Probable basal allosauroid from the early Middle Jurassic Cañadón Asfalto Formation of Argentina highlights phylogenetic uncertainty in tetanuran theropod dinosaurs

AbstractTetanurae, the most successful clade of theropod dinosaurs, including modern birds, split into three major clades early in their evolutionary history: Megalosauroidea, Coelurosauria, and Allosauroidea. The oldest tetanurans occur in the earliest Middle Jurassic, but the early fossil record of the clade is still poor. Here we report one of the oldest known and most complete pre-Late Jurassic tetanuran, the probable allosauroid Asfaltovenator vialidadi gen. et sp. nov., which has an unusual character combination, uniting features currently considered to be apomorphic of different tetanuran lineages. A phylogenetic analysis resulted in a monophyletic Carnosauria (Allosauroidea + Megalosauroidea), and the inclusion of the new taxon significantly changes topology within carnosaurs. The analysis shows concentrated homoplasy in proximal nodes at the base of Tetanurae, and a temporal peak at the Pliensbachian-Toarcian extinction event, recently identified as a potential driver of tetanuran radiation. These results highlight the complex morphological evolution in the early radiation of tetanuran theropods, in which convergences and parallelisms were extremely common. This pattern seems to be a common feature in rapid radiation events of major clades of vertebrates and might explain the common difficulties to unravel phylogenetic relationships of important lineages at the base of major clades.

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A new stem turtle from the Middle Jurassic of Scotland: new insights into the evolution and palaeoecology of basal turtles

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2008.1429 ◽

2008 ◽

Vol 276 (1658) ◽

pp. 879-886 ◽

Cited By ~ 51

Author(s):

Jérémy Anquetin ◽

Paul M Barrett ◽

Marc E.H Jones ◽

Scott Moore-Fay ◽

Susan E Evans

Keyword(s):

Middle Jurassic ◽

Late Jurassic ◽

Evolutionary History ◽

Sister Group ◽

Late Triassic ◽

Sister Group Relationship ◽

New Taxon ◽

Crown Group ◽

History Of ◽

Isle Of Skye

The discovery of a new stem turtle from the Middle Jurassic (Bathonian) deposits of the Isle of Skye, Scotland, sheds new light on the early evolutionary history of Testudinata. Eileanchelys waldmani gen. et sp. nov. is known from cranial and postcranial material of several individuals and represents the most complete Middle Jurassic turtle described to date, bridging the morphological gap between basal turtles from the Late Triassic–Early Jurassic and crown-group turtles that diversify during the Late Jurassic. A phylogenetic analysis places the new taxon within the stem group of Testudines (crown-group turtles) and suggests a sister-group relationship between E. waldmani and Heckerochelys romani from the Middle Jurassic of Russia. Moreover, E. waldmani also demonstrates that stem turtles were ecologically diverse, as it may represent the earliest known aquatic turtle.

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A new possible megalosauroid theropod from the Middle Jurassic Xintiangou Formation of Chongqing, People’s Republic of China and its implication for early tetanuran evolution

Scientific Reports ◽

10.1038/s41598-019-56959-x ◽

2020 ◽

Vol 10 (1) ◽

Cited By ~ 2

Author(s):

Hui Dai ◽

Roger Benson ◽

Xufeng Hu ◽

Qingyu Ma ◽

Chao Tan ◽

...

Keyword(s):

