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A Morphotype Catalogue, Floristic Analysis and Stratigraphic Description of the Aspen Shale Flora(Cretaceous–Albian) of Southwestern Wyoming

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We describe 28 fossil plant morphotypes from the Aspen Shale flora (Cretaceous: middle to late Albian) in southwestern Wyoming. This impression flora includes 6 ferns, 1 sphenopsid, 2 conifers, 17 dicotyledonous angiosperm (dicot) leaves and 2 dicot reproductive structures. The Aspen Shale megaflora is most similar to that of Subzone IIB of the Potomac Group of the eastern United States. Analysis of the Aspen Shale sedimentology and botanical composition shows occupation of open, paludal sites by a succession of progressively more complex plant communities. Like other middle Cretaceous floras, these data suggest that early angiosperms were weedy, herbaceous to shrubby, early successional competitors to ferns on open substrates. The description and illustration of the Aspen Shale morphotypes is presented as an example of how an entire flora can be described and analyzed before full taxonomic determinations have been made.
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Introduction
Fossil floras can provide important insights into
land-plant evolution, paleocology, biogeography
and climate (e.g., Hickey and Doyle 1977; Gra-
ham 1999; Hoffman and Stockey 1999; Manches-
ter 1999; Wilf, Johnson et al. 2003; Peppe et al.
2007). A traditional floristic monograph includes
taxonomic and systematic descriptions of all en-
tities in a flora. However, taxonomic and system-
atic identifications are seldom completed, be-
cause the assignment of each entity to its correct
systematic group and taxon requires knowledge
of: (1) plant morphology; (2) the systematic dis-
tribution of plant characters; (3) phylogenetic re-
lationships; (4) the detailed taxonomy of a wide
range of plant groups; and (5) extensive research
into the nomenclature of each taxon. There are
also inherent difficulties in dealing with fossil
plant material: preservation is always incomplete,
organs are often separated, characters are often
enigmatic, and many extinct species and genera
have no modern relative to alleviate these prob-
lems. Furthermore, a large proportion of older
paleobotanical literature is full of nomenclatural
errors, misidentifications and imprecise, inaccu-
rate and missing descriptions and illustrations of
species (see discussions in Hickey 1973; Dilcher
1974; Hickey and Wolfe 1975). Thus, any taxo-
nomic study of a fossil flora is a tedious and time-
consuming process that greatly impedes the
timely realization of the floras broader potential.
Despite these difficulties, once operational
taxonomic units have been established for a fos-
Bulletin of the Peabody Museum of Natural History 49(2):181–208, October 2008.
© 2008 Peabody Museum of Natural History, Yale University. All rights reserved. • http://www.peabody.yale.edu/
A Morphotype Catalogue, Floristic Analysis
and Stratigraphic Description of the Aspen Shale Flora
(Cretaceous–Albian) of Southwestern Wyoming
Daniel J. Peppe, Leo J. Hickey, Ian M. Millerand Walton A. Green
Department of Geology and Geophysics, Yale University, P. O. Box 208109, New Haven CT 06520-8109 USA
— email: daniel.peppe@yale.edu, leo.hickey@yale.edu
Denver Museum of Science and Nature, 2001 Colorado Blvd., Denver CO 80205 USA
— email: ian.miller@dmns.org
National Museum of Natural History, P. O. Box 37012, MRC 121,
Smithsonian Institution, Washington, DC 20013 USA
— email: wagreen@bricol.net
A
We describe 28 fossil plant morphotypes from the Aspen Shale flora (Cretaceous: middle to late
Albian) in southwestern Wyoming. This impression flora includes 6 ferns, 1 sphenopsid, 2
conifers, 17 dicotyledonous angiosperm (dicot) leaves and 2 dicot reproductive structures. The
Aspen Shale megaflora is most similar to that of Subzone IIB of the Potomac Group of the east-
ern United States. Analysis of the Aspen Shale sedimentology and botanical composition shows
occupation of open, paludal sites by a succession of progressively more complex plant communi-
ties. Like other middle Cretaceous floras, these data suggest that early angiosperms were weedy,
herbaceous to shrubby, early successional competitors to ferns on open substrates. The descrip-
tion and illustration of the Aspen Shale morphotypes is presented as an example of how an entire
flora can be described and analyzed before full taxonomic determinations have been made.
K
Paleobotany, morphotype, Aspen Shale, early angiosperm, early succession, Albian, Early
Cretaceous, Wyoming, floral catalogue.
T . Lithostratigraphic section for Aspen Shale locality. Unit is the stratigraphic bed; unit thickness is the
total thickness of the stratigraphic unit and total thickness is the measure of the stratigraphic section. Strati-
graphic levels of floral localities are indicated in bold.
Unit Total
thickness thickness
Unit (cm) (cm) Lithologic description of each stratigraphic unit
1 400 400 Medium grey silty shale, with 2 to 4 cm interbeds of tuffaceous
siltstone or rusty grey-brown, fine-grained sandstone.
2 100 500 Medium grey tuff, porcellaneous, aphanitic. Parallel bedded. Unit
forms a resistant shoulder.
3 90 590 Medium grey claystone, porcellaneous with parallel interbeds of
yellowish grey, fine-grained, tuffaceous sandstone from 5 to 20 cm-
thick.
4 560 1150 Tannish grey silty shale, with a tannish grey, resistant (tuffaceous),
porcellaneous bed 3.1 m above the base that thickens from 10 cm to
40 cm westward in the outcrop.
5501200 Sandstone, very fine-grained, tuffaceous, downcut 0.5 m into
underlying shale laterally. Trough cross-bedded at base; becoming
plane-bedded at top. Thins westward in outcrop. Flora 0026α
6 60 1260 Yellow-grey siltstone, porcellaneous, blocky, hackly, with some
vertical limonite staining.
7 20 1280 Light yellowish grey siltstone, porcellaneous, massive, blocky.
8601340 Light grey tuff, blocky. Upper 15 cm weathers to a punky texture,
with limonite staining and poorly preserved rhizomorphs. Flora
0026a
9 60 1400 Medium grey porcellinite, with vertical and horizontal rhizomorphs.
10 120 1520 Light yellow-grey siltstone, massive, blocky weathering, tuffaceous.
Has parallel and low-angle cross-lamination in the basal 40 cm. A
20-cm bed of light grey, tuffaceous siltstone, with vertical
rhizomorphs occurs 0.8 m above the base. The uppermost 20 cm is a
tuff with vertical and horizontal rhizomorphs and mats of fern
rachises. Flora 0026b
11 30 1550 Light yellowish grey silty tuff, chippy, with small plant fragments and
a twisted pinna of a AS1 at the base of the unit.
12 290 1840 Greenish grey siltstone, blocky weathering, with carbon films and
irregular bedding. Becomes medium greenish grey with
rhizomorphs and poorly preserved plant scraps laterally.
13 20 1860 Light yellowish grey siltstone.
14 130 1990 Greenish grey siltstone, blocky weathering, with carbon films and
irregular bedding.
15 200 2190 Greenish grey claystone, blocky, aphanitic. Mottled with limonite
and has disrupted texture, but contains no peds or rhizomorphs.
Poorly resistant.
16 90 2280 Greenish grey tuff, blocky weathering but massive, forms a ledge.
17 30 2310 Olive grey to light grey tuff, aphanitic. Flora 0026c.
18 70 2380 Olive grey siltstone, poorly resistant. Becoming more resistant and
aphanitic 50 cm above the base, with the uppermost 10 cm
consisting of a light grey silty tuff.
19 10 2390 Siltstone, tuffaceous.
20 170 2560 Medium olive grey, siltstone. Becomes more resistant in the topmost
40 cm. Flora 0026d occurs in uppermost 15 cm.
21 60 2620 Sandstone, very fine-grained, with low angle cross-lamination at the
base, which appears to be downcutting.
Bulletin of the Peabody Museum of Natural History 49(2) • October 2008
182
sil flora a range of methods can be applied to
them. These include: inference of paleoclimatol-
ogy (e.g., Bailey and Sinnot 1915; MacGinitie
1953; Wolfe 1979; Wing and Greenwood 1993;
Wolfe 1993; Wilf 1997; Wilf et al. 1998; Forest et
al. 1999; Burnham et al. 2001; Jacobs 2002; Huff
et al. 2003; Kowalski and Dilcher 2003; Green-
wood et al. 2004; Greenwood et al. 2005; Royer et
al. 2005; Miller et al. 2006; Meyer 2007); paleoe-
cology (e.g., Spicer 1989; Wing et al. 1993; Wilf,
Cuneo et al. 2003; Green and Hickey 2005; Royer
et al. 2005; Wilf et al. 2005; Royer et al. 2007); and
biostratigraphic zonation (e.g., Crabtree 1987;
Johnson and Hickey 1990; Johnson 2002; Wilf
and Johnson 2004). These studies can be espe-
cially informative when the biotic data are ana-
lyzed in relation to the sedimentologic and strati-
graphic framework of the deposit in which the
plants occur. However, precisely because of the
difficulties involved in their taxonomic identifi-
cation, studies of whole floras have lagged seri-
ously over the last 40 years or so, just as these
powerful new tools have been developed.
