Palaeoentomology

Epibiont communities on mid-Cretaceous Burmese amber

YUAN-YUAN ZHANG, JUN-YE MA, DI-YING HUANG — Fri, 27 Jun 2025 00:00:00 +1200

The mid-Cretaceous Burmese amber was extensively colonized by marine epibiont communities, including pholadids, corals, oysters, and serpulids. In this study, we report a diverse array of marine organisms that adhered to the amber, forming epibiont communities. Notably, cheilostome bryozoans are documented for the first time as an additional group of colonizing organisms on Burmese amber. These bryozoans formed extensive sheets and proliferated on the amber surface, often encrusting other epilithic taxa such as serpulids and oysters. The encrusting organisms exhibited significant marginal competitive interactions, including overgrowth and stand-off behaviours, as they competed for space. These hard substrate communities display trends similar to those observed in extensive soft substrate communities, resembling many counterparts in both modern and geological records. This discovery provides valuable insights into the composition of epibionts, the sequence of their colonization, and their ecological interactions on Burmese amber. Furthermore, this study indicates that the establishment of epibiont communities on Burmese amber occurred later than the entrapment of bioinclusions but earlier than the deposition of nearshore gravel strata.

**Redescription and systematic affinities of Moltenia rieki Schlüter, 2000 (Xyelidae: Archexyelinae) (Molteno Formation, South Africa), one of the rare Gondwanan Triassic Hymenoptera**

NOZOMU OYAMA, TORSTEN WAPPLER, JOHN M. ANDERSON, OLIVIER BÉTHOUX — Fri, 27 Jun 2025 00:00:00 +1200

Using Reflectance Transformation Imaging, we re-examined the holotype of Moltenia rieki Schlüter, 2000, one of the few Triassic Hymenoptera known from Gondwana. The new data revealed characters of venation which were overlooked and/or misapprehended in the original description, and which have putative systematic relevance. Notably, the branching point of Rs, previously assumed to be located in a distal position, is actually located basal to the 2r-rs cross-vein, a trait suggesting a placement within the subfamily Archexyelinae. In combination with other traits, such as a very short 1-Rs and a fully sclerotized pterostigma, Moltenia rieki stands out as a distinctive member of this taxon. This study broadens our knowledge of early Hymenoptera evolution and suggests a wide Triassic distribution for Archexyelinae.

**Expanding diversity of Acalyptratae (Diptera) in the Eocene Baltic amber forest: new species of Acartophthalmites (Clusiomitidae) and Protanthomyza (Protanthomyzidae stat. nov.)**

JINDŘICH ROHÁČEK — Fri, 27 Jun 2025 00:00:00 +1200

Four new fossil species from two families of Acalyptratae (Diptera), all preserved in Baltic amber (Eocene, 48–34 Ma), are described: Acartophthalmites bicolor sp. nov., A. scotopteryx sp. nov., A. striatus sp. nov. (all Clusiomitidae), as well as Protanthomyza chelicerata sp. nov. (Protanthomyzidae). All new species are diagnosed, illustrated, and their relationships are discussed. Updated identification keys are provided. Based on newly acquired morphological data, the relationships of the subfamily Protanthomyzinae (formerly within Anthomyzidae) are revised. Since this fossil taxon is recognized as the sister group of Anthomyzidae (s. str.) (= without Protanthomyzinae) +Opomyzidae,, this group is elevated to the rank of a family, Protanthomyzidae stat. nov. The addition of four new species contributes to the knowledge of the diversity of Acalyptratae flies in the Eocene Baltic amber forest, even though they belong to extinct families.

Is fossil insect taxonomy compatible with database-based research?