Middle Jurassic ◽

Evolutionary History ◽

Morphological Evolution ◽

Cervical Vertebrae ◽

Special Group ◽

Republic Of China ◽

Theropod Dinosaurs ◽

Anterior Dorsal ◽

Articular Surfaces ◽

History Of

AbstractTetanurae is a special group of theropod dinosaurs that originated by the late Early Jurassic. It includes several early-diverging groups of generally large-bodied predators (megalosauroids, allosauroids, tyrannosauroid coelurosaurs) as well as morphologically disparate small-bodied coelurosaurs, including birds. Aspects of the evolutionary history of tetanurans remain contested, including the topology of their deep phylogenetic divergences (among Megalosauroidea, Allosauroidea and Coelurosauria). We report a new theropod, Yunyangosaurus puanensis gen. et sp. nov., based on a fragmentary specimen recovered from the Middle Jurassic Xintiangou Formation of Chongqing, southwestern China. It shares several features uniquely with some megalosauroids (the clade of megalosaurids + spinosaurids + piatnitzkysaurids), such as prominent rims around the anterior articular surfaces of cervical centra and bifurcated anterior dorsal neural spines (present in piatnitzkysaurids). Nevertheless, it also shows several features that are rare or absent among megalosauroids and more crownward tetanurans, including prominent spinopostyzgopophyseal laminae (also present in non-tetanurans and metriacanthosaurid allosauroids), flat anterior articular surfaces of the cervical centra (also present in piatnitzkysaurids and some earlier-diverging tetanurans), and the presence of a posterior pneumatic foramen or fossa (absent in most tetanurans, but sporadically present in some cervical vertebrae of piatnitzkysaurids). Yunyangosaurus therefore presents a combination of derived and apparently primitive character states that are not seen in other theropods. This suggests that patterns of morphological evolution associated with deep tetanuran divergences were more complex than currently recognized, with implications for understanding the character evolution in theropods.

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A new stem turtle from the Middle Jurassic of Scotland: new insights into the evolution and palaeoecology of basal turtles

10.31233/osf.io/qxz7d ◽

2017 ◽

Author(s):

Jérémy Anquetin ◽

Paul M. Barrett ◽

Marc E. H. Jones ◽

Scott Moore-Fay ◽

Susan E. Evans

Keyword(s):

Middle Jurassic ◽

Late Jurassic ◽

Evolutionary History ◽

Sister Group ◽

Late Triassic ◽

Sister Group Relationship ◽

New Taxon ◽

Crown Group ◽

History Of ◽

Isle Of Skye

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Sphenofontis velserae gen. et sp. nov., a new rhynchocephalian from the Late Jurassic of Brunn (Solnhofen Archipelago, southern Germany)

PeerJ ◽

10.7717/peerj.11363 ◽

2021 ◽

Vol 9 ◽

pp. e11363

Author(s):

Andrea Villa ◽

Roel Montie ◽

Martin Röper ◽

Monika Rothgaenger ◽

Oliver W.M. Rauhut

Keyword(s):

Middle Jurassic ◽

Late Jurassic ◽

Wide Distribution ◽

New Taxon ◽

Skeletal Morphology ◽

Southern Germany ◽

Single Well ◽

History Of

The Solnhofen Archipelago is well known for its fossil vertebrates of Late Jurassic age, among which figure numerous rhynchocephalian specimens, representing at least six and up to nine genera. A new taxon, named Sphenofontis velserae gen. et sp. nov., increases rhynchocephalian diversity in the Solnhofen Archipelago and is herein described based on a single, well-preserved specimen originating from the Late Kimmeridgian of the Brunn quarry, near Regensburg. The exquisite preservation of the holotype allowed a detailed description of the animal, revealing a skeletal morphology that includes both plesiomorphic and derived features within rhynchocephalians. Sphenofontis is herein referred to Neosphenodontia and tentatively to sphenodontine sphenodontids. It notably differs from all other rhynchocephalians known from the Jurassic of Europe, showing instead closer resemblance with the Middle Jurassic Cynosphenodon from Mexico and especially the extant Sphenodon. This is evidence for a wide distribution of taxa related to the extant tuatara early in the Mesozoic, and also for the presence of less-specialized rhynchocephalians coexisting with more derived forms during the earliest time in the history of the Solnhofen Archipelago.

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The first definitive Middle Jurassic atoposaurid (Crocodylomorpha, Neosuchia), and a discussion on the genus Theriosuchus

10.31233/osf.io/fpbh5 ◽

2017 ◽

Author(s):

Mark T. Young ◽

Jonathan Tennant ◽

Stephen L. Brusatte ◽

Thomas J. Challands ◽

Nicholas C. Fraser ◽

...

