Fossil egg capsules of chimaeroids (holocephalian fishes), although rare, have been known for more than 150 years (Bessels, 1869; Meunier, 1891a) and have been found in rocks as old as Upper Triassic (Gottfried and Fordyce, 2014). Egg capsules of extant chimaeroids are spindle shaped, with a smooth central body where the embryo develops, an elongate anterior beak through which the hatchling emerges, and an elongate posterior pedicle. The capsules are flanked by a lateral membrane or web on both sides, and the web is reinforced with branching or unbranching rib-like costae that extend laterally from the central body, beak, and pedicle. Specimens are typically about 10–30 cm long. Egg capsules of extant chimaeroids are made of collagen (Hamlett et al., 2005) and as fossils, chimaeroid egg capsules are typically preserved as external casts (Fischer et al., 2014).

Predation is a behavior that is commonly unsuccessful, but the cause of failure is often difficult to determine in the fossil record. Here, we report on gastropod drill holes in two Plio- and Miocene bivalve specimens from the Netherlands created from the inner side of the bivalve prey's shell, which we call reverse drill holes. These holes are unequivocally caused by failure of the gastropod drilling predators to make effective use of their chemoreception and mechanoreception sensory adaptations. We hypothesize that the diffuse nature of chemical cues emanating from dense aggregations of living prey could have confused foraging predators and stimulated them to initiate the drilling process on empty valves. Poor decision making due to hunger is an alternative hypothesis. These traces represent the first reported examples of reverse gastropod drill holes from the fossil record, and the first attributed to Naticidae. Compared to other types of failed predation (incomplete drill holes and drill holes in multiply-drilled specimens) in the two assemblages studied, reverse drill holes are rare (< 1% of drill holes). This result implies that the driller's sensory and decision-making processes were generally reliable at distinguishing dead from live prey.

The existence of Ordovician Peruvian cephalopods has been known since at least the 1910s. However, they have not been effectively documented previously with only a few described taxa listed in open nomenclature. Here, we describe a cephalopod assemblage at the finest taxonomic level possible. The specimens were collected from the Floian section (Baltograptus minutus graptolite Zone) of the San José Formation from the Kimbiri area, northwest of Cuzco (= Cusco), and from a section along the Inambari River, southeastern Peru. The dark mudstone-siltstone of the San José Formation was deposited within the Central Andean Basin. The assemblage contains five species of small orthoceracones belonging to four families and three orders, consisting of one indeterminate dissidocerid, one bathmoceratid (Saloceras sp.), one rioceratid (Rioceras? sp.), and two baltoceratids belonging to Annbactroceras grecicostatum (Kobayashi, 1937), and Bactroceras cocafolium new species. The dominance of small orthoceracones is typical for early Paleozoic pelagic cephalopod assemblages. One species, A. grecicostatum, is known from elsewhere in the Central Andean Basin. The other taxa indicate a peri-Gondwana-Avalonia paleogeographical relationship of the cephalopod fauna, which is consistent with previously published data from brachiopods and trilobites.

UUID: http://zoobank.org/f5cc9686-75f2-46de-bdd9-f279e3b45677

Ediacaran fossils, obtained in stratigraphic context in 1993, 1995, and 1996, with the assistance of A. Seilacher, IGCP project 320 scientists, and the Geological Survey of Namibia, are described for the first time. Most are from the Kliphoek and Buchholzbrunn members of the Dabis Formation and the Huns and Spitskop members of the Urusis Formation, Witputs subbasin, but a significant number, including Pteridinium, are from the Kliphoek Member, Zaris Formation, and the Neiderhagen Member, Nudaus Formation, north of the Osis arch, which separates the two subbasins. We extend the stratigraphic ranges and geographic distributions of several important taxa, including Archaeichnium, Ernietta, Pteridinium, and Swartpuntia, provide reassessments of the paleobiology of these and other organisms, and describe a new sponge—possibly an unmineralized archaeocyath—Arimasia germsi n. gen. n. sp. We also describe and illustrate various ichnofossils (including the oldest known traces from the Nama Group), narrow down the first appearance of Treptichnus in the Nama succession, and reinforce the idea that there was a prolific infauna of micrometazoans during the latest Ediacaran by naming and describing previously reported microburrows found on the surfaces of gutter casts as Ariichnus vagus n. igen. n. isp.

