Pterygotids were Paleozoic marine and marginal marine large apex predatory arthropods. However, their evolution remains poorly understood due to the scarcity of their fossils and the delicate nature of their exoskeletons. The well-studied Devonian Xiaxishancun Formation in Qujing City, Yunnan, China contains various Agnatha and three eurypterid species. Our study focuses on the eurypterid material assigned to Erettopterus qujingensis Ma et al., 2022 and Pterygotus wanggaii Ma et al., 2023. The two species were discovered from the same locality, both with individuals of different developmental stages (juveniles more common), suggesting that this area could represent a breeding site, in agreement with mass molt behavior and the occurrence of other pterygotids in shallow waters. Moreover, the coexistence of heavily armed Agnatha with Pterygotus wanggaii in the Xiaxishancun Formation, alongside their robust chelicerae, supports the hypothesis that some pterygotids were piscivorous. In addition, due to ambiguity of pterygotid cheliceral dentition nomenclature, we introduce a new framework to define the cheliceral denticle types of pterygotids based on their relative positions: TD, terminal denticle; MD, median denticle (including: MMD, modified MD, and OMD, ordinary MD); BD, basal denticle. A key diagnostic feature in the cheliceral denticles of E. qujingensis is established: movable finger ends in a curved TD, 3 MMD’s present, 9 OMDs between MMD1 and MMD2 (OMD4 and OMD8 slightly enlarged); fixed finger ends in an acute TD’, 3 MMD’s present (MMD’2 being the largest), 8 OMD’s between MMD’1 and MMD’2 (OMD’5 slightly enlarged), 15 OMD’s between MMD’2 and MMD’3 (OMD’1 and OMD’10-12 slightly enlarged). This cheliceral diagnosis distinguishes E. qujingensis from Pterygotus wanggaii by its distinct number of MMDs.

Perna perna mussel is a coastal benthic filter-feeder widely cultivated in mytiliculture farms and serves as a resource for local communities engaged in its harvest along the Brazilian coast. This study presents the isotopic ratios (δ13C and δ15N) in the soft tissues of adult mussels from six natural populations in Rio de Janeiro State, southeast Brazil, to evaluate whether they are sensitive enough to distinguish the origin of specimens. The COVID-19 pandemic served as temporal reference, as the quality of coastal waters was influenced by the restrictions imposed during the pandemic. The mean values of δ13C and δ15N ranged from −19.5‰ to −17.3‰, and 6.2‰ to 10.5‰, respectively. The spatial variation of δ13C-δ15N data in the analysed mussels was greater than the temporal variation. The k-means clustering method correctly identified 80% of populations during the pre-pandemic period, 67% in the pandemic, and 50% in the post-pandemic. In most samples, the spatial variation of δ15N (tracer of food source variability) was the primary variable distinguishing the groups of mussels. The isotopic ratios did not reveal a clear trend when using the COVID-19 pandemic as temporal reference. Consequently, the positive environmental changes brought about by the suspension or reduction of anthropogenic activities in coastal waters during the pandemic had minimal impact on the isotopic ratios of mussels at most sampling sites. The utilisation of δ13C-δ15N data to trace the origin of P. perna mussel from natural banks was only partially effective in distinguishing the origin of natural populations across the studied area.

This study provides the first case reported of Paraprionospio treadwelli (Hartman, 1951) in the Gulf of Mexico. Based on 242 individuals collected between 20.8 and 176 m depth during three oceanographic expeditions, we describe in detail the morphology of the identified specimens, including the description of the pygidium, so far unknown in this species, and provide SEM photographs to support their identification. Paraprionospio treadwelli was originally found in Chesapeake Bay, Northwestern Atlantic, and we now extend its distribution southwards to the Western Gulf of Mexico. Remarks on the environmental conditions where this spionid species was found and the observed abundance seasonal pattern are also provided.

Fossil data are subject to inherent biological, geologic, and anthropogenic filters that can distort our interpretations of ancient life and environments. The inevitable presence of incomplete fossils thus requires a holistic assessment of how to navigate the downstream effects of bias on our ability to accurately reconstruct aspects of biology in deep time. In particular, we must assess how biases affect our capacity to infer evolutionary relationships, which are essential to analyses of diversification, paleobiogeography, and biostratigraphy in Earth history. In this study, we use an established completeness metric to quantify the effects of taphonomic filters on the amount of phylogenetic information available in the fossil record of 795 extinct squamate (e.g., lizards, snakes, amphisbaenians, and mosasaurs) species spanning 242 Myr of geologic time. This study found no meaningful relationship between spatiotemporal sampling intensity and fossil record completeness. Instead, major differences in squamate fossil record completeness stem from a combination of anatomy/body size and affinities of different squamate groups to specific lithologies and depositional environments. These results reveal that naturally occurring processes create structural megabiases that filter anatomical and phylogenetic data in the squamate fossil record, while anthropogenic processes play a secondary role.

