A winged relative of ice-crawlers in amber bridges the cryptic extant Xenonomia and a rich fossil record.

Until the advent of phylogenomics, the atypical morphology of extant representatives of the insect orders Grylloblattodea (ice-crawlers) and Mantophasmatodea (gladiators) had confounding effects on efforts to resolve their placement within Polyneoptera. This recent research has unequivocally shown that these species-poor groups are closely related and form the clade Xenonomia. Nonetheless, divergence dates of these groups remain poorly constrained, and their evolutionary history debated, as the few well-identified fossils, characterized by a suite of morphological features similar to that of extant forms, are comparatively young. Notably, the extant forms of both groups are wingless, whereas most of the pre-Cretaceous insect fossil record is composed of winged insects, which represents a major shortcoming of the taxonomy. Here, we present new specimens embedded in mid-Cretaceous amber from Myanmar and belonging to the recently described species Aristovia daniili. The abundant material and pristine preservation allowed a detailed documentation of the morphology of the species, including critical head features. Combined with a morphological data set encompassing all Polyneoptera, these new data unequivocally demonstrate that A. daniili is a winged stem Grylloblattodea. This discovery demonstrates that winglessness was acquired independently in Grylloblattodea and Mantophasmatodea. Concurrently, wing apomorphic traits shared by the new fossil and earlier fossils demonstrate that a large subset of the former "Protorthoptera" assemblage, representing a third of all known insect species in some Permian localities, are genuine representatives of Xenonomia. Data from the fossil record depict a distinctive evolutionary trajectory, with the group being both highly diverse and abundant during the Permian but experiencing a severe decline from the Triassic onwards.

Small wasps, big muscles: Fore and hind leg modifications in chalcidoid wasps (Hymenoptera: Chalcidoidea).

A particularly conspicuous morphological feature in chalcidoid wasps are strikingly modified legs present in both males and females. It evolved convergently multiple times on either fore or hind legs implying strong evolutionary pressure and a prominent function in the wasps' life history. We investigate the external and internal morphology of the modified legs of five species of chalcidoid wasps representing four families (Ooderidae, Heydeniidae, Chalcididae, and Leucospidae), using light microscopy, scanning electron microscopy and micro computed tomography. We aimed to identify shared characteristics as well as differences between genera/species, leg pairs and sexes and to draw first conclusions about the shared or different functions. All species and sexes share the same general leg morphology, with enlarged femur, curved tibia and a huge flexor tibiae muscle. However, there are also genus/species-specific differences such as distinctive spine-like setae on the femur of Oodera spp., or leg pair-specific differences in the position of the extensor tibiae muscle. Shared characteristics imply a common primary function in which strong forces are required to pull the tibia against the femur while differences imply different secondary functions. Both primary and secondary functions have yet to be revealed beyond informed speculations.

Understanding the ant's unique biting system can improve surgical needle holders.

Mechanical grasping and holding devices depend upon a firm and controlled grip. The possibility to improve this gripping performance is severely limited by the need for miniaturization in many applications, such as robotics, microassembly, or surgery. In this paper, we show how this gripping can be improved in one application (the endoscopic needle holder) by understanding and imitating the design principles that evolution has selected to make the mandibles of an ant a powerful natural gripping device. State-of-the-art kinematic, morphological, and engineering approaches show that the ant, in contrast to other insects, has considerable movement within the articulation and the jaw´s rotational axis. We derived three major evolutionary design principles from the ant's biting apparatus: 1) a mobile joint axis, 2) a tilted orientation of the mandibular axis, and 3) force transmission of the adductor muscle to the tip of the mandible. Application of these three principles to a commercially available endoscopic needle holder resulted in calculated force amplification up to 296% and an experimentally measured one up to 433%. This reduced the amount of translations and rotations of the needle, compared to the needle's original design, while retaining its size or outer shape. This study serves as just one example showing how bioengineers might find elegant solutions to their design problems by closely observing the natural world.

A landmark-free analysis of the pelvic girdle in Sulawesi ricefishes (Adrianichthyidae): How 2D and 3D geometric morphometrics can complement each other in the analysis of a complex structure.

