PALEONTOLOGY IN APRIL, 2025

ABSTRACT

The role of ecological interactions and abiotic factors in shaping macroevolutionary patterns has been extensively debated. Yet, the effect of predator-prey interactions on diversification dynamics is unclear. Here, we test the influence of predator-prey interactions in the diversification of saber-toothed cats, a subfamily of felids (Felidae: Machairodontinae) that developed a highly specialized morphology, the notoriously long upper canines. This morphology has been associated with a high degree of trophic dependence on large prey, which is assumed as one of the main reasons for the group’s demise. To test the hypothesis that prey availability affected the diversification of sabertooths we examined whether shifts in speciation and extinction rates were linked with changes in the species richness of their potential prey clades. The only association we detected was between the increase in extinction rates of North American sabertooths and the decline in Equidae richness. However, when accounting for the prey richness per species, regardless of taxonomic affiliation of the prey, we found that the endpoint of most sabertooth taxa occurred when prey richness for that taxon was at its lowest. Our analyses then suggested that reduced prey richness was associated with increased extinction risk. These results support the hypothesis that the extinction of sabertooths was associated with the decline in megafauna, but extend it to more remote times, millions of years before their final demise, suggesting that prey availability contributed to drive the diversification dynamics of the group. More broadly, our findings highlight the importance of ecological interactions in shaping macroevolutionary patterns.

LINK(S)

https://academic.oup.com/jeb/advance-article-abstract/doi/10.1093/jeb/voaf043/8115575?redirectedFrom=fulltext

ABSTRACT

Seven years separate the naming of Megalosaurus bucklandii from its inauguration into paleoart in 1831, an event that also marked the first flesh reconstruction of a non-avian dinosaur. Megalosaurus has been a mainstay of paleoart ever since, but its popularity as subject matter has wavered. Widespread interest was achieved in the mid-1800s, associated with display of a life-size model in the Crystal Palace park grounds of Victorian London, but competition from other, more completely known dinosaurs diminished its paleoart role in the 20th century. Internationally, modern paleoartists have featured Megalosaurus increasingly rarely and, in professional paleoartistry, projects associated with British research institutions have largely driven contemporary M. bucklandii reconstructions. The reconstructed appearance of Megalosaurus has perhaps changed to a greater degree than that of any other dinosaur and recent opinions on their restorability vary. An assessment of M. bucklandii fossils suggests that they are neither beyond restoration nor the ‘generic’ theropods of many depictions, but stout-limbed, long-snouted and potentially crested species of unique visual character.

LINK(S)

https://meridian.allenpress.com/esh/article-abstract/44/1/202/506696/THE-PAST-PRESENT-AND-FUTURE-OF-MEGALOSAURUS

ABSTRACT

The origin and early diversification of ornithopods, a major clade of ornithischian dinosaurs, remain poorly understood, with conflicting phylogenetic hypotheses regarding rootward neornithischian relationships. Some topological stability is inferred near the basal divergence of Iguanodontia, though the ingroup relationships remain unclear. For instance, Rhabdodontidae, a clade of Late Cretaceous European ornithopods ‘traditionally’ considered to include eight to nine species, presents significant taxonomic challenges. We explore the diversity and disparity of European Rhabdodon-lineage iguanodontians. We assembled a novel dataset comprising morphological and morphometric data obtained from rhabdodontomorph dentaries, which are abundant, well-preserved in the majority of the taxa, and distinctive. Special attention is given to Rhabdodon septimanicus, a poorly known taxon from the upper Campanian to lower Maastrichtian of southern France, established based on a particularly robust dentary bone that has been subjected to conflicting taxonomic interpretations. Our restudy of the specimen, combined with a multivariate and phylogenetic assessment, shows that this taxon is a clear morphological outlier among European rhabdodontomorphs, providing a basis for its assignment to a new genus, Obelignathus. Although further large-scale studies, especially detailed osteological descriptions, are needed to clarify the taxonomic significance of certain European rhabdodontomorphs, our results indicate that the group exhibits greater diversity than currently recognized, with several sympatric taxa co-occurring, at least in southern France and possibly also in Romania.