UUID: http://zoobank.org/8c267425-135a-4b0a-98b6-cf726515cbf2

The ontogeny of two species of corynexochid trilobites from the middle Cambrian Mount Cap Formation of the eastern Mackenzie Mountains, northern Canada, is documented. Sahtuia carcajouensis (Dolichometopidae) and Mackenzieaspis parallelispinosa (Zacanthoididae) are both endemic to this formation and only known from one locality. They, along with several other corynexochid taxa, occur in a succession of mudstone with scattered carbonate interbeds, deposited in a weakly storm-agitated setting near the flank of a semi-enclosed basin. The ontogeny of both species is characterized by mainly normal cranidial development, but a unique distribution of segments in their thoraxes and pygidia. The number of trunk segments was typical for their respective families, whereas the final number of segments released into the thorax was reduced. This occurred in both species through timing modifications to segment release, indicating heterochrony. Sahtuia carcajouensis and Mackenzieaspis parallelispinosa are likely derived from two separate clades, and heterochrony probably arose separately but synchronously. The endemicity of both species probably reflects unique paleoecological conditions in this part of the basin. Preliminary results indicate that the fossil-bearing mudstone was deposited under well-oxygenated conditions that underwent high nutrient flux and possibly experienced varying salinity. These factors may have affected the organisms’ physiology, or perhaps provoked an adaptation to achieve early maturation.

Harpetid and trinucleid trilobites share a similar and unusual morphology, the most striking feature of which is a wide, flattened cephalic brim with many pits or holes. This similarity was once interpreted as a sign that these two groups of trilobites were closely related, but in recent years it has instead been assumed that the ‘harpiform’ brim arose in both groups independently. However, relatedness and similarity can be difficult to disentangle in fossil taxa without close living relatives, and this assumption about the harpiform brim has never been explicitly tested. Our study re-evaluates the relationship between Harpetida and Trinucleioidea in order to test a longstanding assumption about trilobite relationships and as a case study in evaluating different kinds of morphological similarity in extinct groups. We inferred a new phylogenetic tree using parsimony methods and discrete morphological character data from a broad sampling of harpetids, trinucleids, and their relatives. Despite their gross morphological similarities, we found that harpetids and trinucleids were readily distinguished in our analyses, a result consistent with a hypothesis of multiple origins for the harpiform brim. By mapping brim-related characters across our new phylogeny, we identified a sequence of morphological innovations that arose in parallel in both groups and led ultimately in each case to the evolution of the harpiform brim. These results indicate that harpiform brims are a prime example of parallel evolution—the similar development of a morphological trait in distantly related taxa that nevertheless share a similar original morphology. In addition, our phylogeny supports the idea that trinucleids are specialized, harpiform asaphids, rather than an independent order of trilobites. We also provide new information on the relationships of the putative ‘basal-most’ members of Trinucleioidea, the Liostracinidae, and confirm recent assessments that this family is more distantly related to trinucleids.

The Ediacaran Subcommission of the International Commission on Stratigraphy is diligently working toward the goal of subdividing the Ediacaran Period into precise and useful chronostratigraphic units. As emphasized by Xiao and colleagues in 2016, one of the most effective tools in this endeavor will be the use of index fossils. Our special issue serves as a presentation of ongoing research efforts aimed at advancing this task and contains explorations into taxonomy, taphonomy, and the diversity of life during the Ediacaran Period.

