Zoological Journal of the Linnean Society

Taxonomic uncertainty at the species level compromises our knowledge of biodiversity, conservation and systematics. The impact of such uncertainty is heightened in megadiverse regions such as Amazonia due to high levels of cryptic diversity. We used integrative taxonomy based on newly collected topotypical specimens to redescribe the Amazonian nurse frog Allobates gasconi and infer its phylogenetic relationships. This species was described in 2002 based solely on morphology, but several characters crucial for the reliable diagnosis of species in Allobates were not considered. Our results show that A. gasconi sensu stricto is not a member of the A. caeruleodactylus clade as previously claimed, but is a member of the A. trilineatus clade. Allobates gasconi is readily distinguished from congeners by a combination of morphological and bioacoustic characters; a revised diagnosis is provided. The type series of A. gasconi comprises more than one species, and we exclude a paratype from lower Jurua River. The species is restricted geographically to flooded environments in the middle and upper Jurua River in Brazil and in the Ucayali River in Peru. The initial misidentification, subsequent absence of topotypic molecular and acoustic data, and the poor preservation condition of the type series have contributed to taxonomic confusion since A. gasconi was first described. The descriptions of other species of Allobates published more than two decades ago were based mainly on gross morphology and we recommend integrative taxonomic revisions to elucidate their systematics.

With an estimated 100,000 extant species, Darwin wasps (Ichneumonidae) are more specious than all vertebrates together. However, only 288 fossil species have been described to date, with hundreds more awaiting formal description in palaeontological collections. One of the largest gaps in our knowledge concerns the ~12 million years between the K-PG mass extinction and the late Ypresian, from which only two species have been formally described, including Pimpla stigmatica Henriksen from the Danish Fur Formation (~55 Ma). Ie here redescribe and reclassify this species in the genus Epitheronia Gupta, n. comb., and describe nine new species from this fossil locality that are consistent with a placement in Pimplinae: Crusopimpla collina n. sp., C. elongata n. sp., C. minuta n. sp., C. rettigi n. sp., C. violina n. sp., Theronia? furensis n. sp., T. nigriscutum n. sp., Xanthopimpla ciboisae n. sp., and X. crescendae n. sp. The diagnosis of the genus Crusopimpla Kopylov, Spasojevic & Klopfstein is amend in the light of the new species. By comparing the preserved colouration between and within specimens of different species, we draw conclusions about the taxonomic usefulness of colour patterns observed in Fur Formation ichneumonids. The number of described species of pimpline parasitoid wasps from Fur is very high when compared to any other fossil deposit, but low with respect to numbers of extant species. Further study and excavation of Fur ichneumonids will certainly reveal an even higher diversity.

The Jaera albifrons species complex comprises several closely related species of intertidal marine isopods that exhibit limited morphological differentiation and varying degrees of hybridization. In this pilot study, we analyzed regions of the nuclear rRNA genes (D1-D2 and ITS1) from populations of J. albifrons, J. praehirsuta, and J. ischiosetosa to assess their utility as diagnostic markers for species identification and phylogenetic inference. Despite the species morphological distinctness and ecological differences, rRNA variability was remarkably shallow across the complex, with only few variable sites in D1-D2 and ITS1. This contrasted sharply with high interspecific divergence observed in other Jaera species, indicating recent divergence and nascent speciation within the complex. J. ischiosetosa showed the lowest intra-individual variation and was most distinct from the two other species. Overlap between J. albifrons and J. praehirsuta genotypes, consistent with known introgressive hybridization, was considerable and likely stems from introgressive hybridization. Local hybridization patterns identifiable morphologically varied across settlements with of the settlements demonstrating unusually high hybridization rates. Different settlements were found to demonstrate a range of abiotic factors impacting spatial separation of the different species and varying degrees of similarity between the species in rRNA genotypes. Phylogenetic analysis of the genus revealed that the J. albifrons complex originates from among the species of the Mediterranean species group and represents a recent migration from the Mediterranean rather than an early-diverging lineage as previously suggested. These findings highlight the challenges of using rRNA markers for species delimitation in recently diverged and hybridizing taxa and underscore variable hybridization and spatial segregation as key factors shaping coexistence in mixed populations.

