The genus Lanayrella currently comprises two recent, minute gastropods species, Lanayrella vagabunda and L. ringei, both known exclusively from the Magellanic Region. The genus was originally assigned to Acteonidae because it shares with Acteon a relatively wide and thick shell with a moderately elevated spire, a sculpture dominated by spiral elements, and a strong columellar fold. However, it lacks a distinct proto/teleoconch boundary, a diagnostic feature of Acteon. Here, L. ringei is studied for the first time based on shell morphology and gross anatomy, which reveal as key characters a cephalic shield divided into two lobes with lateral tentacular pads and the absence of an operculum. These features strongly suggest that Lanayrella belongs among cephalaspidean gastropods rather than within Acteonidae, a "lower" heterobranch taxon. Furthermore, both shell and radular morphologies are comparable to those of certain species of Toledonia and Bogasonia, leading to Lanayrella bullata n. comb. here proposed. Specimens from the Monte León Formation (lower Miocene) of southern Argentina are herein reported as L. vagabunda representing the first fossil record of the genus. This finding indicates that Lanayrella is part of an ancient lineage of highly distinctive gastropods whose presence in southern South America can be traced back at least 20 million years.

Anatomical and osteological analyses in several species of ophidians belonging to the clade Caenophidia have led to the identification of differentstructures present in the cephalic shields of these reptiles. These structures are observed expressed mainly in the parietal shields, manifesting themselves in different forms. “Major parietal pits,” generally symmetrical, occur in the center of the parietal shields, more or less medially distanced to each other. These may appear circular, linear, separated, conjunct, or in contact with the lateral margin of the parietal shield by a slit. Together with the pits, a new distinct trait has been observed in the parietal shields of different species of colubroids, here named “parietal fossae.” Parietal pits and fossae are situated in correspondence with the paired foramina on the parietal bone’s dorsal plane, which in turn correspond ventrally with the epiphysis, and the contact between the cephalic hemispheres and the optic lobes. Other fossae may be present in certain species, occurring more posteriorly in the parietal shields, or in the supraocular shields, in correspondence with neurovascular foramina and fossae present in the underlying cranial bones. A second category of pits has also been found, here named “minor pits,” which appear randomly within the cephalic shields, and are also linked to neurovascular foramina present in the corresponding cranial bones. A third type of pit, distinct from the others, is the “medial posterior pit”, which has been found in aquatic snakes. This pit occurs in the posterior half of the medial contact of the parietal shields, and corresponds to a large central foramen in the posterior apex of the parietal bone’s plane, ventrally opening within a canal between the two fossae covering the optic lobes. All of these traits have been observed in a large number of snakes belonging to the families Colubridae, Natricidae, Psammophiidae, Atractaspididae, Pareidae, Xenodermidae, Micrelapidae and Elapidae. These do not occur in all individuals within the examined taxa, but rather affect part of the specimens of a given species. Fossae and pits appear to be sporadic surface structures that correspond to neurovascular foramina present in the underlaying cranial bones.

ABSTRACT Cranial neomorphic ossifications are extremely rare and their biological roles are largely unexplored. In mammals, the few known examples concern almost exclusively the anterior part of the snout, in both extant and extinct taxa. Among these atypical anatomies, Neosclerocalyptini glyptodonts have one of the most extraordinary neomorphic ossifications of nasal cartilage. Previous work hypothesized that this ossification corresponds to an optimization of the hydric and thermal regulation from the nasal cavity, coinciding with the global cooling of the climate from the Pliocene onwards. Until now, only the endocranial anatomy of their youngest representative has been explored, preventing an evolutionary appraisal of this climato-anatomical hypothesis. Using X-ray microtomography and an exceptionally well-preserved specimen representing the oldest Pleistocene species, we reveal that in Neosclerocalyptus pseudornatus this neomorphic ossification restricts the narial opening and is not open to the nasal cavity, unlike the youngest species, weakening the hypothesis of an early physiological function. We show also that paranasal sinuses, ethmoturbinates, and septoturbinates appear to be similar within the genus. We argue that the most likely functional origin corresponds to structural support associated with the overall cranial organization and expansion of the cephalic shield. In younger species, the enhancement of hydric and thermal regulation capacities would then be an exaptation.