First-formed shells of several species of Dalmanellidae (Brachiopoda) from the Ordovician (Katian) of North America were measured and compared: Cincinnetina multisecta, Diceromyonia tersa, Diceromyonia storeya, Paucicrura corpulenta, Paucicrura rogata, and Paucicrura sillimani. Sizes and structures of the first-formed shells suggest that members of this family had planktotrophic subadults, with some species showing indications of only an unshelled larval stage and others showing both a larval stage and a shelled juvenile stage. This differs from modern rhynchonelliformean brachiopods, which all possess only a lecithotrophic larval stage. The range of sizes of first-formed shells of most studied species are similar, but P. sillimani of Baffin Island, Canada (middle Katian), has a significantly larger first-formed shell that formed during an extended juvenile stage. This may have enabled the species to colonize newly exploitable habitats during an interval of rapid sea level rise in Laurentia during the Katian. This plasticity of developmental modes in the Dalmanellidae shows not only that using distantly related modern brachiopods as an analog for extinct Paleozoic lineages may be misleading, but also that development can vary within a single lineage and that timing of developmental stages should not be considered a reliable character for use in phylogenetic studies of brachiopods.

Shape deformation during fossilization can prevent accurate reconstruction of an organism's form during life, hampering areas of paleontology ranging from functional morphology to systematics. Retrodeformation attempts to restore the original shape of deformed fossil specimens and requires an adequate knowledge of the deformation process. Although tectonic processes and retrodeformation are relatively well understood, research on quantifying the effect of compressive deformation on fossil morphology is scant. Here we investigate the factors that can cause changes in the shape of fossil specimens during compressive deformation. Three-dimensional (3D) models of trilobite cranidia/cephala are subjected to simulated deposition and compaction using rigid body simulation and scaling features of the open-source 3D software Blender. The variation in pitch and roll angle is lowest on flat surfaces, intermediate on tilted surfaces, and highest on irregular surfaces. These trends are reflected in the morphological differences captured by principal component scores in geometric morphometric analyses using landmarks. In addition, the different shapes of trilobite cranidia/cephala according to their systematic affinity influence the degree of angular variation, which in turn affects their posture—normal or inverted. Inverted cranidia/cephala show greater morphological variability than those with normal postures.

A new genus and species of arachnid (Chelicerata: Arachnida), Douglassarachne acanthopoda n. gen. n. sp., is described from the late Carboniferous (Moscovian) Coal Measures of the Mazon Creek Lagerstätte, Illinois, USA. This is a unique animal with distinctive large spines on the legs. It has a subovate body, a segmented opisthosoma, and a terminal anal tubercle. The legs are robust and appear to have been similar in construction throughout the limb series, with heavy spination of the preserved proximal podomeres. The mouthparts and coxo-sternal region are equivocal. The preserved character combination does not permit easy referral to any known arachnid order, living or extinct, thus the new fossil in placed as Arachnida/Pantetrapulmonata incertae sedis. It contributes to an emerging pattern of disparate body plans among late Carboniferous arachnids, ranging from anatomically modern members of living orders through to extinct taxa, such as the present fossil, whose phylogenetic position remains unresolved.

UUID: http://zoobank.org/b70f5f95-9c8b-4389-bee5-b6031bff2ee2

The Cambrian dokimocephalid trilobite genus Deckera Frederickson, 1949 is a minor component of Steptoean (Jiangshanian) faunas of Laurentian North America. The original diagnosis emphasized strongly inflated palpebral areas of fixed cheeks and elevated palpebral lobes as important and novel characters. An appraisal of archival and new specimens from Oklahoma, Missouri, Pennsylvania, Nevada, Utah, and Newfoundland show that the genus is geographically widespread and likely represented by as many as nine species, although only two of them are named formally. Deckera cf. D. aldenensis Frederickson, 1949 from Nevada extends the stratigraphic range of Deckera down to the base of the Jiangshanian Stage, and new species from Nevada and Newfoundland take the genus down farther, into upper Paibian strata. Paibian species show that some basal members of the genus have weakly inflated, nearly flat palpebral areas with palpebral lobes that sit well below the crest of the glabella. A revised diagnosis of Deckera focuses on the broad cranidium with width across the palpebral lobes much greater than the sagittal length. Pygidia are known for a few species and all of them have an unusual flexure of the posterior margin and border. Lectotype and paralectotype specimens are designated for Deckera completa.

