Lucas et al., 2023, Fossil Record 9. New Mexico Museum of Natural History and Science Bulletin 94.
107
FOSSIL VEGETATIONAL TRANSECT FROM BELOW THE COLCHESTER COAL TO 
THE ROOF OF THE CARDIFF (SURVANT) COAL (DESMOINESIAN, UPPER MIDDLE 
PENNSYLVANIAN), ILLINOIS BASIN
JOHN H. CALDER1, W. JOHN NELSON2, ARDEN R. BASHFORTH3, JACK WITTRY4, 
SCOTT D. ELRICK2 and WILLIAM A. DIMICHELE5
1Halifax, Nova Scotia, B3J 2L4, Canada, 2Illinois State Geological Survey, 615 E. Peabody Drive, Champaign, IL 61820 USA, 3Natural History 
Museum of Denmark, University of Copenhagen, 1718 Copenhagen K, Denmark, 4Field Museum of Natural History, Chicago, IL, 60605 USA, 
5Department of Paleobiology, NMNH Smithsonian Institution, Washington, DC 20560, USA email: dimichel@si.edu 
Abstract—Four collections of Middle Pennsylvanian plant fossils create an opportunity to examine a 
transect from below the Colchester Coal through the roof shale of the Cardiff (Survant) Coal of the Illinois 
Basin. The collections come from the Colchester Coal seat earth, the Colchester Coal roof shale (two 
collections), and the roof shale of the Cardiff Coal. The Colchester Coal is one of the most widespread 
coals in the American Pennsylvanian, extending from the Appalachian Basin (Lower Kittanning Coal) 
to the Midcontinent Region (Whitebreast and Croweburg coals). The Colchester Coal has been made 
famous by the fossilized plants and soft-bodied animals preserved in a facies of its roof shale, the Francis 
Creek Shale, host of the Mazon Creek biota. The collections reported here are much smaller than the 
Mazon Creek flora, and so represent local assemblages. The collection from the Cardiff Coal, which is 
no longer mined, is the first report of a flora associated with that coal bed. The three roof shale floras, 
collected in 1906, are small and likely were collected from the surface area at the mine tipple. They 
appear to represent the flora preserved close to the coal-bed surface and thus capture the final flora of 
the peat swamp. Accordingly, they represent the early phases of transition from a humid to a subhumid 
climate at the time of glacial melting and sea-level rise. Similarly, the Colchester Coal seat-earth collection 
likely represents a local landscape preserved during the time of climate change from a wet sub-humid 
to a humid climate, just preceding the onset of peat formation.
INTRODUCTION GEOLOGICAL AND HISTORICAL BACKGROUND
The middle of the Desmoinesian Stage, upper Middle The Colchester Coal originated as part of one of the most 
Pennsylvanian, in coal basins of the eastern and midwestern extensive peat deposits in geologic history. Although too thin to 
United States encompasses the most widespread and mine in many places, the Colchester occurs throughout the Illinois 
economically significant coal beds of the Pennsylvanian in the Basin, which covers much of Illinois, southwestern Indiana, and 
United States (Greb et al., 2003). These coal beds comprise parts western Kentucky. West of Illinois the Colchester correlates into 
of the first appearance of well developed cyclic sedimentation the Midcontinent Basin as the Whitebreast Coal of Iowa and the 
patterns recording the alternation of marine and terrestrial Croweburg Coal of Missouri, eastern Kansas, and northeastern 
strata (Wanless and Weller, 1932; Langenheim and Nelson, Oklahoma. Eastward, the Colchester is correlative with the 
1992; Cecil et al., 2014). This pattern begins with the so-called Lower Kittanning coal bed in the northern Appalachian Basin of 
Verdigris Cycle, which includes the Colchester Coal bed (Cecil eastern Ohio, western Pennsylvania, and parts of West Virginia. 
et al., 2003), the main object of this study. These correlations are based on biostratigraphy of spores in 
Cyclic sedimentation, as was recognized early (Wanless coal (Peppers, 1996) and conodonts in associated marine rocks 
and Shepard, 1936), reflects glacial fluctuations primarily in (Heckel, 2013), in addition to lithologic similarities. Cecil et al. 
the southern hemisphere, which also induced and were thus (2003) compared the paleoclimate of the Colchester Coal to its 
synchronized with changes in sea level and climate (Cecil et al., correlatives (including rocks that lack coal) from the northern 
1985; Cecil, 1990; Montañez et al., 2016). These oscillations Appalachian Basin as far west as California. 
were driven most likely by Earth orbital factors (Horton et al., In the southern part of the Illinois Basin the Colchester Coal 
2012). The resultant glaciations were not, however, equally is too thin to mine, ranging from a few cm to about 50 cm and 
intense, even if they followed a more-or-less regular temporal averaging around 20 to 30 cm. Directly overlying the coal is the 
rhythm (Heckel et al., 2007). Like modern glacial-interglacial Mecca Quarry Shale, which is black, highly fissile, phosphatic 
cycles, magnitude of sea-level changes varied, resulting in marine shale typically 50 to 75 cm thick (Fig. 1). Although thin, 
temporally variable thicknesses and extents of the resulting these units are readily recognized on most types of borehole 
strata (Heckel, 2008). logs. Thicker Colchester Coal is confined to the northern half 
In this study, we examine several local plant-fossil of Illinois where thickness is commonly 75 to 125 cm and the 
assemblages that come from different terrestrial phases of the coal was mined extensively from the middle 19th into the middle 
extensive glaciation that produced the Verdigris cyclothem and 20th century. The growth of heavy industry in the Chicago area 
the Colchester Coal, and the subsequent much less extensive spurred mining of the Colchester Coal, but gradually the thicker 
glaciation that includes the Survant Coal. Local occurrences coal deposits of southern Illinois came to prominence and the 
of the Survant, situated at the most landward fringes of its northern mines went out of production. 
development have been described by several different names Lying between the Colchester Coal and the Mecca Quarry 
over time, reflecting their limited and unconnected areal extents. Shale in much of northern Illinois is a gray, non-marine to 
Among these names was the Cardiff Coal, which is of secondary marginal marine shale unit called the Francis Creek Shale. 
interest here. The Colchester Coal is superseded by the Francis Thickness of the Francis Creek increases from zero on the south 
Creek Shale, which hosts the famous Mazon Creek biota, with and west to more than 25 m at the northeastern corner of the basin 
which these local assemblages can be contrasted. near Kankakee (Smith, 1970; Fig. 2). The Francis Creek Shale 
is famous for its “Mazon Creek” flora and fauna, including soft-
108
is: roadcut on west side of Scab Hollow Road approximately 
300 feet from north line and 1,200 feet from east line of Section 
24, T2N, R1W, on the Ray 7.5-minute topographic quadrangle. 
We sought this locality based on mention of plant fossils 
in a measured section here from Wanless (1957, p. 189). Field 
notes that H.R. Wanless made in 1930 (ISGS, open files) provide 
further information. Wanless identified “well preserved fern 
leaves, including Annularia sphenophylloides, Neuropteris 
rarinervis, Neuropteris sp., Odontopteris, Pecopteris sp., 
Cordaites, Calamites, etc. Collection made by Messrs. Milligan, 
Livingston, and Wanless”. We have not learned the disposition 
of the collection nor the identity of Livingston and Milligan. 
Possibly, they were students of Dr. Wanless. 
The section that Wanless described is shown graphically 
(Fig. 4). Plant fossils occur in the upper 1 to 2 feet (30 to 60 
cm) of gray, micaceous shale that becomes increasingly sandy 
downward and lies approximately 45 to 65 cm beneath the base 
of the Colchester Coal, which is approximately 1.5 feet (45 cm) 
thick at this site. Wanless interpreted the plant-bearing shale 
as the upper part of a channel phase of the unit then called the 
Isabel sandstone, now considered to be the Coxville Sandstone 
Member of the Carbondale Formation.
The plant-bearing siliciclastic bed beneath the Colchester 
Coal is a “seat earth” only in the broadest terms: it is a rock 
unit immediately below a coal bed. Rooting by the lycopsid root 
system, Stigmaria, is concentrated in the upper parts of the bed, 
almost certainly derived from the initial development of the 
Colchester peat swamp. A typical paleosol “underclay”, of the 
type that underlies the Colchester Coal in most of the Illinois 
FIGURE 1. Generalized stratigraphic section discussed in report Basin, was not noted either by Wanless or in the fieldnotes of the 
with approximate stratigraphic position of plant-fossil localities. authors (Nelson and DiMichele).
Minonk Mine: Colchester Coal Roof Shale
bodied invertebrates, preserved in siderite concretions (Wittry, David White, of the U.S. Geological Survey, acquired 
2012, 2020). In addition, the Francis Creek Shale contains a a collection (USGS collection 4146) from the Minonk Coal 
diverse flora preserved as compressions within the shale, and Company’s mine on August 27, 1906. Minonk is about 50 km 
locally the casts of flat-lying logs and stumps in growth position north of Bloomington in north-central Illinois (Fig. 3) and at the 
rooted at the top of the Colchester. Mainly because of difficulty time was a junction point for branches of the Illinois Central and 
in collecting, these fossils have received less attention than Santa Fe Railroads. A shaft 100 m (329 feet) deep was completed 
those of the Mazon Creek concretions. The low seam height in 1869 and production from the Danville Coal began, but this 
in underground mines made walking upright impossible; the operation proved unprofitable, so the company deepened the 
last deep mine closed more than 70 years ago. Surface mining shaft to 168 m (550 feet), where higher quality coal from the 
continued into the 2000s but collecting generally was confined Colchester Coal Member was available (Moore, 1913). More 
to random gathering of siderite nodules from spoil banks. than 1.9 million tons of coal were produced until 1902, when the 
A highly localized deposit of thick coal younger than the first mine was closed. Mine No. 2 commenced operation in 1905 
Colchester is known as the Cardiff Coal (Fig. 1). This coal was from shafts about 1 km north of the original portal and remained 
mined underground more than a century ago at the village of in production through 1951, at the time of closure being one of 
Cardiff in northeastern Illinois (Fig. 3) and later was extracted, the last underground mines in Illinois extracting the Colchester 
together with the Colchester, from a nearby surface mine. As Coal. Total output of Mine No. 2 was approximately 1.28 million 
detailed below, the Cardiff Coal apparently represents peat that tons, having had average annual production less than half that of 
accumulated in an abandoned stream channel. Plant fossils Mine No. 1. According to available maps, workings of the two 
(compressions) were collected from shale overlying the coal in a mines connected underground. 
