How will freshwater lakes in the Arctic respond to climate change, especially if polar amplification results in even greater warming at these northern latitudes? Deep time analogs offer opportunities to understand the potential effects of future climate warming on arctic environments. A core from the Giraffe Pipe fossil locality located in the Northwest Territories of Canada offers a window into the life of a thriving Arctic freshwater ecosystem in the Eocene during greenhouse conditions. The remains of an extensive deposit of microfossils, including photosynthetic protists (chrysophytes, diatoms, and green algae), heterotrophic protists (euglyphids, heliozoans, paraphysomonads, and rotosphaerids), and sponges, were used to reconstruct the history of the ancient waterbody. Concentrations and diversity of chrysophyte taxa were extensive throughout the core, accounting for >70% of the microfossil remains. The ratio of chrysophyte cysts to diatom valves, with a mean value near 14 throughout the core, further emphasized the dominance of the chrysophytes, and given the high diversity of taxa, the locality represents a “paleo-hotspot” for this eukaryote lineage. Based on the totality of fossil evidence, the waterbody within the Giraffe Pipe crater represented a series of relatively shallow aquatic habitats, with changing physical and chemical conditions, and varying water depths. Five major zones were identified, each found to be stable for an extended period of time, but with distinct transitions between successive zones signaling significant shifts in environmental conditions. The study provides valuable insight on how Arctic freshwater ecosystems responded to past warm climates, and to the organisms that could potentially thrive in these environments under future warming scenarios.

The morphology of Zygospira, an early atrypide brachiopod, was analyzed using a multivariate approach. Principal component analysis and discriminant analysis clearly differentiated species as they are currently defined primarily based on differences in shell size and ornamentation but not in terms of overall shell shape. The older Zygospira modesta was able to persist into the late Katian (Richmondian) while smaller early species in other brachiopod lineages mostly went extinct. This may have been possible through niche partitioning because the smaller shells have been found attached to other filter feeders and no larger species have been found in these associations so far. This could represent a rare example of sympatric speciation preserved in the fossil record. In the future, detailed study of the spiralia and their associated structures may provide clues as to the ultimate evolutionary affinities of this group in relation to the other atrypide brachiopods evolving at this time.

This study provides the first focused investigation of rudist bivalves from the Upper Cretaceous of the Gulf Coastal Plain (GCP) in the southern US and previously undescribed specimens from the Flor de Alba Limestone Member of the Pozas Formation in Puerto Rico. Identified rudists from the GCP comprise the Monopleuridae, including Gyropleura, as well as Radiolitidae, including Biradiolites cardenasensi, Durania maxima, Guanacastea jamaicensis, Radiolites acutocostata, and Sauvagesia. Integrating rudist occurrences within well-established GCP biostratigraphy allows for extension of upper ranges of D. maxima and R. acutocostata into the late Campanian, and extension of the lower ranges of B. cardenasensis and G. jamaicensis into the early Campanian. Identified rudists from Puerto Rico comprise the Hippuritidae and include Barrettia monilifera, which supports the age of the Flor de Alba Limestone Member of the Pozas Formation as middle Campanian. Combined taxonomic, biostratigraphic, and paleobiogeographic analyses indicate there is no rudist fauna endemic to the GCP, and the region marks the northeastern range of the Caribbean genera Biradiolites, Durania, Guanacastea, Gyropleura, Radiolites, and Sauvagesia during the Campanian and Maastrichtian. The new occurrences help inform future updates of Late Cretaceous sea surface-current reconstructions for the Caribbean and Western Interior Seaway, USA.

A diverse molluscan assemblage dominated by turritellid gastropods found in Kachchh, western India, has been interpreted in the past as Late Jurassic (Oxfordian) in age, based on associated undoubtedly Oxfordian ammonites. Recently, several investigations focused on the assemblage dealing with taxonomic, paleoecological, and evolutionary aspects. An analysis of the associated bivalve fauna, foraminiferal assemblage, and the geological context strongly suggests a Miocene rather than a Jurassic age and invalidates several conclusions drawn from the alleged Jurassic age of the fossils.