The symphyseal anatomy of extant and fossil cercopithecids has not yet been demonstrated as a useful tool for taxonomic discrimination, and the source of variation in cercopithecid symphysis has not been addressed on a broad taxonomic scale. Here, we used linear and angular dimensions to quantify symphysis shape. Using univariate, multivariate data and allometric regressions (partial least squares and phylogenetic generalized least square regressions), we addressed the hypothesis that extant cercopithecids can be distinguished by symphysis shape. Significant differences in univariate and multivariate data and allometric regressions permitted to distinguish cercopithecids at the subfamilial, tribal, and genus levels. We showed that multivariate data followed the distribution expected under Brownian Motion and significantly discriminates taxa at different taxonomic levels. Colobine symphysis are characterized by developed inferior transverse tori, short planum alveolare, and short symphysis, whereas cercopithecine symphysis are characterized by developed superior transverse tori, long planum alveolare, and long symphysis. Exceptions to this pattern exist within each subfamily, and this study underlines the particular anatomy of Colobus and Presbytis among the colobines, Allenopithecus among the Cercopithecini, and Theropithecus and Lophocebus among the Papionini. We also demonstrate that the relative development of the transverse tori, the relative length of the planum alveolare and symphyseal inclination are dimorphic traits. Specifically, we show that the symphysis of Procolobus verus, Nasalis larvatus, and Papio anubis is strongly dimorphic.

