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x T AMERICAN MUSEUM 

Novitates 



PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY 
CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. 10024 
Number 3208, 43 pp., 24 figures, 1 tables October 23, 1997 



New and Rediscovered Primitive Ants 

(Hymenoptera: Formicidae) in Cretaceous Amber 

from New Jersey, and Their Phylogenetic 

Relationships* 

DAVID GRIMALDI, 1 DONAT AGOSTI, 2 AND JAMES M. CARPENTER 1 

ABSTRACT 



All Cretaceous records of ants are reviewed, 
and evidence originally given for their placement 
is evaluated. Cretaceous Formicoidea preserved in 
rocks lack preservation of critical ant synapomor- 
phies like the metapleural gland, which are pre- 
served in specimens in amber. For this reason, the 
Armaniidae Dlussky, from the Cretaceous of Rus- 
sia, are placed here as Formicoidea incertae sedis, 
not in the Formicidae proper. The oldest amber 
with ants is from New Jersey. 

Seven complete and partial specimens of For- 
micidae, recently discovered in Turonian (92 Ma) 
amber from central New Jersey, are described and 
discussed. The specimens consist of four males 
and three workers. One complete and well-pre- 
served worker is Sphecomyrma freyi Wilson and 
Brown 1967, known previously from two workers 
in a piece of Turonian amber from Cliffwood 
Beach, New Jersey. Well preserved in the new 



worker are external and even some internal fea- 
tures of the metapleural gland a definitive for- 
micid synapomorphy which are described in de- 
tail for the first time. This specimen is designated 
as a neotype to replace the disintegrated holotype 
of this species. One complete male specimen is 
tentatively assigned to Sphecomyrma, which 
would be the first known male of the genus. One 
complete and one partial male, both from the 
same piece of amber, are a new, plesiomorphic 
species of Baikuris Dlussky (Baikuris casei, n. 
sp.), the genus previously known only from upper 
Cretaceous (Santonian) amber of Taymyr, north- 
ern Siberia. Two workers represent a new genus 
and species of Cretaceous Formicidae, Browni- 
mecia clavata n. gen., n. sp., based on distinc- 
tively clubbed antennae, proportions of the anten- 
nal articles, and thin mandibles that lack teeth and 
extensively cross, and a ponerine-like constriction 



* Paleontology of New Jersey amber, Part VI. 

1 Curator, Department of Entomology, American Museum of Natural History. 

2 Research Scientist, Department of Entomology, American Museum of Natural History. 



Copyright American Museum of Natural History 1997 



ISSN 0003-0082 / Price S5.60 



AMERICAN MUSEUM NOVITATES 



NO. 3208 



between abdominal segments III and IV (gaster 
segments I and II). Brownimecia is more closely 
related to extant Formicidae than are Sphecomyr- 
minae, the genus being the earliest known mem- 
ber of the extant subfamily Ponerinae. The fourth 
male belongs to a third genus, undescribed. These 
are the oldest definitive ants. 

Composition, monophyly, and systematic po- 
sition of the subfamily Sphecomyrminae are dis- 
cussed. Modifications were made to the data of 
Baroni Urbani et al. (1992) and reanalyses were 
made of the basal relationships of the Formicidae 
including Sphecomyrma and Brownimecia. Dis- 



crepencies with the cladograms of Baroni Urbani 
et al. (1992) are discussed. Including the fossil 
taxon Formiciinae Lutz (compressed remains 
from the Eocene of Germany) in the cladistic 
analysis, as done by Baroni Urbani et al., imparts 
too many missing values for meaningful analysis. 
Sphecomyrma, not discussed by Baroni Urbani et 
al., retains its basal position in the Formicidae in 
the present analysis. Discovery of new and exclu- 
sively primitive ants in upper Cretaceous ambers 
indicates an origin of the ants probably in the low- 
ermost Cretaceous, but no older, contrary to a re- 
cent molecular hypothesis. 



INTRODUCTION 



The ants can arguably be said to be the 
ecologically and numerically dominant fam- 
ily of insects perhaps of all organisms on 
earth. As Holldobler and Wilson (1990) dis- 
cussed, ants are so abundant that approxi- 
mately 3 million exist in a hectare of Ama- 
zonian forest soil, and they represent some 
10-15% of the entire animal biomass in ter- 
restrial ecosystems. On this basis alone, the 
origins of the ants would be important for 
understanding the evolution of modern ter- 
restrial biological communities. 

The outstanding hallmark of the ants is that 
all species are eusocial, which is what probably 
caused their tremendous success. The wingless 
workers can easily penetrate minute niches. 
Their array of glands and secretions enables 
sophisticated chemical communication, such 
that they can rapidly recruit workers for se- 
questering food; defend the colony, especially 
with soldiers and stinging workers; and even 
;e prey. Eusociality has actually 
he Hymenoptera: once in 
;r times in the Vespoidea 
(social/paper wasps) and the Apoidea s.s. 
(bees). It was the ants that became predomi- 
n nn+ tii*-nirrVi 1-wi^aiicf tHpA/ arp tfinncrht to have 

;ial in- 
sect predators on the ground (Holldobler and 
Wilson, 1990). Clearly, knowing the earliest 
history of the ants can allow much better un- 
derstanding of the unparalleled success of this 
remarkable group. It is a history that began in 
the late Mesozoic. 

SPHECOMYRMA AND NEW JERSEY AMBER 

The first Mesozoic ant to be discovered 
and described was Sphecomyrma freyi Wil- 



son and Brown, in Cretaceous amber from 
New Jersey. The piece of amber that con- 
tained two workers was discovered in 1966 
by an amateur collector, Edmund Frey, who 
found it in strata of the Raritan-Magothy For- 
mations exposed in bluffs at Cliffwood 
Beach, New Jersey. It was studied and re- 
ported by Wilson et al. (1967a, 1967b). De- 
spite such a sensational find, little attention 
was paid to New Jersey amber other than by 
another fossil collector, Gerard R. Case. Case 
collected Cretaceous amber from at least a 
dozen localities between 1962 and 1986, all 
of it found in rather trace quantities on the 
surface of lignitic exposures. Many of his 
samples were given to Princeton University 
(Dept. of Geology) where they were exam- 
ined for inclusions. (The other samples were 
given to the AMNH [American Museum of 
Natural History] in 1992.) The only piece 
with inclusions was found in 1966 the 
same year as the Sphecomyrma discovery 
in the Such Clay Pits in Parlin, New Jersey. 
It contained a ceratopogonid and two chiron- 
omid midges. Case's collections revealed that 
amber in New Jersey was actually wide- 
spread in appropriate Cretaceous exposures, 
and that other insects existed in the amber 
besides Sphecomyrma. These collections re- 
mained largely unnoticed for more than 20 
years, and even the ceratopogonid wasn't de- 
scribed until 1986, as Culicoides casei. 

In 1976 Gerard Case brought Robert Lan- 
genheim (University of Illinois, Champagne- 
Urbana) to several of the amber localities in 
Sayreville and adjacent towns in New Jersey, 
where they collected samples. Langenheim 



GRIMALDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 



had worked on the stratigraphy of late Oli- 
gocene amber from Mexico and Cretaceous 
amber from Alaska. No results were reported 
from those samples from New Jersey. From 
1986-1989 the senior author resumed the 
collection of amber from various Cretaceous 
exposures in New Jersey, some of them vis- 
ited 20 years earlier by Case. The samples 
collected by Grimaldi were used in a strati- 
graphic and chemical study of the amber 
(Grimaldi et al., 1989), and only one piece 
was found to contain an insect inclusion (a 
partial midge). By 1986, some sites had been 
developed and were no longer accessible. 
The bluffs at Cliffwood Beach type locality 
for Sphecomyrma freyi for example, were 
covered in 1974-75 with boulders and a skin 
of cyclone steel fencing onto which concrete 
was poured. All collecting done in New Jer- 
sey up until 1989 uncovered small amounts 
of amber, and the likelihood of discovering 
pieces with insects seemed so remote that 
prospecting was then abandoned. 

In 1992 Gerard Case brought to Grimaldi 's 
attention two remarkable new deposits from 
central New Jersey rich in fossiliferous Cre- 
taceous amber. They lay between some of the 
sites prospected earlier that were only a few 
miles apart. Exact locations and maps are 
available through the senior author, but they 
correspond most closely to site number five 
on the map in Grimald et al. (1989), approx- 
imately 7 km NW of Cliffwood Beach. Since 
November 1992, excavations by dedicated 
AMNH volunteers (see below) have amassed 
several hundred pounds of amber and hun- 
dreds of inclusions. Among these inclusions 
were the additional specimens treated here. 
The new material allows us to more carefully 
consider the phylogenetic position of the 
sphecomyrmines. Although amber has been 
known from New Jersey and other places in 
the Atlantic Coastal Plain for at least 150 
years (reviewed in Grimaldi et al., 1989), it 
was the 1966 discovery of Sphecomyrma that 
brought serious attention to the substance. 

MATERIALS AND METHODS 

Specimens were excavated with hundreds 
of other inclusions in approximately 80 kg of 
raw amber. The amber occurred in veins of 
compacted, lignitic peat, just above the very 



deep deposits of the South Amboy Fire Clay 
(Turanian). The peats are the stranded re- 
mains of deltaic deposits, probably formed 
by coastal cedar swamps. Inclusions of leafy 
shoots and fibrous bark indicate that the bo- 
tanical origin of the amber is not Araucari- 
aceae, as originally proposed based on chem- 
istry (Langenheim, 1969; Grimaldi et al., 
1989), but in the Cupressaceae. A detailed 
account of the stratigraphy, taphonomy, and 
paleoecology of the amber sites is provided 
elsewhere (Grimaldi, 1997). 

Approximately 70% of the amber is vir- 
tually opaque, due to a thick suspension of 
paniculate debris and bubbles. The transpar- 
ent pieces are mostly very brittle and fracture 
easily. To trim and polish a window in this 
amber with an orientation crucial for obser- 
vation, a technique of vacuum-embedding 
needed to be developed. The technique is de- 
scribed in more detail elsewhere (Silverstein 
and Nascimbene, 1997), but involves embed- 
ding the amber in a synthetic casting resin of 
low viscosity and refractive index (see also 
appendix). While the resin is still fluid, the 
preparation is subjected to a reduced pressure 
of approximately 4 psi in a bell jar attached 
to a vacuum pump. This removes air from 
the fine cracks and allows resin to seep in. 
Filling cracks not only cements the fragile 
piece, but allows one to see through cracks 
where the air would otherwise cause a crack 
to be like a small mirror. 

Work on the manuscript was as follows: 
Grimaldi did the final trims and polishing of 
specimens for observation, did sketches and 
final drawings, photographs, and wrote the 
manuscript, including descriptions. Agosti 
also examined morphology, checked the 
sketches and descriptions, and worked with 
Carpenter on the cladistics. 

ACKNOWLEDGMENTS 

It is a pleasure to acknowledge the hard 
work of Keith Luzzi, Gerard Case, and Paul 
Nascimbene, the collectors of the specimens 
reported here, who generously donated their 
specimens to the AMNH. A wonderful spec- 
imen the holotype of Brownimecia clava- 
ta was collected by Yale Goldman, who 
provided it for purchase. In addition, Henry 
Silverstein developed the vacuum-embed- 



AMERICAN MUSEUM NOVITATES 



NO. 3208 



ding technique for the amber laboratory, and 
Paul Nascimbene did many embeddings and 
further refined the technique. Vladimir 
Ovtsharenko kindly provided some Russian 
translations; and Stefan Cover loaned the ho- 
lotype of Sphecomyrma freyi from the MCZ, 
which tragically disintegrated during the em- 
bedding process (see appendix). Funding of 
the research was made possible by a grant 
from Henry G. Walter, trustee of the AMNH 
and by generous donations from Henry and 
Meryl Silverstein. The original manuscript 
was reviewed by Barry Bolton, Bill Brown, 
E. O. Wilson, and especially detailed and 
helpful comments were provided by Phil 
Ward. To all we owe great thanks. 

THE SPHECOMYRMINAE AND 
MESOZOIC "FORMICOIDEA" 

A synopsis of all taxa described as ants 
and close relatives from the Mesozoic, in the 
order in which they were reported, is given 
below. Dlussky (1975, 1983, 1987) described 
16 species and 11 genera from the Creta- 
ceous of Russia and Kazakhstan, based on 30 
compression fossils and inclusions in amber. 
The family Armaniidae was described for 
several new "formicoid" forms: Archaeo- 
pone, Armania, Armaniella, Poneropterus, 
and Pseudarmania. Dlussky (1975) original- 
ly kept the Sphecomyrminae as a subfamily 
of the Formicidae, but later (Dlussky, 1983) 
elevated Sphecomyrminae to family, main- 
taining that the primitive condition of two 
teeth on the mandible and an antenna with a 
short scape and long, flexible funiculus ex- 
cluded them from the Formicidae. Wilson 
(1987), using a morphometric analysis, 
showed that Dlussky's genera are possibly al- 
lometric variations of the gynes and workers 
for only two taxa. He placed Dlussky's gen- 
era into two genera: Sphecomyrma and Cre- 
tomyrma. In lieu of reexamining original ma- 
terial, as E. O. Wilson did for some taxa, we 
will not address the identity of Armaniidae 
here, but our results do bear on the identities 
and relationships of the genera that Dlussky 
placed in the Sphecomyrminae/-idae: Baiku- 
ris, Cretomyrma, Paleomyrmex (later re- 
named Dlusskyidris), and Sphecomyrma. 
Bolton (1994) placed the Armaniidae as a 
subfamily of the Formicidae (along with the 



Sphecomyrminae), which was a classification 
adopted yet again by Dlussky (1996). As we 
discuss below, until more completely pre- 
served material becomes available, it is most 
prudent to regard the Armaniidae as Formi- 
coidea incertae sedis. 

