Two new species of mid-Cretaceous webspinners in amber from northern Myanmar (Embiodea: Clothodidae, Oligotomidae)
Introduction
The insect order Embiodea (also known as Embioptera or Embiidina), is one of the smaller polyneopterous lineages, with approximately 400 living species distributed throughout the world, although the real diversity of the group is significantly greater (Ross, 1991, Ross, 2000a). Commonly referred to as webspinners, species spin silk from glands within their swollen probasitarsi, and this silk is used to construct galleries within which individuals live gregariously (Grimaldi and Engel, 2005, Ross, 2000b). Species are slender with females generally paedomorphic and therefore apterous, while males are typically winged. Other distinguishing features of the order include the combination of a prognathous head that is usually closed ventrally by a ventral bridge or gula (but see below); a reduced mentum and large submentum; absence of ocelli; filiform antenna; trimerous tarsi; enlarged metafemur with greatly developed metatibial depressors; plantulae typically present on metatarsomeres I and II; homonomous and dehiscent wings with ‘blood sinuses’ formed around R, Cu, A, and sometimes Sc; abdomen 10-segmented; male terminalia often asymmetrical; ovipositor vestigial; and cerci frequently dimerous (Boudreaux, 1979, Engel and Grimaldi, 2006, Grimaldi and Engel, 2005, Ross, 1970, Ross, 1991). Resolving relationships both of and within the order has been a challenge, and the sundry numerical attempts have revealed that considerable paraphyly or even polyphyly exists throughout the group (e.g., Miller et al., 2012, Szumik, 1996, Szumik et al., 2008). The family Clothodidae, usually recovered as monophyletic, is often considered the earliest diverging of the living lineages (e.g., Davis, 1940, Miller et al., 2012, Ross, 1970, Ross, 1987, Ross, 2000a, Szumik, 1996, Szumik et al., 2008), but even this notion has been challenged and Australembiidae may represent the living sister group to other Embiodea (e.g., Klass and Ulbricht, 2009, Miller et al., 2012). While Embiodea is consistently monophyletic, their placement among Polyneoptera waivers between support for the Mystroptera (Zoraptera + Embiodea) or the Eukinolabia (Phasmatodea + Embiodea) (e.g., Beutel and Gorb, 2006, Boudreaux, 1979, Engel and Grimaldi, 2000, Grimaldi and Engel, 2005, Ishiwata et al., 2011; ; Letsch and Simon, 2013, Rähle, 1970, Rafael and Engel, 2006, Terry and Whiting, 2005, Yoshizawa, 2007, Yoshizawa, 2011). It is clear that considerable work remains to be undertaken concerning the systematics and biology of Embiodea before a consistent system can be developed.
Perhaps not surprisingly given their life history, Embiodea are poorly represented in the fossil record. Virtually all of those species known are documented from inclusions in amber, as well as a subfossil species, Oligotoma westwoodi Hagen, in Pleistocene copal from East Africa and likely synonymous with an extant species (Hagen, 1885: note that this species was referred to by Hagen, 1866; but not named or described at that time). Species have been discovered in the lower Miocene amber of the Dominican Republic (Ross, 2003, Szumik, 1994, Szumik, 1998), the middle Eocene amber of the Baltic region (Pictet, 1854, Ross, 1956), the lower Eocene amber of India (Engel et al., 2011, Rust et al., 2010), and the mid-Cretaceous amber of northern Myanmar (Cockerell, 1919, Davis, 1939a, Engel and Grimaldi, 2006). In addition to these, a compression fossil of a poorly understood species of a putative embiid has been described from the Eocene-Oligocene shales of Florissant, Colorado (Cockerell, 1908, Ross, 1984). Two further compression fossils have been described as stem-group Embiodea from the middle Jurassic deposits of Inner Mongolia, China (Huang & Nel, 2009). Given the scarcity of material, fossils have factored little in attempts to resolve relationships within the order. Nonetheless, given their specialized biology and morphology, particularly the case for the wholly neotenic females, fossil taxa are likely to represent a critical source of information for revealing the historical biogeography and phylogeny of the webspinners. In this context, the discovery and description of any new fossil species is of importance for expanding the available data and from which to ultimately establish broader patterns and explanations (e.g., Grimaldi & Engel, 2007).
Herein we report two new genera and species of mid-Cretaceous webspinners. Both species are preserved in the amber of northern Myanmar, but differ dramatically from Burmitembia venosa Cockerell, 1919 and Sorellembia estherae Engel & Grimaldi, 2006 from the same deposit. The former known species are of the Burmitembiinae (Notoligotomidae) and Sorellembiinae (Pachylembiidae), while the new fossils are representative of the Clothodidae and Oligotomidae, respectively.
