Xenodens (mosasaur) new specimen + Martintriton, new salamander from Lower Cretaceous of Germany + Late Paleozoic tetrapods in eastern Pangaea + Lingyuanfructus + more

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

Recent papers:

Free pdf:

Nicholas R. Longrich, Nathalie Bardet, Nour-Eddine Jalil, Xabier Pereda-Suberbiola, Anne Schulp & Mohamed Ghamizi (2025)
New Information on the Morphology and Tooth Replacement of Xenodens calminechari (Squamata: Mosasauridae), a Unique Mosasaurid from the Maastrichtian Phosphates of Morocco
Diversity 17(12): 819
doi: https://doi.org/10.3390/d17120819
https://www.mdpi.com/1424-2818/17/12/819


Xenodens calminechari is a highly derived mosasaurid from the latest Maastrichtian Phosphates of the Oulad Abdoun Basin, Morocco. Originally described based on a single maxilla, Xenodens differs from all known squamates in its closely packed, bladelike marginal teeth and modified tooth implantation and replacement. Xenodens’ relationships and anatomy remain poorly understood, and a recent study suggested that the holotype represents a composite, and furthermore that the animal might represent a juvenile of Carinodens. Evidence from a new referred specimen of Xenodens and CT scans corroborate the original description of Xenodens. Scans of the holotype and referred specimen of Xenodens reveal highly derived tooth implantation; interdental ridges are reduced in the posterior part of the jaw and teeth implant in a groove, with adjacent roots contacting and fusing. Tooth roots bear large, deep replacement pits, as is typical of derived mosasaurids, but in posterior teeth the replacement pits merge lingually to create a single large pit for two teeth. We provide an updated diagnosis of Xenodens, detailing unusual features of its tooth anatomy, implantation and replacement. Differences between Xenodens and Carinodens are numerous and no intermediate morphologies exist; furthermore, the size overlap between Carinodens and Xenodens indicates that Xenodens cannot represent a juvenile Carinodens. Xenodens highlights the remarkable diversity of mosasaurids, as well as the exceptional range of ecological niches occupied by this highly successful group of marine reptiles before their extinction.

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Martintriton septatus gen. et sp. nov.

Pavel P. Skutschas, Veniamin V. Kolchanov, Andreas Lang, Julia A. Schultz & Achim H. Schwermann (2025)
Lissamphibian remains from the Lower Cretaceous of Germany with implications for the evolution of Late Jurassic–Early Cretaceous European faunas
Palaeobiodiversity and Palaeoenvironments  (advance online publication)
doi: https://doi.org/10.1007/s12549-025-00675-0
https://link.springer.com/article/10.1007/s12549-025-00675-0


Lissamphibian assemblages of Early Cretaceous age are rare in Europe. Here, we comprehensively describe the most informative lissamphibian remains from the Lower Cretaceous (Barremian–Aptian) Balve locality in Germany. The assemblage from Balve includes the salamandroid salamanders Balveherpeton hoennetalensis and Martintriton septatus gen. et sp. nov., as well as the albanerpetontid Wesserpeton sp. and an indeterminate frog (Anura indet.). Martintriton septatus gen. et sp. nov. is characterised by the following combination of atlantal characters: anterior cotyles large and rounded with almost flat articular surfaces continuous across lateral and ventral surfaces of broad intercotylar tubercle; posterior cotyle oval and laterally compressed; prominent ventrolateral ridges; irregularly located depressions separated by bony septa and several foramina of different sizes on ventral surface of centrum; short lateral ridge on lateral surface of centrum; and large foramina between the lateral and ventrolateral ridges. Martintriton septatus gen. et sp. nov. shares similarities in atlas morphology with the Paleogene batrachosauroidid Palaeoproteus miocenicus and the Late Cretaceous scapherpetids likely indicating a close relationship. The composition of the lissamphibian assemblage from Balve (= faunal association “frogs-crown salamanders-albanerpetontids”) resembles other most diverse Early Cretaceous European lissamphibian assemblages at the family level. The transition from the Jurassic to Cretaceous lissamphibian fauna in Europe is characterised by the retention of the albanepetontid Celtedens and, possibly, by extinction of stem karaurid salamanders.