Because the methods described above can be
used even when only morphologic operational
taxonomic units are employed, one solution to
the taxonomic problem is to handle paleobotan-
ical data outside of a Linnaean framework. In pa-
lynology (e.g., Potonié 1956–1975; Hughes 1970,
1976; Traverse 1988) and in megafloral paleob-
otany (Ferguson 1971) researchers have designed
non-Linnaean systems for floral analysis. How-
ever, these systems are all still hierarchical and
rank-based and, in the case of the Ferguson
(1971) study, the system placed species level op-
erational taxonomic units in the lowest Linnaean
taxonomic rank possible (class to genus).
Our approach is based on the morphotype
concept described in Johnson (1989). This
method is independent of the Linnaean system
and uses morphological characteristics of the
various categories of plant organs, such as leaves
or fruits, to differentiate a flora into operational
taxonomic units. Morphotypes are “selected to
express the total variety of distinct topologic en-
tities present in a flora” (Johnson 1989:70). There
can be multiple morphotypes within one species
(e.g., Cercidiphyllum genetrix: Brown 1939,
1962; Hickey 1977) and multiple species or even
genera in a single morphotype (e.g., Sabalites:
Read and Hickey 1972). When the work of es-
tablishing morphotypes has been carefully done
on large collections of fossil plants, the resulting
categories will often, but not always, coincide
with biologic species. Morphotypes are unique to
the study site, study area or formation, and to the
researchers working on a particular collection.
The morphotype system allows for rapid classifi-
cation of floras and makes it possible to focus on
questions of interpretation rather than on taxo-
nomic issues. As time permits, the morphotypes
can later be attributed to a Linnaean taxon.
In this paper we provide a catalogue of the
Aspen Shale flora for the use of the morphotype
method for the rapid documentation of an entire
flora. In our view, a floral catalogue should, at a
minimum, include descriptions and illustrations
of all morphotypes in a flora. It should also give
sufficiently detailed geographic and stratigraphic
information to identify the site and the age of the
flora. In this catalogue we have also included pre-
liminary taxonomic information, limited syn-
onymies and detailed sedimentological and
environmental interpretations of the site. The
morphotypes described in this catalogue are di-
vided into three categories: (1) those identified
strictly as numerical morphotypes; (2) those rec-
ognized as morphotypes whose previously pub-
lished taxonomic name we regard as invalid or
illegitimate, or whose assignment is incorrect or
doubtful; and (3) those that can be assigned to
valid and legitimate species with a reasonable de-
gree of certainty.
The Aspen Shale flora is significant as one of
the few Early Cretaceous angiosperm floras in
the Rocky Mountain region (Crabtree 1987; Mc-
Clammer and Crabtree 1989). Because of its po-
tential to provide a window on the timing, rates
and ecology of early angiosperm occupation of
the region, we feel that it is important to publish
what we know of the flora in advance of its full
taxonomic study.
Locality and
Geologic Setting
The Aspen Shale plant locality (designated
LJH9918 and LJH0026; the latter is used
throughout the remainder of this paper) is on the
south side of the junction of Roney (formerly
Everly) Creek and Fontenelle Creek (lat 42.08°N,
long 110.16°W), approximately 30 km north of
The Aspen Shale Flora (Cretaceous–Albian) of Southwestern Wyoming • Peppe et al. 183
Kemmerer, in Lincoln County, Wyoming, USA,
in the so-called Overthrust Belt (Figure 1).
Roland W. Brown visited the site in 1930 and
wrote the only published report on it 3 years later
(Brown 1933). To our knowledge, no major col-
lecting occurred at this locality until its rediscov-
ery by Hickey in 1999 and a subsequent visit by
Hickey and Green in 2000. A small collection
made by S. Manchester, P. Crane and M.
Collinson and is housed at the Field Museum in
Chicago (S. Manchester, personal communica-
tion 2008).
The fossil plant locality lies within 40 m of
the upper contact of the Aspen Shale. This for-
mation consists of black shale, dark grey arena-
ceous shale and drab grey sandstone between
400 and 600 m thick (Schultz 1914). Its strata dip
westward and form a series of rounded, elongate,
north–south trending hills west of a high, con-
tinuous ridge of the overlying Frontier Forma-
tion. The Aspen Shale is thought to be predomi-
nately marine, because of the presence of abun-
dant fish scales and rare linguloid brachiopods,
ammonites and pelecypods (Schultz 1914; Ree-
side and Weymouth 1931). However, the Aspen
Shale strata at the plant site seem to have been
deposited in a paludal setting and contain a sig-
nificant component of volcaniclastic sediment.
The Aspen Shale overlies the Bear River Forma-
tion. The dark-colored shale, thin-bedded lime-
stone and sandstone of the marine Bear River
Formation form a belt of topographically more
subdued landscape to the east of the Aspen out-
crop (Schultz 1914). These formations range in
age from Albian for the Bear River and the Aspen
to Cenomanian for the Frontier (e.g., Nichols
and Jacobson 1982; M`Gonigle et al. 1995).
Stratigraphy and Sedimentology
The stratigraphic section at the Aspen Shale
plant locality (see Figure 1; Table 1), contains a
high concentration of volcaniclastic material,
Bulletin of the Peabody Museum of Natural History 49(2) • October 2008
184
F . A, B. Fossil leaf locality, indicated by star in B. C. Stratigraphic section of locality LJH0026. The strati-
graphic position of floral levels is shown on the right (sh, shale; zs, siltstone; tuff/ss, tuffaceous unit/sandstone).
with several beds of porcellaneous tuff. The basal
11 m of the section consists of parallel-bedded,
fissle shale with 2 to 4 cm interbeds of tuffaceous
siltstone. This is separated into two units (1 and
4) by a 2 m thick interval of tuff (unit 2) and in-
terbeds of tuffaceous sandstone and siltstone
(unit 3). The upper shale bed also contains a lens
of tuff (up to 40 cm thick). Weathering colors in
the lower sequence are predominantly medium
grey.
The plant-bearing interval comprises the
upper 14 m of the section and lies above a down-
cut surface at the base of the sandstone desig-
nated as unit 5 (see Figure 1; Table 1). Although
the strata above that level are still highly tuffa-
ceous, there is a marked change in the type of
sedimentary structures, with disrupted bedding,
vertical and horizontal rhizomorphs, carbon
films, mottling and yellow grey to greenish grey
weathering in various intervals (especially to-
ward the upper boundaries of units) throughout
the sequence. While Brown (1933) only de-
scribed one fossiliferous bed, we found fossil
plants in 5 distinct beds. One of these (unit 5) is
a tuffaceous sandstone, 3 are tuffs (units 8, 11
and 17) and the uppermost (unit 20) is a massive
siltstone. Units 17 and 20 are probably the main
sources of Brown’s published flora.
Sedimentary Interpretation
The stratigraphic section seems to represent a
change from predominantly marine to terrestrial
sedimentation after a lowering of base level that
allowed incipient soils to develop before being
inundated by ash falls or debris flows. The floras
here are interpreted as representing a series of
early successional fern-dominated, and later an-
giosperm-dominated, communities that colo-
nized a bare substrate and grew until they were
destroyed by an episode of sedimentation. Tuff
beds in the terrestrial part of the section are fre-
quently laminated and are barren of plant re-
mains, except toward their bases and tops. The
basal few centimeters of a typical tuff bed often
contain comminuted plant matter that some-
times seems to have been charred or burned. The
upper 10 to 40 cm of a typical tuff frequently
show a steady increase in brownish coloration
and an increase in carbon content. Rhizomorphs
and limonite staining, especially on incipient cu-
tans, are present in the upper interval of typical
tuff beds. Recognizable plant fossils in mats of
plant remains occur in the uppermost 15 to 20
cm of the plant-bearing beds. Each of these as-
semblages seems to represent a pioneer plant
community that was colonizing an incipient soil
developing on the upper surface of an ash flow
or, in the case of unit 20, on a floodplain soil.
Methods
Stratigraphic and Floral
Collection Methods
The section was measured by first exposing
bedrock and bedding contacts, then systemati-
cally logging the beds to the nearest centimeter
using an Abney level and a Jacob staff. During
logging of the section, the lithology, lithologic
unit thickness, sedimentary structures, fossil
content and Munsell color were recorded. Beds
were physically traced laterally to determine the
extent of the floral deposits.
During fossil collecting, the floral levels were
logged into the measured section in stratigraphic
order: flora LJH0026α was collected from unit 5,
flora LJH0026a from unit 8, LJH0026b from unit
11, LJH0026c from unit 17 and LJH0026d from
unit 20 (see Figure 1, Table 1). A preliminary flo-
ral collection was made in 1999 and floral census
collections were made in 2000 from floras
LJH0026b, LJH0026c and LJH0026d. During the
census collection, all identifiable leaf specimens
were tallied and examples of each morphotype
were collected, and the distribution and abun-
dance of specific morphotypes among the desig-
nated stratigraphic intervals was tabulated (Table
2). The specimens are curated at the Peabody
Museum of Natural History at Yale University.
Floral Description
In this treatment, we include descriptions and
figures of all morphotypes. The morphotypes are
ordered according to broad taxonomic category
(i.e., ferns and sphenopsids, conifers and di-
cotyledonous angiosperms [dicots]). The dicots
are first classified by organ type. The leaves are
grouped by their organization and margin. We
have included limited synonymies. However,
note that, for all synonymies, the described mor-
photype can only be related to the cited publica-
tions and not necessarily to the type specimen or
to other references to the species. The morpho-
The Aspen Shale Flora (Cretaceous–Albian) of Southwestern Wyoming • Peppe et al. 185
Bulletin of the Peabody Museum of Natural History 49(2) • October 2008
186
T . List of morphotypes, their presence or absence, and census data for Aspen Shale flora. Abbreviations:
For affinity into taxonomic category (Affinity): FER, fern; SPH, sphenopsid; CON, conifer; DIC, dicotyledon.
