Fossiliferous Cretaceous Amber from Myanmar

72 Pages·2002·6.34 MB·English

PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY
CENTRAL PARK WEST AT 79TH STREET, NEW YORK, NY 10024
Number 3361, 71 pp., 44 figures, 2 tables March 26, 2002
Fossiliferous Cretaceous Amber from Myanmar
(Burma): Its Rediscovery, Biotic Diversity, and
Paleontological Significance
DAVID A. GRIMALDI,1 MICHAEL S. ENGEL,2 AND PAUL C. NASCIMBENE3
CONTENTS
Abstract ....................................................................... 3
Introduction .................................................................... 3
Materials and Methods .......................................................... 6
Results ........................................................................ 8
Taphonomic Observations ..................................................... 8
Taxonomic Diversity .......................................................... 8
Plantae .................................................................... 9
Animalia ................................................................. 22
Nematoda .............................................................. 22
Mollusca ............................................................... 24
Onychophora ........................................................... 24
Arthropoda ............................................................. 27
Chelicerata ........................................................... 27
Insecta ............................................................... 31
Orthoptera ......................................................... 31
Zoraptera .......................................................... 31
Embiidina .......................................................... 31
1Curator,Divisionof Invertebrates,AmericanMuseumofNaturalHistory.e-mail:[email protected]
2Research Associate, Division of Invertebrates, American Museum of Natural History; Assistant Professor, De-
partment of Ecology and Evolutionary Biology and Curator, Division of Entomology, Natural HistoryMuseumand
Biodiversity Research Center, Snow Hall, 1460 Jayhawk Boulevard, University of Kansas, Lawrence, KS 66045-
7523.
3CuratorialSpecialist,DivisionofInvertebrates,AmericanMuseumofNaturalHistory.e-mail:[email protected]
Copyright(cid:113)AmericanMuseumofNaturalHistory2002 ISSN0003-0082
2 AMERICAN MUSEUM NOVITATES NO. 3361
Plecoptera .......................................................... 33
Dermaptera ......................................................... 34
Isoptera ............................................................ 35
Hemiptera .......................................................... 35
Neuropterida ....................................................... 42
Coleoptera ......................................................... 45
Hymenoptera ....................................................... 48
Diptera ............................................................ 52
Conclusions ................................................................... 58
Biostratigraphic Chronology .................................................. 58
Taxonomic Diversity ......................................................... 61
Paleoenvironment ............................................................ 63
Acknowledgments ............................................................. 64
References .................................................................... 65
2002 GRIMALDI ET AL.: BURMESE AMBER 3
ABSTRACT
Amber from Kachin, northern Burma, has been used in China for at least a millenniumfor
carvingdecorativeobjects,buttheonlyscientificcollectionofinclusionfossils,attheNatural
HistoryMuseum,London(NHML),wasmadeapproximately90yearsago.Ageofthematerial
wasambiguous,butprobablyCretaceous.Numerousnewrecordsandtaxaoccurinthisamber,
based on newly excavated material in the American Museum of Natural History (AMNH)
containing 3100 organisms. Without having all groups studied, significant new records and
taxa thus far include the following (a † refers to extinct taxa): For Plants: An angiosperm
flower (only the third in Cretaceous amber), spores and apparent sporangia of an unusual but
common fungus, hepatophyte thalli and an archegoniophore of Marchantiaceae, and leafy
shoots of Metasequoia (Coniferae). Metasequoia is possibly the source of the amber. For
Animals:MermithidaeandotherNematoda;theoldestixodidtick(alarvalAmblyomma);bird
feathers; and the only Mesozoic record of the Onychophora (‘‘velvet’’ worms), described as
