A new genus and species of fossil moth, Miogeometrida chunjenshihi Zhang, Shih & Shih, gen. et sp. nov., assigned to Geometridae, is described from Miocene Dominican amber dating from 15–20 Mya. The new genus is characterized by the forewing without a fovea, R₁ not anastomosing with Sc, no areole formed by veins R₁ and Rs, R₁ and Rs₁ completely coincident, M₂ arising midway between M₁ and M₃, anal veins 1A and 2A fused for their entire lengths; and the hind wing with Rs running close to Sc + R₁ and M₂ absent.

chunjenshihi, Ennominae, extinct, fossil, taxonomy

Geometridae, the second most species-rich family of Lepidoptera, comprise approximately 24,000 described species (van Nieukerken et al. 2011; Murillo-Ramos et al. 2019). Geometridae are macrolepidopterans characterized by the presence of unique tympanal organs at the base of the abdomen, and the prolegs of their larvae reduced to two pairs causing the larvae to move by ‘looping’ (Minet and Scoble 1999). Geometridae were once classified into six subfamilies: Geometrinae, Ennominae, Sterrhinae, Larentiinae, Archiearinae and Oenochrominae sensu lato (Holloway 1994, 1996, 1997; Minet and Scoble 1999), but this classification was not fully satisfactory due to the fact that Oenochrominae sensu lato are a polyphyletic group (Scoble and Edwards 1990). Oenochrominae sensu lato were further divided into Oenochrominae sensu stricto, Desmobathrinae, Orthostixinae, and Alsophilinae, forming a classification system of nine subfamilies (Yamamoto and Sota 2007), but later Alsophilinae was subsumed in Ennominae (Wahlberg et al. 2010). Sihvonen et al. (2011) provided a comprehensive phylogeny of the Geometridae, and they found the previously recognized subfamilies to be monophyletic except the Oenochrominae + Desmobathrinae complex, which is a polyphyletic assemblage of taxa, and the Orthostixinae, which was positioned within the Ennominae. The systematic status of Orthostixinae remains uncertain, although Orthostixinae were synonymized with Desmobathrinae by Beljaev (2016). Systematic updates and annotated checklists of Western Palaearctic Geometridae were provided in "The Geometrid Moths of Europe" series (Hausmann 2001, 2004; Mironov 2003; Hausmann and Viidalepp 2012; Skou and Sihvonen 2015; Müller et al. 2019). Murillo-Ramos et al. (2019) established a new subfamily Epidesmiinae and transferred eight genera from Oenochrominae sensu stricto to Epidesmiinae.

The age of Geometroidea was calculated to trace back to 83 Mya (Wahlberg et al. 2013), and the age of Geometridae was estimated at ca 54 Mya (62–48 Mya, Yamamoto and Sota 2007). Recently, Kawahara et al. (2019) inferred a comprehensive phylogeny of Lepidoptera, and they dated the oldest members of the Lepidoptera crown group in the Late Carboniferous (ca 300 Mya), and speculated the ancestors of Geometroidea appeared in the Late Cretaceous. To date, 18 fossil records of Geometridae have been formally reported (Table 1). Harris and Raine (2002) reported a Late Cretaceous (Albian-Turonian, 113–89.8 Mya) lepidopterous genitalic fragment from New Zealand, and deemed its affinity probably lies within Geometridae, but Sohn et al. (2012) regarded the available characters insufficient to support a family-level diagnosis. The Eocene (56–33.9 Mya) species, Eogeometer vadens Fischer, Michalski & Hausmann, 2019, Geometridites larentiiformis Jarzembowski, 1980 and Hydriomena ? protrita Cockerell, 1922, respectively from the Baltic, UK, and USA, are believed to be the earliest representatives of Geometridae. However, most of the reported fossil geometrids are questionable. Evers (1907) assigned a specimen from Zanzibar Island to the extant genus Hyperythra and regarded this specimen as H. lutea, but Kozlov (1988) identified it as Geometridites sp. In addition, Phalaenites proserpinae Heer, 1861 was also considered as Geometridites sp. by Kozlov (1988). Lacking strong evidence, Sohn et al. (2012) disputed the Geometridae affiliation of Problongos baudiliensis Mérit & Mérit, 2008. Kusnezov (1941) treated Angerona electrina Giebel, 1862 as Macrolepidoptera incertae sedis. Grimaldi and Engel (2005) mentioned three specimens of Geometridae from Early Miocene Dominican amber (15–20 Mya), and provided pictures of these specimens.

Here we describe a new genus and species of Geometridae based on an adult specimen preserved in Dominican amber. The age of Dominican amber-bearing deposits is the late Early Miocene through early Middle Miocene, ca 15 to 20 Mya (Iturralde-Vinent and Macphee 1996). Dominican amber, with exquisite preservation, contains a very rich Miocene biota with more than 400 described insect species (Arillo and Ortuño 2005). To date, 30 fossil records within seven superfamilies of Lepidoptera have been reported in Dominican amber (Poinar et al. 1991; Poinar and Brown 1993; Hall et al. 2004; Grimaldi and Engel 2005; Peñalver and Grimaldi 2006; Sohn et al. 2012). All these fossil records belong to the lepidopteran clade Ditrysia.

