The Mesoproterozoic is an important era for the development of eukaryotic organisms in oceans. The earliest unambiguous eukaryotic microfossils are reported in late Paleoproterozoic shales from China and Australia. During the Mesoproterozoic, eukaryotes diversified in taxonomy, metabolism, and ecology, with the advent of eukaryotic photosynthesis, osmotrophy, multicellularity, and predation. Despite these biological innovations, their fossil record is scarce before the late Mesoproterozoic. Here, we document an assemblage of organic-walled microfossils from the 1590–1270 Ma Dismal Lakes Group in Canada. The assemblage comprises 25 taxa, including 11 morphospecies identified as eukaryotes, a relatively high diversity for this period. We also report one new species, Dictyosphaera smaugi new species, and one unnamed taxon. The diversity of eukaryotic forms in this succession is comparable to slightly older assemblages from China and is higher than worldwide contemporaneous assemblages and supports the hypothesis of an earlier diversification of eukaryotes in the Mesoproterozoic.

The Cretaceous chaetetid sponge Acanthochaetetes huauclillensis Sánchez-Beristain and García-Barrera is reported for the first time from the Aptian–Cenomanian Khalsi Formation, Ladakh Himalaya, India. Its low- to high-domical growth form could suggest an adaptation to either an environment with constant sedimentation rates, or to an irregular substrate. However, these growth forms also may indicate an absence of important environmental/sedimentological changes during the lifespan of the sponges. In addition, the growth form of this species suggests a calm, non-turbulent, reef-like microenvironment. Along with the other faunal assemblages, such as the rudists, corals, and the gastropod Nerinea, A. huauclillensis indicates a tropical to subtropical shallow marine carbonate platform setting. This new finding extends its stratigraphic range from the upper Hauterivian to the Aptian–Cenomanian interval in the eastern Tethyan realm.

Type material for Stenopora tasmaniensis Lonsdale, 1844 was lost in the late nineteenth century, and subsequent descriptions of the genus have been based on material incorrectly assigned to the type species. A neotype is erected for S. tasmaniensis from the original type locality and the genus redescribed. The genus exhibits ramose, frondescent, encrusting, and massive colony morphologies, diaphragms are absent, and acanthostyles of a single size surround each aperture. This single size of acanthostyles aligns with the original type species description; however, it differs from the subsequently accepted genus description and may result in existing species being removed from the genus. Analysis of zooecial characters of a single colony exhibiting both frondescent and ramose morphologies reveals statistically significant differences between subsampled sections, despite being from the same colony. Differences relate to details of zooecial parameters and are not controlled by colony morphology. This variation within a single colony confirms the importance of using qualitative characters alongside quantitative measures in defining Paleozoic bryozoan species.

The tectonic evolution of the Sibumasu Block during the Permian remains controversial, and Permian faunas and their paleobiogeographic affinities provide some insight into its paleogeographic and tectonic evolutionary histories. In this paper, a new brachiopod fauna dominated by Spinomartinia prolifica Waterhouse, 1981 is described from the uppermost part of the Taungnyo Group in the Zwekabin Range, eastern Myanmar. This brachiopod fauna includes 23 species and its age is well constrained as late Kungurian by the associated conodonts, i.e., Vjalovognathus nicolli Yuan et al., 2016 and Mesogondolella idahoensis (Youngquist, Hawley, and Miller, 1951), contrary to the late Sakmarian age given to the same brachiopod faunas previously reported from southern Thailand and Malaysia. Based on comprehensive comparisons of the Cisuralian brachiopod faunas and other data in different parts of the Sibumasu Block, we consider that they are better subdivided into two independent stratigraphic assemblages, i.e., the lower (earlier) Bandoproductus monticulus-Spirelytha petaliformis Assemblage of a Sakmarian to probably early Artinskian age, and the upper (younger) Spinomartinia prolifica-Retimarginifera alata Assemblage of a late Kungurian age. The former assemblage is a typical cold-water fauna, mainly composed of Gondwanan-type genera, e.g., Bandoproductus Jin and Sun, 1981, Spirelytha Fredericks, 1924, and Sulciplica Waterhouse, 1968. The latter assemblage is strongly characterized by an admixture of both Cathaysian and Gondwanan elements, as well as some genera restricted to the Cimmerian continents. Notably, the spatial distribution pattern of these two separate brachiopod assemblages varies distinctly. The Sakmarian cold-water brachiopod faunas have been found in association with glacial-marine diamictites throughout the Sibumasu Block including both the Irrawaddy and Sibuma blocks. In contrast, the Kungurian biogeographically mixed brachiopod faunas are only recorded in the Irrawaddy Block, unlike the Sibuma Block that contains a contemporaneous paleotropical Tethyan fusuline fauna. Thus, it appears likely that by the end of Cisuralian (early Permian), the Sibumasu Block comprised the Irrawaddy Block in the south with cool climatic conditions, and the Sibuma Block in the north with a temperate to warm-water environment, separated by the incipient Thai-Myanmar Mesotethys.