LINK(S)

https://www.nature.com/articles/s41598-025-98083-z

https://www.nature.com/articles/s41598-025-98083-z.pdf

ABSTRACT

The absence of terrestrial apex predators on oceanic islands led to the evolution of endemic secondary apex predators like birds, snakes and crocodiles, and loss of defence mechanisms among species. These patterns are well documented in modern and Quaternary terrestrial communities of the West Indies, suggesting that biodiversity there assembled similarly through overwater dispersal. Here, we describe fossils of a terrestrial apex predator, a sebecid crocodyliform with South American origins from the late Neogene of Hispaniola that challenge this scenario. These fossils, along with other putative sebecid specimens from Cuba and Puerto Rico, show that deep-time Caribbean ecosystems more closely resembled coeval localities in South America than those of today. We argue that Plio-Pleistocene extinction of apex predators in the West Indies resulted in mesopredator release and other evolutionary patterns traditionally observed on oceanic islands. Adaptations to a terrestrial lifestyle documented for sebecids and the chronology of West Indian fossils strongly suggest that they reached the islands in the Eocene–Oligocene through transient land connections with South America or island hopping. Furthermore, sebecids persisted in the West Indies for at least five million years after their extinction in South America, preserving the last populations of notosuchians yet recovered from the fossil record.

LINK(S)

https://royalsocietypublishing.org/doi/10.1098/rspb.2024.2891

https://royalsocietypublishing.org/doi/epdf/10.1098/rspb.2024.2891

ABSTRACT

Saratovia glickmani, gen. et sp. nov., is described based on a dentary symphysis fragment from the Upper Cretaceous (upper Cenomanian) Melovatka Formation at Saratov, Russia. This specimen was found by L.S. Glickman in late 1940s and was referred previously to Ornithocheirus, Anhanguera, or Coloborhynchus. S. glickmani is attributed to Targaryendraconia because of strongly scalloped and subparallel lateral margins of dentary symphysis, which is transversely narrow, with the interalveolar width subequal to the alveolar width. It differs from all known targaryendraconians by having a dentary crest. The new taxon differs from all toothed pterodactyloids by lack of median groove on dentary symphysis. Instead, it has a raised flat platform pierced by numerous relatively large nutrient foramina, which are connected by short canals with a median canal within this platform. S. glickmani is one of the latest toothed pterosaurs known in the fossil record.

LINK(S)

https://www.scielo.br/j/aabc/a/j976f3Xdd9fhH6jgxxNt6FJ/abstract/?lang=en

https://www.scielo.br/j/aabc/a/j976f3Xdd9fhH6jgxxNt6FJ/?lang=en&format=pdf

ABSTRACT

Most polycotylid plesiosaurians have isodont dentition with relatively small and slender conical teeth. However, large and robust caniniform teeth are known for some of their basal late Albian and early Cenomanian representatives, implying greater ecological diversity early in the evolutionary history of the clade. Here we report the first evidence of polycotylids with large teeth in the Campanian, thus c. 15 Myr younger than previous records. Several teeth with crowns exceeding 40 mm in height and some reaching 25 mm in basal diameter were collected from two Campanian localities in European Russia. These are the largest polycotylid teeth reported from the Cretaceous of Eurasia. Their large size and specific enamel ornamentation markedly differ from other known polycotylid teeth, suggesting that these teeth belong to an undescribed taxon. However, similar enamel ornamentation was previously reported for the now forgotten ‘Piratosaurus plicatus’ Leidy, 1865 from the Upper Cretaceous of Canada, which may indicate the wide distribution of polycotylids with such teeth in the latest Cretaceous. Unlike classical polycotylids, the new teeth have strong apical wear which implies consumption of abrasive prey, similar to modern killer whales that feed on sharks. Thus, our finding reveals higher ecological diversity of polycotylids in the latest Cretaceous, suggesting the coexistence of small- to medium-toothed and large-toothed (probably “latirostrine”) taxa at different times of the evolutionary history of the Polycotylidae.

