PALEONTOLOGY IN MAY, 2025

ABSTRACT

In the Late Cretaceous, continental fragmentation and high sea levels created a series of island continents, leading to the evolution of endemic dinosaur faunas on these isolated land masses. Laramidia saw the emergence of faunas dominated by ornithischian herbivores and tyrannosaurid predators whereas Gondwanan continents were dominated by titanosaurian sauropods and abelisaurid predators. However, the end of the Cretaceous also saw exchange between northern and southern assemblages, with titanosaurs immigrating into Laurasia, and hadrosaurids invading Gondwana. Recently, the lambeosaurine hadrosaurid Ajnabia odysseus was reported from the late Maastrichtian Phosphates of Morocco, providing evidence of dispersal by duckbill dinosaurs into northwest Africa. A second lambeosaurine, Minqaria bata, has since been documented from the same strata in Morocco. Both belong to the lambeosaurine tribe Arenysaurini. Here we report a third species of arenysaurin, Taleta taleta gen. et sp. nov., also from the uppermost Maastrichtian Phosphates of Morocco. Taleta, known from two associated maxillae, differs from Ajnabia and Minqaria in the dorsally positioned ectopterygoid ridge, straight toothrow, large, obliquely oriented maxillary tooth crowns, and prominent primary ridge of the maxillary teeth. The striking variation in jaw and tooth morphology seen in African arenysaurins suggests a dispersal-driven adaptive radiation, with lambeosaurines rapidly diversifying to occupy new niches following dispersal from Europe into North Africa. The African radiation coincided with lambeosaurine decline in North America, emphasizing the highly regional nature of dinosaur evolution.

LINK(S)

https://www.sciencedirect.com/science/article/abs/pii/S1342937X2500156X?via%3Dihub

ABSTRACT

Allosaurus fragilis was first described in the Upper Jurassic of Portugal in 1999 based on a set of postcranial remains collected at the Andrés fossil site in Pombal. The description of a second species, Allosaurus europaeus, based on a posterior part of an articulated skull and a sequence of cervical vertebrae (ML 415) collected at Praia de Vale Frades in Lourinhã, has been controversial, and its validity has been challenged. A detailed description of a new sample of cranial fossil material collected at Andrés that can be confidentially attributed to Allosaurus is presented. In addition, a comprehensive phylogenetic assessment of the Morrison Formation fossil record of Allosaurus is also performed. This analysis indicates that only two valid Allosaurus species were present in the Late Jurassic ecosystems of North America: Allosaurus fragilis and Allosaurus jimmadseni. An emended diagnosis for Allosaurus fragilis is here proposed. The Portuguese specimens MNHN/UL.AND.#, ML 415, and MG 27804 are here interpreted as belonging to Allosaurus fragilis. This interpretation has important implications to better understand the evolutionary history of the theropod fauna of the Lusitanian Basin, supporting the existence of close biogeographic relationships between the landmasses on both sides of the proto-North Atlantic Ocean during the Kimmeridgian–Tithonian.

LINK(S)

https://academic.oup.com/zoolinnean/article-abstract/204/1/zlaf029/8151024?redirectedFrom=fulltext

ABSTRACT

The recovery of a partial skull comprised mostly of the braincase of the extinct sloth, Megalonyx jeffersonii from Hays, Ellis County, Kansas provides a better understanding of the distribution of this species in Kansas and on the Great Plains in general. While the age of the skull could not be determined by radiocarbon dating, its presence in the Peoria loess narrows the age of the specimen to the late Wisconsian, most likely the Last Glacial Maximum between 21,000- and 12,000-years BP. The sloth specimen is among the few vertebrate remains directly recovered from the Peoria loess.

