebrates are less understood. We examined changes in ichthyosaur body size in the Posidonia Shale of the Southwest German Basin spanning the extinction interval to assess how environmental changes and biotic crisis among prey species affected large reptiles. We report no species-level extinction among the ichthyosaurs coinciding with peak invertebrate extinction. Large ichthyosaurs were absent from the fauna during the extinction interval, but became more abundant in the immediate aftermath.
Stenopterygius quadriscissus
, the most abundant species during the extinction interval, increased in body size after the biotic event. Rapid invasion by large taxa occurred immediately following the extinction event at the end of the first ammonite zone of the early Toarcian. Greater mobility permitting exploitation of ephemeral resources and opportunistic feeding behavior may minimize the impacts of environmental change on large vertebrates.
The ichthyosaur Shonisaurus sikanniensis sp. nov. is described from the Pardonet Formation (Norian, Late Triassic) of northeastern British Columbia. The type specimen is considerably larger than Shonisaurus popularis, with an estimated length of 21 m. It also differs from S. popularis in having a fan-shaped scapula, and relatively longer vertebral centra. Studies of this new species, along with re-examination of S. popularis, suggests that Shonisaurus was not as deep-bodied as previously reconstructed. Teeth are set in sockets, but are known only in a few, small individuals. This implies that teeth were present only in juveniles, and that adults were edentulous. The new species extends the geographical and stratigraphical range of Shonisaurus to the middle Norian of British Columbia.
The Neogene species Petaloconchus sculpturatus presents a contradiction in terms, for it grows whorl "packages;' of nearly perfect regularity, but ranks within the most geometrically irregular family of uncoiled gastropods, the Vermetidae. A first biometric study of vermetids is performed to specify and characterise the factors on both sides of this "exquisite tension' between promotion and prevention of recoiling. The complex combination of promoting and preventing factors produces a shell that is tantalizingly close to fully regular, but cannot truly reattain this previous phyletic state - thus providing a fine example of Dollo's Law at the centenary of his formation of irreversibility. -from Authors
Mesozoic marine reptiles went through a severe turnover near the end of the Triassic. Notably, an important extinction event affected ichthyosaurs, sweeping a large part of the group. This crisis is, however, obscured by an extremely poor fossil record and is regarded as protracted over the entire Norian-earliest Jurassic interval, for the lack of a more precise scenario. The iconic whale-sized shastasaurid ichthyosaurs are regarded as early victims of this turnover, disappearing by the middle Norian. Here we evaluate the pattern of this turnover among ichthyosaurs by analysing the faunal record of two Rhaetian localities. One locality is Autun, eastern France; we rediscovered in this material the holotypes or partial 'type' series of Rachitrema pellati, Actiosaurus gaudryi, Ichthyosaurus rheticus, Ichthyosaurus carinatus and Plesiosaurus bibractensis; a revised taxonomic scheme is proposed. The second assemblage comes from a new locality: Cuers, southeastern France. Both these assemblages provide several lines of evidence for the presence of shastasaurid-like ichthyosaurs in the Rhaetian of Europe. These occurrences suggest that both the demise of shastasaurids and the sudden radiation of neoichthyosaurians occurred within a short time window; this turnover appears not only more abrupt but also more complex than previously postulated and adds a new facet of the end-Triassic mass extinction.
Eight remarkably preserved specimens of ichthyosaurs from the lower Toarcian (Lower Jurassic) of Strawberry Bank (Ilminster, Somerset, England) are described fully for the first time. Whereas previously these ichthyosaurs were assigned to one species, Stenopterygius hauffianus, our study shows there are two, Stenopterygius triscissus and Hauffiopteryx typicus. S. triscissus is a small‐ to medium‐sized ichthyosaur up to 3.5 m long, characterised by three apomorphies: long and slender rostrum, large elliptical supratemporal fenestra and bipartite pelvis. H. typicus is a small ichthyosaur up to 2.95 m long, with five apomorphies: short and extremely slender rostrum, very large orbit, small rounded supratemporal fenestra and tripartite pelvis, which is fused distally. Cladistic analysis is equivocal about their relationships, suggesting either that Hauffiopteryx and perhaps also Stenopterygius are members of a clade Eurhinosauria or that this clade does not exist, and both genera are members of a wider clade Thunnosauria. Further, the clade Stenopterygiidae, in which Hauffiopteryx had been located, is not identified. Most striking is that the specimens are all juveniles (five specimens) or infants (three specimens), ranging from one‐tenth to one‐half the normal adult length of the species.
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.
