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"Godefroit, Pascal"
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Synchrotron scanning reveals amphibious ecomorphology in a new clade of bird-like dinosaurs
The recently discovered theropod
Halszkaraptor escuillei
reveals a novel basal dromaeosaurid clade, and its adaptations that suggest a semi-aquatic predatory lifestyle add an additional ecomorphology to those developed by non-avian maniraptorans.
Dawn of the dino-duck
A dinosaur discovered in the Cretaceous period of Mongolia belongs to a new subfamily of bird-like dinosaurs, which may have taken to water. Andrea Cau and colleagues describe
Halszkaraptor
, a small theropod with a number of unusual, potentially amphibious features. Synchrotron scanning reveals a domed head, a long, swan-like neck, a beak-like snout and several other adaptations that suggest that it spent at least some time in the water. The researchers group the finding with two other hitherto enigmatic and fragmentary finds to produce a new dinosaur subfamily, the Halszkaraptorinae. This adds another string to the versatile bow of maniraptoran theropods, which comprise a wide range of highly diverse forms, including birds.
Maniraptora includes birds and their closest relatives among theropod dinosaurs
1
,
2
,
3
,
4
,
5
. During the Cretaceous period, several maniraptoran lineages diverged from the ancestral coelurosaurian
bauplan
and evolved novel ecomorphologies, including active flight
2
, gigantism
3
, cursoriality
4
and herbivory
5
. Propagation X-ray phase-contrast synchrotron microtomography of a well-preserved maniraptoran from Mongolia, still partially embedded in the rock matrix, revealed a mosaic of features, most of them absent among non-avian maniraptorans but shared by reptilian and avian groups with aquatic or semiaquatic ecologies
6
,
7
,
8
,
9
,
10
,
11
,
12
,
13
,
14
. This new theropod,
Halszkaraptor escuilliei
gen. et sp. nov., is related to other enigmatic Late Cretaceous maniraptorans from Mongolia
15
,
16
in a novel clade at the root of Dromaeosauridae
17
. This lineage adds an amphibious ecomorphology to those evolved by maniraptorans: it acquired a predatory mode that relied mainly on neck hyperelongation for food procurement, it coupled the obligatory bipedalism of theropods with forelimb proportions that may support a swimming function, and it developed postural adaptations convergent with short-tailed birds.
Journal Article
Unusual pectoral apparatus in a predatory dinosaur resolves avian wishbone homology
The furcula is a distinctive element of the pectoral skeleton in birds, which strengthens the shoulder region to withstand the rigor of flight. Although its origin among theropod dinosaurs is now well-supported, the homology of the furcula relative to the elements of the tetrapod pectoral girdle (i.e., interclavicle
vs
clavicles) remains controversial. Here, we report the identification of the furcula in the birdlike theropod
Halszkaraptor escuilliei
. The bone is unique among furculae in non-avian dinosaurs in bearing a visceral articular facet in the hypocleideal end firmly joined to and overlapped by the sternal plates, a topographical pattern that supports the primary homology of the furcula with the interclavicle. The transformation of the interclavicle into the furcula in early theropods is correlated to the loss of the clavicles, and reinforced the interconnection between the contralateral scapulocoracoids, while relaxing the bridge between the scapulocoracoids with the sternum. The function of the forelimbs in theropod ancestors shifted from being a component of the locomotory quadrupedal module to an independent module specialized to grasping. The later evolution of novel locomotory modules among maniraptoran theropods, involving the forelimbs, drove the re-acquisition of a tighter connection between the scapulocoracoids and the interclavicle with the sternal complex.