Among European colubroids, scale sensilla—mechanoreceptors present in the head integument—are more expressed in natricids. The presence of protruded sensilla, observable with the naked eye, is found in the cephalic shields of all species belonging to the genus Natrix. The identification of these sense organs in this genus determines its correlation in aquatic and semi-aquatic species, in which these traits are more developed and recognizable than in terrestrial species. As hypothesized for elapoids, this differentiation could be due to the fact that in natricids, like sea snakes, these can perform a hydrodynamic function in addition to the mechanosensory one. In support of this thesis, within the genus Natrix, the most aquatic species of the five, Natrix tessellata, features the most expressed sensilla. This specificity represents a further analogy in the evolutionary convergences involving the cephalic region that this species shares with marine elapids. Still in the genus Natrix, a second trait involving the shields has been identified, expressing itself in the opposite condition to the protruded sensilla, occurring as a pitting arranged mainly within the shields along the upper portion of the labial arches. In vivo examinations and microscopy were performed on different species of the Natrix genus, and comparative analyses have been carried out on other natricid taxa from the New and Old World, where the presence of protruded scale sensilla has been found in several species.

Abstract A peculiar phyllosoma larva at an intermediate stage was collected in 2006 during a plankton survey in the Mexican Caribbean. Its body length was 7.3 mm. This phyllosoma resembles those of species of Scyllaridae Latreille, 1825 with characters including a pear-shaped cephalic shield, the presence of pereiopod 5 with setae, and traits typical of Scyllarus Fabricius, 1775 at early stages viz., uniramous antenna, circular thorax, and a shallow abdomen. Previously, this phyllosoma had only been reported from Florida, but at a more advanced stage of development. Based on morphological comparison with records of Atlantic phyllosoma larvae, it is considered unlikely that this individual belongs to any of the species previously reported from the Caribbean subregion. Instead, it is proposed that this peculiar larva belongs to the deep-living scyllarid genus Bathyarctus Holthuis, 2002, as it seems more likely that this deep-living larva was vertically transported to the epipelagic layers of the Caribbean.

A new species of Amphisbaena is described from the north of Espinhaço Mountain Range, municipality of Caetité, state of Bahia, Brazil. Amphisbaenaamethysta sp. nov. can be distinguished from its congeners by the following combination of characters: (1) snout convex in profile, slightly compressed not keeled; (2) pectoral scales arranged in regular annuli; (3) four precloacal pores; (4) distinct cephalic shields; (5) 185-199 dorsal half-annuli; (6) 13-16 caudal annuli; (7) conspicuous autotomic site between 4th-6th caudal annuli; (8) 16-21 dorsal and ventral segments at midbody; (9) 3/3 supralabials; (10) 3/3 infralabials; and (11) smooth and rounded tail tip. The new species is the 71st species of genus with four precloacal pores, and the 22nd species from the Caatinga morphoclimatic domain. The identification of Amphisbaenaamethysta sp. nov. indicates that the reptile fossorial fauna in the Espinhaço Mountain Range region is far from being completely known and that it may harbour a much greater diversity of endemic taxa.

The colonization of the pelagic realm by the vertebrates represents one of the major transitions in the evolutionary success of the group and in the establishment of modern complex marine ecosystem. It has been traditionally related with the Devonian rise of jawed vertebrates, but new evidences indicate that first active swimmers, invading the water column, occurred within earlier armoured jawless fishes (“ostracoderms”). These “primitive” fishes lacked conventional fish control surfaces and the precise mechanism used to generate lift and stabilizing forces still remains unclear. We show that, because of their shape, the rigid cephalic shield of Pteraspidiformes, a group of Silurian-Devonian “ostracoderms”, generate significant forces for hydrodynamic lift. Particle Image Velocimetry and force measurements in a water channel shows that the flow over real-sized Pteraspidiformes models is similar to that over delta wings, dominated by the formation of leading-edge vortices resulting in enhanced vortex lift forces and delayed stall angles of attack. Additionally, experiments simulating ground effect show that Pteraspidiformes present better hydrodynamic performance under fully pelagic conditions than in a benthic scenario. This suggests that, lacking movable appendages other than the caudal fin, leading-edge vortices were exploited by earliest vertebrates to colonize the water column more than 400 Mya.