Keyword(s):

Middle Jurassic ◽

Late Jurassic ◽

Evolutionary History ◽

Valid Species ◽

Diagnostic Features ◽

Comprehensive Review ◽

History Of ◽

Isle Of Skye ◽

Broad Scale

Atoposaurids were a clade of semiaquatic crocodyliforms known from the Late Jurassic to the latest Cretaceous. Tentative remains from Europe, Morocco, and Madagascar may extend their range into the Middle Jurassic. Here we report the first unambiguous Middle Jurassic (late Bajocian–Bathonian) atoposaurid: an anterior dentary from the Isle of Skye, Scotland, UK. A comprehensive review of atoposaurid specimens demonstrates that this dentary can be referred to Theriosuchus based on several derived characters, and differs from the five previously recognized species within this genus. Despite several diagnostic features, we conservatively refer it to Theriosuchus sp., pending the discovery of more complete material. As the oldest known definitively diagnostic atoposaurid, this discovery indicates that the oldest members of this group were small-bodied, had heterodont dentition, and were most likely widespread components of European faunas. Our review of mandibular and dental features in atoposaurids not only allows us to present a revised diagnosis of Theriosuchus, but also reveals a great amount of variability within this genus, and indicates that there are currently five valid species that can be differentiated by unique combinations of dental characteristics. This variability can be included in future broad-scale cladistics analyses of atoposaurids and closely related crocodyliforms, which promise to help untangle the complicated taxonomy and evolutionary history of Atoposauridae.

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

The Science of Nature ◽

10.1007/s00114-021-01719-z ◽

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.

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A new Lower Cretaceous ichthyosaur from Russia reveals skull shape conservatism within Ophthalmosaurinae

Geological Magazine ◽

10.1017/s0016756812000994 ◽

2013 ◽

Vol 151 (1) ◽

pp. 60-70 ◽

Cited By ~ 21

Author(s):

VALENTIN FISCHER ◽

MAXIM S. ARKHANGELSKY ◽

GLEB N. USPENSKY ◽

ILYA M. STENSHIN ◽

PASCAL GODEFROIT

Keyword(s):

Early Cretaceous ◽

Lower Cretaceous ◽

Middle Jurassic ◽

Ecological Niche ◽

Late Jurassic ◽

Evolutionary History ◽

Skull Shape ◽

Marine Reptiles ◽

Lower Aptian

AbstractOphthalmosaurinae is a recently recognized clade of derived ichthyosaurs (marine reptiles) ranging from the Bajocian (Middle Jurassic) to the late Albian (late Early Cretaceous). Whereas the Middle–Late Jurassic ophthalmosaurine Ophthalmosaurus is often regarded as a hyperspecialized deep diver, very little is known about the anatomy, evolutionary history and ecology of Cretaceous ophthalmosaurines because of the scarcity of the fossils and the lack of well-preserved skull material. Here, we describe the skull of a new basal ophthalmosaurine ichthyosaur, Leninia stellans gen. et sp. nov., from the lower Aptian of western Russia, and compare the ocular characteristics of ophthalmosaurids. Leninia is recovered as a basal ophthalmosaurine; it possesses unique traits such as a star-shaped frontal–parietal suture as well as features previously thought to be unique to Ophthalmosaurus such as a supratemporal–stapes contact. A large sclerotic aperture – significantly larger than in platypterygiine ophthalmosaurids and similar to that of the largest-eyed modern animals (giant and colossal squids) – and reduced dentition appear widespread within ophthalmosaurines. This conservatism suggests ophthalmosaurine ophthalmosaurids occupied similar ecological niche(s) throughout their long evolutionary history.

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The first metriorhynchoid crocodyliform from the Aalenian (Middle Jurassic) of Germany, with implications for the evolution of Metriorhynchoidea

Zoological Journal of the Linnean Society ◽

10.1093/zoolinnean/zlz072 ◽

2019 ◽

Author(s):

Manuela Aiglstorfer ◽

Philipe Havlik ◽

Yanina Herrera

Keyword(s):