The end-Ordovician mass extinction, linked to a major glaciation, led to deep changes in Hirnantian–Rhuddanian biotas. The Hirnantia Fauna, the first of two Hirnantian survival brachiopod-dominated communities, characterizes the lower–mid Hirnantian deposits globally, and its distribution is essential to understand how the extinction took place. In this paper, we describe, illustrate, and discuss the first macrofossiliferous Hirnantia Fauna assemblage from Belgium, occurring in the Tihange Member of the Fosses Formation at Tihange (Huy), within the Central Condroz Inlier. Six fossiliferous beds have yielded a low-diversity, brachiopod-dominated association. In addition to the brachiopods (Eostropheodonta hirnantensis, Plectothyrella crassicosta, Hirnantia sp., and Trucizetina? sp.), one trilobite (Mucronaspis sp.), four pelmatozoans (Xenocrinus sp., Cyclocharax [col.] paucicrenulatus, Conspectocrinus [col.] celticus, and Pentagonocyclicus [col.] sp.), three graptolites (Cystograptus ancestralis, Normalograptus normalis, and ?Metabolograptus sp.), together with indeterminate machaeridians and bryozoans were identified. The graptolite assemblage, from the Akidograptus ascensus-Parakidograptus acuminatus Biozone, indicates an early Rhuddanian (Silurian) age, and thus, an unexpectedly late occurrence of a typical Hirnantia Fauna. This Belgian association may represent an additional example of relict Hirnantia Fauna in the Silurian, sharing characteristics with the only other known from Rhuddanian rocks at Yewdale Beck (Lake District, England), although reworking has not been completely ruled out. The survival of these Hirnantian taxa into the Silurian might be linked to delayed post-glacial effects of rising temperature and sea-level, which may have favored the establishment of refugia in these two particular regions that were paleogeographically close during the Late Ordovician–early Silurian.

Protandrous sex change (sex change from male to female) is one of the diverse sexual expressions exhibited by bivalves, but its expression in the shell is quite rare. Previous studies on living and fossil astartids suggest a relationship between protandrous sex change and the formation of crenulations on the ventral shell margin at later ontogenetic stages. Here we report the formation of such crenulations in the Early Jurassic astartid Nicaniella rakoveci (Kuhn, 1935) from the Amaltheenton Formation at Buttenheim, Franconia. This is the earliest known record of protandrous hermaphroditism in fossil bivalves, predating previous reports by at least 13 Myr. A principal component analysis of linear size measurements and Fourier shape analysis of the shell outlines revealed that the outline of Nicaniella rakoveci specimens varies from subquadrate to subcircular, but this variation is independent of the presence or absence of crenulations and therefore not associated with sex. Crenulated specimens exhibit a lower height/inflation ratio than non-crenulated ones, suggesting that the protandrous females have more inflated valves than the males. The formation of crenulations was probably related to allocation of resources for reproduction. The most likely function of the crenulations was to increase the internal shell volume in the female stage to accommodate more eggs rather than being an adaptation against predation as often assumed for other bivalves. The formation of crenulations is part of the protandrous life history and probably is controlled by a genetic mechanism that is also responsible for sex change.