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Vladimir I. Davydov, S. Spencer G. Lucas, Eugeny V. Karasev, Yunus Mamadzhanov & Mark D. Schmitz (2025)
Late Paleozoic tetrapods in eastern Pangaea: when and how did they get there?
Earth-Science Reviews 105344
doi: https://doi.org/10.1016/j.earscirev.2025.105344
https://www.sciencedirect.com/science/article/abs/pii/S0012825225003058


Highlights

A time gap in late Paleozoic tetrapods exists between western and eastern Pangaea.
In eastern Pangaea, tetrapods become abundant only in the mid-Permian and later.
CA-IDTIMS age of 292.14 ± 0.14 of the earliest tetrapods in E. Pangaea is obtained.
This age fits the model of the Precaspian Isthmus (PI) development at As-Sk transition.
The migration pattern through the time occurs though the PI and directly from Urals.

Abstract

The distribution and dispersal patterns of Late Paleozoic tetrapods remain poorly constrained. Diverse assemblages of Carboniferous and Permian tetrapods are well documented across western Pangaea, whereas in eastern Pangaea (east of the Ural seaway), tetrapods only become abundant from the mid-Permian onwards. It is unclear whether this discrepancy reflects imprecise chronostratigraphy or a genuine absence of Carboniferous–Early Permian tetrapods in eastern Pangaea. Recently proposed vicariance models of tetrapod evolution incorporate several questionable datasets, and existing palaeogeographic reconstructions of western–eastern Pangaean connections remain controversial, requiring improved constraints and documentation. We report a CA–IDTIMS radioisotopic age of 292.14 ± 0.14 Ma (Sakmarian) from one of the earliest tetrapod (discosauriscid) in the East Pangaea localities in Tajikistan, that is closely resembling discosauriscid assemblages from Kazakhstan. This age supports the recently proposed model for the development of the Precaspian Isthmus during the Asselian–Sakmarian transition, interpreted as the first terrestrial corridor enabling tetrapod dispersal from western to eastern Pangaea. Integrated analyses of regional paleogeography, tectonics, palaeoclimate, palaeobiogeography, palaeofacies, and heavy-mineral provenance indicate that tetrapod migration pathways evolved through time: the initial eastward dispersal occurred via the Precaspian Isthmus during the Asselian–Sakmarian transition, whereas subsequent migrations (late Kungurian, late Roadian, Wuchiapingian, and Changhsingian) proceeded both directly eastward from the East European Platform and through recurrent connections across the Precaspian corridor.

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Leny Montheil, Alexis Licht, K. Christopher Beard, Grégoire Métais, Pauline Coster, Bram Vaes, Yannick Donnadieu, Erwan Pineau, Laurent Husson & Guillaume Dupont-Nivet (2025)

Across ancient oceans: Eocene dispersal routes of Asian terrestrial mammals to Europe, Afro-Arabia and South America
Earth-Science Reviews 105352
doi: https://doi.org/10.1016/j.earscirev.2025.105352
https://www.sciencedirect.com/science/article/abs/pii/S0012825225003137


