Evidence a Young Flightless Cretaceous Bird Hesperornis Escaped a Plesiosaur attack

Hesperornis escapes plesiosaur attack

Authors:

Martin et al

Abstract:

Evidence from the Pierre Shale (Late Cretaceous) of South Dakota is presented for an attack on a juvenile Hesperornis by a polycotylid plesiosaur. The wound healed and the Hesperornis grew to maturity. Evidence of survival provides our best information about predator prey interactions in the fossil record but are rare for birds where survival is an unlikely outcome.

Polycotylus latipinnis: a Redescription of Polycotylid Plesiosaur From Campanian Cretaceous South Dakota

Polycotylus latipinnis Cope (Plesiosauria, Polycotylidae), a nearly complete skeleton from the Niobrara Formation (Early Campanian) of southwestern South Dakota

Authors:

Schumacher et al

Abstract:

A nearly complete skeleton of Polycotylus latipinnis (SDSM 23020) from the upper Niobrara Formation (early Campanian) of South Dakota (U.S.A) greatly improves information for this formerly poorly known taxon. Specimens SDSM 23020 and YPM 1125 (paratype P. latipinnis) exhibit numerous postcranial characters that distinguish Polycotylus, in particular presacral vertebral count, nature of chevron facets, unique ilia, and highly derived paddles including five epipodial ossifications and increased hyperphalangy. Greater vertebral and phalangeal counts of Polycotylus are accompanied by exceptional foreshortening; thus, the relative body and limb proportions are likely similar to less derived polycotylids, with fewer, more elongate vertebrae and phalanges. The complete skull, derived among polycotylids, has short temporal fenestrae, elongate frontals, exceptionally slender parasphenoid with prominent cultriform process, and exceptionally long extensions of the angulars and splenials within the mandibular symphysis. Cladistic analysis indicates that Polycotylus nests firmly within derived Polycotylidae as a potential sister taxon to Dolichorhynchops osborni and Trinacromerum, despite a ‘primitive’ presacral vertebral count. Future improvements in available data, in particular better information regarding basal polycotylids, and refinement of character selection to nullify homoplasy could significantly alter the tree structure to show distinct subgroups within Polycotylidae. North American polycotylids with elongate temporal fenestrae, elongate podials, and relatively long vertebrae are confined to occurrences of late Cenomanian and earliest Turonian age, whereas polycotylids distinctly foreshortened in these respects are restricted to post-Turonian occurrences. Ilium morphology is highly variable among polycotylids and, in addition to taxonomic utility, may be in part attributable to sexual dimorphism.

Mortuneria: an Anarctic Filter Feed Maastrichtian Cretaceous Pleisosaur

If you’ve ever flipped through a book of prehistoric creatures or ambled through a major museum’s fossil halls, you’ve probably seen a plesiosaur.

These were the four-flippered marine reptiles that patrolled the seas for almost the entire Mesozoic era, some 250 to 66 million years ago. Some plesiosaurs were big-headed apex predators. Others had ludicrously long necks and snatched up fish and crustaceans with their little jaws.

Now, Marshall University paleontologist F. Robin O’Keefe has discovered that some of them filled their bellies in a way thought to be impossible for the aquatic reptiles: filter feeding.

The findings, presented last month at the annual Society of Vertebrate Paleontology meeting in Dallas, centered on a plesiosaur that has puzzled paleontologists for over 25 years. Named Mortuneria, this plesiosaur was found in the 66-million-year-old rock of Seymour Island, Antarctica.

Along with a closely related animal called Artistonectes found in Chile, Mortuneria was informally called one of “the hoopy jaws” for its large, hoop-shaped mouth that made it stand out from other known plesiosaurs, O’Keefe says.

Paleontologists Sankar Chatterjee and Bryan Small, who initially described Mortuneria in 1989, mooted the idea that the marine reptile’s odd jaw and needle-like teeth were adaptations for trapping small prey. So O’Keefe went back to re-describe the odd animal and seek out alternate feeding strategies.

“I look at it, and I was baffled”, O’Keefe says. But after weeks of hard work, he found that Mortuneria possessed an array of anatomical features that meant it must have been filter feeding. First of all, the teeth of Mortuneria don’t interlock like they do in other plesiosaurs.

link.

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.

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.

