scholarly journals Bizarre tail weaponry in a transitional ankylosaur from subantarctic Chile

2021 ◽  
Author(s):  
Sergio Soto-Acuña ◽  
Alexander Vargas ◽  
Jonatan Kaluza ◽  
Marcelo Leppe ◽  
Joao Botelho ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Phylogenetic Analyses ◽  
Heavy Tail ◽  
Postcranial Skeleton ◽  
Distal Half

Abstract Armoured dinosaurs are well known for forms that evolved specialized tail weapons: paired tail spikes in stegosaurs, and heavy tail clubs in advanced ankylosaurs1. Armoured dinosaurs from southern Gondwana are rare and enigmatic, but likely include the earliest branches of Ankylosauria2-4. Here, we describe a mostly complete, semiarticulated skeleton of a small (about 2m) armoured dinosaur from the late Cretaceous of Magallanes in southernmost Chile, a region biogeographically related to West Antarctica5. Stegouros elengassen gen. et sp. nov. evolved a large tail weapon unlike any dinosaur: A flat, frond-like structure formed by 7 pairs of laterally projecting osteoderms encasing the distal half of the tail. Stegouros shows ankylosaurian cranial characters, but a largely primitive postcranial skeleton, with some stegosaur-like characters. Phylogenetic analyses placed Stegouros in Ankylosauria, and specifically related to Kunbarrasaurus from Australia6 and Antarctopelta from Antarctica7, forming a clade of Gondwanan ankylosaurs that split earliest from all other ankylosaurs. Large osteoderms and specialized tail vertebrae in Antarctopelta suggest it had a tail weapon similar to Stegouros. We propose a new clade, the Parankylosauria, to include the first ancestor of Stegouros but not Ankylosaurus, and all descendants of that ancestor.

scholarly journals A second peirosaurid crocodyliform from the Mid-Cretaceous Kem Kem Group of Morocco and the diversity of Gondwanan notosuchians outside South America

2021 ◽  
Vol 8 (10) ◽  
Author(s):  
Cecily S. C. Nicholl ◽  
Eloise S. E. Hunt ◽  
Driss Ouarhache ◽  
Philip D. Mannion
Keyword(s):  
South America ◽  
Late Cretaceous ◽  
North Africa ◽  
Lateral Surface ◽  
Middle Jurassic ◽  
Tooth Enamel ◽  
Phylogenetic Analyses ◽  
Late Eocene ◽  
South American ◽  
Early Late

Notosuchians are an extinct clade of terrestrial crocodyliforms with a particularly rich record in the late Early to Late Cretaceous (approx. 130–66 Ma) of Gondwana. Although much of this diversity comes from South America, Africa and Indo-Madagascar have also yielded numerous notosuchian remains. Three notosuchian species are currently recognized from the early Late Cretaceous (approx. 100 Ma) Kem Kem Group of Morocco, including the peirosaurid Hamadasuchus rebouli . Here, we describe two new specimens that demonstrate the presence of at least a fourth notosuchian species in this fauna. Antaeusuchus taouzensis n. gen. n. sp. is incorporated into one of the largest notosuchian-focused character-taxon matrices yet to be compiled, comprising 443 characters scored for 63 notosuchian species, with an increased sampling of African and peirosaurid species. Parsimony analyses run under equal and extended implied weighting consistently recover Antaeusuchus as a peirosaurid notosuchian, supported by the presence of two distinct waves on the dorsal dentary surface, a surangular which laterally overlaps the dentary above the mandibular fenestra, and a relatively broad mandibular symphysis. Within Peirosauridae, Antaeusuchus is recovered as the sister taxon of Hamadasuchus . However, it differs from Hamadasuchus with respect to several features, including the ornamentation of the lateral surface of the mandible, the angle of divergence of the mandibular rami, the texture of tooth enamel and the shape of the teeth, supporting their generic distinction. We present a critical reappraisal of the non-South American Gondwanan notosuchian record, which spans the Middle Jurassic–late Eocene. This review, as well as our phylogenetic analyses, indicate the existence of at least three approximately contemporaneous peirosaurid lineages within the Kem Kem Group, alongside other notosuchians, and support the peirosaurid affinities of the ‘trematochampsid’ Miadanasuchus oblita from the Maastrichtian of Madagascar. Furthermore, the Cretaceous record demonstrates the presence of multiple lineages of approximately contemporaneous notosuchians in several African and Madagascan faunas, and supports previous suggestions regarding an undocumented pre-Aptian radiation of Notosuchia. By contrast, the post-Cretaceous record is depauperate, comprising rare occurrences of sebecosuchians in north Africa prior to their extirpation.