†Cretoperipatus burmiticus, n. gen., n. sp. (Peripatidae). Poinar’s classification of the Ony-
chophoraissubstantiallyrevised.Stilllargelyunstudied,thefaunaofmites(Acari)andspiders
(Araneae) appears to be the most diverse ones known for the Mesozoic. For Insecta:Odonata
indet.(wingfragment);Plecopteraindet.;newgeneraofDermaptera,Embiidina,andZoraptera
(thelattertwoastheonlydefinitiveMesozoicfossilsoftheirorders).WithinHemiptera,there
are primitive new genera in the Aradidae, Hydrometridae, Piesmatidae, Schizopteridae, and
Cimicomorpha (Heteroptera), as well as in †Tajmyraphididae (Aphidoidea), and †Protopsyl-
lidiidae. An adult snakefly (Raphidioptera: †Mesoraphidiidae) is the smallest species in the
order, and new genera occur in the Neuroptera: Coniopterygidae, Berothidae, and Psychopsi-
dae, as well as larvae of apparent Nevrorthidae. Coleoptera are largely unstudied, but are
probably the most diverse assemblage known from the Cretaceous, particularlyforStaphylin-
idae. An adult lymexylid, the most primitive species of Atractocerus, is the first Mesozoic
record of the family. In Hymenoptera there are primitive ants (Formicidae:Ponerinaen.gen.,
and †Sphecomyrma n.sp [Sphecomyrminae]), the oldest record of the Pompilidae, and signif-
icant new records of †Serphitidae and †Stigmaphronidae, among others. Diptera are the most
diverse and abundant, with the oldest definitive Blephariceridae and mosquito (Culicidae), as
well as new genera in the Acroceridae, Bibionidae, Empidoidea; a new genus near the enig-
matic genus Valeseguya, and an unusual new genus in the †Archizelmiridae. †Chimeromyia
(Diptera: Eremoneura), known previously in ambers from the Lower Cretaceous, is also rep-
resented.
The stratigraphic distribution of exclusively Mesozoic arthropods in Burmese amber is re-
viewed, which indicates a probable Turonian-Cenomanian age of this material (90–100 Ma).
Paleofaunal differences between the NHML and AMNH collections are discussed, as is the
distincttropicalnatureoftheoriginalbiota.Burmeseamberprobablyharborsthemostdiverse
biota in amber from the Cretaceous, and one of the most diverse Mesozoic microbiotas now
known.
INTRODUCTION and jade. Use of it as a precious and semi-
precious substance abruptly ended, though,
Of all the world’s amber deposits, perhaps
byapproximately1940,anddespitethework
none has more mystique than those from of an insightful entomologist made 80 years
northern regions of Myanmar. ‘‘Burmite,’’ ago, its scientific significance has been con-
along with jadeite from nearby mines, was fused and only recently recognized.
exported to China since at least the first cen- The first significant geological investi-
turyA.D.foruseinjewelryandcarvedobjets gation of Burma’s amber was by Noetling
d’art (Laufer, 1906; reviewed in Grimaldi, (1892, 1893), who reported the most pro-
1996; Zherikhin and Ross, 2000). Balticam- ductive sites in the Hukawng Valley of the
ber had been prized for 10 millennia before northern stateofKachin,specificallysouth-
thisinnorthernEurope,butinAsiatheprox- west of Maingkhwan (26(cid:56)20(cid:57)N, 96(cid:56)36(cid:57)E).
imity of Burmese amber, and probably its Four other regions in Burma have histori-
deep red color, hardness, and glassy polish, cally yielded amber (reviewed in Zherikhin
made it particularly sought along with ivory and Ross, 2000), but none as prolific and
4 AMERICAN MUSEUM NOVITATES NO. 3361
commercially exploited as in the Hukawng among the plethora of taxa with which he
Valley. Noetling mentioned inclusions of worked.Asaresult,hewasabletorecognize
insects and plants, and perceptivelynoticed that the arthropods in Burmese amber (and
that the newly excavated amber pieces ap- therefore the amber itself) were older than
peared weathered and may havebeentrans- the surrounding sediments, perhaps even
ported some distance before redeposition. Cretaceous in age:
H.L. Chhibber visited the Hukawng Valley They[thearthropodsinBurmeseamber]are,indeed,
in 1930, and made many additional obser- related to living forms; but in practically every case
vations. He reported the amber to occur in topreciselythoseformswhichwehavethoughtofas
ancient,asremnantsofaveryoldfauna.So... itis
thin lignite seams among clays and shales
difficult to avoid a strong suspicion that the amber,
(Chhibber, 1934). The larger, transparent
thoughfoundinMioceneclay,isactuallyverymuch
pieces of amber were buried between 10– older, conceivably even Upper Cretaceous. (Cocker-
15 m, and to reach it miners excavated nar- ell,1917a:360).
