Permian parallelisms: Reanalysis of †Tshekardocoleidae sheds light on the earliest evolution of the Coleoptera

The Coleoptera provides an excellent example of the value of fossils for understanding the evolutionary patterns of recent lineages. We reevaluate the morphology of the Early Permian †Tshekardocoleidae to test alternative phylogenetic hypotheses relating to the Palaeozoic evolution of the order. We discuss prior interpretations and revise an earlier data matrix. Both Bayesian and parsimony analyses support the monophyly of Coleoptera excluding †Tshekardocoleidae (= Mesocoleoptera), and of Coleoptera excluding †Tshekardocoleidae and †Permocupedidae (= Metacoleoptera). Plesiomorphies preserved in †Tshekardocoleidae are elytra, which rest over the body in a loose tent-like manner, with flat lateral flanges, projecting beyond the abdominal apex, and abdomens that are flexible and nearly cylindrical. Apomorphies of Mesocoleoptera include shortening of the elytra and a closer fit with the flattened and probably more rigid abdomen. A crucial synapomorphy of Metacoleoptera is the tightly sealed subelytral space, which may have been advantageous during the Permian aridification. Taxon exclusion experiments show that †Tshekardocoleidae is crucial for understanding the early evolution of Coleoptera and that its omission strongly affects ancestral state polarities as well as topology, including crown-group taxa. By constraining the relationships of extant taxa to match those supported by phylogenomic analysis, we demonstrate that features shared by Archostemata with Permian stem groups are most reasonably supported as plesiomorphic and that the smooth and simplified body forms of Polyphaga, Adephaga, Myxophaga, and Micromalthidae were derived in parallel. Our study highlights the reciprocal illumination of molecular, morphological, and paleontological data, and paves the way for tip-dating analysis across the order.     

On the types of mesozoic archostematan beetles (Insecta, Coleoptera, Archostemata) in the Natural History Museum, London

About 40 type specimens of archostematan beetles from the Jurassic, Lower Cretaceous, and Paleogene of England, named by P. Brodie, J.O. Westwood, C. Giebel, A. Handlirsch, F. Zeuner, P. Whalley, and R. Crowson and stored in the Paleontological Department of the Natural History Museum (London) are redescribed. Nine genera and 11 species are recognized, three genera are assigned to Archostemata for the first time. One new species, Tersus crowsoni (Schizophoridae), is described.     

The first cupedine beetle from Burmese amber (Coleoptera: Cupedidae)

A rare archaic beetle, Mallecupes qingqingae gen. et sp. n., (Insecta: Coleoptera: Archostemata: Cupedidae) is described from mid-Cretaceous Burmese amber. It shows affinity with Paracupes found in South America today and ‘Paracupes’ found in North America during the Cretaceous. Archostemata are diverse in Burmese amber.     

How long can insect species exist? Evidence from extant and fossil Micromalthus beetles (Insecta: Coleoptera)

Six new fossils of Micromalthus (Coleoptera: Archostemata) from Dominican amber are compared with extant and previously described fossil micromalthid beetles. The amber inclusions are well preserved and all important morphological features are visible. Taking into account the morphological variability of the extant species Micromalthus debilis LeConte, 1878 , it is not possible to find any morphological features that distinguish the fossils from the extant species. This also applies to the Dominican amber inclusion described as Micromalthus anasi Perkovsky, 2008, which therefore is considered a junior synonym of M. debilis. The lack of morphological change in M. debilis over time might possibly be explained by unusually stable environmental conditions, as this species occupies a very specialized ecological niche in decaying timber. A general survey of fossil insects indistinguishable from extant species is presented. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158 , 300–311.     

Head structures of Priacma serrata Leconte (Coleptera, Archostemata) inferred from X-ray tomography

Internal and external features of the head of Priacma serrata were studied with X-ray microtomography and with histological methods. The comparison of both techniques shows that X-ray tomography is a promising new technique for the investigation of insect anatomy. The still somewhat coarse resolution of the X-ray data is compensated for by advantages like the nondestructive and artifact-free data acquisition. The head of P. serrata and other adults of Archostemata is characterized by many derived features. Muscular features of Priacma, especially muscles of the labium and pharynx, differ strongly from what is found in other groups of Coleoptera. Several character states are considered as autapomorphies of Archostemata: scale-like surface structures, constricted neck, strongly reduced tentorium, and the plate-like, enlarged prementum. The scales provide a protecting surface pattern and may have evolved with a more exposed lifestyle. The enlarged prementum forms a lid, which closes the mouth and covers the ligula when it is pulled back by contraction of the unusually strong submento-premental muscle. The presence of four cone-shaped protuberances on the dorsal side of the head is considered an autapomorphy of Cupedidae. The galea with a narrow stalk and a round and pubescent distal galeomere is another autapomorphy of this family. It has probably evolved as an adaptation to pollen-feeding. The shape of the mandible of Cupedidae is plesiomorphic compared to what is found in adults of Ommatidae. The vertical arrangement of apical teeth is an autapomorphy of the latter family. The lateral insertion of the antenna in Priacma is a groundplan feature of Cupedidae. The dorsal shift is a synapomorphy of all other cupedid genera. A cladistic analysis of characters of the head and additional data resulted in the following branching pattern: ((Crowsoniella + (Omma + Tetraphalerus)) + (Micromalthus + (Priacma + (Paracupes + (Cupes + Tenomerga + Prolixocupes + Rhipsideigma + Distocupes + (Adinolepis + Ascioplaga)))))).