New Jersey Amber Mayflies: the First North American Mesozoic Members of the Order (Insecta; Ephemeroptera)

New Jersey amber mayflies: the first North American Mesozoic members of the order (Insecta; Ephemeroptera) Nina D. Sinitshenkova Paleontological Institute ofthe Russian Academy ofSciences, Profioyuznaya Street 123, Moscow 117647, Russia Abstract The following new genera and species of mayflies are described from Upper Cretaceous (Turonian) amber from Sayreville, New Jersey, U.S.A: Cretomitarcys lu=ii (imago male), (Polymitarcyidae: Cretomitarcyinae, new subfamily), Borephemera goldmani (imago male, Australiphemeridae), Amerogenia macrops (imago female) (Heptageniidae) and Palaeometropus cassus (subadult male) (Ametropodidae). Previously no mayflies were described from the Mesozoic of North America. Ametropodidae and Heptageniidae are newly recorded for the Mesozoic, and Australiphemeridae for the Upper Cretaceous. The mayflies in this amber probably inhabited a medium-sized or large river. Zoogeography of Upper Cretaceous mayflies is briefly discussed; with particular emphasis on significant faunistic differences between the temperate and subtropical areas. Introduction often abundant in drift of modern rivers, lotic nymphs seem to be very rare in the fossil record Through the kindness of Dr. D. Grimaldi like other insects inhabiting running waters (Department of Entomology, American Museum (Zherikhin, 1980; Sinitshenkova, 1987). The of Natural History, New York) I have had an alate mayflies are extremely short-lived, and the opportunity to examine five mayfly specimens probability is quite low of an occasional burial for found among a large collection of fossil insects the flying stages of a lotic species in lake sedi enclosed in Late Cretaceous amber of New Jersey. ments. Thus, probably the largest part of past This material is interesting and important in sev mayfly diversity became lost as a result of eral respects. taphonomy. In contrast, the winged stages of The fossil record of mayflies is rather good in mayflies are not rare in fossilized resins, and in comparison to many other insect orders, and this case lotic species seem to be represented many extinct taxa have been named (Hubbard, much better. Both subadult and adult mayflies 1987). The mode of mayfly burial and preserva often rest at tree trunks, where they can be easily tion as fossils has never been a subject of special trapped by and entirely engulfed by liquid resin. study but undoubtedly the remains of nymphs Taphonomy of the Sayreville, New Jersey amber and nymphal exuvia of lentic species constitute deposit indicates that the amber was deposited the bulk of the material. It is not surprising very close to the source and in a deltaic environ because ancient lake sediments provide the main ment with deep sands, clays, and organic debris, source of information on fossil insects in general. including wood. Resin is easily transported by However, the lacustrine assemblages of mayflies flowing rivers along with drift wood and bark. are usually poor in species, and many families Also, lotic insects are rather common among seem to be unrepresented or at least strongly amber inclusions (Ulmer, 1912; Wichard and underrepresented. Though mayfly nymphs are Weitschat, 1996). Thus mayflies enclosed in Studies on fossils in amber, with particular reference to the Cretaceous ofNew Jersey, pp. 111-125 Edited by David Grimaldi © 2000 Backhuys Publishers, Leiden, The Netherlands 112 ND. Sinitshenkova amber may compensate for the most significant Cretaceous deposits, mainly lacustrine, of Asia bias in the rock fossil record of the order. (Zherikhin, 1978), Europe (Martinez-Deldos, Up to now mayflies inclusions in amber have 1991), Australia (Jell and Duncan, 1986), and been recorded from the Upper Cretaceous of South America (McCafferty, 1990). It can prob Taymyr Peninsula, North Siberia (Tshernova, ably be explained as a result of the large-scale 1971; Kluge, 1993, 1997); from the Eocene extinction of typical Mesozoic lacustrine biota Baltic amber, Europe (Larsson, 1978; Kluge, near the Early/Late Cretaceous boundary 1993; Wichard and Weitschat, 1996); Fushun (Zherikhin, 1978; Sinitshenkova, 1987). amber, China (Hong, 1979); from the Oligocene A comparison between mayfly faunas of the and Miocene ambers of the Dominican Republic Taymyr and New Jersey ambers is especially (Poinar, 1992) and Chiapas, Mexico (Wichard interesting because both assemblages, probably and Weitschat, 1996), as well as from the very comparable in taphonomic respect, origi Saxonian amber (Wichard and Weitschat, 1996), nate from very different climatic regions of the but they have been only partially described and a Late Cretaceous. Paleobotanically, it is well few are named. A single mayfly inclusion is dis demonstrated that at this time the Taymyr