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J. Bot. Res. Inst. Texas 10(1): 141 – 146. 2016
BREVITRIMARIS ARCUATUS GEN. & SP. NOV., A MONOCOTYLEDONOUS
FOSSIL FLOWER FROM MID-TERTIARY AMBER DEPOSITS
IN THE DOMINICAN REPUBLIC
Kenton L. Chambers George O. Poinar, Jr.
Department of Botany and Plant Pathology Department of Integrative Biology
Oregon State University Oregon State University
Corvallis, Oregon 97331, U.S.A. Corvallis, Oregon 97331, U.S.A.
chamberk@science.oregonstate.edu
ab str ac t
A fossi l flower in am ber from the Dom inican Re public is desc ribed as t he new genus and sp ecies Brevitrimaris arcuatus. Its floral a nd pol-
len cha racterist ics favor placem ent in the Monocot yledonae, but assignment to a moder n family is u ncertain . The flower is act inomorphic,
with 3 l ance-ovate s epals th at are spread ing to shar ply refle xed and are ex terior to 3 ovate p etals. The p erianth p arts are t omentose aba xially
and short-pilate and roughened adaxially. Three short stamens occupy the center of the f lower, sur rounding a short style with a capitate
stigm a. The sagittate anthers are cu rved, 4-locular, and latrors ely dehiscent . Pollen is monosulc ate. The ovary of the pistil is hidden by the
stame ns. A tentat ive relati onship to Hae modoracea e is proposed , but other fam ilies t hat might be co nsidered a re Arecace ae, Burma nniace ae,
Liliaceae, a nd Xyridaceae.
re su men
Se desc ribe una flor fósil en ámbar de la Republica Dominica na como nuevo género y es pecie Brevitrimaris arcuatus. Sus características
flor ales y de polen i ndican su sit uación en Monoc otiledóne as, pero su as ignación a u na famil ia modern a es inciert a. La fl or es actinomór fica,
con tre s sépalos lonceol ado-ovados q ue se extiende n hasta ser re flejos y son ex teriores a los t res pétalo s ovados. Las pa rtes del per ianto son
tomentos as abax ialmente y c ortament e pilosas y r ugosos ada xialm ente. Tres est ambres cor tos ocupan e l centro de la f lor, rodean do un estilo
corto con u n estigm a capitado. La s anteras sa gitadas e stán cur vadas, 4- locular, y dehi scentes de mo do latrorso. El p olen es monosu lcado. El
ovari o del pistilo e stá oculto por lo s estambre s. Se propone una r elación tent ativa con Haemo doraceae, pero ot ras fami lias que pud ieran ser
consideradas son Ar ecaceae, Burmanniace ae, Liliaceae, y Xyridaceae.
int rodu cti on
Amber mines in the Dominican Republic have yielded numerous animal and plant species representative of
Caribbean Mid-Tertiary tropical forests. Characteristics of these forests were described by Poinar and Poinar
(1999), based on amber fossils then available. Since that publication, various insects and other animal species
have been described, as well as some 25 plant taxa, including both modern and extinct genera (see Poinar &
Chambers 2015; Chambers & Poinar 2016). Exact dat ing of these fossils is d ifficult, wit h a range of ages having
been proposed (see Mater ials and Method s). The term Mid-Te rtiary i s broad enough to include the prob able age
of the amber deposits.
The fossil described here has monosulcate pollen (Fig. 5C) and a generalized monocot floral morphology
of 6 perianth parts, the 3 outer tepals (sepals) being longer and more lanceolate than the 3 inner ones (petals),
which otherwise are similar in texture to the sepals (Figs. 1–3). The margins of the petals overlap the sepals at
the base. Abaxial pubescence of the sepals and petals is densely tomentose (Fig. 2), the adaxial surface being
irregularly cobbled, with short pilate trichomes and rosette-like clusters of 2–5 cells (Fig. 4). Stipitate-glandu-
lar tr ichomes (Figs. 5A–B) are scattered on the petal margins. The 3 short stamens surround the style and pos-
sess sagittate, arched anthers with downward-curved tips (Fig. 3). The anthers are 4-locular, latrorsely dehis-
cent, and release pollen in the vicinity of the stigma (Fig. 3). The ovary is obscured by the anthers and may be
either superior or inferior.