During the middle and late Eocene, Asian terrestrial mammals dispersed to Europe, while primates and rodents dispersed across the 500-to-2000 km wide Neotethys Ocean and the 1500-to-2000 km wide Atlantic Ocean to colonize Afro-Arabia and South America. This study explores how these mammals have achieved such remarkable and enigmatic dispersals. We present high-resolution paleogeographic models for the middle to late Eocene based on updated plate kinematic reconstructions, paleo-bathymetry and paleo-topography data. With this, we evaluate landmass configurations and connectivity that may have facilitated faunal exchanges from Asia toward Europe, Afro-Arabia, and South America and discuss dispersal mechanisms between these biogeographic provinces. Our reconstructions reveal that during the Bartonian (~40–38 Ma), an overland dispersal corridor between Asia and Balkanatolia became available to terrestrial mammals and acted as a pivotal pathway for Asian faunas dispersing toward western Europe and Afro-Arabia. We identified two Balkanatolian island-hopping routes across the Western Neotethys potentially enabling the dispersal of small-bodied Asian primates, rodents and artiodactyls to Afro-Arabia. Alternatively, these taxa may have rafted across the Central Neotethys. By ~34 Ma, Balkanatolia fully connected with Western Europe, opening a southern “Grande Coupure” route for Asian faunas. In the Atlantic, we identify long-distance rafting as the most plausible mechanism for the 40–34 Ma transoceanic dispersal of the Asian-originated primates and rodents from Afro-Arabia to South America despite the likely presence of sparse islands along the Walvis Ridge and the Rio Grande Rise.

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Free pdf:

Lingyuanfructus hibrida gen. et sp. nov. (fossil plant)

Xin Wang (2025)
Lingyuanfructus: The First Fossil Angiosperm with Naked Seeds
Life 15(12): 1827
doi: https://doi.org/10.3390/life15121827
https://www.mdpi.com/2075-1729/15/12/1827

Unlike gymnosperms with naked ovules, angiosperms are defined and characterized by their enclosed ovules. According to plant evolution theories, angiosperms should be derived from their gymnospermous ancestors, which have naked ovules. Thus, an assumed transitional plant is expected to have started but not yet completed the enclosing of its ovules; specifically, some of its ovules are enclosed while others are not. This unusual expectation is, although rational, paradoxical: If this is so, is the plant a gymnosperm or an angiosperm? To date, such an expectation has never been met by any fossil evidence. The lack of favorable evidence makes the above expectation speculative and leaves evolutionary theorists vulnerable to attacks from their opponents. Here, I report a fossil plant, Lingyuanfructus hibrida gen. et sp. nov., from the Yixian Formation (Lower Cretaceous) of Liaoning, China, that meets this expectation. With young seeds both naked and enclosed in a single specimen, Lingyuanfructus defies any placement among seed plants and blurs the otherwise distinct boundary between angiosperms and gymnosperms, consolidating the foundation for evolutionary theory.

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Free pdf:

Spinograna myanmarensis gen. et sp. nov

Xin Wang & Weijia Huang (2025)
The spiniest seeds found in Mid-Cretaceous Myanmar amber
BMC Plant Biology 25: 1643
doi: https://doi.org/10.1186/s12870-025-07654-9
https://link.springer.com/article/10.1186/s12870-025-07654-9


Although angiosperms occurred earlier, their radiation did not occur until the Middle Cretaceous. Owing to a lack of knowledge of early angiosperms, this radiation used to be mistaken for the origin of angiosperms and became Darwin’s “abominable mystery”. Palaeobotanical progresses in recent decades have released more information on early angiosperms, especially their Middle Cretaceous radiation. The fossil angiosperms from Myanmar amber shed unique light on the evolution and diversity of angiosperms due to their exquisite preservation. To enhance our understanding of this fossil lägerstatte, here we report a new fossil angiosperm named Spinograna myanmarensis gen. et sp. nov. from Myanmar amber. The fossil is a fruit bearing spiny seeds. Its seeds are unique in morphology: they are discoid in form, with marginal furcated spines. This unique morphology represents an extremity in seeds: it is the spiniest seed in plant history, implying that they were dispersed by animals, a fact that remains unknown hitherto. The discovery of Spinograna indicates that the ecosystem in the Middle Cretaceous is much more complicated than previously thought, and some of the ecological ties between plants and animals that existed then have gone out forever.

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