The early history of reptile palaeontology is reviewed in order to assess the different roles played by museums, collections and collectors. The formal characterization and description of several fossil reptile groups (mosasaurs, pterosaurs, ichthyosaurs, plesiosaurs and dinosaurs) is then examined in a series of case histories. Fossil reptile bones were collected from the end of the sixteenth century, originally as objects of curiosity. The comprehensive collection of John Woodward (1665-1728) was an exception to this, and fossil reptiles only comprise a small fraction of the total number of specimens. Early discoveries of reptile fossils were interpreted within an anthropocentric context, with later interpretations being based on contemporary exotic faunas. The emergence of the systematic study of comparative anatomy at the end of the eighteenth century allowed more precise identifications of specimen's affinities, and demonstrated that extinction was a reality. Interpretations were no longer constrained by the contemporary biota. Georges Cuvier was instrumental in both of these advances. Collections and museums of comparative biological material were vital to his methods, and to the whole field of comparative anatomy. By the 1840s, fossil reptiles had been classified into separate and distinguishable groups. Private collectors were important for securing new discoveries, but specimens have only survived when they were acquired by institutional museums. Museums and their collections influenced the careers of such early pioneers as Richard Owen, who later became one of the most politically powerful scientists of the nineteenth century. It is hard to conceive how a field such as palaeontology could survive without collections, as fossil reptiles ably demonstrate.
A previously undocumented marine reptile fauna comprising well-preserved ichthyosaur and plesiosaur remains is described from the Early Jurassic Saltford Shale Member within the Blue Lias Formation of central England. Two ichthyosaur genera are recognized, namely Leptonectes and Ichthyosaurus, as well as generically indeterminate remains of plesiosaurs. The specimens include partly-articulated skeletons, reflecting preservation in dysaerobic argillaceous sediment in a dominantly low-energy setting on the English East Midlands Shelf.
Temnodontosaurus platyodon, from the English lower Liassic (Hettangian and Sinemurian), is a large ichthyosaur that reached an estimated length of almost 9 m (29 ft). Although represented by at least 13 specimens, few are complete, and the species cannot be described as well known. A similarly sized species from the upper Liassic (Toarcian) of Germany has hitherto been referred to a separate genus, but is shown here to be referable to Temnodontosaurus. This species, T. burgundiae, shares several features in common with T. platyodon, including a small orbit, modestly sized teeth, a relatively long maxilla, forefins probably with four or less digits, notching in at least some of the elements of the first digit, a distally expanded humerus, and a discrete pubis and ischium. An emended diagnosis is given for Temnodontosaurus. Poorly known giants from the English lower Liassic, represented only by isolated teeth and girdle elements, may have reached lengths of 15 m (49 ft). This at least equals the size of the largest known ichthyosaur, Shonisaurus. These mysticete-sized reptiles may have fed upon other ichthyosaurs.
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 new ichthyosaur species is described from the Upper Triassic (middle Norian) of Williston Lake, northeastern British Columbia. Aside from the foramen enclosed between the radius and ulna–a characteristic of Triassic ichthyosaurs–the new specimen is typical of Lower Jurassic forms. Indeed, if the specimen had been collected from the English lower Liassic, there would have been no hesitation in referring it to the common English genus Ichthyosaurus, a taxonomic course I follow here. Referring the new species to Ichthyosaurus extends the geological range of the genus by approximately 9 Ma, to the middle Norian. Ichthyosaurus janiceps sp. nov. has an abbreviated snout, like that of Ichthyosaurus breviceps, but it is a much larger species, and has a distinctly different forefin.
A small, nearly complete ichthyosaur skeleton is described from the Upper Triassic of Williston Lake, in northeastern British Columbia. The age of the material, based on conodonts, is early Norian. Although the length of the entire skeleton would probably not have exceeded 1 m, there is no evidence of immaturity–quite the contrary. Named Hudsonelpidia brevirostris, the new taxon shares some features with Triassic taxa, as exemplified by Mixosaurus from the European Middle Triassic, and with post-Triassic ichthyosaurs like Ichthyosaurus, from the English Lower Jurassic. Mixosaurian characters include an elongate tibia with emarginated pre- and postaxial margins, and phalanges in the hindfin with pre- and postaxial notches. Like Ichthyosaurus, the humérus is elongate rather than broad, so too is the pubis and ischium. Mixosaurus is unusual among Triassic ichthyosaurs for having a relatively large orbit, but the orbit is even more prominent in Hudsonelpidia, probably because of the shortness of the snout. Hudsonelpidia has an unusually large femur that approaches the length of the humérus, dwarfing the rest of the hindfin. The rostrum is unique in being perforated by foramina, but this could possibly be an abnormality.
Some unusual extensions of the neural spines are reported for two ichthyosaurs from the Lower Jurassic of Germany. These processes are similar to those recently reported for the enigmatic marine reptile Hupehsuchus, from the Middle Triassic of China. There are insufficient data to determine whether the ichthyosaurian processes are homologous with those of Hupehsuchus, nor whether they represent ancestral features that were normally suppressed during ontogeny. The possibility that the processes are artificial rather than natural cannot be discounted.