For plant organ (Plant): L = leaf; R = reproductive structure. For organization of angiosperm leaf (Org): S, sim-
ple leaf; C, compound leaf; , absent. For dicotolydon angiosperm leaf margin type (Margin): E, entire; T,
toothed; , absent. For fossil leaf levels at Aspen Shale locality (LJH0026α, LJH0026a, LJH0026b, LJH0026c,
LJH0026d) , presence; , absence; the number of specimens tallied in the census collection is given in paren-
theses.
Locality levels
Morphotype LJH LJH LJH LJH LJH
Affinity Plant Org Margin number Taxon 0026α 0026a 0026b 0026c 0026d
FER L ⴑⴑ AS1 “Amenia ⴑⴒ(75) (23)
freemontii
FER L ⴑⴑ AS2 Baieropsis sp. ⴑⴒ(54) (5)
FER L ⴑⴑ AS3 Cladophlebis ⴒⴒ(14) (1) (0)
readii
FER L ⴑⴑ AS4 ⴑⴑ(0) ⴑⴒ(0)
FER L ⴑⴑ AS5 “Microtenia ⴑⴑⴒ(25)
paucifolia
FER L ⴑⴑ AS6 “Asplenium ⴑⴑⴑ ⴒ(0)
occidentale
FER L ⴑⴑ AS26 Housemania sp. ⴑⴑⴒ(0)
SPH L ⴑⴑ AS12 Equisitites sp. ⴑⴑ(0) ⴑⴒ(12)
CON L ⴑⴑ AS7 ⴑⴑⴑ ⴒ(18)
CON L ⴑⴑ AS8 ⴑⴑⴒ(1)
DIC R AS9 “Sparganium ⴑⴑⴑ ⴒ(12) (1)
aspensis
DIC R AS33 ⴑⴑⴑ
DIC L S E AS16 ⴑⴑⴑ ⴒ(9) (0)
DIC L S E AS17 ⴑⴒⴑ
DIC L S E AS20 ⴑⴑⴒ(1)
DIC L S E AS34 ⴑⴒⴑ
DIC L S T AS10 “Sassafras ⴑⴑⴑ ⴒ(0) (1)
bradleyii
DIC L S T AS11 ⴑⴑⴒ(1)
DIC L S T AS13 “Populus ⴑⴑⴑ ⴒ(6) (0)
aspensis
DIC L S T AS18 “Prunus ⴑⴑ(2) (25) (0)
aspensis
DIC L S T AS25 ⴑⴑ(0) (1)
DIC L S T AS27 ⴑⴑⴒ(4)
DIC L S T AS28 ⴑⴑⴑ ⴒ(0) (0)
DIC L S T AS29 ⴑⴑ(1) ⴑⴒ(1)
DIC L S T AS31 ⴑⴑⴒ(3)
DIC L S T AS32 Sapindopsis ⴑⴑⴑ ⴒ(2) (2)
shultzii
DIC L C E AS19 Sapindopsis ⴑⴑ(0) (25) (65)
magnifolia
DIC L C T AS14, Sapindopsis ⴑⴑⴑ ⴒ(51) (5)
AS30 belviderensis
types described below have been placed into 3
categories on the basis of the certainty of taxo-
nomic identification (see Introduction, above,
for a complete description of these categories):
1. No previous description is known and no
name is proposed (e.g., AS2).
2a. Genus is incorrect or invalid, but the species
name is valid (e.g., “Anemia fremontii
Brown, 1933).
2b. Those associated with a previously published
but uncertain or incorrect identification (e.g.,
Microtaenia paucifolia”).
3. As far as is known, this is a correct identifica-
tion to a valid and legitimate genus and species
(e.g., Cladophlebis readii Brown, 1933).
Format of Floral Description
The descriptions follow the format of Johnson
(1996), which is a modification of Hickey (1977).
The terms used are based on Ash et al. (1999)
and Hickey (1973). Each morphotype is de-
scribed in the following format:
Morphotype number.
Taxonomic name.
Systematic affinity.
Previous identification.
Synonymy.
Description. Organization of laminae. Lamina shape
and preservation. Lamina length; lamina width;
length-to-width ratio; apex shape; base shape; margin
type; other characters of the lamina (e.g. petiole,
glands, etc.). Category and preservation of primary ve-
The Aspen Shale Flora (Cretaceous–Albian) of Southwestern Wyoming • Peppe et al. 187
F . “Anemiafremontii Brown, 1933, AS1. A. YPM 56068, bipinnate frond, showing alternate to subal-
ternate arrangement. B. YPM 56068, close-up of frond showing pinnatasect, subopposite pinnules. Scale bars
= 1 cm.
F . A, B. Cladophlebis readii Brown, 1933, AS3. A. YPM 55897, frond showing subalternate to alternate
arrangement of pinnules. B. YPM 55897, close-up of pinnule showing bifurcated venation. C. Baieropsis sp.,
AS2, YPM 55913, frond showing subopposite, irregular dissection to even pinnate arrangement of pinnules.
D. AS4, YPM 56096, pinnate frond with stout rachis. Scale bars = 1 cm.
Bulletin of the Peabody Museum of Natural History 49(2) • October 2008
188
nation; thickness of primary vein(s); presence of agro-
phic veins; category and preservation of secondary ve-
nation; arrangement and spacing of secondary veins
on primary; number of secondary vein pairs; angle of
secondary vein departure from primary; secondary
vein course; nature of intersecondary veins. Category
and preservation of tertiary venation; tertiary vein
course; position and orientation of tertiary veins for
the primary and secondary veins; tertiary vein spacing.
Higher order venation. Areolation; tooth type, tooth
venation; tooth shape.
Morphotype exemplar.
Discussion.
Terms and Definitions
Used in Floral Description
The following systematic descriptions use these
terms: “Morphotype number” is a numerical
designation that distinguishes an entity with a
unique morphology within the flora; using the
convention established by Johnson (1989), this is
a 2-letter prefix based on the formation name
plus a number starting from one. “Previous iden-
tification” indicates that this morphotype has
been identified and published before, but that the
identification is incorrect or uncertain; this term
will only be used for morphotypes in category 2b.
“Morphotype exemplar” is the specimen that
best exemplifies the characters of the morpho-
type and may be changed if a better specimen is
found.
Description
of Morphotypes
Ferns and Sphenopsids
AS1
Figure 2A, B
Anemiafremontii Brown 1933
Systematic affinity: Class Filicopsida; Order Filicales; Family
and Genus incertae sedis.
Synonymy: Anemia fremontii Brown, 1933:3, pl. 1, fig. 3
(USNM 39136).
Description: Frond bipinnate; pinnules typically arranged al-
ternately to subalternately, occasionally odd-pinnate. Pinnules
pinnatisect, subopposite, forming a low angle with the rachilla.
Venation dichotomizing, no reticulation. Margin irregularly
toothed, veins appear to end in tooth sinus.
Morphotype exemplar: YPM 56058.
AS2
Figure 3C
Baieropsis aff. B. expansa Fontaine 1889
Systematic affinity. Class Filicopsida; Order Filicales; Family
Schizeaceae.
Description. Pinnules irregularly dissected; arrangement of
pinnules subopposite to even pinnate. Venation open dichoto-
mous. Irregular, terminally bifurcated veins give appearance of
an irregularly toothed margin.
Morphotype exemplar. YPM 55913, YPM 55976 (part and
counterpart).
Discussion. This morphotype belongs to Fontaine’s (1889)
genus Baieropsis. It likely belongs to the species B. expansa,
which is the type species of Baieropsis. However, the Aspen
Shale material does not have sporangia, making the species as-
signment uncertain. Berry (1911) later made B. expansa the
type of his genus Schizaeopsis. Under Article 11.3 of the Code
The Aspen Shale Flora (Cretaceous–Albian) of Southwestern Wyoming • Peppe et al. 189
F . “Microtaenia paucifolia,” AS5, YPM 56058,
fertile frond showing subopposite to opposite attach-
ment of fertile material. Scale bar = 1 cm.
of Botanical Nomenclature (Greuter et al. 2000), Baieropsis
Fontaine (1889) is the correct name for this taxon and Berry’s
genus Schizaeopsis is an illegitimate junior synonym. The
complex of fern species recognized by Fontaine (1889) as
Baieropsisis most abundant in Potomac Group Zone I, but ex-
tends upward to Subzone IIC (Clark et al. 1911:90–91; Hickey
and Doyle 1977).
AS3
Figure 3A, B
Cladophlebis readii Brown, 1933
Systematic affinity. Class Filicopsida; Order Filicales; Family
Osmundaceae.
Synonymy. Cladophlebis readii Brown, 1933:4, pl. 1, fig. 2
(USNM 39138).
Description. Frond bipinnate, rachis stout. Pinnule arrange-
ment subalternate to alternate. Pinna broadly attached to
rachis; pinnules pinnatisect, asymmetrical, falcate, bending to-
ward apex of frond. Veins bifurcate twice and terminate at the
margin.
Morphotype exemplar. YPM 55897, YPM 55969 (part and
counterpart).
AS4
Figure 3D
Systematic affinity. Class Filicopsida; Order Filicales; Family,
Genus and species incertae sedis.
Description. Frond once-pinnate, deeply pinatifid, rachis stout.