African cichlids are model systems for evolutionary studies and for host-parasite interactions, because of their adaptive radiations and because they harbour many species of monogenean parasites with high host-specificity. Here, we sampled five locations in southern Lake Victoria, the youngest of the African Great Lakes. We surveyed gillinfecting monogeneans from 18 cichlid species belonging to the Lake Victoria radiation superflock and two cichlid species representing two older and distantly related lineages. We found one species of Gyrodactylus (Gyrodactylidae, Monogenea), Gyrodactylus sturmbaueri Vanhove, Snoeks, Volckaert & Huyse, 2011, and seven species of Cichlidogyrus (Dactylogyridae, Monogenea). Four species are herein described: Cichlidogyrus pseudodossoui n. sp., C. nyanza n. sp., C. furu n. sp., C. vetusmolendarius n. sp.. Another species is reported but not formally described (because of few specimens and morphological similarity with C. furu n. sp.). Two other species are redescribed: Cichlidogyrus bifurcatus Paperna, 1960 and C. longipenis Paperna & Thurston, 1969. Our results confirm that the monogenean fauna of Victorian littoral cichlids displays lower species richness and lower host-specificity than that of Lake Tanganyika littoral cichlids. In C. furu n. sp., hooks V are clearly longer than the other hooks, highlighting the need to re-evaluate the current classification system of haptoral configurations that considers hook pairs III-VII as rather uniform. Some morphological features of C. bifurcatus, C. longipenis and C. nyanza n. sp. suggest that these are closely related to other congeners that infect haplochromines. We also found morphological indications that representatives of Cichlidogyrus colonised Lake Victoria haplochromines or their ancestors at least twice, which is in line with the Lake Victoria superflock being colonized by two cichlid tribes (Haplochromini and Oreochromini). DisclaimerThis preprint is disclaimed for purposes of Zoological Nomenclature in accordance with the International Code of Zoological Nomenclature, Fourth Edition Articles 8.2 and 8.3 (ICZN 1999). No new names or nomenclatural changes are available from statements in this preprint. Resume - Quatre especes nouvelles de Cichlidogyrus (Platyhelminthes, Monogenea, Dactylogyridae) parasites dhaplochromine (Cichlidae) du lac Victoria, avec la redescription de C. bifurcatus and C. longipenisA cause des radiations adaptatives quils ont subies, les cichlides africain sont des systemes modeles pour etudier levolution, mais aussi les relations hotes/parasites, car ils hebergent de nombreuses especes de Monogenes parasites qui presentent une specificite etroite vis-a-vis de leurs hotes. Dans ce travail, nous avons echantillonne cinq localites dans le Sud du lac Victoria, le plus jeune des grands lacs dAfrique de lEst. Nous avons examine les Monogenes presents sur les branchies de 18 especes de Cichlides appartenant a la radiation adaptative << superflock >> du lac Victoria et de deux especes representant deux lignees anciennes et non etroitement apparentees. Nous avons trouve une espece de Gyrodactylus (Gyrodactylidae, Monogenea), Gyrodactylus sturmbaueri Vanhove, Snoeks, Volckaert & Huyse, 2011 et sept especes de Cichlidogyrus (Dactylogyridae, Monogenea). Quatre especes nouvelles sont decrites dans le present travail : Cichlidogyrus pseudodossoui n. sp., C. nyanza n. sp., C. furu n. sp., C. vetusmolendarius n. sp.. Une est signalee mais non decrite formellement (trop peux dindividus recueillis, morphologiquement proche de C. furu n. sp.). Deux autres sont redecrites : Cichlidogyrus bifurcatus Paperna, 1960 and C. longipenis Paperna & Thurston, 1969. Nos resultats confirment que la faune des Monogenes des Cichlides du lac Victoria fait preuve dune richesse specifique et dune specificite moins importante que celle du lac Tanganyika. Chez C. furu n. sp. la paire de crochet V etant nettement plus longue que les autres, il faudra reconsiderer le systeme de classification actuel des types de hapteurs chez les Cichlidogyrus, qui considere que tous les crochets (III a VII) ont la meme taille. Quelques caracteristiques morphologiques de C. bifurcatus, C. longipenis et C. nyanza n. sp. pourraient etre la preuve dune ascendance commune avec des congeneres presents chez dautres Haplochromines. De meme, certains caracteres indiqueraient que des representants des Cichlidogyrus ont colonise les Haplochromines du lac Victoria, ou leurs ancetres, au moins a deux reprises, ce qui est coherent avec une colonisation du lac par deux lignees de cichlides distinctes (Haplochromini and Oreochromini).

We present an integrative taxonomic study describing the first fossil representative of the family Protanguillidae from the Danian deposits near Palenque, Chiapas, Mexico. Osteological analysis and parsimony-based phylogenetic reconstruction using morphological characters support the designation of a new genus and species as a protanguillid by the presence of several features, including the autogenous premaxillae, the presence of metapterygoid and symplectic bones, the participation of pterosphenoid on the posterior margin of orbital margin, the reduced number of vertebrae, and the configuration of hypural complex. The new taxon differs from Protanguilla palau by the shape of last branchiostegal ray, the disposition of anterodorsal branch of subopercle, and the insertion of unpaired fins. To investigate the evolutionary history of true eels, we conducted a total-evidence tip-dating analysis combining 14 mitochondrial genes with a morphological matrix, incorporating both Cretaceous and Cenozoic fossil taxa. The results support a gradual acquisition of the diagnostic characters of Anguilliformes throughout the Cretaceous. A Bayesian topological test further supports the species here described as a surviving lineage of Cretaceous eels with {dagger}Libanechelyidae bultyncki, closely related to the modern eels. This discovery expands the paleobiogeographic range of the Protoanguillidae and provides new insight into the origin and diversification of true eels.