LINK(S)

https://www.sciencedirect.com/science/article/pii/S2095383625000604

ABSTRACT

A variety of small ornithischian dinosaur specimens collected from the Upper Jurassic Morrison Formation of Colorado and Wyoming were described by O.C. Marsh in the late 19th century. These include Nanosaurus agilis, N. rex, Laosaurus celer, L. gracilis, and L. consors. Another taxon from Wyoming, Drinker nisti, was added to this list more recently. The taxonomy of these species has undergone numerous revisions, with differing opinions regarding their validity and potential synonymies and in terms of the specimens referred to each of them. Their systematics have also been debated, with some taxa regarded as ornithopods and others as earlier diverging ornithischians. Here, we provide a critical reappraisal of these species based on first-hand examination of their type specimens. None of the relevant holotypes or syntype series exhibit either autapomorphies or unique character combinations that could be used to support their validity, and we regard all of these taxa as nomina dubia. Most of these specimens can be identified only as indeterminate neornithischians, but some include juvenile iguanodontian remains. “Drinker” possesses some dental and skull features that are known only in pachycephalosaurs, raising the possibility that this material represents an early diverging member of this clade. Other specimens formerly referred to these taxa should be regarded as indeterminate until they have been restudied in detail in order to establish their affinities rigorously and determine the true species richness of the Morrison Formation ornithischian fauna.

LINK(S)

https://bioone.org/journals/bulletin-of-the-peabody-museum-of-natural-history/volume-66/issue-1/014.066.0102/A-Review-of-Nanosaurus-agilis-Marsh-and-Other-Small-Bodied/10.3374/014.066.0102.short

ABSTRACT

Modern ants are among the most ecologically dominant animal groups on Earth, with their diversity shaped by global events occurring since their origin in the late Mesozoic. The so-called hell ants of the subfamily Haidomyrmecinae comprise a group of morphologically unique ants exclusive to the Cretaceous. They represent some of the earliest known ants in the fossil record, preserved as amber inclusions in deposits in France, Myanmar, and Canada. Here, we report the oldest known Haidomyrmecinae, preserved as a rock impression in limestone of the Crato Konservat-Lagerstätte in northeastern Brazil. This finding also represents the earliest undisputed ant known to science. Micro-computed tomography applied to phylogenetic analysis of early ants shows that the new species is closely related to hell ants found only in Burmese amber. The presence of hell ants in the Aptian of northeastern Brazil provides the earliest evidence of Formicidae biogeographic history through deep time. The distribution of known clades indicates that hell ants were widely distributed, with repeated interchanges between Cretaceous landmasses. Notably, northeastern Brazil’s paleoenvironment contrasts with other known deposits for Haidomyrmecinae, suggesting ecological diversity among these ants. Hell ants thrived for a long time in gymnosperm-dominated and mixed landscapes, such as the Crato paleoenvironment, persisting into the angiosperm expansion before being decisively affected by geological events toward the Cretaceous end.

LINK(S)

https://www.cell.com/current-biology/fulltext/S0960-9822(25)00308-2

https://www.cell.com/action/showPdf?pii=S0960982225003082

ABSTRACT

Transmarine distribution and gigantism in the Late Cretaceous North American crocodyliform Deinosuchus has been difficult to reconcile with consistently inferred phylogenetic relationships to alligatorids, an otherwise freshwater and smaller-bodied group. We present an expanded phylogeny with increased spatiotemporally coherence that reinterprets species of Deinosuchus as stem-group crocodylians together with further putative alligatoroids, Leidyosuchus canadensis and the European Diplocynodon spp. (closely related to North American Borealosuchus). The novel topology elucidates the evolution of osmoregulation in Crocodylia and its close relatives by inferring plesiomorphic saltwater tolerance for Deinosuchus and the crown-group as well as secondary loss already in stem-group alligatorids. Divergence of Alligatoroidea coincided with extreme mid-Cretaceous sea level highs and the distribution of Deinosuchus across the Western Interior Seaway can be best explained by marine dispersal. Phylogenetic body-length analysis using a head-width proxy reveals phyletic dwarfism early in alligatoroid evolution and a reasonable total length estimate for the most complete specimen of Deinosuchus riograndensis. We find that gigantism in crocodyliforms is correlated with high-productive extensive aquatic ecosystems in the present and the past.