Section snippets
Material and methods
The morphological terminology employed for the descriptions is generally that outlined by Ross (2000a) for the order, while the format follows that of Engel et al. (2011). We have followed the general indications of the higher classification suggested by the studies of Ross, 1970, Ross, 2000a, Szumik, 1996, and Miller et al. (2012). The material originates from the Hukawng Valley in northern Myanmar (Cruickshank and Ko, 2003, Grimaldi et al., 2002), and generally considered of earliest
Systematic palaeontology
Order: Embiodea Kusnezov, 1903.
Suborder: Clothododea Engel & Grimaldi, 2006.
Infraorder: Clothodomorpha Engel and Huang, nov.
Family: Clothodidae Enderlein, 1909.
Subfamily: Atmetoclothodinae Engel and Huang, subfam. nov.
Type genus. Atmetoclothoda Engel and Huang, gen. nov.
Diagnosis. Male: Head with postoccipital suture continuous, extending anteriorly on ventral of head to meet hypostomal carina at posterior tentorial pit near posterolateral corners of submentum; ventral bridge lacking, thus
Discussion
The two new genera described herein expand considerably the known fossils of webspinners, doubling the available Cretaceous records and adding two more families to those known from this period. Interestingly, all of the Cretaceous fossils are from Burmese amber (Cockerell, 1919, Engel and Grimaldi, 2006), highlighting the importance of this deposit for understanding mid-Cretaceous insect life. The discovery of putatively primitive species of Clothodidae and Oligotomidae extend the record of
Concluding remarks
As we have documented here, there is a growing diversity of webspinners known from the fossil record and the two genera described double the number of lineages previously known from the Cretaceous. This diversity now includes the primitive Clothodidae, the first of its kind known as fossils as well as from the Eastern Hemisphere, and the earliest occurrence of the Oligotomidae. It is hoped that continued attention to Mesozoic deposits will bring forth additional Embiodea, and that in time a
Acknowledgements
The work of D.-Y.H. has been supported by grants from the National Basic Research Program of China (2012CB821903), the Outstanding Youth Foundation of Jiangsu Province (BK 2012049), and the National Natural Science Foundation of China (91114201). The participation of L.C.V.B. and M.S.E. was partially supported by U.S. National Science Foundation grant DEB-1144162 (to M.S.E.). We are grateful to two anonymous reviewers for their helpful comments on the manuscript. We dedicate this paper to
References (56)
- et al.
Phylogenetic relationships among insect orders based on three nuclear protein-coding gene sequences
Molecular Phylogenetics and Evolution
(2011) - et al.
The female genitalic region and gonoducts of Embioptera (Insecta), with general discussions on female genitalia in insects
Organisms Diversity and Evolution
(2009) - et al.
Age constraint on Burmese amber based on U-Pb dating of zircons
Cretaceous Research
(2012) The higher classification of the order Embioptera: a cladistic analysis
Cladistics
(1996)- et al.
A revised interpretation of the evolution of attachment structures in Hexapoda with special emphasis on Mantophasmatodea
Arthropod Systematics and Phylogeny
(2006) Arthropod phylogeny with special reference to insects
(1979)Descriptions of tertiary insects, II
American Journal of Science
(1908)Two interesting insects in Burmese amber
Entomologist
(1919)- et al.
Geology of an amber locality in the Hukawng Valley, northern Myanmar
Journal of Asian Earth Sciences
(2003) Taxonomic notes on the order Embioptera. III. The genus Burmitembia Cockerell
Proceedings of the Linnean Society of New South Wales
(1939)
Taxonomic notes on the order Embioptera. IV. The genus Clothoda Enderlein
Proceedings of the Linnean Society of New South Wales
Taxonomic notes on the order Embioptera. XX. The distribution and comparative morphology of the order Embioptera
Proceedings of the Linnean Society of New South Wales
Die Klassifikation der Embiiden, nebst morphologischen und physiologischen Bemerkungen, besonders über das Spinnen deselben
Zoologischer Anzeiger
New earwigs in mid-Cretaceous amber from Myanmar (Dermaptera, Neodermaptera)
ZooKeys
A winged Zorotypus in Miocene amber from the Dominican Republic (Zoraptera: Zorotypidae), with discussion on relationships of and within the order
Acta Geológica Hispánica
The first Mesozoic Zoraptera (Insecta)
American Museum Novitates
A primitive earwig in Cretaceous amber from Myanmar (Dermaptera: Pygidicranidae)
Journal of Paleontology
The earliest webspinners (Insecta: Embiodea)
American Museum Novitates
Diverse Neuropterida in Cretaceous amber, with particular reference to the paleofauna of Myanmar (Insecta)