THE MESOZOIC FORMICOIDS 

Sphecomyrma freyi Wilson and Brown, 
1967. Described on the basis of two well- 
preserved workers in a piece of amber from 
Cliffwood Beach, New Jersey. It was origi- 
nally thought (Wilson et al., 1967a, 1967b) 
that this amber was Cenomanian (ca. 100 
Ma), then late Santonian, ca. 80 Ma (Wilson, 
1985; Holldobler and Wilson, 1990) (this 
was a date quoted by Dlussky, 1975). Dlus- 
sky (1983: p. 63 of Paleontol. J. translation) 
later mentioned that "in the past few years 
they [the New Jersey amber deposits] have 
been redated as Santonian or even early 
Campanian," which is erroneous. Like the 
material we are reporting, the type material 
of S. freyi is probably Turonian (9094 Ma). 
In the original paper describing the species 
(Wilson et al., 1967b), they mentioned the 
piece of amber as being in the private col- 
lection of Edmund Frey, of Mountainside, 
New Jersey. It was donated to the Museum 
of Comparative Zoology, Harvard, soon after 
publication of the paper, residing in the fossil 
insect collection. The specimen disintegrated 
during the vacuum-embedding process, for 
which a neotype is designated, below. 

Cretomyrma arnoldii Dlussky, 1975: 116. 
Known from a partial worker in a piece of 
amber from Yantardakh, Taymyr Peninsula, 
northern Siberia (Paleontological Institute 
Nauka [PIN] number 3130/113). It is largely 
headless (only imprints of some rnouthparts 
and the second segment of the antenna re- 
main), but details of petiole, gaster, and legs 
are well described. This deposit is dated as 
Santonian. Cretomyrma was placed by Dlus- 
sky (1975; 1987) in the Sphecomyrminae/- 
idae. 

Cretomyrma unicornis Dlussky, 1975: 
116. A worker specimen even more partial 
than C. arnoldii, with just a portion of the 
propodeum, petiole, gaster, and the entire left 



GRIMALDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 



middle leg preserved. From the same deposit 
as C. arnoldii, PIN 3311/363. 

Dlusskyidris zherichini (Dlussky), 1975: 
118. Dlusskyidris Bolton, 1994, is a replace- 
ment name for Paleomyrmex Dlussky (pre- 
occupied by Paleomyrmex Heer, 1865). 
Known from a virtually complete male (ho- 
lotype, PIN 3311/364) and two incomplete 
males (PIN 3311/365 and 3311/366) in Si- 
berian amber. Placed by Dlussky (1975; 
1987) in the Sphecomyrminae/-idae. 

Petropone petiolata Dlussky, 1975: 119. 
Compression fossil of an apparent wingless 
specimen, possibly a worker, from the Cre- 
taceous (Turonian) of southern Kazakhastan 
[PIN 2783/158]. Dlussky actually placed this 
(and two other genera, immediately below) 
in the Ponerinae, but later (Dlussky, 1983: p. 
64 Paleontol. J. translation) mentioned that 
the "systematic position of these genera {Pe- 
tropone and Cretopone] must be changed 
.... [but] remains unclear, because their im- 
pressions are incompletely preserved." Car- 
penter (1992) mentioned this taxon to be 
only doubtfully assigned to the Formicidae. 

Cretopone magna Dlussky, 1975: 119. 
Compression of a partial and badly distorted 
insect from the same deposit as Petropone. 
Dlussky (1983) removed it, and Petropone, 
from the Ponerinae to a genus incertae sedis 
in the Formicoidea. In our view, based on 
Dlussky 's (1975) illustration, it is impossible 
to assign the specimen to any aculeate fam- 
ily. 

Archaeopone kzylzharica Dlussky, 1975: 
121. Based on a single, incomplete compres- 
sion fossil from the Cretaceous of Kazakha- 
stan (same deposit as previous two taxa) 
(PIN 2383/263). Originally placed in the Po- 
nerinae (Dlussky, 1975), it was later placed 
in the Armaniidae (Dlussky, 1983). Carpen- 
ter (1992) gave this taxon a doubtful assign- 
ment to the Formicidae, with which we must 
concur. As illustrated (Dlussky, 1975, p. 120, 
fig. 132), the specimen is headless and vir- 
tually legless. The alitrunk and gaster are 
preserved; a petiole also shows but without 
an obvious node. 

Dolichomyrma longiceps Dlussky, 1975: 
121. Cretaceous of Kazakhastan (same de- 



posit as previous taxa). Like Archaeopone, 
Dlussky originally placed this unique speci- 
men (PIN 2383/145) and a similar one (de- 
scribed as Dolichomyrma} latipes Dlussky, 
1975 [PIN 2383/144]) in the Ponerinae, then 
in the Armaniidae. Carpenter (1992) men- 
tioned this taxon also to be of doubtful as- 
signment as a formicid. The type and only 
known specimen of D. longiceps has pro- 
portions of the head, alitrunk, and gaster sim- 
ilar to that of a worker ant, and a possible 
petiole is rendered in his figure of it, but no 
other "diagnostic" features are obvious. 

Armania robusta Dlussky, 1983. Based on 
a large, winged female compressed in rocks 
from the Al'skaya Formation (Cenomanian) 
of Ten'ki District, Magadan region, Russia. 
Holotype (PIN 3901/155) is in lateral view 
showing a distinct, large petiole; paratype 
(PIN 3901/160), also winged, is preserved 
dorsally with a petiole barely preserved. 

Pseudarmania rasnitsyni Dlussky, 1983. 
Known only from a single winged, well-pre- 
served female from the same deposit as Ar- 
mania (PIN 3901/156). Head, alitrunk, and 
gaster, some legs, are well preserved, and 
only basal portions of the wings. 

Pseudarmania aberrans Dlussky, 1983: as 
for P. rasnitsyni, except that the unique spec- 
imen (PIN 3901/152) is missing the head and 
anterior portion of the alitrunk. 

Armaniella curiosa Dlussky, 1983. De- 
scribed on basis of a single, incomplete fe- 
male (PIN 3901/158) from the Al'skaya For- 
mation of Ten'ki, Magadan. Portions of the 
head, antenna, wing, legs, gaster, and the pet- 
iole are preserved. 

Archaeopone taylori Dlussky, 1983. Based 
on two specimens from the Al'skaya For- 
mation of Magadan. The holotype (PIN 
3901/154) is an apparent male with the head, 
antenna, alitrunk, anterior half of gaster, and 
portions of wing preserved. 

Poneropterus sphecoides Dlussky, 1983. 
Complete apparent male specimen (PIN 
3901/157) from the Al'skaya Formation of 
Magadan. Virtually entire body preserved, in 
dorsal aspect. 



AMERICAN MUSEUM NOVITATES 



NO. 3208 



Sphecomyrma canadensis Wilson, 1985. 
Known from a well-preserved worker (ho- 
lotype) and poorly preserved one in amber 
from near Medicine Hat, Alberta, Canada, 
numbers 330 (holotype) and 205 (paratype) 
in Biosystematics Research Institute, Agri- 
culture Canada, Ottawa. These specimens 
were from collections made by McAlpine 
and Martin (1966), who also collected Cre- 
taceous amber from Cedar Lake, Manitoba. 
It is generally believed that the amber from 
Medicine Hat and the redeposited amber 
from Cedar Lake is the same age as amber 
from Grassy Lake, Alberta, dated in situ (ac- 
cording to Pike, 1995) as from the upper part 
of the Judith River Group of the Foremost 
Formation, ca. 7879 Ma. 

Pike (1995) reported three additional ants, 
identified as "Sphecomyrma sp.," in the am- 
ber from Grassy Lake. These are in the Royal 
Tyrrell Museum, Drumheller, Alberta. The 
specimens were examined by E. O. Wilson, 
two of them being Sphecomyrma [canaden- 
sis7], the other being a poorly preserved 
worker with mandibles and antenna more 
highly derived than in Sphecomyrma (Pike, 
personal commun. to DG, Jan. 1997). 

Cretacoformica explicata Jell and Duncan, 
1986. Based on (an) alate specimen(s) from 
the Lower Cretaceous of Koonwarra, Victo- 
ria, Australia, in the Aptian (ca. 115 Ma) 
Koonwarra Fossil Bed Formation. The spec- 
imen is not well preserved. For example, the 
petiole, if present, is obscured. Naumann 
(1993) reexamined the unique specimen (no. 
NMVP 102501A,B in Museum of Victoria, 
Melbourne), and presented a detailed, cor- 
rected description. He could not place it to a 
family of Apocrita, but discussed features 
that were both consistent and inconsistent 
with the Diapriidae, as proposed by Darling 
and Sharkey (1990). The genus was cited as 
Cretaceoformica [sic] in Poinar (1992). 

Baikuris mandibularis Dlussky, 1987. 
Known from three males in a piece of amber 
from Lake Taymyr, Baykura-Neru Bay, Tay- 
myr Peninsula of Siberia, Russia (amber 
piece is PIN 3730/5 in the Paleontological 
Institute, Moscow). This amber is dated as 
Santonian. 

Baikuris mirabilis Dlussky, 1987. Known 



from an incomplete male in a piece of amber 
from the same locality as B. mandibularis 
(PIN 3730/8). 

Cariridris bipetiolata Brandao and Mar- 
tins-Neto, 1989: Based on an apterous spec- 
imen in Lower Cretaceous (Santana Forma- 
tion, Aptian, ca. 110 Ma) limestone from 
Ceara, Brazil, and interpreted as a worker. 
This specimen has a definite, narrow and 
elongate petiole, and a scape that appears 
slightly longer than in Sphecomyrma or Cre- 
tomyrma workers; but the bases of the anten- 
nae, on the other hand, are obscured. Ex- 
amination by DG of an excellent color slide 
of the specimen indicates that the proposed 
existence of a postpetiole in the specimen (a 
constriction just anterior to true abdominal 
segment IV) may be a preservational artifact. 
Prior and continuing studies of Santana For- 
mation insects (e.g., Grimaldi, 1990) docu- 
ment excellent and detailed preservation of 
external cuticles, the study of which requires 
proper physical cleaning and removal of ma- 
trix with acetic acid digestion. There are sub- 
stantial areas of the specimen still uncleaned, 
with limestone matrix still covering the pro- 
notum, bases of the legs, all of the mid left 
leg, and margins of the alitrunk and petiole. 
What is interpreted as petiole and gastric 
constriction could be an appearance due to 
the overburden of matrix in these areas. As 
we discuss later, placement of Cariridris as 
possibly in the Myrmiciinae (Brandao et al., 
1990) is consistent with the basal phyloge- 
netic position of this subfamily. However, 
since mandibular dentition, calcars, and pres- 
ence of a metapleural gland cannot be ob- 
served, placement of Cariridris in the family 
Formicidae cannot be confirmed with present 
material. 

Lastly, Poinar (1992: 203) published an 
unclear photograph of an aculeate in Leba- 
nese amber (Neocomian) from the Acra Col- 
lection, as "The earliest known ant?" That 
specimen is preserved very well and was ex- 
amined in 1990 by the senior author. Al- 
though an aculeate, it is definitely not For- 
micoidea. 

Using a criterion of just the presence of a 
petiole a feature easily fossilized even as a 
compression there is certainty in the iden- 



GRIMALDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 



tity of the following genera being formi- 
coids: Armania, Amaniella, Archaeopone 
taylori, Cariridris, Dolichomyrma, Poner- 
opterus, and Pseudarmania. Wilson (1987) 
reexamined Dlussky's holotypes of Armania 
robusta and Pseudarmania rasnitsyni, and 
found that a trochantellus was actually ab- 
sent, as is the case in all living Formicidae. 
Dlussky used its apparent primitive presence 
to exclude the Armaniidae from the formic- 
ids. It is an intriguing character, since it oc- 
curs as a ground plan of the Vespidae, the 
sister group (with Scoliidae) to the Formici- 
dae (Brothers, 1975; Brothers and Carpenter, 
1993; Rasnitsyn, 1988). The character, how- 
ever, seems as if it would be exceedingly dif- 
ficult to resolve in a compression fossil, since 
it is a segment largely fused to the base of 
the femur, demarcated merely by a fine su- 
ture. A trochantellus definitely occurs in at 
least the New Jersey amber specimens, mak- 
ing it plausible that the Armaniidae also pos- 
sessed it. In Dlussky's diagnosis of the Ar- 
maniidae he mentioned the broad attachment 
of the petiole to the gaster (a plesiomorphic 
feature), which Wilson also critiqued. If the 
large gasters of the winged females described 
by Dlussky indicate that they are indeed 
queens, as argued by Wilson, the most par- 
simonious argument is that the broadly at- 
tached petiole is a sexually dimorphic fea- 
ture, as in living Formicidae. Lack of pre- 
served details like dentition of the mandible 
and presence of a metapleural gland pre- 
cludes a more detailed placement of these 
taxa, at least with the present material. 

Incomplete and/or poor preservation of 
Archaeopone kzylzharica, Cretacoformica, 
Cretopone, and Petropone (as described by 
Dlussky) makes their identities even as for- 
micoids questionable in our view. This 
leaves the four genera described in Creta- 
ceous amber from Siberia, Canada, and New 
Jersey: Sphecomyrma, Cretomyrma, Baiku- 
ris, and Dlusskyidris. The latter two genera 
are known only from males, and metapleural 
glands cannot be observed. The first two 
genera are known from workers where the 
metapleural gland can be observed, making 
these the oldest true ants, family Formicidae 
(see below, for discussion of taxonomy). The 
oldest definitive Formicidae is still Spheco- 
myrma, along with the new taxa in New Jer- 



sey amber described below. We mostly agree 
with the classification of Wilson (1987), in 
that Sphecomyrminae are the most primitive 
and oldest known subfamily of the Formici- 
dae (see cladistic results, below). However, 
we are unprepared for the formal synonymies 
of Dlussky's genera made by Wilson, without 
the basis of definitive synapomorphies. 