LINK(S)

https://bioone.org/journals/transactions-of-the-kansas-academy-of-science/volume-128/issue-1-2/062.128.0101/A-New-Record-of-the-Extinct-Ground-Sloth-Megalonyx-jeffersonii/10.1660/062.128.0101.short

ABSTRACT

The first elasmosaurid skeleton from the Haslam Formation (Upper Santonian) of the Nanaimo Group (Late Cretaceous) on Vancouver Island was first described in 2002, and has recently been declared the Provincial Fossil of British Columbia. Since then, additional fossils have been recovered: an isolated right humerus and a well-preserved, osteologically immature skeleton comprising thorax, girdles and limbs. The Haslam material can now support further taxonomic assessment, and we erect the species Traskasaura sandrae based on it. Traskasaura possesses a strange mosaic of features. The mandible is plesiomorphic as seen in Libonectes: relatively narrow with large teeth and a broad symphysis. The skull therefore lacks any of the radical oral cavity adaptations seen in basal aristonectines. The neck of the Haslam animal is also plesiomorphic, with at least 36 preserved cervical vertebrae having vertebral length indices (VLIs) over 100 (the total number of cervicals is not known). The centra lack the anteroposterior compression and midline longitudinal constriction characteristic of derived aristonectines, yet the cervical ribs trend forward – a condition known only in derived aristonectines and Vegasaurus. The autapomorphic coracoid of Traskasaura differs greatly from any known elasmosaurid; the cardiform recess is reduced and posteriorly located, with some similarities to that of Aristonectes quiriquinensis. The humerus is autapomorphic, possessing a relatively straight shaft, pronounced ventral camber and an articular facet on the leading edge that makes a 90° angle with the radial facet. Taken together, these features document a new genus, with a plesiomorphic axial skeleton, but with several convergent appendicular adaptations with derived aristonectines. A revised phylogenetic analysis of Elasmosauridae recovered the new taxon in a basal position. Therefore, the postcranial adaptations shared with derived aristonectines appear to be convergent.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/14772019.2025.2489938

ABSTRACT

This study describes new ankylosaurid dinosaur fossil material discovered in the Haoling Formation of the Lower Cretaceous strata in the Ruyang Basin, Henan Province. Based on this material, a new species within the genus Zhongyuansaurus is established: Zhongyuansaurus junchangi sp. nov. This species is characterized by a unique au tapomorphy: at least five caudal armor plates arranged in a shingle-like pattern with a distinctive swallowtail shape. Additionally, it exhibits relatively slender mandibular bones compared to the more robust mandibles of advanced An-kylosaurinae. The anterior tip of the coronoid process extends only to the last two alveoli, differing from Shamosaurus. The distal caudal vertebrae are adorned with small osteoderms, and the humerus has a midshaft circumfer ence-to-total-length ratio of 0.46, distinguishing it from Zhongyuansaurus luoyangensis. The discovery of Zhong yuansaurus junchangi provides new insights into the evolution of ankylosaurs in the Lower Cretaceous strata of Ruyang and enhances the species diversity of the Ruyang dinosaur fauna.

LINK(S)

http://gswxb.cnjournals.cn/gswxb/article/abstract/20250104

http://gswxb.cnjournals.cn/gswxb/article/pdf/20250104

ABSTRACT

In 2015, a partial skeleton of the Late Triassic dinosaur Plateosaurus trossingensis was excavated from Frick, Switzerland, and subsequently mounted at the Natural History Museum of Vienna in 2021. This specimen includes an almost complete series of tail vertebrae, with a well-preserved, articulated whip-like distal end. The preserved tail structure provides valuable insights into the morphological implications of tail function and its potential role in the behaviour of Plateosaurus. Using the caudal vertebrae, we reconstructed and analysed the potential tail-lashing capabilities of Plateosaurus, comparing its biomechanics with those of other fossil and extant long-tailed reptilian taxa, including the extinct sauropod Diplodocus, the extant Asian water monitor (Varanus salvator), and the green iguana (Iguana iguana). Our results indicate that the tail of P. trossingensis was highly flexible, with an estimated kinetic energy output ranging between 0.537 and 1.616 kJ during rapid strikes, comparable to the defensive tail use observed in modern reptiles. These findings suggest that tail-whipping may have played a role in predator deterrence and intraspecific interactions in Plateosaurus.