Preservation of digestive structures in trilobites is generally rare; remains of the alimentary tract have been documented in about eighty of more than twenty thousand described species. Several tens of specimens belonging to five Cambrian and nine Ordovician species from the Barrandian area, Czech Republic, have markedly contributed to the knowledge of the trilobite digestive system. Here, we describe seven exceptionally preserved late holaspid trilobite specimens of species of the genus Dalmanitina collected from Upper Ordovician strata of the Barrandian area. All studied specimens are preserved as internal moulds and exhibit a narrow strip-like structure that runs sagitally or sub-sagitally under the axial lobe of the thoracopygon. These strip-like structures are markedly different from scavenger burrows and are interpreted as remains of the alimentary canal. A slightly expanded anterior-most part of the digestive system is preserved in the cephalic shield of six specimens and is interpreted as a remainder of the anterior midgut. A dark area is seen in the glabellar lobes of three specimens. These dark areas do not represent pyrite concentrations in the hypostome–glabellar cavity, because they contain only small amounts of Fe and S. These areas are interpreted as the remainder of cephalic digestive midgut diverticula, or the “perigastric organ”. Quantitative chemical analyses show that in species of Dalmanitina the digestive system is preserved as dark matter containing partly digested food particles and most probably also a higher amount of clay minerals. The described specimens constitute the first well-documented example of digestive structures in the subfamily Dalmanitininae.

Exoskeleton moulting is the process of shedding the old exoskeleton to enable growth, development and repair, representing a crucial recurrent event in the life histories of all euarthropods. The fossil record of moulting allows us to interpret the evolution of this important behaviour and its impact on the evolutionary trajectories of extinct and extant euarthropods. Current knowledge of Palaeozoic euarthropod moulting relates largely to trilobites, with fewer examples known for non-mineralised extinct taxa from early in euarthropod evolutionary history. We describe exuviae from a marrellid marrellomorph found abundantly in the Early Ordovician Fezouata Shale Lagerstätte of Morocco, which allow a novel reconstruction, the second ever, of marrellid moulting behaviours. We identify the moulting suture location, describe preserved moulting assemblages, and suggest how its moulting behaviours are adaptive to its morphology. Several specimens represent complete and nearly complete assemblages and additional disarticulated specimens confirm the suture line location. The suture line is located between the mediolateral and posterolateral spine pairs, dividing the cephalic shield into anterior and posterior parts. The Fezouata marrellid likely exited the exoskeleton during exuviation using posterior and upwards movements, analogous in terms of movement to lobster-like extant arthropods. The suture line is comparable in the closely related marrellid Mimetaster, and distinctive from that of another marrellid, Marrella splendens, which has an exuvial opening at the anterior of the cephalic shield and exited the exoskeleton anteriorly. This difference in moulting behaviour as compared to Marrella is likely adaptive to the greater complexity of the Fezouata marrellid, with upwards rather than forwards movement presumably providing a more favourable angle for the extraction of complex spines. This description of the moulting behaviours and related morphological features of marrellomorphs expands our understanding of this crucial characteristic in extinct euarthropods.