mine at Cardiff but information on their precise geologic setting Like most mines in the Colchester Coal, both Minonk 
is not available. mines used the longwall system of coal extraction that evolved 
This article describes and illustrates plant fossils from three to maximize recovery from thin coal seams. Generally, the 
localities associated with the Colchester Coal and one with the mine layout was circular or semi-circular having haulage 
Cardiff Coal (Fig. 3). Two of the Colchester collections came roads radiating from the shafts to the working faces around the 
from the lower part of the Francis Creek Shale in underground perimeter. After setting wooden props and building walls of 
mines (Minonk and Spring Valley) and the third came from waste rock to protect roads and work areas, the miners removed 
shale a short distance below the Colchester exposed along a coal and as the face advanced, allowed overburden to subside 
county road (Scab Hollow). The Cardiff collection came from into the worked-out area. In this manner, more than 90% of the 
shale overlying the Cardiff Coal in an underground mine.  coal in place could be extracted. Most of the work was carried 
Scab Hollow Locality: Colchester Coal Seat Earth out by hand: undercutting the coal with a pick, drilling shot 
holes, blasting with explosives, and loading by shovel into cars 
This name refers to a flora collected by coauthors DiMichele pulled by mules or other animals. By contrast, the longwall 
and Nelson in July 1983 near Scab Hollow (USNM locality system of mining in use today is fully mechanized and uses 
38404), a ravine in Schuyler County, western Illinois (Fig. 3). massive hydraulic jacks to support the roof at the working face. 
We have not learned the origin of this peculiar name. Judging by No field notes from David White’s visit to Minonk have 
a field photograph and Google Earth imagery, the legal location 
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FIGURE 2. Thickness of Francis Creek Shale, from Korose (2003), with plant-fossil localities from this report.
come to light. We do not know whether he collected fossils Company operated five longwall underground mines in the 
underground or from waste piles on the surface. Geologists from Colchester Coal at Spring Valley, which lies about midway 
the Illinois State Geological Survey (ISGS) visited the Minonk between Joliet and the Quad Cities in northern Illinois (Fig. 3). 
No. 2 Mine on several occasions. In field notes from circa The No. 1 Mine opened in 1884, No. 2 following a year later 
1912, K.D. White reported, “The shale above the coal has many and operating until 1908 having produced more than 5.2 million 
plant impressions, mostly fern fronds. Also in the roof, up to a tons of coal. The city of Spring Valley was born with and grew 
height of 10 feet [3 m] there are many flattened trunks with the up around the mines. 
diamond patterned imprints on the surface. These were observed No field notes on the Spring Valley No. 2 Mine by David 
in places to be 12 inches [30 cm] wide, 1½ inches [4 cm] thick, White, H.F. Bain, or other geologists have been found.  J.A. 
and as long as 10 feet [3 m]. One vertical stem 6 inches [15 cm] Udden, however, then working for the ISGS, went underground 
in diameter was observed in place, the others being horizontal at spring Valley No. 1. His fieldnotes state that the coal averaged 
or nearly so.” 1.1 m (3.5 feet) thick and contained partings of pyrite and 
Spring Valley No. 2 Mine: Colchester Coal Roof Shale “bone”. The roof was hard gray shale as thick as 6 m (20 feet) having thin “draw slate” at the base, whereas the floor consisted 
A plant-fossil collection (USGS 4149) was made by of fire clay, grading down to sandstone. 
David White and H. Foster Bain, the latter from the ISGS, on In the Spring Valley No. 5 Mine, bordering No. 2 on the 
August 17, 1906, at an unnamed mine operated by the Spring northeast, Gilbert Cady (ISGS) reported that the coal varied 
Valley Coal Company, noted in the USGS collection records from 73 to 122 cm (2.4 to 4.0 feet) thick, and the “soapstone” 
as operating near LaSalle, Illinois. The Spring Valley Coal roof thinned toward the northeast, where black shale (Mecca 
110
FIGURE 4. Graphic section of Scab Hollow plant-fossil locality 
as described in field notes of H.R. Wanless, 1930 (ISGS field 
notes archive).
first. Production grew until in September 1912 when the Wabash 
Railroad canceled its contract with Cardiff claiming that coal 
quality had declined and was no longer suitable as fuel for steam 
locomotives. Thus, Mine No. 2 closed, people moved away, 
FIGURE 3. Map of Illinois showing plant-fossil localities and most of the buildings in town were dismantled and moved 
discussed in this report. (Ridings, 2008). Given the timing, White and Bain obtained their collection from Cardiff’s Mine No. 2. 
Quarry) came close to the top of the coal. In notes dated 1912, As with the other sites from this time, no field notes of 
K.D. White (ISGS) stated the gray shale varied up to 9 m (0 to White and Bain are on file for the Cardiff Mine. Considering 
30 feet) thick, with about 3 m (10 feet) of black shale containing that their Cardiff and Spring Valley collections carry the same 
limestone and ironstone concretions (again, Mecca Quarry dates, most likely they gathered fossils from waste piles on the 
Shale). Neither Cady nor White mentioned plant fossils, which surface and did not go underground. 
almost certainly occurred in the gray Francis Creek Shale and The two mines extracted both the Colchester Coal and the 
not the black Mecca Quarry Shale. younger, lenticular seam that came to be called the Cardiff Coal. 
Cardiff Mine: Cardiff/Survant Coal Roof Shale Cady (1915, p. 35) provided a map and three cross sections (Fig. 5) and described the Cardiff Coal as follows: “…a thick, 
David White and H. Foster Bain collected plant fossils lenticular bed of coal which seems to have been deposited in a 
(USGS collection 4150) on August 17, 1906, from the Cardiff small channel-like basin running in a quarter circle for about 
Coal Company’s mine at Cardiff, Illinois. This is the same day two miles [3.2 km], with a breadth of 1000 to 1200 feet [300 to 
on which they collected at the Spring Valley Mine noted above. 420 m]. At the bottom of this trough this coal (the ‘big vein’) 
Now a ghost town, Cardiff was situated in Livingston County, lies a few feet, as a rule not over 10 [3 m], above coal No. 2 
northeastern Illinois about 30 km west of Kankakee. [Colchester]; at a few points the beds are in contact. The bottom 
Coal was discovered at Cardiff (probably by drilling), a of the coal rises to a height of 15 [4.5 m] to over 30 feet [9 m] 
shaft was sunk, and production began in September 1899. The above coal No. 2 at the sides of the trough. Twelve feet [3.6 m] 
town that blossomed around the mine was named for the city in of coal has been encountered, but the average thickness in the 
Wales, long known for its collieries. Within four years the mine trough is about 9 feet [2.7 m].”
employed 400 workers and Cardiff’s population grew to 2,000. Coal having the same characteristics was encountered 
Then in March of 1903 a series of explosions (probably of in 1958 in Peabody Coal Company’s Northern Mine, Pit 15, 
methane gas and/or coal dust) ripped through the underground a surface mine about 11 km north-northeast of Cardiff (ISGS 
workings, killing nine workers and injuring 16 more. The Cardiff field notes; Smith, 1970). Whether the Cardiff and Clarke 
Coal Company then sealed the shafts and opened a new mine, City deposits are continuous has not been determined. At both 
Cardiff Coal Company No. 2, less than 1 km northwest of the localities the Cardiff coal body is crescent-shaped and concave 
111
FIGURE 5. Maps and cross sections modified from Cady (1915, Plate V) showing configuration of Cardiff Coal in the mines at 
Cardiff, Illinois.
upward in cross section. Interbeds of shale and claystone are “hand-sample = quadrat” method of Pfefferkorn et al. (1975). 
numerous. In places the coal terminates abruptly at its margins, At the time these quantifications were carried out, each hand 
elsewhere it interfingers and grades laterally to shale. sample, both sides together, were treated as a single quadrat. 
A columnar section (Fig. 6) for the Cardiff area was Identical areas of Part-Counterpart faces were counted only 
assembled using drilling records from the Cardiff Coal Company. once. On each quadrat, the occurrence of a taxon was noted 
As interpreted by Nelson et al. (2022a), the Cardiff coal is the once, regardless of how many individual specimens of that taxon 
Wheeler or lower Survant Coal Member and represents peat that were present. This method adjusts for the great size differences 
accumulated in one or more channel-form depressions. That among plant remains in a typical Pennsylvanian-age wetland 
conclusion agrees with Peppers (1970, p. 49), who examined flora. For example, recalling that the objective is an estimate of 
fossil spores from Cardiff and concluded, “The Cardiff Coal is biomass, how many marattialean-fern pinnules can be taken to 
interpreted as an earlier abandoned channel phase of deposition be equivalent to a fragment of a Lepidodendron trunk? Because, 
of the Lowell [Survant] Coal. It may actually be a little older hypothetically, every taxon or recognized object could be 
than the Lowell Coal of other parts of the Illinois Basin present on every quadrat, the resulting data reflect commonness 
because the spore assemblage has some aspects of the No. 2 not relative abundance (i.e., the method produces frequency 
[Colchester] Coal assemblage.” Also interpreted as Survant data). In practice, however, the method preserves rank-order 
equivalents are the Kerton Creek and Roodhouse coal beds of abundance and generally reflects absolute abundance. As 
western Illinois (Nelson et al., 2022b, 2022c). The Survant Coal shown by Wing and DiMichele (1995), this method tends to 
occurs extensively in the deeper part of the Illinois Basin but underestimate, within the context of an assemblage, the relative 
was not deposited outside of local depressions on the northern commonness of the more common forms and overestimate the 
and western shelves of the basin where regional subsidence was relative commonness of the rarer forms. 
slower. Frequencies of taxonomic or recognized-object occurrence 
QUANTITATIVE ANALYSIS OF THE FLORAS were normalized by being expressed as a percentage occurrence relative to the total number of quadrats examined.  The additive 
Methods percentages of all recognized categories, however, will not add 
The floras analyzed in this study were quantified using the up to 100% because of the above-mentioned characteristics of 
112
FIGURE 6. Generalized section in Cardiff area, northeastern Livingston County, Illinois, based on a composite of drilling records, 
interpreted by Nelson et al. (2022a).