Encompassing global cooling, the spread of grasslands, and biogeographic interchanges, the Hemphillian North American Land Mammal Age is an important interval for understanding the factors driving ecological and evolutionary change through time. McKay Reservoir near Pendleton, Oregon is a natural laboratory for analyses of these factors. It is remarkable for its small vertebrate fauna including rodents, bats, turtles, and lagomorphs, but also for its larger mammal fossils like camelids, rhinocerotids, canids, and felids. Despite the importance of the site, few revisions to its faunal list have been published since its original description. We expand on this description by identifying taxa not previously known from McKay Reservoir based on specimens collected during fieldwork and through reidentification of previously collected fossils. Newly identified taxa include the borophagine canid Borophagus secundus (Matthew and Cook, 1909), the camelids Megatylopus Matthew and Cook, 1909 and Pleiolama Webb and Meachen, 2004, a dromomerycid, and the equids Cormohipparion Skinner and MacFadden, 1977 and Pseudhipparion Ameghino, 1904. Specimens previously assigned to Neohipparion Gidley, 1903 and Hipparion de Christol, 1832 lack the features necessary to diagnose these genera, which are therefore removed from the site's faunal list. The presence of Borophagus secundus, Cormohipparion, and Pseudhipparion is especially important, because each occurrence represents a major geographic range extension. This refined understanding of the fauna lays the foundation for future studies of taphonomy, taxonomy, functional morphology, and paleoecology—potentially at the population, community, or ecosystem levels—at this paleobiologically significant Miocene locality.

In their detailed comments, Das et al. (2023) try to discount our arguments that the strata cropping out at the so-called Jhura pond locality are not Late Jurassic in age but Miocene. We wrote this paper (Fürsich et al., 2023) because of the far-reaching conclusions that have been drawn from the molluscan fauna at that locality, in particular with respect to the evolution of turritellid gastropods and the evolution of drilling predation by naticid gastropods. We still maintain that the beds containing abundant turritellids are not Jurassic but Neogene, most probably Miocene, in age. In no way do we contest the various analyses on the material collected from the outcrop by the authors, but just the erroneous age assignment of the strata. In order to keep this reply short, we support our point by referring to just to two aspects: the position of the outcrop and the composition of the fauna. Rather than refuting each of the other arguments of Das et al. (2023), we think that a joint visit to the locality would be more productive for arriving at a consensus on the origin and age of the fauna of the Jhura pond locality.

Tribrachidium heraldicum Glaessner in Glaessner and Daily, 1959 is a triradial Ediacaran organism found in abundance within the Ediacara Member of the Flinders Ranges, South Australia. Here we report and describe a new species within the genus Tribrachidium Glaessner in Glaessner and Daily, 1959: Tribrachidium gehlingi new species from Nilpena Ediacara National Park (NENP), South Australia. Tribrachidium gehlingi n. sp. has low relief and three slightly curved, main arm-like structures that leave a conspicuous gap between the end of the arm-like structures and rim. In place of the ‘bulla’ found on T. herladicum, there are three secondary arm-like structures approximately half of the length of the main arm-like structures. Key morphological differences between the two species are statistically significantly different. Additionally, the species occur together within the same fossiliferous event horizons, indicating that the observed morphological differences are unlikely a result of taphonomy.