row shafts with walls supported bybamboo
Until approximately the 1960s, the Creta-
screens. Beyond this depth, ground water
ceous was one of the poorest known geolog-
would fill the shaft. Presence of the fora-
ical periods for insects; now there are over
miniferan Nummulitesbiarritzensisindicat-
30 major Cretaceous deposits yielding in-
ed a middle Eocene age of the sediments,
sects (see, for example, the summary in Ev-
though Chhibber acknowledged that the
enhuis, 1994). Despite this deficiency, and
amber was possibly reworked from older
Cockerell’s early suggestion that Burmese
sediments. He also reported that amberwas
amber was Cretaceous, there was very little
mined most abundantly near the villages of
research on the NHML collection between
Khanjamaw (26(cid:56)15(cid:57)50(cid:48)N, 96(cid:56)33(cid:57)37(cid:48)E),
1921 and 1995, nor were there any recorded
Ladummaw (26(cid:56)11(cid:57)19(cid:48)N, 96(cid:56)28(cid:57)48(cid:48)E), and attempts to excavate additionalBurmeseam-
Lajamaw (26(cid:56)15(cid:57)N, 96(cid:56)28(cid:57)E). His obser- ber for study of the inclusions. In 1995, Al-
vation thatsomeareasreportedbyNoetling exandr Rasnitsyn, of the Paleotological In-
were pocked with abandoned mines may stitute, Moscow, and Genady Dlussky, of
have led to the popular notion that the min- Moscow State University, studiedHymenop-
ing of Burmese amber, by and large, was tera and specifically ants, respectively,in the
depleted or abandoned (e.g., Fraquet, NHML collection of Burmese amber. Ras-
1987). nitsyn (1996b) noted the presence of the ex-
AccordingtotherecordsoftheGeological tinct Cretaceous family †Serphitidae and the
Survey of India, 82,000 kg of Burmese am- subfamily †Iscopininae (Hymenoptera).
ber were excavated between 1898–1940 Dlussky (1996) described a bizarre ant,
(summarized by Zherikhin and Ross, 2000). †Haidomyrmex, from the NHML collection,
Curiously, only one collection of Burmese which he placed in the Cretaceoussubfamily
amber is known that was made for scientific †Sphecomyrminae. Mounting evidence that
purposes. This collection consists of 117 Burmese amber was Cretaceous led to a co-
piecescontainingapproximately1200organ- ordinated study of the NHML collection, or-
isms in the NHML. It was assembled by ganized by Andrew Ross (NHML). Produc-
R.C.J. Swinhoe of Mandalay between 1915 tive as Cockerell was, he touched on but a
and 1916, and sent to a prolific entomologist fraction of the organisms in the NHML col-
in Colorado, T.D.A. Cockerell (1866–1948). lection of Burmese amber. In a recent issue
Cockerell is renowned for having written (vol. 56, no. 1) of the Bulletin of the Natural
nearly 4000 articleson varioussubjects(We- History Museum (Geology Series) [London],
ber, 1965), butparticularlythesystematicsof eight papers describe 15 new species of ar-
living and fossil insects. Between 1916 and thropods in six orders from that collection.
1921, Cockerell published 13 papers on 41 Therein are also extremely usefulsummaries
new arthropods in Swinhoe’s collection,then ofdescribedspeciesinBurmeseamber(Ross
donated the collection to the NHML. Cock- and York, 2000), and a listofarthropodfam-
erell described perhaps 7000–8000 species ilies (Rasnitsyn and Ross, 2000).
