Arnebolagus leporinus Lopatin and Averianov, 2008, known previously from a single tooth (P3) from the early Eocene Bumban Member of Naran Bulak Formation at Tsagan-Khushu locality in Mongolia, is redescribed based on additional specimens from the type locality. Phylogenetic relationships of Eocene stem lagomorphs from Asia and North America are reconstructed for the first time based on a parsimony analysis of 54 morphological characters and 32 taxa. Two new node-based clades are proposed, stemming from the most-recent common ancestor of Lepus Linnaeus, 1758 and Dawsonolagus Li, Meng, and Wang, 2007 (Eulagomorpha new clade, ‘lagomorphs of the modern aspect’) and from the most-recent common ancestor of Lepus and Gobiolagus Burke, 1941 (Epilagomorpha new clade). Arnebolagus Lopatin and Averianov, 2008 is geologically oldest and the most plesiomorphic eulagomorph, similar to Dawsonolagus from the early Eocene Arshanto Formation of China in its weakly pronounced, unilateral hypsodonty of the upper cheek teeth and its brachyodont lower cheek teeth with separate roots. Arnebolagus is more plesiomorphic than Dawsonolagus in having two roots of P4. Arnebolagus is the oldest known eulagomorph, the only taxon known from the earliest Eocene Bumbanian Asiatic Land Mammal Age (ALMA). The other Asiatic early Eocene eulagomorphs (Dawsonolagus, Aktashmys Averianov, 1994, and Romanolagus Shevyreva, 1995) come from the Arshantan ALMA.

A new crocodylian, Dongnanosuchus hsui n. gen. n. sp., is described mainly based on four well-preserved skulls from the Eocene Youganwo Formation of the Maoming Basin, southeastern China. It is an alligatoroid and phylogenetically nested within the Orientalosuchina. Dongnanosuchus hsui n. gen. n. sp. differs from all other orientalosuchines primarily in certain features of the skull: (1) a preorbital ridge connects posteriorly with the dorsal orbital rim and a ridge around the anteroventral margin of the orbit, (2) the palatine is short and does not reach the posterior border of the suborbital fenestra, (3) the external mandibular fenestra is closed, and (4) the splenial joins the formation of the mandibular symphysis. The discovery of Dongnanosuchus hsui n. gen. n. sp. confirms the monophyly and North American origin of the Orientalosuchina but suggests that the clade dispersed to Asia via Beringia after diverging from the mainline rather than a sub-lineage of the Alligatoroidea in the Late Cretaceous.

UUID: http://zoobank.org/f8ca22f1-6323-462e-bf32-03c6a164c82e.

Five marsupial species are recognized from the Brule Formation at two localities in southwestern North Dakota: Fitterer Ranch and Obritsch Ranch (middle Oligocene; Whitneyan North American Land Mammal Age [NALMA]). The herpetotheriids Herpetotherium fugax Cope, 1873a, Copedelphys superstes new species, and the peradectid Nanodelphys hunti (Cope, 1873b) are represented at both localities. A fourth species is H. sp., cf. H. merriami (Stock and Furlong, 1922), represented by a single specimen from Fitterer Ranch, being limited elsewhere to the later Arikareean NALMA. A fifth species is represented by two isolated lower cheek teeth, interpreted as m1s, from Fitterer Ranch that are unique in lacking a trigonid (only two cusps present) while having a well-developed talonid. These specimens are referred to an indeterminate herpetotheriine species. The new species of Copedelphys is distinct from other species of the genus in that the anterior two lower molars are enlarged relative to the posterior molars. Overall, this new species is more similar in proportions to the latest Eocene (Chadronian) C. titanelix (Matthew, 1903) than the Oligocene (Orellan and Whitneyan) C. stevensoni (Cope, 1873b). This study adds a third and fourth Whitneyan marsupial fauna from the Great Plains region of North America, increases the known diversity of Whitneyan marsupials, and provides further evidence that marsupial diversity during the late Paleogene in North America was relatively stable until the late early Arikareean NALMA.