The type specimens of Eothinoceras americanum Ulrich et al., 1944, type species of the genus Eothinoceras Ulrich et al., 1944, are revised based on new photographic material. The resulting interpretation of the conch shape of Eothinoceras shows that the type species is an endogastric cyrtocone, necessitating the restriction of Eothinoceras to the type species and requiring the revision of the family Eothinoceratidae and the order Cyrtocerinida. A new scheme for classifying the genera of the order Cyrtocerinida into its three families is proposed: (1) Eothinoceratidae Ulrich et al., 1944, containing the genera Eothinoceras; Protothinoceras Chen and Teichert, 1987; Mesothinoceras Chen and Teichert, 1987; and Conothinoceras Chen and Teichert, 1987; (2) Cyrtocerinidae Flower, 1946, including Cyrtocerina Billings, 1865; Tangshanoceras Chen, 1976; and Centrocyrtocerina Stait, 1983; (3) Bathmoceratidae Gill, 1871, containing Bathmoceras Barrande, 1865; Saloceras Evans, 2005; Sacerdosoceras Evans, 2005; Margaritoceras Cecioni and Flower, 1985; and Mutveiceras Cichowolski et al., 2014.

The trilobite Needmorella new genus, with type species N. simoni new genus new species from the late Emsian to mid-Eifelian Needmore Shale of West Virginia, is a distinctive member of the subfamily Synphoriinae. It also occurs in the same formation in Pennsylvania and Virginia. It is not very similar to other Devonian representatives of the subfamily and is considered to have its origins in a morphologically less-derived ancestor because it shares certain similarities with Silurian genera, including the very short anterior cephalic border unmodified by crenulations or spines, S2 that is not largely reduced to a deep pit adaxially, the relatively low inflation of L3, and the well-defined interpleural furrows on the pygidium. Other particularly distinctive characters of the genus include the very long genal spines and the abaxially inflated and expanded posterior pleural bands on the thorax and pygidium that project slightly distally. The conventional concept of the Devonian synphoriine Anchiopsis Delo, 1935 appears to be incompatible with the holotype of the type species, judging from the early illustrations of the specimen, and the genus could be a synonym of Synphoria Clarke, 1894.

The first fossil Typhlocybinae inclusions from Eocene Rovno amber are described and illustrated. They include two new monotypic genera of the extinct tribe Protodikraneurini, Retrorsotettix n. gen. with type species R. vlaskini n. sp. and Protoparallaxis n. gen. with type species P. clavatus n. sp. Also described and illustrated are two new monotypic genera of the extant tribe Dikraneurini, Eodikraneura n. gen. with type species E. obscura n. sp. and Rovnodikra n. gen. with type species Rovnodikra longipes n. sp. Retrorsotettix is the oldest leafhopper known to exhibit a false eyespot and false leg markings on the forewing, representing an early acquisition of a defensive strategy against visual predators. Appearance of a small insect with false eyespots in the Eocene fossil record may reflect increased pressure by visual predators, especially crown ornithuromorph insectivorous birds. Such birds and small insect prey with false eyespots remain unknown in the Cretaceous. Eodikraneura exhibits a unique condition of the hind wing venation in which radius posterior and media anterior veins are confluent for a short distance but then diverge before separately reaching the submarginal vein. This presumably represents a morphological transition between the Protodikraneurini, in which hind-wing radius posterior and media anterior veins are completely separate and connected by a radial-medial crossvein, and Dikraneurini, in which radius posterior and media anterior veins are completely confluent distally. A key to genera of Protodikraneurini is provided.

Zygocycloides? foerstei n. sp. is described from the Llandovery (Aeronian) Brassfield Formation of southwestern Ohio. This is among the oldest reported Silurian cyclocystoids from North America and is the only North American Llandovery cyclocystoid that is preserved with a complete rim of marginal ossicles. Zygocycloides Smith and Paul, 1982 is most similar to Nicholsodiscus Glass et al., 2003 (Katian) and Perforocycloides Ewin et al., 2019 (Llandovery, Telychian), both from Anticosti Island, Québec. Cyclocystoids (Ordovician to Mississippian) survived Late Ordovician extinctions, and this discovery documents that this echinoderm clade was part of shallow-water, marine paleocommunities during the initial post-extinction transgression onto the Laurentian platform.

Goryeocrinus pentagrammos n. gen. n. sp. from the Jigunsan Formation of South Korea is described and is the first diplobathrid recorded from Middle Ordovician (middle Darriwilian) strata of East Gondwana. Phylogenetic analyses suggest that G. pentagrammos n. gen. n. sp. is a member of the paraphyletic Rhodocrinitidae of the Diplobathrida and most closely related to Paradiabolocrinus from the Late Ordovician (Sandbian) of Laurentia. Goryeocrinus pentagrammos n. gen. n. sp. is characterized by having a pentameral, flat bowl-shaped calyx, a conspicuous pentagrammatic ridge formed by bifurcated median ray ridge and pentagonal basal ridge, at least two interradials in the first row of regular interrays, an anitaxial ridge originating from the CD interray but close to the C ray radial, and lacking intrabrachials and interradials between secundibrachials. The occurrence of G. pentagrammos n. gen. n. sp. from South Korea (East Gondwana) drastically expands the Ordovician paleogeographic range of camerates, which otherwise have been recorded from Laurentia, West Gondwana, Avalonia, and Baltica.