during his lifetime, but also had an uncanny AddingtotherenewedinterestinBurmese
ability to recognize natural relationships amber, we are able to reporta newcollection
2002 GRIMALDI ET AL.: BURMESE AMBER 5
TABLE1
Summary of Major Fossiliferous Cretaceous Amber Deposits
of fossils in amber assembled from material the Cretaceous. Disparity in the results is
that was recently excavated from the Hu- probably due to approaches that use taxic
kawng Valley in northern Burma—the only analyses (e.g., numbers of insect families)
new scientific specimens of the material ob- versus phylogenetic analyses (see Grimaldi,
tained in over 80 years. The collection con- 2000a). Compared to dramatic extinctionsof
tains nearly three times the number of inclu- non-avian dinosaurs, ammonites, rudist bi-
sions as the NHML collection, and many valves, and other taxa by the K/T boundary,
new taxa and records not represented in the extinctions of insects are barely noticeable,
NHML collection. Moreover, our findings and may be obscured by the impressive ra-
not only corroborate a Cretaceous age of diations of insects just prior to this time.
Burmese amber, but also suggest an origin Besides preserving a rich fauna from a bi-
that is probably mid-Cretaceous. ologically important time period, Burmese
The Cretaceous is one of the most bioti- amber preserves organisms with a lifelikefi-
cally significant periods in the evolution of delity for which amber is renowned (Gri-
terrestrial life since the angiosperms explo- maldi, 1996). Such complete preservation
sivelyradiatedintheupperpartoftheLower vastly improves interpretation of extinctspe-
Cretaceous (Crane et al., 1995). Given the cies.
greatdiversityofextantinsectsintimatelyas- Lastly,thelocationofBurmeseamberalso
sociated with angiosperms, evolution of the makes it highly significant. It is theonlyma-
two groups would presumably be inextrica- jor,fossiliferousdepositofCretaceousamber
bly linked. One study found, however, that in southeastern Asia, and one of two of the
therewasnoincreaseinthenumberofinsect most southerly deposits of fossiliferous Cre-
families in the Cretaceous during or imme- taceous amber. All other major deposits of
diately following the angiosperm radiations Cretaceousamberoccurbetween34(cid:56)and74(cid:56)
(Labandeira and Sepkoski, 1993), but in fact N latitude (Table 1), but why they are re-
there was a slight slump in family numbers. stricted to the Northern Hemisphere is an
Other taxic analyses found a profound radi- enigma. Paleolatitude of the Burmese and
ation of Cretaceous insects (Jarzembowski Lebanese amber deposits (10–15(cid:56)N) are the
and Ross, 1993, 1996; Ross et al., 2000). most southerly of all major Cretaceous am-
Phylogenetic studies on speciose families of ber deposits. As discussed at the end of this
insect pollinators (Engel, 2001; Grimaldi, paper, climatic effects from paleolatitude
1999), herbivores (Farrell, 1998), and major were probably profound. Ages, locations,
consumers (Grimaldi and Agosti, 2000; Gri- and references for the major deposits of fos-
maldi et al., 1997; Thorne et al., 2000) in- siliferous Cretaceous amber are the follow-
dicatedexplosiveradiationofthesegroupsin ing:
6 AMERICAN MUSEUM NOVITATES NO. 3361
LOWER CRETACEOUS: LEBANON and Chhibber (1934). Apparently, miners needto
JORDAN, ranging from the Lower to Upper reach lignitic seams some 30–40 cm thickto
Neocomian (Berriasian to Aptian, and a mi- obtain the amber, which can occur at depths
nor incursion into the Albian; Azar, 2000); ofupto12m.In2000,nearly80kgofcrude
SPAIN (Nograro Formation of Alava, upper amber was mined. Samples of various colors
Aptian and middle Albian; Alonso et al., were analyzed using Pyrolysis-Gas chroma-
2000); and RUSSIA, Taimyr Peninsula of tography (PyGC) and PyGC-Mass Spectros-
northern Siberia (Ogneva Formation, Aptian copy (e.g., Shedrinsky et al., 1991; Grimaldi
to Albian; Zherikhin and Eskov, 1999). Sev- et al., 2000a), which matched identically to
eral smaller deposits in Japan and England each other and to samples from the NHML
have also yielded insect fossils (summarized collection (A. Shedrinsky, unpubl. data on
by Grimaldi, 1996; Ross, 1998). file in the Invertebrates Division, AMNH).
