scholarly journals A new Barremian (Early Cretaceous) ichthyosaur from western Russia

2018 ◽  
Author(s):  
Valentin Fischer ◽  
Edwige Masure ◽  
Maxim S. Arkhangelsky ◽  
Pascal Godefroit
Keyword(s):  
Phylogenetic Analysis ◽  
Early Cretaceous ◽  
Sister Taxon ◽  
New Taxon ◽  
Skull Roof

A new ophthalmosaurid ichthyosaur, Sveltonectes insolitus, gen. et sp. nov., is described from a sub-complete and three-dimensionally preserved specimen from the late Barremian of western Russia. This new taxon is supported by 11 cranial, dental, and postcranial autapomorphies, and is also characterized by features previously considered as autapomorphic for some other Ophthalmosauridae, such as a processus narialis on the prefrontal and relatively long hind fins with pre- and postaxial accessory digits. We conducted a new phylogenetic analysis of Thunnosauria, which supports a ‘Stenopterygius’ origin for Ophthalmosauridae. Sveltonectes is regarded as the sister taxon of Aegirosaurus, which shares a similar skull roof construction. Contrary to most other Cretaceous ichthyosaurs, Sveltonectes is characterized by delicate and sharply pointed teeth, confirming that the ophthalmosaurids were ecologically highly diversified during the Early Cretaceous.

scholarly journals A new iguanodontian (Dinosauria: Ornithopoda) from the Early Cretaceous of Mongolia

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5300
Author(s):  
Terry A. Gates ◽  
Khishigjav Tsogtbaatar ◽  
Lindsay E. Zanno ◽  
Tsogtbaatar Chinzorig ◽  
Mahito Watabe
Keyword(s):  
Phylogenetic Analysis ◽  
Growth Stage ◽  
Phylogenetic Analyses ◽  
Type Specimen ◽  
Sister Taxon ◽  
New Taxon ◽  
Time Of Death ◽  
The North ◽  
Unusual Combination ◽  
Relationship Of

We describe a new iguanodontian ornithopod,Choyrodon barsboldigen. et sp. nov. from the Albian-aged Khuren Dukh Formation of Mongolia based on several partial skeletons interpreted to represent a subadult growth stage based on osteohistological features. This new taxon is diagnosed by many autapomorphies of the maxilla, nasal, lacrimal, opisthotic, predentary, and surangular.Choyrodondisplays an unusual combination of traits, possessing an open antorbital fenestra (a primitive ornithopod trait) together with derived features such as a downturned dentary and enlarged narial fenestra. Histological imaging suggests that the type specimen ofChoyrodonwould have been a subadult at the time of death. Phylogenetic analysis of two different character matrices do not positChoyrodonto be the sister taxon or to be more primitive than the iguanodontianAltirhinus kurzanovi, which is found in the same formation. The only resolved relationship of this new taxon is that it was hypothesized to be a sister-taxon with the North American speciesEolambia caroljonesa. Though discovered in the same formation andChoyrodonbeing smaller-bodied thanAltirhinus, it does not appear that the former species is an ontogimorph of the latter. Differences in morphology and results of the phylogenetic analyses support their distinction although more specimens of both species will allow better refinement of their uniqueness.

scholarly journals A derived dryolestid mammal indicates possible insular endemism in the Late Jurassic of Germany

2021 ◽  
Vol 108 (3) ◽  
Author(s):  
Thomas Martin ◽  
Alexander O. Averianov ◽  
Julia A. Schultz ◽  
Achim H. Schwermann ◽  
Oliver Wings
Keyword(s):  
Phylogenetic Analysis ◽  
Early Cretaceous ◽  
Lower Cretaceous ◽  
Middle Jurassic ◽  
Late Jurassic ◽  
New Taxon ◽  
Lower Saxony ◽  
Therian Mammal ◽  
Geological Age ◽  
Near Shore