Characteristics of the flower tentatively suggest a relationship to the Haemodoraceae, a mainly tropical
and subtropical family of 14 genera and 107 species, distributed from eastern North America to Mesoamerica,
northern South America, South Africa, New Guinea, and Australia (Simpson 1998; Hopper et al. 1999). The
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142 Journal of the Botanical Research Institute of Texas 10(1)
genus Lachnanthes, found in bogs along the eastern seaboard of North America, has 3 stamens and an inferior
ovary, but its perianth trichomes are not glandular (Simpson 1990, Fig. 168), the perianth parts are narrowly
lance-li near, and the stamen s are exserted on long filaments (pers. obser v.). The eastern Nor th American genus
Lophiola, with 6 erect to spreading stamens and a half-inferior ovary, is sometimes placed in Haemodoraceae
(Robertson 2002) but is probably better assigned to Melanthiaceae (Ambrose 1985) or Nartheciaceae (Zomle-
fer 1997; Hopper et al. 1999). The fossil differs in one or more respects from other modern genera of Haemo-
doraceae described in Simpson (1990, 1998). The assignment to this family is uncertain, and a relationship to
other families of Monocotyledons might also be suggested, such as Arecaceae, Burmanniaceae, Liliaceae, and
Xyridaceae (anon., in litt.).
mat er ia ls an d me tho ds
Proposed ages of Dominican amber are based on planktonic m icrofossils found in t he marine strata in which it
was originally deposited. An estimated age of 20–15 Ma (Itur ralde-Vinent & MacPhee 1996) was derived from
foraminifera, whereas 45–30 Ma, based on coccoliths, was proposed by Cépek (in Schlee 1999). The deposits
are marine sandstones of the Upper Eocene to Lower Miocene Mamey Group (Draper et al. 1964). From the
appearance of the amber, Dilcher et al. (1992) suggested that “the age of the amber is greater than Miocene and
quite likely is as early as late Eocene.” Other Caribbean amber is known from the early Paleocene of Puerto
Rico (Iturralde-Vinent 2001).
The block of amber was cut and polished close to the fossil so as to allow microscopic study and photog-
raphy. Observations and photographs were made with a Nikon SMA-10R stereoscopic microscope and Nikon
Optiphot compound microscope with magnifications up to 600X. Helicon Focus Pro X54 was used to stack
photos for better depth and clarity. Our search for possible familial relationships of the fossil included exami-
nation of monocot keys and illustrations in floras of the Southeastern United States, Mexico, the Caribbean,
and northern South America. Other useful literature is cited in the References section.
des cr ipt ion
Brevitrimaris K.L. Chambers & Poinar, gen. nov. (Figs. 1–5). type species: Brevitrimaris arcuatus K.L. Chambers & Poinar,
sp . nov.
Flower perfect, radially symmetrical, perianth biseriate, sepals 3, spreading to sharply recurved, lance-ovate,
abaxially densely tomentose-puberulent (Fig. 2), adaxially short-pilate and roughened with rosette-like clus-
ters of 2– 6 cells (Fig. 4), apex acute, m argins enti re, smooth or spars ely ciliate, petals 3, recu rved, ovate, shorter
than sepals and overlapping them at the base (Figs. 1–3), similar in texture and pubescence to sepals (Figs.
2–4), apex acute, margins entire or sparsely ciliate, with scattered stipitate-glandular trichomes (Figs. 5A–B),
stamens 3, short and clustered in the center of the flower (Figs. 1, 3), anthers surrounding pistil, sagittate,
slightly arcuate laterally, the tips curving downward (Fig. 3), thecae forking at base, locules 4, dehiscence la-
trorse (Fig. 3), pistil mostly obscured by stamens, style short, stigma capitate, held slightly above the anthers
(Fig. 3), ovary not visible, pollen monosulcate (Fig. 5C).
Brevitrimaris arcuatus K.L. Chambers & Poinar, sp. nov. ty pe: HISPANIOLA. dominican republic: amber mines in the
northern mount ain ranges (Cordillera Septent rional), between Puerto Plata and Santiago, 1985, unkno wn ambe r miner s.n. (holo-
type: Cat. No. Sd-9 -140, deposit ed in the Poinar a mber collect ion, Oregon Stat e University, Cor vallis, Or egon 97331, U.S.A.)
Flower pedicellate, pedicel 0.8 mm long, perianth 3.3 mm in diameter when sepals are spread, sepals 1.4–1.6
mm long, 1.0–1.3 mm wide, petals 1.3 mm long, 0.8– 0.9 mm wide, stamens short, surrounding the pistil, fila-
ments not visible, anthers held horizontally, ca. 0.5 mm long, style slightly exceeding stamens, stigma small,
capitate, pollen monocolpate (Fig. 5C).
Etymology.—Genus name from Latin “brevis,” short, “tri,” three, and “mas, maris,” man, referring to the
3 stamens. Species name from Latin “arcuatus,” bent like a bow, with reference to the curved anthers.
Two of the 3 sepals are recurved (Fig. 2), which was probably their usual position in mature flowers. The
tight clustering of the anthers around the pistil obscures the ovary and style as well as the filaments, for which
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Chambers and Poinar, Brevitrimaris arcuatus gen. & sp. nov. 143
Fig. 1. Brevitrimaris arcuatus in Dominican amber. Apical view of flower. A. Sepal. B. Petal. Note petal margins overlapping sepals. C. Anther. Scale bar
= 0.9 μm.
Fig. 2. Brevitrimaris arcuatus in Dominican amber. Lateral view of flower. A. Strongly recurved sepal. Note dense abaxial covering of trichomes. B. Petal.