The Gulf of California, one of the world’s most biodiverse marine ecosystems, is also heavily exploited by fisheries. Among its fish fauna are species that, although currently underappreciated, may become commercially important in the future. Enhancing our biological knowledge of these species is crucial for monitoring population dynamics and community changes. Fish parasites offer valuable insights into host ecology, including feeding habits and population structure. In this study, we document the metazoan parasite fauna of Trichiurus nitens (Trichiuridae) from four locations in the eastern Gulf of California, Mexico. A total of 165 fish specimens were examined, revealing five parasite species identified using both morphological characteristics and molecular markers: the monogenean Octoplectanocotyla travassosi, the trematode Lecithochirium sinaloense, and three nematodes – Anisakis typica A, Skrjabinisakis brevispiculata, and Spinitectus sp. Among these, L. sinaloense was the most prevalent. Although parasite species richness was similar between small and large fish, overall parasite abundance was higher in larger specimens. Moreover, parasite assemblages did not vary significantly across the study locations. These findings suggest that T. nitens exhibits a specialized feeding strategy, relying on a narrow range of prey throughout its life, and that the oceanographic variability does not limit fish movement in the region. Future studies encompassing a broader geographical scale, additional fish size classes, and different climatic seasons are needed to further elucidate the ecological role of this species. This work provides novel insights into the host-parasite dynamics of T. nitens and establishes a valuable baseline for ecosystem monitoring under global change scenarios.

The first geographically widespread metazoans form the Avalon assemblage (Ediacaran; 574–560 Ma). These early animals were regularly disturbed by sedimentation events such as ash flows and turbidites, leading to an apparent “resetting” of communities. However, it is not clear how biological legacies—remains or survivors of disturbance events—influenced community ecology in the Avalon. Here, we use spatial point process analysis on 19 Avalon paleocommunities to test whether two forms of biological legacy (fragmentary remains of Fractofusus and survivor fronds) impacted the recolonization dynamics of Avalon paleocommunities. We found that densities of Fractofusus were increased around the Fractofusus fragments, suggesting that they helped to recolonize the post-disturbance substrate, potentially contributing to the Fractofusus dominance found in 8 of the 19 paleocommunities. However, we found no such effects for survivor fronds. Our results suggest that the evolution of height was for long-distance dispersal rather than local recolonization. In modern deep-sea environments, there is a trade-off between local and long-distance dispersal, and our work demonstrates that this differentiation of reproductive strategies had already developed in the early animals of the Avalon.

We report a new stratigraphic section in the Argentine Precordillera (Zanja Honda, west of Pachimoco, San Juan Province), recording the Silurian-Devonian transition. It corresponds to particular siliciclastics of the uppermost 75 m of the Los Espejos Formation (LEF) exhibiting coquines at the base, noduliferous dark siltstones above, then greenish-brown sandstones, and subsequently, a reddish, massive, fine-grained sandstone interval. The overlying shaly lower interval of the Talacasto Formation records the homalonotid trilobite Burmeisteria notica (Clarke, 1913a), indicating the Lochkovian-Pragian interval. Brachiopods and trilobites of the basal coquinites are typical of the upper Silurian of the LEF elsewhere. However, Slovinograptus Urbanek, 1997, the youngest graptolite from southwestern Gondwana, indicates the Silurian-Devonian transition in the basal coquine. The dalmanitid Pachimocaspis pachimocensis new genus new species comes from this and other undoubted Silurian underlying coquinites. The brachiopod and trilobite associations disappear in the overlying dark nodular siltstone interval, replaced by an earliest Lochkovian Orthostrophia meridionalis Benedetto in Benedetto et al., 1992 brachiopod association and a monospecific Pachimocaspis pachimocensis n. gen. n. sp. Thus, we recognize a neat faunal turnover around the Silurian-Devonian boundary as in other southern South American localities. We refer to Pachimocaspis pachimocensis n. gen. n. sp. pygidia from the Silurian-Devonian of Bolivia and the lowest Pragian of the Talacasto Formation from Las Aguaditas locality in the Precordillera Basin. Pachimocaspis pachimocensis n. gen. n. sp. lacks the typical pygidial dalmanitid morphology, exhibiting instead a subelliptical shape with no caudal spine. Also, thoracic pleural tips are variably blunt along the thorax in contrast with the evenly spinose dalmanitid morphology. The morphology of this taxon challenges its systematic position in regarding Silurian-Devonian subfamilies from high paleolatitudes, resembling instead extra-Gondwanic, early Silurian synphoriines.

UUID: http://zoobank.org/df0b0726-a8e9-4c30-bf1d-217c54467609

As the capital of medieval Makuria, Old Dongola, Sudan was one of the largest sites in the region and a center of religious and cultural importance. The annex to the monastery on Kom H at Old Dongola, functioning from the 6/7th through 14/15th c. CE, contains three distinct burial crypts that have been proposed as having been utilized for the burials of social elites, quite likely Makurian Church or monastic officials. Each crypt contains multiple burials, ranging from five (Crypt 3) to seven (Crypts 1 and 2), bringing forth questions of temporality and re-use. Medieval Makurian burials do not typically contain grave goods or personal items, reducing the possibility of establishing temporality through relative dating. In the absence of substantial grave goods allowing for seriation and temporal affiliation of interments, and with only the epitaph of Georgios providing a date of 1113 CE, it has thus far not been possible to differentiate the timeframes of interment for the individuals interred within Crypts 1–3 on Kom H at Old Dongola nor the establishment of these crypts in relation to the monastery. To gain further insight to the periods of use of these crypt burial spaces, 18 human bone collagen samples were submitted for radiocarbon dating at Poznań Radiocarbon Laboratory. The results of radiocarbon dating provide novel insights to the use of Crypts 1–3 at the Kom H monastery, allowing for periodization of this burial environment in relation to the larger adjacent medieval cemetery and Old Dongola community.