AbstractThe Langenberg Quarry near Bad Harzburg has yielded the first Jurassic stem therian mammal of Germany, recovered from Kimmeridgian (Late Jurassic) near shore deposits of a palaeo-island within the Lower Saxony Basin of the European archipelago. The new stem therian is represented by one lower and three upper molars. Hercynodon germanicus gen. et sp. nov. is attributed to the Dryolestidae, a group of pretribosphenic crown mammals that was common in western Laurasia from the Middle Jurassic to the Early Cretaceous. The new taxon is characterised by small size, a reduced cusp pattern in the upper molars lacking a metacone, and enhancement of the shearing crests paracrista and metacrista. Phylogenetic analysis identified Hercynodon gen. nov. as sister taxon of Crusafontia from the Lower Cretaceous (Barremian) of Spain. Both taxa belong to an endemic European clade of dryolestids, including also Achyrodon and Phascolestes from the earliest Cretaceous (Berriasian) of England. Despite its greater geological age, Hercynodon gen. nov. is the most derived representative of that clade, indicated by the complete reduction of the metacone. The discrepancy between derived morphology and geological age may be explained by an increased rate of character evolution in insular isolation. Other insular phenomena have earlier been observed in vertebrates from the Langenberg Quarry, such as dwarfism in the small sauropod Europasaurus, and possible gigantism in the morganucodontan mammaliaform Storchodon and the pinheirodontid multituberculate mammal Teutonodon which grew unusually large.

scholarly journals A New Early Cretaceous lizard in Myanmar Amber with Exceptionally Preserved Integument

2021 ◽  
Author(s):  
Andrej Čerňanský ◽  
Edward L. Stanley ◽  
Juan D. Daza ◽  
Arnau Bolet ◽  
J. Salvador Arias ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Morphological Analysis ◽  
Sister Taxon ◽  
Phylogenetic Position ◽  
Pectoral Girdle ◽  
New Taxon ◽  
Anterior Portion ◽  
External Appearance ◽  
Rare Opportunity ◽  
Rule Out

Abstract We here report on a well-preserved juvenile lizard specimen in Albian amber (ca. 110 mya) from the Hkamti site in Myanmar. This new taxon, Retinosaurus hkamtiensis gen. et sp. nov., is represented by an articulated skull and the anterior portion of the trunk, including the pectoral girdle and forelimbs. The ocular skeleton (scleral ossicles) and eyelid are also visible, and the specimen exhibits pristine detail of the integument (of both head and body). In a combined molecular and morphological analysis, Retinosaurus was consistently recovered as a scincoid lizard (i.e. Scinciformata), as the sister taxon to the Mexican Cretaceous genus Tepexisaurus + Xantusiidae. However, the phylogenetic position of Retinosaurus should be interpreted with caution. We cannot not rule out the possibility that Retinosaurus represents a separate lineage of uncertain phylogenetic position, as it is the case for many Jurassic and Cretaceous taxa. Nonetheless, this fossil offers a rare opportunity to glimpse the external appearance of one group of lizards during the Early Cretaceous.

scholarly journals Osteology of the Permian temnospondyl amphibian <i>Glanochthon lellbachae</i> and its relationships

Fossil Record ◽  
2021 ◽  
Vol 24 (1) ◽  
pp. 49-64
Author(s):  
Rainer R. Schoch
Keyword(s):  
Phylogenetic Analysis ◽  
Lateral Margin ◽  
Sister Taxon ◽  
Time Interval ◽  
New Taxon ◽  
Early Permian ◽  
Apex Predators ◽  
Trophic Guild ◽  
Long Time ◽  
Registration Date

Abstract. The early Permian Meisenheim Formation of the Saar–Nahe Basin (Germany) is famous for its richness in vertebrate fossils, among which the temnospondyls were present with microvores and fish-eating apex predators. The latter trophic guild was occupied exclusively by the genus Sclerocephalus in that basin within a long time interval up to M8, whereas in M9, a new taxon, Glanochthon lellbachae, appeared. This taxon is defined by (1) a preorbital region 1.8–2.0 times as long as the postorbital skull table, (2) dermal ornament with tall radial ridges, (3) a prefrontal anteriorly wider with straight lateral margin, (4) a squamosal posteriorly only half as wide as the quadratojugal, (5) phalanges of manus and pes long and gracile, (6) carpals unossified in adults, and (7) tail substantially longer than skull and trunk combined. Phylogenetic analysis finds that G. lellbachae forms the basal sister taxon of the stratigraphically younger G. angusta and G. latirostre and that this clade nests within the paraphyletic taxon Sclerocephalus, with S. nobilis forming the sister taxon of the genus Glanochthon (urn:lsid:zoobank.org:act:3038F794-17B9-4FCA-B241-CCC3F4423651; registration date: 15 March 2021).