113
the sampling process. Nonetheless, they preserve the basic rank The two Colchester Coal roof-shale assemblages also are 
order of the objects recognized and can be shown in dominance- very similar. Both are more diverse than either of the other 
diversity graphs. two assemblages, despite each being considerably smaller 
The counts were performed by two different individuals. than the Colchester Coal seat-earth collection. Dominance in 
Calder examined the Colchester seat-earth collection (USNM both collections also is lower with a longer tail of less frequent 
38404), one of the Colchester roof-shale collections (USGS taxa. In both cases, the arboreous lycopsid Synchysidendron 
4146), and the Cardiff roof-shale collection (USGS 4150). andrewsii is either the most frequently encountered taxon 
DiMichele examined one of the Colchester roof-shale collections or just slightly below that position. Both collections also 
(USGS 4149). Furthermore, Bashforth reassessed the taxonomic contain small numbers of lycopsid remains attributable to 
composition of the three roof-shale collections and Wittry Diaphorodendron cf. rimosum. Together these species constitute 
reassessed the Cardiff roof-shale flora. the Diaphorodendraceae (sensu DiMichele and Bateman, 
Results of Quantitative Analyses 1996), thus, as a group, the most frequently encountered in the assemblages. Illinois State Geological Survey fieldnotes, taken 
The results of the quantitative analyses are presented in at the time of active mining at the Spring Valley mine (USGS 
Table 1. For each taxon or object category, this table shows both 4149), make note of the abundance of large lycopsid trunks in 
the raw frequencies (the count data itself) and the corresponding the roof shale. Other elements in these floras include various 
percentage of the sample that frequency entails. The table also calamitalean remains, Sphenophyllum, tree-fern foliage, and 
shows the reranking of the taxa from most to least frequent, not other pteridosperms, such as Macroneuropteris scheuchzeri and 
including axes, seeds, or roots; due to uncertainties caused by Laveineopteris rarinervis.
preservation, some of the categories in fact may be duplicates, 
lowering overall diversity. Dominance-diversity curves based FLORISTICS
on the rankings and frequencis in Table 1 for each of the four Selected elements of the floras are shown in Figures 8 - 20. 
samples are presented in Figure 7. They are described below beginning with the stratigraphically 
Possibly the most interesting result of these analyses is the lowest of the assemblages, the Colchester Coal seat earth flora 
similarity of the Colchester Coal seat-earth flora (USNM 38404) from the Scab Hollow location, proceeding to the two Colchester 
to the Cardiff Coal roof-shale flora. Both are dominated to a Coal roof shale collections, and ending with the Cardiff Coal 
relatively high degree by species of Neuropteris, N. ovata in the roof shale collection.
seat-earth assemblage and N. vermicularis in the Cardiff flora. 
Both assemblages also contain small proportions of marattialean Colchester Coal Seat Earth, Scab Hollow (USNM 38404)
fern foliage and only single occurrences of aerial arboreous The flora at Scab Hollow (Fig. 8 a) was described initially 
lycopsid remains. Laveineopteris rarinervis occurs in all four by Wanless (1957). It was preserved in a fine sandstone, that 
collections. The rarity of some of the remains more common in grades upward into a hard silty clay, reflecting pedogenesis in 
the Colchester Coal roof shale may reflect the small size of the its upper portion. The upper part of the deposit was heavily 
Cardiff sample. penetrated by stigmarian rooting systems (Fig. 8 b-d) that 
FIGURE 7. Dominance-Diversity curves for the collections discussed herein. Data on Frequency is derived from Table 1. a, USNM 
38404, Colchester Coal seat earth, Scab Hollow locality. b, USGS 4146. Colchester coal roof shale, Minonk Mine. c, USGS 4149, 
Colchester Coal roof shale, Spring Valley No. 2 Mine. d, USGS 4150. Cardiff Coal roof shale, Cardiff Mine.
114
TABLE 1. Quantitative analyses of Colchester and Cardiff coal macrofloras.
Cardiff Coal roof shale (Cardiff Mine) USGS 4150
Quadrats 31
TAXA Frequency Percentage
Neuropteris vermicularis 19 61.29
Neuropteris ovata 10 32.26
Cyclopteris spp. 4 12.90
Laveineopteris rarinervis 3 9.68
Neuropteris sp. 2 6.45
"Pecopteris" cf. cyathea 2 6.45
Diaphorodendron sp. 1 3.23
Macroneuropteris macrophylla 1 3.23
Crenulopteris sp. 1 3.23
Senftenbergia plumosa 1 3.23
Seeds 1 3.23
cf. Small fern 1 3.23
Medullosan axes numerous
Colchester Coal roof shale (Spring Valley) USGS 4149
Quadrats 43
TAXA Frequency Percentage
Calamitalean tissue sheets 12 27.91
Synchysidendron andrewsii 9 20.93
striate axes 8 18.60
Crenulopteris cf. acadica 6 13.95
Marattialean foliage sp. 6 13.95
Diaphorodendron cf. rimosum 3 6.98
Annularia sp. 3 6.98
Sphenophyllum emarginatum 3 6.98
Alethopteris serlii 3 6.98
Crenulopteris cf. subcrenulata 2 4.65
cf. Neuropteris anomala 2 4.65
Pteridosperm foliage 2 4.65
Lepidodendrid indeterminate 1 2.33
Sphenophyllum cf. oblongifolium 1 2.33
Calamites sp. 1 2.33
Macroneuropteris cf. scheuchzeri 1 2.33
Lavineopteris rarinervis 1 2.33
comminuted plant debris 1 2.33
bivalves 3 6.98
snails 1 2.33
charcoal 2 4.65
115
TABLE 1 (continued). Quantitative analyses of Colchester and Cardiff coal macrofloras.
Colchester Coal roof shale (Minonk Mine) USGS 4146
Quadrats 71
TAXA Frequency Percentage
Synchysidendron andrewsii 21 29.58
Oligocarpia/Mariopteris 11 15.49
Lepidodendrid indeterminate 9 12.68
Diaphorodendron cf. rimosum 5 7.04
Macroneuropteris scheuchzeri 4 5.63
Laveineopteris rarinervis 4 5.63
Senftenbergia plumosa 2 2.82
Sphenophyllum sp. 2 2.82
Marattialean foliage 2 2.82
Lepidodendron cf. aculeatum 2 2.82
cf. Lepidodendron mannabachense 1 1.41
Bergeria sp. 1 1.41
Annularia radiata 1 1.41
Sphenophyllum emarginatum 1 1.41
Crenulopteris cf. subcrenulata 1 1.41
Sphenopteris sp. 1 1.41
Seeds 1 1.41
Medullosan axes numerous
Lepidophylloides sp. numerous
Dunbarella (pectinacean bivalve) 2 2.82
Colchester Coal seat earth (Scab Hollow) USNM 38404
Quadrats 121
TAXA Frequency Percentage
Neuropteris ovata 103 85.12
“Pecopteris” cf. cyathea 12 9.92
Crenulopteris acadica 6 4.95
Cyclopteris fimbriata 5 4.13
Calamites spp. 4 2.48
Lepidophylloides sp. 1 0.83
Stigmaria ficoides 1 0.83
Laveineopteris rarinervis 1 0.83
Medullosan axes numerous
Stigmarian rootlets numerous
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FIGURE 8. USNM 38404. Colchester Coal seat earth (Scab Hollow). a, Roadside ditch collection location. USNM locality 38404, 
July 6, 1983. b, Stigmarian rhizomorph with attached rootlets USNM 787712. c, Closeup, 2X magnification increase, of stigmarian 
axis with attached rootlets. Rootlet attachment points are vague but can be identified on the axis. d, Stigmarian rootlets penetrating 
downward in seat-earth matrix. USNM 787711. e, Stigmarian rootlets penetrating downward in seat-earth matrix. USNM 787710. 
Scale bar in (c) = 1 cm. Scale bars in (b, d, e) = 2 cm (1/2 X at published plate size - 18.4 cm width).
diminished downward in the deposit. be cyatheoid, that is with lateral veins dichotomized no more 
The taxonomic composition changed through the 1 m than once; whether all or some are dichotomized is one of the 
thickness of the deposit that was excavated. In the lower parts, characteristic traits on which species of this group are separated. 
plant remains were sparse and comprised primarily axes, In addition, the apparent lack of marginal pinnule lobation also 
including striate axes typical of calamitalean stems (Fig. 9 weighs against a lobate-marattialean affinity.
a-c), pteridosperms, and marattialean ferns. The Calamites Neuropteris ovata nearly entirely dominates the middle part 
stems were preserved mainly as sandstone-filled stem casts, a of the deposit and also occurs frequently in the upper portions. 
preservation type commonly referred to as “pith casts” but that, The plant remains (Fig. 10) are relatively well preserved and 
in nearly all instances, are casts of stems (see DiMichele and occur in considerable abundance where present. In addition, 
Falcon-Lang, 2012; Falcon-Lang, 2015; the cited papers discuss the foliage is commonly intermixed with fine roots typical 
the pith-cast explanation in detail). Rare remains of tree-fern of pteridosperms and calamitaleans (Fig. 10 c). The N. ovata 
foliage also were found. In his examination of the site in 1930, specimens are typical of this species. Pinnules are basipetally 
H.R. Wanless noted the presence of Annularia sphenophylloides auriculate and acropetally somewhat incised, having a relatively 
among the plant remains; we did not encounter any calamitalean weak midvein that extends through about 2/3 of the pinnule 
foliage in the collection. length, flanked by thin, dense, arching lateral veins, straight 
The upper parts of the deposit were the richest in marattialean to slightly curved lateral margins, and a blunt and broadly 
tree-fern foliage, attributable to Crenulopteris acadica (Wittry et rounded apex. In more distal parts of pinnae, secondary veins 
al., 2015), a lobate form of tree-fern foliage (Fig.9 d-e). In these can be found entering directly from the rachis on both sides of 
plants, pinnule shape varies systematically through the large the midvein. There is considerable variation in pinnule size, 
fronds, and are associated with characteristic forms of pinnule but the basic characteristics are consistent. In addition, where 
venation and lobing (Wagner, 1959). This foliage type has long pinna apices are preserved (Fig. 10 a - c), apical pinnules are 
been characterized as Lobatopteris vestita, a form of foliage bluntly rounded and not notably inflated or constricted, and the 
that includes a number of species within the genus Lobatopteris lateral pinnules are increasingly fused to one another and to the 
(Wagner, 1959). The introduction of the genus Crenulopteris apical pinnule. Associated with these pinnules is a cyclopterid, 
by Wittry et al. (2015) challenged lobatopterid taxonomy, and a Cyclopteris fimbriata (Fig. 10 d), that is part of the N. ovata 
response can be found in Wagner and Álvarez-Vázquez (2016). frond.
