Botanical Journal of the Linnean Society, 2002, 139, 361–367. With 13 figures
Fossil palm flowers in Dominican and Baltic amber
GEORGE POINAR JR.*
Department of Entomology, Oregon State University, Corvallis, OR 97331, USA
Received October 2001; accepted for publication March 2002
Five palm flowers in Dominican amber and one in Baltic amber are described or characterized. Palaeoraphe
dominicana gen. et sp. nov. in the subtribe Livistoninae, is described from one perfect flower in Dominican amber.
Roystonea palaea sp. nov. is described from one staminate and one pistillate flower in Dominican amber. Three
other palm flowers, two perfect flowers from Dominican amber and one staminate flower from Baltic amber, are
briefly characterized and figured. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society,
2002, 139, 361–367.
ADDITIONAL KEYWORDS: distribution – Palmae – Tertiary flowers.
INTRODUCTION
Documentation of palms (Palmae) in the fossil record
is mainly based on the presence of foliage, stems, fruits
and/or pollen in sedimentary strata which provides
evidence of this family from the early Cretaceous
(Daghlian, 1981; Stewart, 1983; Taylor & Taylor, 1993).
Fossil palm flowers are rare and those in amber show
excellent preservation (Caspary, 1880; Conwentz,
1886; Poinar, 2002). The present study describes and
characterizes newly acquired fossil palm flowers, five
from Dominican amber and one from Baltic amber.
These fossils, together with others reported previously
(Poinar, 2002), provide evidence of palm diversity in
the Greater Antilles in the mid-Tertiary and support
earlier evidence of extended northern ranges of the
Palmae in northern Europe in the Eocene.
MATERIAL AND METHODS
Of the five specimens in Dominican amber, one (accession number Sd–9–158) contains a perfect flower
belonging to the subtribe Livistoninae Saakov. This
specimen was reshaped to a triangular piece measuring 20 ¥ 16 ¥ 17 mm along the sides and 8 mm greatest depth with a weight of 1.2 g. Another piece of
Dominican amber (Sd–9–101) contained a staminate
*E-mail: [email protected]
and pistillate flower of a Roystonea species. This piece
was roughly trapezoidal in outline, measuring 40 ¥
40 ¥ 40 ¥ 35 mm, with a greatest depth of 7 mm
and weight of 14.5 g. Specimen Sd–9–102, also from
Dominican amber, contained two perfect flowers which
appear to be palm but could not be assigned to any
extant group. This piece was roughly oval in outline
with a greatest length of 45 mm, greatest width of
35 mm, greatest depth of 6 mm and weight of 6 g. A
Baltic amber piece (Sd–9–104) containing a single
staminate flower was roughly rectangular in outline,
measuring 21 mm in greatest length, 11 mm in greatest width and 0.9 g in weight. All specimens discussed
here are in the Poinar amber collection maintained at
Oregon State University, Corvallis, OR 97331.
The Dominican amber specimens originated from
La Toca mine in the northern mountain ranges of
the country. Dominican amber has been dated using
several methods, with estimates ranging from 15–
20 Myr on the basis of foraminifera (Iturralde-Vincent
& MacPhee, 1996) to 30–45 Myr on the basis of coccoliths (Cêpek in Schlee, 1990). The Baltic amber piece
originated from the Kaliningrad mines and has been
dated at 40 Myr based on stratigraphy (Larsson, 1978;
Poinar, 1992). All drawings were made with a camera
lucida tube mounted on a Nikon UFX-2 steromicroscope. Terminology and generic analysis of extant
palms were based on the works of Uhl & Dransfield
(1987) and Zona (1996).
© 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 361–367
361
362
G. POINAR JR.
RESULTS
Specimen Sd–9–158, identified as belonging to the
subtribe Livistoninae, did not conveniently fit into any
extant genera and is described below in a new genus.
Palmae Juss. 1789
Coryphoideae J. W. Griff. 1844
Corypheae C. Mart. 1837
Livistoninae Saakov 1954
Palaeoraphe Poinar gen. nov. (Figs 1–2, 5–8)
Diagnosis: Perfect flower; calyx of three broad sepals,
connate for more than half their length, their apices
irregular to fringed; petals 3, united basally in a tube
as long as sepals, valvate apically, furrowed adaxially;
stamens 6, borne at the mouth of the corolla tube, filaments connate into a 6-lobed ring, lobes triangular,
tapering to narrow tips. Stamens opposite petals
reflexed with the anthers resting on the middle of
three depressions on the adaxial surface of the petal;
stamens alternate with the petals, partially erect.