area covered in the collection of apparently was situated within the East Siberian paleofloris Cretaceous Burmese amber in the Natural tic province of the temperate Siberian-Canadian History Museum, London (Sinitshenkova, realm, possibly even northwards of the polar cir 2000). A mayfly from the New Jersey Late cle, while New Jersey lay within the Potomac Cretaceous amber, from the same deposit as the province of the subtropical Euro-Chinese realm material described here, has been mentioned by (Vakhrameev, 1988). Thus the discovery of Gelhaus and Johnson (1996). mayflies in the New Jersey amber opens the door The taxa described below are the first North to studies in Late Cretaceous mayfly paleozoo American Mesozoic mayflies known. Moreover, geography. up to now the mayflies from the Taymyr amber All five specimens in hand are enclosed in the were the only named Late Cretaceous mayflies. transparent yellow substance described by Few mayfly fossils have been discovered in Grimaldi et aL (1989) as the second type of the Cenomanian tuffaceous mudstones at New Jersey amber. They are rather well preserved Obeshchayushchy Creek in the Magadan Region and identifiable. The specimen mentioned by and in Cenomanian or T uronian days at Gelhaus and Johnson (1996) was not available Timmerdyakh-Khaya in Jakutia, Russia as well as for study. in Turonian clays at Kzyl-Dzhar, Kazakhstan The mayfly classification system below is in (Zherikhin, 1978) but the nymphal remains accordance with McCafferty (1991), and Wang from these sites are poorly preserved and unde and McCafferty (1995). scribed. A mayfly from Arkhara in the Amur Region, Russia, also mentioned by Zherikhin (1978), is probably Danian, and not Cretaceous, Acknowledgments in age (Krassilov, 1976). The traces of activity of burrowing mayfly nymphs in fossilized wood I am very grateful to Dr. David Grimaldi, have been figured by Nessov (1988) from American Museum of Natural History, New Cenomanian deposits at Khodzhakul in York, U.S.A., for the loan of these most interest Karakalpakia, Northern Uzbekistan; similar ich ing mayflies for study; Prof. Javier Alba Tercedor, nofossils have been discovered also in the Amur University Granada, Spain, for copies of some Region, Russia, together with Maastrichtian important papers; and to Dr. Vladimir V dinosaur bones (see below). This scarcity of the Zherikhin, Paleontological Institute of the Upper Cretaceous record of mayflies is in strong Russian Academy of Sciences, Moscow, Russia, contrast to their common occurrence in Lower for the comments on the manuscript. New jersey amber Mayflies: the first North American Mesozoic members ofthe order (Insecta; Ephemeroptera) 113 Systematics both antennae can not be excluded with absolute certainty. However, the structure of the antennae Family Polymitarcyidae Banks, 1900 is in any case peculiar, with a pedicel which is dis CRETOMITARCYINAE Sinitshenkova, tinctly wider than the scape and possesses a small NEW SUBFAMILY apical tubercle that may represent the rudiment of the flagellum. Diagnosis: Imago, male. Antennae situated close Phylogenetic position. Cretomitarcys is based to each other, short and strongly thickened; seg on a single male specimen; thus its phylogenetic mentation not observable but tumourous subglo affinities may be discussed only on the basis of a bose apical part seems to represent pedicel; fla reduced set of features that do not include phy gellum perhaps reduced to small apical tubercle logenetically important female (presence/absence on pedicel. Middle and hind legs well developed, of the imaginal stage) and nymphal characters. more so than the fore ones, fore tarsi clearly five The phylogeny of ephemeroid taxa in general is segmented. Vein MA of forewings forked more still controversial and not well-grounded on distally than the last fork of RS; two long and many points (McCafferty, 1991). Not suprising straight cubital intercalaries originating from ly for an ancient lineage, Cretomitarcys retains wing base. Intercalaries near outer margin wing many primitive character states. Especially the long, with additional shorter ones mostly on middle and hind legs are unusually well devel both sides of the main one; crossveins at the mar oped, showing no tendency to the reduction in gin absent. Anal veins almost straight, not less all living polymitarcyid genera (the leg structure than three. Crossvenation well developed. Hind is not known for the Early Cretaceous genus wing with numerous longitudinal intercalaries, Pristiplocia McCaff, constituting an extinct sub crossveins few and restricted to wing base. family of its own). This character may indicate Forceps long, four-segmented. Two caudal fila that Cretomitarcys forms a sister group to all other ments, rudiment of paracercus very

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