The following is a proposed summary 
classification of Cretaceous aculeate fossils 
that have been described as convincing ants 
or close ant relatives: 

APOCRITA, incertae sedis 

Cretacoformica 
ACULEATA, incertae sedis 
Cretopone 
Petropone 
Superfamily FORMICOIDEA 

Family ARMANIIDAE (monophyly 

uncertain) 
Armania 
Armaniella 
Archaeopone 
Dolichomyrma 
Poneropterus 
Pseudarmania 
Family uncertain 

Cariridris 

Family FORMICIDAE (true ants) 
Subfamily Sphecomyrminae 
IBaikuris ( S 6 only) 
Cretomyrma 
Dlusskyidris 
Sphecomyrma 
IHaidomyrmex (Burmese amber: 

Tertiary?) 

Subfamily Ponerinae 
Brownimecia 

FAMILY FORMICIDAE 

SUBFAMILY SPHECOMYRMINAE 

INCLUDED GENERA: Baikuris, Cretomyrma, 
Dlusskyidris, and Sphecomyrma. 

All features diagnostic for the subfamily 
as given by Wilson et al. (1967b) and Dlus- 
sky (1975, 1983, 1987) are symplesiomor- 
phic at the level of the family: worker with 
short mandibles with only two teeth; anten- 
nae with short scape and long, flexible fu- 
niculus; low, rounded petiole; presence of 
metapleural gland; an unconstricted gaster; 



AMERICAN MUSEUM NOVITATES 



NO. 3208 



extrusible sting; mid and hind tibiae with 
double spurs. 

The only synapomorphies we could find 
for the group are: presence of a short pedicel, 
which has a length slightly longer than its 
width; a second funicular segment (first fla- 
gellar segment) twice or more the length of 
other segments (an exception would be Sphe- 
comyrma canadensis, see below); and males 
without a distal, evanescent segment of wing 
vein CuA (CuA 1 )- All three features are 
unique within the Formicidae. However, the 
short pedicel also appears in some Vespidae, 
so it is possibly plesiomorphic. 

Dlussky removed sphecomyrmines from 
the Formicidae, as mentioned above, based 
on the structure of the antenna and the man- 
dibles. Specifically, the antenna has a first 
segment too short for the antenna to be suf- 
ficiently elbowed a condition necessary, 
Dlussky maintained, for eusociality, since it 
allows brood and food manipulation. If not 
social, Dlussky concluded, then Sphecomyr- 
ma and relatives cannot be ants. Although he 
did not cite studies that address how ants ma- 
nipulate objects with their antennae, Dlussky 
presumably meant that the apices of the an- 
tennae must not be too distant from the man- 
dibles, for optimal manipulation of food and 
tactile communication ("antennation"). In- 
deed, antennation is a behavior commonly 
used for such social activities as trophallaxis, 
although (as Wilson [1987] pointed out), 
trophallaxis may not occur among workers 
of many primitive ants such as Nothomyr- 
mecia, Amblyoponini, Apomyrminae and 
even some advanced species like Pogono- 
myrmex badius (reviewed in Holldobler and 
Wilson, 1990). Workers of some ants merely 
transport larvae to cached prey and do not 
engage in trophallaxis. 

Evidence in favor of Dlussky's argument, 
however, is the fact that the proportions of 
the scape and funiculus appear to be grossly 
maintained throughout the ants. For example, 
there is a convergent development in ants 
with extremely long, gaff-shaped mandibles 
and a corresponding lengthening of the scape 
(e.g., Acanthognathus, Harpegnathos, Myr- 
mecia, and Myrmomoteras). This suggests a 
functional constraint in proportions of the an- 
tennae and mandibles. Dlussky attempted to 
quantify the relationship between antennal 



proportions and social existence in aculeates. 
Using 37 genera in various families, he de- 
vised several indices of the antennae, which 
for purposes here are best represented by his 
IK1 index (length of scape/total length of an- 
tenna). This index and the other two were 
divided into three categories: one represented 
by the parasitoid aculeates (IK1 = 10-25%), 
the second by the solitary provisioning 
wasps and bees (IK1 = 17-35%), and the 
third by the social bees, ants, and a few sol- 
itary bees (IK1 = 30-40%). In lieu of seeing 
the complete data, it is reasonable to assume 
these are arbitrary groupings. Statistics on 
ANOVA or confidence limits were not given, 
and the great overlap in the ranges would 
suggest that the groupings are not significant. 

We do not want to belabor the antennal 
index argument, because the manipulation of 
the antennae in any sphecomyrmine will nev- 
er be observed, only inferred. For Dlussky 
(1983) to claim that "[sphecomyrmines] 
could not have transported their brood or en- 
tered into trophallaxis with their larvae," is 
thus speculation at this point. As Wilson 
(1987) pointed out, the eusocial wasps have 
antennal proportions similar to those of the 
sphecomyrmines, and this obviously hasn't 
prevented them from feeding their larvae. In 
fact, an extremely short antennal scape is 
present in various leptanilloidine ants, which 
are eusocial like other ants. Morphology of 
sphecomyrmines is not at all inconsistent 
with a social existence, but perhaps the only 
way to confirm sociality would be the dis- 
covery of part of a fossilized colony. Por- 
tions of fossilized colonies occur, rarely, in 
younger, Tertiary ambers, such as with some 
dolichoderines like Azteca, and another (un- 
described) genus in Miocene amber from the 
Dominican Republic (Waggensberg et al., 
1996). Wilson's (1987) morphometric evi- 
dence on the relative size of the gaster is 
strongly supportive of castes in the Creta- 
ceous formicoids. 

Dlussky probably underestimated the sig- 
nificance of the metapleural gland, a feature 
agreed even by Dlussky to be in sphecomyr- 
mines. The metapleural gland, which pro- 
duces large quantities of microcidal and fun- 
gistatic phenylacetic acid, is unique to ants. 
It presumably acts as a disinfectant, and al- 
lows nesting in soil/leaf litter without infec- 



GRIMALDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 



tion of the brood and colony (Holldobler and 
Wilson, 1990), which explains its loss in 
tree-nesting genera (Oecophylla, Polyrachis, 
Dendromyrmex, and most Camponotus) and 
some socially parasitic ants. Despite claims 
by Dlussky (1987) that sphecomyrmines 
:y or semicommunal, the meta- 

r jland is almost certainly evidence of 

a social existence. 

Brandao et al. (1990) stated that the po- 
sition of sphecomyrmines as ancestral/prim- 
itive to all Formicidae "... was challenged 
by Dlussky [sic] 1987, with whom we con- 
cur." They then concluded that Cariridris is 
the oldest formicid on the basis of its differ- 
entiated scape and the presence of a petiole. 
Baroni-Urbani (1988) (and as cited in Poinar, 
1992) also offered a conclusion similar to 
that of Dlussky, that Sphecomyrma could not 
be an ant because of the short basal antennal 
article, and "the apparent absence of a meta- 
pleural gland." This is one reason why Bar- 
oni-Urbani et al. (1992) did not include 
Sphecomyrma in their phylogenetic analysis 
of ant tribes (personal commun. CBU to DG 
and DA). Our new material definitively 
proves the existence of the gland. Also, Ba- 
roni Urbani and de Andrade (1994: p48) 
commented that "only one probably true ant 
is known from the lower Cretaceous [Car- 
iridris} . . . other presumed Cretaceous For- 
micidae are currently regarded as non-for- 
micid Aculeates." As discussed above, crude 
preservation of Cariridris in limestone pre- 
vents observation of critical details. 

The other reason given by Baroni Urbani 
et al. (1992) for not including sphecomyrmi- 
nes in their ant cladogram was that "many of 
the characters . . . cannot be assessed ..." 
Oddly, they included the Formiciinae, an ex- 
tinct subfamily described from compressed 
remains in Eocene oil shales of Messel, Ger- 
many (Lutz, 1988), the preservation of which 
is hardly as fine as that in amber. Indeed, only 
20% of the characters in their matrix can be 
scored for the Formiciinae, but slightly over 
40% can be scored for Sphecomyrma workers 
(67% if characters of the apparent male are 
included, but which were unavailable to Bar- 
oni Urbani et al. [1992]). This probably ex- 
plains why the Formiciinae was the basalmost 
lineage in their analysis, which we discuss in 
the cladistic section of this paper. 



Genus Cretomyrma Dlussky 

DIAGNOSIS (extracted and translated from 
Dlussky, 1975, 1983): Known only from 
workers. Propodeum: low; with "i ~.t-Vi_ 
like process; spiracles circulai, >j 
Sphecomyrma on the basis of a p 



terior connections that are less constricted. 
Legs elongate, with calcars on mid and hind 
tibiae. Mandibles with "additional tooth on 
top." 

One character mentioned by Dlussky, the 
size of the sting, is questionable, since the 
extent that it is extruded will affect estimates 
of its size. 

TYPE SPECIES: C. arnoldii Dlussky. 

Genus Dlusskyidris Bolton 

Paleomyrmex Dlussky, 1975: 118 (preoccupied 

by Paleomyrmex Heer, 1865: 91). 
Dlusskyidris Bolton, 1994: 187 (replacement 

name). 

DIAGNOSIS (extracted and translated from 
Dlussky, 1975): Known only on basis of 
male. Mid and hind tibia with calcars. Wing 
venation complete and primitive, with closed 
cells Ir + 2r, 3r, 2rm and Imcu [Dlussky's 
terminology]. Subgenital plate triangular, 
reaching valvulae. Last tergite of abdomen 
triangular, with well-developed cerci. Para- 
meres narrow, pointed, and slightly curved 
medially. 

Dlussky mentioned that, on the basis of 
hardly being able to associate males and 
workers in ants, it is "quite possible that Pa- 
leomyrmex are males of Sphecomyrma or 
Cretomyrma." 

TYPE SPECIES: D. zherikhini (Dlussky) 

Genus Sphecomyrma Wilson and Brown 

DIAGNOSIS: Scape short, 0.57-0.68 mm; 
funiculus long and filiform, approximately 
four times the length of scape; pro/mesotho- 
racic suture complete and well formed; pet- 
iole with distinct, domed node widely sepa- 
rated from propodeum and gaster by deep 
constrictions; cuticle without sculpturing, 
just superficially microscopic relief, with 
scattered and sparse setae. 

Significant features not mentioned in the 
original reports (Wilson et al., 1967a,b), 



AMERICAN MUSEUM NOVITATES 



NO. 3208 



Jk * 

Hfe ^"" * r 




i ic Bife > 
- \ *< 





GRIMALDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 













Fig. 1. Photomicrographs of Formicidae in Turonian amber from New Jersey. [Left page] a. Sphe- 
comyrma freyi, AMNH NJ-112. b. Male, Sphecomyrmal AMNH NJ-242. c. Male, Baikurus casei (ho- 
lotype), AMNH NJ-90bb. [Above] d. Male, undetermined genus, AMNH NJ-107. e-f: Brownimecia 
clavata. e. Holotype. f. Paratype, AMNH NJ-231. 



AMERICAN MUSEUM NOVITATES 



NO. 3208 



which we report here based on AMNH 
NJ-1 12, are: helcium apparently lacking; tro- 
chantellus lacking; and a pair of long, ex- 
tremely fine setae present in the middle of 
the clypeus. 

TYPE SPECIES: S. freyi Wilson and Brown. 

Sphecomyrma freyi Wilson and Brown 
Figures la, 2, 3 

SPECIMEN (NEOTYPE): AMNH NJ-1 12, 
from the "Sunrise Landing" site, East 
Brunswick, New Jersey. Collected by Gerard 
Case, James Leggett, and Paul Borodin, 
1994. The ant is a complete and beautifully 
preserved wingless female in a transparent, 
deep amber-colored piece that originally was 
half filled with debris. After embedding, the 
debris half was sliced off; now the piece is 
18 X 14 X 5 mm, and contains some debris, 
bubbles, as well as one mite, six podurid 
Collembola, stellate trichomes, and portion 
of a spider. A piece of debris is lying in front 
of the head, obscuring a portion of the face. 
Deposited in the Museum of Comparative 
Zoology, Harvard University, in replacement 
for the original type specimen (see appen- 
dix). 

DESCRIPTION: Measurements of AMNH 
NJ-1 12: total length 4.1 mm; head width 
1.08; eye depth 0.28; scape length 0.57; fu- 
niculus length 2.02; alitrunk length 1.48; gas- 
ter length 1.51. These measurements and oth- 
er features agree in virtually all respects with 
the detailed descriptions and illustrations in 
Wilson et al. (1967a,b), to which we can add 
some observations on the metapleural gland 
(MG). The MG was distinctly observed un- 
der 60-100X magnifications, although better 
results were obtained using a Leitz stereo- 
scope at 144X and different angles of fiber 
optic illumination. Best results were obtained 
by examining the propodeum at 160X and 
400 X using a Zeiss compound microscope 
and reflected fiber optic illumination. This 
method of examination absolutely requires a 
flat amber surface parallel to and very close 
to the surface of the structure, as in the prep- 
aration of AMNH NJ-1 12. In the original re- 
port by Wilson et al. (1967b: p. 11), there 
was some equivocation as to the presence of 
the gland, which perhaps explained why it 
was not described in any detail: "... if we 




Fig. 2. Newly discovered worker and neotype 
of Sphecomyrma freyi (AMNH NJ-1 12, now in 
the MCZ). Above. Detail of head, frontal view (at 
a slight ventrolateral angle). Total length of funic- 
ulus and relative size of flagellomeres are distort- 
ed, since the antenna is curled back and somewhat 
underneath the head. The left side of the head is 
obscured by a large piece of debris. Note that 
short space between scape and pedicel is a mem- 
branous area, not an antennomere. Below. Detail 
of pretarsal claws. 



are mistaken about the presence of the meta- 
pleural gland, it would be possible to con- 
sider Sphecomyrma as a wasp rather than an 
ant." 