Open Water Marine Reptiles Resisted Extinction During Triassic Better

Selective extinction of Triassic marine reptiles during long-term sea-level changes illuminated by seawater strontium isotopes

Authors:

Kelley et al

Abstract:

The relationship between cycles of sea-level change and marine diversity has long been the subject of debate. Large predators may be particularly sensitive to changes in habitat availability and marine productivity driven by changes in sea-level, especially those dependent on nearshore benthic food resources. To test this relationship, we compared the proportional diversity of differing marine reptile ecotypes through the Triassic with the isotopic composition of seawater strontium (87Sr/86Sr), a geochemical index linked to tectonically controlled sea-level change. The proportional abundance of marine reptiles adapted toward a diet of shelled prey rose during times of rapid sea-level rise and fell during times of rapid sea-level fall, while open water forms were more resistant to these changes. Our results indicate that the rate of sea-level change, rather than the absolute magnitude of sea-level or flooded shelf area, played a role in shaping patterns of ecological diversification and ecologically selective extinction during the Triassic. The link between the isotopic composition of seawater strontium and the evolution of marine reptiles demonstrates that sea-level change played an important role in the structuring of marine ecosystems over geologic time.

Yunguisaurus: a new Specimen of the Ladinian Triassic Pistosauroid With Implications for Pleisosaur Origins

A new specimen of the Triassic pistosauroid Yunguisaurus, with implications for the origin of Plesiosauria (Reptilia, Sauropterygia)

Authors:

Sato et al

Abstract:

An adult skeleton of the pistosauroid sauropterygian Yunguisaurus liae reveals a number of morphological features not observed in the holotype, such as the complete morphology of the skull roof, stapes, atlas and axis, ventral view of the postcranium, and nearly complete limbs and tail. Size and morphological differences between the two specimens are mostly regarded as ontogenetic variation, and newly added data did not affect the phylogenetic relationships with other pistosauroids significantly. The number of mesopodia (11 carpals and 8 tarsals) exceeds that known in any other Triassic marine reptiles and does not serve as a precursor of the plesiosaurian pattern with fewer mesopodia of different topology; it demonstrates variability of the limb morphology among the Triassic pistosauroids. The pectoral girdles of Corosaurus, Augustasaurus and Yunguisaurus may indicate early stages of the adaptation towards the plesiosaurian style of paraxial limb movements with ventroposterior power stroke.

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.

New Finds Increase Late Cretaceous Antarctic Plesiosaur Diversity

Additions to the diversity of elasmosaurid plesiosaurs from the Upper Cretaceous of Antarctica

Authors:

1. Rodrigo A. Otero (a)
2. Sergio Soto-Acuña (a, b)
3. Alexander O. Vargas 9a)
4. David Rubilar-Rogers (b)
5. Roberto E. Yury-Yañez (c)
6. Carolina S. Gutstein (d)

Affiliations:

a. Red Paleontológica U-Chile, Laboratorio de Ontogenia y Filogenia, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Av. Las Palmeras 3425, Santiago, Chile

b. Área Paleontología, Museo Nacional de Historia Natural, Casilla 787, Santiago, Chile

c. Laboratorio de Zoología de Vertebrados, Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Av. Las Palmeras 3425, Santiago, Chile

d. Laboratorio de Ecofisiología, Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Santiago, Chile

Abstract:

Three specimens of elasmosaurid plesiosaurs (Sauropterygia, Plesiosauroidea) from Upper Cretaceous beds of Antarctica are described here. These include postcranial remains of a single adult individual recovered from late Maastrichtian beds of Marambio (= Seymour) Island, possessing distinctive cervical vertebrae with the transverse section of the centra having a triangular outline, a vertical groove on the rostral and caudal edge of the neural spines, and a deep articulation over the neural arch for the following postzygapohysis, while the scapula shows an unusually large and anteriorly recurved dorsal process. This combination of features is not known to occur in any adult, postcranial elasmosaurid genus recovered to date in the Upper Cretaceous of the Weddellian Biogeographic Province and could represent a new form. Additional specimens from James Ross Island comprise the first record of an Aristonectinae (Plesiosauria, Elasmosauridae) in late Campanian beds, being the oldest known record of this sub-family. Finally, a third specimen from the same age and locality reveals the presence of very-long necked elasmosaurids with affinities to typical representatives from the Upper Cretaceous of the Northern Hemisphere. These findings add to the known diversity of Upper Cretaceous elasmosaurids in high latitudes of the Southern Hemisphere.

Pleisosaur and Pliosaur Extinction and Evolution Through the Jurassic-Cretaceous Boundary

Faunal turnover of marine tetrapods during the Jurassic–Cretaceous transition

Authors:

1. Roger B. J. Benson (a)
2. Patrick S. Druckenmiller (b)

Affiliations:

a. Department of Earth Sciences, University of Oxford, Oxford, U.K.

b. Department of Geology and Geophysics, University of Alaska Museum, University of Alaska Fairbanks, Fairbanks, Alaska 99775, U.S.A.