A large ichthyosaur, with a total length in excess of 7 m, is described from the Lower Jurassic (Sinemurian) of Dorset, England. Like Leptopterygius tenuirostris the new species, named Leptopterygius solei, has a long slender snout armed with slender teeth that are remarkably small for the large size of the skull. There are also similarities in the forefin: the humerus is widely expanded distally, and the phalanges are rounded rather than polygonal and are probably well spaced distally. However, in contrast to L. tenuirostris, there is no notch on the leading edge of the radius. The snout is also relatively shorter and the orbit smaller. Thus in the holotype the estimated values for the snout and orbital ratios are 0.68 and 0.15 respectively, compared with observed ranges for L. tenuirostris of 0.71–0.76 (n = 7) and 0.18–0.24 (n = 7). Leptopterygius solei also has a somewhat higher prepelvic vertebral count, being at least 50 in the holotype compared with an observed range of 44–48 (n = 9) for L. tenuirostris. Furthermore, the ischium is considerably wider than the pubis, whereas these elements have approximately similar widths in L. tenuirostris. The possibility that the new material might merely represent the upper end of a growth series of L. tenuirostris is dismissed. Based on skull length, the holotype of L. solei is 66% larger than the largest specimen of L. tenuirostris.
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 the radiation events themselves are pre-Cretaceous. Cretaceous ichthyosaurs therefore include distantly related lineages, with contrasting evolutionary histories, and appear more diverse and disparate than previously supposed.
The Vocontian Basin (SE France) was formed along the northwestern border of Tethys during Mesozoic times. Mainly known for its rich ammonite fauna, this basin has also yielded several Lower Jurassic ichthyosaurs. The specimens discussed here were discovered in lower Toarcian limestone and marl successions in the vicinity of Digne-les-Bains, High-Provence Alps. The best-preserved specimen is identified as Suevoleviathan sp., a rare taxon previously reported only in southern Germany. Along with this specimen, premaxillae and paddle elements of Eurhinosaurus sp. and probable Stenopterygiidae centra were found in neighbouring localities. These specimens were preserved thanks to the deposition of soft anoxic marls or calcarodetritic sediments, coeval with other anoxic shales in Europe (the Toarcian Oceanic Anoxic Event or T-OAE), which allows faunal comparisons between these basins. The localities from the Vocontian Basin are closer to the Tethys than any other sites where identifiable Toarcian ichthyosaurs have been found in Europe. Nevertheless, the Vocontian ichthyosaur assemblage is strikingly similar to those of other basins across Europe. This suggests a wide palaeobiogeographical distribution for Toarcian ichthyosaurs, reflecting their anatomical adaptations as highly mobile swimmers.
A newly prepared plesiosaur skull collected by Thomas Hawkins (1810–1889) from the Lias quarries of Street, Somerset, England, provides important indications of character polarity within the Plesiosauria. Many features of the 3-dimensional, matrix-free skull are seemingly plesiomorphic in accord with the early, probably latest Rhaetian, stratigraphic position of the specimen. The small supratemporal fenestrae, elongate jugals, deeply excavated cheek, spatulate mandibular symphysis, and other characters thus have important implications for phylogenetic studies of the Plesiosauria. A new genus is erected to include the skull and several other specimens of historical importance that comprise part of the oldest known fauna of fully articulated plesiosaurs.
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.
Shonisaurus, from the Upper Triassic (Carnian) of Nevada, is represented by some 40 individuals. However, many comprise only a few elements, and not one of the skeletons is complete. Furthermore, preservation is often poor, so information is limited. Reaching lengths of up to 15 m, possibly slightly more, Shonisaurus was about the size of a Gray Whale. The only other ichthyosaur of comparable size was a little known and unnamed ichthyosaur from the English Lower Jurassic, which may have reached 15 m (McGowan, 1996). Shonisaurus was long-bodied, with about 60 presacral vertebrae. Some of the centra, at about the level of the 97th vertebra, are wedge-shaped, indicating a tailbend. However, their cambers are small, and their combined angle of deflection is only about 5°, which hardly constitutes a tailbend. The paired fins were long and slender, with no more than three major digits in each, possibly only two.Contrary to previous descriptions, the emarginations on the free margins of many of the fin elements were probably preaxial rather than postaxial, as in all other ichthyosaurs. The coracoid does not have a hooked process distally, and is therefore much like that of Shastasaurus. The teeth are set in individual sockets, as previously described. Three species have been described, but S. popularis is here considered the only valid species.
For the first time, a three-dimensionally preserved skull of the Lower Jurassic leptonectid ichthyosaur Leptonectes cf. tenuirostris is described. The specimen reveals a wealth of new data on the cranial anatomy of basal leptonectid neoichthyosaurs. The osteology of the skull roof differs fundamentally from other well-known post-Triassic ichthyosaurs and is highly autapomorphic. The structure of the sclerotic ring, which is well preserved in situ, is described and it appears plausible that L. cf. tenuirostris was capable of stereoscopic vision. Inadequate description makes comparison to other leptonectids difficult. It can be demonstrated, however, that L. cf. tenuirostris is most similar to L. tenuirostris among known leptonectids. It is fundamentally different from the Upper Liassic Eurhinosaurus longirostris in the osteology of the skull roof and the size and orientation of the major skull openings, making generic distinction of these two species a necessity. At the moment, no autapomorphies are known of the genus Leptonectes, which therefore must be considered as a metataxon that comprises basal leptonectids from the Lower to Middle Liassic.
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