Slipper (Scyllaridae) and spiny (Palinuridae) lobsters show a complex life cycle with a planktonic larval phase, named phyllosoma. This unique larval form within Achelata (Decapoda) is characterized by a transparent dorsoventrally compressed body and a pair of antennae. This conspicuous morphology has been attributed to adaptive specialization of planktonic life. Early studies suggest that phyllosoma morphology has remained constant over the evolutionary history of Achelata, while recent evidence points out large morphological changes and that diversification of phyllosoma larvae is a consequence of radiation and specialization processes to exploit different habitats. Given the ecological and evolutive significance of phyllosoma, we used shape variation of the first phyllosoma stage (phyllosoma I) and a time-calibrated phylogeny of extant Achelata to study how diversification of phyllosoma I shape occurred along with the evolutionary history of Achelata. Our results show a conserved phyllosoma I with a pear-shaped cephalic shield and large antennae in spiny lobsters and older groups of slipper lobsters, yet highly specialized phyllosoma I with wide rounded cephalic shield and short antennae in younger groups of slipper lobsters. Analyses revealed two bursts of lineage diversification in mid and late history without a slowdown in recent times. Both bursts preceded large bursts of morphological disparity. These results joined with the allopatric distribution of species and convergence of phyllosoma I shapes between largely divergent groups suggest that diversification involves nonadaptive radiation processes. However, the correlation of a major direction of shape with the maximum distribution depth of adults and the occurrence of the second burst of diversification post-extinction of competitors within Achelata presuppose some ecological opportunities that might have promoted lineage and morphological diversification, fitting to the characteristic components of adaptive radiations. Therefore, we conclude that diversification of Achelata presents a main signature of nonadaptive radiation with some components of adaptive radiation.

Platypsyllus castoris is closely associated with beavers and displays a unique set of structural specializations. We document the morphology of adults with modern techniques, and interpret evolutionary changes linked with the specific life style. The small subfamily Platypsyllinae has evolved an entire suite of features correlated with a more or less close association with mammals, for instance a flattened body, a dorsal cephalic shield, flightlessness, eye reduction, and depigmentation. Within this small group, Platypsyllus displays numerous autapomorphic features, correlated with a close association with the beaver. Essential is a combination of mechanical stabilization and firm anchorage on the host, and efficient forward movement in the fur. Exo- and endoskeletal structures of the head and thorax are reinforced by vertical cuticular columns and by an array of internal ridges. The antennae are shortened and strongly modified, the mandibles distinctly reduced and flattened, unsuitable for cutting, scraping or grinding. The musculature of the mouthparts is simplified, whereas an enhanced set of prepharyngeal and pharyngeal dilators forms an efficient sucking pump. The prothoracic musculature is strongly developed. In contrast, the pterothoracic muscle system is distinctly simplified, even though leg muscles are strongly developed. Using the legs, the flattened beetles move sideways through the dense fur of the beaver, using posteriorly directed groups of setae and ctenidia to prevent being pushed backwards by the densely arranged hairs. In contrast to the anterior body, the cuticle of the abdomen is thin, and the entire tagma flexible, with thin layers of segmental muscles. The hind gut is not connected with the mid gut. The beetles probably consume liquid, possibly with emulgated minute skin debris. As the morphology of the mouthparts excludes damage to the skin of the host, the association should not be addressed as ectoparasitic but as commensalism.

Two large (ca. 0.5 mm long), rare, and probably closely related species of Facetotecta (y-larvae), Hansenocaris cristalabri sp. nov. and Hansenocaris aquila sp. nov., are described on the basis of last-stage lecithotrophic nauplii reared from plankton at Sesoko Island, Okinawa, Japan. The two species resemble each other in having a labrum with a row of spines and a long, attenuate trunk region that terminates in a long, heavily spinose dorsocaudal spine. The labrum of H. cristalabri sp. nov. has an enormous, cockscomb-like ventral process that bears a row of distally directed, dagger-like spines along its anterior side, while the spine-bearing keel of the labrum of H. aquila sp. nov. extends posteriorly into a robust, eagle-like beak. The labral “crest” of H. cristalabri sp. nov. has no equivalent in any other described y-larva, nor in any other crustacean nauplius; its possible functions are discussed. Another diagnostic feature of H. cristalabri sp. nov., absent in H. aquila sp. nov., is a pair of shallow, rounded notches bounded by sharp spinules on the far posteriolateral margins of the cephalic shield. Both new species have longitudinal spine rows on the trunk dorsum, two rows in H. cristalabri sp. nov. and four in H. aquila sp. nov., something not previously documented for y-nauplii. The plate arrangement of the cephalic shield in H. cristalabri sp. nov. is described in detail, with an attempt to homologize the pattern with that of other y-nauplii (especially Hansenocaris furcifera Itô, 1989). The body surface of H. cristalabri sp. nov. has fewer setae and pores than any other late- or last-stage facetotectan nauplius described to date, suggesting paedomorphic development. A formal diagnosis is presented for the family-group taxon Hansenocarididae fam. nov.; this name, while already in use, has until now been nomenclaturally unavailable.