Journal Article
Anatomical description and digital reconstruction of the skull of Jeholosaurus shangyuanensis (Dinosauria, Ornithopoda) from China
Ornithopod dinosaurs appeared during the Middle Jurassic, but it was in the Lower Cretaceous they started their successful evolutionary history. Different phylogenies describing the evolutionary relationships of Ornithopoda are mostly based on cranial features, however there is a lack of well-preserved and complete skulls for the basal member of the clade, hampering our knowledge on the mode and tempo of these herbivorous dinosaurs. Here we describe YLSNHM 01942, a well-preserved skull of a juvenile neornithischian from the Liaoning Province of China. The specimen was scanned with a μCT scan, and all the elements were segmented and extrapolated for description. The specimen shows a ventral deformation due to the compression of the sediment, and a few rostral elements were artificially added. The specimen is attributed to the basal ornithopod Jeholosaurus shangyuanensis because of the presence of a large foramen in the quadratojugal, however it lacks the nodular ornamentation on the postorbital and jugal, herein interpreted as an ontogenetic feature. This, together with the disarticulation degree of the cranial elements, suggest YLSNHM 01942 represents a juvenile Jeholosaurus . The endosseous labyrinth is tentatively reconstructed, although the disarticulation of the neurocranial bones hampers its complete reconstruction. Thanks to the analysis of previously undescribed inner neurocranial bones (such as the prootics, the exoccipital/ophistotic, basioccipital, and basisphenoid), we improve the previous phylogenetical scoring for J . shangyuanensis , and perform a phylogenetical analysis adding the basal ornithopod Changmiania liaoningensis and the recently re-evaluated Ajkaceratops kozmai . The phylogenetical analysis reports a well-supported base of Ornithopoda, with C . liaoningensis as the most basal ornithopod, and a resolved topology for Nanosaurus agilis , Changchunsaurus parvus , Haya griva , Yandusaurus hongheensis and J . shangyuanensis .
Journal Article
High Diversity in Cretaceous Ichthyosaurs from Europe Prior to Their Extinction
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.
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.
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.
Journal Article
A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds
The complete skeleton of a new avialan dinosaur from the Tiaojishan Formation (Middle–Late Jurassic period) of Liaoning Province, China, is described and included in a comprehensive phylogenetic analysis of basal Paraves.
Archaeopteryx
back on its perch
Discoveries of feathered theropod dinosaurs in China during the past two decades have prompted dramatic revisions of our ideas of the evolution of birds and the origins of flight — including the suggestion that the iconic fossil
Archaeopteryx
might have lain some distance from the ancestry of modern birds. Now
Archaeopteryx
is back on its perch with the discovery of yet another bird-like dinosaur, from the Tiaojishan Formation (Middle–Late Jurassic) of Liaoning Province, China. A new phylogenetic analysis restores
Archaeopteryx
as an early diverging avialan and realigns Troodontidae as the sister-group for Avialae. These results are consistent with early diversification of birds in Asia during the Middle–Late Jurassic, and a single origin for avian forelimb-powered flapping flight.
The recent discovery of small paravian theropod dinosaurs with well-preserved feathers in the Middle–Late Jurassic Tiaojishan Formation of Liaoning Province (northeastern China)
1
,
2
,
3
,
4
has challenged the pivotal position of
Archaeopteryx
3
,
4
, regarded from its discovery to be the most basal bird. Removing
Archaeopteryx
from the base of Avialae to nest within Deinonychosauria implies that typical bird flight, powered by the forelimbs only, either evolved at least twice, or was subsequently lost or modified in some deinonychosaurians
3
,
5
. Here we describe the complete skeleton of a new paravian from the Tiaojishan Formation of Liaoning Province, China. Including this new taxon in a comprehensive phylogenetic analysis for basal Paraves does the following: (1) it recovers it as the basal-most avialan; (2) it confirms the avialan status of
Archaeopteryx
; (3) it places Troodontidae as the sister-group to Avialae; (4) it supports a single origin of powered flight within Paraves; and (5) it implies that the early diversification of Paraves and Avialae took place in the Middle–Late Jurassic period.
Journal Article
Reduced plumage and flight ability of a new Jurassic paravian theropod from China
Feathered dinosaurs from the Middle-Late Jurassic of north-eastern China have recently been described. Here, a new paravian dinosaur, characterized by less extensive feathers on its limbs and tail, shows that the plumage of theropods was already diversified and adapted to different ecological niches by the Late Jurassic.
Feathered theropods were diverse in the Early Cretaceous Jehol Group of western Liaoning Province, China. Recently, anatomically distinct feathered taxa have been discovered in the older Middle-Late Jurassic Tiaojishan Formation in the same region. Phylogenetic hypotheses including these specimens have challenged the pivotal position of
Archaeopteryx
in bird phylogeny. Here we report a basal troodontid from the Tiaojishan Formation that resembles
Anchiornis
, also from Jianchang County (regarded as sister-taxa). The feathers of
Eosinopteryx
are less extensive on the limbs and tail than
Anchiornis
and other deinonychosaurians. With reduced plumage and short uncurved pedal claws,
Eosinopteryx
would have been able to run unimpeded (with large foot remiges cursorial locomotion was likely problematic for
Anchiornis
).
