Swiss Journal of Palaeontology最新文献

Nanhsiungchelys, the type genus of Nanhsiungchelyidae, is an extinct turtle taxon that lived during the Late Cretaceous in southern China. Despite having a relatively abundant fossil record, the plastral morphology of Nanhsiungchelys is not well understood. Here, we describe a large specimen of Nanhsiungchelys with an associated skull and shell (SNHM 1558) from the Upper Cretaceous of Nanxiong Basin, China. The skull of SNHM 1558 is similar to that of Nanhsiungchelys yangi, but the carapace bears a pair of stick-like anterolateral processes. For this reason, we tentatively refer SNHM 1558 to Nanhsiungchelys cf. yangi. A concave plastron and a narrower posterior lobe indicate that SNHM 1558 may be a male. Nanhsiungchelys spp. was previously regarded as the most advanced taxa of Nanhsiungchelyidae, but some morphological characteristics suggest plesiomorphic similarities with the outgroup Adocus spp. A phylogenetic analysis using Adocus spp. as the outgroup suggests that Nanhsiungchelys spp. and Anomalochelys angulata form a monophyletic group at the base of Nanhsiungchelyidae. However, this phylogenetic result is not conclusive, as Nanhsiungchelys spp. is found deeply nested within the tree when Sinaspideretes wimani is employed as the outgroup.

Supplementary information: The online version contains supplementary material available at 10.1186/s13358-025-00385-2.

Here, we present a new Cretaceous carettochelyid turtle, Byeoljubuchelys yeosuensis gen. et sp. nov., from the Lower Cretaceous Hasandong Formation of Yeosu, Korea. A nearly complete shell and select elements of the girdles and limbs provide crucial insight into the evolution and aquatic adaptation of this family. Phylogenetic analyses place Byeoljubuchelys yeosuensis at the most basal position within Carettochelyidae. The mid-sized plastron of Byeoljubuchelys yeosuensis appears to be plesiomorphic for the group. The expansion of the plastron during carettochelyid evolution, especially during the Paleogene, may be an evolutionary response to increasing body size or the threat of mammalian predators. Although the shell of Byeoljubuchelys yeosuensis lacks distinct scute sulci, traces are apparent that are reminiscent of juvenile scutes in the extant Carettochelys insculpta, suggesting that scute loss was facilitated in trionychian evolution through the thickening of the epidermis. Byeoljubuchelys yeosuensis possesses a plesiomorphic humerus with a proximally located lateral process and a sigmoidal shaft lacking torsion, implying rowing locomotion rather than the underwater flapping seen in more recent carettochelyids. The repeated acquisition of a softshell in two clades of trionychians during the mid-Cretaceous may be related to an environmental shift towards humid climates at that time, perhaps reflecting a remarkable adaptation to freshwater ecosystems.

Supplementary information: The online version contains supplementary material available at 10.1186/s13358-025-00415-z.

The hybodontiform shark-like Strophodus was a large durophagous predator with highly specialized crushing-type dentition that mainly inhabited Mesozoic marine environments for more than 130 million years, with a fossil record spanning from the Middle Triassic to the Lower Cretaceous. Strophodus was a geographically widespread taxon with 13 species reported from Africa, Asia, Europe, India and South America. Here, we describe a new species of Strophodus, which we name Strophodus timoluebkei sp. nov. based on three teeth from the same individual in semi-articulated position. The holotype was collected in the Prealpine Sulzfluh Limestone Formation (Middle Oxfordian to Late Tithonian), Central Switzerland. Strophodus timoluebkei sp. nov. currently is the only vertebrate species reported from this geological unit, and its presence suggests that this durophagous shark likely played an important role as predator of the invertebrate fauna in this ancient Tethyan tropical coastal ecosystem. The new discovery sheds additional light onto the hybodontiform paleodiversity during the Upper Jurassic.

Although trionychians have a rich fossil record, much of their fossil diversity is known from the Cretaceous and Paleogene, and little is known about their evolutionary history in the Neogene. We here describe cranial and shell material of trionychians from the Early Miocene Moghra Formation of Egypt that we attribute to a new carettochelyid taxon, Allaeochelys meylani sp. nov., and to the Trionyx lineage. Allaeochelys meylani sp. nov. fills a temporal gap between previously described taxa and exhibits a series of unique features, including greatly thickened cranial bones, a broad bony wall posterior to the orbit, a large fossa formed by the maxilla and premaxilla at the anterior third of the triturating surface, and a medial process on peripheral II. Allaeochelys meylani sp. nov. also documents the oldest occurrence of Carettochelyidae on the Afro-Arabian continent, while the Trionyx material reported herein provides unambiguous evidence for the presence of this lineage on the Afro-Arabian continent no later than the Early Miocene.

