40 new specimens of Ichthyornis provide unprecedented insight into the postcranial morphology of crownward stem group birds.

Ichthyornis has long been recognized as a pivotally important fossil taxon for understanding the latest stages of the dinosaur-bird transition, but little significant new postcranial material has been brought to light since initial descriptions of partial skeletons in the 19th Century. Here, we present new information on the postcranial morphology of Ichthyornis from 40 previously undescribed specimens, providing the most detailed morphological assessment of Ichthyornis to date. The new material includes four partially complete skeletons and numerous well-preserved isolated elements, enabling new anatomical observations such as muscle attachments previously undescribed for Mesozoic euornitheans. Among the elements that were previously unknown or poorly represented for Ichthyornis, the new specimens include an almost-complete axial series, a hypocleideum-bearing furcula, radial carpal bones, fibulae, a complete tarsometatarsus bearing a rudimentary hypotarsus, and one of the first-known nearly complete three-dimensional sterna from a Mesozoic avialan. Several pedal phalanges are preserved, revealing a remarkably enlarged pes presumably related to foot-propelled swimming. Although diagnosable as Ichthyornis, the new specimens exhibit a substantial degree of morphological variation, some of which may relate to ontogenetic changes. Phylogenetic analyses incorporating our new data and employing alternative morphological datasets recover Ichthyornis stemward of Hesperornithes and Iaceornis, in line with some recent hypotheses regarding the topology of the crownward-most portion of the avian stem group, and we establish phylogenetically-defined clade names for relevant avialan subclades to help facilitate consistent discourse in future work. The new information provided by these specimens improves our understanding of morphological evolution among the crownward-most non-neornithine avialans immediately preceding the origin of crown group birds.

Discussion on ‘Tabelliscolex (Cricocosmiidae: Palaeoscolecidomorpha) from the early Cambrian Chengjiang Biota and the evolution of seriation in Ecdysozoa’ by Shi et al. 2021 (JGS, jgs2021-060)

Exceptionally preserved fossils are key to reconstructing the origin of the modern animal body plans in the Cambrian radiation. The Panarthropod phyla Euarthropoda, Onychophora and Tardigrada have roots in a ‘lobopodian’ grade typified by broadly cylindrical organisms with sclerotized dorsal plates and paired ventral projections. A similar anatomical configuration has been taken to link certain palaeoscolecid worms with the earliest ecdysozoans. Shi et al. (2021) contend that these similarities evolved convergently, and that palaeoscolecids are priapulan relatives with little bearing on the panarthropod evolution.Here we show that this conclusion holds only under a particular treatment of inapplicable character states with known shortcomings. When inapplicable tokens are handled more rigorously, palaeoscolecids are most parsimoniously reconstructed as stem-group panarthropods with homologous dorsal plates and ventral projections – highlighting the degree to which the treatment of inapplicable data can influence fundamental evolutionary conclusions. As the position of palaeoscolecids depends so strongly on the underlying methodology, and is highly uncertain under a Bayesian approach, we consider it premature to exclude the possibility that panarthropods evolved from a grade of palaeoscolecids with dorsal plates and ventral projections.Supplementary material:https://doi.org/10.6084/m9.figshare.16419522

Die Stammgruppe der Fächerflügler (Insecta, Strepsiptera)

Die Fächerflügler (Strepsiptera) sind mit nur ca. 600 beschriebenen rezenten Arten eine kleine, parasitische Gruppe der holometabolen Insekten. Fossilfunde sind selten, aber in den letzten Jahren hat sich die Kenntnis der Stammgruppe der Strepsiptera durch die Entdeckung gut erhaltener Arten aus kreidezeitlichem burmesischem Bernstein und eozänem baltischen Bernstein stark vermehrt. Bis auf ganz wenige Ausnahmen, wie eine fossile Primärlarve aus burmesischem Bernstein und ein spätes weibliches Larvenstadium der †Mengeidae aus baltischem Bernstein, sind nur Männchen bekannt. Diese Bernsteinfossilien haben wesentlich zum Verständnis der Evolution der Strepsiptera im späten Mesozoikum und Känozoikum beigetragen. Die Stammgruppenvertreter der Fächerflügler werden vorgestellt und in einen evolutiven Kontext eingeordnet. The stem-group of the twisted-winged parasites (Insecta, Strepsiptera) Abstract: With only about 600 described extant species, the twisted-winged parasites (Strepsiptera) are a small, parasitic group of holometabolous insects. Fossil records of Strepsiptera are rare, but in the last years the knowledge of the stem group has greatly increased with the discovery of well-preserved species from Cretaceous Burmese amber and Eocene Baltic amber. With very few exceptions, such as a fossil primary larva from Burmese amber and a late female larval stage of the †Mengeidae from Baltic amber, only males are known. These amber fossils have greatly contributed to the understanding of the evolution of Strepsiptera in the late Mesozoic and Cenozoic. The stem group representatives of the twisted-winged parasites are described and placed in an evolutionary context.