I examined a total of 27,581 images of 6.345 individuals from the Cornell Lab of Ornithologys Macaulay Library to clarify conflicting reports on molt and plumage strategies in eight species of hummingbirds that breed or have bred primarily in the southwestern United States. Fixed replacement sequences from two nodes among primaries and two nodes among secondaries were found without exception, conforming to the findings of previous studies. I concluded that the preformative molt is limited to partial in three species, partial to incomplete in three species, partial to complete in one species, and complete in one species. These molt strategies could be interpreted as having differentiated through synapomorphy, with species between currently recognized clades varying in the extent of their preformative molts; however, given the plastic nature of molt strategies, I predict that this variation will be shaped more by environmental factors than by synapomorphy. Results of this study additionally clarify molt terminology in Trochilidae as based on homologies and establish new criteria for age determinations. The Macaulay Library clearly provides an important resource for the investigation of avian molts and plumages. The results of a validation exercise that I conducted indicate that banders and field ornithologists with a wide range of previous experience can collect accurate data in this manner. I present a road map for such studies and suggest many other questions on avian molt that can also be investigated, including how timing of molts vary geographically and by habitat and how remigial replacement sequences proceed in little-known bird families. I encourage contributors to the Macaulay Library to take and upload images of birds in molt or in worn plumages.

Understanding behavioral differences between non-native and closely related endangered species could be important to aid conservation management. In volume 169 of Zoology, Bels et al. (2025) reported on their comparison of display-action-patterns (DAP) between native Iguana delicatissima and non-native iguanas present on islands of the Guadeloupe Archipelago in the Caribbean Lesser Antilles. Here, we address conceptual and methodological concerns about their work and reanalyze their data given our proposed corrections, primarily a literature-informed adjustment of their "species" category. We additionally utilize online videos from South American mainland I. iguana populations, from where the non-native iguanas in the Guadeloupe Archipelago originate, to better understand the different DAPs between native and non-native iguanas in the Guadeloupe Archipelago. Significant differences in DAP characteristics among "species" categories (native I. delicatissima, non-native iguanas, and hybrids) show that Bels et al. (2025) oversimplified their data analyses by merging all non-native populations into one group. This result indicates the presence of behavioral variation among subpopulations within widely hybridizing iguanid populations, which has been poorly studied. Additionally, videos from mainland populations across two major mitochondrial clades of Iguana iguana show that non-native iguanas on Guadeloupe retained DAP characteristics of those populations from which they originate. We discuss these findings in light of the proposed hypotheses put forward by Bels et al. (2025), of which two can be excluded. Overall, our reanalysis shows that studies focusing on characteristics within settings of complex hybridization in diverse species should acknowledge this complexity.

Kolomyjec et al. (2020). Phylogenetic analysis of Michigan’s freshwater sponges (Porifera, Spongillidae) using extended COI mtDNA sequences. – Zoologica Scripta, 00, 000-000. The phylogenetic relationships of eight species of freshwater sponges sampled throughout the State of Michigan in the North American Great Lakes region were examined as part of a Course-based Undergraduate Research Experience (CURE). An extended version of the standard cytochrome oxidase subunit I (COI) metazoan DNA was used for sequencing and Bayesian phylogenetic inference. The extended gene region (COI-ext) produces a 1,200 bp amplicon instead of the standard 640 bp fragment which compensates for the standard amplicon’s low informatics value in Phylum Porifera. The species examined clustered into strongly supported monophyletic species groups within the family Spongillidae. This study represents the first look at the phylogenetic relationships of freshwater sponges in the Great Lakes Region.Per Kolomyjec, College of Science and the Environment, Lake Superior State University, 650 W Easterday Ave., Sault Sainte Marie, MI 49783, USA. E-mail skolomyjec{at}lssu.eduCompeting Interest StatementThe authors have declared no competing interest.View Full Text