Pinnules opposite to alternate; dissected part way to the
rachilla, forming lobes; rachilla perpendicular to the rachis.
Midrib of pinnule distinct; secondary veins bifurcate up to two
times. Margins of pinnules entire.
Morphotype exemplar. YPM 56906.
AS5
Figure 4
Microtaenia paucifolia
Systematic affinity. Class Filicopsida; Order Filicales; Family
Matoniaceae; Genus and species incertae sedis.
Previous identification. Microtaenia paucifolia (Hall) Knowl-
ton, Brown 1933:4, pl. 1, fig. 4 (USNM 39139).
Description. Fertile frond. Opposite to subopposite attachment
of reproductive fertile material. Fertile material orbicular. Ve-
nation of frond pinnate.
Morphotype exemplar. YPM 56058.
AS6
Figure 5
Aspleniumoccidentale
Systematic affinity. Class Filicopsida; Order, Family and Genus
incertae sedis.
Synonymy. Asplenium occidentale Brown, 1933:3, pl. 1, fig. 5
(USNM 39137).
Description. Shape of pinnule uncertain. Pinnae lobed. Veins
bifurcate at least twice, no reticulation, veins curved abaxially
and ending at the margin. Margin toothed, teeth sharp-pointed
with rounded sinuses, veins go to tips of teeth.
Morphotype exemplar. YPM 56132.
AS26
Figure 6
Hausmannia sp.
Systematic affinity. Class Filicopsida; Order Filicales; Family
Dipteridaceae.
Description. Leaf small, less than 5 cm wide by 5 cm long. Mar-
gin serrate and highly dissected; multi-lobed. Pinnate primary
Bulletin of the Peabody Museum of Natural History 49(2) • October 2008
190
F . “Aspleniumoccidentale, AS6, YPM 56132,
pinna showing bifurcated venation. Scale bar = 1 cm.
The Aspen Shale Flora (Cretaceous–Albian) of Southwestern Wyoming • Peppe et al. 191
F . A–C. Hausmania sp., AS26. A. YPM 56082, small multi-lobed leaf showing serrate, highly dissected
margin. B. YPM 56129, close-up of margin showing serrate teeth, arrows indicate spinose gland at end of tooth.
C. YPM 56129, close-up of end of lobe showing serrate teeth that do not have spinose glands. Scale bars = 1 cm.
venation; secondary veins semicraspedodromous or reticulo-
dromous. One order of teeth, 2 teeth per centimeter, spacing ir-
regular, shape irregular, sinus rounded, some teeth spinose.
Morphotype exemplar. YPM 56129, YPM 56082 (part and
counterpart).
AS12
Figure 7C
Equisetites sp.
Systematic affinity. Class Sphenopsida; Order Equisetales;
Family Equisetaceae.
Description. Whorled leaves at nodes; leaves linear with no ev-
ident venation. Stem 0.5 to 1.0 cm wide; vertical, linear stria-
tions on stem.
Morphotype exemplar. YPM 55996.
Conifers
AS7
Figure 7D
Systematic affinity. Class Coniferopsida; Order, Family, Genus
and species incertae sedis.
Bulletin of the Peabody Museum of Natural History 49(2) • October 2008
192
F . A. Sparganiumaspensis Brown, 1933, AS9, YPM 56001, inflorescence showing alternate attach-
ment of probably flower heads. B. AS8, YPM 56069, conifer showing adpressed, spirally arranged scales.
C. Equisetites sp., AS12, YPM 55878, whorled leaves around stem. D. AS7, YPM 55782, branch showing 1 to
2 cm long needles. E. AS33, YPM 56151, angiosperm (see D). Scale bars = 1 cm.
Description. Needles alternate, possibly spirally arranged. Nee-
dles 1 to 2 cm long, dorsiventrally flattened; bases clasping
branchlet; single vein in each needle.
Morphotype exemplar. YPM 55782.
Discussion. This morphotype resembles Glyptostrobus End-
licher (1847), which is known from other Early Cretaceous flo-
ras (e.g., LePage 2007), but was not confirmed by cones or cone
scales.
AS8
Figure 7B
Systematic affinity. Class Coniferopsida; Order, Family, Genus
and species incertae sedis.
Description. Adpressed, spirally arranged scales. Scales 1 to 3
mm, sharp-pointed.
Morphotype exemplar. YPM 56069
The Aspen Shale Flora (Cretaceous–Albian) of Southwestern Wyoming • Peppe et al. 193
F . AS16. A. YPM 56095, base of leaf showing 5 basal veins. B. YPM 55883, apex of leaf showing entire
margin and opposite percurrent tertiary veins. Scale bars = 1 cm.
Discussion. This morphotype resembles Brachyphyllum
Brongniart (1828), but the generic assignment was not con-
firmed by cones or cone scales.
Dicot Angiosperm
Reproductive Structures
AS9
Figure 7A
Sparganiumaspensis
Systematic affinity. Class Magnoliopsida; Order, Family, and
Genus incertae sedis.
Synonymy. Sparganium aspensis Brown, 1933:4, pl. 2, fig. 2
(USNM 39140).
Description. Inflorescence consisting of orbicular, alternately
attached heads of probable flowers.
Morphotype exemplar. YPM 56001, YPM 56064 (part and
counterpart).
Discussion. “Sparganiumaspensis (AS9) can likely be as-
signed to the genus Platanocarpus Friis, Crane, and Pederson
(1988)
AS33
Figure 7E
Systematic affinity. Class Magnoliopsida; Order, Family, Genus
and species incertae sedis.
Description. Elliptic, 0.5 cm long seed.
Morphotype exemplar. YPM 56151.
Simple, Entire, Dicot Leaves
AS16
Figure 8A, B
Systematic affinity. Class Magnoliopsida; Order, Family, Genus
and species incertae sedis.
Description. Leaf simple, mesophyll-sized. Leaf symmetrical;
base rounded to obtuse, base angle obtuse; petiolar attachment
marginal; margin entire at base. Primary venation actinodro-
mous, at least 5 basal veins; secondary veins likely brochido-
dromous; tertiary veins opposite percurrent; fourth-order
veins opposite percurrent. Leaf may be lobed.
Morphotype exemplar. YPM 56095.
AS17
Figure 9; Figure 10B
Systematic affinity. Class Magnoliopsida; Order, Family, Genus
and species incertae sedis.
Description. Leaf simple, ovate, microphyll-sized. Leaf sym-
metrical; apex rounded, apex angle acute; base rounded, base
angle obtuse; apex may be glandular; margin entire. Primary
venation pinnate; secondary veins festooned brochidodro-
mous, secondary vein spacing irregular; basal secondary vein
angle irregular; intersecondary veins absent; tertiary veins al-
ternate percurrent, obtuse to primary vein, inconsistent angle
variability; fourth-order venation polygonal, regular reticulate;
fifth-order venation dichotomizing; areoles moderately well
developed; freely ending veinlets branched.
Morphotype exemplar. YPM 56018.
Discussion. The festooned brochidodromous secondary vena-
tion, the regular polygonal reticulate fourth-order venation, the
dichotomizing fifth-order venation, the moderately well-devel-
oped areolation, and the branched freely ending veinlets sug-
gest that this morphotype is likely a species of the genus Fico-
phyllum Fontaine (1889).
Bulletin of the Peabody Museum of Natural History 49(2) • October 2008
194
F . AS17, YPM 56018, ovate, microphyll-sized
leaf. Scale bar = 1 cm.
The Aspen Shale Flora (Cretaceous–Albian) of Southwestern Wyoming • Peppe et al. 195
F . A. AS20, YPM 56063, apex of ovate leaf showing reticulodromous venation. B. AS17, YPM 56018,
close-up of apex of leaf showing higher order venation. C. AS34, YPM 56138, long, linear leaves. Scale bars =
1 cm.
AS20
Figure 10A
Systematic affinity. Class Magnoliopsida; Order, Family, Genus
and species incertae sedis.
Description. Simple, ovate, microphyll-sized leaf. Leaf asym-
metrical; margin entire. Primary venation pinnate; secondary
venation reticulodromous.
Morphotype exemplar. YPM 56063
AS34
Figure 10C
Systematic affinity. Class Magnoliopsida; Order, Family, Genus
and species incertae sedis.
Description. Long, linear, thin leaf. Margin entire. One promi-
nent midvein.
Morphotype exemplar. YPM 56138.
Simple, Toothed Dicot Leaves
AS10
Figure 11; Figure 12
Sassafrasbradleyi
Bulletin of the Peabody Museum of Natural History 49(2) • October 2008
196
F . “Sassafrasbradleyii Brown, 1933, AS10,
YPM 56077a, leaf showing suprabasal actinodromous
venation. Scale bar = 1 cm.
F . “Sassafrasbradleyii Brown, 1933, AS10. A. YPM 56073b, base of leaf showing suprabasal actin-
odromous primary venation. B. YPM 56073a, 3-lobed leaf showing lobes with round apices. Scale bars = 1 cm.
Systematic affinity. Class Magnoliopsida; Order, Family, and
Genus incertae sedis.
Synonymy. Sassafras bradleyi Brown, 1933:7, pl. 2, fig. 5
(USNM 39144).
