Kawanectes lafquenianum: a new Elasmosaurid Plesiosaur From Campanian/Maastrichtian Cretaceous Patagonia

A SMALL BODY SIZED NON-ARISTONECTINE ELASMOSAURID (SAUROPTERYGIA, PLESIOSAURIA) FROM THE LATE CRETACEOUS OF PATAGONIA WITH COMMENTS ON THE RELATIONSHIPS OF THE PATAGONIAN AND ANTARCTIC ELASMOSAURIDS

Author:

O'Gorman

Abstract:

The systematics of the Late Cretaceous non-aristonectine elasmosaurids from Argentinean Patagonia are poorly known as there is no valid species currently recognized. Here a new non-aristonectine elasmosaurid: Kawanectes lafquenianum nov. comb. from the late Campanian–early Maastrichtian Allen Formation is diagnosed. Kawanectes lafquenianum is a distinctively small-bodied sized non-aristonectine elasmosaurid characterized by caudal vertebrae with marked laterally projected parapophyses, presence of pelvic bar, high ratio (~1.2) between humerus/femur length and a large posterodistal projection of the humerus which bears a posterior accessory articular facet. A phylogenetic analysis recovered K. lafquenianum closely related with Morenosaurus stocki, Vegasaurus molyi and Aristonectinae, showing the relationships between the elasmosaurids from Patagonia, Western Antarctic, and the Pacific coast of the USA. Kawanectes lafquenianum is part of the fauna of the coeval Allen and La Colonia formations that also comprises indeterminate aristonectines and polycotylids . This relatively high diversity plesiosaur fauna includes the three main morphotypes (aristonectines, non-aristonectines elasmosaurids and polycotylids), which is remarkable since the depositational environments of the Allen have been inferred as marginal marine to non-marine environments.

Cardiocorax mukulu: a new Elasmosaurid Pleisosaur From Maastrichtian Cretaceous Angola

A new elasmosaurid from the early Maastrichtian of Angola and the implications of girdle morphology on swimming style in plesiosaurs

Authors:

Araújo et al

Abstract:

We report here a new elasmosaurid from the early Maastrichtian at Bentiaba, southern Angola. Phylogenetic analysis places the new taxon as the sister taxon to Styxosaurus snowii, and that clade as the sister of a clade composed of (Hydrotherosaurus alexandrae (Libonectes morgani + Elasmosaurus platyurus)). The new taxon has a reduced dorsal blade of the scapula, a feature unique amongst elasmosaurids, but convergent with cryptoclidid plesiosaurs, and indicates a longitudinal protraction-retraction limb cycle rowing style with simple pitch rotation at the glenohumeral articulation. Morphometric phylogenetic analysis of the coracoids of 40 eosauropterygian taxa suggests that there was a broad range of swimming styles within the clade.

Dwarf, Freshwater Elasmosaurs Found From Campanian/Maastrichtian Patagonia?

Late Cretaceous reptilian biota of the La Colonia Formation, central Patagonia, Argentina: Occurrences, preservation and paleoenvironments

Authors:

Gasparini et al

Abstract:

Cropping out on the southeastern margin of the Somún Curá Plateau, the La Colonia Formation (Campanian–Maastrichtian) has yielded, over the last several decades, a varied fossil tetrapod fauna (mammals, ophidians, turtles, dinosaurs, plesiosaurs, anurans). For this study several field trips were carried out specifically to recover reptile remains. Three sections, located on the southeastern slope of the Sierra de La Colonia and in the vicinity of Cerro Bayo, Chubut Province (Argentina), were selected for particular attention. The prospected sections are composed of massive, laminated or heterolithic siltstones and claystones, with scarce and thin intercalations of massive, heterolithic o cross-bedded fine sandstones and of fossiliferous conglomerates. The most abundantly recovered reptiles are terrestrial and freshwater turtles, followed by plesiosaurs and dinosaurs. Among the chelonians, more than 16 specimens of Patagoniaemys gasparinae (Meiolaniformes), three specimens of Yaminuechelys aff. Y. gasparinii (Chelidae), and the remains of a new genus of Chelidae were identified. Among the dinosaurs, theropod metatarsal fragments, an incomplete abelisaurid theropod skeleton, sauropod vertebrae, ankylosaur osteoderms and appendicular fragments of hadrosaurs were found. Among the plesiosaurs there are several well preserved elasmosaurids (including two with associated gastroliths) and a polycotylid (Sulcusuchus erraini). Except for the plesiosaurs, all the reptiles are terrestrial or freshwater taxa. However, analysis of the elasmosaurids indicates they are adult specimens of small body size, which could be related to forms that lived in restricted aquatic environments. Likewise, the polycotylid possesses deep rostral and mandibular grooves, and a conspicuous vascularization and/or innervation, that is consistent with the presence of some associated special sensory structures similar to those known in some cetaceans that inhabit modern rivers and estuaries. Sedimentological analysis suggests that deposition would have been mostly in low-energy restricted environments, like muddy plains, marshes and ponds cut by meandering channels, probably in the central mixed-energy zone within an estuary. This interpretation is consistent with the habitat inferred for the recovered reptiles, as well as with associated foraminifers and with the probable origin of gastroliths found associate with the plesiosaurs.