Anthers broadly elliptical, dorsifixed, dehiscence
latrose; carpels basically distinct, strongly ridged and
resembling the unexpanded cotyledons of a walnut;
styles fused for most of their length, with their tips
recurved, stigmas flattened.
Etymology: From Greek palaios – ancient; raphia – a
genus of palms.
Notes: The tribe Livistoninae contains 12 extant
genera in both Old and New Worlds (Uhl & Dransfield,
1987). The new genus shares floral characters with
Brahea, Acoelorraphe and Colpothrinax but the
general overall floral structure, especially the furrows
on the petals, the distinct sepals, and the size and
shape of the anthers is closest to Brahea. However, in
the latter genus, the styles are united for their entire
length and no stigmas are differentiated. Also in
Brahea, the anthers are more erect and the ovary is
normally smooth. These characters separate the two
genera. The ridged carpels, recurved tips of the styles
and reflexed petals opposite the stamens are unique
characters which do not occur in other members of this
subtribe.
Type species: Palaeoraphe dominicana Poinar sp.
nov. Figs 5–10
Diagnosis: As for genus. Greatest diameter of flower,
10.8 mm; distance from stigmas to base of calyx tube,
4.4 mm; length of petals, 5.7 mm; largest diameter at
base of ovary, 1.7 mm; length of stamens, 2.7 mm;
length filaments, 1.5 mm; length of anthers, 1.1 mm;
petals with three depressions on the adaxial surfaces,
inner depression 1.4 mm long, containing reflexed
anther, outer depressions flanking anther, 1.6 mm and
1.7 mm long, respectively; styles, petals and stamens
glabrous.
Holotype: Sd–9–158 (Dominican amber).
Etymology: From the site of origin, Dominican
Republic.
Locality: La Toca mine, Cordillera Septentrional,
Dominican Republic.
Note: The staminate and pistillate flowers in
Sd–9–101 could not be assigned to any extant species
of Roystonea and are described below as a new species.
Since they are in the same piece of amber, they are
considered to have originated from the same plant. It
would be highly unlikely that two separate species of
Roystonea would leave flowers in the same amber
piece.
Roystonea palaea Poinar sp. nov. (Figs 3, 9, 10)
Diagnosis: Staminate flower (Sd–9–101A): 3 sepals,
imbricate, triangular, 2 mm long, 1.9 mm wide; 3 distinct petals, ovate, dark brown, valvate, about 2.8
times the length of the sepals, stamens 6, filaments
awl-shaped, greatest width at base, c. 1 mm; anthers
elongate, white, 1.7–3.1 mm long, versatile, sagittate
basically, dorsifixed near middle, latrose, pollen not
observed, pistillode concealed from view.
Pistillate flower (Sd–9–101B) ovoid, with 3 distinct,
brown, imbricate sepals, 2.7 mm in length, petals 3,
ovate, with acute lobes at apex, brown, 3.4 mm long;
gynoecium subglobose, style not distinct, stigmas 3,
recurved, developing fruit subglobose, perianth persistent, epicarp smooth, black.
Holotype: Staminate flower (Sd–9–101A) in Dominican
amber.
Paratype: Pistillate flower (Sd–9–101B) in Dominican
amber.
Figures 1–4. Palm flowers. Figs 1–2. Palaeoraphe dominicana sp. nov. (Sd–9–158). Fig. 1. Complete flower. Scale
bar = 3.0 mm. Fig. 2. Adaxial surface of petal and stamen. Scale bar = 0.6 mm. Fig. 3. Pistillate flower of Roystonea palaea
sp. nov. (Sd–9–101B). Note perianth partially removed from ovary and two scratches on the latter (arrows). Scale bar = 0.8
mm. Fig. 4. Staminate flower (Sd–9–104) in Baltic amber. Scale bar = 1.3 mm.