Description. Leaf ovate, notophyll- to mesophyll-sized. Leaf
symmetrical; apex acute to rounded; base acute to decurrent;
margin toothed or entire; 3 lobes, lobes rounded to acute at
apices; intrafoliar glandular dots present. Primary venation
suprabasal actinodromous; 3 or more basal veins; secondary
veins festooned brochidodromous to weakly brochidodro-
mous, irregularly spaced, secondary vein angle approximately
45° to the primaries; tertiary venation random reticulate, vein
course and vein angle to primary random; fourth-order vena-
tion random reticulate. When toothed, one order of teeth,
shape convex/concave (CV/CC), sinus rounded, apex
rounded.
Morphotype exemplar. YPM 56077a, b.
The Aspen Shale Flora (Cretaceous–Albian) of Southwestern Wyoming • Peppe et al. 197
F . A–B. Populusaspensis Brown, 1933, AS13. A. YPM 56003, nanophyll-sized with showing cordate
base. B. YPM 5906, nanophyll-sized leaf with rounded apex. C. AS11, YPM 55996, base of leaf with deeply cor-
date base. D. “Prunusaspensis Brown, 1933, AS18, YPM 56008, leaf with cordate base and pinnate primary ve-
nation. Scale bars = 1 cm.
AS11
Figure 13C
Systematic affinity. Class Magnoliopsida; Order, Family, Genus
and species incertae sedis.
Description. Leaf simple, very broad ovate, microphyll-sized.
Leaf symmetrical; apex rounded, angle obtuse; base deeply cor-
date; petiolar attachment marginal; margin crenate. Primary
veins basal actinodromous; 5 basal veins; one pair of weak agro-
phic veins; secondary veins semicraspedodromous. One order
of teeth, 3 to 4 teeth per centimeter, tooth spacing regular, tooth
shape convex/convex (CV/CV), sinus sharp, apex rounded.
Morphotype exemplar. YPM 55996.
AS13
Figure 13A, B
Populusaspensis
Systematic affinity. Class Magnoliopsida; Order, Family, and
Genus incertae sedis.
Synonymy. Populus? aspensis Brown 1933:5, fig. 1 (USNM
39141).
Description. Simple, ovate to elliptic, nanophyll-sized leaf. Leaf
symmetrical; apex rounded, angle acute; base cordate, angle
obtuse; margin serrate. Primary vein pinnate; secondary veins
craspedodromous, basally crowded, secondary vein angle
slightly increasing to base; tertiary veins mixed opposite–alter-
nate, vein course irregular, angle to primary vein obtuse, angle
variability inconsistent; fourth-order veins roughly orthogonal
to tertiary veins. One order of teeth, irregular spacing, tooth
shape CV/CC, sinus rounded, apex glandular.
Morphotype exemplar. YPM 55906.
Discussion. The teeth and higher order venation suggest that
this morphotype may be a member of the Trochodendraceae.
AS18
Figure 13D
Prunusaspensis
Systematic affinity. Class Magnoliopsida; Order, Family, and
Genus incertae sedis.
Synonymy. Prunus aspensis Brown 1933:9, pl. 2, fig. 4 (USNM
39147).
Description. Simple, ovate, mesophyll-sized leaf. Leaf asym-
metrical; apex acute; base cordate; margin crenate to serrate.
Primary vein pinnate; secondary veins semicraspedodromous;
no higher order venation preserved. Teeth crenate to serrate,
one order of teeth, tooth shape CV/CV, sinus angular, simple to
possibly glandular apex.
Morphotype exemplar. YPM 56008.
Bulletin of the Peabody Museum of Natural History 49(2) • October 2008
198
F . AS25, YPM 56178. A. Close-up of margin of leaf showing teeth and higher order venation. Arrows
indicate position of crenate teeth. B. Large leaf (a, position of midvein; b, margin near base; c, toothed margin
shown in A). Scale bars = 1 cm.
AS25
Figure 14
Systematic affinity. Class Magnoliopsida; Order, Family, Genus
and species incertae sedis.
Description. Megaphyll-sized leaf. Margin crenate. Primary
venation pinnate; secondary venation weakly brochidodro-
mous; tertiary veins random reticulate. One order of teeth, 4
teeth per centimeter, spacing regular, shape concave/concave
(CC/CC), sinus rounded, apex pointed.
Morphotype exemplar. YPM 56178.
AS27
Figure 15
Systematic affinity. Class Magnoliopsida; Order, Family, Genus
and species incertae sedis.
Description. Simple, elliptic, microphyll-sized leaf. Leaf sym-
metrical; length-to-width ratio 1:1; apex rounded, angle acute;
base cordate, angle obtuse; petiolar attachment marginal; mar-
The Aspen Shale Flora (Cretaceous–Albian) of Southwestern Wyoming • Peppe et al. 199
F . AS27. A. YPM 56077b, leaf with rounded apex and cordate base. B. YPM 56007a, leaf with actin-
odromous primary venation and one pair of agrophic veins showing crenate margin. Scale bars = 1 cm.
Bulletin of the Peabody Museum of Natural History 49(2) • October 2008
200
F . AS28. A. YPM 56073b, ovate leaf with acute apex and base. B. YPM 56099, close-up of leaf show-
ing highly ascending secondary veins. C. YPM 56076, close-up of margin of leaf showing closely spaced serrate
teeth. Arrows indicate position of teeth. Scale bars = 1 cm.
The Aspen Shale Flora (Cretaceous–Albian) of Southwestern Wyoming • Peppe et al. 201
F . A. Sapindopsisschultzii Brown, 1933, AS32, YPM 56116b, ovate leaf with straight apex and ser-
rate margin. B. AS29, YPM 55899, leaf with lobes and large teeth. C. AS31, YPM 55877, microphyll-sized leaf
with serrate margin. Scale bars = 1 cm.
gent crenate. Primary venation actinodromous to palinactin-
odromous; one pair of agrophic veins; secondary veins fes-
tooned brochidodromous to reticulodromous; tertiary veins
random reticulate. One order of teeth, 3 to 4 teeth per cen-
timeter, tooth spacing regular, shape CV/CV, sinus rounded,
apex rounded and glandular.
Morphotype exemplar. YPM 56077.
AS28
Figure 16
Systematic affinity. Class Magnoliopsida; Order, Family, Genus
and species incertae sedis.
Description. Simple, ovate to linear, notophyll- to mesophyll-
sized leaf. Leaf symmetrical; length-to-width ratio 7:1; apex
acute, angle acute; base acute, angle acute; petiolar attachment
marginal; margin minutely serrulate, but in most specimens
appearing entire, perhaps due to marginal enrollment. Primary
venation pinnate; secondary veins craspedodromous, veins
highly ascending toward margin; tertiary veins opposite per-
curent. Teeth very small, in one order, 3 to 5 teeth per cen-
timeter, spacing irregular, shape CV/CC to CV/CV, sinus
rounded.
Morphotype exemplar. YPM 56076
Discussion. This morphotype can be distinguished from AS31
and AS32 (“Sapindopsisshultzii) by the size and shape of its
teeth and a much greater length-to-width ratio of the lamina.
AS29
Figure 17B
Systematic affinity. Class Magnoliopsida; Order, Family, Genus
and species incertae sedis.
Description. Notophyll-sized leaf. Apex angle acute; margin
serrate; multi-lobed. Primary venation pinnate; secondary
veins craspedodromous to semicraspedodromous; tertiary
veins loosely and irregularly percurrent, vein course irregular
and slightly sinuous; fourth-order venation random reticulate.
Two orders of teeth, 3 to 4 teeth per centimeter, spacing irreg-
ular, shape CV/CV, sinus rounded to acute, apex rounded to
sharp, tooth glandular, chloranthoid tooth. Lamina has glan-
dular dots.
Morphotype exemplar. YPM 55899, YPM 56023 (part and
counterpart).
AS31
Figure 17C; Figure 18
Systematic affinity. Class Magnoliopsida; Order, Family, Genus
and species incertae sedis
Description. Simple, ovate, microphyll-sized leaf. Leaf sym-
Bulletin of the Peabody Museum of Natural History 49(2) • October 2008
202
F . Sapindopsis magnifolia Fontaine, 1889,
AS19, YPM 56073a, bi-lobed terminal leaflet. Scale
bar = 1 cm.
F . AS31. A. YPM 55975, leaf with serrate
margin and acute apex. B. YPM 56052, leaf with
rounded base and acrodromous secondary venation.
Scale bars = 1 cm.
metrical; length-to-width ratio 3:1; apex acute, angle acute;
base rounded; petiolar attachment marginal; margin serrate.
Primary venation acrodromous; one pair of agrophic veins;
secondary veins craspedodromous; higher order venation ran-
dom reticulate. One order of teeth, 6 to 8 teeth per centimeter,
spacing regular, shape CV/CV, sinus rounded, apex sharp and
glandular.
Morphotype exemplar. YPM 56052.
Discussion. This morphotype can be distinguished from AS28
and AS32 (“Sapindopsisshultzii) by is acrodromous primary
venation and the size and shape of its teeth.
AS32
Figure 17A
Sapindopsisshultzii
Systematic affinity. Class Magnoliopsida; Order, Family, Genus
incertae sedis.
Synonymy. Sapindopsis shultzii Brown, 1933:10, pl. 1, fig. 7
(USNM 39149).
Description. Simple, ovate, notophyll- to mesophyll-sized leaf.
Leaf symmetrical; length-to-width ratio 3:1 to 6:1; apex
straight, angle acute; margin serrulate. Primary venation pin-
nate; secondary veins semicraspedodromous; higher order ve-
nation random reticulate. One order of teeth, 4 to 6 teeth per
centimeter, spacing regular, shape CV/CV, sinus acute, apex
rounded to sharp.