This study aims to discriminate cercopithecid taxa of higher taxonomic levels (subfamily, tribe, subtribe, and genus) on the basis of corpus shape in transverse cross-section at the M1-M2 junction and to assess its variation using 2D geometric morphometrics. Specifically, we evaluated the effect of allometry and sexual dimorphism on differences in corpus shape at interspecific and intraspecific levels, respectively. We also investigated whether corpus variation among cercopithecids was following Brownian motion using Pagels {lambda}. Taxonomic discrimination and sexual dimorphism were established using Analysis of Variance on Principal Component scores. Allometry was studied using phylogenetic least-squares regressions and partial least-squares regressions. We demonstrated that, using corpus shape, extant cercopithecids can be significantly discriminated at the subfamilial, tribal, and subtribal levels. In addition, the main axis of variation of the Principal Component Analysis follows a distribution expected under Brownian motion, validating the presence of a phylogenetic signal in corpus shape. Colobines exhibit a robust corpus (superoinferiorly short and transversely broad) with large lateral prominences while cercopithecines have a gracile corpus (superoinferiorly long and transversely thin in its distal portion) with marked corpus fossae in African papionins. Exception to the typical subfamilial or tribal shape pattern exist, with the best examples being Trachypithecus, Presbytis and Pygathrix within colobines, Allenopithecus within Cercopithecini, and Macaca, Theropithecus and Cercocebus within Papionini. Sexual dimorphism is a confounding factor in shape discrimination, as there are significant differences between sexes, notably in Papio anubis, Nasalis larvatus and Procolobus verus . Intriguingly, sexual dimorphism in corpus shape does not seem to follow the dimorphism deduced in canine and molar crown dimensions. This discrepancy is illustrated by the low degree of dimorphism in corpus shape in Piliocolobus badius, despite dimorphic canine and molar dimensions. Overall, our findings concerning corpus shape variation in cercopithecids will greatly benefit to paleontological studies that seek to identify taxa in the fossil record, and to neontological studies aiming to explore the ecomorphological value of the cercopithecid mandible.

The morphology and the anatomy of the copulatory apparatus in a Dugesiidae population from the SW Romania are presented. The copulatory apparatus is characterized by intermingled bursal canal musculature and two distinct penis bulbs with two large seminal vesicles. Based on these morphological characters, the population is assigned to the "lugubris-polychroa" group of species, now belonging to the genus Schmidtea (de Vries & Sluys 1991). The copulatory apparatus is also characterised by the presence of an atrial fold, characteristic of S. mediterranea. The assign of the morphotype here presented to the species level is delayed until integrative molecular analysis.

As biological shape is usually complex and evolves on different constraints, it can be assessed using integrative methods such as geometric morphometrics. Allometric changes were analysed in three species of Didelphis genus (D. albiventris n=20, D. marsupialis n=82, D. pernigra n=35) by means of geometric morphometric techniques. A significant correlation between shape and size was found, suggesting an allometric change pattern for all three species studied. However, allometries appeared to be different between D. marsupialis and D. pernigra, both of which belong to different groups (the so-called black-eared group and the white-eared group, respectively). Results are consistent with taxonomic recognition at the group level and can help to elucidate phylogenetic relationships between these three Didelphis species.