UPPER CRETACEOUS: CANADA (western), Material from the outcrops of the 1999 and
CedarLake,ManitobaandMedicineHat,Al- 2000 excavations may be different from that
berta (McAlpine and Martin, 1969), and reported by Chhibber (1934) and earlier
Grassy Lake, Alberta (Pike, 1995). The workers, but their proximity and chemical
Grassy Lake and Medicine Hat deposits be- identity indicates an identical botanical ori-
longtotheForemostFormation,JudithRiver gin with the historical collections and, thus,
Group (Campanian, possibly Santonian). probably a very similar or identical age.
RUSSIA: Taimyr Peninsula, Siberia, from Approximately 75 kg of raw Burmeseam-
Agapa and belonging to the Dolgan Forma- ber were shipped to the AMNH by Leeward
tion (Cenomanian), and from Yantardakh, Capital, where it was treated in lots of ap-
Kheta Formation (Santonian). Zherikhin and proximately 3 kg, using a 50% solution of
Eskov (1999) also reviewed other localities muriatic acid (HCl) to dissolve veins of cal-
in the former USSR. USA: NewJersey(Rar- cite that permeated most pieces. This greatly
itan Formation, Turonian; Grimaldi et al., improved visibility into the amber. The am-
1989; 2000a). The paleobiota of New Jersey ber was then washed thoroughly with water,
amber is the most diverse one reported thus and carefully screened for organismal inclu-
far,eventhoughthedepositthatyieldedmost sions piece by piece. The amber was kept
of the amber was extremely localized. Very wetduringscreeninginordertoimprovevis-
likelytheBurmeseamberbiotawillbefound ibility. Screening was done under a stereo-
tobemorediversethananyotherCretaceous scope(approximately20(cid:51)magnification)us-
amber deposit, including amber from New ing transmitted and oblique reflected light.
Jersey. For many pieces, one or more surfacesneed-
edtohavea‘‘window’’polishedintothesur-
MATERIALS AND METHODS ficial rind in order to locate and view inclu-
sions.ThiswasdoneusingaBuehlerEcomet
Bags of crude amber were purchased by water-fed flat lap with abrasive discs (320,
Leeward Capital Corporation, a Calgary- 600, 800, 1200 grits). Because Burmese am-
based mining company, from local sources ber is exceptionally hard compared to other
near the village of Tanai. Tanai is on the ambers, it was generally possible to trim off
Ledo Road in Kachin State, close to the his- some amber surrounding an inclusion with-
torical sources of Burmese amber in the Hu- out the piece splitting or crumbling. Hard-
kawngValley(fig.1).Miningspecificallyoc- ness of Burmese amber allowssurfacestobe
cursapproximately32kmsouthwestofTanai polished with a glassy finish. Trimming was
near Noije Bum (‘‘hill’’, approx. 250 m). done with a fine (1.5 mm thick) diamond,
Since initial exploration in 1999, Leeward water-fed, circular trim saw; the sawed sur-
has joined with a local Kachin mining com- faces were ground with successively finer
pany (Buga Company Ltd.) for exploitation grits, and then polished with a 1(cid:109)m alumina
of the amber deposits, under the jurisdiction polish. This optimized the penultimate step
of the Myanmar Ministry of Mines and mil- in preparation: embedding the piece in a
itary officials. Methods of mining the amber highlystableepoxy(Buehler)undervacuum,
remain traditional, just as were described by asdescribedindetailelsewhere(Nascimbene
2002 GRIMALDI ET AL.: BURMESE AMBER 7
Fig. 1. Location of Burmese amber deposits. Above: inset shows approximate area in southeast
Asia. Below: detail within inset.