Olenellid trilobites from the lower Cambrian of the Iberian Peninsula are very scarce and poorly studied, making them difficult to compare with defined species and to include in biostratigraphic and paleobiogeographic analyses. Based on newly collected specimens, we revise the species ‘Callavia? lotzei’ Richter and Richter, 1941 from the ‘Cumbres beds’ of Cumbres de San Bartolomé and the ‘Herrerías shale’ of Cañaveral de León, Sierra del Bujo, and Hinojales (Huelva, Spain), and ‘Paradoxides choffati’ Delgado, 1904 from the Vila Boim Formation of Elvas (Portugal). The new material indicates that Callavia? lotzei is a junior synonym of ‘P. choffati.’ The Iberian species are here assigned to Callavia Matthew, 1897, for which morphological characters are reassessed, offering a valuable opportunity to discuss characters previously misinterpreted for this genus. Traditionally assigned to the Olenelloidea Walcott, 1890, Callavia lacks some of the diagnostic characters of this superfamily and is here assigned to Judomioidea Repina, 1979. A new diagnosis for this genus is provided, and Sdzuyomia Lieberman, 2001 is considered to represent a junior synonym of Callavia. The genus Callavia is distributed across the western margin of Gondwana, from the western Mediterranean region (Iberia and Morocco) throughout all the Avalonia sectors (UK, eastern Newfoundland, and Massachusetts). Its presence in Iberia supports the faunal links between the West Gondwana domain and Avalonia during Cambrian Series 2. The Iberian records of Callavia choffati are assigned to the middle part of the regional Marianian Stage (uppermost Cambrian Stage 3 to the lowermost Cambrian Stage 4) and correlates with the Callavia Biozone of Avalonia (lower Branchian Series).

Most Cambrian Series 2 faunas of Laurentia are dominated by olenelline trilobites; however, non-olenelline trilobites occur with the olenellines and sometimes dominate the assemblages. Reported here are such non-olenelline trilobites from the Harkless Formation and Mule Spring Limestone at Clayton Ridge, Nevada. At the bottom of the Saline Valley Tongue, Harkless Formation, are two assemblages that are characterized by corynexochines and/or ptychoparioids, with olenellines occurring as only rare components. The corynexochines present in these assemblages include Bonnia cf. B. brennus (Walcott, 1916), Ovatoryctocara cf. O. yaxiensis Yuan et al., 2009, Protoryctocephalus? aff. P.? arcticus Geyer and Peel, 2011, Ogygopsis sp. indet., and Oryctocephalops frischenfeldi Lermontova, 1940. These assemblages are from the mid-Dyeran Stage, below the lowermost zone in the upper Dyeran (Arcuolenellus arcuatus Biozone), and can be correlated to Series 2 Stage 4 (Cambrian) assemblages in Greenland, Siberia, and South China based on the corynexochines.

Also in the Saline Valley Tongue and the overlying Mule Spring Limestone and lowermost Emigrant Formation are olenelloid-dominated assemblages that contain the corynexochines Bonnia columbensis Resser, 1936, Zacanthopsis aff. Z. levis (Walcott, 1886), and Z. sp. indet.

New parasitoid wasps of the family Braconidae are documented from Eocene Baltic and Rovno ambers. A new fossil genus belonging to the braconid subfamily Exothecinae, Palaeocolastes n. gen., with its type species P. bruesi n. sp., is described and illustrated from Baltic amber. This represents the first reliable fossil record for a member of Exothecinae. Two additional new species from Baltic amber are also described: Ascogaster (Syntaphus) latitibialis n. sp. (Cheloninae) and Meteorus arasnitsyni n. sp. (Euphorinae). Another fossil species, Microtypus eocenus n. sp. (Microtypinae), is described from coeval Rovno amber (Ukraine), representing the first braconid species described from this deposit. A new record of a female of Diospilites brevicornis Brues, 1933 (Diospilitinae) from Baltic amber, together with variation of some diagnostic features of the species and redescription of its subfamily and genus, are also provided.