Protohemiphlebiidae fam. nov., a stem hemiphlebioid damselfly from Cretaceous amber in Kachin

Hemiphlebiidae are the most basal lestomorphan family following the latest phylogenetic analysis of the Zygoptera: this unique damselfly family today contains one relict species found in the wetlands of Australia. It was, however, very diverse and widespread during the Mesozoic. Nevertheless, very few species were known obscuring the origination and early evolution of the family. Here we propose a new stem hemiphlebioid taxon (Protohemiphlebiidae Zheng, Jarzembowski & Nel, fam. nov.) based on a new genus and two species: Protohemiphlebia zhangi Zheng, Jarzembowski & Nel, sp. nov. and Protohemiphlebia meiyingae Zheng, Jarzembowski & Nel, sp. nov. The new family shares the characters of both Hemiphlebiidae and Coenagrionoidea, but it is more closely related to Hemiphlebiidae in having the pterostigma with a ‘star-shaped’ microsculpture, and AA originating from the wing base slightly distal of Ax0. Protohemiphlebia Zheng, Jarzembowski & Nel, gen. nov. is further considered to belong to the stem group of Hemiphlebioidea, instead of belonging to the Hemiphlebiidae, in possessing pretibial combs and a weakly kinked RP1 below the Pt-brace. The new damselflies will help to calibrate the origin of Hemiphlebiidae, which could be earlier than their current oldest records in the Kimmeridgean (Late Jurassic).

New multipodomerous appendages of stem-group euarthropods from the Cambrian (Stage 4) Guanshan Konservat-Lagerstätte

Stem-group euarthropods are important for understanding the early evolutionary and ecological history of the most species-rich animal phylum on Earth. Of particular interest are fossil taxa that occupy a phylogenetic position immediately crownwards of radiodonts, for this part of the euarthropod tree is associated with the appearance of several morphological features that characterize extant members of the group. Here, we report two new euarthropods from the Cambrian Stage 4 Guanshan Biota of South China. The fuxianhuiid Alacaris ? sp. is represented by isolated appendages composed of a gnathobasic protopodite and an endite-bearing endopod of at least 20 podomeres. This material represents the youngest occurrence of the family Chengjiangocarididae, and its first record outside the Chengjiang and Xiaoshiba biotas. We also describe Lihuacaris ferox gen. et sp. nov. based on well-preserved and robust isolated appendages. Lihuacaris ferox exhibits an atypical combination of characters including an enlarged rectangular base, 11 endite-bearing podomeres and a hypertrophied distal element bearing 8–10 curved spines. Alacaris ? sp. appendages display adaptations for macrophagy. Lihuacaris ferox appendages resemble the frontal appendages of radiodonts, as well as the post-oral endopods of chengjiangocaridid fuxianhuids and other deuteropods with well-documented raptorial/predatory habits. Lihuacaris ferox contributes towards the record of endemic biodiversity in the Guanshan Biota.

Fossil evidence unveils an early Cambrian origin for Bryozoa

Bryozoans (also known as ectoprocts or moss animals) are aquatic, dominantly sessile, filter-feeding lophophorates that construct an organic or calcareous modular colonial (clonal) exoskeleton1–3. The presence of six major orders of bryozoans with advanced polymorphisms in lower Ordovician rocks strongly suggests a Cambrian origin for the largest and most diverse lophophorate phylum2,4–8. However, a lack of convincing bryozoan fossils from the Cambrian period has hampered resolution of the true origins and character assembly of the earliest members of the group. Here we interpret the millimetric, erect, bilaminate, secondarily phosphatized fossil Protomelission gatehousei9 from the early Cambrian of Australia and South China as a potential stem-group bryozoan. The monomorphic zooid capsules, modular construction, organic composition and simple linear budding growth geometry represent a mixture of organic Gymnolaemata and biomineralized Stenolaemata character traits, with phylogenetic analyses identifying P. gatehousei as a stem-group bryozoan. This aligns the origin of phylum Bryozoa with all other skeletonized phyla in Cambrian Age 3, pushing back its first occurrence by approximately 35 million years. It also reconciles the fossil record with molecular clock estimations of an early Cambrian origination and subsequent Ordovician radiation of Bryozoa following the acquisition of a carbonate skeleton10–13.

Tapered wedge stems decrease early postoperative subsidence following cementless total hip arthroplasty in Dorr type C femurs compared to fit-and-fill stems