UUID: http://zoobank.org/196bef68-54da-42a9-9327-dcb55411a457

The Eager Formation (Cambrian Stage 4) of the Cranbrook area, British Columbia, contains abundant, sometimes beautifully preserved, trilobites and rare non-biomineralized taxa. Trilobites were first reported just over a century ago but have received little research attention, resulting in uncertainty in the number and identity of species within the assemblage and ambiguity in the age of the fauna. The trilobites of the Eager Formation in the Cranbrook area are described herein based largely upon material collected in 2015. A minimum of eight (and perhaps up to 11) trilobite species are recognized. The four species of olenelloids (Olenellus santuccii Webster n. sp., Olenellus? schofieldi, Mesonacis eagerensis, and Wanneria cranbrookense Webster n. sp.) are by far the most abundant elements of the fauna. At least two, and perhaps as many as five, species of dorypygid are present, as are two species of “ptychoparioids”. Paucity and poor preservational quality of specimens mean that the various dorypygid and “ptychoparioid” species are left in open nomenclature. Trilobite diversity in the Cranbrook Lagerstätte is comparable to that within other Lagerstätten from Cambrian Stage 4 (Series 2) of Laurentia. The diversity and abundance of trilobites, combined with biostratinomic and trace fossil data, suggest that the assemblage is autochthonous and/or parautochthonous, and that the local environment was at least periodically able to support a “typical” benthic trilobite community. The age of the Cranbrook Lagerstätte is constrained to lie within the middle Dyeran Stage of Laurentia, within what was a substantial stratigraphic gap in the distribution of Burgess Shale-type Lagerstätten.

UUID: http://zoobank.org/5beab9df-6b6a-4d6d-95e8-57057cd47a66

Natural history museums house numerous previously undescribed species and unknown information hidden in their collections. We describe lower Carboniferous slit-bearing gastropods (order Pleurotomariida, subclass Vetigastropoda; and family Goniasmatidae, subclass Caenogastropoda) from previously unreported gastropod collections made by Jane Longstaff (Jane Donald), one of the pioneering paleontologists of Paleozoic gastropods in the late nineteenth and early twentieth centuries. The gastropods were collected from the Lower Limestone Formation (Visean, Brigantian) near Dalry, Ayrshire, Scotland. The collection consists largely of microgastropods, many of which are unusually well-preserved including delicate ornament and protoconchs (larval shells). Three new pleurotomariidan species are described—Biarmeaspira heidelbergerae new species, Neilsonia seussae new species, Tapinotomaria longstaffae new species—in addition to seven species belonging to Borestus Thomas, 1940, Stegocoelia (Stegocoelia) Donald, 1889, Stegocoelia (Hypergonia) Donald, 1892, Donaldospira Batten, 1966, and Platyzona Knight, 1945. The caenogastropod-type protoconch is documented for the first time in Hypergonia, which is therefore placed in Goniasmatidae. The new data confirm that Neilsonia Thomas, 1940 (type genus of Neilsoniinae) belongs to Pleurotomariida and is distinct from the morphologically convergent Peruvispira Chronic, 1949 (Goniasmatidae). The selenizone morphology is identical in Biarmeaspira Mazaev, 2006 and Baylea de Koninck, 1883 during their early ontogeny, and Biarmeaspira develops an angulation on the selenizone (the diagnostic feature) in late ontogeny. This corroborates earlier suggestions that Biarmeaspira evolved from Baylea. Biarmeaspira heidelbergerae n. sp. is the first Carboniferous record of Biarmeaspira, which was previously only known from the Permian. The angulated selenizone evidently evolved several times in Pleurotomariida and the repeated appearance of this character in different groups (e.g., Phymatopleuridae, Eotomariidae, Pleurotomariidae) needs further studies using phylogenetic methods.

UUID: http://zoobank.org/92ae9a99-5774-4ee9-bf5d-9a9319494ef6

This work presents a detailed taxonomic study on organic-walled microfossils from the Ediacaran Sete Lagoas Formation (Bambuí Group) at the Barreiro section in the Januária area of the São Francisco basin, Brazil. Seven species are described, including Siphonophycus robustum (Schopf, 1968), Ghoshia januarensis new species, Leiosphaeridia crassa (Naumova, 1949), Leiosphaeridia jacutica (Timofeev, 1966), Leiosphaeridia minutissima (Naumova, 1949), Leiosphaeridia tenuissima Eisenack, 1958, and Germinosphaera bispinosa Mikhailova, 1986. These taxa are recovered for the first time in the Sete Lagoas Formation. They occur abundantly in the lower portion of the studied section, but only Ghoshia januarensis is present in the upper part of the studied section, probably due to environmental or taphonomic changes. Leiosphaeridia species, particularly Leiosphaeridia minutissima, dominate the organic-walled microfossil assemblage. Although most taxa described here have long stratigraphic ranges, they are consistent with a terminal Ediacaran age as inferred from detrital zircon data and tubular fossils (e.g., Cloudina and Corumbella) from the Sete Lagoas Formation.