The type specimen in amber described herein is housed in Laboratorio Dominicano De Ambar Y Gemas, Santo Domingo, Dominican Republic. The specimen was examined and photographed by using a Nikon SMZ 18 dissecting microscope with an attached Nikon DS-Ri2 digital camera system and a Leica M205A with an attached Leica DMC5400 digital camera system. These devices used cool white LED illuminators. Cool white transmitted light passed through the specimen from the bottom up, and cool white light, emitted from double optical fibers, irradiated the specimen from two sides simultaneously. Images were prepared for illustration using Adobe Photoshop CS6. Wing index is defined as the ratio of wing width/wing length. The body length was measured from the apex of head to the terminal end of abdomen. Family-level classification follows van Nieukerken et al. (2011). Wing venation nomenclature is based on Wootton (1979).

Miogeometrida gen. nov. can be assigned to Geometroidea based on forewing without spinarea (i.e., forewing-metathoracic aculeate locking device) and hind wing with basal part of the upper edge of discal cell markedly convex upwards, which are autapomorphies of the Geometroidea (Rajaei et al. 2015). In Geometroidea, the abdominal tympanal organ is an important diagnostic character, but the lateral and ventral parts of the abdomen of our specimen of Miogeometrida gen. nov. are damaged. It is thus impossible to determine whether a tympanal organ is present or not.

Although the essential apomorphy of Geometridae, i.e. a unique tympanal organ at the base of the abdomen, is not preserved for characterization, we chose to assign Miogeometrida gen. nov. to Geometridae. Based on the preserved and observable characters, Miogeometrida gen. nov. shows many similarities with Geometridae: (1) The size of Miogeometrida gen. nov. is in the common range of geometrids (wingspan ranges in most species from 20 to 45 mm; Heppner 2008a); (2) Hind wings of Miogeometrida gen. nov. are rounded as is the case in most species of Geometridae (Heppner 2008a); (3) Miogeometrida gen. nov. matches the major characters of geometrids in venation, such as forewing Rs₄ stalked with Rs₂ and Rs₃, M₂ not arising nearer to M₃ than M₁, and hind wing Sc bent strongly at its base (Minet and Scoble 1999). Although the first two similarities are also true for many other Lepidoptera, they can separate Miogeometrida gen. nov. from most sematurids and uraniids of Geometroidea.

We provide additional evidence to exclude three related Geometroidea families, i.e., Sematuridae, Uraniidae and Epicopeiidae. Sematuridae is a small family comprising only six extant genera and 40 species (van Nieukerken et al. 2011). An autapomorphy of Sematuridae are distally thickened antennae with swollen scape and elongate first flagellomere (Minet and Scoble 1999) – Miogeometrida gen. nov. does not have such an antenna. In addition, Miogeometrida gen. nov. with a wingspan of ca 20 mm, is obviously far smaller than sematurids whose wingspan range from 42 to 100 mm (Heppner 2008b). Moreover, Miogeometrida gen. nov. does not possess tails on the hind wings as found in most sematurids. In Uraniidae, the base of Rs₄ is connate or stalked with M₁, but separate from the other branches of Rs on the forewing, an apomorphy of the group (Minet and Scoble 1999). In Miogeometrida gen. nov., however, Rs₄ is stalked with Rs₂₊₃ on the forewing, which does not conform with the state in Uraniidae. Similarly, Miogeometrida gen. nov. can be distinguished from Epicopeiidae whose Rs₄ is never stalked with Rs₁ + Rs₂ + Rs₃.

Ennominae is the largest subfamily of Geometridae, comprising ca 10,000 species worldwide, classified in approximately 1100 genera (Pitkin 2002). Miogeometrida gen. nov. shows many similarities with some extant taxa. We assign Miogeometrida gen. nov. to Ennominae based on the absence of M₂ on its hind wing that is considered as the traditionally diagnostic feature for this subfamily (Holloway 1994, Pitkin 2002). However, we cannot assign the new genus to tribe, mostly due to the poor preservation of its detailed morphological characters.

We appreciate the valuable comments and constructive suggestions from Gunnar Brehm (editor), Pasi Sihvonen (reviewer) and one anonymous reviewer. This research was supported by grants from Natural Science Foundation of Hebei Province (No. D2020403002), State Key Laboratory of Palaeobiology and Stratigraphy (Nanjing Institute of Geology and Palaeontology, CAS) (No.183131), the National Natural Science Foundation of China (Nos. 31730087, 41688103), the Program for Changjiang Scholars and Innovative Research Team in University (No. IRT-17R75), and Project of High-level Teachers in Beijing Municipal Universities (No. IDHT20180518).