Crenulopteris acadica is found most commonly in the later part It is possible that other neuropterids are present as rare 
of the Middle Pennsylvanian, consistent with its occurrence elements in the assemblage. The specimen illustrated in Figure 10 
here. f, shown at the same magnification of that in Figure 10 e, is much 
There may be other tree-fern species present, but poor larger than pinnules of most of the N. ovata specimens, lacks 
preservation hampers identification. The specimen illustrated an auricle and has a tapering apical region. The identity of this 
in Figure 9 f is one of the better preserved examples of these particular specimen is uncertain. Wanless, in his aforementioned 
questionable specimens. Although venation is unclear, it could 1930 field notes, also recorded the presence of “Neuropteris” 
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FIGURE 9. USNM 38404. Colchester Coal seat earth (Scab Hollow). Pteridophytes. a - b, Opposite sides of calamitalean stem cast 
from sandstone portion of seat earth. This specimen is not a “pith cast” (see discussion of this form of preservation in DiMichele 
and Falcon-Lang, 2012; Falcon-Lang, 2015). USNM 787708. c, Calamitalean stem cast. USNM 787707. d, Crenulopteris acadica 
(Lobatopteris vestita) lobate marattialean fern foliage. USNM 543927. e, Crenulopteris acadica (Lobatopteris vestita) lobate 
marattialean fern foliage. USNM 543926. f, Marattialean foliage, possibly “Pecopteris” cyathea or a member of the cyathea group. 
Lateral venation is not clear but may be once bifurcate, and there is no evidence of marginal lobing. USNM 787704. Scale bars = 
1 cm.
(now Laveineopteris) rarinervis and Odontopteris sp. We found 1985). Coal balls are rare in the Colchester Coal, and in those 
no indication of Odontopteris and note that in certain parts of the we have examined the peat is too poorly preserved to identify 
frond, particularly near the apex of pinnae, N. ovata pinnules can the plant composition. In addition, it can be quite difficult to 
be broadly attached, lack a midvein, and be partially fused to one distinguish flattened striate axes of pteridosperms and ferns, 
another and the apical pinnules, thus appearing much like a form wherein the striae are strands of supportive sclerenchyma cells, 
of Odontopteris. As noted below, Laveineopteris rarinervis was from cordaitalean leaves, wherein the striae are mostly bundles of 
identified in the Colchester Coal roof-shale collections analyzed vascular tissue (leaf veins). There were, in our collection, striate 
here, so its presence in this collection is not unexpected. axis-or-leaf remains that could not be classified unequivocally 
As a final note, Wanless recorded the presence of Cordaites. as cordaitalean leaves. Consequently, Wanless’ identification 
Cordaitalean gymnosperms are a common, if not dominant, would not be atypical for a wetland flora of this time period, but 
element in coal balls, thus of the coal-swamp floras themselves, it also cannot be affirmed.
from coals older and younger than the Colchester (Phillips et al., 
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FIGURE 10. USNM 38404. Colchester Coal seat earth (Scab Hollow). Pteridosperms. a, Neuropteris ovata pinna tip. USNM 
787720. b, Neuropteris ovata pinna. USNM 787718. c, Neuropteris ovata litter of various sizes (from different parts of the frond), 
mixed with fine roots of pteridosperm or calamitalean origin. USNM 787719. d, Cyclopteris fimbriata, cyclopterid pinnule of N. 
ovata. USNM 787706. e, Neuropteris ovata pinna. USNM 787717. f, Neuropterid pinnule, possibly a large N. ovata pinnule. USNM 
787720. In all images: arrows point to areas of suspected arthropod damage. Scale bars = 1 cm.
Colchester Coal Roof Shale, Minonk Mine (USGS 4146) Oligocarpia or Mariopteris. Other elements are rare, but include 
The collection from the Minonk Mine (USGS 4146) is the the spectrum of typical wetland plants, including pteridosperms, 
larger of the two USGS Colchester Coal roof shale collections, calamitaleans, marattialean tree ferns, and groundcover plants, 
consisting of 71 non-empty quadrats. The flora is dominated by Sphenophyllum and small ferns.
lycopsids, consistent with the observations of ISGS geologist Most of the collected lycopsid remains can be attributed to 
K.D. White, who noted when visiting the Minonk Mine that “... Synchysidendron andrewsii (Fig, 11 a-e) and Diaphorodendron 
in the roof, up to a height of 10 feet [3 m] there are many flattened cf. rimosum (Fig. 11 f-g). Both genera are characterized by 
trunks with the diamond patterned imprints on the surface.” deciduous-lateral branch architecture (DiMichele et al., 2013). 
Second in abundance is a fern-like plant that may be either Leaf cushions of Synchysidendron protrude more from the stem surface than those of Diaphorodendron. Synchysidendron leaf 
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FIGURE 11. USGS 4146. Colchester Coal roof shale (Minonk Mine). Lycopsids. Diaphorodendraceae. a, Synchysidendron andrewsii. 
USNM 787801. b, Synchysidendron andrewsii USNM 787799. c, Synchysidendron andrewsii USNM 787798. d, Enlargement of 
image (c). e, Synchysidendron andrewsii USNM 787803. f. Diaphorodendron cf. rimosum USNM 787807. g, Diaphorodendron cf. 
rimosum USNM 787806. Scale bars = 1 cm.
cushions also change shape from larger diameter branches, c-d re-illustrates the specimen in the other orientation for direct 
where they are much longer than wide, to the smaller branches, comparison) suggesting an affinity with Lepidophloios, possibly 
where they approach equidimensional in height and width. L. acerosus; this identification seems unlikely given the position 
Diaphorodendron leaf cushions, in contrast, remain narrow and of what may be infrafoliar parichnos strands (Fig. 13 d, arrows) 
elongate on branches of all diameters. Other kinds of lycopsids and the location of extensive plications above the leaf scar in the 
also are present. One form, Figure 12, is a form of Lepidodendron Lepidophloios orientation (Fig. 13 a-b), but must be considered.
sensu stricto (DiMichele, 1983), possibly L. aculeatum, with Small numbers of marattialean fern remains were 
curved tails, lower keel folds, a relatively small leaf scar, encountered in the collection. The name Pecopteris, long used 
and sub-leaf-scar infrafoliar parichnos. These specimens are for marattialean sterile foliage, is an invalid name as applied to 
somewhat more rounded than typical of the species and lack that group; the type species of Pecopteris belongs to a different 
so-called lateral lines, running in downward arcs from the group of ferns (see Cleal, 2015). The USGS 4146 specimens 
edges of the leaf scar, so the L. aculeatum identification must are difficult to identify with confidence; they are similar to 
remain speculative. One specimen has leaf cushions with nearly “Pecopteris” cyathea or “Pecopteris” oreopteridia (Fig. 14 a-b) 
equal height and width (Fig. 12 c-d). The upper angle of the in being approximately twice as long as wide, with midveins 
leaf cushions on this specimen is sharply angular, whereas the that are inserted orthogonally on the rachis, and lateral veins that 
lower angle is rounded. There are wrinkles in the lower portion, fork once once or are unforked. Due to the state of preservation 
below the leaf scar, possibly due to compression given that and the small size of the remains, certain identification is not 
these leaf cushions appear to be rather thick and protuberant. possible. The specimen illustrated in Figure 14c, preserved in a 
There may be infrafoliar parichnos beneath the distinctive, siderite concretion, is similar to Crenulopteris cf. subcrenulata. 
protuberant leaf scar. Rare specimens (Fig. 12e) with attached Its pinnules are deeply lobed and might be described as a pinna 
leaves and obscure leaf cushions, typical of specimens with still bearing small, rounded pinnules with typically lobatopterid, 
attached and somewhat adpressed leaves, may be attributable candelabra-type venation (Fig. 14d). 
to Bergeria, or simply be a branch of one of the other forms Sphenopsid remains, also rare, are represented by both 
(Thomas and Cleal, 2022). Figure 13 shows the same specimen calamitaleans and sphenophyllaleans. Rare foliage is tentatively 
illustrated in Figure 12 c-d, but inverted (Fig. 13 a-b; Fig. 13 assigned to Annularia radiata (Fig. 15a), given its relatively 
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FIGURE 12. USGS 4146. Colchester Coal roof shale (Minonk Mine). Lycopsids. a, Lepidodendron cf. aculeatum. USNM 787811. 
b, Lepidodendron cf. aculeatum. USNM 787805. c, cf. Lepidodendron mannabachense, USNM 787808. d, Higher magnification 
of parts of specimen in image (c). White arrows point to what possibly are infrafoliar parichnos. See also Figure 13, which also 
examines the possibility that this specimen is a species of Lepidophloios. e, Bergeria sp. (Paralycopodites-type) with attached 
leaves. USNM 787810. Scale bars = 1 cm.