Middle Jurassic ◽

Evolutionary History ◽

Marine Ecosystems ◽

Morphological Features ◽

New Taxon ◽

Unique Combination ◽

Southern Germany ◽

Puzzle Piece ◽

Character Distribution ◽

History Of

Abstract Thalattosuchia, a clade of Mesozoic aquatic crocodyliforms, were the only archosaurs that ever became fully adapted to marine ecosystems. They are represented by two clades, the semiaquatic teleosauroids and the metriorhynchoids, which include fully pelagic forms. So far, little is known on the early evolutionary history of Metriorhynchoidea and data are sparse, especially from the early Middle Jurassic. Opisuchus meieri gen. et sp. nov. a metriorhynchoid crocodyliform from the early Aalenian (early Middle Jurassic) of southern Germany, is described here. It is one of the most complete specimens of a non-metriorhynchid metriorhynchoid, and the best-preserved thalattosuchian described from the Aalenian. The new taxon is represented by a nearly complete skull, which has a unique combination of characters distinguishing it from other species of Metriorhynchoidea. It displays a mosaic of plesiomorphic and apomorphic morphological features that sheds new light on early metriorhynchoid evolution. This taxon is an important puzzle piece, which will help to better track the mosaic character distribution in Thalattosuchia.

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Notes on the cheek region of the Late Jurassic theropod dinosaur Allosaurus

PeerJ ◽

10.7717/peerj.8493 ◽

2020 ◽

Vol 8 ◽

pp. e8493

Author(s):

Serjoscha W. Evers ◽

Christian Foth ◽

Oliver W.M. Rauhut

Keyword(s):

North America ◽

19Th Century ◽

Late Jurassic ◽

Morrison Formation ◽

Late 19Th Century ◽

Theropod Dinosaur ◽

European Species ◽

Theropod Dinosaurs ◽

The Common ◽

Iconic Status

Allosaurus, from the Late Jurassic of North America and Europe, is a model taxon for Jurassic basal tetanuran theropod dinosaurs. It has achieved an almost iconic status due to its early discovery in the late, 19th century, and due to the abundance of material from the Morrison Formation of the western U.S.A., making Allosaurus one of the best-known theropod taxa. Despite this, various aspects of the cranial anatomy of Allosaurus are surprisingly poorly understood. Here, we discuss the osteology of the cheek region, comprised by the jugal, maxilla, and lacrimal. This region of the skull is of importance for Allosaurus taxonomy and phylogeny, particularly because Allosaurus has traditionally been reconstructed with an unusual cheek configuration, and because the European species Allosaurus europaeus has been said to be different from North American material in the configuration of these bones. Based on re-examination of articulated and disarticulated material from a number of repositories, we show that the jugal participates in the antorbital fenestra, contradicting the common interpretation. The jugal laterally overlies the lacrimal, and forms an extended antorbital fossa with this bone. Furthermore, we document previously unrecorded pneumatic features of the jugal of Allosaurus.

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A Middle Jurassic abelisaurid from Patagonia and the early diversification of theropod dinosaurs

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2012.0660 ◽

2012 ◽

Vol 279 (1741) ◽

pp. 3170-3175 ◽

Cited By ~ 71

Author(s):

Diego Pol ◽

Oliver W. M. Rauhut

Keyword(s):

South America ◽

Northern Hemisphere ◽

Early Cretaceous ◽

Middle Jurassic ◽

Evolutionary History ◽

Regional Geography ◽

Distinctive Features ◽

Theropod Dinosaurs ◽

Early Diversification ◽

History Of

Abelisaurids are a clade of large, bizarre predatory dinosaurs, most notable for their high, short skulls and extremely reduced forelimbs. They were common in Gondwana during the Cretaceous, but exceedingly rare in the Northern Hemisphere. The oldest definitive abelisaurids so far come from the late Early Cretaceous of South America and Africa, and the early evolutionary history of the clade is still poorly known. Here, we report a new abelisaurid from the Middle Jurassic of Patagonia, Eoabelisaurus mefi gen. et sp. nov., which predates the so far oldest known secure member of this lineage by more than 40 Myr. The almost complete skeleton reveals the earliest evolutionary stages of the distinctive features of abelisaurids, such as the modification of the forelimb, which started with a reduction of the distal elements. The find underlines the explosive radiation of theropod dinosaurs in the Middle Jurassic and indicates an unexpected diversity of ceratosaurs at that time. The apparent endemism of abelisauroids to southern Gondwana during Pangean times might be due to the presence of a large, central Gondwanan desert. This indicates that, apart from continent-scale geography, aspects such as regional geography and climate are important to reconstruct the biogeographical history of Mesozoic vertebrates.

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