UUID: http://zoobank.org/656cb1a3-b9cf-4696-ae24-0d4df9545101.

The youngest species of Amphoracrinus, A. tenax new species, is described from the Muldraugh Member of the Borden Formation (early Viséan) of north-central Kentucky. With this new occurrence, both the oldest and youngest named species of Amphoracrinus are from North America. Numerous Tournaisian and Viséan crinoid faunas are documented in the United States, but only four are known to contain Amphoracrinus. Morphological analysis indicates that A. tenax is more closely aligned with species from China than with species from Western Europe or other species from North America, where Amphoracrinus was most diverse and abundant, which has implications for understanding paleogeographic dispersal. The holotype of A. tenax was partially disarticulated on the seafloor before burial, and final burial occurred early during disarticulation. The relative state of disarticulation from pinnules to columnals suggests that plates bound only with ligaments disarticulated as a function of surface area of ligaments binding an articulation.

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Larvae of sea urchins, brittle stars, and allies are common, ecologically important, and diverse members of marine ecosystems in all of the world's oceans today. In contrast to modern representatives, the fossil record of echinoderm larvae is poorly known. This study reports the first ophiopluteus skeleton from Cretaceous sediments worldwide, obtained from chalky sediment of the Isle of Wolin, NW Poland. The evidence presented here, that it is possible to isolate fossil echinoderm larval skeletons from rocks, indicates a hidden diversity of such fragile fossils and thus the possibility of direct geological recording.

Polykampton recurvum n. isp. is the sixth ichnospecies of the ichnogenus Polykampton Ooster, 1869. It is a horizontal structure composed of a median cylindrical tunnel and narrow, usually back-curved lateral lobes located in alternating position. It occurs 2–3 cm below the top of single beds in the Maastrichtian–Paleocene deep-sea turbiditic marlstones of the Monte Antola Unit in the Northern Apennines. The lobes of P. recurvum n. isp. are actively filled with gray mudstone from above through the permanently open median tunnel. The trace fossil belongs to the category sequestrichnia, which is typical of oxygenated deep-sea environments characterized by seasonal or episodic supply of organic matter into a generally oligotrophic environment. P. recurvum n. isp. was produced by a “worm,” probably a polychaete, which adapted to seasonal or only episodic supply of organic matter to the deep-sea floor. The tracemaker stored the organic-rich mud in the lobes for nutrition during times of low organic matter availability on the seafloor.

UUID: http://zoobank.org/49555117-1c39-4658-8b49-3f3e2f47ba27

The late Paleozoic temnospondyl Sclerocephalus formed an aquatic top predator in various central European lakes of the late Carboniferous and early Permian. Despite hundreds of specimens spanning a wide range of sizes, knowledge of the endocranium (braincase and palatoquadrate) remained very insufficient in Sclerocephalus and other stereospondylomorphs because even large skulls had unossified endocrania. A new specimen from a stratigraphically ancient deposit at St. Wendel in southwestern Germany is recognized as representing a new taxon, S. concordiae new species, and reveals a completely ossified endocranium. The sphenethmoid was completely ossified from the basisphenoid to the anterior ethmoid region, co-ossified with the parasphenoid, and the basipterygoid joint was fully established. The pterygoid bears a slender, S-shaped epipterygoid, which formed a robust pillar lateral to the braincase. The massive stapes was firmly sutured to the parasphenoid. In the temnospondyl endocranium, character evolution involved various changes in the epipterygoid region, which evolved distinct morphologies in each of the major clades.

UUID: http://zoobank.org/5e6d2078-eacf-4467-84cf-a12efcae7c0b

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.

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.

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.