Soft-shelled turtles (Pan-Trionychidae) are one of the primary clades of turtles with a particularly rich fossil record reaching back to the Early Cretaceous. Yet, the evolution of the group has been difficult to resolve, in part because the fossil record mostly consists of shells and because the shells are known to exhibit high levels of polymorphism, making it difficult to establish parsimony-informative characters. A revision of the shell osteology of extant and extinct pan-trionychid turtles resulted in the development of 69 revised and novel characters with over 221 derived character states. Of these, 40 are multistate characters and 11 morphometric characters that utilize length, surface, and angular measurements. In a first step, the characters were scored for 530 regularly developed individuals representing all currently recognized species of living trionychids. The primary dataset confirms that most characters are affected by high levels of polymorphism. Statistical analyses conclude that much variability can be attributed to ontogenetic changes. In a second step, the primary data was used to code terminal taxa by reference to the most adult individuals for characters controlled by ontogeny. Terminals were otherwise only scored polymorphic if at least 20% of individuals displayed a particular character state. A phylogenetic analysis concludes that the new characters converge best upon the emerging molecular consensus, if characters are run ordered. All three utilized outgroups have a negative impact on ingroup relationships and character evolution, which can only partially be addressed through the use of a molecular backbone. The reduction of polymorphism by reference to adults and a minimum frequency of 20% yields more parsimony-informative characters and character states. A brief account is provided on how to diagnose all extant clades and species of trionychids using osteological characters.

Supplementary information: The online version contains supplementary material available at 10.1186/s13358-025-00360-x.

Phenotypic intraspecific variation of organisms is essential for evolution and, thus, has the potential to provide crucial insights into evolutionary dynamics. Additionally, ontogeny is often intricately linked with the evolutionary trajectories of organisms. In this study, we explore the relationship between the magnitude and ontogenetic pattern of intraspecific variation, and the interrelationships of organisms, their geographic distribution, and species duration. We analyzed the intraspecific variation in the whorl expansion rate (WER) of several Late Cretaceous ammonoid species, including Hypophylloceras ramosum, Phyllopachyceras ezoense, Gaudryceras tenuiliratum, Tetragonites glabrus, T. popetensis, Damesites damesi, Tragodesmoceroides subcostatus, Subprionocyclus minimus, Yezoites puerculus (all from Hokkaido, Japan), as well as Scaphites whitfieldi and Hoploscaphites comprimus (both from North America). Our results reveal a weak to moderate, negative correlation between the magnitude of intraspecific variation and geographic distribution. The correlation between intraspecific variation and species duration is weak. Notably, scaphitid and phylloceratid ammonoids exhibit a higher degree of intraspecific variation compared to other species, although no significant differences are apparent within each family. Additionally, scaphitid species from both Japan and North America display similar ontogenetic patterns of intraspecific variation. Hypophylloceras ramosum exhibits a pattern of intraspecific variation, differing from other normally coiled ammonoids. In other taxa, the pattern among species cannot be distinguished. These discoveries suggest that intraspecific variation, geographic distribution, and species duration are, at least, not positively correlated. However, contrary to previous studies, our data suggest a potential link between intraspecific variation and the interrelationships of species (relative phylogenetic position). Further research involving the analysis of more taxa, multiple morphological parameters examined over longer ontogenetic stages, and the development of a robust phylogenetic hypothesis are necessary to better understand these associations.

Supplementary information: The online version contains supplementary material available at 10.1186/s13358-025-00397-y.

The Upper Cretaceous European vertebrate fossil record has improved significantly in the past three decades but there still remain chronostratigraphic and geographic gaps, which obscure our understanding of the paleobiogeography and evolution within the insular environments of the Late Cretaceous European Archipelago. Recently, a new vertebrate locality of late Santonian-early Campanian age was discovered in westernmost Bulgaria, promising to fill some of these gaps. Here, we use a multidisciplinary approach involving palynology, paleontology and paleohistology to investigate aspects of the paleoecology and taphonomy of this new locality and to provide preliminary information on its taxonomic contents. Palynomorph data shows that the flora was dominated by angiosperms of the Normapolles group with subordinate presence of ferns and only rare gymnosperms. The association of the pollen taxa Krutzschipollis crassus and K. spatiosus supports latest Santonian to early Campanian age for the vertebrate-bearing strata. The floral composition and especially a number of fern spore humidity indicators imply the existence of a generally humid subtropical climate, with some seasonal droughts. Using palynofacies analysis, we infer a coastal, proximal shelf to oxidated deltaic or lagoonal depositional environment for the examined sedimentary succession. The locality has so far yielded 250 vertebrate specimens collected from eight strata. There are at least seven clades present, including lamniform sharks, lepisosteid gars, amphibians, turtles, crocodylomorphs, ornithopod and titanosaur dinosaurs, and possibly pterosaurs. Semi-aquatic and aquatic animals dominate the assemblage. Most common are turtles (about 30% of the sample), followed by dinosaurs. Skeletal elements are disarticulated, isolated and mostly fragmentary. Fossils are not sorted by size. Many of the fossil bones show signs of abrasion and bioerosion, both micro- and macroscopically. Paleohistological data reveal that all sampled dinosaur bones belong to subadult or adult individuals. We interpret the site to be an attritional assemblage. Taxonomic comparisons with other well-known Santonian to Maastrichtian fossil assemblages from Central (Hungary and Austria) and Eastern Europe (Romania and Serbia) indicate similarities with both the Santonian Iharkút-Ajka vertebrate fauna of Hungary and the younger Haţeg Island fauna of Romania, although additional material and more precise taxonomic identification of the Bulgarian fossils is needed. Our work presents the first more in-depth look at life on land in this currently underexplored part of the Late Cretaceous European Archipelago.