Geometric morphometrics (GM) enable the quantification of morphological variation on various scales. Recent technical advances allow analyzing complex three-dimensional shapes also in cases where landmark-based approaches are not appropriate. Pelvic girdle bones (basipterygia) of Sulawesi ricefishes are 3D structures that challenge traditional morphometrics. We hypothesize that the pelvic girdle of ricefishes experienced sex-biased selection pressures in species where females provide brood care by carrying fertilized eggs supported by elongated pelvic fins ("pelvic brooding"). We test this by comparing pelvic bone shapes of both sexes in species exhibiting pelvic brooding and the more common reproductive strategy "transfer brooding," by using landmark-free 2D and 3D GM, as well as qualitative shape descriptions. Both landmark-free approaches revealed significant interspecific pelvic bone variation in the lateral process, medial facing side of the pelvic bone, and overall external and internal wing shape. Within pelvic brooders, the three analyzed species are clearly distinct, while pelvic bones of the genus Adrianichthys are more similar to transfer brooding Oryzias. Female pelvic brooding Oryzias exhibit prominent, medially pointing tips extending from the internal wing and basipterygial plate that are reduced or absent in conspecific males, Adrianichthys and transfer brooding Oryzias, supporting our hypothesis that selection pressures affecting pelvic girdle shape are sex-biased in Sulawesi ricefishes. Furthermore, both sexes of pelvic brooding Oryzias have overall larger pelvic bones than other investigated ricefishes. Based on these differences, we characterized two reproductive strategy- and sex-dependent pelvic girdle types for Sulawesi ricefishes. Morphological differences between the investigated pelvic brooding genera Adrianichthys and Oryzias provide additional evidence for two independent origins of pelvic brooding. Overall, our findings add to a better understanding on traits related to pelvic brooding in ricefishes and provide a basis for upcoming studies on pelvic girdle function and morphology.

How to stay attached-Formation of the ricefish plug and changes of internal reproductive structures in the pelvic brooding ricefish, Oryzias eversi Herder et al. (2012) (Beloniformes: Adrianichthyidae).

Teleost fishes show an enormous diversity of parental care, ranging from no care to viviparity with maternal provisioning of embryos. External brooders carry their developing eggs attached to their bodies. This requires the formation of novel morphological structures to support attachment. The pelvic brooding ricefish Oryzias eversi evolved such a structure, called the "plug." The plug anchors attaching filaments from the fertilized eggs inside the female reproductive system, allowing the female to carry the embryos until hatching. Using histological sections and µ-computed tomography scanning, we show that the plug is formed by several types of interstitial cells, blood capillaries, and collagen fibrils that encapsulate the end of the attaching filaments in the anterior part of the gonoduct. Even 15 days after the loss of the protruding attaching filaments, the plug remains. In addition, the developed plug contains multinucleated giant cells that are derived from fusing macrophages. We thus hypothesize that the ricefish plug, which is vital for egg attachment in O. eversi, evolved due to an inflammatory reaction. We assume that it forms similar to a foreign body granuloma, as a reaction to irritation or injury of the gonoduct epithelium by the attaching filaments. Our study further corroborates that pelvic brooding entails a complex set of adaptations to prolonged egg-carrying in the female reproductive system. During brooding, for instance, ovulation in the ovary is suppressed and the anterior part of the gonoduct is characterized by an intricate, recessed folding.

Postembryonic development of the tracheal system of beetles in the context of aptery and adaptations towards an arid environment.

The tracheal system comprises one of the major adaptations of insects towards a terrestrial lifestyle. Many aspects such as the modifications towards wing reduction or a life in an arid climate are still poorly understood. To address these issues, we performed the first three-dimensional morphometric analyses of the tracheal system of a wingless insect, the desert beetle Gonopus tibialis and compared it with a flying beetle (Tenebrio molitor). Our results clearly show that the reduction of the flight apparatus has severe consequences for the tracheal system. This includes the reduction of the tracheal density, the relative volume of the trachea, the volume of the respective spiracles and the complete loss of individual tracheae. At the same time, the reduction of wings in the desert beetle allows modifications of the tracheal system that would be impossible in an animal with a functional flight apparatus such as the formation of a subelytral cavity as a part of the tracheal system, the strong elongation of the digestive tract including its tracheal system or the respiration through a single spiracle. Finally, we addressed when these modifications of the tracheal system take place during the development of the studied beetles. We can clearly show that they develop during pupation while the larvae of both species are almost identical in their tracheal system and body shape.

Morphological, functional, and phylogenetic aspects of the head capsule of the cockroach Ergaula capucina (Insecta/Blattodea).