Owing to the largely unexplored diversity of metazoan parasites, their speciation mechanisms and the circumstances under which such speciation occurs--in allopatry or sympatry--remain vastly understudied. Cichlids and their monogenean flatworm parasites have previously served as study system for macroevolutionary processes, e.g. for the role of East African host radiations on parasite communities. Here, we investigate the diversity and evolution of the poorly explored monogeneans infecting a West and Central African lineage of cichlid fishes: Chromidotilapiini Greenwood, 1987, which is the most species-rich tribe of cichlids in this region. We screened gills of 149 host specimens (27 species) from natural history collections and measured systematically informative characters of the sclerotised attachment and reproductive organs of the parasites. Ten monogenean species (Dactylogyridae: Cichlidogyrus and Onchobdella) were found, eight of which are described and one redescribed herein. The phylogenetic positions of chromidotilapiines-infecting species of Cichlidogyrus were inferred through a parsimony analysis of the morphological characters. Furthermore, we employed machine learning algorithms to detect morphological features associated with the main lineages of Cichlidogyrus. Although the results of these experimental algorithms remain inconclusive, the parsimony analysis indicates that West and Central African lineages of Cichlidogyrus and Onchobdella are monophyletic, unlike the paraphyletic host lineages. Several instances of host sharing suggest occurrences of intra-host speciation (sympatry) and host switching (allopatry). Some morphological variation was recorded that may also indicate the presence of species complexes. We conclude that collection material can provide important insights on parasite evolution despite the lack of well-preserved DNA material. Data availability statementType material was deposited in the invertebrate collection of the Royal Museum for Central Africa (Tervuren, Belgium) (RMCA) (RMCA_VERMES_XXXXX-XXX), the collection of the Research Group Zoology: Biodiversity and Toxicology of Hasselt University (Diepenbeek, Belgium) (HU XXX-XXX), the Finnish Museum of Natural History (Helsinki, Finland) (MZH XXXXX-XXX), and the Iziko South African Museum (Cape Town, South Africa) (SAMC-XXXXXXX-XXX). The morphological data that support the findings of this study are openly available in MorphoBank at www.morphobank.org, at https://dx.doi.org/XXXXXXXX. Phylogenetic trees and data matrices for the analysis in TNT are included as additional data in MorphoBank.

The anadromous Hickory Shad Alosa mediocris (Mitchill, 1814) (Clupeiformes: Clupeidae) is reviewed, specifically regarding morphometric and meristic variation. Despite its long history as recognized species, few descriptions of Hickory Shad morphometric and meristic characters exist in the literature. Most authors of the historic literature have failed to provide capture location for specimens, analyze large numbers of Hickory Shad, or document how morphometric and meristic characters of the species vary spatially. To address this information gap, a total of 717 mature Hickory Shad were collected from 23 different locations in Maryland, Delaware, Virginia, North Carolina, South Carolina, Georgia, and Florida using electroshocking, gill net, or rod and reel. All specimens were frozen, thawed, and 17 morphometric characters and four meristic characters were examined; a random subset (n = 463) were analyzed for an additional four meristic counts of gill rakers. Overall specimens ranged from 206-389 mm SL with a mean + SD of 278.41 + 27.69 mm, 232-435 mm FL with a mean of 310.98 + 30.35 mm, and 272-508 mm TL with a mean of 365.62 + 35.52 mm. The linear relationships between FL and TL, and FL and SL, were investigated and found to be: TL = 1.169*FL + 1.660 (n=705, r2=0.995) and SL = 0.909*FL - 4.274 (n=717, r2=0.992). Substantial differences in character means for many morphometric measurements were found between male and female specimens, suggesting strong sexual dimorphisms relating to shape. However, meristic characters did not show differences in character means by sex. No one morphometric measurement could distinguish Hickory Shad from other morphologically similar clupeids, but the meristic count of gill rakers on the lower limb of the first arch were important to separate Hickory Shad (19-22) from American Shad A. sapidissima (Wilson, 1811), Alewife A. pseudoharengus (Wilson, 1811), and Blueback Herring A. aestivalis (Mitchill, 1814).

