Taxonomy Sphecomyrma

paratype worker of s. freyi

before discovery of first sphecomyrma fossils, there no fossil records of ants cretaceous amber , oldest social insects @ time extended eocene epoch; earliest known ant @ time described forewing found in claiborne formation in tennessee. great diversity of ant fossils found in baltic amber , florissant shales of oligocene , in sicilian amber of miocene have prompted entomologists search ants of cretaceous age may link ants , non-social wasps together. such link may shed light on origins of ants, no fossils of social insect existed before s. freyi discovered, evolution of ants remained mystery. single hymenopterous upper cretaceous fossil has been subject of possible significance evolution of aculeate wasps , ants. single forewing discovered in siberia , described in 1957 cretavus sibiricus, author noting wing ventation closely resembles of bethylid or scoliid wasps, of these families of wasps have close connections origin of ants. however, there several problems: fossil single wing, scientists not explain or answer whether or not insect had key diagnostic body traits place within subclade aculeata.

in 1966, first fossils of s. freyi collected edmund frey , wife during trip collecting mineralogical specimens in magothy exposure near cliffwood beach in raritan bay, new jersey. found large deep red piece of amber embedded in clay containing number of insects, including diptera flies. approximate age of fossils dates cretaceous, 92 million years ago. donald baird of princeton university first notified carpenter recent discovery, , david stager of newark museum arranged transfer specimens studied , examined. @ time, existence of ants of cretaceous age significant, ants not detected of amber around site collected. discovery of ants confirmed existence of cretaceous ants, , appearance of workers closely matched speculations of mesozoic ants looked like. result of these finds, e. o. wilson , colleagues erected new subfamily sphecomyrminae , designated genus sphecomyrma (meaning wasp ant ) type genus in article published in 1967 in journal science. published paper included first description of s. freyi, named after edmund frey , wife. holotype , paratype of species collected , moved museum of comparative zoology, holotype accidentally destroyed. however, neotype specimen numbered amnh-nj-112 collected sunrise landing site near brunswick in 1994, , subsequently donated museum. holotype destroyed because amber accidentally cracked in half, separating 2 workers each other , later stored in wooden cabinet in uncovered draw other fossil insects 30 years; piece deteriorated, appearing more dark , fractured.

a comparison of archetypal ant hypothesised before discovery of sphecomyrma. body details of hypothesised ancestor (top) made same s. freyi (bottom) convenience.

although hypothesised description of mesozoic ants looked accurate when compared actual specimens, characteristics inaccurate. believed ant-like mandibles first appeared before development of ant-like petiole, such case proven false when opposite on s. freyi specimens (ant-like petiole first appeared before development of ant-like mandibles). based on drawings, suggested mesozoic ants had long mandibles multiple teeth, toothed tarsal claws , broadly jointed petiole. examination of collected specimens, however, shows these ants had short mandibles, toothless tarsal claws , separated petiole.

s. freyi remained sole member of sphecomyrma until fossil closely resembling species collected in canadian amber deposits in 1985. wilson provided first description of fossil, naming s. canadensis. notes close resemblance of fossils s. freyi in key characteristics support inclusion in sphecomyrminae. further notes specimens first ants recorded in canadian amber, vast diversity of insects have been found in amber prior discovery, stretching far 19th century. discovery of specimens canada indicates subfamily widespread through of northern hemisphere during late cretaceous. in 2005, new fossils of undescribed sphecomyrma ant , s. freyi collected in white oaks outcrop in sayreville, new jersey. specimens later donated american museum of natural history , studied palaeoentomologists michael engel , david grimaldi, both provided first description of undescribed ant in american museum novitates journal article, naming sphecomyrma mesaki. age of these fossils estimated @ 79 92 million years.

in 1987, russian palaeoentomologist gennady m. dlussky elevated subfamily @ family level, renaming sphecomyrmidae accommodate sphecomyrma , other fossil insects studied throughout soviet union. placement short-lived wilson, new morphological evidence, elevated family subfamily level , studied cretaceous ants put sphecomyrma or cretomyrma. however, dlussky , russian palaeoentomologist elena b. fedoseeva retained classification , sphecomyrma remained under sphecomyrmidae. reasons first segments of antenna short elbowed , structure of mandibles. elbowed antennae allow brood , food manipulation, or sociality, impossible classify sphecomyrma , relatives ants. despite authors notes, did not cite study how ants manipulate items , such antennae, may have implied apices, feature found on antenna, may have been far away mandibles. close distance of apices mandibles allow manipulation of food or antennation other nestmates. issue whether or not metapleural gland present, unique feature found in ants. despite , previous claims made dlussky saying sphecomyrmines including sphecomyrma solitary or semi-communal, confirmed existence of metapleural gland through newly collected fossils confirms sphecomyrma , relatives social. evidence against dlussky reinstated sphecomyrma , subfamily members of formicidae in 1997, although sources published before 1997 did not formally recognise sphecomyrminae @ family level. additional doubts surrounding nature of sphecomyrma , relatives emerged when 1999 paper concluded fossil ants found in cretaceous amber in new jersey closer wasps ants. dismissed due overwhelming evidence supporting placement within formicidae, , fact authors cited unpublished cladograms , disregarded key diagnostic traits (synapomorphies) found in ants.

evolution

original hypothetical cladogram showing placement of sphecomyrma, tiphiid wasps potential ancestor

ants of genus considered primitive within family formicidae. body presents wasp-like structure several ant-like characteristics. these ant-like characteristics, however, primitive compared more modern ants, , intermediate other primitive ants , aculeate wasps. presence of metapleural gland, nodiform (a structure resembling node, segment found between mesosoma , gaster, bulbous posterior portion of metasoma), structure of petiole , general physical appearance of ant concludes sphecomyrma species ants rather wasps; absence of metapleural gland mean wasp instead of ant. not known group of wasps descendants of sphecomyrma, members of family tiphiidae, particularly in genus methocha strikingly similar sphecomyrma. wilson placed genus closest tiphiidae among extant wasps, later study published in 1975 derives ants later clade , not tiphiidae.

sphecomyrma may hold close relationship extant primitive ants. australian dinosaur ant (nothomyrmecia macrops) recognised primitive living ant today, , both ants closely resemble each other. eocene genera of aneuretini resemble sphecomyrma ants, believed ancestors of dolichoderinae. subfamily myrmeciinae thought ancestor of aneuretini because elongated mandibles (a well-known feature in myrmeciinae ants), considered primitive , short mandibles derived. theory proven false after sphecomyrma specimens had small mandibles. currently, phylogenetic analyses recognise sphecomyrma sister group modern living ants, meaning stem-group formicid. means more closely related ants in contrast other organism, crown-group formicids (as in recent common ancestor of modern ants , descendants) more closely related each other , distantly related sphecomyrma. end of mesozoic, sphecomyrmines including these ants vanished.

cite error: there <ref group=upper-alpha> tags or {{efn-ua}} templates on page, references not show without {{reflist|group=upper-alpha}} template or {{notelist-ua}} template (see page).