8 AMERICAN MUSEUM NOVITATES NO. 3361
and Silverstein, 2000). Inthisprocess,epoxy amber varied in color from light, transparent
penetrates most fine cracks and thus helps yellowtodeep,bloodred,butthemostabun-
prevent fracturing during the final trimming, dant kind was an orange-colored amber con-
grinding, and polishing. Optimal prepara- taining swirls of fine bubbles and different
tions resulted in a cubic shape, with gener- hues. Pyrolysis gas chromatography–mass
ally no more than a millimeter or two be- spectroscopy on thedifferentformsofamber
tweentheinclusionandoneormoresurfaces indicate a chemically identical substance (T.
of the amber, these surfaces being generally Wampler and A. Shedrinsky, unpubl. data),
parallel to the plane of critical structures. so all of the amber was probably formed by
However, many pieces had multiple inclu- a single species of tree. Botanical identity of
sions that could not be separated, and this the tree that produced Burmese amber is un-
compromises preparation and observation. known,butpresenceofdiagnosticconiferous
This appears to be a particular problem with compounds indicates it certainly was a co-
the pieces from the NHML collection, since nifer, and possibly a cupressaceous tree like
most inclusions occur in large pieces that Metasequoia (see below). Variations may be
were sliced into polished slabs for viewing, a result of amount of predepositional expo-
but no further. sure and of geothermal energy during depo-
All AMNH pieces were given unique, se- sition (for color), and whether the resin was
quential numbers; for pieces with multiple secreted subcortically or externally (for
inclusions each inclusion was lettered (a, b, form). Insects were comparativelyrareinthe
c,...). Identifications weredone,wherepos- ‘‘swirly’’ amber, and when presenttheywere
sible,toatleastfamilylevel,andacollection often distorted from moderate to extreme
of 1200 pieces and 3100 inclusions was cat- compression, and often also disarticulated.
alogued using the database MS Access. This type of amber preservation is similar to
Printed or diskette copies of the databaseare thatinPaleoceneamberfromWyoming(Gri-
available from the senior author forqualified maldi et al, 2000b) and putatively Paleocene
researchers; an electronic version will even- amber from Sakhalin Island (Zherikhin and
tually be available at www.amnh.org. For Eskov, 1999). For Wyoming amber, it is be-
taphonomic purposes we included counts of lieved that extremely deep sedimentscreated
308 arthropod specimens too partial or de- tremendous pressures, which compressed
graded to be of systematic use, and so they most organisms and even organic debris
were not accessioned, cataloged, or databa- within the amber into unrecognizable
sed. Some were identifiable to insect family, ‘‘smears.’’ Another type of Burmese amber
or just as ‘‘Insecta incertae sedis’’ or ‘‘Ar- consisted of flattened, lens-shaped pieces,
thropodaincertaesedis’’.Systematicdescrip- which rarely contained insects. Insects were
tion and discussion of various taxa will be most commonly found in pieces shaped like
made in separate papers. flows or runnels; these compromised no
more than 3–4% by mass of all the amber
RESULTS butyieldedapproximately85%ofthearthro-
pods. Insects in runnel pieces were usually
TAPHONOMIC OBSERVATIONS
well preserved, and sometimes numerous or-
Some72.21kgofacid-washedamber(mi- ganisms were found in such a piece merely
nus the dissolved calcite) yielded, on aver- 3 cm long and 1 cm diameter. Clearly, the
age, 46 organismal inclusions per kg (a total runnel pieces were flows of resin secreted in
of3,408organisms).Thiscountincludes308 areas or under conditions optimal to entrap-
partial specimens, such as isolated wings of ment of insects.
insects, as well as specimens too poorly pre-
served for identification beyond order or to
TAXONOMIC DIVERSITY
family. Other inclusions (not included in this
figure) were plant stellate trichomes (more The recent collections haveyieldedsignif-
abundant than in any other Cretaceous am- icantnew,higher-leveltaxonomicrecordsfor
bersstudiedthusfar),barkfibers,woodfrag- Burmese amber, including several plants,the
ments, and insect frass. Individual pieces of phylaNematodaandOnychophora,andnear-
2002 GRIMALDI ET AL.: BURMESE AMBER 9
ly 30 families of Arthropoda (table 2). Col- the portion of the polyp preservedintheam-
lectively based on the NHML and AMNH ber almost always has a cross section of the
collections, the Burmese amber fauna pre- base exposed at the surface. This exposure
serves a remarkable diversity of organisms, allowed decay of the internal tissues in most
including numerous records of earliest oc- specimens; occasionally specimens were
currence and other significance. We briefly found with intact internal contents.
