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.

A Very Complete Triassic Plesiosaur Found in Germany

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The Hydrodynamics of Plesiosaurs

Millions of years ago when the dinosaurs were walking around on the earth, there was a type of marine reptile called a plesiosaur that was swimming in the seas. Plesiosaurs were reptiles that had evolved to live in the ocean, and had four big flippers that they used to swim with. These flippers were similar to the flippers of a turtle or sea lion, but whereas these creatures only really use their front two for propulsion, plesiosaurs used all four.

link.

The First Polycotylid Plesiosaur From Coniacian/Campanian Cretaceous Antarctica

First record of Polycotylidae (Sauropterygia, plesiosauria) from the Upper Cretaceous of Antarctica

Authors:

Novas et al

Abstract:

In the present paper we report the incomplete skeleton of an indeterminate polycotylid that includes the articulated pelvic girdle. The material was collected from the Alpha Member of the Santa Marta Formation (upper Coniacian–lower Campanian) on James Ross Island, Antarctic Peninsula. The specimen is referred to the Polycotylidae on the basis of its very elongate ischia and rimmed anterior and posterior articular surfaces of the dorsal vertebrae. Additionally, the caudal vertebrae show confluent parapophyses and neural arch facets. The present report constitutes the first record for polycotylids in Antarctica, being an important addition to the fossil marine reptile diversity. Polycotylids are a scarce component of the Weddellian herpetofauna, which are dominated by aristonectine and non–aristonectine elasmosaurids. In contrast, in Northern Hemisphere assemblages, polycotylids are an important component of the plesiosaur diversity. The scarcity of polycotylids may constitute another distinctive feature of Weddellian plesiosaur faunas.

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.

Colymbosaurus megadeirus: A Reassessment of Kimmeridgian Jurassic Plesiosaur Paleodiversity

Anatomy of Colymbosaurus megadeirus (Reptilia, Plesiosauria) from the Kimmeridge Clay Formation of the U.K., and high diversity among Late Jurassic plesiosauroids

Authors:

Benson et al

Abstract:

We describe the syntype postcranial skeletons of the cryptoclidid plesiosauroid Colymbosaurus megadeirus. C. megadeirus is the type species of Colymbosaurus, and one other valid species, C. svalbardensis, is known. Although it is in widespread usage, C. trochanterius is a not valid species, although the presence of an anteroposteriorly oriented ridge bisecting the distal surfaces of the holotype humerus allows its referral to Colymbosaurus sp. Some specimens previously referred to C. trochanterius, including the holotype of ‘Plesiosaurus’ manselii, lack this feature, or show other differences from our hypodigm, suggesting that they are taxonomically distinct from Colymbosaurus, and countering previous suggestions that the Kimmeridge Clay Formation represents a depauperate plesiosauroid fauna. Substantial differences between the atlas-axis complexes and cervical vertebrae of Kimmerosaurus langhami, ‘Plesiosaurus’ manselii, C. megadeirus, and specimens referred here to cf. Spitrasaurus indicate that at least four plesiosauroid taxa were present in the Kimmeridge Clay Formation. This proposition is also supported by coracoid morphotypes, and demonstrates that Late Jurassic plesiosauroids were taxonomically diverse. Most Late Jurassic–Early Cretaceous cryptoclidids belong to a monophyletic Colymbosaurinae, but Kimmerosaurus and its sister taxon Tatenectes originated independently from Middle Jurassic cryptoclidids.

Arctic Plesiosaurs From Aptian Cretaceous Nunavut, Canada

Arctic plesiosaurs from the Lower Cretaceous of Melville Island, Nunavut, Canada

Authors:

Vavrek et al

Abstract:

An expedition to Melville Island in Nunavut, Canada, recovered the fragmentary fossils of several plesiosaurs from non-marine deposits of the Hauterivian–Aptian Isachsen Formation. These plesiosaur fossils are some of the oldest Early Cretaceous records of the group in North America, and they likely predate the formation of a continuous Western Interior Seaway. The plesiosaurs from Melville Island appear to be primarily juveniles, and would have been living in a region that experienced at least seasonally cool temperatures. The presence of these fossils in a fluvial deposit support previous suggestions that juvenile plesiosaurs may have preferentially inhabited shallower waters rather than open marine environments. These fossils also show that polycotylid plesiosaurs were able to rapidly disperse and colonize high latitude coastal regions, as their occurrence in Arctic Canada only slightly postdates the first confirmed appearance of the group in Australia.

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.

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.

Evidence for Caudal Fins in Plesiosaurs From the Toarcian Jurassic

MORPHOLOGY OF THE CAUDAL VERTEBRAE IN RHOMALEOSAURUS ZETLANDICUS AND A REVIEW OF THE EVIDENCE FOR A TAIL FIN IN PLESIOSAURIA

Author:

Adam S. Smith

Abstract:

The holotype of the large plesiosaurian Rhomaleosaurus zetlandicus from the Toarcian (Lower Jurassic) of England comprises an almost complete skeleton, including the caudal vertebral series. The osteology of the tail is described and two morphological characteristics are interpreted as evidence for a caudal fin in Rhomaleosaurus: 1. A distinct node consisting of two relatively anteroposteriorly shortened vertebrae; and 2. Laterally compressed terminal caudal centra. This inference is based on osteological correlates derived from other marine reptile groups that possessed a vertically oriented bilobed dermal tail fin in life (ichthyosaurs, thalattosuchian crocodylomorphs, and mosasaurs). This corroborates evidence from other plesiosaurian taxa and suggests that a caudal fin may have been widespread among plesiosaurians, with implications for locomotion and behavior.

Plesiosaurs Had Evolved by the Carnian Triassic

New information on Bobosaurus forojuliensis (Reptilia: Sauropterygia): implications for plesiosaurian evolution

Authors:

1. Matteo Fabbri (a)
2. Fabio M. Dalla Vecchia (b)
3. Andrea Cau (c)

Affiliations:

a. Dipartimento di Scienze della Terra , Università degli studi di Firenze , Via La Pira 4, I-50121 , Firenze , Italy

b. Institut Català de Paleontologia ‘Miquel Crusafont’ , C/Escola Industrial 23, E-08201 , Sabadell , Spain

c. Museo Geologico e Paleontologico ‘Giovanni Capellini’

Abstract:

Preparation of the holotype specimen of Bobosaurus forojuliensis, a large sauropterygian from the lower Carnian of northeastern Italy, revealed new morphological data relevant in establishing its phylogenetic affinities among pistosauroid taxa and its relationships with plesiosaurians. Inclusion of B. forojuliensis in two phylogenetic analyses focusing, respectively, on sauropterygians and pistosauroids agreed in placing the Italian taxon as closer to plesiosaurians than to other pistosauroids. The phylogenetic interpretation of Bobosaurus was not biased by assumptions on character weighting, is consistent with its relatively younger age compared to most pistosauroids, extends the fossil record of the plesiosaurian basal lineage back to the Carnian and supports the earliest diversification of the clade during the Late Triassic in agreement with the record of several distinct lineages of rhomaleosaurids, plesiosauroids and pliosauroids in the lowermost Jurassic. Bobosaurus shows that the evolution of the plesiosaurian body plan from the ancestral pistosauroid grade was a step-wise process, and that some of the vertebral and appendicular specialisations of Jurassic and Cretaceous plesiosaurians had already developed in the earliest Late Triassic.