Background: Cockroaches are usually typical omnivorous detritivores and their cephalic morphology is considered to be ancestral in various aspects. Thus, several studies addressed the morphology and function of the blattodean head, and the cockroach usually serves as a model for standard mouthparts in text books. However, so far only two of the three major lineages of Blattodea have been studied and no detailed information for the head of any Corydioidea was available. The present study closes this gap by providing a detailed morphological description of the head of Ergaula capucina, studying some important functional parameters of the mandible and discussing it in a phylogenetic framework. Methods: The cephalic morphology of Ergaula studied in detail using a broad set of different techniques including digital microscopy, µ-computed tomography, and 3-dimensional reconstructions. Concerning the functional morphology of the mandible, we compared the volume and effective cross sections of the eight compartments of the primary mandibular adductor muscle for Ergaula, Blattella germanica, and Salganea rossi and measured the mechanical advantage, i.e., the force transmission ratio for all teeth of the mandible of Ergaula. Results: The head capsule of Ergaula is characterized by a strong sexual dimorphism and typical orthopteran mouthparts. It resembles the head capsule of other roaches in several respects and confirms oesotendons, the reduction of the mesal occelus, and bipartite M. verticopharyngealis and M. hypopharyngosalivaris as blattodean apomorphies. But it also shows some unique adaptations. It is the first described cockroach that lacks the dorsal tentorial arms which has various consequences for the cephalic musculature. On the maxillary lacinia, Ergaula is the first described blattodean to show strong and blunt setae instead of a lacinula, which might be homologues to the dentisetae of dragonflies and mayflies. Like other corydiid roaches that inhabit xeric areas, Ergaula has an atmospheric water-vapor absorption mechanism that includes a gland and a ductus on the epipharnyx and bladders on the hypopharynx. The mandibular adductor is in cockroaches asymmetric, a pattern not found in termites, mantids, or other closely related insects.

Sexual dimorphism in an adaptive radiation: Does intersexual niche differentiation result in ecological character displacement?

Evolutionary radiations are one plausible explanation for the rich biodiversity on Earth. Adaptive radiations are the most studied form of evolutionary radiations, and ecological opportunity has been identified as one factor permitting them. Competition among individuals is supposedly highest in populations of conspecifics. Divergent modes of resource use might minimize trophic overlap, and thus intersexual competition, resulting in ecological character displacement between sexes. However, the role of intersexual differentiation in speciation processes is insufficiently studied. The few studies available suggest that intersexual niche differentiation exists in adaptive radiations, but their role within the radiation, and the extent of differentiation within the organism itself, remains largely unexplored. Here, we test the hypothesis that multiple morphological structures are affected by intersexual niche differentiation in "roundfin" Telmatherina, the first case where intersexual niche differentiation was demonstrated in an adaptive fish radiation. We show that sexes of two of the three morphospecies differ in several structural components of the head, all of these are likely adaptive. Sexual dimorphism is linked to the respective morphospecies-specific ecology and affects several axes of variation. Trait variation translates into different feeding modes, processing types, and habitat usages that add to interspecific variation in all three morphospecies. Intrasexual selection, that is, male-male competition, may contribute to variation in some of the traits, but appears unlikely in internal structures, which are invisible to other individuals. We conclude that intersexual variation adds to the adaptive diversity of roundfins and might play a key role in minimizing intersexual competition in emerging radiations.

On the value of Burmese amber for understanding insect evolution: Insights from †Heterobathmilla - an exceptional stem group genus of Strepsiptera (Insecta).

Burmese amber and amber from other periods and regions became a rich source of new extinct insect species and yielded important insights in insect evolution in the dimension of time. Amber fossils have contributed to the understanding of the phylogeny, biology, and biogeography of insects and other groups, and have also gained great importance for dating molecular trees. Another major potential is the documentation of faunal, floral and climatic shifts. Evolutionary transitions can be well-documented in amber fossils and can reveal anatomical transformations and the age of appearance of structural features. Here, using a new stem group species of Strepsiptera from Burmite, we evaluate this potential of amber insect fossils to assess the current phylogeny of Strepsiptera, with the main emphasis on the early splitting events in the stem group. Amber fossils have greatly contributed to the understanding of the evolution of Strepsiptera in the late Mesozoic and the Cenozoic. †Heterobathmilla kakopoios Pohl and Beutel gen. et sp. n. described here is placed in the stem group of the order, in a clade with †Kinzelbachilla (†Kinzelbachillidae) and †Phthanoxenos (†Phthanoxenidae). †Phthanoxenidae has priority over †Kinzelbachillidae, and the latter is synonymised. The superb details available from this new fossil allowed us to explore unique features of the antennae, mouthparts, and male copulatory apparatus, and to provide a phylogenetic hypothesis for the order. The younger †Protoxenos from Eocene Baltic amber was confirmed as sister to all remaining extinct and extant groups of Strepsiptera, whereas the position of the Cretaceous †Cretostylops in the stem group remains ambivalent. While the value of Burmite and amber from other periods has a recognized impact on our knowledge of the evolution in various lineages, this new fossil does not fundamentally change our picture of the phylogeny and evolution of early Strepsiptera. However, it offers new insights into the morphological diversity in the early evolution of the group.