Fri, 27 Jun 2025 00:00:00 +1200

The lack of veracity in assignments of fossil insects to generic and even higher taxonomic levels has been a well-recognized problem since the late 19^th century. This is of course partly a function of the lack of well-preserved morphological detail in fossils, but also to a misplaced sense of the need to assign generic and specific names–that specimens not assigned genus and species names are somehow of less value than those that are. In the present review, the early history of paleoentomological assignments is reviewed, including the origin and use of “Open nomenclature” and other attempts by authors to indicate a degree of inaccuracy in their identifications. Numerous examples are provided, both old and recent, as the problem of incorrect taxonomic assignments persists. Public databases are of increasing importance to the field of paleoentomology, but the numerous inaccuracies in the primary literature have often been transferred directly to the databases. In many cases, original attempts to suggest degrees of inaccuracy are not countenanced. The advent of database-based research is particularly susceptible to the burden of incorrect taxonomic assignments. We suggest changes in the way that databases record indications of uncertainty but recognize that it is not the responsibility of database managers to ascertain these inaccuracies. Every scientist in the field is obligated to correct inaccurate assignments and to assign, where necessary, previously named specimens to incertae sedis. We submit that the field must recognize that a specimen identified to, at some level, incertae sedis, can be as valuable to science as those that are assigned valid and well supported taxonomic assignments.

**A new wireworm-like larva (Coleoptera, Elateridae incertae sedis) from about 100 million year-old Kachin amber with a very stout antenna**

JOACHIM T. HAUG, PATRICK MÜLLER, CAROLIN HAUG — Fri, 27 Jun 2025 00:00:00 +1200

Beetle larvae are ubiquitous in the modern-day fauna, and we can expect that this was not very different in many past ecosystems. Yet, the literature on fossil beetle larvae is still comparably scarce. Here we report a larva with a wireworm-like morphology from about 100 million years old Kachin amber, Myanmar. The larva represents the third type of larvae that shares characters with modern larvae of Elateridae, the group of click beetles. However, it also possesses an unusual feature, a bulbous trunk end. Such a structure is well known in modern larvae of some ingroups of Elateridae such as Cebrioninae, Elaterini, and Agriotini, and to a certain degree also Dicrepidiini, Physorhinini, and Ampedini. The new fossil is different in the morphology of the antennae and palps, which are short, rather stout, and cone-shaped, being broader than those of any of the modern counterparts.

Evolutionary development revealed in discovery of the earliest Saldinae (Heteroptera: Leptopodomorpha: Saldidae) in Cretaceous amber from Myanmar

MAO ZHANG, DONG REN, YUN-ZHI YAO — Fri, 27 Jun 2025 00:00:00 +1200

A new genus and species of shore bugs, Exornatum sulcatum gen. et sp. nov., is identified as the oldest Mesozoic member of the subfamily Saldinae from mid-Cretaceous Kachin amber in Myanmar. This discovery indicates that the Saldinae may have originated in the Cretaceous, a key phase in the subfamily-levels evolutionary radiation of the Saldidae. We also observe and discuss variations in the hemelytra veins of the new and the known species, enhancing our understanding of the early origins and evolution of saldids in the Mesozoic.

**The oldest known Cardiocondyla ant (Hymenoptera, Formicidae) from the late Eocene Rovno amber (Ukraine)**

ALEXANDER RADCHENKO, MYKOLA KHOMYCH — Fri, 27 Jun 2025 00:00:00 +1200

A new fossil species of the ant genus Cardiocondyla Emery, 1869, C. primitiva sp. nov., is described based on a winged gyne from the late Eocene Rovno amber (Ukraine, 37.8–33.9 Ma). It is the first Cardiocondyla found in the late Eocene European ambers, and the earliest known record of this genus. Most features of C. primitiva sp. nov. fit the modern diagnosis of Cardiocondyla. However, it is clearly distinguished from all known modern congeners by its much more developed forewing venation. In particular, the cells mcu, 1+2r and 3r are closed and the free branches 4+5RS and 2+3+4M are well developed, whereas forewing in modern species has only one closed cell 1+2r, and the free branches 4+5RS and 2+3+4M are strongly or completely reduced. The discovery of C. primitiva sp. nov. pushes the date of the earliest known fossil Cardiocondyla back at least 18 million years, and may force a reconsideration of its phylogenetic relationship with other Myrmicinae genera.

