New insects feeding on dinosaur feathers in mid-Cretaceous amber

Abstract

Due to a lack of Mesozoic fossil records, the origins and early evolution of feather-feeding behaviors by insects are obscure. Here, we report ten nymph specimens of a new lineage of insect, Mesophthirus engeli gen et. sp. nov. within Mesophthiridae fam. nov. from the mid-Cretaceous (ca. 100 Mya) Myanmar (Burmese) amber. This new insect clade shows a series of ectoparasitic morphological characters such as tiny wingless body, head with strong chewing mouthparts, robust and short antennae having long setae, legs with only one single tarsal claw associated with two additional long setae, etc. Most significantly, these insects are preserved with partially damaged dinosaur feathers, the damage of which was probably made by these insects' integument-feeding behaviors. This finding demonstrates that feather-feeding behaviors of insects originated at least in mid-Cretaceous, accompanying the radiation of feathered dinosaurs including early birds.

Fig. 1

AMBER No. 01 with the specimens of Mesophthirus engeli Gao, Shih, Rasnitsyn & Ren, gen. et sp. nov. from the mid-Cretaceous of Myanmar. a Photo of the whole feather and the locations of the insects, corresponding to the Supplementary Fig. 1. b–i Paratypic specimens CNU-MA2016001 to CNU-MA2016008. j Holotypic specimen CNU-MA2016009. k Parts of the feather show complete areas at basal part and adjacent largely damaged area between barbs. Representative, star in white referring to relatively complete barbules, star in blank referring to large areas of damages. Scale bars, 1 mm (a), 100 μm (b–j), and 0.5 mm (k).

Fig. 2

Holotype and paratypes of Mesophthirus engeli Gao, Shih, Rasnitsyn & Ren, gen. et sp. nov. within the AMBER No. 01 from mid-Cretaceous. a, b Holotype and line drawing of M. engeli sp. nov., CNU-MA2016009. c Enlargement of mouthpart of a shows details of mandible and maxillary palpi, arrows in white show teeth and arrows in green show the segments of palpi. d Paratype of M. engeli sp. nov., CNU-MA2016005, shows setae on the apex of antenna and single pretarsal claw. e, f Paratype and line drawing of M. engeli sp. nov., CNU-MA2016003, show spiracles on meso- and metanotum. g Paratype of M. engeli sp. nov., CNU-MA2016001, shows details of antennae, eyes, and spiracles on the side of abdominal segments, indicating the size scale of M. engeli sp. nov. with a feather barbule. h Paratype of M. engeli sp. nov., CNU-MA2016002, shows the two long stiff setae on the outsides of pretarsus. i Artist’s reconstruction of M. engeli sp. nov. of elder development stage feeding on the feather. It was reconstructed mainly based on the morphological characters of the holotype CNU-MA2016009, with supplemental consideration of CNU-MA2016001 and CNU-MA2016003. Colors of the insects are conjectural and referring to the general color of living feather-feeding lice. Scale bars, 50 μm.

Fig. 3

AMBER No. 02 with the paratype of Mesophthirus engeli Gao, Shih, Rasnitsyn & Ren, gen. et sp. nov. from the mid-Cretaceous of Myanmar. a Photo of the whole feather and the location of the insect. b Enlargement of the insect crawling on the feather. c Paratype of M. engeli sp. nov., CNU-MA2016010. d CNU-MA2016010 under green epifluorescence. e Line drawing of c. Scale bars, 1 mm (a), 0.1 mm (b–e).