The earliest Timematids in Burmese amber reveal diverse tarsal pads of stick insects in the mid‐Cretaceous

Abstract

Many extant insects have developed pad structures, euplantulae or arolia on their tarsi to increase friction or enhance adhesion for better mobility. Many polyneopteran insects with euplantulae, for example, Grylloblattodea, Mantophasmatodea and Orthoptera, have been described from the Mesozoic. However, the origin and evolution of stick insects' euplantulae are poorly understood due to rare fossil records. Here, we report the earliest fossil records of Timematodea hitherto, Tumefactipes prolongates gen. et sp. nov. and Granosicorpes lirates gen. et sp. nov., based on three specimens from mid-Cretaceous Burmese amber. Specimens of Tumefactipes prolongates gen. et sp. nov. have extremely specialized and expanded euplantulae on their tarsomere II. These new findings are the first known and the earliest fossil records about euplantula structure within Phasmatodea, demonstrating the diversity of euplantulae in Polyneoptera during the Mesozoic. Such tarsal pads might have increased friction and helped these mid-Cretaceous stick insects to climb more firmly on various surfaces, such as broad leaves, wetted tree branches or ground. These specimens provide more morphological data for us to understand the relationships of Timematodea, Euphasmatodea, Orthoptera and Embioptera, suggesting that Timematodea might be monophyletic with Euphasmatodea rather than Embioptera and Phasmatodea should have a closer relationship with Orthoptera rather than Embioptera.

Cretaceous winged stick insects clarify the early evolution of Phasmatodea

“…Based on the results of our phylogenetic analyses (figure 1), Phasmatodea are corroborated to have a closer relationship with Embioptera than with Orthoptera, the apomorphies of Phasmatodea with Embioptera are as follows: antennifer well-defined (character 2: 1), prothorax without lateral extension (character 9: 1), trochanter fused with the femur (character 22: 1), media (M) of tegmina with two branches (character 43: 1), the branch location of M in behind of RP origin (character 44: 1), RP of hind wings unbranched (character 49: 1) and M of hind wings with two branches (character 51: 1). To date, stick insects from Myanmar (Burmese) amber have been described based on apterous adults and nymphs, and they are all recognized as true stick insects [4,[22][23][24]. Here, we described three winged adults for the first time, Pterophasma erromera gen. et sp.…”

“…All the known specimens of winged stick insects found before the mid-Cretaceous possessed long tegmina, such as Susumanioidea. Therefore, we suppose that the forewing shortening [4,22,23,24]. Whiting [11] documented that the loss and recovery of wings in stick insects should have happened many times during the course of evolution based on abundant molecular data.…”

“…Furthermore, Pterophasmatidae fam. nov. share some apomorphies with living groups: labrum emarginated [5,9,31], antennifer well-defined [5,8,9], metasternum and abdominal sternum I fused [5,[23][24][25], male with thorn pads in tergum X [5,14] and cerci unsegmented [5,8,32]. Therefore, Pterophasmatidae fam.…”

“…Stick insects have been documented in Dominican amber [16][17][18], Mexican amber [19], Baltic amber [20], Oise amber [21] and Myanmar (Burmese) amber [4,[22][23][24]. Most of these described amber species are wingless.…”

The oldest known mastotermitids (Blattodea: Termitoidae) and phylogeny of basal termites

“…They are from the mid‐Cretaceous (Grimaldi et al , ; Cruickshank & Ko, ; Ross, ). Many stem‐group insects have been found in this locality with evolutionary significance (Engel et al , ; Chen et al , ,b). Imago specimens were observed and photographed with a Nikon SMZ25 (CNU).…”