© 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 361–367
PALM FLOWERS IN AMBER
1
2
3
4
© 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 361–367
363
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G. POINAR JR.
Figures 5–10. Palm flowers. Figs 5–8. Palaeoraphe dominicana sp. nov. (Sd–9–158). Fig. 5. Complete flower showing
arrangement of petals and stamens. Note ridges on ovary. Scale bar = 1.1 mm. Fig. 6. Adaxial view of petal and stamen
showing lateral grooves flanking anther. Scale bar = 1 mm. Fig. 7. Detail of calyx with irregular apices on sepals. Same
magnification as Fig. 6. Fig. 8. Dorsal view of stigmas and tips of recurved styles. Same magnification as Fig. 6. Fig. 9.
Pistillate flower of Roystonea palaea sp. nov. (Sd–9–101B). Scale bar = 0.5 mm. Fig. 10. Staminate flower of Roystonea
palaea sp. nov. (Sd–9–101A). Scale bar = 1 mm.
Etymology: From Greek palaios – ancient.
Locality: La Toca mine, Cordillera Septentrional,
Dominican Republic.
Notes: Floral characteristics of the genus Roystonea
include pistillate flowers with petals connate basically,
valvate distally and staminate flowers nearly sym-
metrical, with 3 distinct short sepals and 3 distinct
ovate large valvate petals. The fruits retain the stigmatic remains (Uhl & Dransfield, 1987). Unfortunately the staminodial tube in the pistillate flower
could not be seen due to damage to the fruit. Petal
colour and fruit shape are important characters in
separating extant Roystonea species (Zona, 1996),
However in the present specimens, only the anthers
© 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 361–367
PALM FLOWERS IN AMBER
have retained a light colour which is similar to some
extant species which are described as possessing
white anthers (Zona, 1996). All other colours appear
to have darkened to shades of brown, thus precluding
their use in the description. The major character separating the fossil from extant members of Roystonea
is the large size of the calyx in both staminate and
pistillate flowers (Figs 9, 10). While the pistillate
fossil flower has a petal/sepal ratio of 1.2, all extant
species have this ratio greater than 1.5 (Table 1). This
ratio in the fossil staminate flower is 2.2–2.6, but it is
over 4.0 in all modern Roystonea flowers except R.
oleracea and R. dunlapiana (Table 1). However, R.
oleracea has larger anthers than those of the fossil
(3.5–4.7 mm vs. 1.7–3.1 mm) and the apices of the
anthers are not recurved in the fossil species as they
are in R. oleracea. The sepals of the pistillate flowers
are longer in the fossil (2.27 mm) than in R. oleracea
(1.5–1.8 mm), making the P/S ratio 1.7–1.9 in R. oleracea but only 1.2 in the fossil. Staminate flowers of
Roystonea dunlapiana have sepals only one half as
long as the fossil (1 mm vs. 2 mm), and the anthers are
purple. Measurements of the pistillate flowers of R.
dunlapiana were not available for comparison (Zona,
1996).
Species of Roystonea occur throughout the tropical
Greater Antilles, Central America and northern South
America as well as in subtropical areas of southern
Florida (Zona, 1996). One side of the pistillate flower
of R. palea has a portion of the perianth removed
as well as two scratches on the developing fruit. It
is possible that the ovary had been seized by a
herbivore and dropped into the resin before it could
be consumed. Birds and bats are known to feed on
the oily fruit of extant Roystonea (Zona, 1996), and
one of the above could have been the source of the
noted injury.
Table 1. Petal/Sepal length ratios for extant and the fossil
Roystonea palms (Data obtained from Zona, 1996)
Species
Staminate flowers
Pistillate flowers
altissima
borinquena
4.0–6.5
4.6–7.6
2.0–3.0
1.8–2.0
dunlapiana
lenis
maisiana
oleracea
princeps
regia
stellata
violacea
2.9–5.6
4.3–4.6
4.1–4.2
2.1–2.8
8.5
4.4–4.6
–
5.7
–
1.9–2.4
1.9–2.1
1.7–1.9
2.9–3.1
2.1–3.9
2.3–3.5
2.5
palaea (fossil)
2.2–2.6
1.2
365
Two perfect palm flowers in a single piece of
Dominican amber (Sd–9–102). One of these flowers
is partially obscured by bubbles in the amber and
measurements are based on the second, more distinct
flower. Sepals, three, brown, connate at base, 3.7 mm
long, free portion triangular, with faint veins; petals
3, valvate, brown, veins pronounced, 3.7 mm long;
(only four anthers are present), filaments awl-shaped,
anthers elongate, white, 1.8 mm long, versatile,
dorsifixed near middle, dehiscence latrose, pollen
not observed, gynoecium with three elongate styles,
1.8 mm long, stigmas absent (Fig. 11). These specimens cannot be assigned to any modern palm group
at this time.