UUID: http://zoobank.org/7f92b900-0176-4da6-93a3-fd51edb22cbf

Silicified brachiopods from Hirnantian strata in three sections of the lower Whittaker Formation, Mackenzie Mountains, northwestern Canada, yielded a moderately diverse, Edgewood-type Hirnantian fauna, consisting of 13 species: Biparetis paucirugosus, Brevilamnulella laevis, Dalmanella edgewoodensis, Drabovia noixella, Eospirigerina putilla, Epitomyonia paucitropida, Epitomyonia sekwiensis, Glyptorthis papillosa new species, Gnamptorhynchos orbiculoidea, Katastrophomena mackenzii new species, K. parvicardinis, Parastrophina cf. P. minor, and Skenidioides sp. Compared to the typical Edgewood fauna of the American Midcontinent, Brevilamnulella laevis has a notably smaller shell than B. thebesensis, and is interpreted as a deeper-water form. The strong faunal affinity of the Mackenzie Mountains fauna to the Edgewood-type Hirnantian fauna is indicated by the occurrence of Biparetis, Brevilamnulella, Eospirigerina, and Gnamptorhynchos. In addition to the Edgewood type area within Laurentia, Biparetis, Eospirigerina, and Gnamptorhynchos are characteristic taxa that also occur in the Ellis Bay Formation (Hirnantian) of Anticosti Island. Multivariate and network analyses strongly support the differentiation between an Edgewood-type Hirnantian fauna in Laurentia and peri-Laurentia and the typical Hirnantia fauna of the Kosov Province in Gondwana, peri-Gondwana, South China, Kazakhstan terranes, Avalonia, and Baltica.

UUID: http://zoobank.org/7ff8f8c8-52d1-4527-acae-9bacd2e8b914

The Lower Ordovician (Floian) Al Rose Formation from the Inyo Mountains, California, is a deeper-water, graptolitic equivalent of the well-known and richly fossiliferous successions described from Utah and Nevada. It is considered to have been originally marginal to the Laurentian paleocontinent. It has yielded a low-diversity trilobite fauna that differs strikingly from contemporary faunas to the east in its abundance of raphiophorid, nileid, olenid, and agnostoid trilobites, resembling that of the Nileid Biofacies known from scattered locations marginal to Laurentia. Two new trilobite species are described: Globampyx sexsegmentatus (Raphiophoridae) and Protopresbynileus divergens (Nileidae). Carolinites genacinaca Ross, 1951 is a link with the Great Basin. Other trilobites include the olenid Cloacaspis cf. C. ceryx anataphra Fortey, 1974, metagnostid Geragnostus cf. G. (Novoagnostus) longicollis Raymond, 1925, and pliomerid Hintzeia sp.

UUID: https://zoobank.org/19a679ce-968d-4ce1-a590-f7f55bf9d62d

A new cornulitid genus and species, Porkuniconchus fragilis new genus and species, is here described from the Ärina Formation (Hirnantian, Porkuni Regional Stage) of northern Estonia. This new taxon differs from most cornulitids by having a fusiform ornamentation pattern that is somewhat similar to that of Kolihaia. All studied specimens are attached to a carbonate hardground. The hardground fauna is by abundance and encrustation area dominated by cornulitids. Other encrusters are represented only by a single sheet-like cystoporate bryozoan. The cornulitid specimens represent different growth stages, which suggest that the hardground was continuously colonized by cornulitid larvae. The high encrustation density indicates that the studied hardground may have represented a high-productivity site in the Hirnantian of the Baltic Basin.

UUID: http://zoobank.org/623afcc3-ab32-4e8f-be14-a1093cba4ae6