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FIGURE 13. USGS 4146. Colchester Coal roof shale (Minonk Mine). This plate represents two views of the specimen illustrated in 
Figure 12, demonstrating the possibility that this specimen is a species of Lepidophloios rather than Lepidodendron. In the rotated 
views of images (a) and (b) the specimen bears some resemblance to Lepidophloios acerosus. Scale bars = 1 cm.
narrow, straight-sided leaves and acuminate leaf apices. is a single specimen of the small fern cf. Senftenbergia plumosa 
Sphenophylls, which constitute some of the rare groundcover (Fig. 16d/upper bracket). This latter foliage fragment has short, 
components of the flora, are assignable to Sphenophyllum falcate pinnules of triangular shape with an acuminate apex. A 
emarginatum (Fig. 15 b-c). midvein is well marked and proceeds from the pinnule base to 
Additional small groundcover plants were rare but include the apex. Lateral veins are sparse, dichotomize at least one time, 
unidentified sphenopterid-fern remains that appear to bear and are borne at approximately 45°.
pinnule-margin sporangia (Fig. 15d). Also tentatively identified Another possible fern is part of a complex of plants that 
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FIGURE 14. USGS 4146. Colchester Coal roof shale (Minonk Mine). Marattialean ferns. a, Cyatheoid marattialean foliage, possibly 
“Pecopteris” cyathea or “Pecopteris” oreopteridia. USNM 787792. b, Cyatheoid marattialean foliage, possibly “Pecopteris” 
cyathea or “Pecopteris” oreopteridia. USNM 787791. c, Crenulopteris cf. subcrenulata USNM 787789. d, Enlargement of right-
side basal portion of image (c) showing lobate pinna margins and lobatopterid venation. Scale bars = 1 cm.
proved difficult to identify to species, and may represent more The basal basiscopic pinnule is more triangular and enlarged 
than one group, artificially combined in Table 1 as Oligocarpia/ with a slightly constricted base. A midvein is present through 
Mariopteris. This group includes what we think might be the true about 2/3 of the pinnule length and lateral veins are thick and 
fern Oligocarpia leptophylla (Fig. 15 e-f), which has elongate, coarse. Progressively along the ultimate pinna the pinnules 
largely straight-sided pinnules with bluntly triangular apices. A become fused to those adjacent. Overall, were these pinnules 
midvein is weakly developed and lateral veins are ascendent and larger, the specimens would bear comparison with Mariopteris 
dichotomizing. The basiscopic basal pinnule, sometimes two, cf. nervosa, a seed plant.
of each pinna are rounded with a slightly undulatory margin. Two seed plants in the flora are attributable to the 
Another form of foliage that we have lumped into this group Medullosales, Macroneuropteris scheuchzeri (Fig. 16 a-b) 
is shown in Figure 15 g-h. In such specimens, the pinnules are and Laveineopteris rarinervis (Figs. 15e, 16e). The former is 
more rounded than elongate, but with an undulatory margin and recognizable by its large size, thin but well marked midvein, 
a bluntly convergent apex, and fused together in the apical parts and fine, arching lateral venation. Most distinctively, however, 
of the ultimate pinnae in the terminal portion of the penultimate are the “hairs” that mark its surface, which Laveine and Oudoire 
pinna. The pinnules are generally more uniform in shape than (2015) showed to be subepidermal resin ducts. Laveinopteris 
in Figure 15 e-f, although the basalmost pinnules of a pinna rarinervis, a common late Middle Pennsylvanian species, is 
are likewise enlarged compared to the more distal pinnules. As characterized by generally small pinnules that are strongly 
seen especially in Figure 15h the penultimate rachis is relatively adherent to the rachis, with straight sides, a rounded apex, strong 
thin and flexuous, leading us to conclude that this is likely a midvein, and sparse but robust lateral venation (Cleal and Shute, 
fern rather than a pteridosperm, possibly Oligocarpia gutbieri. 2003). A single seed was found in the collection (Fig. 16e); it is 
Additional specimens of this complex are illustrated in Figure round and may be platyspermic, but otherwise lacks identifiable 
16 c-d/lower bracket. These specimens are intermediate in features. 
form between the others illustrated in having robust, straight, Among animal remains in the collection were pectenoid 
penultimate pinna rachises. The pinnules are uniformly short and bivalves. One of these is illustrated in Figure 16f.
rounded with undulate margins but with bluntly pointed apices. 
FIGURE 15 (facing page). USGS 4146. Colchester Coal roof shale (Minonk Mine). a, Annularia radiata USNM 787784. b, 
Sphenophyllum emarginatum USNM 787786. c, Sphenophyllum emarginatum, longitudinally preserved axis USNM 787785. d, 
Unidentified fertile sphenopterid fern with marginally borne sporangia on pinnules. USNM 787788. e, Oligocarpia leptophylla 
USNM 787787 counterpart. f, Oligocarpia leptophylla USNM 787787 part; note Laveineopteris rarinervis pinnules, upper left of 
image. g, Oligocarpia cf. mixta, Mariopteris cf. nervosa, or possibly Senftenbergia plumosa; compare with Figure 16 c, d, perhaps 
reflective of intraspecific, even intra-frond, variation. USNM 787790. h, Enlargement of lower portion of image (g), showing 
sinuousness of the rachis, sparseness of the venation, and lobate pinnule margins. Scale bars = 1 cm.
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FIGURE 16. USGS 4146. Colchester Coal roof shale (Minonk Mine). Seed plants. a, Macroneuropteris scheuchzeri. Arrows point 
to areas with subcutaneous resin canals (“hairs”). USNM 787782. b, Macroneuropteris scheuchzeri. Arrows point to areas with 
subcutaneous resin canals (“hairs”). USNM 787783. c, Mariopteris cf. nervosa USNM 78794. d, cf. Senftenbergia plumosa (upper 
bracket) and Mariopteris cf. nervosa (lower bracket) USNM 78793. e, Seed (arrow) and cf. Laveineopteris rarinervis USNM 
787795. f, Dunbarella (pectinacean bivalve) USNM 787796. Scale bars = 1 cm.
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Colchester Coal Roof Shale, Spring Valley Mine (USGS of the elongate, obovate shape of the pinnules with bluntly 
4149) pointed tips, somewhat constricted bases, and dense lateral 
The collection from the Spring Valley Mine, USGS 4149, veins strongly orthogonal to the midvein, the latter extending 
is about half the size of the other Colchester Coal roof-shale almost to the pinnule apex. A number of unusual pteridosperm 
collection from the Minonk Mine (USGS 4146). Both roof shale foliage specimens or fragments were found that are not clearly 
collections are more diverse than the seat-earth collection from identifiable (e.g., Fig 18e, cf. Macroneuropteris scheuchzeri; cf. 
Scab Hollow, which contains three times as many specimens. Neuropteris anomala). These mostly were large with fine, dense, 
Species dominance differs between the Spring Valley and curved veins, but lacking critical characteristics for further 
Minonk localities. At Spring Valley, the most commonly identification.
encountered and recognizable specimens in the assemblage were Cardiff Coal Roof Shale (USGS 4150)
isolated sheets of parenchyma cells, contextually associated 
with calamitalean stem remains. Of the more definitive remains, Only a small collection of specimens was made from the 
the lycopsid Synchysidendron andrewsii is the most commonly roof shales of the Cardiff Coal, which, at the time, was being 
encountered species from Spring Valley, as at Minonk. However, mined underground. Unfortunately, we have no information 
overall, marattialean tree ferns, which are very rare in the other on geologic context of the Cardiff fossils. It is likely that the 
roof-shale collection, are the most commonly encountered collection was made from spoils at the mine tipple. Clearly, this 
larger taxonomic group of plants. Lesser components of the flora collection is not representative of the full flora that was present 
include calamitalean remains, pteridosperms, and the lycopsid during the final phases of the channel in which the Cardiff Coal 
Diaphorodendron cf. rimosum. was accumulating. This vegetation may have come from the 
Examples of pteridophytes are illustrated in Figure 17 and channel margins or have been the final phases of a drowning 
Figure 18 a-d. Synchysidendron cf. andrewsii is illustrated in swamp flora. Diversity of the flora is low (Fig. 7d). What 
Figure 17 a-b. Its characteristics are described above, in the is of interest, however, is the dominance of the neuropterid 
Minonk flora. The two specimens illustrated demonstrate the pteridosperm, Neuropteris vermicularis. The remainder of the 
basic features of the species: elongate leaf cushions that are common plants in the flora also are pteridosperms, with a small 
somewhat protuberant and that change in height-width ratio on number of tree ferns and the lycopsid Diaphorodendron.
progressively smaller stems. Neuropteris vermicularis is likely a more widespread species 
Sphenopsid remains include rare Calamites stems (Fig. 17c) than is generally reported. As noted by Bashforth et al. (2016, p. 
and Annularia sp. (Fig. 17d). The latter is characterized by an 620), N. vermicularis is difficult to differentiate from Neuropteris 
asymmetrical leaf whorl with long, narrow leaves, but the absence flexuosa, particularly when a large spectrum of specimens is not 
of leaf tips and insufficient preservation prevent a positive species available. In particular, large pinnules of N. vermicularis with a 
identification (see Wittry, 2020). The groundcover or climbing dense venation are virtually indistinguishable from equally large 
sphenopsid, Sphenophyllum emarginatum is represented by a forms of N. flexuosa. In smaller specimens and near the pinna 
few leaf whorls (Fig. 17 e-f). The specimen illustrated in Figure terminus, however, N. vermicularis pinnules remain elongate 
17f is similar to S. oblongifolium in the narrowness of its leaves whereas in N. flexuosa the pinnules become more squat and 
and the leaf arrangement (opposite laterally projecting pairs rounded. N. vermicularis typically has no lateral veins entering 
and downward facing “bib”). The marginal teeth, however, are the pinnule lamina directly from the rachis, and the pinnules 
rounded rather than acuminate, so there is a possibility this is a lack an auricle on the basiscopic side except in those nearest the 
taphonomic effect and that the specimen is S. emarginatum. terminal pinnule. The basic characteristics of N. vermicularis 
Marattialean tree-fern foliage is illustrated in Figures 17 g-h can be seen in Figure 19 a-d.
and 18 a-d. Figure 17g may be “Pecopteris” cf. cyathea; it appears Other medullosan remains in the collection include 
to have elongate, straight-sided pinnules with a well developed Neuropteris ovata (Figs. 19 e-f, 20d [box 2]), which also is 
midvein that extends to near the tip of the pinnule, and sparse, relatively abundant. These have typical characteristics of this 
dichotomized lateral veins (Fig. 17h). The marattialean foliage species. The pinnules are parallel-sided with rounded apices that 
illustrated in Figure 18 a-d is a lobate form that is most likely are “truncated” on the basiscopic side, and they are auriculate. 