BackgroundPolystomatidae represents a monogenean group whose representatives infect mainly (semi)-aquatic tetrapods. Sphyranuridae with its single genus (Sphyranura) exhibits ectoparasitism on salamander hosts and was traditionally considered a sister-group to Polystomatidae based on the presence of a well-developed opisthaptor yet was distinguished due to the presence of a single pair of haptoral suckers, as opposed to the three pairs present in polystomatids. However, more recent molecular work supported its inclusion within Polystomatidae, at an early diverging, yet unresolved, position in the clade of polystomatids that otherwise exhibit endoparasitism of batrachians. Resolving the position of Sphyranura in relation to Polystomatidae is a prerequisite for understanding the factors driving evolution and the shifts between ecto- and endoparasitism in Polystomatidae. MethodsVarious staining methods were used to morphologically characterise collected specimens of Sphyranura. The mitochondrial genome was assembled from WGS data. Based on a combination of nuclear (18S, 28S rRNA) and mitochondrial markers (cox1, 12S) we inferred the phylogeny of Polystomatidae using Bayesian inference and maximum likelihood methods. ResultsBased on morphological examination and comparison with type material, specimens of Sphyranura infecting Oklahoma salamander (Eurycea tynerensis) at Greathouse Spring, Arkansas (USA), were identified as S. euryceae, a new distributional record for the species. Along with an amended diagnosis of Sphyranura we provide the first molecular data for S. euryceae. Mitochondrial level comparison reveals instances of tRNA gene rearrangements in polystomatids. Our phylogeny identifies two clades within polystomatids infecting tetrapods, one infecting exclusively batrachians, the other mainly known from chelonians. Although not fully supported, Sphyranura appears as the earliest branching lineage within the former. ConclusionsWith Sphyranura nested within Polystomatidae, we consider Sphyranuridae invalid. Sphyranuras apparent early branching position indicates ectoparasitism is an ancestral trait with endoparasitism having evolved later in the Polbatrach clade. However, the reduced number of haptoral suckers in representatives of Sphyranura is a derived characteristic potentially resulting from paedomorphic evolution. Whilst there is an indication towards phylogenetic congruence of polystomatids and their batrachian hosts, the same was not true for polystomatid parasites of chelonians with evidence of multiple host switches. Furthermore, geographic distribution of hosts was not found to drive polystomatid phylogeny.

We report the first confirmed record of the ranellid gastropod Turritriton labiosus (Wood, 1828) from the island of Tenerife in the northeastern Atlantic Ocean. A single shell specimen was discovered at 6 m depth approximately 100m off the southern coast. The specimen matches the reddish-orange morphotype previously reported from Indo-Pacific localities such as Guam and the Marshall Islands. This constitutes a new biogeographic record, potentially indicative of long-distance larval dispersal or an unrecognized Atlantic population. Morphological comparisons, shell dimensions, and habitat context are discussed. The specimen is housed in the authors curated private scientific reference collection and has been documented on iNaturalist and RedPROMAR.

Hydrozoan cnidarians are widely known for a diversity of life cycles. While some hydrozoan polyps produce medusae, in most species the gonophore remains attached to the polyp. Little is known about the mechanisms behind the loss of the medusal stage in hydrozoans. Hydrozoan Sarsia lovenii is a promising model for studying this issue. It is a polymorphic species with several haplogroups. One haplogroup produces attached eumedusoids and the other one buds free-swimming medusae. Here, we compared patterns of cell proliferation and distribution of nematocytes in medusoids, medusa buds and medusae of S. lovenii. Cell proliferation is absent from exumbrella of late medusa buds and medusae, but presumably i-cells proliferate in exumbrella of medusoids. In exumbrella of medusoids, we also observed evenly distributed nematocytes with capsules and expression of late nematogenesis-associated gene, Nowa. Nematocyte capsules and Nowa expression were also observed in exumbrella of medusa bud, but we did not detect prominent Nowa signal in the bell of developed medusa. It is also known that abundance of exumbrellar nematocysts signs immaturity in medusae of Sarsia genus. Our data demonstrate that nematocyte distribution and associated gene expression in medusoids resemble medusa buds rather than developed medusae. Thus, sexually mature medusoids exhibit juvenile somatic characters, demonstrating signs of neoteny. Research highlightsHydrozoan Sarsia lovenii has attached eumedusoids and free-swimming medusae. The distribution of nematocytes in eumedusoids resembles that in medusa buds. This may indicate neoteny of eumedusoids.