LINK(S)

https://royalsocietypublishing.org/doi/10.1098/rsos.250325

https://royalsocietypublishing.org/doi/pdf/10.1098/rsos.250325

ABSTRACT

Imperobator antarcticus is a paravian dinosaur based on fossil remains of the left and right hind limbs from the Cape Lamb Member (lower Maastrichtian) of the Snow Hill Island Formation, Antarctica. The only known specimen includes the tibia, astragalus, calcaneum, fragments of metatarsals, and non-ungual and ungual phalanges. It was originally described as a paravian with uncertain affinities, as it exhibits a mosaic of characters, such as the fusion of the calcaneum and fibula, a non-ginglymoid metatarsal II, and the absence of hyper-specialization of pedal digit II, forming the raptorial digit typical of deinonychosaurian dinosaurs. Previous authors indicate that it may be related to dromaeosaurids and unenlagiids. Imperobator was included in the TWiG data matrix to recognize its phylogenetic affinities. This comprehensive dataset was further improved by re-scoring and reanalysis of most unenlagiids. Additionally, 11 new taxa (including Imperobator and South American paravians like Pamparaptor and Overoraptor) were added, resulting in a data matrix of 175 taxa and 850 characters. The STAR 1 methodology proposed by previous authors was followed to construct phylogenetic trees. As a result, Imperobator antarcticus is nested within the Unenlagiidae clade. Despite its incomplete nature, Imperobator exhibits a subarctometatarsalian pes, a condition regarded as a Unenlagiidae synapomorphy by the present analysis. In dromaeosaurids, such as eudromaeosaurians and halszkaraptorines, metatarsal III is not lateromedially compressed, shows subparallel medial and lateral margins, and is not constricted between metatarsals II and IV. Imperobator antarcticus constitutes an important addition to the list of Late Cretaceous dinosaurs shared by South America and Antarctica.

LINK(S)

https://ameghiniana.org.ar/index.php/ameghiniana/article/view/3604

ABSTRACT

Much diversity in arthropod form is the result of variation in the number and differentiation of segments (tagmosis). Fossil evidence to date has suggested that the earliest-diverging arthropods, the radiodonts, exhibited comparatively limited variability in tagmosis. We present a new radiodont, Mosura fentoni n. gen. and n. sp., from the Cambrian (Wuliuan) Burgess Shale that departs from this pattern. Mosura exhibits up to 26 trunk segments, the highest number reported for any radiodont, despite being among the smallest known. The head is short, with a small, rounded preocular sclerite, three prominent eyes and appendages with curving endites tipped with paired spines, altogether suggesting a nektonic, macrophagous predatory ecology. The trunk is divided into a neck, mesotrunk with large swimming flaps and multisegmented posterotrunk with tightly spaced bands of gill lamellae and reduced flaps. Detailed preservation of expansive circulatory lacunae, closely associated with the gills, clarifies the nature of similar structures in other Cambrian arthropod fossils, including Opabinia. The morphology of the posterotrunk suggests specialization for respiration, unique among radiodonts, but broadly convergent with the xiphosuran opisthosoma, isopod pleon and hexapod abdomen. This reinforces the hypothesis that multiple arthropod lineages underwent parallel diversification in tagmosis, in tandem with their initial Cambrian radiation.

LINK(S)

https://royalsocietypublishing.org/doi/full/10.1098/rsos.242122

https://royalsocietypublishing.org/doi/pdf/10.1098/rsos.242122

ABSTRACT

Cratoavis cearensis, described from a single specimen unearthed from the Crato Formation of the Araripe Basin in Brazil, represents one of the earliest known fossil avians from South America (ca. 117 My). We report on the presence of disarticulated fish elements associated with the skeleton and interpret them as contained within the digestive tract of this enantiornithine bird. These bony elements are similar to ribs of Dastilbe crandalli, a fish belonging to Gonorynchiforms. Dastilbe crandalli is abundant in the same Crato deposits that have yielded Cratoavis cearensis. The identified bony elements provide direct evidence of a piscivorous diet for this Brazilian enantiornithine, thus contributing to the meager evidence available for understanding the trophic specializations of this major clade of Mesozoic birds.