Crenulopteris. The most common species of Crenulopteris in the The midvein is weakly developed and extends about 1/2 - 2/3 
upper Middle Pennsylvanian is C. acadica (Lobatopteris vestita of the length of the pinnule. Lateral venation is fine, arching, 
– see comment by Wagner and Álvarez-Vázquez, 2016) (Wittry and asymmetrical on the acroscopic and basiscopic sides. The 
et al., 2015). A specimen attributable to this species is illustrated identity of the isolated, elongate, narrow pinnule in Figure 19g 
in Figure 18 a-b. The pinnules are elongate with lobate margins; is uncertain. We suggest comparison with Macroneuropteris 
they might be described as pinnae with small, rounded pinnules, macrophylla, which has been identified in the American 
particularly on some larger specimens where the lobation is literature as Neuropteris clarksonii (see Wittry, 2020, p. 195). 
deeper. The midvein of the pinnule is strong and proceeds to Laveineopteris rarinervis (Fig. 19h) is typical of the species, 
near the pinnule tip. Lateral veins are candelabra-like, typical of with relatively small, non-deciduous pinnules. Enlargement of 
the lobatopterid marattialeans. Additional fragmentary remains pinnules from image (h) in Figure 19i shows the coarseness 
of lobatopterids were found (Fig. 18 c-d). We have tentatively of the lateral venation typical of this species. Cyclopterid 
assigned these to Crenulopteris cf. subcrenulata given their pinnules, typical of portions of pteridosperm fronds, are rare in 
lobate form, (both species are lobate), but the lateral veins that the collection. Most are similar to C. fimbriata, typical of N. 
are more widely spaced and, where visible (as in Fig. 18d), the ovata, in having fine venation, although a fimbriate margin is not 
ultimate rachis is more robust. Nonetheless, given the small clearly visible (e.g., Fig. 20a). In contrast, the large cyclopterid 
size of the flora, these fragments may be C. acadica. See Wittry in Figure 20b is coarse veined and the veins are particularly low 
(2020) for a discussion of various forms of marattialean foliage density at the base of the pinnule, possibly indicating affinity 
found in the Mazon Creek flora. with L. rarinervis. A tiny, ribbed seed/ovule with a compression 
Pteridosperms in both of the Colchester roof-shale floras, border is seen in Figure 20d [box 3].
surprisingly, do not include Neuropteris ovata, which is Small numbers of pteridophytes occur in the flora. The small 
abundant in the Colchester Coal seat-earth flora from Scab fern Senftenbergia plumosa (Fig. 20c) is represented by a single 
Hollow. In addition to single specimens of Macroneuropteris specimen, which is enlarged in Figure 20d [box 1]. It is similar 
scheuchzeri and Laveineopteris rarinervis, several specimens to the S. plumosa specimen illustrated in Figure 16d. Both have 
of Alethopteris serlii were identified (Fig. 18f) on the basis characteristic short, falcate pinnules that terminate in a pointed 
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FIGURE 17. USGS 4149. Colchester Coal roof shale (Spring Valley Mine). Pteridophytes. a, Synchysidendron andrewsii USNM 
787768. b, Synchysidendron andrewsii USNM 787769. c, Calamites stem. USNM 787780. d, Annularia sp. USNM 787781. e, 
Sphenophyllum emarginatum USNM 787779. f, Sphenophyllum oblongifolium or S. emarginatum. Leaf narrowness and arrangement 
suggests the former; rounded rather than acuminate teeth, the latter. USNM 787778. g, “Pecopteris” cf. cyathea, marattialean 
foliage. USNM 787771. h, Enlargement of basal-most pinnules illustrated in image (g) to show venation. Scale bars = 1 cm; scale 
bar for image (g) is angular with arrowhead at lower end.
apex. The midvein is strong and traverses the pinnule with DISCUSSION
sparse, lateral veins that dichotomize at least one time. Other 
pteridophytes include a possible lobatopterid marattialean fern, The late Middle Pennsylvanian (Desmoinesian) was a time 
perhaps Crenulopteris acadica or C. subcrenulata, with lobate period during which significant changes took place in tropical 
pinnule margins and candelabra-like lateral venation (Fig. 20e). terrestrial landscapes. These temporal changes were reflected 
Questionable calamitalean remains are only a coarsely ribbed in compositional changes in Pennsylvanian tropical floras, 
axis, but without clear nodes (Fig. 20f). A small pinna (Fig. 20g) best studied for floras from wetland settings. These floras are 
is perhaps a fragment of a filicalean fern, a marattialean or even preserved in coals, either as coal-balls (Phillips et al., 1985) or 
Laveineopteris rarinervis; the flexuous rachis suggests a small, palynofloras (Peppers, 1996; Eble et al., 2001; Bek and Opluštil, 
filicalean fern. 2021), and in siliciclastic rocks both as palynofloras (e.g., Juncal et al., 2019) and as an extensive adpression flora record, mainly 
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FIGURE 18. USGS 4149. Colchester Coal roof shale (Spring Valley Mine). Marattialean ferns and pteridosperms. a, Crenulopteris 
acadica. USNM 787772. b, Enlargement of portion of specimen in image (a) showing pinnule marginal lobation and lobatopterid 
venation. c, Crenulopteris cf. subcrenulata or C. acadica. USNM 787775. d, Crenulopteris cf. subcrenulata or C. acadica USNM 
787774. e, Neuropterid of uncertain affinity, cf. Neuropteris anomala or N. inflata. USNM 787776. f, Alethopteris serlii. USNM 
787777. Scale bars = 1 cm.
in association with coal bearing strata. There are numerous tree ferns (e.g., Costanza, 1985; Phillips et al., 1985; Raymond 
examples documented from Europe Europe ( e.g., Kidston, et al., 2010). By about the middle of the Desmoinesian, there 
1923–1925; Crookall, 1955–1976; Wagner, 1983; Cleal, 1997, was a decrease in the abundance and diversity of cordaitaleans, 
2018; Wagner and Álvarez-Vázquez, 2010; Bashforth et al., and a change in their taxonomic composition, but they remained 
2011; King et al., 2011; Opluštil et al., 2022), but also a relatively quantitatively important; this change took place during what 
small number in the U.S. (e.g., Boneham, 1974; Gastaldo, 1977; Phillips and Peppers (1984) labelled their “Second Cordaitalean 
Pheifer, 1979; Blake, 2002; Wittry 2006) and Canada (e.g., Bell, Interval”. The drop in cordaitaleans and change in the dominant 
1938; Calder et al., 1996). The prevalence of these plants in form thereof (based on ovule/seed type) also witnessed the 
association with tropical wetlands has led to the establishment beginnings of the rise in abundance and diversity of marattialean 
of both palynological and macrofloral biostratigraphic schemes ferns. A similar change was noted in the adpression floras across 
(e.g., Peppers, 1970, 1996; Wagner, 1984; Cleal, 1991; Wagner Euramerica (Pfefferkorn and Thomson, 1982). A second change 
and Álvarez-Vázquez, 2010; Opluštil et al., 2022). was noted in the late Desmoinesian, at which time cordaitalean 
Coal balls and palynofloras from coal beds of Desmoinesian abundance dropped consistently below 1% of swamp-floral 
age indicate that early Desmoinesian floras were rich in biomass, and marattialean abundance continued to increase. 
lycopsids and cordaitaleans of various kinds, as well as a variety During this general time period, some of the most extensive 
of pteridosperms, but relatively small numbers of marattialean peat-forming swamps of all time developed across the coastal 
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FIGURE 19. USGS 4150. Cardiff Coal roof shale (Cardiff Mine). Pteridosperms. a, Neuropteris vermicularis pinna fragments 
and dispersed pinnules. Specimen is 1/2 natural size on printed page with full plate at 18.4 cm wide. b, Neuropteris vermicularis. 
USNM 787749. c, Neuropteris vermicularis. USNM 787750. d, Neuropteris vermicularis impression showing pinnule venation. 
USNM 787753. e, Neuropteris ovata impression showing venation. USNM 787756. f, Neuropteris ovata. USNM 787755. g, 
Macroneuropteris macrophylla. USNM 787762 part. h, Laveineopteris rarinervis. USNM 787757. i, Enlargement of pinnules from 
image (h) showing coarseness of the lateral venation. Scale bars = 1 cm.
129
FIGURE 20. USGS 4150. Cardiff Coal roof shale (Cardiff Mine). Pteridosperms and pteridophytes. a, Cyclopteris sp. USNM 
787758. b, Cyclopteris sp. Low density venation, particularly in the lower portion, suggests affinity with Laveinopteris rarinervis. 
USNM 787763. c, Senftenbergia plumosa. USNM 787764.  d, Senftenbergia plumosa (higher magnification image of specimen in 
image [c]) box 1, Neuropteris ovata box 2, Seed box 3. USNM 787764. e, Lobatopterid marattialean fern, possibly Crenulopteris 
acadica or C. subcrenulata. Note lobate pinnule margins and candelabra-like lateral venation. USNM 787760. f, Calamites stem. 
USNM 787752. g, Pteridophyte foliage, possibly a small fern, a marattialean fern, or even Laveineopteris rarinervis. The flexuous 
rachis suggests a small, filicalean fern. USNM 787766. Scale bars = 1 cm.