Baltic staminate palm flower (Sd–9–104). Floret
just opening, well- preserved, 4.9 mm in height, sepals
3, tan, 1.6 mm long, connate at base for 0.9 mm;
petals 3, valvate, tan, veins pronounced, length 4.3–
4.6, stamens 6; filaments hidden from view, anthers
2.4–2.7 mm long, elongate, tan, method of attachment not observed, pollen not observed (Figs 4,
12, 13).
This specimen resembles the one described by
Conwentz (1886) as Phoenix eichleri from Baltic
amber. One curious feature of the present specimen is
the presence of branched trichomes inside the partially opened floret. Because of their location, it could
not be determined if these trichomes originated from
some portion of the palm or from another source, such
as members of the Fagaceae which occur in the same
amber deposit and are well known for their abundant
supply of branched trichomes.
DISCUSSION
Diversification of palm genera in the American tropics
during the Tertiary was probably quite great, and the
disappearance of select palm lineages from Hispaniola
over the past 20 Myr is quite probable. It has been suggested that the palms originated in the late Mesozoic
on the then adjoining land masses of Africa and South
America (Moore & Uhl, 1973). If this were the case,
palms would have had some 140 Myr years to speciate
throughout tropical America, including the Greater
Antilles. It is likely that Palaeoraphe was a stenotopic
(intolerant of a wide range of conditions) tropical
genus that was restricted to the Greater Antilles or
possibly just to the island of Hispaniola. The disappearance of tropical lineages of animals and plants
from the original amber forest as a result of climatic
shifts during the Pliocene–Pleistocene has been proposed (Poinar & Poinar, 1999). Such climatic shifts
would have eliminated the strictly stenotopic lineages
such as Palaeoraphe but not the eurytopic forms
(based on their presence in subtropical areas today)
such as Roystonea.
© 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 361–367
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G. POINAR JR.
Figures 11–13. Palm flowers. Fig. 11. Lateral view of complete flower of specimen Sd–9–102 in Dominican amber. Scale
bar = 1 mm. Fig. 12. Lateral view of staminate flower (Sd–9–104) in Baltic amber. Scale bar = 0.7 mm. Fig. 13. Dorsal view
of staminate flower of Sd–9–104 in Baltic amber. Scale bar = 1.5 mm.
Climatic changes were much more extensive in
northern Europe in the area of the Baltic deposits,
ranging from subtropical in the Eocene at the time of
the amber deposits to cool temperate in the Oligocene
(Prothero, 1994). Stenotypic forms, including all palm
lineages, disappeared at that latitude, many leaving
descendants at the generic or family level in various
parts of the Old World Tropics (Larsson, 1978; Poinar,
1992).
The presence of both pinnate and palmate palms in
the Dominican amber forest had already been predicted on the basis of the discovery of two insects
whose modern descendants are intimately associated
with palms. A palm bug, Palaeodoris lattini Poinar &
Santiago-Blay (1997), whose closest relative today is
the royal palm bug, Xylastodoris luteolus, that occurs
in Cuba and Florida, was predicted as probably
feeding on Roystonea in the original amber forest
(Poinar & Poinar, 1999). The existence of palmate
palms was based on the discovery of a palm bruchid,
Caryobruchus dominicanus Poinar (1999), in Domini-
can amber. The present study now provides direct evidence of both types of palms in the original amber-producing forest
ACKNOWLEDGEMENTS
The author expresses his gratitude to Scott Zona and
Roberta Poinar for comments on earlier versions of
this manuscript and to Scott Zona for providing references related to this study.
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© 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 361–367