The Postcranial Skeleton of Elamosaurid Libonectes morgani From Turonian Cretaceous Texas

Postcranium of the paradigm elasmosaurid plesiosaurian Libonectes morgani (Welles, 1949)

Authors:

Sachs et al

Abstract:

Elasmosauridae constitutes one of the most immediately recognizable plesiosaurian radiations. Their distinctive body plan represents the popular model for Plesiosauria, and is typified by an osteological morphology especially adapted for hyper-elongation of the neck. Nevertheless, many archetypal elasmosaurids are known only from incomplete and/or inadequately documented material, a problem that has contributed to their uncertain intra-clade relationships. A prime example of this is Libonectes morgani from the Upper Cretaceous of Texas, USA, which is frequently presented as an elasmosaurid structural proxy because of its three-dimensionally preserved holotype skull. Perplexingly though, both the taxonomic diagnosis and phylogenetic placement of L. morgani rely primarily upon the cervical vertebrae, together with the pectoral girdle and forelimb, yet most of these elements are now lost and figured only as line drawings. We therefore reviewed the remnant postcranial skeleton of L. morgani first-hand with the objective of clarifying its defining character states. Our observations showed that the existing diagnosis of L. morgani is indeed inadequate. Moreover, the only identifiable autapomorphies occurred within the axial skeleton. This concurred with an examination of character scores used in published plesiosaurian phylogenies, and highlights the persistent significance of postcranial elements for discriminating elasmosaurid taxa.

A new Elasmosaurid Pleisosaur Found in Santonian Cretaceous Israel

A late Cretaceous elasmosaurid of the Tethys Sea margins (southern Negev, Israel), and its palaeogeographic reconstruction

Authors:

Rabinovich et al

Abstract:

Recent research on the late Cretaceous (Santonian), Menuha Formation of the southern Negev, Israel, has revealed several unconformities in its exposures, spatial changes in its lithofacies, agglomerations of its carbonate concretions and nodules at a variety of localities. At Menuha Ridge Site 20, portions of a new elasmosaurid skeleton were found within deposits of laminated bio-micritic muddy limestone with thin phosphatic layers. The sediments are rich in microfossils – foraminifera and ostracods preserved in the carbonate mud. Planktic foraminifera species (e.g. Dicarinella asymetrica, D. concavata, Sigalia decoratissima carpatica) appear as well as species indicative of opportunistic life strategies typical of a forming upwelling system in the region. Marine ostracods (e.g. Brachycythere angulata, Cythereis rosenfeldi evoluta) and many echinoid spines suggest an open marine environment. Using a multidisciplinary approach, we offer here a reconstruction of the micro-regional palaeogeography along a segment of the ancient shoreline of the Tethys Sea during the Santonian, and explain the environmental conditions under which the various fauna lived. This new elasmosaurid is examined in light of the above and compared with evidence from the adjacent areas along the margins of the southern Tethys Sea.

Was There Only One Elasmosaur Species in Maastrichtian Cretaceous Chile?