130
lowlands, west of the Appalachians (Cecil et al., 2003; Greb differ to a considerable degree but, in all instances, the plant 
et al., 2003). The Colchester and Cardiff coals fall within the remains appear to have been subject to little transport and most 
latter part of the period of cordaitalean abundance, the Middle likely are parachthonous (sensu Bateman, 1991). The sub-
Desmoinesian interval during which their importance was in Colchester seat-earth deposit and the Cardiff Coal roof shale may 
decline and during which marattialeans were beginning to have many aspects of deposition and taphonomy in common and 
increase in diversity and abundance. The uppermost coal bed differ from the conditions under which the Colchester Coal roof-
in the Illinois Basin that includes this “Second Cordaitalean shale deposits formed. None of these accumulations are similar 
Interval” is the Houchin Creek (the Illinois No. 4) Coal, the next to those under which the Mazon Creek biota was preserved.
significant coal above the Survant/Cardiff Coal bed (Fig. 1). The oldest assemblage at Scab Hollow is the sub-Colchester 
Thus, although we have no coal-ball floras from the immediate Coal channel fill, which accumulated during the transition from 
interval under investigation here, we do have reference to one of a more seasonal subhumid climate to a less seasonal humid 
the best known adpression floras of the Pennsylvanian, that from climate during glacial maximum, ultimately transitioning to a 
Mazon Creek, with which to compare. coal swamp flora (the source of the stigmarian root systems in 
Colchester and Cardiff Floras in Environmental Context the top of the deposit, immediately below the coal bed). The two Colchester roof floras are preserved in what were likely mudflats, 
The major, underlying driver of floristic changes during formed during the early phases of sea-level-driven inundation 
the Desmoinesian was a long-term, 106-year time scale, trend of the peat swamp, perhaps by increasingly brackish water, 
toward greater aridity. Superimposed on the longer term trend preserving a peat-swamp-type vegetation. The Colchester Coal, 
were short-term glacial-interglacial cycles on 105-year time from which we do not have a macroflora, lies between these 
scales. These shorter term cycles are marked stratigraphically deposits and represents the wettest part of a glacial-interglacial 
by an alternation of climatically sensitive terrestrial strata, cycle, possibly formed at glacial maximum and in the early 
reflecting climate changes accompanying glacial-interglacial phases of ice melting. Lastly, the Cardiff Coal roof flora may be 
cycles (Cecil, 1990). Coals, formed from peat beds, reflect too small to account fully for the local flora; unfortunately, the 
perhumid and humid climates (10 months or more when rainfall ISGS geologists who visited the Cardiff mines while they were 
exceeded evapotranspiration, sensu Cecil, 2003). Paleosols active did not leave any records of plant fossils they observed. 
and various kinds of fluvial-deltaic sediments reflect periods It is possible, however, that, given the channel form of the coal 
of greater seasonality, ranging from sub-humid to semi-arid. bed, the same channel may have been occupied during the 
These shorter term cyclic patterns are reflected differently in sea-level inundation that terminated formation of the Survant 
strata formed on the great coastal plains west of the Variscan- (Cardiff) peat swamp. Such inundation may have tracked inland 
Appalachian mountain ranges (e.g., Heckel, 2008) in the present in these depressions, thereby capturing a flora that included both 
day United States, or in physiographically similar regions on the peat-swamp elements and plants that lived alongside the channel 
eastern side of the ranges in, for example, the Donets Basin (e.g., on wet mineral soils of floodplains lateral to the peat body.
Eros et al., 2012), than they are in the various intermountain The most unusual of the four collections is that from 
regions (e.g., Opluštil et al., 2015, 2019) or north and south of the Colchester Coal seat earth, from the Scab Hollow Road 
those regions (e.g., Van Hoof et al., 2013) in modern Europe. In ditch (USNM 38404). This collection was deposited in what 
addition to changes in climate co-occurring with the different Wanless (1957, and 1930 fieldnotes) characterized as a small, 
phases of glacial-interglacial cycles, there also were little- sandstone-filled channel. Rooted by stigmarian axes in its 
investigated changes in temperature (Fredericksen, 1972; Tabor upper portions, but lacking remains of arboreous lycopsids, one 
et al., 2013; Matthaeus et al., 2021), which would have been is led to conclude that the stigmarian remains penetrated the 
pantropical, even if affected by local topography. deposit well after the aerial plant remains had been deposited, 
Glacial cycles also would have been accompanied by originating from obligate wetland lycopsid trees that populated 
changes in sea level (Heckel, 2008; Rygel et al., 2008). the developing peat swamp. Furthermore, the flora preserved 
These latter fluctuations, however, although worldwide, were in the channel changes vertically through the deposit, initially 
manifested mainly in those areas directly fronting the ocean, dominated by calamitalean remains, with scraps of marattialean 
such as in the Appalachian Basin and westward, or in the Donets foliage (and possibly calamitalean foliage, reported by Wanless 
Basin in eastern Euramerica. Such regular fluctuations gave rise, but not found by us). The preservation of calamitalean stems as 
particularly in the Midcontinent and Eastern Interior basinal casts, some angular in the bedding, suggests that they may have 
regions of the United States, to so-called cyclothems, alternating been growing in streamside settings or on bars within the active 
packages of marine and terrestrial strata. A cyclothem typically channel. The midpart of the deposit is heavily dominated by 
contains within the terrestrial phase a coal bed, sometimes only the medullosan Neuropteris ovata, of classic form. The lack of 
fluvial-deltaic strata and paleosols, recording glacial maxima. The directional orientation and the mixed, but relatively large sizes of 
marine phase includes shales and limestones of various origins, leaf fragments found abundantly in the deposit indicate standing 
recording phases from glacial melting through re-expansion. water. This inference is supported further by the common 
The present study has focused on one such cycle, which likely presence of fine roots that do not penetrate across the bedding 
represents the transition from glacial maximum through the early surfaces of the deposit but lie on the same planes as the foliage 
stages of deglaciation - the Colchester Coal cycle and associated - they likely represent bank collapse material washed into the 
floras, a widespread glacial event of significant magnitude based deposit. Marattialean tree-fern foliage becomes most abundant 
on the extent of correlative stratigraphic units. This cycle has in the upper portions, documenting plants occupying a surface 
been traced across the United States from the Appalachian Basin with an ever higher water table (consider their aerenchymatous 
in the east to areas of Utah in the west (Cecil et al., 2003; Greb et root systems - Ehret and Phillips, 1977 - giving them access to 
al., 2003). The next cycle, that represented by the Cardiff Coal, flooded substrates). What is surprising is the lack of lycopsids in 
was of lesser magnitude, based on the extent and thickness of the uppermost parts of the seat earth.
correlative units (see Fig. 2). Almost as unusual is the small flora collected in 1906 
Patterns in the data from the Cardiff Coal (USGS 4150). According to the USGS collections records, White and Bain visited both the Cardiff and 
Interpreting the patterns in the data represented by the four Spring Valley mines on the same day. These mines are 80 km (50 
collections is closely tied to the environments of deposition in miles) apart, suggesting that they either did not enter the mines 
which the plant remains were preserved. These environments and simply collected from gob or spoils exposed in the course 
131
of mining, or that they did not explore the mines thoroughly. We Comparison of the Colchester and Cardiff floras with the 
have not been able to locate fieldnotes of either individual that Mazon Creek flora
might shed additional light on the nature of fieldwork or on any 
plant remains that may have been observed but not collected. The Mazon Creek flora is an obvious point of comparison 
The Cardiff Coal collection is of interest not only because of its for the floras discussed here, given that the two Colchester Coal 
stratigraphic position but because of its potential depositional roof-shale floras are, like the Mazon Creek flora, enclosed in the 
environment. Clearly deposited in a shallow channel (Fig. 5a), Francis Creek Shale. The Mazon Creek flora is one of the most 
and well inland of the more continuously developed Survant extensively collected, well researched, and publicly accessible 
peat swamp, the Cardiff Coal represents the finger-like edge of fossil floras of the Pennsylvanian Subperiod (e.g., Janssen, 1979; 
planar peat formation. The channel was filled as downstream Wittry, 2006, 2020). A comparative analysis of the Mazon Creek 
flow was dammed by the developing more extensive peat flora and a stratigraphically equivalent, similarly preserved 
swamp, permitting organic matter to accumulate and clog the flora from Okmulgee, Oklahoma was presented in Moore et al. 
channel; marginal interfingering with shale reflects the vagaries (2013, table 2). Quantitative lists of the most common Mazon 
of swamp expansion and contraction through time. During the Creek taxa (compiled by Wittry) were compared with the entire 
time of peat formation, this swampy area was almost certainly Okmulgee taxonomic list (compiled by Moore and DiMichele, 
surrounded by a flora adapted to growth on wet, siliciclastic soils with identifications validated by Wittry for consistency). 
- a rainforest in more classic conception than would be peat- Based on large numbers of specimens, generally with each 
swamp vegetation. We are inclined to believe that as ice-melting nodule containing only a single specimen, seven of the 10 most 
ensued and coastal transgression began, the channel containing commonly encountered taxa were shared by the two nodule 
the precursor Cardiff peat accumulation was flooded, capturing collections from Mazon Creek and Okmulgee. These include 
some of the later stage swamp plants mixed with remains from the tree ferns Crenulopteris acadica (Lobatopteris vestita) 
the vegetation occupying the wetland floodplains flanking the and indeterminate marattialean fern foliage, the pteridosperms 
channel. This may explain why the flora bears similarity to Macroneuropteris scheuchzeri and Laveineopteris rarinervis, 
the Colchester seat-earth assemblage, in being pteridosperm- calamitalean stems and the foliage form Annularia 
dominated, but also containing rare remains of lycopsid trees. sphenophylloides, and, lastly, various remains of arboreous 
The Colchester Coal roof shale assemblages at Minonk lycopsids, mainly the combination of leaves and reproductive 
(USGS 4146) and Spring Valley (USGS 4149) are both typical of structures. There were an additional eight shared taxa ranked 
coal beds from the upper Desmoinesian, dominated by lycopsids, between 11 and 27, including the marattialean Diplazites unitus, 
particularly members of the Diaphorodendraceae, pteridosperm the pteridosperms Alethopteris serlii and Odontoperis aequalis, 
foliage, and marattialean tree-fern remains, with minor amounts the calamitalean foliage forms Annularia radiata, Annularia 
of calamitalean remains and groundcover pteridosperms, ferns, spinulosa, and Asterophyllites equisetiformis, the shrubby 
and sphenopsids. This makes these assemblages overall more sphenopsid Sphenophyllum emarginatum, and the arboreous 
diverse than the other two. From a taphonomic perspective, they lycopsid Lepidodendron sp. (distinguished from members 
also may have a greater degree of intra-environmental transport of the Diaphorodendraceae, which also were recognized in 
and mixing, thus capturing remains from a larger spatial domain. the assemblages). 11 of the 27 most quantitatively abundant 
Although no coextensive river channel has been identified that taxa from the smaller Okmulgee assemblage were not among 
is contemporaneous with and lateral to the Colchester Coal bed, the most common Mazon Creek taxa, but were reported from 
it is likely that the strata containing these two floras were inland Mazon Creek, according to Wittry’s census. Conversely, 12 of 
of the now well known and extensively studied lagoonal facies the top 27 categories in Wittry’s Mazon Creek compilation did 
of the Francis Creek Shale, the facies in which the Mazon Creek not occur in the Okmulgee assemblage.
