Arthropods in amber from the Triassic Period

Abstract

The occurrence of arthropods in amber exclusively from the Cretaceous and Cenozoic is widely regarded to be a result of the production and preservation of large amounts of tree resin beginning ca. 130 million years (Ma) ago. Abundant 230 million-year-old amber from the Late Triassic (Carnian) of northeastern Italy has previously yielded myriad microorganisms, but we report here that it also preserves arthropods some 100 Ma older than the earliest prior records in amber. The Triassic specimens are a nematoceran fly (Diptera) and two disparate species of mites, Triasacarus fedelei gen. et sp. nov., and Ampezzoa triassica gen. et sp. nov. These mites are the oldest definitive fossils of a group, the Eriophyoidea, which includes the gall mites and comprises at least 3,500 Recent species, 97% of which feed on angiosperms and represents one of the most specialized lineages of phytophagous arthropods. Antiquity of the gall mites in much their extant form was unexpected, particularly with the Triassic species already having many of their present-day features (such as only two pairs of legs); further, it establishes conifer feeding as an ancestral trait. Feeding by the fossil mites may have contributed to the formation of the amber droplets, but we find that the abundance of amber during the Carnian ( ca. 230 Ma) is globally anomalous for the pre-Cretaceous and may, alternatively, be related to paleoclimate. Further recovery of arthropods in Carnian-aged amber is promising and will have profound implications for understanding the evolution of terrestrial members of the most diverse phylum of organisms.

Morphological support for a clade comprising two vermiform mite lineages: Eriophyoidea (Acariformes) and Nematalycidae (Acariformes)

“…Therefore, the paraphyletic status of Nematalycidae is tentative. But if Nematalycidae are paraphyletic, they would have to be older than the Eriophyoidea, which originated no later than the Triassic (c. 230 Ma) (Schmidt et al 2012;Sidorchuk et al 2015). Accordingly, the highly elongated body and unusual modes of locomotion (Bolton et al 2015b) of Nematalycidae would represent a relatively early departure from the primitive body form and mode of locomotion of Acariformes.…”

“…This lineage contains the largest family of mites (Eriophyidae >3,500 species), with new species being described at a much faster rate than for any other mite family (Liu et al 2013). Their species richness is explained, at least in part, by their high level of host specificity, but the relatively great age of this group may also be a contributing factor (Schmidt et al 2012;Sidorchuk et al 2015). All Eriophyoidea feed on the fluid contents of vascular plants.…”

“…However, a small number of eriophyoidlike fossils have been recovered from Triassic amber (Schmidt et al 2012;Sidorchuk et al 2015). Like extant Eriophyoidea, these mites have styliform chelicerae for feeding on the fluid contents of Eriophyoidea insofar as they are attenuated into styliform structures, and without reduction of the fixed digits.…”

A new genus and species of fairyfly, Tinkerbella nana (Hymenoptera, Mymaridae), with comments on its sister genus Kikiki, and discussion on small size limits in arthropods

“…In mites, the smallest adult individuals of several species in three families are less than 95 μm in length: Cochlodispus minimus Mahunka at 79 μm (Mahunka 1976) and Microdispus australis Mahunka at 82 μm (Mahunka 1969) (both Microdispidae), female of Indosetacus rhinacanthi Ghosh and Chakrabarti at 86 μm (Ghosh and Chakrabarti 1987), male of Eriophyes parvulus (Nalepa) at 90 μm (Nalepa 1892), both sexes of Achaetocoptes quercifolii Farkas at 90 μm (Farkas 1961) (all Eriophyidae), and females of Iponemus truncatus eurus Lindquist at 93 μm and I. confusus oriens (Lindquist and Bedard) at 94 μm (both Tarsonemidae) (Lindquist 1969). That small size in arthropods is not a recent evolutionary phenomenon is shown by a Triassic mite, Ampezzoa triassica Lindquist and Grimaldi (Eriophyidae), 124 μm in length (Schmidt et al 2012). Adults of Eriophyidae have only two pairs of usually 5-segmented legs yet they are evidently capable of locomotion but the legs are so reduced that they cannot lift the entire body off the substrate.…”

The oldest fossil biting midge (Diptera: Ceratopogonidae) from the Purbeck Limestone Group (Lower Cretaceous) of southern Great Britain

“…This Lower Cretaceous (Aptian) amber deposit is among the oldest with insect inclusions, with the exception of the recently reported 230 million year old Triassic amber from Italy, yielding one adult nematocerous Diptera (SCHMIDT et al 2012). Compression fossils of biting midges are relatively poorly known (HEYDEN 1870, COCKERELL 1921, STATZ 1944, probably because the incentive to study these fades when the awesome detail available in amber specimens is realized.…”