A new postcranial skeleton of an elasmosaurid plesiosaur from the Upper Cretaceous of central Chile and reassessment of Cimoliasaurus andium Deecke

Authors:

Otero et al

Abstract:

We describe a new specimen of an elasmosaurid plesiosaur from the upper Maastrichtian of central Chile. The specimen includes a relatively complete dorso-caudal series, a few cervical vertebrae, and a fragmentary pelvic girdle. The specimen is identified as a sub-adult non-artistonectine elasmosaurid (Sauropterygia, Plesiosauria) based on graphic bivariate analysis of the cervical vertebral proportions. The caudal vertebrae have distinctive features such as neural arches that are recurved cranially, with pedicels overlapping the dorso-posterior surface of the immediately anterior centrum, and terminal centra with two pairs of deep dorsal articulations for the neural arches. These unusual features are present in several late Maastrichtian adult specimens from the Quiriquina Formation of central Chile, and have been included within the hypodigm of the historic taxon Cimoliasaurus andium Deecke (nomen dubium). The specimen studied here likely represents the same taxon or a closely related form, showing slight differences in both size and ontogenetic stage. The preserved elements of this new skeleton afford comparison with several other late Maastrichtian specimens from Chile that were previously, albeit tentatively, referred to “C. andium”. The similarity of these specimens suggests that the late Maastrichtian elasmosaurid diversity of central Chile (excluding aristonectines) may be represented by taxa with low morphological disparity, or by a single taxon.

Gastroliths in Elasmosaur Pleisosaur Guts From Maastrichtian Cretaceous Antarctica

Gastroliths associated with an Aristonectes specimen (Plesiosauria, Elasmosauridae), López de Bertodano Formation (upper Maastrichtian) Seymour Island (Is. Marambio), Antarctic Peninsula

Authors:

O'Gorman et al

Abstract:

The occurrence of a large gastrolith set associated with a specimen referred to Aristonectes sp. is reported here for the first time. The specimen MLP 89-III-3-1 comes from Seymour Island (Is. Marambio), Antarctic Peninsula, López de Bertodano Formation (upper Maastrichtian). The gastrolith cluster is composed of 793 elements (534 in their presumed original state and about 259 that are broken). The gastroliths are described using sedimentological indices. The mean major axis of the gastroliths is 21 mm, the mean Maximum Projection Sphericity is 0.71 and the standard deviation is 0.11. According to Krumbein's classification, 43.3% are spheroidal (equant), 14.9% are cylindrical (prolate), 34.7% are discoidal and 7.1% are bladed (laminar). Following Powers' roundness categories, 10.1% are very rounded, 29.2% are rounded and 60.7% are subrounded. The mean Maximum Projection Sphericity value indicates a fluvial origin for the gastroliths. Petrographically, the gastroliths comprise rhyolitic volcanites (56.2%), quartz vein material (27.8%), subarkose arenites (14.5%) and laminated, radiolarian-rich mudstones and tuffs (1.5%). The potential geological sources are several formations from the Antarctic Peninsula, such as the Upper Jurassic Antarctic Peninsula Volcanic Group (rhyolitic volcanites), the Permian–Triassic Trinity Peninsula Group (subarkose arenites), and the Kimmeridgian–Berriasian Ameghino Formation (radiolarian-rich mudstones and tuffs). All these formations crop out within about 100 km of the locality where the specimen was collected. We also discuss how gastroliths were ingested, concluding that the ingestion was not done individually. Finally, this record of gastroliths provides evidence against the hypothesis of their use for buoyancy control.

A new Elasmosaurid Plesiosaur From Maastrichtian Cretaceous New Zealand

A new elasmosaurid plesiosaur from the lower Maastrichtian of North Canterbury, New Zealand

Authors:

Hiller et al

Abstract:

A postcranial specimen from the lower Maastrichtian levels of the Conway Formation, Middle Waipara River, North Canterbury, New Zealand shows clear elasmosaurid affinities, based on the articular faces, with a ventral notch, of the centra of cervical vertebrae. The ilia have some distinctive features such as a gracile shaft divided into two parts by a posterior “knee”, with the distal portion being longer than the proximal one, and the flattened distal end being slightly expanded and bearing an ovoid depression. These features differentiate this specimen from other elasmosaurids from the Weddellian Biogeographic Province, in which the ilia are known, but these are considered insufficient grounds on which to erect a new taxon. However, this specimen demonstrates a potentially greater elasmosaurid diversity in the lower Maastrichtian of the southern Hemisphere than previously appreciated. The gastrolith cluster associated with the bones has sedimentological features similar to those previously recorded in gastroliths of other elasmosaurids.