Eosinopteryx
increases the known diversity of small-bodied dinosaurs in the Jurassic, shows that taxa with similar body plans could occupy different niches in the same ecosystem and suggests a more complex picture for the origin of flight.
Journal Article
Resolving the long-standing enigmas of a giant ornithomimosaur Deinocheirus mirificus
Two almost complete skeletons are presented for the theropod dinosaur
Deinocheirus mirificus
, revealing a humpbacked form with a duckbill-like skull.
A giant dinosaur reborn
For almost 50 years, the strange theropod dinosaur
Deinocheirus mirificus
has been regarded as one of the most intriguing puzzles in palaeontology. Known only from two gigantic forelimbs unearthed in Mongolia in 1965, it had been variously described as an ornithomimid, a therizinosaur or a member of a completely new theropod clade. New excavations have now revealed two almost entire skeletons of the creature, enabling Yuong-Nam Lee
et al
. to offer a detailed picture of
D. mirificus
. What emerges is a gigantic creature with a duckbill-like skull and a humped back, the largest known member of the ornithomimosaurs, living in a damp environment, with plants and fish as part of the diet of
D. mirificus
.
The holotype of
Deinocheirus mirificus
was collected by the 1965 Polish–Mongolian Palaeontological Expedition at Altan Uul III in the southern Gobi of Mongolia
1
. Because the holotype consists mostly of giant forelimbs (2.4 m in length) with scapulocoracoids
2
, for almost 50 years
Deinocheirus
has remained one of the most mysterious dinosaurs. The mosaic of ornithomimosaur and non-ornithomimosaur characters in the holotype has made it difficult to resolve the phylogenetic status of
Deinocheirus
3
,
4
. Here we describe two new specimens of
Deinocheirus
that were discovered in the Nemegt Formation of Altan Uul IV in 2006 and Bugiin Tsav in 2009. The Bugiin Tsav specimen (MPC-D 100/127) includes a left forelimb clearly identifiable as
Deinocheirus
and is 6% longer than the holotype. The Altan Uul IV specimen (MPC-D 100/128) is approximately 74% the size of MPC-D 100/127. Cladistic analysis indicates that
Deinocheirus
is the largest member of the Ornithomimosauria; however, it has many unique skeletal features unknown in other ornithomimosaurs, indicating that
Deinocheirus
was a heavily built, non-cursorial animal with an elongate snout, a deep jaw, tall neural spines, a pygostyle, a U-shaped furcula, an expanded pelvis for strong muscle attachments, a relatively short hind limb and broad-tipped pedal unguals. Ecomorphological features in the skull, more than a thousand gastroliths, and stomach contents (fish remains) suggest that
Deinocheirus
was a megaomnivore that lived in mesic environments.
Journal Article
A new basal ornithopod dinosaur from the Lower Cretaceous of China
A new basal ornithopod dinosaur, based on two nearly complete articulated skeletons, is reported from the Lujiatun Beds (Yixian Fm, Lower Cretaceous) of western Liaoning Province (China). Some of the diagnostic features of Changmiania liaoningensis nov. gen., nov. sp. are tentatively interpreted as adaptations to a fossorial behavior, including: fused premaxillae; nasal laterally expanded, overhanging the maxilla; shortened neck formed by only six cervical vertebrae; neural spines of the sacral vertebrae completely fused together, forming a craniocaudally-elongated continuous bar; fused scapulocoracoid with prominent scapular spine; and paired ilia symmetrically inclined dorsomedially, partially covering the sacrum in dorsal view. A phylogenetic analysis places Changmiania liaoningensis as the most basal ornithopod dinosaur described so far. It is tentatively hypothesized that both Changmiania liaoningensis specimens were suddenly entrapped in a collapsed underground burrow while they were resting, which would explain their perfect lifelike postures and the complete absence of weathering and scavenging traces. However, further behavioural inference remains problematic, because those specimens lack extensive sedimentological and taphonomic data, as it is also the case for most specimens collected in the Lujiatun Beds so far.
Journal Article
Correction: High Diversity in Cretaceous Ichthyosaurs from Europe Prior to Their Extinction
The images for Figures 17, 18, 19, and 20 were incorrectly switched.
Citation: Fischer V, Bardet N, Guiomar M, Godefroit P (2014) Correction: High Diversity in Cretaceous Ichthyosaurs from Europe Prior to Their Extinction.
Journal Article