Cingulata (Mammalia, Xenarthra) from the type fauna of the “Friasian” South American Land-Mammal age, Alto Río Cisnes (Río Frías Formation, Burdigalian-Langhian Age, Miocene), Chile

Abstract Previous studies have suggested species- and individual-specific morphologies of cephalic shields of three-banded armadillos (Tolypeutes spp.). Central cephalic scutes would form discrete lines; the first two posterior lines being composed of one scute (1-1) in Tolypeutes matacus and one followed by two scutes (1-2) in Tolypeutes tricinctus. However, conclusions were limited to a few specimens and the T. tricinctus pattern was later observed in T. matacus. Here, we assessed the potential use of the morphology of the cephalic shield as a species diagnostic trait and individual natural mark in three-banded armadillos by quantifying their patterns in museum (n = 71) and field (n = 82) specimens. In total, 93% of T. matacus and 88% of T. tricinctus specimens presented the respective species’ character states. All specimens could be individualized based on a visual comparison of their cephalic shields. Our findings show that the morphology of cephalic shields is a species diagnostic trait and an individual natural mark in three-banded armadillos. Therefore, we add an accessible character for species diagnosis in Tolypeutes and provide an alternative to artificial marks that presents virtually no associated cost and damage to animal welfare and can be reliably applied in ecological and participatory science projects.

Several phragmotic species in the ant genus Carebara Westwood, 1840 with a cephalic shield are known from the Old World, but species with an anteriorly truncated head seem to be unknown until now. A new species, resembling the phragmotic workers of the ant genus Colobopsis, is here described as Carebara colobopsis Hosoishi & Yamane, sp. nov., based on major and minor worker found in Cambodia. This new species is similar to Carebara acutispina (Xu) and C. obtusidenta (Xu) in some important characters, but distinguished from the latter two by distinct metanotum and deep groove in front of metanotal disc in the major worker, and longer head and deep metanotal groove in the minor worker. This is the first confirmed record of a truncated phragmotic head in the major worker of the genus Carebara. We propose the Carebara acutispina species group to include all the three species, present a diagnosis of this group, and provide a key to species based on the major and minor worker castes.

The Muaco and Taima-Taima sites, in Falcón State of northwestern Venezuela, are among the earliest sites of human occupation in South America containing artifacts associated with preserved megafaunal remains and dating between 19,810 and 15,780 calybp. Here we report novel visual and CT scanning analysis of six glyptodont skulls of Glyptotherium cf. cylindricum from these sites, of which four exhibit distinct and similar patterns of breakages in the fronto-parietal region that suggest intentional blows by direct percussion by humans, with fractures not being diagenetic but instead antemortem or transmortem. This hypothesized and unreported hunting technique focused in an area of the skull where the cephalic shield becomes thin, thus increasing the effectiveness of the blow. From Taima-Taima other glyptodont remains included an inverted carapace, also previously reported as probable evidence of human–glyptodont interaction during the latest Pleistocene. We estimated that roughly 150-170 Kg of potentially accessible muscles and fat of an adult Glyptotherium cylindricum could be used as food sources.

Abstract Cheloniellida is a rare but significant clade of artiopod euarthropods, and a major component of Vicissicaudata alongside aglaspidids. The first cheloniellid to be described wasTriopus draboviensis, based on a single specimen from the Upper Ordovician Letná Formation in Bohemia. Because this specimen was believed to be missing its anterior,Triopus draboviensishas been the subject of considerable speculation regarding its affinities, with several authors combining various isolated cephalic shields with its trunk. Notwithstanding,Triopus draboviensishas eluded detailed restudy in the 150 years since its first description. Here we provide a redescription of the holotype and hitherto only known specimen ofTriopus draboviensis, and describe a recently discovered second partial specimen asTriopussp. It is shown that the holotype ofTriopus draboviensispreserves the complete cephalic shield, while the trunk reveals a likely articulating device, which may represent an apomorphy for Cheloniellida. Further information on the trunk morphology provided by the new specimen has allowed a complete reconstruction of the dorsal exoskeleton ofTriopus. An assessment is made of fossils previously suggested to represent the cephalic shield ofTriopus draboviensis; while it is shown that none of those fossils can be attributed toTriopus, it is reaffirmed thatDrabovaspis complexalikely does belong to Cheloniellida, makingDrabovaspisthe third cheloniellid genus known from the Letná Formation, afterTriopusandDuslia. A revised diagnosis for Cheloniellida is provided, and the recently described problematic euarthropodParioscorpio venatorfrom the Silurian of Wisconsin is firmly rejected from this clade.