UUID: http://zoobank.org/b8534802-b9ed-4120-baca-fc72917f7d6a

A revision of the rhinocerotid material from the Negev (Israel), dating back to the early Miocene (MN3 in the European Mammal Biochronology), highlights the presence of Brachypotherium and a taxon close to Gaindatherium in the Levantine corridor. A juvenile mandible, investigated using CT scanning, displays morphologically distinct characters consistent with Brachypotherium cf. B. snowi rather than with other Eurasian representatives of this genus. Some postcranial remains from the Negev, such as a humerus, display features that distinguish it among Miocene taxa. We attribute these postcrania to cf. Gaindatherium sp., a taxon never recorded outside the Siwaliks until now. This taxon dispersed into the Levantine region during the late early Miocene, following a pattern similar to other South Asian taxa. Brachypotherium cf. B. snowi probably occurred in the Levantine region and then in North Africa during the early Miocene because its remains are known from slightly younger localities such as Moghara (Egypt) and Jebel Zelten (Libya). The occurrence cf. Gaindatherium sp. represents a previously unrecorded range expansion out of Southeast Asia. These new records demonstrate the paleogeographic importance of the Levantine region showcasing the complex role of the Levantine corridor in intercontinental dispersals between Asia and Europe as well as Eurasia and Africa.

The horseshoe crab Limulus polyphemus (Linnaeus, 1758) is a famous species, renowned as a ‘living fossil’ (Owen, 1873; Barthel, 1974; Kin and Błażejowski, 2014) for its apparently little-changed morphology for many millions of years. The genus Limulus Müller, 1785 was used by Leach (1819, p. 536) as the basis of a new family Limulidae and synonymized it with Polyphemus Lamarck, 1801 (Lamarck's proposed but later unaccepted replacement for Limulus, as discussed by Van der Hoeven, 1838, p. 8) and Xyphotheca Gronovius, 1764 (later changed to Xiphosura Gronovius, 1764, another junior synonym of Limulus). He also included the valid modern genus Tachypleus Leach, 1819 in the family. The primary authority of Leach (1819) is widely recognized in the neontological literature (e.g., Dunlop et al., 2012; Smith et al., 2017). It is also the authority recognized in the World Register of Marine Species (WoRMS Editorial Board, 2021).

We undertake a redescription of the equid sample from the Early Pleistocene of Roca-Neyra, France. This locality has been recently calibrated at the Pliocene/Pleistocene boundary (2.6 ± 0.2 Ma) and therefore it is of interest for the first appearance of the genus Equus and last appearance of hipparionine horses. The Roca-Neyra equid sample, re-analyzed herein using morphological, morphometrical, and statistical analyses, has revealed the co-occurrence of Plesiohipparion cf. ?P. rocinantis and Equus cf. E. livenzovensis. The analysis undertaken on several European, African, and Asian “Hipparion” sensu lato species from late Miocene to Early Pleistocene has revealed different remnant Hipparion lineages in the Plio-Pleistocene of Europe: Plesiohipparion, Proboscidippaion, and likely Cremohipparion. The discovery of the first European monodactyl horse, Equus cf. E. livenzovensis correlates Roca-Neyra with other 2.6 Ma European localities in Italy, Spain, and in the Khapry area (Azov Sea region). The morphological description of the Equus cf. E. livenzovensis lower cheek teeth has highlighted intermediate features between the North American Pliocene species Equus simplicidens and Early Pleistocene European Equus stenonis. Our study supports the hypothesis that E. livenzovensis is a plausible evolutionary predecessor for the Equus stenonis group. These observations underscore the importance of Roca-Neyra as an important locality for the last European hipparions and the first Equus in the Early Pleistocene of Europe.

In the first half of the nineteenth century, a marked shift occurred in our understanding and treatment of the chelicerate fossil record, with the differentiation and recognition of entirely extinct genera for the first time. At the heart of this taxonomic revolution were the Eurypterida (sea scorpions) and Xiphosura (horseshoe crabs), although both groups were in fact considered crustaceans until Lankester's (1881) seminal comparative anatomical study of the extant xiphosuran Limulus Müller, 1785 and modern scorpions. The oldest available eurypterid genus is Eurypterus deKay, 1825; the oldest available fossil arachnid genus name is that of the scorpion Cyclophthalmus Corda, 1835. However, there has been considerable historical confusion over the oldest available fossil xiphosuran genus name, which has been recognized alternately as Belinurus König (with a publication date of either 1820 or 1851) or the synonymous Bellinurus Pictet, 1846. Most recent treatments (e.g., Selden and Siveter, 1987; Anderson and Selden, 1997; Anderson et al., 1997; Lamsdell, 2016, 2021; Bicknell and Pates, 2020) have favored Bellinurus Pictet, 1846 as the available name; however, Haug and Haug (2020) recently argued that Belinurus König, 1820 is valid and has priority, a position then followed by Lamsdell (2020), prompting a reinvestigation of the taxonomic history of the genus. Upon review, it is clear that neither of the previously recognized authorities for Belinurus are accurate and that the two candidate type species for each genus are, in fact, synonyms. Given the convoluted and at times almost illogical history of the competing names, along with the most recent controversy as to which has priority, we present a complete history of the treatment of the genus to resolve the issue.