Nova Supplementa Entomologica
New mid-Cretaceous earwigs in amber from Myanmar (Dermaptera)
Novitates Paleoentomologicae
Primitive termites from the Early Cretaceous of Asia (Isoptera)
Stuttgarter Beiträge zur Naturkunde
Webspinners in Early Eocene amber from western India (Insecta, Embiodea)
ZooKeys
Evolution of the insects
Why descriptive science still matters
BioScience
Fossiliferous Cretaceous amber from Myanmar (Burma): Its rediscovery, biotic diversity, and paleontological significance
American Museum Novitates
Strepsiptera and triungula in Cretaceous amber
Insect Systematics and Evolution
Psocinorum et Embidinorum synopsis synonymica
Verhandlungen der Kaiserlich-Königlichen Zoologisch-Botanischen Gesellschaft in Wien
Monograph of the Embidina
Canadian Entomologist
Cited by (12)
A new plesiomorphic species of webspinner (Embiodea, Clothodidae) from mid-Cretaceous Kachin amber of northern Myanmar
2023, Journal of Asia-Pacific EntomologyNew data on embiids (Insecta: Embiodea) from mid-Cretaceous Burmese amber, with description of new genus and two new species
2022, Cretaceous ResearchCitation Excerpt :Enantiornithine birds (named “opposite birds”) (Zelenkov, 2017; Perkovsky et al., 2019) probably did not play an important role in the biological control of the Cretaceous webspinners because of their manner of eating (named “cranioinertial”, i.e., once the food is taken with the beak, the head and neck are rapidly thrusted backwards and the beak is simultaneously opened, releasing the prey) (Perkovsky et al., 2020a). Cranioinertial feeding would have been an obstacle for consuming small (less than 10 mm) arboreal insects (most opposite birds were arboreal), and nine of the eleven described Burmese species of webspinners are very small (Engel and Grimaldi, 2006; Engel et al., 2016; Cui et al., 2020; Lai et al., 2022; this paper). Enantiornithine birds would likely have been feeding on the large webspinners, which, however, would have been protected by their moderately-sized silk webs.
New webspinners (Insecta: Embioptera) from Upper Cretaceous amber of northern Myanmar
2022, Cretaceous ResearchNew species of webspinners (Insecta: Embiodea) from mid-Cretaceous amber of northern Myanmar
2020, Cretaceous ResearchCitation Excerpt :Several species have been recorded from Miocene amber of the Dominican Republic (Szumik, 1994, 1998; Ross, 2003), a single species in Eocene amber of the Baltic region (Ross, 1956), and a single species in Eocene amber from northwestern India (Engel et al., 2011). Presently, four species of Embiodea are documented from the Cretaceous, and all of these are from Burmese amber: Burmitembia venosa Cockerell (Notoligotomidae: Burmitembiinae), Sorellembia estherae Engel & Grimaldi (Scelembiidae: Sorellembiinae), Litoclostes delicatus Engel & Huang (Oligotomidae), and Atmetoclothoda orthotenes Engel & Huang (Clothodidae: Atmetoclothodinae) (Cockerell, 1919; Davis, 1939; Engel & Grimaldi, 2006; Engel et al., 2016). Herein we report a further three Cretaceous species in two genera, all of which have comparatively simplified male terminalia, in which the sclerites are generally symmetrical and with an undivided tenth tergum, typical of the family Clothodidae (Ross, 1987) (also found in the neotenic, apterous family Paedembiidae of Central Asia: Ross, 2006; Gorochov & Anisyutkin, 2006; Blyummer, 2017).
A thorny, 'anareolate' stick-insect (Phasmatidae s.l.) in Upper Cretaceous amber from Myanmar, with remarks on diversification times among Phasmatodea
2016, Cretaceous ResearchCitation Excerpt :These Burmese amber mines have yielded thousands of fossils of earliest Cenomanian age (Shi et al., 2012), and represent one of the richest and oldest sources for paleobiological information on the Upper Cretaceous. The locality has been extensively studied and mapped by Grimaldi et al. (2002) and Cruickshank and Ko (2003), and the biotic diversity, largely comprising insects, has been tabulated by Grimaldi et al. (2002) and Ross et al. (2010), but with numerous important additions subsequent to these works that have expanded the crustacean (Broly et al., 2015), arachnid (Engel and Grimaldi, 2014a; Engel et al., 2016a), and insect records (e.g., Grimaldi and Engel, 2013; Barden and Grimaldi, 2014, 2016; Dikow and Grimaldi, 2014; Engel and Grimaldi, 2014b; Grimaldi and Johnston, 2014; Arillo et al., 2015; Parker and Grimaldi, 2014; Vea and Grimaldi, 2015; Delclòs et al., 2016; Engel et al., 2016b, 2016c, 2016d, 2016e, 2016f; Yamamoto, 2016). The classification of Phasmatodea is rather muddled, with much comparative morphological investigation and revision necessary before a robust, stable system is achieved.