Background: To compare the degree of stem subsidence between two different femoral component designs and to determine the risk factors associated with stem subsidence after cementless total hip arthroplasty (THA) in Dorr type C femurs. Methods: We retrospectively reviewed 91 consecutive hips in 87 patients with Dorr type C proximal femoral morphology who underwent primary cementless THA using a fit-and-fill stem or a tapered wedge femoral stem at our institution between January 2013 and June 2020. A fit-and-fill stem was used in 48 hips and a tapered wedge stem was used in 43 hips. Radiologically, the distance between the apex of the major trochanter and the stem shoulder were measured at three different time points (immediately [0W], one week [1W], and six weeks [6W] after surgery) and the degrees of stem subsidence were assessed by comparing the distance between 0W and 1W, 1W and 6W, and 0W and 6W, respectively. Results: The mean degree of stem subsidence (0W vs. 1W) was 0.25 mm (standard deviation [SD] 0.58) in the fit-and-fill stem group, and 0.24 mm (SD 0.43) in the tapered wedge stem group. There was no significant difference between the two groups (P = 0.4493). However, the mean degrees of subsidence were significantly higher in the fit-and-fill stem group (1W vs. 6W, 0.38 mm [SD 0.81]; 0W vs. 6W, 0.64 mm [SD 1.17]) than in the tapered wedge stem group (1W vs. 6W, 0.17 mm [SD 0.29]; 0W vs. 6W, 0.25 mm [SD 0.35]) (P < 0.05 for both). In addition, the rates of >3 mm subsidence (in which instability can be observed) were 16.7% (8 of 48 hips) and 2.3% (1 of 43 hips), respectively. There was also a significant difference between the two stems (P = 0.0324). Multivariate analysis demonstrated that higher age and fit-and-fill stem were risk factors for >3 mm subsidence after THA in Dorr type C femurs (P = 0.0396 and 0.0227, respectively). Conclusion: Our findings suggest that the tapered wedge stem is more suitable for Dorr type C femurs than the fit-and-fill stem to avoid early postoperative subsidence in cementless THA.

New species of Kamopanorpa Martynov from the Permian of South Siberia with comments on the systematic position of Microptysmatidae (Protomeropina = Permotrichoptera)

The systematic position of Microptysmatidae and Protomeropidae is critically reviewed in light of the latest reassessment by Minet et al. The Microptysmatidae belongs to a stem-group of Trichoptera, or at least to stem-Amphiesmenoptera (depending on chosen methodology), rather than to its own order Permotrichoptera as suggested by Minet et al., and Protomeropidae are not Mecoptera. The double anal loop of Kamopanorpa Martynov, 1928 is not significantly different from that of more advanced amphiesmenopterans, while in Microptysmella Kukalová-Peck & Willmann, 1990, anal veins show clear tendency to looping (not a “fairly different arrangement”). If Microptysmatidae are considered in the traditional way, the polarity of characters listed by Minet et al. as supporting monophyly of the order Permotrichoptera can be treated just the opposite: divided veins RS1, RS2 and M1 are symplesiomorphies with Protomeropidae, and simple M4 is the synapomorphy of Microptysmatidae, Cladochoristidae, and Amphiesmenoptera s. str. In addition, three new species of Kamopanorpa are described from the Permian deposits of Minusinsk Coal Basin, South Siberia: Kamopanorpa rasnitsyni sp. nov., K. sivchikovi sp. nov., and K. rotunda sp. nov. Some traits of fore- and hindwing venation of Microptysmatidae are discussed.

A partial skeleton of Septencoracias from the early Eocene London Clay reveals derived features of bee-eaters (Meropidae) in a putative stem group roller (Aves, Coracii)

A partial skeleton of the putative stem group roller Septencoracias is described from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK). With an age of about 55 million years, the bones represent one of the earliest fossil records of a coraciiform bird. The new fossil reveals that the proximal pedal phalanges of the three anterior toes of Septencoracias exhibit markedly widened distal ends. This distinctive trait is not found in other representatives of the Coracii, but occurs in the Meropidae (bee-eaters). The quadrate likewise exhibit a derived characteristic of the Meropidae, and the beak is narrower than in rollers. These previously unnoticed features are of particular interest, because the Meropidae result as the sister taxon of the Coracii in sequence-based analyses. Calibrated molecular data suggest that the divergence between the Coracii and the Meropidae occurred at 55.6 Ma, with the new fossil being only slightly younger than this date. However, phylogenetic analyses recovered Septencoracias within the Coracii, so that the derived features shared with the Meropidae most likely are either plesiomorphic and were lost in the Coracii, or they represent parallelisms that evolved convergently in Septencoracias and the Meropidae. In any case, these traits suggest that Septencoracias differed from extant rollers in its ecological preferences and foraging mode.

Sakhalinencyrtus leleji Simutnik gen. et sp. nov. of earliest Encyrtidae (Hymenoptera, Chalcidoidea) from Sakhalinian amber

Another earliest representative of the family Encyrtidae, Sakhalinencyrtus leleji Simutnik gen. et sp. nov., is described and illustrated based on a male specimen from the middle Eocene Sakhalinian amber. Similarly to other Encyrtidae from Sakhalinian amber, the new fossil fundamentally differs from encyrtids from late Eocene European ambers as well as from modern ones. Moreover, it probably belongs to a stem group of the family. The new genus is characterized by extremely apical position of cerci, long veins of the forewing with expanded parastigma, stigmal vein with long uncus, and absence of filum spinosum. The forewing venation of the new genus is very similar to that of Sugonjaevia Simutnik, 2015, but these genera differ by the structure of Mt8, hypopygium, genitalia, and clava.