In 1946 Gilmore observed that the Hell Creek Formation portion of the late Maastrichtian TT-zone contained more tyrannosaur taxa than just titanic Tyrannosaurus rex, based on a small, ontogenetically mature skull with a higher tooth count than the tyrant lizard. Over four decades later the skull was assigned to its own genus, Nanotyrannus lancensis. Also tagged shortly after was the genus Stygivenator molnari. At the turn of the century it was contended that all TT-zone tyrannosaurs are adult or juvenile T. rex, a view that became accepted by many. Because of the unusual morphological alterations that this hypothesis requires, it was consequently proposed that during ontogeny T. rex experienced a peculiar fish like metamorphosis. Detailing normal amniote growth more broadly than prior work on the subject, this analysis rejects radical ontogenetic speculations, in favor of Tyrannosaurus having shared much the same average amniote/diapsid conventional growth observed in its fellow tyrannosaurids and especially tyrannosaurins. Actual juvenile Tyrannosaurus specimens show the same tooth count and other osteological features observed in the adults, negating the need for the metamorphosis not observed in any amniotes. Most lesser sized TT-zone tyrannosaurs possess a number of features that indicate they are not only not Tyrannosaurus, but represent an array of basal eutyrannosaur taxa that are neither Nanotyrannus nor Stygivenator, with high tooth counts, and at least in some examples elongated hands, prominent dentary grooves and other features. Two new taxa are correspondingly named, Gilmorelarsontyrannus lethaeus and Elegansvenator zannoae. These are postulated to represent at least in part the migration of basal eutyrannosaurs from former Appalachia into the Laramidia region via the new Laralachia land bridge. The total number of tyrannosaur taxa now known to have inhabited the TT-zone for over 1 MA is seven species in five genera from multiple subfamilies, with a smaller portion of this collection extant at any given stratigraphic level.

Ascidians are marine filter feeder primitive chordates. Botrylloides ascidians possess diverse biological abilities like whole-body regeneration (WBR), hibernation/aestivation, blastogenesis, metamorphosis, and natural chimerism. However, the absence of distinctive morphological features often makes identification problematic. Botrylloides diegensis is an ascidian that has been misidentified in previous studies and is recorded in GenBank as Botrylloides leachii due to the high morphological similarity between the sister species. More available sequences and strategies around identification would help resolve some of the confusion currently surrounding its ambiguous nature. We collected several Botrylloides samples from 7 locations around New Zealand - Dunedin, Christchurch, Picton, Nelson, Whangateau, New Plymouth and Invercargill - and barcoded the species based on Cytochrome Oxidase I, Histone 3, 18S, and 28S ribosomal RNA markers. Network and Bayesian trees confirmed the presence of three Botrylloides species: B. diegensis, B. jacksonianum, and B. aff. anceps. Additionally, morphotypes of three species were investigated regarding zooid size, area, tentacle numbers and colonial arrangement.

The genus Zoniferella includes six taxa of land snails from Colombia and Ecuador for which little has been published beyond their original descriptions. In this paper, we present new records of Zoniferella vespera, a species previously known only from its type locality, expanding its range across northwestern Ecuador. We provide the first description of the colouration in life for Zoniferella snails. We comment on the similarities among some species of Zoniferella, suggesting the possibility that Z. vespera and Z. riveti are junior synonyms of Z. albobalteata, and Z. bicingulata is a synonym of Z. riveti var. bizonalis (as Z. bizonalis). Finally, we offer evidence to allow the restriction of the locality of "Los Puentes", type locality of Mesembrinis vesperus Jousseaume, 1887 = Zoniferella vespera (Gastropoda: Achatinidae); Isomeria bourcieri lutea Cousin, 1887 (Gastropoda: Labyrinthidae); Guestieria locardi Jousseaume, 1887 (Gastropoda: Scolodontidae); Proserpinella cousini Jousseaume, 1887 (Gastropoda: Proserpinellidae); Idiophthalma robusta Simon, 1889 (Arachnida: Barychelidae); Eurypelma (Lasiodora) augusti Simon, 1889 = Pamphobeteus augusti (Arachnida: Theraphosidae), Eurypelma (Lasiodora) vespertinus Simon, 1889 = Pamphobeteus vespertinus (Arachnida: Theraphosidae).