Abstract:

Marine and terrestrial animals show a mosaic of lineage extinctions and diversifications during the Jurassic–Cretaceous transition. However, despite its potential importance in shaping animal evolution, few palaeontological studies have focussed on this interval and the possible climate and biotic drivers of its faunal turnover. In consequence evolutionary patterns in most groups are poorly understood. We use a new, large morphological dataset to examine patterns of lineage diversity and disparity (variety of form) in the marine tetrapod clade Plesiosauria, and compare these patterns with those of other organisms. Although seven plesiosaurian lineages have been hypothesised as crossing the Jurassic–Cretaceous boundary, our most parsimonious topology suggests the number was only three. The robust recovery of a novel group including most Cretaceous plesiosauroids (Xenopsaria, new clade) is instrumental in this result. Substantial plesiosaurian turnover occurred during the Jurassic–Cretaceous boundary interval, including the loss of substantial pliosaurid, and cryptoclidid diversity and disparity, followed by the radiation of Xenopsaria during the Early Cretaceous. Possible physical drivers of this turnover include climatic fluctuations that influenced oceanic productivity and diversity: Late Jurassic climates were characterised by widespread global monsoonal conditions and increased nutrient flux into the opening Atlantic-Tethys, resulting in eutrophication and a highly productive, but taxonomically depauperate, plankton. Latest Jurassic and Early Cretaceous climates were more arid, resulting in oligotrophic ocean conditions and high taxonomic diversity of radiolarians, calcareous nannoplankton and possibly ammonoids. However, the observation of discordant extinction patterns in other marine tetrapod groups such as ichthyosaurs and marine crocodylomorphs suggests that clade-specific factors may have been more important than overarching extrinsic drivers of faunal turnover during the Jurassic–Cretaceous boundary interval.

Mesozoic Marine Reptiles Were Warm Blooded?!

(image source: here)

Giant reptiles that ruled dinosaur-era seas might have been warm-blooded, a new study says.

Researchers found that ancient ocean predators possibly regulated their body temperatures, which allowed for aggressive hunting, deep diving, and fast swimming over long distances.

"These marine reptiles were able to maintain a high body temperature independently of the water temperature where they lived, from tropical to cold-temperate oceanic domains," said study co-author Christophe Lécuyer, a paleontologist at Université Claude Bernand Lyon 1 in France.

The prehistoric reptiles may have had body temperatures as high as 95 to 102 degrees Fahrenheit (35 to 39 degrees Celsius)—comparable to those of modern dolphins and whales, Lécuyer noted. (See whale pictures.)

Most modern reptiles and fish are cold-blooded, which means their internal temperatures vary along with those of the surrounding water.

Since the modern oceans' top predators—such as tuna and swordfish—are to some degree warm-blooded, this made the team wonder if ancient marine reptiles might have been, too, Lécuyer said.

Tuna and swordfish are homeothermic, or capable of keeping their body temperatures relatively constant, despite changing environmental temperatures. The predators are also partially endothermic, which means they can generate and retain enough heat to raise their body temperatures to high but stable levels.

Most animals thought of as warm-blooded, including mammals and birds, are also both homeothermic and endothermic.

Fossil Teeth Provide Sea-Reptile Clues

While dinosaurs dominated land during the Mesozoic period (251 million to 65 million years ago), three kinds of large swimming reptiles reigned in the seas—the dolphin-like ichthyosaurs, the serpentine mosasaurs, and the Loch Ness monster-like plesiosaurs. (See a prehistoric time line.)

By studying fossil teeth of fish that would have lived alongside these creatures, Lécuyer and colleagues were able to determine the teeth's oxygen isotopes, or atomic structures.

The levels of oxygen isotopes in teeth reflect those of the blood, which in turn reflect animals' body temperatures.

The team compared these results with oxygen-isotope compositions in modern-day fish that live in a variety of hot and cold environments.

Since most modern fish are cold-blooded, this data helped the team figure out the ocean temperatures of the ancient species' habitat.

Then the researchers compared oxygen-isotope data from the fossilized fish teeth with those seen in fossil-reptile teeth from the same areas.

"Enthralling" Sea-Reptile Findings

Homeothermy and endothermy in ichthyosaurs and plesiosaurs would make sense, as past studies of their body plans suggested the creatures were pursuit predators that needed to keep active, according to the study, published tomorrow in the journal Science.

The new data for mososaurs, which scientists suspect hunted by ambush, were more ambiguous, but are consistent with the idea that these reptiles could control their body temperatures to some degree, the authors write.

Whoa.

In a way, that mosasaurs were possibly cold blooded makes sense since they are relatively derived varanids. Even so...wow.