The metapleural gland in AMNH NJ-1 12 
distinctly shows a wide oval orifice, virtually 
round, with a shallow lip extended antero- 
ventrad to it for a length of approximately 6 
to 7 diameters of the orifice. Distance of the 
orifice from the posterior margin of the pro- 



GRIMALDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 




< t 

r 



atrium \ 
(subcuticular) 



Posterior end 



MGO 



Fig. 3. Sphecomyrma freyi worker, AMNH NJ-112. Photomicrograph and illustrated rendering (to 
the same scale) of the alitrunk and anterior portion of the gaster, showing details of the metapleural 
gland opening [MGO] (arrows) and petiole. The cuticle of the bulla appears thinner than surrounding 
cuticle and, as shown in the photo, this area is actually collapsed into a slight depression. The bulla 
was rendered in the drawing as it might have appeared: slightly bulging. 

Subcuticular detail beneath the MGO is also shown, which is probably the atrium of the gland, with 
remnants of the glandular tissue to one corner. Scale = 0.1 mm. 



Male, AMNH NJ-242, probably Sphecomyrma. Scale = 0.5 mm. 



podeum is approximately twice the diameter 
of the orifice. The cuticle of the area anterior 
to the orifice is quite transparent and shows 
little sclerotization, suggesting it to be con- 
siderably thinner than surrounding cuticle of 
the alitrunk. What was probably a slightly 
raised area (the bulla) is now a shallow con- 
cavity, perhaps compressed because of the 
thinner cuticle in this area. Consequently, an 
irregularly shaped chamber is visible beneath 
the cuticle, probably the atrium for the se- 
cretions of the metapleural gland. In the an- 
terodorsal corner of the lightly sclerotized 
subcuticular chamber is a whitish mass with 
four small lobes: perhaps the gland itself, 
shrunken from its normal size. 

Sphecomyrma canadensis Wilson 

The only other sphecomyrmine known 
from North America can be distinguished 
from S. freyi (according to Wilson [1985]) 
based on the workers with a more robust 
trunk and a shorter third antennal segment 



(which is about as long as the second anten- 
nal segment; in freyi the third segment is 
slightly more than twice the length of seg- 
ment two). 

Sphecomyrma? sp. 
Figures Ib, 4, 12a 

SPECIMEN: Male, AMNH NJ-242, from 
White Oaks site, Sayreville, New Jersey, col- 
lected by Keith Luzzi, 1995. A superbly pre- 
served, complete, and well-displayed speci- 
men in a piece of amber that was originally 
cylindrical and 5 mm diameter, 10 mm long, 
with the ant occupying almost the entire di- 
ameter. The amber is slightly turbid with 
minute particles and bubbles, and contains a 
few fine cracks. The piece was vacuum-em- 
bedded and sliced lengthwise to remove the 
debris-filled half and improve visibility of 
the wings and venation. 

DESCRIPTION: Total length 3.13 mm. HEAD: 
With three large ocelli on vertex, but not on 
tubercle(s); pair of fine, stiff hairs on frons, 



GRIMALDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 



vertex, and postocciput, with finer hairs in- 
terspersed. Face with two pairs of longer, fine 
setae and several smaller ones. Eye reniform, 
with middle of hind margin emarginate, in- 
dented to a depth of about 4 facets. Eye 
large, its depth 0.6 X depth of head; width of 
eye 0.72X depth of eye. Supra-antennal su- 
ture present, extended to level of anterior 
ocellus. No microtrichia on head. Antennal 
proportions: scape short, approximately same 
length as flagellomere I (funicular segment 
II); pedicel very short, ca. 0.3X length of fla- 
gellomere I. Flagellomere I 1.1 1.2 X length 
of longest distal funicular segments. Antenna 
with 1 1 flagellomeres, densely covered with 
fine microtrichia, total length of antenna 2.6 
mm. Mouthparts largely covered with bub- 
bles, with two palpal segments protruding. 

ALITRUNK: 1.25 mm long, length of petiole 
0.35 mm. Petiole covered with microtrichia, 
having pair of longer setae on apex of nodus, 
tae posteriad. Depth of petiole 
: 1.5X depth of where it is at- 
tached to trunk or gaster. Trunk largely cov- 
ered with fine microtrichia, nota with scat- 
tered, larger setae. Legs distal to and includ- 
ing femora with microtrichia in even, longi- 
tudinal rows. Mid and hind tibia each with a 
pair of setose, apical spurs; one on the hind 
tibia is pectinate. Propodeal spiracle slitlike, 
with small lobe covering part of orifice. 
WINGS: Forewing length 2.25 mm. Hind- 
wing 0.7 X length of forewing, shapes typi- 
cally formicid, with hindwing having more 
acute apex and angulate posteroapical mar- 
gin. Distinctive features of forewing are: cos- 
tal vein thickened beyond pterostigma, ta- 
pering to nearly wing apex; vein R + Sc with 
small spur just before it meets with ptero- 
stigma; discoidal cell narrow, with distinctive 
veins connecting it with R + Sc and M + 
CuA. Hindwing with 7 fine, long distal ham- 
uli, no anterior hamuli; basal part of vein M 
straight, distal spur virtually lost; vein Cu 
fairly long, nearly reaching wing margin. 

GASTER: Length 1.22 mm; segments 1 and 
2 equal in length, comprising approximately 
% of gaster. Terminalia largely obscured by 
layer of froth, with two pairs of setose lobes 
protruding (cerci?). Anterior pair (parameres) 
twice as broad as posterior ones. 

DISCUSSION: Genera of ants are not rou- 
tinely surveyed for males, the systematics of 



which is based mostly on workers. Without 
males taken directly from a colony, assign- 
ment of them to a particular species or even 
genus is rarely done. Nonetheless, some fea- 
tures allow us to tentatively associate this 
male with Sphecomyrma workers: similar 
size; similarity in structure of the petiole, 
which has a pair of fine, long setae on the 
apex of the node (albeit widespread in many 
ants); lack of a trochantellus; and the pro- 
portions of the basal segments of the anten- 
na. This male is certainly not Baikurus or the 
same genus as AMNH NJ-231. 

GENUS Baikuris Dlussky 

DIAGNOSIS: According to Dlussky 
(1987): Only males known, having eyes 
kidney-shaped; mandibles na 
virtually parallel and without teeth; base of 
outer surface with oval area and ridge 
(opening of mandibular gland?); "lower 
jaw" palps long, 6-segmented; labral palps 
evidently 3-segmented; scutum with deep 
parapsidal grooves; forewing with cell Ir + 
2r (Dlussky terminology) partly divided by 
rudimentary crossvein; mid and hind legs 
with small trochantellus; tibial spurs 2, 2, 
2; claws with preapical tooth; petiole dis- 
tinct, with small node; indistinct constric- 
tion between first and second segment of 
abdomen [sic?] [gaster]; genitalia small, re- 
tracted into abdominal segments; cerci well 
developed. 

Baikurus easel, new species 
Figures Ic, 5a-d, 12b 

DIAGNOSIS: Known only from male spec- 
imens, and distinguished from other males of 
genus on basis of eyes not being reniform 
and there being no complete or partial cross- 
vein between cell Ir + 2r. Otherwise, simi- 
larities with Baikurus are striking: mandibles 
have no or virtually no teeth; labial palps are 
long, 6 segmented; alitrunk with deep pa- 
rapsidal grooves; small trochantellus present 
on mid and hind legs; petiole elongate, as in 
Baikurus mirabilis; and genitalia very simi- 
lar. 

DESCRIPTION: Males large, 7.5 mm body 
length, forewing length 5.0 mm. 

HEAD: With three large ocelli, hind pair on 
low tubercles; head bare of setae. Eyes 



GRIMALDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 



large, oval (not reniform or emarginate), 
depth ca. 0.6 X depth of head. No supra- an- 
tennal suture seen. Antennal proportions: 
scape short, 0.5 X length of flagellomere 1 
(antennal segment 3); pedicel very small, 
0.45 X length of scape; antennal segment 3 
slightly longer than immediately distal one, 
segments increasingly shorter distad, nar- 
rowly tapered at apex. Antenna with 1 1 fla- 
gellomeres. Labial palps long, 5 segments 
visible; maxillary palps shorter, 4 segments 
visible. Mandibles barely toothed; clypeus 
well developed. 

ALITRUNK: Pleura somewhat obscured; 
legs long and slender, forelegs with one api- 
cal tibial spur; mid and hind tibia with two 
apical tibial spurs; mid and hind coxa (best 
seen in NJ-90aa) with slight suture at prox- 
imal end of femur (the trochantellus). Peti- 
ole long and slender: in NJ-90bb length is 
2.3X the width, in NJ-90aa length is only 
1.7X width, difference possibly due to an- 
gles of observation. WINGS: Forewing with 
vein C not reaching pterostigma, vein R ta- 
pering out midway between pterostigma and 
apex of Rs. Vein M + Im-cu with slight 
bend in middle, but no extra crossvein in- 
tersecting submarginal cell-1. Discal cell 
and subdiscal cell-1 trapezoidal. Hindwing 
with apical half of posterior margin acute 
and very straight; 10 minute apical hamuli, 
no proximal hamuli. 

CASTER: First segment 1.2-1.3X length of 
petiole, with slight constriction between gas- 
ter segments 1 and 2. Genitalia best seen in 
ventral view of NJ-90bb, with two pairs of 
lobes apparent: anterior pair slightly clavate, 
posterior pair with apices tapered. 

HOLOTYPE: AMNH NJ-90bb, a large, 
completely preserved male in a large, ex- 
tensively fractured, clear yellow piece of 
amber. Piece AMNH NJ-90 is one of the 
most remarkable pieces of New Jersey am- 
ber discovered thus far, containing 40 
whole organism inclusions, including the 
oldest fossil mushrooms (Hibbett et al., 



1996) (details of the piece are presented 
elsewhere [Grimaldi, 1997]). A large sliver 
from the entire piece, measuring 30 X 30 
X 8 mm, was vacuum-embedded, and the 
portion with the ant isolated by cutting out 
a pielike slice. One surface of the slice with 
the ant is irregular and coarsely ground, re- 
quiring glycerine with a glass coverslip on 
top for viewing the inclusion. Observing 
the wing venation requires viewing from 
both sides. 

ETYMOLOGY: Patronym in recognition of 
the collecting efforts of Gerard R. Case. 

OTHER SPECIMENS: NJ-90aa. A very par- 
tial male in a thin, chipped, clear yellow 
piece 10 X 6 X 2 mm, which also contains 
the remains of a very large insect unidenti- 
fiable to order. The dorsal portion of the 
ant's alitrunk is lost at the surface of the 
amber, the head is completely gone, and 
only one-third of the wing is preserved. 
However, the entire fore and mid legs are 
well preserved and the hind legs up to the 
femur. The petiole and base of the gaster are 
well preserved, and have proportions very 
similar to that of specimen NJ-90bb. That, 
plus the fact that both specimens came from 
the same large piece, makes it almost certain 
they are the same species, perhaps even 
males from a swarm. 

DISCUSSION: Wilson et al. (1967b) dis- 
cussed the similarities between Sphecomyr- 
ma and amblyoponines, the latter being the 
most primitive or among the most primitive 
"poneroids," by virtue of the petiole being 
broadly attached to the gaster (much more 
so than in Sphecomyrma or Cretomyrma). 
Interestingly, they mentioned that "one 
character that has never received any par- 
ticular attention is the form of the ambly- 
oponine male mandibles ..." which are 
"narrow . . . sometimes bidentate, and 
sometimes tapering to a single acute point 
. . . [and] close tightly against the . . . clyp- 
eal margin." This is the situation in Baik- 



Fig. 5. Baikurus casei, n. sp. a-c. Holotype (AMNH NJ-90bb). a. Left habitus, with a slightly ventral 
view, also showing details of genitalia. b. Oblique dorsal view of head. c. Oblique dorsal view of gaster 
and petiole, d. Incomplete specimen (AMNH NJ-90aa), showing petiole, legs, and portions of alitrunk 
and gaster. Scales = 0.5 mm. 



AMERICAN MUSEUM NOVITATES 



NO. 3208 



uris, which also has a slight constriction 
between gaster segments 1 and 2. 

GENUS? 
Figures Id, 6, 13c 

DESCRIPTION: Male, AMNH NJ-107: A 
virtually complete specimen in a small, 
clear yellow chip of amber, 7X9X3 mm, 
missing distal portions of forelegs, anten- 
nae distal to first two segments. 

HEAD: Eyes large, oval, posterior margin 
not emarginate. Position of specimen in the 
amber prevents measurements on proportions 
of the eye and head. Mouthparts largely ob- 
scured by forthy coating, although two pairs 
palps protrude, each with four visible seg- 
ments. Only three basal segments of right an- 
tenna remain, the pedicel being very short 
(ca. 0.3 X length of scape). If portion of the 
right antenna distal to pedicel is a complete 
first flagellomere, it is relatively short (ca. 
2.2X length of pedicel). 

ALITRUNK: Mesonotum with spare, short, 
erect hairs, cuticle otherwise devoid of ml- 
crotrichia. Scutellum with shallow trans- 
verse trough on anterior margin, containing 
row of 5 pits; pair of widely separated, fine 
setae on dorsal surface. Mesothoracic spi- 
racle recessed in deep, large pit. Propo- 
deum large; spiracle centrally placed and 
aperture not slitlike (no flap covers the ap- 
erture), with pair of fine setae dorsally. 
Posterior face of propodeum with very 
lightly rugose oval area, bordered by 8 
erect fine setae. Petiole relatively short; 
conically shaped; narrow and articulating 
with propodeum, with a central ring of 8 
fine setae. Where gaster articulates with 
petiole, short collar is formed on anterior 
margin of first gaster segment. LEGS: Fore- 
leg with apical tibial spur and proximal tar- 
sal segment with basal "kink" and comb 
of 8-10 fine setae that oppose spur (anten- 
nal cleaner). Mid and hind tibia each with 
pair of apical spurs, one spur half the 
length of other. Mid and hind femora with 
short trochantellus at proximal end, faintly 
sutured from femur. Tarsal claws with small 
preapical tooth. 