A review of the hexapod tracheal system with a focus on the apterygote groups.

Respiratory systems are key innovations for the radiation of terrestrial arthropods. It is therefore surprising that there is still a considerable lack of knowledge. In this review of the available information on tracheal systems of hexapods (with a focus on the apterygote lineages Protura, Collembola, Diplura, Archaeognatha and Zygentoma), we summarize available data on the spiracles (number, position and morphology), the shape and variability of tracheal branching patterns including anastomoses, the tracheal fine structure and the respiratory proteins. The available data are strongly fragmented, and information for most subgroups is missing. In various cases, individual observations for one species account for the knowledge of the entire order. The available data show that there are strong differences between but also within apterygote orders. We conclude that the available data are insufficient to derive detailed conclusions on the hexapod ground plan and outline the possible evolutionary scenarios for the tracheal system in this group.

Complex sexually dimorphic traits shape the parallel evolution of a novel reproductive strategy in Sulawesi ricefishes (Adrianichthyidae).

BACKGROUND: Pelvic brooding is a form of uni-parental care, and likely evolved in parallel in two lineages of Sulawesi ricefishes. Contrary to all other ricefishes, females of pelvic brooding species do not deposit eggs at a substrate (transfer brooding), but carry them until the fry hatches. We assume that modifications reducing the costs of egg carrying are beneficial for pelvic brooding females, but likely disadvantageous in conspecific males, which might be resolved by the evolution of sexual dimorphism via sexual antagonistic selection. Thus we hypothesize that the evolution of pelvic brooding gave rise to female-specific skeletal adaptations that are shared by both pelvic brooding lineages, but are absent in conspecific males and transfer brooding species. To tackle this, we combine 3D-imaging and morphometrics to analyze skeletal adaptations to pelvic brooding. RESULTS: The morphology of skeletal traits correlated with sex and brooding strategy across seven ricefish species. Pelvic brooding females have short ribs caudal of the pelvic girdle forming a ventral concavity and clearly elongated and thickened pelvic fins compared to both sexes of transfer brooding species. The ventral concavity limits the body cavity volume in female pelvic brooders. Thus body volumes are smaller compared to males in pelvic brooding species, a pattern sharply contrasted by transfer brooding species. CONCLUSIONS: We showed in a comparative framework that highly similar, sexually dimorphic traits evolved in parallel in both lineages of pelvic brooding ricefish species. Key traits, present in all pelvic brooding females, were absent or much less pronounced in conspecific males and both sexes of transfer brooding species, indicating that they are non-beneficial or even maladaptive for ricefishes not providing extended care. We assume that the combination of ventral concavity and robust, elongated fins reduces drag of brooding females and provides protection and stability to the egg cluster. Thus ricefishes are one of the rare examples where environmental factors rather than sexual selection shaped the evolution of sexually dimorphic skeletal adaptations.

Comparative transcriptomics of ice-crawlers demonstrates cold specialization constrains niche evolution in a relict lineage.

Key changes in ecological niche space are often critical to understanding how lineages diversify during adaptive radiations. However, the converse, or understanding why some lineages are depauperate and relictual, is more challenging, as many factors may constrain niche evolution. In the case of the insect order Grylloblattodea, highly conserved thermal breadth is assumed to be closely tied to their relictual status, but has not been formerly tested. Here, we investigate whether evolutionary constraints in the physiological tolerance of temperature can help explain relictualism in this lineage. Using a comparative transcriptomics approach, we investigate gene expression following acute heat and cold stress across members of Grylloblattodea and their sister group, Mantophasmatodea. We additionally examine patterns of protein evolution, to identify candidate genes of positive selection. We demonstrate that cold specialization in Grylloblattodea has been accompanied by the loss of the inducible heat shock response under both acute heat and cold stress. Additionally, there is widespread evidence of selection on protein-coding genes consistent with evolutionary constraints due to cold specialization. This includes positive selection on genes involved in trehalose transport, metabolic function, mitochondrial function, oxygen reduction, oxidative stress, and protein synthesis. These patterns of molecular adaptation suggest that Grylloblattodea have undergone evolutionary trade-offs to survive in cold habitats and should be considered highly vulnerable to climate change. Finally, our transcriptomic data provide a robust backbone phylogeny for generic relationships within Grylloblattodea and Mantophasmatodea. Major phylogenetic splits in each group relate to arid conditions driving biogeographical patterns, with support for a sister-group relationship between North American Grylloblatta and Altai-Sayan Grylloblattella, and a range disjunction in Namibia splitting major clades within Mantophasmatodea.