Towards a time-tree solution for Branchiopoda diversification: a jackknife assessment of fossil age priors

NICCOLÒ RIGHETTI, FILIPPO NICOLINI, GIOBBE FORNI, ANDREA LUCHETTI — Fri, 27 Jun 2025 00:00:00 +1200

An understanding of Branchiopoda’s evolutionary history is crucial for a comprehensive knowledge of the Pancrustacea tree of life, given their close evolutionary relationship with Hexapoda. Despite significant advances in molecular and morphological phylogenetics that have resolved much of the branchiopod backbone topology, a reliable temporal framework remains elusive. Key challenges include a sparse fossil record, long-term morphological stasis, and past topological inconsistencies. Leveraging a Bayesian Inference approach and the most extensive phylogenomic dataset for branchiopod to date, encompassing 46 species and over 130 genes, we inferred a time-calibrated phylogenetic tree. Furthermore, to strengthen the confidence in our divergence times estimation, we assessed the impact of age priors, topological uncertainties, and gene trees which are discordant from the species trees. Our results are largely consistent with the fossil record and with previous studies, indicating that Branchiopoda originated between 400 and 500 million years ago, and the orders of large branchiopods diversified during the Mesozoic. Concerning Cladocera, results remain problematic, with a sharper uncertainty in the diversification time with respect to the fossil record. Though, the jackknife resampling of fossils and the other sensitivity analyses proved our calibration method to be robust, suggesting that the difficulties in obtaining a paleontological-consistent time tree may be hindered by the variability in branchiopod substitution rates and topological instability within certain clades.

A new arceotermitid species from mid-Cretaceous Kachin amber (Isoptera: Teletisoptera)

CORENTIN JOUAULT, RU SMITH, MICHAEL S. ENGEL — Mon, 30 Jun 2025 00:00:00 +1200

The mid-Cretaceous termite genus Arceotermes Engel & Jiang (Arceotermitidae) has hitherto been known from a single species in Kachin amber (Myanmar). Here we report a second species, which is described and figured as Arceotermes bellator sp. nov., permitting an emendation of the generic diagnosis. The new species is distinguished from the type species by mandibular dentition and number of antennomeres. We discuss its systematic placement in detail, and propose of brief summary of the defensive strategy used by termite soldiers during the mid-Cretaceous.

Newly discovered ammonites in mid-Cretaceous Burmese amber

Mon, 30 Jun 2025 00:00:00 +1200

Amber is famous for preserving detailed records of terrestrial and soft-bodied organisms that have a low preservation potential elsewhere in the fossil record. Because preservation in amber is biased toward animals such as insects that live in close association with resin-producing trees, inclusions of marine fossils in Mesozoic amber are extremely rare. Here, we report unusual fossil assemblages consisting of ammonites preserved alongside terrestrial arthropods in Burmese amber. Under X-ray microcomputed tomography (CT), we made detailed observations of the preserved septa and sutures in the ammonite samples. On the basis of the suture structure, moderately involute shell, and smooth shell surface without ornamentation, we classified one of the new ammonites within the superfamily Desmoceratoidea. The partial filling of shell chambers with calcite suggests that the ammonites were buried for a short time in the sediment, which started the fossilization process prior to encapsulation in resin. Sand infills within the shell chambers indicate significant weathering and transport within a high-energy environment prior to encapsulation. The arthropod inclusions are represented by terrestrial and possibly aquatic associated forms belonging to Acari (mites); Hemiptera: Cimicomorpha: Vetanthocoridae; and Diptera: Muscomorpha. These insects are surrounded by powdered wood, insect frass, and plant fragments. The combined fossil assemblage seems to suggest that at least some amber-producing trees grew close to the coast, capturing a mixture of forest floor communities and partially fossilized shells redeposited from high-energy coastal waters.