WINGS: Shape of submarginal cell most 
like that of Baikurus casei, with slight bend 
in vein M + Im-cu. Easily distinguished 



from B. casei and other Cretaceous ant 
wings by the open discal cell- 1 (lacking the 
apical cross vein) and subdiscal cell-1 not 
being trapezoidal but with the anterior vein 
curved down toward posterior vein. 

DISCUSSION: Although this male is distinct 
from the Baikuris and probably Sphecomyr- 
ma males also in the deposit, we prefer not 
to formally name it. Ant taxonomy presently 
relies on diagnoses using worker characters, 
which is a criterion that should apply to ex- 
tinct taxa until modern taxa are better sur- 
veyed for males. Genera named for isolated 
males and workers are very likely to lead to 
a confusing taxonomy. We describe a new 
species of Baikuris above, based on males, 
because this genus is presently diagnosed 
only by males. 

Unfortunately, critical features of the an- 
tenna are lost that would confirm this ant 
as a sphecomyrmine, which appears very 
likely. It primitively possesses the trochan- 
tellus (Sphecomyrma lacks a trochantellus), 
and wing venation although with a few 
deviant features is very similar to that of 
other male sphecomyrmines. The apparent 
absence of a distal spur on vein CuA would 
also place this ant in the Sphecomyrminae. 

WING VENATION: Perhaps not surprisingly, 
there is little comparative work on the wing 
venation in the living Formicidae. Ant sys- 
tematists have concentrated their collecting, 
and thus the systematic characters, on the ap- 
terous workers. One of the few studies on 
comparative wing venation was done by 
Brown and Nutting (1949); on which many 
of our comments on Cretaceous taxa are 
based. 

In general, the venation of aculeates is 
rather conservative, particularly so in the 
Formicidae. The discal/discoidal cell of the 
forewing, for example is virtually constant, 
very rarely lost in ants. The second sub- 
marginal cell ("discal cell 2") is apo- 
morphically absent in some ants; the cell is 
present in many primitive ants and in the 
Cretaceous taxa. But, valuable insight in 
sphecomyrmine monophyly, for example, 
was provided by wing venation: loss of the 
evanescent distal section of vein Cu-A 
(also termed Cu-Al). Conversely, wing ve- 
nation reinforces the primitive nature of 
sphecomyrmines. The presence of vein Ir, 



AMERICAN MUSEUM NOVITATES 



NO. 3208 



for example, which bisects the submarginal 
cell, is seen in primitive, extant Myrmeci- 
inae and some Ponerinae, as well as in the 
Cretaceous Baikuris mandibularis . Loss of 
this vein occurs early in ant cladogenesis. 
Likewise, the absence of vein Mf2 (the dis- 
tal wall of the second submarginal cell) is 
apomorphic, but the vein is present in Baik- 
uris, Dlusskyidris, and the apparent male 
Sphecomyrma reported here. 

Brownimecia, new genus 

Distinguished from other Cre- 
taceous worker ants by antenna (seen in both 
specimens) and the mandibles (seen in 
AMNH NJ-667). Antenna distinctly clubbed, 

__:__, a___,i ..: .u- w j dth of basal 

s long, thin, scim- 
:, without teeth 

or crenulations, but with oral surface bearing 

setae. Gaster with 
slight but definite constriction between first 
and second segment (abdominal segments III 
and IV). 

ETYMOLOGY: For the renowned system- 
atist on ants, the late William L. Brown, Jr., 
"'horn the senior author had the pleasure of 



wing mis manu- 
was able to learn 
of the discoveries and see the patronym in 
his honor. 

TYPE SPECIES: B. clavata, new species. 

Brownimecia clavata, new species 
Figures le, f; 711 

DESCRIPTION: Body largely covered with 
microtrichia, sparsest on notum, absent on 
propodeum. 

HEAD: Large, width (excluding eyes) 
1.6X greatest width of notum. Eye rela- 
tively small, length 0.3X length of head, 
virtually round, with about 100 ommatidia. 
Ocelli not observed. Postocciput with re- 
cessed, trapezoidal area bearing no micro- 
trichia. Antenna distinctively clubbed, with 
apical segment 2. OX width of basal flagel- 
lar segments plus pedicel. Relative lengths 
of funicular segments: for AMNH NJ-231: 
pedicel 2.1 : flagellomere-I 1.6: 1.0 : 1.1. : 
1.3 : 1.3 : 1.1 : 1.3 : 1.3 : 1.6 :apical fla- 



gellomere 2.3. For AMNH NJ-667: pedicel 
1.4 : 1.8 : 1.2 : 1 : 1 : 1 : 1: 1.2 : 1.2 : 1.7 
: apical flagellomere 3.2. Shortest funicular 
segments are the third through sixth; sec- 
ond funicular segment slightly swollen in 
middle. Scape lost in AMNH NJ-231; in 
AMNH NJ-667 scape is 0.4 X length of fu- 
niculus, 1.7X height of eye. Mouthparts in- 
tact only in NJ-667. Clypeus shallow and 
very broad, nearly width of head. Mandi- 
bles distinctive: apical half of left mandible 
protruding beyond clypeus (but best seen in 
lateral view of specimen), right mandible 
adpressed against ant 
eus, but oral surface visible in anterodorsal 
view: mandibles are narrow, toothless, 
scimitarshaped, crossing approximately at 
midlength, oral surface with about 30 short 
and spiculelike setae. Basal portion of gena 
with a lateral tooth. Palps long and thin: 
labial palp with 4 segments (basal one min- 
ute), maxillary palp with 2 visible seg- 
ments (probably more present). Fimbricate 
glossa present (observable only in lateral 
view). 

ALITRUNK: Dorsally constricted at level of 
middle of mesonotum; pronotum and meso- 
notum with sparse microtrichia, mesonotum 
with flat, oval-shaped dorsal surface. M^atVir.. 
racic spiracle raised on small cone-sha^ 
tuberance. Articulation between nrot 
and mesonotum la^ 
visible). Propodeum with dome smooth and 
hairless, in lateral view helmet-shaped. Pro- 
podeal spiracle situated in middle. Metapleural 
gland orifice obscured by froth of fine bubbles, 
but transverse ridge to MGO is visible (this is 
also seen in a scanning electron micrograph of 
the cavity of AMNH NJ-231, see below). Area 
surrounding the MGO not conspicuously 
raised into a bulla. Legs densely covered with 
microtrichia, except coxae. Calcars on mid 
and hind tibiae. Pretarsal claw with preapical 
tooth. Petiole with dome of node not hemi- 
spherical but slightly pointed, microtrichose, 
with pair of fine setae near summit. Petiolar 
spiracle at basal third of petiole. Petiole nar- 
rowly attached to propodeum, broadly at- 
tached to gaster. 

GASTER: Helcium well developed, with 
slight crenulations on gastral edge (best 
seen in SEMs). Abdominal segment 3 (gas- 
ter segment 1) microsetose, 1.5X length of 



GRIMALDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 



petiole, with slight constriction between 
abdominal segments 3 and 4. Abdomen lost 
at surface of amber in AMNH NJ-231. In 
AMNH NJ-667, tip of abdomen is obscured 
by a coating of froth, through which a sting 
is discernible. 

Measurements (in mm) 



holotype 



paratype 



Body length 3.43 

Head width 0.79 

Scape length 0.52 

Funiculus length 1.02 

Alitrunk length 1.32 1.20 

Caster length 1.29 

TYPES: Holotype, AMNH NJ-667, a su- 
perbly preserved, complete specimen in a 
clear yellow piece of amber. It was vacuum 
embedded for better observation of certain 
details. Collected by Yale Goldman at White 
Oaks site. 

Paratype, partial remains of a worker, 
AMNH NJ-231 in a tiny, oval, clear yellow 
piece, only 2X3X6 mm. We are grateful 
to Alan Graffam of Geological Enterprises 
(Ardmore, OK), who sent it to us, having ob- 
tained it from a private collector whose iden- 
tity was not disclosed. Almost undoubtedly 
this piece was collected at the White Oaks 
site, since this is where virtually all New Jer- 
sey amber collectors obtained their material. 
Someone had obviously tumbled the piece 
since the surface is rather polished, and the 
ant is merely an exposed and clean cast on 
the flat surface of the piece. The front legs are 
virtually all gone, the mid and hind legs lost 
distally from the middle of the tibiae. A cast 
of the dorsal part of the head remains (in- 
cluding the ommatidia), but the ventral half 
of the head is lost. Funiculus of left antenna 
is intact, but scape is largely lost (the right 
antenna is entirely lost). The entire alitrunk is 
largely intact within the amber. Exposure of 
the specimen is fortuitous, since it exposed 
casts of some critical areas and details, partic- 
ularly the petiole, which allowed viewing 
with an SEM. The specimen was first gold 
coated for SEM and examined at low voltage 
(5 kV) using a Zeiss DSM-1 scanning EM. 
Details of the exposed cuticle were observa- 
ble, the most significant being the propodeum, 
petiole, and helcium. The specimen was then 



vacuum embedded, trimmed close and paral- 
lel to the lateral and dorsal surfaces of the 
body, which exposed windows into the gold- 
coated amber. Surprisingly, translucency of 
the coated surface was retained. 

ETYMOLOGY: In reference to the distinc- 
tively clubbed antennae. 

DISCUSSION: Brownimecia is not referable 
to the Sphecomyrminae, by virtue of its more 
derived proportions of antennal segments, the 
pedicel being relatively longer and the first 
flagellomere relatively shorter than in all the 
other sphecomyrmine workers in Canadian, 
Siberian, and New Jersey ambers. The scape 
is much longer in proportion to the funiculus 
(1:2) than in the worker sphecomyrmines 
(e.g., 1:4 in Sphecomyrma freyi). The man- 
dibles are distinctively autapomorphic, and 
the clavate funiculus is found in most living 
ants, probably a groundplan feature of the liv- 
ing ants. The slight gastric constriction indi- 
cates Brownimecia to be a primitive ponerine. 

Ward (1994) discussed many characters of 
primitive ponerines, and amblyoponines in 
particular, which are useful in assessing the 
phylogenetic position of Brownimecia. One 
feature that he did not mention, however, was 
genal spurs, which occur in some ambly- 
oponines like Amblyopone and Mystrium. 
Other features that Brownimecia shares with 
certain amblyoponines are: mandibles nar- 
row, long, articulation points very widely 
separated, and mandibles extensively cross- 
ing (again, much like Amblyopone and Mys- 
trium); eyes small; and the mesonotum short 
and flattened. In virtually all other respects, 
though, Brownimecia is extremely primitive 
compared to extant Amblyoponini or Poner- 
inae: the genus lacks tergosternal fusion of 
abdominal segments III and IV, anterior mar- 
gin of the clypeus is simple (without peglike 
setae), and the eyes are situated near the mid- 
dle of the sides of the head (not slightly pos- 
terior to the middle). Unfortunately, some 
characters discussed by Ward (1994) could 
not be observed in either specimen of 
Brownimecia: metacoxal cavities, metapleu- 
ral gland orifice, abdominal sternum and ter- 
gum II, stridulatory file on abdominal termite 
IV, and details of the sting. 

Very recently, Dlussky (1996) described a 
bizarre ant in the Sphecomyrminae. His re- 
port is of exceptional interest because of the 



AMERICAN MUSEUM NOVITATES 



NO. 3208 





' *** *S ,,.- 



Figs. 8-10. Scanning electron micrographs of Brownimecia clavata, paratype AMNH NJ-231. 8: 
(above) Entire specimen, as exposed on surface of amber (compare fig. 7). Scale = 200 jjun. 



structure of the ant, and its preservation in 
Burmese amber. Moreover, it had been sug- 
gested to us that perhaps Haidomyrmex Dlus- 
sky and Brownimecia were closely related, 
on the basis of the bizarre, sickle-shaped, 
toothless mandibles (they also both possess 
a narrow, elongate pronotal "neck," and 
small eyes). 

First, a great deal of mystique has sur- 



rounded amber from northern Burma, which 
was mined for at least a millennium until the 
early quarter of the 20th century (Grimaldi, 
1996). The only museum with a significant 
collection of the material having inclusions 
is the Natural History Museum, London. 
Cockerell (1922), who originally studied the 
NHM material, stated that the material was 
no younger than mid-Eocene, but, unfortu- 



GRIM AUDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 



Figs. 9, 10. 9: Detail of propodeum, showing 
channels leading to the metapleural gland open- 
ing. 10: Petiole, showing crenulate helcium. 
Scales = 50 jrni. 



nately, the stratigraphy of Burmese amber 
has never been reliably determined. Recent- 
ly, Rasnitsyn (1996) surveyed 1200 arthro- 
pod inclusions in the NHM Burmese amber 
collection, and concluded, at least on the ba- 
sis of the Hymenoptera (including the ants 
described by Dlussky), that the amber was 
most likely upper Cretaceous in origin. A 
sphecomyrmine in Burmese amber would 
suggest a Cretaceous age of this amber, pro- 



viding the ant is accurately placed (see be- 
low). Composition of the Burmese amber, 
based on visual inspection by D. Grimaldi 
and pyrolysis gas chromatography by Alex- 
ander Shedrinsky (unpubl.), suggests it to be 
Tertiary. Granted, there are no means pres- 
ently known that perfectly correlate amber's 
color, hardness, brittleness, or any other 
physical and chemical features of "matura- 
tion," with age. Nonetheless, all Cretaceous 
ambers are brittle and often highly fractured; 
Burmese amber is soft enough that it had 
been used for carvings, as early as 1000 A.D. 
and before Baltic amber became so available 
(Grimaldi, 1996). The general features of 
Burmese amber suggest a Paleocene or early 
Eocene age. 

Secondly, the ant itself, Haidomyrmex, is 
startling: it possesses small eyes, huge genae, 
and huge, L-shaped mandibles. Depth and 
width of the mandible are approximately 
equal to those of the ant's cranium; the outer 
margin of the mandible has a squared angle, 
the inner margin being curved and toothless. 
These mandibles may have functioned in a 
manner analogous to that of other, living ants 
with "trap jaws," where long, fine hairs trig- 
ger the mandibles to suddenly snap closed. 
Haidomyrmex has a pair of such hairs on the 
margin of the clypeus. 