Graptolites from the latest Ordovician to the earliest Silurian rocks of northwest Peninsular Malaysia are described and reviewed. The fossils were collected previously by C. R. Jones and presently by the authors inside the black mudstones from the basal section of Tanjung Dendang Formation in Pulau Langgun, Langkawi, which comprises assemblages from the Hirnantian Metabolograptus extraordinarius Biozone to the Rhuddanian Akidograptus ascensus–Parakidograptus acuminatus Biozone. The latest Ordovician strata also include a Hirnantia fauna bed between the Metabolograptus extraordinarius and Metabolograptus persculptus biozones, in which shelly fossils such as Mucronaspis sp. could be recovered. A revised graptolite biozonation is proposed for the latest Ordovician to the earliest Silurian succession of northwest Peninsular Malaysia. This interval is significant for understanding the extent of mass extinction events happening right at the end of the Ordovician period and subsequent faunal change in the region.

The Lochkovian, Pragian, and basal part of the Emsian, which represent the post-Kwangsian Orogeny strata in the South China Block, are mainly composed of siliciclastic rocks. This lithological composition impedes investigation of Pragian and Lochkovian conodont biostratigraphy in the South China Block, which results in a persistent controversy on the age of relevant lithological units. The present study provides new evidence by reporting for the first time Lochkovian conodonts obtained from the South China Block, specifically the Gaoling Member of the Nahkaoling Formation at the Lingli section, central Guangxi. The conodont fauna, consisting of Pandorinellina exigua lingliensis Lu n. subsp., Pandorinellina exigua exigua, Zieglerodina? tuojiangensis Lu n. sp., Amydrotaxis praejohnsoni, and Eognathodus cf. E. irregularis, places the studied interval of the Gaoling Member in the lower or middle Lochkovian (contingent upon varying definitions for the base of the middle Lochkovian) to lower Pragian. Moreover, Amydrotaxis praejohnsoni, which was reported previously only in North America and eastern Australia, is herein also recorded in the South China Block, and thus may play an important role in intercontinental biostratigraphical correlation. By shedding light on the age of the upper limit of the underlying Lianhuashan Formation at the Lingli section, the present study indicates that the Kwangsian Orogeny ended before the late Lochkovian. This date is slightly earlier than the previously estimated late Lochkovian based on studies of fossil plants from the siliciclastic rocks deposited after the Kwangsian Orogeny.

Recent fossil discoveries from New Zealand have revealed a remarkably diverse assemblage of Paleocene stem group penguins. Here, we add to this growing record by describing nine new penguin specimens from the late Paleocene (upper Teurian local stage; 55.5–59.5 Ma) Moeraki Formation of the South Island, New Zealand. The largest specimen is assigned to a new species, Kumimanu fordycei n. sp., which may have been the largest penguin ever to have lived. Allometric regressions based on humerus length and humerus proximal width of extant penguins yield mean estimates of a live body mass in the range of 148.0 kg (95% CI: 132.5 kg–165.3 kg) and 159.7 kg (95% CI: 142.6 kg–178.8 kg), respectively, for Kumimanu fordycei. A second new species, Petradyptes stonehousei n. gen. n. sp., is represented by five specimens and was slightly larger than the extant emperor penguin Aptenodytes forsteri. Two small humeri represent an additional smaller unnamed penguin species. Parsimony and Bayesian phylogenetic analyses recover Kumimanu and Petradyptes crownward of the early Paleocene mainland NZ taxa Waimanu and Muriwaimanu, but stemward of the Chatham Island taxon Kupoupou. These analyses differ, however, in the placement of these two taxa relative to Sequiwaimanu, Crossvallia, and Kaiika. The massive size and placement of Kumimanu fordycei close to the root of the penguin tree provide additional support for a scenario in which penguins reached the upper limit of sphenisciform body size very early in their evolutionary history, while still retaining numerous plesiomorphic features of the flipper.