LINK(S)

https://www.nature.com/articles/s42003-025-07653-4

https://www.nature.com/articles/s42003-025-07653-4.pdf

ABSTRACT

The allosauroid theropod dinosaurs of the clade Carcharodontosauridae were the apex predators in terrestrial ecosystems of the Early Cretaceous but were replaced in this ecological niche by Tyrannnosauridae in the Late Cretaceous. Details of this turnover are poorly known because only two transitional ecosystems, containing both carcharodontosaurids and tyrannosauroids, had been recognized to date (Cenomanian Cedar Mountain Formation of Utah, USA, and Turonian Bissekty Formation of Uzbekistan). Moreover, the presence of carcharodontosaurids in the Bissekty Formation, based on a maxilla fragment identified as Ulughbegsaurus uzbekistanensis Tanaka et al., 2021, has been recently questioned. Here we report on the third ecosystem containing both clades of apex predators, the Cenomanian Khodzhakul Formation in Uzbekistan. This new occurrence of Carcharodontosauridae is based on a newly identified maxilla that closely resembles the holotype maxilla of U. uzbekistanensis and is identified as Ulughbegsaurus sp. The revised morphological characters of both specimens support attribution of Ulughbegsaurus to Carcharodontosauridae. We report a novel neurovascular feature of the theropod maxilla—a medial alveolar canal that supplied the alveoli medially and contained tributaries of the palatine vessels in Ulughbegsaurus.

LINK(S)

https://www.cambridge.org/core/journals/journal-of-paleontology/article/abs/first-record-of-carcharodontosauridae-dinosauria-theropoda-in-the-upper-cretaceous-khodzhakul-formation-of-uzbekistan/7068DD313B954E2DB7EC507F956EFE73

ABSTRACT

Gigantism in terrestrial tortoises occurred frequently and convergently in different lineages of Testudinidae. Despite the fact that giant forms were geographically and stratigraphically widespread in South America, Pleistocene members are still very poorly known, most of them represented by fragmentary and unassociated materials. The aim of the present contribution is to describe Chelonoidis pucara n. sp., a new species coming from Upper Pleistocene beds of northern Buenos Aires province, Argentina. The new species is known by the anterior half of a plastron having a unique combination of apomorphic and plesiomorphic features. It is very large-sized (estimated carapace length about 1.7-1.8 meters), rendering it as the largest testudinid from South America, and placing it among the “supergigantic” tortoise phenotype. Like other supergigantic tortoises (which were up to now exclusively known in the Old World), the new species shows enlarged epiplastral projections, probably related to competition with other males. The ecological role of these “supergigantic” tortoises is also briefly discussed.

LINK(S)

https://riviste.unimi.it/index.php/RIPS/article/view/27229

ABSTRACT

Dire wolves (Aenocyon dirus) are extinct predators of Pleistocene North America. Although phenotypically similar to living wolves (Canis lupus), dire wolves have yet to be placed confidently in the canid family tree. We generated 3.4× and 12.8× paleogenomes from two well-preserved dire wolves dating to > 13,000 and > 72,000 years ago, and estimated consensus species trees for these and 10 canid species. Our results revealed that ∼2/3 of dire wolf ancestry is derived from a lineage sister to the clade comprising the gray wolf, coyote, and dhole, and the remaining ∼1/3 from a lineage near the base of Canini diversity. We identified 80 genes evolving under diversifying selection in dire wolves. Our results underscore the power of paleogenomes to resolve long-standing taxonomic questions and contribute to growing evidence of the role of post-speciation gene flow as an evolutionary force.

LINK(S)

https://www.biorxiv.org/content/10.1101/2025.04.09.647074v1

https://www.biorxiv.org/content/biorxiv/early/2025/04/11/2025.04.09.647074.full.pdf