Morphotype exemplar. YPM 5611a, b.
Discussion. The teeth and venation of this morphotype suggest
that it may be a species of Crassidenticulum. This morphotype
can be distinguished from AS28 and AS31 by its pinnate pri-
mary venation and the size and shape of its teeth.
Compound, Entire Dicot Leaves
AS19
Figure 19; Figure 20; Figure 21
Sapindopsis magnifolia
Systematic affinity. Class Magnoliopsida; Order and Family in-
certae sedis.
Synonymy. Sapindopsis magnifolia Fontaine 1889:297, pl.
151, fig 2–3, pl. 152, fig. 2–3, pl. 153, fig. 2, pl. 154, fig. 1, 5,
pl. 155, fig. 6.
Laurus aspensis Brown 1933:6, pl. 2, fig. 1 (USNM 39143).
Description. Leaf odd-pinnate compound, oppositely attached.
Leaflets lanceolate to elliptic, notophyll-sized, except the termi-
nal leaflet, which is obovate and notophyll-sized. Leaf symmet-
rical to rarely asymmetrical; apex rounded to acute; base acute
The Aspen Shale Flora (Cretaceous–Albian) of Southwestern Wyoming • Peppe et al. 203
F . Sapindopsis magnifolia Fontaine, 1889,
AS19. A. YPM 56077a, elliptic leaflet with pinnate
primary venation. B. Slightly asymmetrical leaflet.
Scale bars = 1cm.
F . Sapindopsis magnifolia Fontaine, 1889,
AS19, YPM 56070, odd-pinnate compound leaf
showing attached leaflets. Scale bar = 1 cm.
Bulletin of the Peabody Museum of Natural History 49(2) • October 2008
204
F . Sapindopsis belvedierensis Berry, 1922, AS14, YPM 56077a. A. Terminal leaflet with 3 lobes.
B. Close-up of margin of leaf showing crenate margin. Arrow indicates tooth. Scale bars = 1 cm.
to decurrent; margin entire; terminal leaflet unlobed to bi-
lobed. Primary venation in unlobed leaves pinnate, primary
venation in lobed leaves suprabasal actinodromous; secondary
venation weakly brochidodromous, vein spacing irregular, vein
angle decreasing to base; inter-secondary veins present; tertiary
veins random reticulate.
Morphotype exemplar. YPM 56070.
Compound, Toothed Dicot Leaves
AS14
Figure 22
Sapindopsis belvedierensis
Systematic affinity. Class Magnoliopsida; Order and Family in-
certae sedis.
Synonymy. Berry 1922:216–217, pl. 49, fig 1–7, pl. 50, fig. 1, pl.
51, fig. 1, pl. 52, fig. 1, pl. 53, fig. 1–2, pl. 54, fig. 2.
Description. Leaflet obovate, mesophyll-sized. Apex acute;
base acute; margin crenate, typically 3-lobed. Primary veins
suprabasal actinodromous to palinactinodromous, 5 basal
veins; secondary veins craspedodromous, vein spacing irregu-
lar; no higher order venation preserved. Large teeth. One order
of teeth, 2 to 3 teeth per centimeter; spacing regular, shape
CV/CC to CV/CV, sinus rounded, apex acute to rounded, teeth
become rounded and more symmetrical to leaf apex.
Morphotype exemplar. YPM 56076, YPM 56099 (part and
counterpart).
Discussion. The diagnostic features of this leaf are its large
teeth and its primary venation pattern. This is likely the termi-
nal leaflet of a compound Sapindopsis belvedierensis Berry
(1922) leaf.
AS30
Figure 23; Figure 24
Sapindopsis belvedierensis
Systematic affinity. Class Magnoliopsida; Order and Family in-
certae sedis.
Synonymy. Berry 1922:216–217, pl. 49, fig 1–7, pl. 50, fig. 1, pl.
51, fig. 1, pl. 52, fig. 1, pl. 53, fig. 1–2, pl. 54, fig. 2.
Description. Leaflet elliptic to obovate, notophyll-sized. Leaflet
symmetrical; length-to-width ratio 3:1; apex rounded, angle
acute; base cuneate to decurrent, angle acute; margin serrate.
Primary venation pinnate; secondary veins semicraspedodro-
mous, vein angle decreases towards base. One order of teeth, 1
tooth per centimeter, spacing regular, shape flexuous/convex
(FL/CV), flexuous/concave (FL/CC), CC/CC, sinus rounded,
apex rounded, apex occasionally glandular.
Morphotype exemplar. YPM 55882, YPM 55884 (part and
counterpart).
Discussion. This is likely a lateral leaflet of Sapindopsis
belvedierensis. It can be distinguished from AS14 by its pinnate
primary venation, leaf shape, and tooth type.
Biostratigraphic Correlation
and Paleoecological Interpretation
The presence of Sapindopsis belvedierensis and
the petiolulate form of S. magnifolia, combined
with the presence of palmately lobed leaves, the
variety of dicot angiosperm leaf types and the
The Aspen Shale Flora (Cretaceous–Albian) of Southwestern Wyoming • Peppe et al. 205
F . Sapindopsis belvedierensis Berry, 1922,
AS14, YPM 55884, obovate leaflet with large teeth.
Scale bar = 1 cm.
presence of AS7, “Sparganiumaspensis, allows
us to correlate the Aspen Shale flora with the
upper part of Subzone IIB of the Potomac Group
of the Middle Atlantic United States (Doyle and
Hickey 1976). This indicates a middle to late Al-
bian age (Doyle and Hickey 1976). In addition,
the occurrence of toothed, pinnatifid leaves of
Sapindopsis in middle to late Albian strata in the
Pacific northwest (Bell 1956), the Cheyenne
Sandstone of Kansas (Berry 1922) and the upper
Lakota and Fall River formations of the Black
Hills (Hickey and Doyle 1977) supports this
chronostratigraphic estimate.
At the outcrop scale, the floral composition
of the plant beds changes significantly upward in
the sequence (see Table 1). Ferns dominate the
lowest 3 floral levels. In the basalmost level,
LJH0026α, only a single fern species,
Cladophlebis readii (AS3), is present. In the next
two levels, LJH0026a and LJH0026b, C. readii
(AS3) also occurs with “Anemia fremontii
(AS1) and “Aspleniumoccidentale (AS6). An-
giosperms are rare in the third level, LJH0026b,
but become dominant in the fourth level,
LJH0026c. In this level Sapindopsis belvedieren-
sis (AS14, AS30) is the most abundant compo-
nent of the flora. S. magnifolia (AS19) and S.
belvedierensis dominate the angiosperm assem-
blage of the fifth and uppermost floral level
(LJH0026d), where C. readii is the only fern
present.
The trends toward increasing angiosperm
abundance and diversity are similar to trends
found in other early angiosperms assemblages
(e.g., the Potomac flora, Hickey and Doyle 1977),
suggesting three possible interpretations. The
first, and least likely, is ecological succession. The
strata are disturbed, but there are not patterns of
seral succession within these beds. A second in-
terpretation is that there is progressive ecological
displacement of early successional ferns by early
successional angiosperms through evolution and
immigration. Given typical continental sedimen-
tation rates, this interpretation seems unlikely
because the restricted thickness of the section
(about 13 m between lowermost and uppermost
floral levels; see Figure 1; Table 1) likely repre-
sents little time.
We favor a third interpretation, in which
ferns and angiosperms colonized disturbed envi-
ronments. We infer that the relative abundance
of ferns and angiosperms in each floral bed is due
to heterogeneity of the fluvial environment (see
Figure 1; Table 1). The Aspen Shale is similar to
other early angiosperm floras (e.g., Hickey and
Doyle 1977; Crabtree 1987; Wing et al. 1993) in
that it suggests that the angiosperms were early
successional, weedy to shrubby species that colo-
nized open substrates.
Acknowledgments
The authors thank Steve Roberts and Richardson
Ranches for access to the localities, and Steve
Manchester and an anonymous reviewer for
comments that improved this manuscript.
Received 24 January 2008; revised and accepted
9 May 2008.
Bulletin of the Peabody Museum of Natural History 49(2) • October 2008
206
F . Sapindopsis belvedierensis Berry, 1922,
AS14, YPM 55907, odd-pinnate compound leaf
showing attached leaflets with teeth. Scale bar = 1 cm.
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208
... eschweizerbart_xxx 54 C. K. West, D. R. Greenwood, and J. F. Basinger ically distinct groups of specimens, or morphotypes. Morphotypes are morphological groupings that may parallel traditional biological species concepts, but that have no formal taxonomic status ( Johnson 1989;Peppe et al. 2008;Ellis et al. 2009). Thus, the morphotype system can be used to develop a rigorous classification system unique to a fossil locality, geological unit, or basin that is independent of the traditional Linnean framework ( Johnson 1989;Peppe et al. 2008;Maxbauer et al. 2013). ...
... Morphotypes are morphological groupings that may parallel traditional biological species concepts, but that have no formal taxonomic status ( Johnson 1989;Peppe et al. 2008;Ellis et al. 2009). Thus, the morphotype system can be used to develop a rigorous classification system unique to a fossil locality, geological unit, or basin that is independent of the traditional Linnean framework ( Johnson 1989;Peppe et al. 2008;Maxbauer et al. 2013). ...