scholarly journals A new southern Laramidian ankylosaurid, Akainacephalus johnsoni gen. et sp. nov., from the upper Campanian Kaiparowits Formation of southern Utah, USA

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5016 ◽  
Author(s):  
Jelle P. Wiersma ◽  
Randall B. Irmis
Keyword(s):  
Late Cretaceous ◽  
First Record ◽  
Multiple Time ◽  
New Taxon ◽  
Postcranial Skeleton ◽  
Surface Textures ◽  
Close Phylogenetic Relationship ◽  
Biogeographic Provinces ◽  
Dispersal Events ◽  
Upper Campanian

A partial ankylosaurid skeleton from the upper Campanian Kaiparowits Formation of southern Utah is recognized as a new taxon, Akainacephalus johnsoni, gen. et sp. nov. The new taxon documents the first record of an associated ankylosaurid skull and postcranial skeleton from the Kaiparowits Formation. Preserved material includes a complete skull, much of the vertebral column, including a complete tail club, a nearly complete synsacrum, several fore- and hind limb elements, and a suite of postcranial osteoderms, making Akainacephalus johnsoni the most complete ankylosaurid from the Late Cretaceous of southern Laramidia. Arrangement and morphology of cranial ornamentation in Akainacephalus johnsoni is strikingly similar to Nodocephalosaurus kirtlandensis and some Asian ankylosaurids (e.g., Saichania chulsanensis, Pinacosaurus grangeri, and Minotaurasaurus ramachandrani); the cranium is densely ornamented with symmetrically arranged and distinctly raised ossified caputegulae which are predominantly distributed across the dorsal and dorsolateral regions of the nasals, frontals, and orbitals. Cranial caputegulae display smooth surface textures with minor pitting and possess a distinct conical to pyramidal morphology which terminates in a sharp apex. Character analysis suggests a close phylogenetic relationship with N. kirtlandensis, M. ramachandrani, Tarchia teresae, and S. chulsanensis, rather than with Late Cretaceous northern Laramidian ankylosaurids (e.g., Euoplocephalus tutus, Anodontosaurus lambei, and Ankylosaurus magniventris). These new data are consistent with evidence for distinct northern and southern biogeographic provinces in Laramidia during the late Campanian. The addition of this new ankylosaurid taxon from southern Utah enhances our understanding of ankylosaurid diversity and evolutionary relationships. Potential implications for the geographical distribution of Late Cretaceous ankylosaurid dinosaurs throughout the Western Interior suggest multiple time-transgressive biogeographic dispersal events from Asia into Laramidia.

A review of pelvic shield morphology in ankylosaurs (Dinosauria: Ornithischia)

2011 ◽  
Vol 85 (2) ◽  
pp. 298-302 ◽  
Author(s):  
Victoria M. Arbour ◽  
Michael E. Burns ◽  
Philip J. Currie
Keyword(s):  
North America ◽  
Late Cretaceous ◽  
Late Jurassic ◽  
Phylogenetic Analyses ◽  
Diagnostic Value ◽  
Evolutionary Trends ◽  
Parsimony Analysis ◽  
Geographic Context ◽  
Binary Character ◽  
First Time

The pelvic shield of ankylosaurian dinosaurs refers to an area of osteoderms lacking differentiated transverse bands over the pelvic region and it is used as a diagnostic character for various ankylosaur groups. The pelvic shield character varies across ankylosaur taxa but is typically coded as a binary character or is excluded from phylogenetic analyses, which obscures evolutionary trends and relationships. This study investigates for the first time pelvic shield morphology in a stratigraphic and geographic context. This paper comprehensively reviews pelvic shield morphology with firsthand observations of specimens, and proposes three categories of pelvic shield morphology. Category 1 pelvic shields have un-fused but tightly interlocking osteoderms. Category 2 pelvic shields have fused osteoderms forming rosettes and are restricted to the Late Jurassic to mid Cretaceous of North America and Europe. Category 3 pelvic shields have fused polygonal osteoderms of similar size, and are found in the mid- to Late Cretaceous of North America. Although the pelvic shield is used to characterize the Polacanthidae, an interpretation supported by this review, the validity of such a clade is dependent upon a global parsimony analysis incorporating this character. Future analyses of the Ankylosauria should incorporate a more detailed treatment of the pelvic shield to determine its diagnostic value within the group.

scholarly journals Diversification patterns based on the largest morphological phylogenetic analysis of Pleurodira

2015 ◽  
Author(s):  
Gabriel S Ferreira ◽  
Juliana Sterli ◽  
Mario Bronzati Filho ◽  
Max C Langer
Keyword(s):  
Early Cretaceous ◽  
Late Cretaceous ◽  
Evolutionary History ◽  
Feeding Habits ◽  
Phylogenetic Analyses ◽  
Morphological Data ◽  
Phylogenetic Hypothesis ◽  
Consensus Tree ◽  
Strict Consensus Tree ◽  
History Of