The study of the cranial endocast provides valuable information to understand the behavior of an organism because it coordinates sensory information and motor functions. In this work, we describe for the first time the anatomy of the encephalon of an early Miocene pan-octodontoid caviomorph rodent (Prospaniomys priscus Ameghino, 1902) found in the Argentinean Patagonia, based on a virtual 3D endocast. This fossil rodent has an endocast morphology here considered ancestral for Pan-Octodontoidea and other South American caviomorph lineages, i.e., an encephalon with anteroposteriorly aligned elements, mesencephalon dorsally exposed, well-developed vermis of the cerebellum, and rhombic cerebral hemispheres with well-developed temporal lobes. Prospaniomys Ameghino, 1902 also has relatively small olfactory bulbs, large paraflocculi of the cerebellum, and low endocranial volume and degree of neocorticalization. Its encephalization quotient is low compared with Paleogene North American and European noncaviomorph rodents, but slightly higher than in several late early and late Miocene caviomorphs. Paleoneurological anatomical information supports the hypothesis that Prospaniomys was a generalist caviomorph rodent with terrestrial habits and enhanced low-frequency auditory specializations. The scarce paleoneurological information indicates that several endocast characters in caviomorph rodents could change with ecological pressures. This work sheds light on the anatomy and evolution of several paleoneurological aspects of this particular group of South American rodents.

Paromomyidae are one of several families of plesiadapiforms that flourished during the Paleocene in North America soon after the extinction of non-avian dinosaurs some 66 million years ago. Although they are often among the best-represented plesiadapiforms in mammalian faunas in both North America and Europe, the early history of paromomyids is poorly understood, and their fossil record at higher latitudes is comparatively depauperate. We report here on the discovery of two new species of paromomyids from Paleocene deposits in southwestern Alberta: Edworthia greggi new species is the second known species of the basal paromomyid Edworthia Fox, Scott, and Rankin, 2010 whereas Ignacius glenbowensis new species is among the most abundantly represented species of Ignacius Matthew and Granger, 1921. These new discoveries document, for the first time, parts of the upper dentition of Edworthia, and the new species of Ignacius represents the first new, pre-Clarkforkian species of the genus to be described in nearly 100 years. A comprehensive phylogenetic analysis of nearly all known paromomyid taxa (including the new species described herein) recovered both species of Edworthia near the base of the paromomyid tree in a polytomy with Paromomys depressidens Gidley, 1923 and a paraphyletic Ignacius. The new paromomyids from Alberta not only increase the known taxonomic diversity of Edworthia and Ignacius but also add significantly to knowledge of the dental anatomy of these poorly known genera and further add to a uniquely Canadian complement of Paleocene plesiadapiforms.

Proterozoic eukaryotic macroalgae are difficult to interpret because morphological details required for proper phylogenetic studies are rarely preserved. This is especially true of morphologically simple organisms consisting of tubes, ribbons, or spheres that are commonly found in a wide array of bacteria, plants, and even animals. Previous reports of exceptionally preserved Tonian (ca. 950–900 Ma) fossils from the Dolores Creek Formation of Northwestern Canada feature enough morphological evidence to support a green macroalgal affinity. However, the affinities of two additional forms identified on the basis of the size distribution of available specimens remain undetermined, while the presence of three unique algal forms supports other reports of increasing algal diversity in the early Neoproterozoic. Archaeochaeta guncho new genus new species is described as a green macroalga on the basis of its well-preserved morphology consisting of an unbranching, uniseriate thallus with uniform width throughout and possessing an elliptical to globose anchoring holdfast. A larger size class of ribbon-like forms is interpreted as Vendotaenia sp. A third size class is significantly smaller than Archaeochaeta n. gen. and Vendotaenia, but in the absence of clear morphological characters, it remains difficult to assign. As Archaeochaeta n. gen. and Vendotaenia represent photoautotrophic taxa, these findings support the hypothesis of increasing morphological complexity and phyletic diversification of macroalgae during the Tonian, leading to dramatic changes within benthic marine ecosystems before the evolution of animals.

Specimens of macroalgae are reported and described herein from newly discovered algal-Lagerstätten within the Llandoverian Earlton Formation at two localities separated by a distance of 45 km in the Timiskaming outlier of Ontario, Canada. Both localities are characterized by abundant specimens of the Codium-like bryopsidalean green alga Thalassocystis striata, the details of which, including within-assemblage morphological variation, compare closely to material from the type locality. Previously, this noncalcified taxon was known only from the Llandoverian Schoolcraft Formation in northern Michigan, ∼500 km to the west. These new occurrences provide additional evidence that the alga-bearing intervals within the Earlton Formation at both Timiskaming localities correlate with the Schoolcraft Formation in the Michigan Basin. An associated noncalcified form at one of the Timiskaming localities is described as a new genus and species, Earltonella fredricksi LoDuca, n. gen. n. sp., the thallus architecture of which, with a creeping, runner-like stolon and numerous pinnate fronds, broadly resembles that of the living bryopsidalean alga Caulerpa. In broader terms, these new algal-Lagerstätten indicate that for a brief time during the late Llandoverian, as with other times during the Silurian, unusual conditions conducive to both the proliferation and preservation of expansive ‘seaweed meadows’ were established across regional-scale areas of the Laurentian epeiric sea.