biota is preserved. Fortunately, ISGS geologist K.D. White The two Colchester roof-shale floras (Minonk and Spring 
made some helpful observations on the plant fossils he observed Valley) studied here consist of 71 and 43 hand-specimens 
in the Minonk Mine (USGS 4146), noting fern fronds (probably respectively, making them much smaller than the Mazon Creek 
mostly pteridosperms) and lycopsid trunks with diamond flora by several orders of magnitude. These two floras share the 
shaped bark, up to 30 cm in diameter, occurring upward of 3 major elements of lobate marattialeans (such as Crenulopteris 
meters into the roof;  there must have been some roof falls for acadica, specimens of which were identified in one of the 
him to make this observation in 1912. In our plant collections collections), the pteridosperms Macroneuropteris scheuchzeri 
we note the presence of the pectinacean bivalve Dunbarella and Lavineopteris rarinervis, different species of the calamitalean 
and small snails, both characteristic of brackish to near-marine foliage Annularia, the shrubby sphenopsid Sphenophyllum 
water conditions. In combination, these various observations emarginatum, and the lycopsid Diaphorodendron cf. rimosum. 
indicate a similarity of the Colchester Coal roof deposits to those Species of Neuropteris, Alethopteris, Senftenbergia, Mariopteris, 
found flanking channels in underlying Desmoinesian coals, Lepidodendron, and Lepidophloios were identified in one or the 
such as the Murphysboro (Treworgy and Jacobson, 1985), and other of the collections. Given the small size of these collections, 
overlying Desmoinesian coals such as the Springfield, Herrin, they might be considered replicates rather than being suitable 
and Danville, in all of which contemporaneous river channels examples of spatial variation in the composition of the flora, 
have been documented or strongly suspected (Eggert, 1982; and together provide a picture of the flora of the Colchester 
Nelson, 1983; Burk et al., 1987; Elrick et al., 2017; Nelson et al., Coal in its final phases as the landscape was turned from a peat 
2020). These channels were converted to estuaries in the latter swamp to a mudflat. In toto, these floras are compositionally 
phases of peat formation (Archer et al., 2016). In combination comparable to that known from Mazon Creek or Okmulgee. 
with changing climate, the channels are suspected of changing What is noteworthy is the absence of Neuropteris species (either 
from largely black-water rivers, draining the lowland, peat- N. ovata or N. vermicularis) from either of these Colchester 
covered landscapes and mineral-soil wetlands farther inland, to Coal roof-shale collections. Both of these species occur in 
estuaries carrying an increased sediment load, resulting in the the Mazon Creek collection, although only N. vermicularis is 
development of mudflats flanking and progressively burying among the most abundant taxa in Wittry’s analysis in Moore et 
peat beds as sea-level rise progressed (e.g. Archer and Kvale, al. (2013). In conclusion, the roof shale floras of the Colchester 
1993), often rapidly as part of meltwater pulses (Archer et al., Coal, collected inland from the brackish-to-marine facies of the 
2016). We suspect that the roof-shale deposits documented Francis Creek Shale from which nodular floras have been so 
herein formed in the same way. widely collected, are consistent with the more broadly known Mazon Creek floral assemblage.
132
Turning to the Colchester Coal seat-earth assemblage that includes the Colchester Coal. The interval is situated below 
from Scab Hollos, one finds a quantitative, but not qualitative, a major environmental and floristic change that occurred at the 
difference from the Mazon Creek assemblage, indicating its Atokan-Desmoinesian boundary (Bsshforth and Nelson, 2015), 
assembly from a common species pool but reflecting differences one that also saw a change in peat-forming environments from 
in microhabitat conditions. The presence of lobate marattialean more domed to more planar in form (Mastalerz et al., 2018), 
foliage, most likely attributable to Crenulopteris acadica, likely reflecting a major step change in rainfall seasonality 
is a consistent feature, particularly its increasing abundance during the wettest parts of glacial-interglacial cycles (Montañez, 
in the upper portion of the seat-earth flora, wherein it can be 2016). Most of the Brazil Formation flora is preserved in tidalite 
inferred that seasonality of rainfall was decreasing progressively sediments that are thought to have formed on a drowning 
into the beginnings of peat formation. The dominance of coastline (Kvale and Archer, 1990). Most Brazil Formation 
Neuropteris ovata, however, differs from the Mazon Creek plant fossils are preserved as adpressions; the relationship 
pattern wherein this species is the 25th most common taxon in of the siderite-preserved assemblages to the more typical and 
Wittry’s compilation. The other elements of the seat-earth flora, widespread compression-impression assemblages is unstudied, 
calamitaleans and Annularia sphenophylloides (the latter in but these kinds of preservation appear to be spatially separated.
Wanless’ fieldnotes) also are consistent with the broader species 
pool. Perhaps of interest also is the larger size of the collection CONCLUSIONS
than the roof-shale assemblages, but, nonetheless, its much The four floras described in this study, three associated 
lower diversity. with the Colchester Coal and one with the Cardiff Coal, are all 
The small collection (31 specimens) from the Cardiff typically late Middle Pennsylvanian in character. The absence 
Coal certainly is inadequate to provide a full sense of the local of conspicuous cordaitalean remains is a key factor separating 
flora. However, experience suggests that were the collection them from what is known, primarily from palynological studies 
“random” (that is, not a trophy hunt), it likely captures the most (e.g., Phillips et al, 1985; Peppers, 1996), of the peat-swamp 
common elements of the assemblage. The dominant elements floras they precede or supercede stratigraphically, which had a 
of the assemblage are very similar to what is found at Mazon small, but significant cordaitalean component. This difference 
Creek. The assemblage is overwhelmingly dominated by is of interest because of the great range of ecological tolerance 
Neuropteris, with N. vermicularis and N. ovata numbers 1 and exhibited by the cordaitaleans, as a group; elements of this broad 
2 in the count, with Cyclopteris cf. fimbriata as number 3. A taxonomic group might be expected to have inhabited a broad 
few specimens of Laveineopteris rarinervis, a single specimen range of wetland habitats.
of Diaphorodendron, and a marattialean foliage specimen Of particular interest are the two Colchester Coal roof-shale 
identified as Pecopteris cf. cyathea are, again, all consistent with floras, which are paleogeographically inland of that part of the 
the Mazon Creek flora. The marattialean specimen could easily Francis Creek Shale that is rich in siderite nodules and preserves 
be a part of one of the more complex lobate marattialean fronds the well known Mazon Creek flora. These floras likely formed 
of the Crenulopteris/Lobatopteris form, given the many venation in the early phases of marine transgression of the peat, which 
patterns found in different parts of those fronds. In addition, involved a transition from a freshwater peat-forming landscape 
although Diaphorodendron is not among the dominants in the to one of mudflats and an increasingly inundated landscape. 
Wittry quantitative assessment, it is present in the Mazon Creek Nonetheless, plant-fossil assemblages reflect, even in their small 
flora (Wittry, 2020) and ranks among the top 10 taxa reported sample sizes, basic compositional similarity to the Mazon Creek 
from the Okmulgee collection. As noted above, the similarity, assemblage, despite being much less diverse. By all indications, 
quantitatively, of the Cardiff macroflora to the Colchester Coal the Mazon Creek assemblage was allochthonous, drawn from 
seat-earth flora, suggests similarities to their microhabitats, a broad swath of landscape, thus from many small patches of 
with the dominant pteridosperm foliage possibly drawn from vegetation like those preserved in these two assemblages.
siliciclastic soils flanking the peat soils that had formed in the The Cardiff Coal roof flora is of additional interest because 
choked, and/or abandoned channel, mixing the immediately there has been no mining of this coal in over 65 years as of 
surrounding vegetation with the remnants of the dying peat- this date, and there is unlikely to be any additional collecting 
swamp flora. possible from those strata. That said, there may be collections 
As a final note, it should be emphasized that the Mazon from the Cardiff roof shales present in the drawers of one or 
Creek biota is not the only such large-scale plant and animal more museum, university, or private collections that may one 
assemblage preserved in siderite concretions. There are two day appear. More information would be most welcome given the 
other published examples from the American Eastern Interior unusual conditions under which the parent peat formed.
Basin. One is the Carterville flora (Gastaldo, 1977) from the roof 
shales of the Herrin (No. 6) Coal of southern Illinois. The Herrin ACKNOWLEDGEMENTS
Coal is several cycles above the Colchester Coal, but is part We acknowledge the great David White for his commitment 
of the late Middle Pennsylvanian interval during which thick, to documenting the plant fossils from across the United States 
widespread peats blanketed the coastal regions of west-central at a time, late 1800s through the 1930s, when relatively little 
Pangea (Greb et al., 2003). As with the relationship between the was known or published from many areas, particularly using 
two Colchester Coal roof floras described here, and the Mazon active coal mines as the source of specimens. He left a large, 
Creek flora, the allochthonous Carterville flora was preserved and largely unexplored, collection at the National Museum of 
in shales flanking the lower reaches of the Walshville Channel, Natural History. We thank reviewers Christopher Cleal and 
in a brackish to marine setting, whereas upstream of this area Michael Donovan for their careful reading, comments, and 
roof floras are preserved in tidalite mudflats flanking the channel suggestions helpful in the revision of an earlier version of this 
(Archer and Kvale, 1993; Nelson et al., 2020). In a somewhat paper.
different depositional setting, the Stanley Cemetery flora of LITERATURE CITED
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