A new ceratopsid from the Foremost Formation (middle Campanian) of Alberta

2012 ◽  
Vol 49 (10) ◽  
pp. 1251-1262 ◽  
Author(s):  
Michael J. Ryan ◽  
David C. Evans ◽  
Kieran M. Shepherd
Keyword(s):  
Phylogenetic Analysis ◽  
Type Species ◽  
New Genus ◽  
Sister Taxon ◽  
Low Density ◽  
New Taxon

Xenoceratops foremostensis gen. et. sp. nov., a new centrosaurine ceratopsid from the Foremost Formation (Campanian) of Alberta, is described based on frill material from at least three adult-sized individuals collected from a low-density bone bed. The material can be assigned to Centrosaurinae based on features of the preserved squamosal. Although the parietals are incomplete, the shape of the diagnostic parietal can be inferred from several overlapping serial elements. The parietal of the new taxon shares with all other centrosaurines, except Centrosaurus apertus , spike-like ornamentation at the posterolateral (P3) locus under traditional coding methods. At approximately 78 Ma, it is the oldest known Canadian ceratopsid, approximately 0.5 Ma older than Albertaceratops from the lower Oldman Formation of Canada and approximately 1.0 Ma younger than Diabloceratops from the Wahweap Formation of Utah. A phylogenetic analysis resolves the new taxon as the basalmost centrosaurine and places Centrosaurus brinkmani as the sister taxon to Styracosaurus albertensis . The type species of Centrosaurus brinkmani is moved to a new genus.

scholarly journals A primitive clupeomorph from the Albian Loon River Formation (Northwest Territories, Canada)

2016 ◽  
Vol 53 (4) ◽  
pp. 331-342 ◽  
Author(s):  
Oksana Vernygora ◽  
Alison M. Murray ◽  
Mark V.H. Wilson
Keyword(s):  
Phylogenetic Analysis ◽  
New Species ◽  
Northwest Territories ◽  
Early Cretaceous ◽  
The Body ◽  
New Taxon ◽  
Ventral Margin ◽  
Sensory Canal ◽  
Diagnostic Characters ◽  
Incertae Sedis

Foreyclupea loonensis, gen. et sp. nov., is described from the early–middle Albian Loon River Formation of the Northwest Territories, Canada. The only specimen of the new species was originally described as a part of an enigmatic taxon Erichalcis arcta in 1975, which was assigned to the Clupeomorpha. Since then, E. arcta has proven to be a composite taxon, made up of clupeomorph and non-clupeomorph specimens. The non-clupeomorph material was redescribed as a Euteleostei incertae sedis and retained the species name. Described herein is the fossil clupeomorph specimen originally assigned to Erichalcis arcta. As in other members of the superorder Clupeomorpha, the ventral margin of the body in the specimen is covered with spiny scutes, and the supratemporal commissural sensory canal passes through the parietals. Along with these diagnostic characters, the new taxon also shows primitive traits of the basal members of the group, including a medioparietal skull roof, unfused halves of the neural spines of the abdominal vertebrae, and no evidence of presence of the recessus lateralis. When included in a phylogenetic analysis of the Early Cretaceous clupeomorphs, the new species forms a clade with the Early Cretaceous clupeomorphs from Mexico and Brazil, Ranulfoichthys dorsonudum and Scutatuspinosus itapagipensis, respectively.

scholarly journals A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7247 ◽  
Author(s):  
Scott Hartman ◽  
Mickey Mortimer ◽  
William R. Wahl ◽  
Dean R. Lomax ◽  
Jessica Lippincott ◽  
...  
Keyword(s):  
Phylogenetic Analysis ◽  
North America ◽  
Early Cretaceous ◽  
Late Jurassic ◽  
New Taxon ◽  
Morrison Formation ◽  
Postcranial Skeleton ◽  
Avian Flight ◽  
Multiple Alternative ◽  
Limb Proportions

The last two decades have seen a remarkable increase in the known diversity of basal avialans and their paravian relatives. The lack of resolution in the relationships of these groups combined with attributing the behavior of specialized taxa to the base of Paraves has clouded interpretations of the origin of avialan flight. Here, we describeHesperornithoides miesslerigen. et sp. nov., a new paravian theropod from the Morrison Formation (Late Jurassic) of Wyoming, USA, represented by a single adult or subadult specimen comprising a partial, well-preserved skull and postcranial skeleton. Limb proportions firmly establishHesperornithoidesas occupying a terrestrial, non-volant lifestyle. Our phylogenetic analysis emphasizes extensive taxonomic sampling and robust character construction, recovering the new taxon most parsimoniously as a troodontid close toDaliansaurus,Xixiasaurus, andSinusonasus. Multiple alternative paravian topologies have similar degrees of support, but proposals of basal paravian archaeopterygids, avialan microraptorians, andRahonavisbeing closer to Pygostylia than archaeopterygids or unenlagiines are strongly rejected. All parsimonious results support the hypothesis that each early paravian clade was plesiomorphically flightless, raising the possibility that avian flight originated as late as the Late Jurassic or Early Cretaceous.