LINK(S)

https://www.sciencedirect.com/science/article/abs/pii/S0195667125000849 

ABSTRACT

In 1855, Ferdinand Hayden collected a single tooth from the Judith River badlands of central Montana. Joseph Leidy named this specimen the following year as Troodon formosus. We describe troodontid material from the coeval Two Medicine Formation of Montana that compares closely to the recently resurrected and previously synonymized Stenonychosaurus inequalis from the lower Dinosaur Park Formation of Alberta. We uphold that synonymy but recognize T. formosus as the senior synonym. Troodon formosus is distinguished from other troodontids by a maxilla with an anteriorly more broadly rounded maxillary fenestra, low-angled nasal process with stepped anterior portion, large palatal shelf, and 23 teeth; more pronounced basioccipital tubera; L-shaped to triangular frontal; and relatively shorter metatarsal III with convex to flat anterior face at maximum breadth. Phylogenetic analysis places T. formosus within the Troodontinae, a clade with poor within-group resolution. The T. formosus holotype was diagnostic at time of description. Despite numerous complications over the taxon’s long history, the original name of 1856 has come to encompass a robust and specific species concept despite originally fragmentary material. Troodon formosus best satisfies the International Code of Zoological Nomenclature’s tenants of priority and stability. Recent proposals to re-establish Stenonychosaurus inequalis as the proper name encounter an equally problematic and undiagnostic type specimen. Instead of either of these types, we propose that material from the Two Medicine Formation (Museum of the Rockies, MOR 553) would best serve as a neotype for Troodon formosus.

LINK(S)

http://cambridge.org/core/journals/journal-of-paleontology/article/troodontid-specimens-from-the-cretaceous-two-medicine-formation-of-montana-usa-and-the-validity-of-troodon-formosus/3E58F1FDA3FE53DE569E0D0B20E79F22

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/3E58F1FDA3FE53DE569E0D0B20E79F22/S0022336024000672a.pdf/div-class-title-troodontid-specimens-from-the-cretaceous-two-medicine-formation-of-montana-usa-and-the-validity-of-span-class-italic-troodon-formosus-span-div.pdf

ABSTRACT

Some of the oldest known dinosaurs and the first faunas numerically dominated by them are documented in the Upper Triassic–Lower Jurassic-aged Gondwana formations exposed in the Pranhita-Godavari Valley of south-central and east-central India. The Upper Maleri Formation of the Pranhita-Godavari Basin preserves an early-middle Norian dinosaur assemblage numerically dominated by sauropodomorph dinosaurs, including at least two nominal species. However, the preliminary report of a herrerasaurian dinosaur specimen indicates that this assemblage of south-central Gondwana was more taxonomically diverse. Here, we describe and compare in detail the anatomy and assess the taxonomy and phylogenetic relationships of the Upper Maleri herrerasaurian specimen. A unique combination of character states present in this specimen allows the erection of the new genus and species Maleriraptor kuttyi. Updated quantitative phylogenetic analyses focused on early dinosauriforms recovered Maleriraptor kuttyi as a member of Herrerasauria outside of the South American clade Herrerasauridae. Maleriraptor kuttyi fills a temporal gap between the Carnian South American herrerasaurids and the younger middle Norian–Rhaetian herrerasaurs of North America. Maleriraptor kuttyi shows the first evidence that herrerasaurs survived also in Gondwana the early Norian tetrapod turnover that resulted in the global extinction of the rhynchosaurs.