ABSTRACT

Aenocyon dirus played a crucial role as a predator in late Quaternary megafaunal communities throughout southern North America. This article presents two new occurrences of the species from southwest Iowa on the eastern Great Plains, updates the Peccary Cave record in the southern Ozark Highlands, and amends the fossil record of the species. In southern North America, there are 166 occurrences of A. dirus, spanning Marine Isotope Stage (MIS) 2-19, with at least two-thirds (n = 112) of the occurrences dating to MIS 2-3 (11,600–57,000 cal B.P.). A. dirus fossils are found across this region, with notable concentrations in California, Florida, the Ozark Highlands, and broadly across the southern Great Plains. Consideration of Canis specimens from the lead region (covering contiguous parts of Illinois, Wisconsin, and Iowa) previously identified as Canis mississippiensis (and sometimes synonymized with A. dirus or C. lupus) reveals they are actually C. lupus. The terminal extinction of A. dirus occurred sometime after 12,800 cal B.P. The Iowa finds, consisting of a radius and a partial cranium, are the first records for the state. Zooarchaeology by mass spectrometry confirms these records, as well as the Peccary Cave record, are A. dirus, as opposed to C. lupus. The Iowa specimens are directly dated to 29,040–28,410 cal B.P. and 14,325–14,075 cal B.P., while Peccary Cave is dated to 25,350–21,405 cal B.P. These results place A. dirus in the interior of southern North America before, during, and after the Last Glacial Maximum (26,500–19,000 cal B.P.). Stable nitrogen isotope (δ15N) values of bone collagen from the younger of the two Iowa records suggest this individual did not regularly compete for prey with Smilodon fatalis during the Bølling-Allerød Chronozone (14,640–12,850 cal B.P.). To the south, at Peccary Cave, considerations of prey size, prey abundance, and isotopic data strongly suggest Platygonus compressus was the focal prey species.

LINK(S)

https://peerj.com/articles/19219/

https://peerj.com/articles/19219.pdf

ABSTRACT

Cienciargentina sanchezi gen. et sp. nov. is a new rebbachisaurid sauropod dinosaur from the Late Cretaceous of Argentina. The new species is erected on the basis of a unique combination of characters that includes many autapomorphies, among them: cervical epipophyses absent, anterior dorsal centra amphicoelous to slightly opisthocoelous, posterior dorsal centrum slightly opisthocoelous, posterior dorsal neural spines anteroposteriorly extended, mid and posterior dorsal vertebrae with intrapostzygapophyseal lamina supporting the postzygapophyses from below, middle and posterior dorsal vertebrae with accesory spinodiapophyseal lamina, lateral laminae in anterior caudal vertebrae formed by the spinoprezygapophyseal lamina and the spinopostzygapophyseal lamina, which fuse at the middle of the neural spine, anterior caudal vertebrae with spinoprezygapophyseal lamina more robust than spinopostzygapophyseal lamina, anterior caudal transverse processes with a full suite of diapophyseal laminae (anterior centrodiapophyseal lamina, posterior centrodiapophyseal lamina, prezygodiapophyseal lamina, postzygodiapophyseal lamina), ratio of length to height of the posterior caudal vertebrae 5 or higher, forked chevrons without anterior and posterior projections, and femoral head dorsally directed, rising well above the level of the greater trochanter. This new species is added to the list of rebbachisaurid sauropods documented in the Huincul Formation (upper Cenomanian-Turonian), which are thought to be the latest diplodocoids at global level. In fact: from the Turonian onwards, sauropod communities are composed exclusively of macronarians, mostly titanosaurs. In Patagonia, particularly in the Huincul Formation, the hypothetical faunal turnover that occurred in the middle of the Cretaceous, which involved not only sauropods but other groups of dinosaurs, is observed, perhaps like nowhere else in South America.

LINK(S)

https://www.sciencedirect.com/science/article/abs/pii/S0195667125000606?via%3Dihub

ABSTRACT

Although globally scarce, Middle Jurassic dinosaur tracks are known from the Isle of Skye, Scotland, and help indicate the palaeoenvironmental preferences and behaviour of major dinosaur clades. Here, we report an extensive new tracksite from Skye: 131 in-situ dinosaur tracks at Prince Charles’s Point on the Trotternish Peninsula. The tracks occur in multiple horizons of rippled sandstones of the Late Bathonian aged Kilmaluag Formation, part of the Great Estuarine Group, which formed in a locally, shallowly submerged lagoon margin. We assign these tracks to two morphotypes, further divided into four morphotype subgroups, most likely representing large megalosaurid theropods, and sauropods that are either non-neosauropods or basal neosauropods. The trackways, although relatively short, evidence time-averaged milling behaviour, as observed at other tracksites in the Great Estuarine Group. The presence of sequential manus and pes sauropod tracks amends their previous identification by geologists as fish resting burrows, raising the potential that other such structures locally and globally may in fact be dinosaur tracks, and emphasises the predominant occurrence of sauropods in lagoonal palaeoenvironments in the Great Estuarine Group. At Prince Charles’s Point, however, unlike previously described lagoonal assemblages, large theropod trackmakers are more abundant than sauropods.