scholarly journals The Biggest Megaraptoridae (Theropoda: Coelurosauria) of South America

2021 ◽  
Author(s):  
Alexis M. Aranciaga Rolando ◽  
Matias J. Motta ◽  
Federico L. Agnolín ◽  
Makoto Manabe ◽  
Takanobu Tsuihiji ◽  
...  
Keyword(s):  
Phylogenetic Analysis ◽  
South America ◽  
Early Cretaceous ◽  
South American ◽  
New Taxon ◽  
Santa Cruz ◽  
Monophyletic Clade ◽  
Present Contribution ◽  
Anatomical Features ◽  
Top Predators

Abstract Megaraptorans are a theropod clade distributed in former Gondwana landmasses and Asia. Most members of the clade are known from early Cretaceous to Turonian times whereas Maastrichtian megaraptorans are known just from isolated and poorly informative remains. The aim of present contribution is to describe a partial skeleton of a megaraptorid coming from Maastrichtian beds at Santa Cruz province, Argentina. This new taxon constitutes the most informative megaraptoran from post-Turonian beds. Phylogenetic analysis nested the new taxon together with South American megaraptorans in a monophyletic clade, whereas Australian and Asian members constitute successive stem groups. South American forms differ from more basal megaraptorans in several anatomical features and in being much larger and more robustly built. It is possible that the Cenomanian-Turonian extinction of carcharodontosaurids was allowed to megaraptorans to occupy the niche of top predators in South America.

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

2015 ◽  
Vol 94 (1) ◽  
pp. 109-120 ◽  
Author(s):  
R. Araújo ◽  
M.J. Polcyn ◽  
A.S. Schulp ◽  
O. Mateus ◽  
L.L. Jacobs ◽  
...  
Keyword(s):  
Phylogenetic Analysis ◽  
Sister Taxon ◽  
New Taxon ◽  
Swimming Style

AbstractWe 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.

scholarly journals Evolutionary significance of the blastozoan Eumorphocystis and its pseudo-arms

2020 ◽  
pp. 1-17
Author(s):  
Thomas E. Guensburg ◽  
James Sprinkle ◽  
Rich Mooi ◽  
Bertrand Lefebvre
Keyword(s):  
Phylogenetic Analysis ◽  
Sister Taxon ◽  
Evolutionary Significance ◽  
Coelomic Cavity ◽  
Anatomical Features ◽  
New Findings ◽  
Solid Block ◽  
Cover Plates

Abstract Twelve specimens of Eumorphocystis Branson and Peck, 1940 provide the basis for new findings and a more informed assessment of whether this blastozoan (a group including eocrinoids, blastoids, diploporites, rhombiferans) constitutes the sister taxon to crinoids, as has been recently proposed. Both Eumorphocystis and earliest-known crinoid feeding appendages express longitudinal canals, a demonstrable trait exclusive to these taxa. However, the specimen series studied here shows that Eumorphocystis canals constrict proximally and travel within ambulacrals above the thecal cavity. This relationship is congruent with a documented blastozoan pattern but very unlike earliest crinoid topology. Earliest crinoid arm cavities lie fully beneath floor plates; these expand and merge directly with the main thecal coelomic cavity at thecal shoulders. Other associated anatomical features echo this contrasting comparison. Feeding appendages of Eumorphocystis lack two-tiered cover plates, podial basins/pores, and lateral arm plating, all features of earliest crinoid ‘true arms.’ Eumorphocystis feeding appendages are buttressed by solid block-like plates added during ontogeny at a generative zone below floor plates, a pattern with no known parallel among crinoids. Eumorphocystis feeding appendages express brachioles, erect extensions of floor plates, also unknown among crinoids. These several distinctions point to nonhomology of most feeding appendage anatomy, including longitudinal canals, removing Eumorphocystis and other blastozoans from exclusive relationship with crinoids. Eumorphocystis further differs from crinoids in that thecal plates express diplopores, respiratory structures not present among crinoids, but ubiquitous among certain groups of blastozoans. Phylogenetic analysis places Eumorphocystis as a crownward blastozoan, far removed from crinoids.

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