LINK(S)

https://royalsocietypublishing.org/doi/10.1098/rsos.250081

https://royalsocietypublishing.org/doi/pdf/10.1098/rsos.250081

ABSTRACT

Late Cretaceous Earth was dominated by theropods such as tyrannosauroids and megaraptorans; however, it is unclear how these clades diversified and grew to massive proportions. This study aimed to conduct a biogeographical analysis and test climate as a potential mechanism for the increase in size. We used published phylogenetic matrices with the R package BioGeoBears to test different biogeographical hypotheses for both clades. We mapped body mass (BM) and body length against known climate data to test this potential hypothesis. Continental-scale variance did not drive tyrannosauroid biogeography and instead widespread ancestral populations, sympatric speciation and localized extinctions throughout these clades constricted geographic range. Both patterns were supported by statistical analyses. This biogeographical model also indicates the ancestor of the clade Tarbosaurus and Tyrannosaurus was present in both Asia and Laramidia, and therefore the ancestor of Tyrannosaurus came from Asia. Statistical data illustrated no correlation between Mean Annual Temperature (MAT) and BM but potential climatic shifts may be associated with gigantism in derived megaraptorids and eutyrannosaurians. This biogeographical model implies megaraptorans may have had a cosmopolitan distribution prior to the splitting of Laurasia and Gondwana. Also, gigantism in these clades may be associated with climatic shifts in the Late Cretaceous.

LINK(S)

https://royalsocietypublishing.org/doi/10.1098/rsos.242238

https://royalsocietypublishing.org/doi/pdf/10.1098/rsos.242238

ABSTRACT

The “mid-Cretaceous” record from northern Africa is characterised by a peculiar fauna of theropod dinosaurs, mostly referred to a “triumvirate” of clades: Abelisauroidea, Allosauroidea and Spinosauridae. The majority of this material is based on unassociated bones and has ignited a debate on the validity and inclusiveness of the named species, between “lumping” and “splitting” approaches. Although this debate has mostly focused on the alpha taxonomy, the impact of minimising the a priori assumptions on the diversity and inclusiveness of the taxa coded in the numerical analyses (“methodological splitting”) has barely been investigated. Here, we use new theropod material from the “Kem Kem beds” (Morocco) to test the “methodological splitting” approach on theropod phylogenetics. Revision of the theropod material from the Bahariya Formation (Egypt) described by Ernst Stromer in 1934 leads us to consider the Moroccan Deltadromeus as a junior synonym of Bahariasaurus. Using a large-scale phylogenetic analysis integrating ontogenetic information, all Kem Kem material results nested in the three lineages of the “triumvirate”. The “noasaurids” are reconstructed as a paraphyletic grade of Abelisauroidea, with Bahariasaurus as the largest representative and related to non-predatory taxa showing several convergences with the ornithomimosaurs. Kryptops palaios hypodigm is confirmed an abelisaurid-allosauroid chimaera. Our analysis also indicates that Eocarcharia dinops hypodigm is a spinosaurid-allosauroid chimaera, and supports recent suggestions for the exclusion of Carcharodontosaurus iguidensis from the latter genus. The Egyptian carcharodontosaurid specimen described by Ernst Stromer and recently renamed Tameryraptor markgrafi is reconstructed as sister taxon of Carcharodontosaurus saharicus neotype even following the updated coding of its morphology. A couple of fused frontals shows several similarities with the holotype of the enigmatic carcharodontosaurid Sauroniops but is less robustly built despite the comparable size. The “mid-Cretaceous” northern African theropod diversity cannot be resolved following “splitting” or “lumping” aprioristic approaches. Direct overlap of diagnostic elements is the only valid criterion for lumping non-associated material. In the absence of overlap in the sample, hypodigms based on “methodological splitting” should be preferred because they prevent topological artifacts biased by the unrecognised inclusion of chimaeras in the taxon sample.

LINK(S)

https://www.italianjournalofgeosciences.it/297/article-1220/beyond-the-stromer-s-riddle-the-impact-of-lumping-and-splitting-hypotheses-on-the-systematics-of-the-giant-predatory-dinosaurs-from-northern-africa.html

https://www.italianjournalofgeosciences.it/files/download/IJG/IJG%20Vol%20144%20(2025)%20f2/Cau%201291.pdf