We doubt that this new genus is in the 
Sphecomyrminae, for the lack of ocelli and 
structure of the head, and a scape that is dis- 
tinctly shorter than any definitive, Cretaceous 
sphecomyrmine. Its lack of a trochantellus 
(cited by Dlussky) does not differ from the 
situation in Sphecomyrma (reported here in 
the new worker of S. freyi). Clearly, Haido- 
myrmex and Brownimecia are unrelated, 
based at the very least on proportions of the 
antennae, apparent lack of a gastral constric- 
tion in Haidomyrmex, position of spiracles, 
and pilosity of the alitrunk. Haidomyrmex 
may be a sphecomyrmine, but until more de- 
finitive worker synapomorphies are discov- 
ered for the subfamily, its exact position will 
remain obscure. 

PHYLOGENETICS 

It is virtually self-evident that the fullest 
systematic value of fossils can be revealed 
by an understanding of phylogenetic posi- 



AMERICAN MUSEUM NOVITATES 



NO. 3208 






Fig. 11. Brownimecia clavata, holotype: lateral habitus. Scale line: 0.5 mm (for habitus). Detail of 
left mandible (slightly more magnified) from anterodorsal view, showing spiculate oral surface. 



tion. Species diversity and rich morphology 
of modern forms have dictated the bases for 
insect phylogenies, including the Hymenop- 
tera. Indeed, the lack of many characters in 
fossil forms compromises the resolution of 
phylogenetic hypotheses (Wheeler, 1992), 
and the placement of fossils accordingly de- 
pends on preserved characters whose phylo- 
genetic values are known. 

The most comprehensive and widely cited 
study on ant phylogeny is by Baroni Urbani 
et al. (1992), which provides a cladistic 
framework for our discussion of the positions 
of Sphecomyrma and Brownimecia, the old- 
est definitive worker ants. First, we discuss 
some character receding for the matrix of 
Baroni Urbani et al. (1992), reanalyze the 
slightly revised data, then discuss implica- 
tions of the revised (albeit, still unstable) 
cladograms for placing the two Cretaceous 
genera. 



METHODS: Cladistic analysis (Hennig, 
1966) was implemented using the programs 
Hennig86 (Farris, 1988), Nona (Goloboff, 
1996a), Phast (Goloboff, 1996b), Dada (Nix- 
on, 1995a) and Clados (Nixon, 1995b). Dada 
was used for data matrix editing, and as a 
shell for submission of character matrices to 
Hennig86, Nona, and Clados. Hennig86 was 
used for cladogram construction, and succes- 
sive weighting with the rescaled consistency 
index (Farris, 1989). Typically, the multiple 
tree search command was applied with 
branch swapping (mhennig*), followed by 
branch breaking (bb*). This procedure was 
supplemented by use of the "autospin" fea- 
ture of Dada, which randomly shuffles order 
of taxa in the matrix and resubmits the ma- 
trix to Hennig86. Autospin was run 100 
times with mhennig* to try to find separate 
stands of multiple equally parsimonious 
trees, with the results all subjected to bb*. 



GRIMALDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 



Sphecomyrma? AMNHNJ-242 



Baikuris easel AMNH NJ-90bb 



Fig. 12. Fore and hind wing venation of male sphecomyrmines. a. AMNH NJ-242 (Sphecomyrmal). 
b. Baikurus casei, holotype, AMNH NJ-90bb. 



Because Hennig86 does not support analysis 
of polymorphic data, such characters are re- 
coded as missing by Dada before submission 
to Hennig86. Results of Hennig86 analyses 
were checked with Nona, which does support 
polymorphisms. Because Hennig86 also out- 
puts semistrictly supported trees (with reso- 
lutions supported by just one among the pos- 
sible optimizations; see Nixon and Carpenter, 



1996), Nona was used as a filter for strictly 
supported trees, as described by Carpenter 
(1996), using the "unique" command after 
reading in Hennig86 trees. Nona was also 
used for cladogram construction, by applying 
the multiple tree search command via ran- 
dom addition sequence, with tree-bisection- 
reconnection branch swapping (mult* with 
20-50 random additions), followed by ad- 



AMERICAN MUSEUM NOVITATES 



NO. 3208 



Baikuris mandibularis 



Formicium simillimum 

Fig. 13. Wing venation of male sphecomymines in upper Cretaceous amber from Taymyr, Siberia 
(a,d), New Jersey (c), and the Eocene Formiciinae (Messel, Germany; redrawn from Lutz, 1988). ? 
Baikuris mandibularis Dlussky (redrawn from Dlussky, 1987 [fig. 2]). b. Formicium simillimum. t. 
AMNH NJ-107, genus unknown, d. Dlusskyidris zherichini (Dlussky) (redrawn from Dlusskv 1975 [fie 
130]). ' 



ditional branch swapping (command max*). 
Results were filtered for collapsibility as de- 
scribed by Nixon and Carpenter (1996), us- 
ing the "ksv" and "best" commands on tree 
files. Clados was used for tree visualization 
and manipulation, checking for strict support, 
calculation of consensus trees, and printing. 
Bremer support values (Bremer, 1988) were 
calculated using Phast, by invoking the 
"bsupport" command and searching on sub- 
optimal trees up to six steps longer. 

The following analyses were based on 



modifications to the original data matrix by 
Baroni Urbani et al. (1992) (see appendix, 
table 1). 

1 . Character 30 of the matrix was receded 
for Leptanilloidinae (1 instead of 0), a cor- 
rection suggested by Phil Ward (personal 
commun.). The results from analysis of the 
corrected matrix are shown, which are essen- 
tially the same as those reported by Baroni 
Urbani et al. (1992). 

2. The corrected data matrix was expand- 



GRIMALDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 



AMNHNJ-107 



Dlusskyidris zherikhini 



Fig. 13. (Continued) 



ed by the addition of Adetomyrma, a genus 
that complicates the proposed phylogeny of 
Baroni Urbani et al, as this new genus does 
not fall within their interpretation of the Po- 
nerinae (Ward, 1994). 



3. The following characters used in the 
matrix of Baroni Urbani et al (1992) were 
receded, due to unnecessary splitting of mul- 
tistate characters: 11 and 12 (new character 
9): metapleural gland absent (0), present 



AMERICAN MUSEUM NOVITATES 



NO. 3208 



Characters 1-62 

Multistate characters are treated as nonadditive, as noted. A question mark denotes an unknown state, 
while a dash denotes an inapplicable trait. An asterisk denotes a polymorphism showing all applicable 
states; a dollar sign denotes a subset polymorphism. 



CHARACTER LIST 

1. Head: hypognathous (0); prognathous (1). 

2. Labrum: without rows of peglike teeth (0); with 2 rows of peglike teeth (1). 

3. Labium: with pair of cylindrical pegs (0); without (1). 

4. Clypeus: normally developed (0); extremely reduced (1). 

5. Clypeus: rounded (0); with flat medial surface (10. 

6. Worker eyes: present (0); absent (1). 

7. Malar area in dorsal view: visible (0); reduced (1). 

8. Antennal socket: exposed (0); not covered (1); covered by torulus (2) [nonadditive]. 

9. Worker promesonotal suture: mobile (0); fused (1). 

10. Metapleural gland: absent (0); not covered (1); covered by cuticular flange (2) [nonadditive]. 

1 1. Metacoxal cavities: open or sutured (0); closed (1). 

12. Metatibial gland: absent (0); present (1). 

13. Basitarsal sulcus on metatarsi: absent (0); present (1). 

14. Petiole: without tergosternal fusion (0); with (1). 

15. Worker helcium: unfused (0); fused (1). 

16. Helcium sternite: protruding ventrally (0); not (1). 

17. Helcium sternite: overlapped laterally by pretergite (0); not (1). 

18. Worker spiracle of III: situated posteriorly (0); situated close to anterior face of tergite (1). 

19. Worker diameter of segment III: subequal to segment IV (0); smaller (1). 

20. Worker segment III: tergum and sternum not fused (0); with complete fusion (10). 

21. Worker dorsal stridulatory organ: absent (0); present between segments III & IV (1). 

22. Worker ventral stridulatory organ: absent (0); present between segments III & IV (1). 

23. Segment IV: without presclerites (0); with presternite & pretergite, unfused (1); fused (2) [nonadditive 

24. Segment IV presclerite length: <.5 IV (0); >.5 IV (1). 



GRIMALDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 



without a dorsally covering flange (1), cov- 
ered with a flange (2); 25 and 26 (new char- 
acter 22): abdominal segment IV without 
presclerites (0), with presclerites and preter- 
gites unfused (1), with presclerites and pre- 
tergites fused (2). Baroni Urbani et al. (1992) 
scored only binary variables in their data ma- 
trix, but in doing so, they potentially lost in- 
formation (Pogue and Mickevich, 1990). 
Multistate characters are readily analyzed as 
additive, if states are in a morphocline or 
similarity is nested, or as nonadditive. The 
two new variables were treated as nonaddi- 



The following characters were deleted: 9, 
the "short scape" is difficult to define, and 
furthermore present in Leptanilloidinae. 
Dlussky (1983) and Baroni Urbani (1989) in- 
troduced this character essentially as a sur- 
rogate for social behavior (also see our pre- 
vious discussion, p. 8). 51, basal hamuli have 
not been seen in Amblyopone spp. and in 
Nothomyrmecia. 67 and 68, we consider the 
empirical basis too meager to include these 
two behavioral characters in the analyses. 

Polymorphic characters were resolved for 
the ponerines by splitting the ponerines into 
monomorphic subtaxa (admittedly, still a slim 



25. Presternite of IV: subequal to pretergite (0); shorter (1). 

26. Segment IV tergum & sternum: not fused (0); completely fused (1). 

27. Spiracles of V-VII: not visible (0); visible (1). 

28. Pygidium: not bidentate (0); bidentate (1). 

29. Pygidial spines: absent (0); present (1). 

30. Pygidial reduction: absent (0); narrow U-shaped sclerite (1). 

31. Worker pygidium: not covered by tergum VI (0); covered (10. 

32. Acidopore: absent (0); present (1). 

33. Sting and lancets: articulated (0); disarticulated (1). 

34. Furcula: well developed (0); reduced to absent (1). 

35. Proventriculus: flaccid (0); sclerotized (1). 

36. Dufour gland epithelium: not crenellate (0); crenellate (1). 

37. Pavan's gland: absent (0); present (1). 

38. Sting bulb gland: absent (0); present (1). 

39. Worker-gyne dimorphism: limited to wings & alar sclerites (0); pronounced (1). 

40. Gyne: not dichthadiiform (0); dichthadiiform (1). 

41. Wing venation: not crowded (0); crowded (1). 

42. Gyne segment III: poorly differentiated (0); forming postpetiole (1). 

43. Bursa copulatrix: not exposed (0); exposed (1). 

44. Male antennal sockets: clypeus visible (0); at anterior margin of head (1). 

45. Male head incision: absent (0); present posteriorly (1). 

46. Male antennal scape: shorter than next 2 articles (0); longer (1). 

47. Male forewing pterostigma: present (0); absent (1). 

48. Male hindwing jugal lobe: present (0); absent (1). 

49. Male propodeal spiracle: slit-shaped (0); round to elliptical (1). 

50. Male segment III: no tergosternal fusion (0); present (1). 

51. Male segment IV: without presclerites (0); with differentiated presclerites (1). 

52. Male tergite VII: sclerotized (0); desclerotized (1). 

53. Male sternite VIII: without anterior apodemes (0); with long anterior apodemes (1). 

54. Male cerci: present (0); absent (1). 

55. Male subgenital plate: not biaculeate (0); biaculeate (1). 

56. Lamina annularis: thin (0); enlarged (1). 

57. Male genitalia: retractile (0); not retractile (1). 

58. Male genitalia size: normal (0); larger than rest of gaster (1). 

59. Larval hemolymph feeding organ: absent (0); present on abdominal segment III (1). 

60. Larval mandibles: inner masticatory margin (0); outer (1). 

61. Trophothylax: absent (0); present (1). 

62. Pupa: with cocoon (0); naked (1). 



AMERICAN MUSEUM NOVITATES 



NO. 3208 



-Vespidae 

Bradynobaenidae 



-Formiciinae 



radynobaen 
Formici 
IT 1-r- 



Formicinae 
Aneuretinae 
Dolichodr- J - 



Myrmiciru 
-l-i Pseudomyrmecina 



1-1 iviyrmeciiri.L 
Nothomyrmec: 
I Prionomyrmec 



Anomalomyrmini 



rapacnyinae 

Icitoninae 
1 1-, Aenictinae 



-Aneuretinae 



-Dolichoderinae 



-Formicinae 



-Myrmicinae 



-Pseudomyrmecinae 
I Myrmeciini 



-Nothomyrmeciinae 



-Prionomyrmecini 



-Apomyrmini 



-Ponerinae 



-Anomalomyrmini 
Leptanillini 



-Cerapachyinae 



-Leptanilloides 



-Ecitoninae 



-Aenictinae 



Aenictogiton 
Dorylinae 



Fig. 14. Consensus cladogram based on successive weighting of 54 trees with length of 537, using 
data revised from Baroni Urbani et al. (1992). 

Fig. 15. Brerner support values for cladogram in fig. 14. 



sampling), which is preferable to the ambiguity 
introduced by polymorphic scorings (Nixon 
and Davis, 1991; Nixon, 1996). For that rea- 
son, Paraponera, Platythyrea, and Amblyopo- 
ne were scored and included. For the out- 
groups, Vespidae and Bradynobaenidae, some 



polymorphism was resolved by extrapolation, 
based on the groundplans established by 
Brothers and Carpenter (1993). 