Santonian/Campanian Cretaceous Puskwaskau Formation Shows Diverse Marine Reptile Fauna Near Paleo Arctic Circle

Marine Reptiles (Plesiosauria and Mosasauridae) from the Puskwaskau Formation (Santonian–Campanian), West-Central Alberta

Authors:

Bell et al

Abstract:

Plesiosaurs and mosasaurs are identified from the Puskwaskau Formation of west-central Alberta, Canada. These deposits record the final stages during which the Western Interior Seaway remained open to the Boreal Sea to the North and therefore are important for determining the ranges of high-latitude marine reptiles. Polycotylid and elasmosaurid plesiosaurs shared these waters with russellosaurine (including plioplatecarpine) mosasaurs suggesting a diverse ecology of large-bodied marine predators occupied these high-latitude waters in the early Campanian. This locality, situated at 65°N paleolatitude, helps link the poorly known faunas from northern Canada with the better-known faunas from central and southern North America. Rare articulated material from the Puskwaskau Formation urges further investigation of this poorly explored unit.

Aristonectes quiriquinensis: a new Elasmosaur From Maastrichtian Cretaceous Chile

Aristonectes quiriquinensis, sp. nov., a new highly derived elasmosaurid from the upper Maastrichtian of central Chile

Authors:

Otero et al

Abstract:

This paper describes a new species of elasmosaurid plesiosaur, Aristonectes quiriquinensis, sp. nov., based on a partial skeleton recovered from upper Maastrichtian beds of the Quiriquina Formation of central Chile. The material described here consists of two skeletons, one collected near the village of Cocholgue, and a second juvenile specimen from Quiriquina Island. Prior to these finds, Aristonectes was viewed as a monospecific genus, including only the enigmatic Aristonectes parvidens, the holotype of which consists of an incomplete skull and incomplete postcranium. Other material referred to the genus includes an incomplete juvenile skull and other postcranial material from the upper Maastrichtian of Antarctica, as well as a partial skull from the Quiriquina Formation of central Chile. The relationships of Aristonectes have been controversial, with competing theories assigning the genus to Cryptoclididae, Elasmosauridae, and Aristonectidae; however, there is a developing consensus that Aristonectes is a derived elasmosaurid, and this paper gives strong evidence for this view. Comparison of the specimen here studied with the holotype of A. parvidens demonstrates that A. quiriquinensis is a distinct species. The completeness of the adult skeleton allows the first confident size estimates for adult Aristonectes. It is a large plesiosaurian with a relatively large skull with numerous homodont teeth, a moderately long and laterally compressed neck, and relatively narrow trunk, with slender and elongate forelimbs. The two specimens are restricted to the upper Maastrichtian of central Chile, posing questions concerning the austral circumpolar distribution of different elasmosaurids towards the end of the Cretaceous.

Neotony Or Larger Adult Size in Maastrichtian Cretaceous Plesiosaurs From Patagonia?

Reappraisal of Tuarangisaurus? cabazai (Elasmosauridae, Plesiosauria) from the Upper Maastrichtian of northern Patagonia, Argentina

Authors:

O'Gorman et al.

Abstract:

The holotype of Tuarangisaurus? cabazai Gasparini, Salgado and Casadio, 2003 (Elasmosauridae, Plesiosauria) from the Upper Maastrichtian Jagüel Formation (northern Patagonia, Argentina) is redescribed, its taxonomic status is reconsidered, and its phylogenetic relationships analysed. We conclude that it must be referred as an aristonectin elasmosaurid. The complete ilium of an Aristonectinae is described for the first time, and reveals a distinctive proximodistally elongated facet in its distal end. Aristonectins are the most commonly recorded Weddellian elasmosaurids. There is a high proportion of osteologically immature individuals (“juveniles”) within the investigated sample of specimens. Most of these are larger than other juvenile elasmosaurids, and apparently retain juvenile features at larger body sizes.