Author Correction: Phylogenomic analysis sheds light on the evolutionary pathways towards acoustic communication in Orthoptera.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Phylogenomic analysis sheds light on the evolutionary pathways towards acoustic communication in Orthoptera.

Acoustic communication is enabled by the evolution of specialised hearing and sound producing organs. In this study, we performed a large-scale macroevolutionary study to understand how both hearing and sound production evolved and affected diversification in the insect order Orthoptera, which includes many familiar singing insects, such as crickets, katydids, and grasshoppers. Using phylogenomic data, we firmly establish phylogenetic relationships among the major lineages and divergence time estimates within Orthoptera, as well as the lineage-specific and dynamic patterns of evolution for hearing and sound producing organs. In the suborder Ensifera, we infer that forewing-based stridulation and tibial tympanal ears co-evolved, but in the suborder Caelifera, abdominal tympanal ears first evolved in a non-sexual context, and later co-opted for sexual signalling when sound producing organs evolved. However, we find little evidence that the evolution of hearing and sound producing organs increased diversification rates in those lineages with known acoustic communication.

Ear asymmetry in Tengmalm's owl (Aegolius funereus): Two phases of asymmetrical development of the squamoso-occipital wing.

Ear asymmetry is an adaptive characteristic present in the order of owls (Strigiformes). It developed independently up to seven times in this taxon and is accompanied by morphological adaptations in bones or soft tissues around or at the ear openings. Within all strigiform species, the Boreal or Tengmalm's owl (Aegolius funereus) possesses a particularly complex bilateral ear asymmetry that results from modifications of the neurocranium and some cartilaginous elements. While the ear asymmetry in adult birds has been described in detail, data on its development is scarce. Here we describe the development of the asymmetric squamoso-occipital wing of A. funereus from its embryonic origin up to adulthood. The asymmetry of the squamoso-occipital wing develops in two phases. Firstly, it originates as a cartilaginous structure in the last ten days before hatching. Its frontal margin shows a bilateral asymmetry from the beginning of its development while the rostro-ventral process stays symmetrical up to post-hatching day 35. Secondly, when the fledglings have already left the nest, the squamoso-occipital wing ossifies. Moreover, the rostro-ventral process on the right side grows towards the eyeball, while there is no relative displacement on the left side. Thus, the developmental process in A. funereus differs from that in the barn owl that develops its soft tissue asymmetry in one phase and completes the asymmetry before hatching. The new data presented here extend our knowledge of the mechanisms underlying the asymmetric skull development in owls.

Do we need the third dimension? Quantifying the effect of the z-axis in 3D geometric morphometrics based on sailfin silversides (Telmatherinidae).

This study investigated the impact of the third dimension in geometric morphometrics (GM) using sailfin silversides (Telmatherinidae) from the Malili Lakes of Sulawesi (Indonesia). The three morphospecies of the monophyletic "roundfin" radiation are laterally compressed and vary in shape traits. The results of 2D and 3D GM were compared and quantified to discuss the advantages and disadvantages of both methods for closely related species and their sexes. This approach focused on the head because it is far more complex and three-dimensionally structured than the trunk or the caudal region. The results revealed no significant benefit concerning repeatability and measurement error in 3D GM compared to 2D GM. The z-axis contributed substantially to the variance of the 3D data set but was irrelevant for discrimination of species and sexes in the approach. Limited gain in information was contrasted by substantially higher effort for 3D compared to the 2D analyses. The study concluded that 2D GM is the more efficient shape analysis approach for discriminating roundfins. Broader studies are needed to test which of the two methods is more efficient in distinguishing laterally compressed fishes in general. For future studies, due to the high investment required, this study recommends carefully evaluating the necessity of 3D GM. If in doubt, this study suggests testing for congruence between 2D and 3D GM with a subsample and consequently applying 2D GM in the case of high congruence.