4. The New Jersey amber fossils Spheco- 
myrma and Brownimecia were added to the 



GRIMALDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 






Vespidae 
-Bradynobaenidae 



-Formiciinae 



Bradynobaenidae 
-IT Formiciinae 



Nothomyrmeciinae 

-Myrmeciini 
-Prionomyrmecini 



-Myrmicinae 



Pseudomyrmecinae 
-Aneuretinae 

Dolichoderinae 

Formicinae 

-Adetomyrma 
I Apomyrmini 



-Ponerinae 



Aneuretinae 
' Dolichoderinae 
Myrmicinae 
Pseudomyrmecinae 
-1- 

I Nothomyrmeciinae 
' Prionomyrmecini 
l-i Adetomyrma 

' l-i Apomyrmini 

' l-i Ponerinae 

l-i Anomalomyrmin: 

' Leptanillini 



Anomalomyrmini 

Leptanillini 

-Leptanilloides 



taniiioiaes 

Ecitoninae 

l-i Aenicti 



-Cerapachyinae 
-Ecitoninae 
Aenictinae 
Aenictogiton 
Dorylinae 



Fig. 16. Consensus cladogram with the Malagasy genus Adetomyrma added. 
Fig. 17. Bremer support values for cladogram in fig. 16. 



matrix, scoring characters for the worker of 
Sphecomyrma and the apparent male. 

5. Finally, all taxa with more than 70% 
missing values were excluded, i.e., Formici- 
inae (81%), Prionomyrmecinae (75%), and 
Aenictogitoninae (71%). The overall effect 



of high levels of missing data is to weaken 
the application of the parsimony criterion 
(Nixon, 1996), and this is seen in the present 
study, where the taxon Formiciinae (an Eo- 
cene compression fossil) in particular intro- 
duces instability into the results, with no dis- 
cernible benefit. 



AMERICAN MUSEUM NOVITATES 



NO. 3208 



-Vespidae 



Bradynobaenidae 



l-i Myrmicinae 
' Pseudomyrmecinae 



faraponera 
-l-i Ponerinae 
I Platythyree 



-Bradynobaenidae 



-Formiciinae 



-Paraponera 
-Amblyopone 



Ponerinae 



-Platythyrea 

Formicinae 
Aneuretinae 

Dolichoderinae 

Myrmicinae 

Pseudomyrmecinae 

I Nothomyrmeciinae 



| | Myrmeciini 

Prionomyrmecini 
-Adetomyrma 



Apomyrmini 

I Anomalomyrmini 

Leptanillini 

I Leptanilloides 



-Cerapachyinae 



l-i Ano 

I 1-^- 



Lieptanillini 

2-1 Leptanilloides 

' 1-j l-i Cerapachyinae 

' Ecitoninae 

' 2-i Aenictogiton 

' l-i Aenictinae 



Ecitoninae 

-Aenictogiton 
Aenictinae 
Dorylinae 



Fig. 18. Cladogram using revised characters and the ponerines divided into three smaller taxa. Strict 
consensus of successively weighted trees. 

Fig. 19. Bremer support values for cladogram in fig. 18. 



CLADISTIC RESULTS 

1. The reanalysis of Baroni Urban! et al.'s 
revised data resulted in 144 cladograms of 
length 110; the original result was 72 clado- 
grams of that length. However, of these 144 



cladograms, only eight are strictly supported 
when filtered by Nona (four for the original, 
uncorrected matrix). Successive weighting 
results in 54 cladograms of weighted length 
537; their consensus tree (fig. 14) is slightly 
less resolved than the consensus presented by 



GRIMALDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 



Baroni Urbani et al. (1992: fig. 4), with Lep- 
tanilloides and Cerapachyinae now part of a 
trifurcation. 

Baroni Urbani et al. (1992) reported var- 
ious statistical tests of "structure" in their 
matrix. They cited the FTP test (Faith and 
Cranston, 1991) as indicating "significant" 
phylogenetic structure in the data, but the 
problems and validity of that test have been 
presented (Kallersjo et al., 1992; Carpenter, 
1997). Baroni Urbani et al. also reported 
results of bootstrapping (Felsenstein, 
1985), another technique that has been cri- 
tiqued (Carpenter, 1992); but, criticism 
aside, the bootstrapping result (Baroni Ur- 
bani et al., 1992: fig. 7) was notable for 
showing no "significant" nodes. Indeed, 
their bootstrapped tree, a fully resolved ma- 
jority-rule consensus, contained a great ma- 
jority of nodi >>.< 

less than 50%! Althou .. , _, r ._ 

sented, this is certainly a misapplication: 
groups with frequencies less than 50% may 
be contradicted more often than they ap- 
pear (see examples in Farris et al., 1996). 
The Bremer support was calculated for the 
data matrix, and the results (fig. 15) con- 
firm low support for all groupings only 
one clade has a Bremer support of as much 
as two steps, all other nodes being sup- 
ported by one step, or with no support (un- 
resolved in that figure). 

2. The addition of the data for the living 
Malagasy genus Adetomyra produced a 
rather different tree (fig. 16). Hennig86 re- 
ported 264 cladograms of length 1 14, con- 
sistency index 0.59, and retention index of 
0.71. Only 40 of these trees are strictly sup- 
ported, and successive weighting resulted 
in six cladograms of weighted length 532. 
The consensus of these six cladograms (fig. 

16) shows major rearrangements of basal 
nodes, and that the enigmatic, apparent po- 
nerine genus Adetomyra is not the sister 
group of the Ponerinae, as already indicat- 
ed by Ward (1994). Bremer supports (fig. 

17) remain low. 

3. Receding of the abovementioned char- 
acters, and the addition of three more ponerine 
taxa produced yet another topology (fig. 18). 
Hennig86 reports four cladograms (with autos- 
pin) of length 121, consistency index 0.52, and 



retention index 0.69. Only two of these are 
strictly supported, and the results are stable to 
successive weighting (weighted length 468). 
The consensus tree of the two strictly support- 
ed trees is poorly resolved basally, but exam- 
ination of the underlying trees shows that this 
is caused by alternative placements of one tax- 
on: Formiciinae is either the sister group of 
Bradynobaenidae, or of Paraponera\ Clearly, 
that taxon is contributing little useful infor- 
mation. Aside from that (artifactual) instability, 
a notable difference is the grouping within the 
army ant clade sensu Bolton (cf. the position 
of Cerapachyinae). Bremer supports remain 
low, although now two clades have supports 
of two steps (fig. 19). 

4. The addition of the two fossil taxa, 
Brownimecia and Sphecomyrma, leads to a 

reDOrt Of 1?^ ^I^HrKrrQmc K\7 T-T^nnirrS/^ jx/ifrl-i 



retention index 0.68. Just 16 of these are 
strictly supported, and successive weighting 
results in 12 cladograms (weighting length 
470). The consensus of these 12 cladograms 
(fig. 20) is again poorly resolved basally, but 
again that results primarily from instability 
brought about by inclusion of the Formici- 
inae. The position of the sphecomyrmines is 
thus ambiguous, but Brownimecia turns out 
to be part of a distant ponerine clade. The 
Bremer supports did not change overall (fig. 
21). 

5. The deletion of taxa with more than 
70% missing values caused significant 
changes in topology, as predicted in simula 
tions by Wheeler (1992). Hennig86 reports 
356 cladograms of length 122, consistency 
index 0.50, and retention index 0.67. Just 82 
of these cladograms are strictly supported, 
and successive weighting results in 36 clado- 
grams (weighted length 449). The consensus 
of these 36 cladograms (fig. 22) is much bet- 
ter resolved. The basal formicid node is a 
quadritomy with Sphecomyrma, Myrmeciini 
+ Nothomyrmeciinae, Myrmicinae + Pseu- 
domyrmecinae, and the remaining taxa. 
Brownimecia is part of a larger ponerine 
clade, apparently a very basal member (not 
reflected in the cladistic analysis); and, there 
are two changes in the army ant clade (Apo- 
myrmini to Dorylinae). The Bremer supports 
(fig. 23) are low. 



AMERICAN MUSEUM NOVITATES 



NO. 3208 



Vespidae 

Bradynobaenidae 

-Formiciinae 
Sphecomyrma 
Paraponera 

Amblyopone 



-Ponerinae 



Bradynobaenida 



-H Platythyrea 

' Brownimecia 

Formicinae 

rAneuretinae 

Dolichoderinae 

. Myrmicinae 

Pseudomyrmecinae 

I Nothomyrmeciinae 

| | Myrmeciini 

-Prionomyrmecini 
-Adetomyrma 

I Apomyrmini 

I Anomalomyrmini 

Leptanillini 

' I Leptanilloides 



lonomyrmecin: 

I '" la 

| 1-| Myrraicinae 

domyrmecinae 
icinae 

leuretinae 
' Dolichoderinae 

Amblyopone 

Paraponera 

Ponerinae 

Platythyrea 



Cerapachyinae 
Ecitoninae 



-Aenictogiton 

I Aenictinae 

Dorylinae 



Apomyrmini 

LOmalomyrmini 
-l-i Leptanillini 

' 2-i Leptanilloides 

' l-i l-i Cerapachyinae 

1 Ecitoninae 

' 2-j Aenictogiton 

' l-i Aenictinae 

' Dorylinae 



Fig. 20. Consensus of 1 2 successively weighted cladograms, with the New Jersey amber Cretaceous 
fossils Sphecomyrma and Brownimecia incorporated. 

Fig. 21. Bremer support values for cladogram in fig. 20. 



GRIMALDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 



Vespidae 

Brady nobaenidae 



-Sphecomyrma 



Myrmeci: 
Not homy] 



lyopone 
Myrmicinae 
Pseudomyrmecir 



Myrmicinae 

-Pseudomyrmecinae 



Myrmeciini 

-Nothomyrmeciinae 

I Formicinae 

li Aneuretinae 

' Dolichoderinae 

I Amblyopone 

Paraponera 



1 HPIatythyrea 

' Brownimecia 
-Adetomyrma 




-Ponerinae 



Apomyrmini 

Anomalomyrmini 

Leptanillini 

I Leptanilloides 



-Cerapachyinae 
-Ecitoninae 
Aenictinae 
Dorylinae 



Fig. 22. Preferred cladogram: consensus of 36 successively weighted cladograms, deleting three taxa 
with >70% missing values (Formiciinae [Eocene compression fossil], and the living subfamilies Prion- 
omyrmecinae and Aenictogitoninae). 

Fig. 23. Bremer support values for cladogram in fig. 22. 



DISCUSSION: CLADISTICS 

Our preferred result (fig. 22) differs in 
some fundamental ways from that of Baroni 
Urbani et al. (their figs. 9-15). The grouping 
of army ants is stable through both analyses, 
reflecting the numerous synapomorphies re- 



vealed in the studies by Bolton (1994). Ad- 
etomyrma, however, replaces the Ponerinae 
as their sister group in figure 22, confirming 
Ward's (1994) comment that Adetomyra, if 
considered a ponerine, would render the sub- 
family polyphyletic. Even more fundamental 
is the finding that the clade ((Aneuretinae + 



AMERICAN MUSEUM NOVITATES 



NO. 3208 



Dolichoderinae) + Formicinae) is now the 
sister group to the Ponerinae s.l. + (Adeto- 
myrma + army ants), and not to (Myrmeci- 
inae, Nothomyrmeciinae, Pseudomyrmeci- 
nae, Myrmicinae). Also, the basal node of 
Formicidae is now unresolved, whereas it 
was resolved in Baroni Urbani et al.'s (1992) 
trees. In the hand-derived cladogram by 
Ward (1994), the most significant difference 
is the switch of the Myrmicinae from being 
one of the most basal clades, to perhaps be- 
ing allied with a portion of the Ponerinae. 

The analyses presented here raise caution 
concerning the robustness of the proposed 
phylogeny of the ants, caused by the addition 
and deletion of taxa as well as the reinter- 
pretation of some of the character states, 
which have great effects on the topology of 
the trees. First, many missing values, es- 
pecially in three taxa (Aenictogiton, Priono- 
myrmex, and the fossil Formicium) create a 
highly ambiguous matrix with 16% of the 
cells missing. Second, many taxa have a high 
degree of polymorphism (6% of cells). These 
two factors result in an ambiguous matrix 
(more than 22% of the cells), which is ac- 
cordingly problematic (Nixon, 1996). The 
addition or deletion of taxa always resulted 
in different topologies, in our view another 
clear sign of insufficient data. 

As important as phylogenetic analyses of 
Formicidae are for evolutionary studies, the 
understanding of ant phylogeny still requires 
serious attention. The fine preservation of 
fossils in amber allows retention of many 
more characters than in compression fossils, 
which is made abundantly clear in how much 
less ambiguous is the placement of the New 
Jersey amber ants as compared to the Eocene 
compression fossil taxon. Placement of even 
the finest fossils, though, depends on a stable 
phylogeny, itself subject to the discovery of 
fossils with unpredicted combinations of 
characters. Ultimately, all robust phylogenies 
depend on the discovery of new characters 
and close scrutiny of the homologies of 
known characters. 

CONCLUSION: THE AGE OF ANTS 

The discovery of further sphecomyrmine 
ants in amber and the detailed structure of 
their metapleural gland clearly show that 



sphecomyrmines are ants. The reanalyses of 
earlier published data and the inclusion of 
fossil data (indeed, data on fossilized inclu- 
sions!), for which more than 35% of the 
characters could be coded, confirm the basal 
position of the sphecomyrmines. The discov- 
ery in particular of Brownimecia, a new and 
primitive Cretaceous ponerine, and the pres- 
ence of four taxa from the same deposit, in- 
dicate that the radiation of ants 90-94 Ma 
was more developed than previously be- 
lieved. Stratigraphic distribution of fossil 
Formicoidea is thus: the oldest known forms 
are from ca. 110 Ma, and the oldest definitive 
Formicidae are known from approximately 
20 Ma later; only primitive taxa occur 
throughout the first 50 Ma or pre-Tertia- 
ry history of fossil ants. 

