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

Abstract

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.

The earliest beetle with mouthparts specialized for feeding on nectar is a parasitoid of mid-Cretaceous Hymenoptera

“…Kathirithamby et al [ 62 ] reject the conclusions presented in Beutel et al [ 61 ] and his colleagues, and report a third specimen of a conicocephalate larva (again belonging to a different species or even genus) from the Upper Cretaceous amber of Taimyr (Russia) as likely to be a strepsipteran larva. The Cretaceous Strepsiptera in Burmese amber are possibly a monophyletic lineage with four genera [ 22 ]. The general morphology of their larvae is identical with that of extant lineages and thus all three conicocephalate morphotypes are considered to be Ripiphoridae [ 22 , 63 ].…”

“…The Cretaceous Strepsiptera in Burmese amber are possibly a monophyletic lineage with four genera [ 22 ]. The general morphology of their larvae is identical with that of extant lineages and thus all three conicocephalate morphotypes are considered to be Ripiphoridae [ 22 , 63 ].…”

“…The mid-Cretaceous Burmese amber provides exceptionally well-preserved fossils of arthropods and other organisms, which offer excellent insights into the evolutionary history of particular insect groups (for review see, e.g., [ 22 ]. The representatives of Ripiphoridae found in Burmese amber are usually very well preserved and can be compared in great detail with their extant relatives.…”

“…Inclusions in Burmese amber in combination with fossils available from other Cretaceous amber deposits is an important source of taxonomic, bionomic, systematic and biogeographic data for Cretaceous Ripiphoridae and other groups of insects (e.g. [ 21 , 22 ]. Here we report a new genus and species of wedge-shaped beetle from Burmese amber and the first definite adult of a Cretaceous Ripiphorinae with elongated mouthparts adapted for feeding on nectar.…”

Fossils Shed a New Light on the Diversity and Disparity of the Family Limoniidae (Diptera, Nematocera)

“…Cretaceous ambers are of great value for paleoentomological research. We find there the inclusions of descendants of the Triassic and Jurassic fauna hitherto known only from imprints in sediments, as well as the first representatives of families and genera which dominate in recent fauna [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. Especially important is Burmese amber ( Figure 1 ), aged at the beginning of the Upper Cretaceous, Cenomanian (98.79 ± 0.62 Ma [ 9 ]).…”