Description of a new Moridilla species from North Sulawesi, Indonesia (Mollusca: Nudibranchia: Aeolidioidea)-based on MicroCT, histological and molecular analyses.

We describe a new species, Moridilla jobeli sp. nov., belonging to the marine heterobranch group Aeolidioidea. Up to now, it is only recorded from Bunaken National Park, North Sulawesi, Indonesia. A combination of histological, computer tomographic and scanning electron microscopic methods was applied in order to describe and illustrate the anatomy of Moridilla jobeli sp. nov. in detail. Furthermore, we conducted molecular analyses which include available partial COI and 16S rRNA sequences, as well as the nuclear gene Histone 3 (H3) of Facelinidae and Aeolidiidae. NeighborNet analyses, species delimitation tests and phylogenetic reconstruction methods show the distinctiveness of the new species from the type species Moridilla brockii Bergh, 1888 and the two recently described species Moridilla fifo Carmona Wilson, 2018 and Moridilla hermanita Carmona Wilson, 2018, as well as the monophyly of the genus. A phylogenetic analysis of the Facelinidae and Aeolidiidae does not result in a resolved tree, therefore relationship of former assumed closely related genera, Noumeaella Risbec, 1937 and Palisa Edmunds, 1964, cannot be discussed in detail.

The cephalic morphology of the troglobiontic cholevine species Troglocharinus ferreri (Coleoptera, Leiodidae).

Leiodidae are the second largest subterranean radiation of beetles at family rank. To explore morphological trends linked with troglobiontic habits and characters with potential phylogenetic significance, the head of the cave-dwelling species Troglocharinus ferreri (Cholevinae, Leptodirini) was examined in detail. Overall, the general pattern is similar to what is found in Catops ventricosus (Cholevini). Shared apomorphic features include a fully exposed anterolateral concavity containing the antennal socket, a distinct bead above this depression, a bilobed lip-like structure anterad the labrum, a flat elevated portion of the ventral mandibular surface, and a ventral process at the proximomesal edge of this mandibular area. The tentorial structures are well-developed as in C. ventricosus, with a large laminatentorium and somewhat shortened dorsal arms. The mouthparts are largely unmodified, with the exception of unusually well-developed extrinsic maxillary muscles. Features of T. ferreri obviously linked with subterranean habits are the complete lack of compound eyes, circumocular ridges, and optic lobes. A series of characters is similar to conditions found in other genera of Leptodirini: the head capsule completely lacks a protruding ocular region, a distinct neck is missing, the transverse occipital crest is indistinct, and the antennae are elongate and lack a distinct club. Two different trends of cephalic transformations occur in troglobiontic Leptodirini, with some genera like Troglocharinus and Leptodirus having elongated head capsules and antennae, and others having broadened, more transverse heads. In contrast, the modifications are more uniform in the closely related Ptomaphagini, with a pattern distinctly differing from Leptodirini: the head is transverse, with a distinctly protruding ocular region, a distinct transverse occipital crest, and a very narrow neck region.

An integrative phylogenomic approach illuminates the evolutionary history of cockroaches and termites (Blattodea).

Phylogenetic relationships among subgroups of cockroaches and termites are still matters of debate. Their divergence times and major phenotypic transitions during evolution are also not yet settled. We addressed these points by combining the first nuclear phylogenomic study of termites and cockroaches with a thorough approach to divergence time analysis, identification of endosymbionts, and reconstruction of ancestral morphological traits and behaviour. Analyses of the phylogenetic relationships within Blattodea robustly confirm previously uncertain hypotheses such as the sister-group relationship between Blaberoidea and remaining Blattodea, and Lamproblatta being the closest relative to the social and wood-feeding Cryptocercus and termites. Consequently, we propose new names for various clades in Blattodea: Cryptocercus + termites = Tutricablattae; Lamproblattidae + Tutricablattae = Kittrickea; and Blattoidea + Corydioidea = Solumblattodea. Our inferred divergence times contradict previous studies by showing that most subgroups of Blattodea evolved in the Cretaceous, reducing the gap between molecular estimates of divergence times and the fossil record. On a phenotypic level, the blattodean ground-plan is for egg packages to be laid directly in a hole while other forms of oviposition, including ovovivipary and vivipary, arose later. Finally, other changes in egg care strategy may have allowed for the adaptation of nest building and other novelties.