Background. Most studies on pleurodiran turtles are about the behavior and/or feeding habits analyzes, description of new taxa or specimens (both extinct and extant), or phylogenetic analyzes of one of its subclades with extant taxa: Chelidae, Pelomedusidae or Podocnemididae. With the exception of some molecular phylogenies, there are no phylogenetic analyses of extant and extinct representatives of Pleurodira including all of its lineages. A broader understanding of the evolutionary history of Pleurodira requires a phylogenetic hypothesis based on more extensive taxonomic and character samplings.Methods. We constructed a taxon-character matrix including 227 morphological characters and 87 taxa from all the Pleurodira lineages, plus one stem Pan-Pleurodira, Notoemys laticentralis, and one stem-Testudinata, Proganochelys quenstedti, as outgroups. The resulting matrix was analyzed using parsimony, Tree Bisection and Reconnection (TBR) algorithms, with 5000 replicates, and a hold of 20. The obtained strict consensus tree was used as the basis of a diversification analysis using topology-based methods. A nestedgrowing tree approach was employed to create a corresponding tree for different intervals of the geological history of the group. Six distinct time bins were created for periods in which members of Pleurodira occur: Early Cretaceous, Late Cretaceous, Paleocene, Eocene, Miocene, and Recent. Results. All main pleurodiran clades were recovered in the strict consensus tree, but with some changes in their relationship compared to previous analyses, e.g. the inclusiveness of both Pelomedusoides and Bothremydidae. The diversification analysis shows that, after the establishment of the two major lineages (i.e. Chelidae and Pelomedusoides) in the Early Cretaceous, these subgroups diversified in distinct rates along their evolutionary history. Two main diversification shifts were identified: one at the early evolution of Podocnemoidea, during the Late Cretaceous, and another during the Miocene, deep nested in the Podocnemididae clade. Discussion. The resulting strict consensus tree is the largest exclusive phylogenetic hypothesis for Pleurodira, including both extant and extinct taxa. Based on morphological data, it allows more inclusive inferences on the general morphological and diversification patterns of the group. The diversification pulses analysis suggests variation on the rates of diversification on the different pleurodiran clades. The first shift detected is related to the great radiation of Bothremydidae and Podocnemoidae in the Late Cretaceous; the second shift, detected in the Miocene, is related to a diversification within the Stereogenyina, a Podocnemididae clade. Ongoing analysis will determine which factors could enforce those different diversification rates in the evolution of Pleurodira.

scholarly journals The evolutionary history of polycotylid plesiosaurians

2018 ◽  
Vol 5 (3) ◽  
pp. 172177 ◽  
Author(s):  
V. Fischer ◽  
R. B. J. Benson ◽  
P. S. Druckenmiller ◽  
H. F. Ketchum ◽  
N. Bardet
Keyword(s):  
Early Cretaceous ◽  
Late Cretaceous ◽  
Phylogenetic Relationships ◽  
Evolutionary History ◽  
Phylogenetic Analyses ◽  
Neck Length ◽  
Ecological Release ◽  
Holotype Specimen ◽  
Low Diversity ◽  
History Of

Polycotylidae is a clade of plesiosaurians that appeared during the Early Cretaceous and became speciose and abundant early in the Late Cretaceous. However, this radiation is poorly understood. Thililua longicollis from the Middle Turonian of Morocco is an enigmatic taxon possessing an atypically long neck and, as originally reported, a series of unusual cranial features that cause unstable phylogenetic relationships for polycotylids. We reinterpret the holotype specimen of Thililua longicollis and clarify its cranial anatomy. Thililua longicollis possesses an extensive, foramina-bearing jugal, a premaxilla–parietal contact and carinated teeth. Phylogenetic analyses of a new cladistic dataset based on first-hand observation of most polycotylids recover Thililua and Mauriciosaurus as successive lineages at the base of the earliest Late Cretaceous polycotyline radiation. A new dataset summarizing the Bauplan of polycotylids reveals that their radiation produced an early burst of disparity during the Cenomanian–Turonian interval, with marked plasticity in relative neck length, but this did not arise as an ecological release following the extinction of ichthyosaurs and pliosaurids. This disparity vanished during and after the Turonian, which is consistent with a model of ‘early experimentation/late constraint’. Two polycotylid clades, Occultonectia clade nov. and Polycotylinae, survived up to the Maastrichtian, but with low diversity.