The petal is adaxially grooved. Scale bar = 0.4 μm.
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144 Journal of the Botanical Research Institute of Texas 10(1)
measurements are not given. The flower is at anthesis, and the longitudinal, latrorse dehiscence of the locules
is clea rly visible (Fig. 3). Pollen grain s are present on the st igma, showing t he plant’s facilit y for self-poll ination.
The way the inner tepal whorl overlaps the outer is similar to flowers of Xiphidium caeruleum as illustrated by
Lentz (2004, Fig. 231). Pubescence of the adaxial surface of the sepals and petals is a combination of short,
curved, few-celled trichomes and a surface cobbled or roughened by variably-sized clusters of rounded cells
(Fig. 4). The short trichomes are suggestive of the example of pilate trichomes with an enlarged terminal cell
illustrated by Simpson (1990, Fig. 10) for Dilatris of Haemodoraceae subfamily Haemodoroideae, but the apex
is not as densely cytoplasmic. The rough-textured epidermal surface (Fig. 4) has clusters of cells, some of
which have the rosette form seen characteristically at the base of the elongated pilate trichomes illustrated by
Simpson for many genera of Haemodoraceae (op. cit., Figs. 9–20). A lateral view of the flower (Fig. 2) shows a
slight broadening of the receptacle immediately above the pedicel, which may indicate the presence of an infe-
rior ovary, but other interpretations are possible respecting ovary position.
Fig. 3. Brevitrimaris arcuatus in Dominican amber. Enlarged apical view of flower. A. Anther with curved tip. Note latrorse dehiscence of thecae. B. Stigma.
C. Sepal. Note puberulence on adaxial surface. Scale bar = 0.5 μm.
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Chambers and Poinar, Brevitrimaris arcuatus gen. & sp. nov. 145
dis cus sion
The molecular phylogenetic studies of Hopper et al. (1999)
verify the monophyletic status of the Haemodoraceae and of
its two subfamilies, Haemodoroideae and Conostylidoideae.
Only the former subfamily is represented in the New World.
Outgroups used in their cladistic analysis were Pontederia-
ceae, Philydraceae, and Commelinaceae. No unequivocal
synapomorphie s for the family were found. The authors suggest that the Haemodoraceae are an ancient group,
perhaps dating from the Cretaceous, in which significant extinction of earlier lines has occurred, leaving an
interruptedly relictual geographic distribution.
Three stamens (rarely 1) characterize the 4 New World genera of Haemodoraceae, and like the fossil,
these are placed opposite the inner perianth parts (Maas & Mass-van de Kamer 1993, Fig. 2). Among these
genera, only Lachnanthes has an inferior ovary. Schiekia, Pyrrorhiza, and Xiphidium have a superior ovary and
differ f rom Brevitrimaris in characteristics of the perianth and a ndroecium. The presence of pilate t richomes in
the 3 Central and South American genera mentioned above, is also found in Barberetta, Dilatris, and Wachen-
dorfia of South Africa. Similar trichomes could not be unequivocally demonstrated in Brevitrimaris, although
some cellular clusters resemble the rosettes illustrated by Simpson (1990, Figs. 9–20) as basal to such tri-
chomes. The irregular cellular cobbling of the epidermis is otherwise unique, and similarities to Haemodora-
ceae should not be overdrawn.
Family assignment of Brevitrimaris, for example by a comparison with Haemodoraceae as above, is made
diffic ult by lack of inform ation on the nature of the pollen exine, as well as morpholog y or position of the ovar y,
presence or absence of an hy panthium, and other floral det ails hidden from v iew by the close approximation of
stamens to pistil. Unfortunately, it is not possible to section amber-embedded flowers without destroying
them, and examination by electron microscopy, which might clarify details of t he pollen exine and other floral
features, is not feasible. Ordinary microscopy, as shown in Figures 4 and 5, is possible due to clarity of the
amber, and this gives the best available view of cellular morphology. It might be expected that placement in a
modern family is difficult for a fossil of late Oligocene or early Miocene age.
Fig. 4. Brevitrimaris arcuatus in Dominican amber. Adaxial epidermis of petal. Note
clusters of rounded cells giving a cobbled appearance. Scale bar = 50 μm.
Fig. 5. A–B. Stipitate-glandular trichomes from margins
of petal of Brevitrimaris arcuatus in Dominican amber.
C. Pollen grains. Arrows indicate the sulcus on each
grain. Scale bars: A = 50 μm, B = 35 μm, C = 11 μm.
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146 Journal of the Botanical Research Institute of Texas 10(1)
ack now le dgm ent s
We thank Terry MacFarlane and an anonymous reviewer for their useful suggestions and corrections. Lori
Hilterbrand and Kelly Holcomb of the staff of the Valley Library, Oregon State University, kindly provided as-
sistance with the literature.
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Inquiries regarding distributable and open access versions may be directed to jbrit@brit.org.