LINK(S)

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0319862

ABSTRACT

The Upper Jurassic beds of the Lusitanian Basin in central Portugal yield diverse dinosaurian fauna, dated to the Kimmeridgian–Tithonian interval. Saurischian dinosaurs are, overall, more abundant than their ornithischian counterparts, in terms of both specimens collected and species recognized. Iguanodontians are so far represented by the styracosternan Draconyx loureiroi, the dryosaurid Eousdryosaurus nanohallucis and the enigmatic dryomorphan Hesperonyx martinhotomasorum. Here we aim to highlight the diversity of this clade in the Late Jurassic of Portugal, presenting evidence for yet another species of ankylopollexian iguanodontian dinosaur, represented by the specimen SHN.JJS.015, which is housed at the Sociedade de História Natural, Torres Vedras. Detailed comparisons rule out attribution to previously known taxa, and phylogenetic analyses that include SHN.JJS.015 indicate early-diverging ankylopollexian affinities for this specimen. As there is no robust diagnosis, we do not erect a new formal species for it at this stage. Nevertheless, this specimen represents a previously unreported taxon that highlights greater diversity than previously estimated among the iguanodontians of the Late Jurassic and highlights the importance of Europe in diversification and dispersal events of this clade. A series of smaller, isolated femora from the same sub-basin as SHN.JJS.015 may represent the same taxon, presenting evidence of thriving communities of ankylopollexians during the Kimmeridgian–Tithonian interval in Portugal.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/14772019.2025.2470789?src=exp-la

ABSTRACT

Metriacanthosaurid theropods represent a basal-branching lineage of tetanurans. Members of this clade are mainly medium to large-sized and lived in Laurasia during the Middle Jurassic to the Early Cretaceous. In this clade, Sinraptor dongi, Sinraptor hepingensis, and Yangchuanosarus shangyouensis from the Late Jurassic are well represented by the nearly complete specimens, but the incompleteness of Middle Jurassic taxa hinders our knowledge of the origin and early evolution of Metriacanthosauridae. This paper describes a new genus and species of metriacanthosaurids, Yuanmouraptor jinshajiangensis gen. et sp. nov, from the Middle Jurassic Zhanghe Formation of Yunnan Province, China. The new taxon is represented by a cranium and the anterior section of the vertebral column including the complete cervical series and the first dorsal vertebra. Yuanmouraptor jinshajiangensis can be diagnosed based on the following autapomorphies: the anterior process of postorbital sheet-shaped and keeping consistent depth; ventral ramus of postorbital bearing a laterally twisted trough running along its lateral surface; ventral surface of axial intercentrum parallel with that of axial centrum; discontinuity of inclination on anterodorsal margin of the third and fourth cervical vertebrae; strongly posteriorly elongated epipophyses of anterior cervical vertebrae; deeply excavated pneumatic foramina on the third cervical vertebra; sheet-shaped and subrectangular neural spines of posterior cervical vertebrae. Phylogenetic analysis recovers Yuanmouraptor as the most basal-branching member within Metriacanthosauridae and provides a new alternative phylogenetic topology of non-coelurosaurian tetanurans.

LINK(S)

https://peerj.com/articles/19218/

https://peerj.com/articles/19218.pdf

ABSTRACT

Abundant fossil material from Niedźwiedzia Cave documented the presence of three canid species: Canis lupus spelaeus, Vulpes vulpes, and Vulpes lagopus. Dated on MIS 3, the canid assemblage is represented by large individuals of robust posture, typical for the cold phases of the Late Pleistocene. Canis lupus spelaeus is a characteristic element of Late Pleistocene steppe-tundra faunas; a short legged, very large wolf with a powerful dentition. The conducted analysis showed that wolves from Niedźwiedzia Cave are among the largest ever found. Because of the great variability of the postcranial material, any of the morphological features cannot be used as a clearly defined factor to distinguish between Vulpes vulpes and Vulpes lagopus. Accordingly, only metric characters allow for a clear determination of taxonomic affiliation.

LINK(S)

https://palaeo-electronica.org/content/2025/5489-canids-from-niedzwiedzia-cave

https://palaeo-electronica.org/content/pdfs/1510.pdf