review below those taxa for which at least The sporangia in Burmese amber have no
some family-level identifications were done, apical ostiole, as is found in some antheridia
and ones we considered especially signifi- of hepatophytes having roughly similar
cant. We have not discussed the following shape (e.g., Sphaerocarpaceae). Cuticles
taxa represented in the new AMNH collec- were better viewed using scanning electron
tion, simply because they still require study: microscopy (SEM). This was done by taking
Aves(feathers,currentlyunderstudybyCar- threepieceswithsporangiaandcuttingafine
la Dove, Smithsonian Institution), Reptilia groove in each amber piece along various
(skin), Myriapoda, Collembola, Archaeog- axes close to the sporangium, then splitting
natha and Thysanura, Ephemeroptera,Odon- them open. This caused fracturing between
ata (wing fragments only), Blattodea and the cuticle and the amber (fig. 6), or through
Mantodea, Auchenorrhyncha, Pscoptera, the sporangium (fig. 7), depending on how
Thysanoptera, Trichoptera and Lepidoptera. the groove was cut. The exposed sporangia
were then gold coated for examination using
Kingdom PLANTAE a Zeiss DSM-1 SEM. The external surfaces
(cuticle) of the sporangia have a very fine
Plant Antheridia or Fungal Sporangia? geometricsculpturing,similartoherringbone
The most common organismal inclusion in patterns (fig. 6). Under stereoscope magnifi-
the material we screened were polyp-shaped cations (50–100(cid:51)), this pattern resembles
structures, ranging in size from 2 to 6 mm in fingerprints. Under the SEM at magnifica-
width,which arealmostcertainlythesporan- tions of 100–1000(cid:51), no cellular/epithelial
gia of a fungus or possibly plant (figs. 2–7). structurewasvisible,althoughinsomeviews
Similar structures occur in the NHML col- minute openings, 3–4 (cid:109)m in diameter, were
lection (A.J. Ross, personal commun.). They found in fairly regular distribution (fig. 6b),
were never branched or joined at the base, though nothing resembled stomata.
nor were vegetative/leafy structures found The interior of well-preserved sporangia
associated with them. One type of abundant was whitish and somewhat granular under
spore (figs. 8, 9) in this amber must be pro- stereoscopic magnifications; under the SEM
duced by these sporangia. at magnifications of 1,000–3,000(cid:51) some bi-
The sporangia grew on and through the ological structure was apparent. Significant
wood of the tree that produced the amber. looking structures were short, fibrous bun-
Several pieces of amber contained sporangia dles (figs. 7b, f) and small, compressed, ir-
and thin, delaminated layers of wood con- regular ‘‘flakes’’ approximately 5 (cid:109)m in di-
taining circular holes the same diameter as ameter (figs. 7a, c–e). Serial sections for
the base of nearby sporangia (fig. 3c). Doz- transmission electron microscopy (TEM)
ens, and up to approximately 100 sporangia, would probably be useful, although if a hy-
can be found in a piece of amber (fig. 2c). menium were present even at these SEM
Many pieces contained groups of sporangia magnifications columns of paraphyses and
arranged radially, with the bulbous ends to- asci would be apparent, as is found in the
ward the center (fig. 2c). This suggests that apothecia of certain ascomycetes like Pyro-
the sporangia were growing in narrow chan- nema.
nels into which resin flowed, either in deep Sporangia were always found either com-
grooves in the bark, or within decayedpock- pletely intact, or dehisced into empty, hemi-
ets near the surface of wood (fig. 4). Bases spherical halves (longitudinally; figs. 2, 5).
of sporangia were very rarely preserved, ap- Spores were never found within or oozing
parently having decayed when buried with out of dehisced sporangia, though clumps of
thewoodonwhichtheyweregrowing.Thus, a very distinctive and uniform type of spore
10 AMERICAN MUSEUM NOVITATES NO. 3361
TABLE2
Numbers of Specimensof Organismal Inclusionsin Burmese Amber in the Two Major Collections