ABSTRACT Caridean prawns show five different types of mating systems and may show specific morphological characters depending on the reproductive strategy, resulting in sexual dimorphism between males and females. The present study aimed to analyse the sexual dimorphism in the freshwater prawns Macrobrachium pantanalense and Macrobrachium iheringi, two species that presumably have different mating systems. Our predictions are that the pattern of sexual dimorphism shows differences between the species, which may be related to its mating system and sexual behavior. Sexual dimorphism was analysed by geometric morphometrics using the carapace (CA), second pleonal pleuron (SPP) and cheliped propodus (CP). The geometric morphometrics analysis showed differences between the sexes in the shape of CA and SPP of M. pantanalense. In M. iheringi, differences between sexes were observed only in the shape of SPP. The sexual dimorphism in the size of CA and CP diverged between the species, while in M. pantanalense the females showed the largest sizes, in M. iheringi the males showed the largest sizes. The patterns observed between size and shape of structures in each species reinforce the presence of relationships between mating system and sexual dimorphism in caridean prawn species. http://zoobank.org/urn:lsid:zoobank.org:pub:03DE0D3E-598A-4692-9771-79EA449D92EA

Abstract The purpose of this study was to investigate the relative growth and sexual dimorphism in the hermit crab Clibanarius signatus. The evaluation was done with 955 specimens (494 males, 251 females, and 210 intersexes) captured in Persian Gulf (Iran) during January to December 2015. Animals were submitted to measurements related to weight (BW, total wet weight) and body size related to cephalic shield (SW, width; and SL, length) and propodus of both chelipeds (CPL, length; and CPW, width). Males were larger and heavier than females and intersexes. Both males and females showed a negative allometric growth for the SL–BW and SL–SW relationships, but a positive allometric growth to intersex specimens. To SL–CPL relationship, a negative allometric growth was confirmed in males and females independent of the laterality of the CPL, whereas a contrast was verified in intersexes, with a positive allometric growth occurred for both hands. To SL–CPW relationship, a negative allometric growth (b < 1) occurred in females, independent of the laterality of the CPW, while in males, a positive allometric pattern was confirmed. In intersexes, this relationship was positive except for the right CPW which was isometric. Sexual dimorphism was evident in Clibanarius signatus, with males being the largest and females the smallest specimens in the population.

Since the rearrangement of all leptotyphlopid species previously known as "Leptotyphlops" in Adalsteinsson et al. (2009)'s paper, several taxa have remained untested regarding their generic identity and have been assigned to different genera based on phenotypic data or, in some cases, without any clear justification. Most of the difficulties in assigning some leptotyphlopid taxa are due to their conserved external morphology, summed with a relatively small number of available specimens, which complicate the recognition of a unique combination of characters for their reasonable generic allocation. On the other hand, recent osteological studies-especially those on the skull-provide relevant data combinations for species assignment and even for the recognition of new genera. In this work, we have attempted to determine the generic allocation of Epictia unicolor and Trilepida guayaquilensis-both species currently known only by their holotype-based on a detailed description of cranial and post-cranial osteology. We confirm the assignment of E. unicolor to the genus Epictia despite the divergent configuration of cephalic shields. Based mainly on data from the skull, suspensorium, and cervical vertebrae but supported by external morphology as well as a redescription of the holotype, we propose the assignment of Trilepida guayaquilensis to the genus Epictia. This study provides not only detailed data on the osteology of Epictia, but also a first approach to the putative combination of osteological characters for the genus.