A reasonable estimation would place the 
origin of the ants in the lowermost Creta- 
ceous, but almost certainly no earlier. This 
conclusion is also consistent with the close 
relationship of the Formicidae to the Vespi- 
dae + Scoliidae (Brothers and Carpenter, 
1993), and the phylogenetic position of Cre- 
taceous Vespidae (Carpenter and Rasnitsyn, 
1990). Vespid fossils belonging only to the 
two basalmost clades of the family occur in 
sediments from the Barremian (ca. 118 Ma) 
to Turonian of Russia. Vespids may extend 
to the earliest Cretaceous. Recently, Crozier 
et al. (1997) estimated a controversial age of 
the Formicidae as being in the lower Juras- 
sic. This hypothesis was based on estimated 
divergence times of mitochondrial cyto- 
chrome b sequences compared among extant 
species of Myrmecia, calibrating nucleotide 
substitution rates using Cariridris, and an as- 
sumption of clocklike rates. Previously we 
discussed the ambiguous nature of Cariri- 
dris, but Crozier et al. regard it as an "un- 
doubted ant" and a myrmeciine in particular. 
Our reanalyses have confirmed a basal phy- 
logenetic position of the myrmeciines, mak- 
ing the existence of a lower Cretaceous one 
like Cariridris plausible. While Cariridris, 
like other insects from the Crato Member of 
the Santana Formation, is assignable to the 
Aptian (Maisey, 1990), an absolute age of 
124.5 Ma (cited by Crozier et al., 1997) is 
too old: 110 Ma is the recognized age. Use 
of an ambiguous fossil to calibrate nucleotide 
change among extant species of Myrmecia 



GRIMALDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 



no doubt has led to an estimate of ant origins 
that is contrary to the whole fossil record of 
the Hymenoptera. Despite the vicissitudes of 
insect fossilization, given the consistent pres- 
ervation of Symphyta and basal Apocrita in 
the Jurassic, and the appearance of most liv- 
ing and extinct families of Aculeata in the 
lower to mid-Cretaceous (Rasnitsyn, 1988), 
a lower Jurassic origin of the ants is highly 
improbable. The earliest Hymenoptera, in 
fact, are xyelid sawflies from the Triassic, 
and the earliest aculeates are the extinct fam- 
ily Bethylonymidae from the upper Jurassic 
of Russia. 

With little doubt, ant origins do not pre- 



date 140 Ma, or the earliest Cretaceous. Lat- 
est Cretaceous and earliest Tertiary records 
of ants are paultry to nonexistent, but all ev- 
idence thus far indicates that by the early 
Tertiary there is consistent preservation of 
living subfamilies and even some extant gen- 
era (Dlussky, 1988, 1996; W. M. Wheeler, 
1915; Wilson, 1985). The radiations that 
spawned approximately 11,000 living spe- 
cies of ants occurred only 40-50 million 
years ago, or one-third to one-half the ap- 
proximate duration of ants. Why the ants did 
not become abundant, diverse, and dominant 
until the Tertiary is a matter for future con- 
sideration. 



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Poinar, G. O., Jr. 

1992. Life in amber. Palo Alto, CA: Stanford 
Univ. Press. 

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1988. An outline of the evolution of the hy- 
menopterous insects (Order Vespida). 
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1996. Burmese amber at the Natural History 
Museum [London]. Inclusion (Wrostek) 
[Krakow] 23: 18-22. 

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1 970. Insektenfuhrender Bernstein aus der Un- 

terkreide des Lebanon. N. Jahrb. Geol. 

Palaontol. Monatsh. 1970: 40-50. 
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1997. Techniques for screening and preparing 
inclusions in brittle ambers from the 
Cretaceous period. MS. Am. Mus. Nov- 
itates. 

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Urbani 

1996. Le mystere de la chambre jaune. Re- 
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1994. Adetomyrma, an enigmatic new ant ge- 
nus from Madagascar (Hymenoptera: 
Formicidae), and its implications for ant 
phylogeny. Syst. Entomol. 19: 159-175. 
Wheeler, W 

1992. Extinction, sampling, and molecular 
phylogenetics. In M. Novacek and Q. D. 
Wheeler (eds.), Extinction and phylog- 



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Univ. Press. 
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1915. The ants of the Baltic amber. Schr. Phys. 

-Okon Ges. Konigsberg 55: 1-142. 
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amber of North America. Psyche 92: 

205-216. 
1987. The earliest known ants: an analysis of 

the Cretaceous species and an inference 

concerning their social organization. Pa- 

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Wilson, E. O., E M. Carpenter, and W. L. Brown, 
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1967a. The first Mesozoic ants. Science 157: 

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1-19. 

APPENDIX 

Vacuum Embedding and Disintegration 
of the Type of Sphecomyrma freyi 

The holotype of Sphecomyrma freyi occurred 
in a deep red piece of amber collected in 1966 
from Cliffwood Beach, New Jersey. The piece 
originally contained two workers, but it cracked, 
separating the two workers (Wilson et al., 
1967a,b). The piece containing the holotype (pho- 
tograph in Holldobler and Wilson, 1990) was 
roughly cubical, approximately 22 X 18 X 17 
mm, very brittle, with some fine, superficial 
cracks; larger cracks permeated deeply into the 
piece. It was stored in a wooden cabinet in an 
uncovered drawer of the fossil insect collection in 
the Museum of Comparative Zoology for 30 
years, padded with cotton in a small plastic box 
with a snap clasp. Over the years there had been 
deterioration of the piece; it become darker and 
more fractured, which is typical of even softer, 
less brittle amber like Baltic material (Grimaldi, 
1993). Cretaceous material is even more suscep- 
tible to oxidative damage. To slow or prevent fur- 
ther deterioration, Canada Balsam had been ap- 
plied to one or more faces of the piece (F. M. 
Carpenter, personal commun. to DG, 1988), al- 
though when and how often is unknown. 

The ant itself was very close (ca. 0.3 mm) to a 
flat, prepared surface. This surface had numerous, 
fine, parallel scratches, the result of grinding/pol- 
ishing by Carpenter or others. On top of this sur- 
face was a layer of clear, hardened material with 
a slightly irregular surface, 0.1-0.2 mm thick, that 
prevented detailed observation of the holotype. A 
cotton swab moistened with 70% ethanol gently 
rubbed on the surface resulted in no visible effect. 



AMERICAN MUSEUM NOVITATES 



NO. 3208 



Balsam would become tacky under such treat- 
ment. The coating(s) applied just over the ant no 
doubt were made to reduce surface distortions for 
photography and close examinations. It later be- 
came apparent that this material was almost cer- 
tainly dried mineral oil, or perhaps a synthetic 
slide mounting medium like Euparol (or both), 
based on the manner in which this substance be- 
haved during curing in a synthetic embedding res- 
in, and some other observations. 

Mineral oil has traditionally been used for ex- 
tremely clear observation of inclusions in amber 
(e.g., Grimaldi, 1993). F. M. Carpenter used min- 
eral oil, in fact, to store some pieces of Baltic and 
Canadian amber in the MCZ, as a method to pre- 
vent oxidative decomposition, but he also embed- 
ded some pieces in Canada Balsam (Grimaldi, 
1993; also see comments below). Lastly, the cot- 
ton stored in the box with the type specimen was 
stained yellowish, similar to mineral oil residues 
on cotton from specimens in the AMNH collec- 
tion. If the layer was even partially dried mineral 
oil, numerous coatings must have been applied 
over the years, perhaps by various investigators 
inspecting the specimen. 

To prevent further deterioration of the MCZ 
specimen, a process of vacuum embedding in a 
synthetic resin was used, refined from that of 
Schlee and Dietrich (1970), who developed it for 
preserving and studying very brittle Lebanese am- 
ber. The technique not only seals the piece from 
atmospheric oxygen, it is an excellent physical 
protection from accidental shattering, and is the 
only reliable way to trim into a piece of cracked 
amber for accurate views of inclusions without 
further fracturing or splitting the piece. The tech- 
nique has been used successfully and consistently 
on over 800 pieces of New Jersey and Lebanese 
amber at the AMNH. A detailed, illustrated de- 
scription will be presented elsewhere (Silverstein, 
and Nascimbene, 1997), but with basic techniques 
mentioned here. 

The embedding medium is an epoxide (Buehler, 
Inc.) that is hardened using a polymerization/cat- 
alyzing agent. Heat is generated during the poly- 
merization; the larger the volume of medium, the 
hotter the reaction. Epoxide and catalyzing agent 
are mixed in a separate container, then poured into 
shallow cylindrical rubber molds (Buehler, Inc). 
The amber piece is then gently slipped beneath 
the surface of the liquid epoxy, bubbles removed 
from the epoxide, and the preparation placed un- 
der a bell jar that is sealed and brought to ap- 
proximately 4 psi of pressure (atmospheric pres- 
sure at sea level being 14 psi). The reduced pres- 
sure removes air from fine cracks in the amber, 
allowing epoxide to seep into the cracks and bind 
fractures together (it also improves visibility, by 



eliminating mirrorlike fractures filled with air). 
After 10 minutes under vacuum, the rubber cups 
are removed and the specimen is allowed to hard- 
ened at room temperature and pressure, generally 
taking several hours. The hardened block can then 
be trimmed with a water-fed diamond saw and 
ground with water-fed emory wheels of 320 and 
600 grits. 

Shortly after the MCZ piece was removed from 
the vacuum, a foam of bubbles suddenly appeared 
on the coated surface over the ant, signaling a 
reaction within the epoxide no doubt initiated by 
the heat of polymerization. Within several min- 
utes the epoxide had become thickened enough to 
prevent removing the amber without damage. Nu- 
merous previous embeddings done in this manner, 
using pieces of New Jersey amber and epoxide 
volume several times this size, never yielded vis- 
ible effects to the amber, let alone a froth of bub- 
bles. The heat alone from the polymerization re- 
action would not cause such an effect on the am- 
ber (amber, in fact, requires temperatures in ex- 
cess of 350F for any softening to occur). The 
coating over the ant had caused the intense bub- 
bling, since uncoated surfaces were largely unaf- 
fected. To our deep disappointment, we found that 
the coating had penetrated several millimeters into 
the amber. 

After the epoxy was completely hardened, it 
was trimmed and polished. No view of the ant 
could be found, the surface where it now was be- 
ing opaque with a suspension of yellowish bub- 
bles. The block was cut through the middle of the 
amber piece, distant from the ant, in an attempt 
to view the ant from the other, interior side. (In 
cutting through the center, other, minute insects 
may have been obliterated, which we considered 
worth sacrificing for the sake of the ant. One un- 
usual psychodid midge deep in the piece, though, 
was revealed this way and remains very well pre- 
served and displayed, a silent and enduring wit- 
ness). Cutting through the interior of the amber 
exposed highly fractured and brittle amber too 
deep for the epoxide to have permeated, even un- 
der vacuum. Both halves were vacuum embedded 
again, with perfect results (the coated surface of 
the amber was already sealed). Since the exposed 
inner surface of the amber was cemented by the 
second embedding, grinding of the interior sur- 
face toward the outer surface with the ant could 
now be done safely. Reaching 2 mm within the 
presumed surface of the ant revealed no specimen. 
It was only after a cross section was ground away 
from one edge that it became apparent that the 
bubbling involved the 12 mm of surface amber 
containing the ant. During the bubbling of the 
coating + amber mixture, the ant had become dis- 



GRIMALDI ET AL.: PRIMITIVE ANTS IN CRETACEOUS AMBER 



coating 

coating 

+ 
amber 



amber 



epoxide 



Fig. 24. Schematic interpretation in cross sec- 
tion of damaged incurred to the amber piece con- 
taining the type of Sphecomyrma freyi during em- 
bedding process. Top, prior to embedding. Mid- 
dle, formation of reaction bubbles. Bottom, end 
result. Uncoated surfaces were largely unaffected. 



articulated and the parts entirely obscured, with 
the specimen effectively disintegrated. 

What was so stunning was the dramatic and 
destructive effect of the coating on the amber it- 
self, a substance popularly considered inert. The 
effect must have been greatly enhanced by oil that 
penetrated numerous fine fractures in the piece, 
and by presumably 30 years of contact with and 
replenishment of oil. If any of these microscopic 
and oil-laden fractures extended to the ant, its 
body cavity would probably have contained the 
coating too. Oddly, Baltic amber stored for de- 
cades in vials of mineral oil at the MCZ showed 
little surface degradation (D. Grimaldi, personal 
obs., 1995). A small collection of Arkansas am- 
ber, however, given to the AMNH and stored for 
20 years in mineral oil at the Univ. Illinois by 
Ellis MacLeod, was soft and malleable even to 
the core of pieces 20 mm thick, and totally de- 
graded. Mineral oil obviously has dramatically 
different effects on different ambers. Even though 
Baltic and Arkansas ambers are similar in age, 
they have completely different botanical origin 
and chemistry, which must account for the differ- 
ent reactivity. New Jersey amber is no different. 
The fact that this amber visibly reacts with organ- 
ic solvents like acetone, whereas most other am- 
bers (including Cretaceous amber from Lebanon 
and Canada) do not, indicates a particularly frag- 
ile and reactive composition. 

This preparation is a tragic lesson in the study 
and stewardship of valuable amber fossils. First, 
the use of mineral oil almost certainly the coat- 
ing that caused the disintegration must be strin- 
gently avoided. Despite advocacy of the use of 
mineral oil for viewing inclusions (e.g., Grimaldi, 
1993; Poinar, 1992), this oil clearly chemically 
reacts with some ambers much more than others. 
Sugar syrup or glycerine, or other water-based 
substance, should be used. Hopefully it is not too 
late for some specimens. Many pieces of amber 
in the Acra collection of Lebanese amber, and 
even some of the New Jersey amber ants reported 
in this study, had been coated with mineral oil at 
various times for better viewing of inclusions. 
Thin films of the oil must still reside on the sur- 
face and in the fine cracks. 

Secondly, failures like this must temper future 
curatorial decisions. Given a particularly valuable 
amber fossil that will gradually disintegrate with 
age, but which has been treated in unknown ways, 
keen insight must be excercised as to the appro- 
priate method of conservation. 

David Grimaldi, Curator, AMNH 
Paul Nascimbene, Curatorial Assistant