Supplementary information: The online version contains supplementary material available at 10.1186/s13358-025-00388-z.

Ontogenetic shell shape changes of turtles are often only documented for individual species. It is currently unclear how shell shape changes during ontogeny across species, if there are common trends, and at what point in ontogeny individuals reach their adult morphology. Inspired by questions of whether some morphologies are too juvenile to be included into macroevolutionary studies of shell shape, we develop ontogenetic shell shape curves based on landmarked 3D shell shapes of turtles. Species-specific allometric shape regressions confirm that turtles show marked ontogenetic shell shape change. Geometric morphometric analysis shows that juvenile turtles have rounded shells, and ontogenetic differentiation between species increases adult turtle disparity. Disparity analysis indicates that juvenile shells across turtle clades are more similar than adult shapes, suggesting an important role of developmental constraints on early turtle shell shape, and possible adaptive post-natal ontogenetic changes that produce the observed adult shell shape disparity. Ontogenetic shell shape curves indicate when turtles converge onto adult morphologies, here quantified as 85% the distance between juvenile shape and maximum size adult shape. This happens at about 65% of the species-specific maximum carapace sizes. Sexual shell shape dimorphism is comparatively low across turtles even in the presence of pronounced sexual size dimorphism. These preliminary results provide guidance for studying shell shape macroevolution, but need to be scrutinized further in the future by data addition.

Supplementary information: The online version contains supplementary material available at 10.1186/s13358-025-00395-0.

Even though many early stem turtles are known from relatively well-preserved skulls, their neuroanatomy remains poorly understood, limiting insights into key cranial and ecological transitions. Here we reconstruct the brain, nerves, inner ears, olfactory endocasts and arteries of two early stem turtles-the Early Jurassic Kayentachelys aprix and the Middle Jurassic Eileanchelys waldmani-based on high-resolution imaging. These species document key phases of turtle cranial evolution. Our analysis documents intermediate conditions of Jurassic mesochelydians between earlier Triassic stem turtles such as Proganochelys quenstedtii and crown Testudines. We show that changes in the canalis cavernosus, geniculate ganglion positioning, and braincase architecture are related to cranial stiffening in turtles. Whereas Kayentachelys aprix retains plesiomorphic features of Triassic testudinatans (e.g., separation of recessus scalae tympani and cavum acustico-jugulare; flat processus interfenestralis morphology) or intermediate features (e.g., cranio-quadrate space modified to short canalis cavernosus; clearly tympanic stapes but with robust morphology; reduced prootic foramen but absence of secondary braincase wall of parietal-pterygoid contact), Eileanchelys waldmani shows essentially 'modern' braincase architecture, including a ventrally inclined processus interfenestralis and a fully developed cavum tympani. Additionally, anatomical traits associated with olfaction and hearing provide insights into the paleoecology of these taxa, supporting a terrestrial lifestyle for Kayentachelys aprix and aquatic adaptations in Eileanchelys waldmani. Our study highlights the utility of neuroanatomical data in refining hypotheses of turtle cranial evolution and ecology, and underscores the importance of Jurassic stem turtles for understanding the origins of crown-group traits.

The evolutionary radiation of diapsid reptiles that includes all extant and most extinct reptiles is well-represented in the Mesozoic and Cenozoic fossil records, however, the earliest stages recorded in the Paleozoic Era are limited to comparatively few taxa. Consequently, the origins of Sauria, the crown-group of Diapsida, remains poorly understood and the phylogenetic positions of the few known taxa along the saurian stem are controversial. Here, we describe Akkedops bremneri sp. et gen. nov., a new early late Permian stem saurian from the Karoo of South Africa based on two skulls and show that the famous aggregation of "juvenile Youngina" SAM-PK-K7710 is also referrable to it, thereby making this one of the best-known stem saurians. The skull has a short rostrum, open lower temporal bar, large contribution of the postfrontal to the upper temporal fenestra, slender stapes, sliver-like supratemporal with a distinct lateral flange suturing to the postorbital, and lacks both postparietal and tabular bones. The saddle-shaped quadrate is rather saurian-like in being posteriorly emarginated with a tympanic crest and unique medial flange. The post cranial skeleton of Akkedops bremneri is lizard-like and notably shows a hook-shaped fifth metatarsal and thyroid fenestra. Phylogenetic analysis recovers Akkedops bremneri as sister to Sauria, which is especially surprising considering its rather small size and slender, lizard-like morphology prior to the split between the apparently similar lepidosauromorphs and many of the comparatively robust archosauromorph saurians. Our analysis also indicates that Youngina capensis falls outside the clade of Akkedops bremenri + Sauria and does not appear to form a clade with other "younginiform" reptiles. The available evidence indicates a surprising level of complexity related to the evolution of stem saurians and the origin of Sauria that occurred in the shadow of other Paleozoic amniotes.

Supplementary information: The online version contains supplementary material available at 10.1186/s13358-025-00351-y.