... The morphotype system has an advantage over Linnean taxonomy in that traditional taxonomic and systematic descriptions are often challenging and time-consuming processes, whereas, the morphotype system allows for fossil floras to be rapidly and rigorously classified ( Johnson 1989;Peppe et al. 2008). Thereby, allowing both palaeoecological and palaeoclimatological analyses to be applied to a flora before a complete taxonomic assessment occurs (e.g., West et al. 2015;Lowe et al. 2018). ...
Presentation
Understanding the causal mechanisms of the modern latitudinal diversity gradient (LDG) is a long-established problem in ecology. Temperature has been proposed as the primary driver of the modern LDG, although other hypotheses (e.g. precipitation, insolation, seasonality, biogeographical history, and biological interactions), have been suggested as constraints or drivers of diversity in the extra-tropics (i.e. the mid- and high-latitudes). The modern Arctic is characterized by very low floral diversity and a cold dry climate; however, the early Eocene Arctic was much warmer and wetter, as evidenced from paleobotanical climate reconstructions (e.g. MAT ≈ 8.5–12.7 ºC and MAP >150 cm/yr), and the presence of thermophilic flora and fauna (e.g. palm or palm-like palynomorphs and alligators). Nevertheless, forest diversity for Arctic Eocene ecosystems remains relatively untested and is typically described as low and homogenous. Reported here are the first quantitative megafloral diversity estimates from Stenkul Fiord, Ellesmere Island, Canada, utilizing two purpose-made census-sampled fossil leaf collections coupled with horizon-specific palynological analyses. Recent U-Pb zircon geochronology, and new geological mapping at Stenkul Fiord, place the fossil sites stratigraphically near the PETM and ETM2 hyperthermal events of the early Eocene, a time when warm equable climates allowed temperate and tropical plant taxa to survive at high northern latitudes. Diversity was assessed using coverage-based interpolation- and extrapolation-based rarefaction, a method that reconstructs richness with high accuracy. The results show that the early Eocene paleoarctic forests supported diverse forest ecosystems with floral diversity similar to modern mid-latitude mesic-mesothermal broadleaf forests from North America, but overall floral diversity may have been restricted as a result of photic seasonality. Furthermore, these ecosystems experienced floristic change probably related to the transient hyperthermal events.
... As seen in Fig. 7, The NMDS analysis clustered many fern genera around Site 2 and Site 4, which indicates that these sites were suitable environments for fern growth; likely high in moisture, recently disturbed, or boggy environments (Cremer & Mount, 1965;Gee, 2011;Howe & Cantrill, 2001;Peppe et al., 2008;Van Konijnenburg-Van Cittert, 2002). The NMDS analysis also clusters conifer taxa around site 1. ...
... Lamberson et al. (1996) suggests that orogenic uplift to the west led to periodic drought in the Gates Fm wetlands which in turn increased the frequency of wildfires which were likely occurring at the 20-40-year interval. Brown et al. (2020) Wyoming (Peppe et al., 2008) are contemporaneous and younger than the Gates Fm-middle to late Albian-but are geographically far apart and quite different to each other in terms of diversity. The biggest differences between these two Middle to Late Albian macrofloras are that Peppe et al. (2008) recorded 16 dicot angiosperm leaf morphotypes in the Aspen Shale whereas the Kukpowruk Fm contains none. ...
... Brown et al. (2020) Wyoming (Peppe et al., 2008) are contemporaneous and younger than the Gates Fm-middle to late Albian-but are geographically far apart and quite different to each other in terms of diversity. The biggest differences between these two Middle to Late Albian macrofloras are that Peppe et al. (2008) recorded 16 dicot angiosperm leaf morphotypes in the Aspen Shale whereas the Kukpowruk Fm contains none. The Aspen Shale also did not contain any conifers, cycads, or ...
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During the Cretaceous, large herbivorous dinosaurs (megaherbivores) acted as keystone species—just as large mammals do today (e.g., elephants)—yet despite their significance in Cretaceous ecosystems, what plant taxa these dinosaurs ate is unclear. The Albian armoured dinosaur Borealopelta markmitchelli (Ornithischia; Nodosauridae) was discovered in northern Alberta, Canada and has well-preserved stomach contents dominated by fern leaf tissues, with only trace amounts of gymnosperm material, implying selective feeding. The Lower Albian Gates Formation (Grand Cache Member) macroflora of central Alberta is contemporaneous and spatially proximal with B. markmitchelli and therefore provides information on local vegetation available to this nodosaur and other megaherbivores in this area. In this study we provide unbiased abundance data for the Gates Fm macroflora. These data also provide the means to further investigate the feeding ecology of Borealopelta by summarizing the vegetation and local food options available. Census collections at five sites within the Grande Cache Mbr exposed in the Grande Cache Coal Mine reveal that the local vegetation there was dominated by conifers (44–70%) across all sites. Athrotaxites, Elatides, and Pityocladus were the most common conifers. Other gymnosperms present were ginkgophytes (e.g., Ginkgo, Ginkgoites; 11%) and Taeniopteris (9%). Caytoniales (Sagenopteris) were found at one study site but uncommon (2%). Ferns (e.g., Cladophlebis, Coniopteris, Gleichenites) accounted for 14% of the total site counts while cycadophytes (Bennettitales; 4%) and Equisetites (1%) were less common. When comparing the Gates Fm macroflora to the stomach contents of Borealopelta, these data suggest that B. markmitchelli was selectively feeding on ferns or in a recently disturbed fern-dense area within the local landscape.
... Macrofossil compressions and impressions and permineralized wood were organized and described by morphotypes following the method described by Peppe et al. (50). Each morphotype has a three-letter prefix (DSB or DSC) based on the name of the formation and the member from which they belong to, plus a number starting from one. ...
... A systematic affinity was proposed for each morphotype. Species names were not proposed for any of the morphotypes described because this required extensive research into the nomenclature of the taxon, previous fossil descriptions, and phylogenetic relationships (50), which were topics out of the scope of this paper. ...
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Andean uplift played a fundamental role in shaping South American climate and species distribution, but the relationship between the rise of the Andes, plant composition, and local climatic evolution is poorly known. We investigated the fossil record (pollen, leaves, and wood) from the Neogene of the Central Andean Plateau and documented the earliest evidence of a puna-like ecosystem in the Pliocene and a montane ecosystem without modern analogs in the Miocene. In contrast to regional climate model simulations, our climate inferences based on fossil data suggest wetter than modern precipitation conditions during the Pliocene, when the area was near modern elevations, and even wetter conditions during the Miocene, when the cordillera was around ~1700 meters above sea level. Our empirical data highlight the importance of the plant fossil record in studying past, present, and future climates and underscore the dynamic nature of high elevation ecosystems.
... The collected material was studied at the Geoscience Department at the Universidad de los Andes and it was separated and described by morphotypes following the method proposed by Peppe et al. (2008). A two-letter prefix (ES) was given to each morphotype based on the formation name plus a number. ...
Article
Movement toward our current climate state began in the middle Eocene to early Oligocene interval when the global temperature cooled and the first Antarctic ice sheet appeared. This dramatic climate change caused a significant global turnover in both marine and terrestrial biotas. The biotic response to this event at low latitudes remains mostly unexplored. Here, we studied a recently discovered Eocene fossil macro- and palynoflora from Esmeraldas Formation (Colombia). The Esmeraldas Flora consists of more than seven hundred macrofossil specimens found in two localities, including 15 morphotypes of leaves, seeds, cuticles, fruits, and flowers and > 5000 palynomorphs, that include 210 morphospecies. The Esmeraldas Formation is dominated by meandering river floodplain deposition, and was dated, using palynology and isotopic stratigraphy, as middle to late Eocene (~47.3 to ~33.9 Ma). Quantitative paleoclimatic calculations based on leaf physiognomy and coexistence analyses indicate a warm temperature and a seasonal precipitation within the range of modern tropical dry forests. Furthermore, the floristic composition that includes the presence of macrofossils of the Pterocarpus clade (Fabaceae), and pollen records of the subfamily Bombacoideae (Malvaceae), and Euphorbiaceae, could be indicative of a tropical dry forest. The overall paleobotanical record suggests that the Esmeraldas flora represents one of the earliest records of a tropical dry forest from low latitudes.
... Chemostratigraphical data of the Shapaja area, including section, sample labels, heights (m), CaCO 3 content (%), δ 13 C org values (‰, VPDB) and δ 13 C nod values (‰, VPDB). Fossil leaves were organized and described by morphotypes following the method proposed by Peppe et al. (2008). Each morphotype has a two-letter prefix (PZ) based on the formation name (Pozo Formation) plus a number starting from one. ...