A new, remarkably preserved, enantiornithine bird from the Upper Cretaceous Qiupa Formation of Henan (central China) and convergent evolution between enantiornithines and modern birds

2021 ◽  
pp. 1-8
Author(s):  
Li Xu ◽  
Eric Buffetaut ◽  
Jingmai O’Connor ◽  
Xingliao Zhang ◽  
Songhai Jia ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Late Cretaceous ◽  
Convergent Evolution ◽  
Upper Cretaceous ◽  
Henan Province ◽  
Central China ◽  
Postcranial Skeleton ◽  
Cretaceous Period ◽  
New Evidence ◽  
Partial Skeleton

Abstract A new enantiornithine bird is described on the basis of a well preserved partial skeleton from the Upper Cretaceous Qiupa Formation of Henan Province (central China). It provides new evidence about the osteology of Late Cretaceous enantiornithines, which are mainly known from isolated bones; in contrast, Early Cretaceous forms are often represented by complete skeletons. While the postcranial skeleton shows the usual distinctive characters of enantiornithines, the skull displays several features, including confluence of the antorbital fenestra and the orbit and loss of the postorbital, evolved convergently with modern birds. Although some enantiornithines retained primitive cranial morphologies into the latest Cretaceous Period, at least one lineage evolved cranial modifications that parallel those in modern birds.

Osteology and systematics of Uberabatitan ribeiroi (Dinosauria; Sauropoda): a Late Cretaceous titanosaur from Minas Gerais, Brazil

Zootaxa ◽  
2019 ◽  
Vol 4577 (3) ◽  
pp. 401 ◽  
Author(s):  
JULIAN C. G. JUNIOR SILVA ◽  
THIAGO S. MARINHO ◽  
AGUSTÍN G. MARTINELLI ◽  
MAX C. LANGER
Keyword(s):  
Late Cretaceous ◽  
Phylogenetic Analyses ◽  
Minas Gerais ◽  
Type Locality ◽  
Southeastern Brazil ◽  
Type Series ◽  
Total Body ◽  
Linear Regressions

Uberabatitan ribeiroi is a Late Cretaceous titanosaur (Dinosauria, Sauropoda) from southeastern Brazil. Here we provide a detailed revision of all its available specimens, including new elements from the type-locality. One new autopomorphy is added to diagnosis of the taxon: astragalus with a well-developed anteroposterior crest that mediodistally delimits the tibial articulation. Linear regressions were conducted in an attempt to circumscribe specimens within the type-series, revealing that it is composed of several individuals, with inferred total body lengths varying from 7 to 26 meters. Phylogenetic analyses including U. ribeiroi show that the Brazilian taxon corresponds to a non-saltasaurid lithostrotian titanosaur. 

scholarly journals Reassessment of a juvenile Daspletosaurus from the Late Cretaceous of Alberta, Canada with implications for the identification of immature tyrannosaurids

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jared T. Voris ◽  
Darla K. Zelenitsky ◽  
François Therrien ◽  
Philip J. Currie
Keyword(s):  
Late Cretaceous ◽  
Phylogenetic Analyses ◽  
Ontogenetic Stage ◽  
Ontogenetic Changes ◽  
Diagnostic Features ◽  
Taxonomic Affinity ◽  
Small Juvenile ◽  
Juvenile Individual ◽  
Dinosaur Park Formation ◽  
Upper Campanian

AbstractDaspletosaurus is a large tyrannosaurine found in upper Campanian deposits of Alberta and Montana. Although several large subadult and adult individuals of this taxon are known, only one juvenile individual, TMP 1994.143.1, has been identified. This specimen has played a key role in the idea that juvenile tyrannosaurid individuals are difficult to differentiate among species. Here the taxonomic affinity of TMP 1994.143.1 is reassessed in light of a juvenile tyrannosaurine postorbital recently discovered in the Dinosaur Park Formation of Alberta. Anatomical comparisons and phylogenetic analyses reveal that TMP 1994.143.1 is referable to the albertosaurine Gorgosaurus libratus, whereas the new postorbital belongs to a small juvenile Daspletosaurus. This taxonomic reassignment of TMP 1994.143.1 results in the juvenile ontogenetic stage of Daspletosaurus being known only from two isolated cranial elements. The new postorbital provides insights into early Daspletosaurus ontogeny, revealing that the cornual process developed earlier or faster than in other tyrannosaurids. Although some ontogenetic changes in the postorbital are found to be unique to Daspletosaurus, overall changes are most consistent with those of other large tyrannosaurines. Our results also show that diagnostic features develop early in ontogeny, such that juveniles of different tyrannosaurid species are easier to differentiate than previously thought.

Sign in / Sign up

Export Citation Format

Share Document