Article
Since 2012, we have investigated a stratigraphic section encompassing the late Eocene–earliest Oligocene interval at Shapaja (Tarapoto area, Peruvian Amazonia, ca. 7°S), through paleontological and geological fieldwork. The measured sedimentary series (120 m-thick [West] plus 90 m-thick [East]), assigned to the upper member of the Pozo Formation, records fluvial micro-conglomeratic lenses intercalated with floodplain and evaporite-rich fine red deposits, estuarine/coastal-plain tidally-influenced fine sandstones, and oxbow lake nodule-rich blue clays. This sedimentary shift coincides locally with the demise of the large Eocene coastal-plain wetland known as Pozo System. The late Eocene–early Oligocene Shapaja section was extensively sampled for chemostratigraphy (δ13C on dispersed organic matter and pedogenic carbonate nodules), which in turn allowed for refining the location of the Eocene-Oligocene Transition (EOT) and other climatic events recognized at a global scale (i.e., Oi-1 and Oi-1a). The section has yielded nine fossil localities with plant remains (leaves, wood, charophytes, and palynomorphs), mollusks, decapods, and/or vertebrates (selachians, actinopterygians, lungfishes, amphibians, sauropsids, and mammals), documenting ~130 distinct taxa. Four localities of the upper member of the Pozo Formation at Shapaja predate the EOT, one is clearly within the EOT, while four are earliest/early Oligocene in age. The small leaf impressions found along the Shapaja section could be indicative of dry and/or seasonal conditions for this region throughout and after the EOT. Monkeys, indicative of tropical rainforest environments, are only recorded in a latest Eocene locality (TAR-21). Two biotic turnovers are perceptible in the selachian, metatherian, and rodent communities, well before the EOT [~35–36 Ma] and a few hundred thousand years after the EOT [~33 Ma]. The latter turnover seems to be primarily related to a global sea-level drop (ichthyofauna: marine-littoral elements replaced by obligate freshwater taxa) and/or the onset of a drier and more seasonal climate in early Oligocene times (terrestrial components). Changes in the structure of the Shapaja paleocommunities were mostly driven by the flexural subsidence during the late Eocene, and then globally driven by the earliest Oligocene climatic deterioration.
... The collected material was studied at the Geoscience Department at the Universidad de los Andes and it was separated and described by morphotypes following the method proposed by Peppe et al. (2008). A two-letter prefix (ES) was given to each morphotype based on the formation name plus a number. ...
... Based on the features observed when making these descriptions, the fossils from each locality 238 were divided into morphotypes (e.g., Ellis et al. 2009;Peppe et al. 2008) ...
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During the early Paleogene the Earth experienced long-term global warming punctuated by several short-term ‘hyperthermal’ events, the most pronounced of which is the Paleocene-Eocene Thermal Maximum (PETM). During this time, tropical climates expanded into extra-tropical areas potentially forming a wide band of ‘paratropical’ forests that are hypothesized to have expanded into the mid-latitude Northern Great Plains (NGP). Relatively little is known about these ‘paratropical’ floras, which would have extended across the Gulf Coastal Plain (GCP). This study assesses the preserved floras from the GCP in Central Texas before and after the PETM to define plant ecosystem changes associated with the hyperthermal event in this region. These floras suggest a high turnover rate, change in plant community composition, and uniform plant communities across the GCP at the Paleocene-Eocene boundary. Paleoecology and paleoclimate estimates from Central Texas PETM floras suggest a warm and wet environment, indicative of tropical seasonal forest to tropical rainforest biomes. Fossil evidence from the GCP combined with data from the NGP and modern tropics suggest that warming during the PETM helped create a ‘paratropical belt’ that extended into the mid-latitudes. Evaluating the response of plant communities to rapid global warming is important for understanding and preparing for current and future global warming and climate change.
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A new middle Cretaceous trilobed leaf, Araliaephyllum silvapinedae sp. nov., collected near the town of Cabullona, Sonora, Mexico, in La Cintura (Albian–Cenomanian) Formation, is described and identified through two comparative methods.: a leaf architecture analysis and the morphometric analysis of its shape. These allowed close comparison of the Cabullona material with extant and fossil taxa. The results of both the comparative methods demonstrate that the leaf of the new fossil plant is related to Araliaephyllum and Pabiania, the former being the one with which it shares most characteristics, both in leaf architecture and in shape. The analyses further confirm close morphological similarity between Araliaephyllum and Pabiania, as well as their relationship with Laurales, supporting the recognition of a new species for the Sonoran material.
Article
A new wood type for the Baja California Cretaceous adds to the plant diversity so far known for the area where gymnosperms seem to be dominant. It was collected near El Rosario, Baja California, from rocks of the Rosario Formation, in a sedimentary sequence that comprises ca. 1200 m of non-marine to deep marine sediments from Upper Campanian to Lower Danian age. The wood is characterized by having semiring porous growth rings, predominantly radial multiples of 2–7 with occasional clusters and some solitary vessels, simple perforation plates, alternate intervascular pits, oval to large elliptical vessel element-ray pits with reduced borders, septate thin-walled fibers, 1–4 seriate heterocellular rays, scares paratracheal, vasicentric and marginal parenchyma and oil cells associated with ray parenchyma. All these characters are found in Lauraceae, however, none of the extant taxa of the family have all these characters and even among fossil woods the characters in the Baja California material are better described only among the diverse Laurinoxylon, but vessel grouping, growth ring type, absence of marginal parenchyma, and slightly thicker rays suggest the presence of a new taxon, Rosarioxylon bajacaliforniensis Cevallos-Ferriz, Catharina & Kneller. By the end of the Cretaceous the family formed part of the plant community that represents a western extension of vegetation types more completely described from areas in the margins of the southern limits of the Western Interior Sea. The new taxon is proposed to highlight anatomical differences and geographic isolation from similar taxa and further suggests a large distribution of Lauraceae in what appears to be conifer dominated communities.
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The lower Miocene of Rusinga Island (Lake Victoria, Kenya) is best known for its vertebrate fossil assemblage but the multiple stratigraphic intervals with well-preserved fossil leaves have received much less attention. The Hiwegi Formation has three fossil leaf-rich intervals, which span the entire formation from oldest to youngest: Kiahera Hill, R5, and R3. Here, we describe new fossil collections from Kiahera Hill and R3 and compared these floras to previous work from R5, as well as modern African floras. The oldest flora at Kiahera Hill was most similar to modern tropical rainforests or tropical seasonal forests and reconstructed as a warm and wet, closed forest. This was followed by a relatively dry and open environment at R5, which was reconstructed as a woodland to open tropical seasonal forest. The youngest flora at R3 was most similar to modern tropical seasonal forests and was reconstructed as a warm and wet spatially heterogenous forest. Floral composition of all three floras differed, but the Kiahera Hill and R3 floras were more similar to each other than either flora was to the R5 flora. The Kiahera Hill flora had few monocots or herbaceous taxa, was dominated by large leaves, and had higher species richness and greater evenness than the R3 flora. Our work, coupled with previous studies, suggests that the R3 landscape consisted of both closed forest areas and open areas with seasonal ponding. The absence of morphotypes from the R5 flora that were present in the Kiahera Hill and R3 floras provides evidence for local extirpation during the R5 time interval. Thus, this work indicates that the Hiwegi Formation on Rusinga Island samples multiple environments ranging from more closed tropical forests to more open woodlands in the Early Miocene and provides important context for the evolution and habitat preference of early apes.
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The origins of South America’s exceptional plant diversity are poorly known from the fossil record. We report on unbiased quantitative collections of fossil floras from Laguna del Hunco (LH) and Río Pichileufú (RP) in Patagonia, Argentina. These sites represent a frost‐free humid biome in South American middle latitudes of the globally warm Eocene. At LH, from 4,303 identified specimens, we recognize 186 species of plant organs and 152 species of leaves. Adjusted for sample size, the LH flora is more diverse than comparable Eocene floras known from other continents. The RP flora shares several taxa with LH and appears to be as rich, although sampling is preliminary. The two floras were previously considered coeval. However, 40Ar/39Ar dating of three ash‐fall tuff beds in close stratigraphic association with the RP flora indicates an age of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $47.46\pm 0.05$ \end{document} Ma, 4.5 million years younger than LH, for which one tuff is reanalyzed here as \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $51.91\pm 0.22$ \end{document} Ma. Thus, diverse floral associations in Patagonia evolved by the Eocene, possibly in response to global warming, and were persistent and areally extensive. This suggests extraordinary richness at low latitudes via the latitudinal diversity gradient, corroborated by published palynological data from the Eocene of Colombia.
Article
Precise estimates of past temperatures are critical for understanding the evolution of organisms and the physical biosphere, and data from continental areas are an indispensable complement to the marine record of stable isotopes. Climate is considered to be a primary selective force on leaf morphology, and two widely used methods exist for estimating past mean annual temperatures from assemblages of fossil leaves. The first approach, Leaf Margin Analysis, is univariate, based on the positive correlation in modern forests between mean annual temperature and the proportion of species in a flora with untoothed leaf margins. The second approach, known as the Climate-Leaf Analysis Multivariate Program, is based on a modern data set that is multivariate. I argue here that the simpler, univariate approach will give paleotemperature estimates at least as precise as the multivariate method because (1) the temperature signal in the multivariate data set is dominated by the leaf-margin character; (2) the additional characters add minimal statistical precision and in practical use do not appear to improve the quality of the estimate; (3) the predictor samples in the univariate data set contain at least twice as many species as those in the multivariate data set; and (4) the presence of numerous sites in the multivariate data set that are both dry and extremely cold depresses temperature estimates for moist and nonfrigid paleofloras by about 2°C, unless the dry and cold sites are excluded from the predictor set. New data from Western Hemisphere forests are used to test the univariate and multivariate methods and to compare observed vs. predicted error distributions for temperature estimates as a function of species richness. Leaf Margin Analysis provides excellent estimates of mean annual temperature for nine floral samples. Estimated temperatures given by 16 floral subsamples are very close both to actual temperatures and to the estimates from the samples. Temperature estimates based on the multivariate data set for four of the subsamples were generally less accurate than the estimates from Leaf Margin Analysis. Leaf-margin data from 45 transect collections demonstrate that sampling of low-diversity floras at extremely local scales can result in biased leaf-margin percentages because species abundance patterns are uneven. For climate analysis, both modern and fossil floras should be sampled over an area sufficient to minimize this bias and to maximize recovered species richness within a given climate.