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Ongoing discoveries of new rangeomorph fossils from the Ediacaran of Avalonia allow us to put forward a unified and approachable scheme for the description and phylogenetic analysis of frondose genera and their species. This scheme focuses upon the branching morphology of rangeomorph units. Our system has the advantage of being applicable at all visible scales of subdivision and is suitable for the study of isolated fragmentary specimens. The system is also free from hypothesis about biological affinity and avoids tectonically influenced features such as shape metrics. Using a set of twelve character states within this unified scheme, we here present emended diagnoses for Beothukis, Avalofractus, Bradgatia, Hapsidophyllas, Fractofusus, Trepassia and Charnia, together with a more extensive taxonomic treatment of the latter genus. For those forms that fall within the morphological spectrum between Trepassia and Beothukis, we introduce Vinlandia gen. nov. It is hoped that this scheme will provide a robust framework for future stud-ies of rangeomorph ontogeny and evolution.
Department of Earth Sciences, Oxford University, South Parks Road, Oxford OX1 3AN, UK; e-mail:
Department of Earth Sciences, Memorial University of Newfoundland, St John’s, NL, Canada A1B 3X5
Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Road, Bristol BS8 1RJ, UK; e-mail: jonathanantcliffe@hotm
Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK; e-mail:
*Corresponding author.
Typescript received 10 October 2011; accepted in revised form 22 April 2012
Abstract: Ongoing discoveries of new rangeomorph fossils
from the Ediacaran of Avalonia allow us to put forward a
unified and approachable scheme for the description and
phylogenetic analysis of frondose genera and their species.
This scheme focuses upon the branching morphology of
rangeomorph units. Our system has the advantage of being
applicable at all visible scales of subdivision and is suitable
for the study of isolated fragmentary specimens. The system
is also free from hypothesis about biological affinity and
avoids tectonically influenced features such as shape metrics.
Using a set of twelve character states within this unified
scheme, we here present emended diagnoses for Beothukis,
and Charnia, together with a more extensive taxonomic
treatment of the latter genus. For those forms that fall
within the morphological spectrum between Trepassia and
Beothukis, we introduce Vinlandia gen. nov. It is hoped that
this scheme will provide a robust framework for future stud-
ies of rangeomorph ontogeny and evolution.
Key words: Ediacaran, rangeomorph, architecture, mor-
phology, taxonomy, Vinlandia, Avalonia.
Ediacaran fossils from the Avalon terrane represent
some of the earliest known macroscopic fossil assem-
blages, ranging from c. 580 to 560 million years old
(Brasier and Antcliffe 2004; Narbonne 2005). Interpreta-
tion of these and other Ediacaran fossils as multicellular
animals ancestral to the Cambrian explosion of Metazoa
has excited much interest (e.g. Glaessner 1966, 1984;
Pflug 1971; Fedonkin 1985, 2003; Gehling 1991; Runnegar
1992; Fedonkin et al. 2007). However, this view currently
rests in the balance; alternative affinities including fungal
(Peterson et al. 2003) and protozoan (Pflug 1972a,b;
Zhuravlev 1993; Seilacher et al. 2003) relationships have
been proposed, while doubt has also been cast on sug-
gested direct relationships with crown group Metazoa
(Antcliffe and Brasier 2007a, 2008).
Over the last decade, there has been a concerted effort
to document occurrences of frondose (adj. meaning to
possess a frond; see Table 1) Ediacaran fossils on bedding
planes in both England and Newfoundland, making use
of conventional approaches (Narbonne and Gehling 2003;
Laflamme et al. 2004, 2007; Hofmann et al. 2008;
Laflamme and Narbonne 2008; Narbonne et al. 2009), as
well as new technologies including high resolution laser
scanning and digital mapping (e.g. Antcliffe and Brasier
2008; Brasier and Antcliffe 2009), and large-scale casting
programs (e.g. Edwards and Williams 2011; Wilby et al.
2011). These recent efforts have brought forth remarkably
preserved fossils that reveal, in unprecedented detail, the
architecture and structure of several Ediacaran taxa. New
observations made on these and other fresh materials
have the potential to lead us to a better understanding of
the construction of rangeomorph organisms (sensu
Narbonne 2004), and their rules for growth (cf. Brasier
and Antcliffe 2004).
Below, we set out broad constructional rules and a
clear, coherent taxonomic scheme to describe the range-
omorph architectures found within frondose Ediacaran
fossils. Although there have been prior attempts at such
an endeavour (e.g. Pflug 1972a,b; Jenkins 1992; Laflamme
and Narbonne 2008; Narbonne et al. 2009), newly emerg-
ing details of Avalonian fossils arguably permit a much
more complete understanding of the architecture of fron-
dose organisms than was previously possible. Prior termi-
nology was often influenced by questionable views about
biological relationships (e.g. use of cnidarian terms such
as ‘rachis’; Jenkins 1985). Laflamme and Narbonne (2008)
have done much to help rationalise the terminology of
the field, and their significant contribution in that regard
is welcomed. In recent papers, we have gone further, and
argued for a fresh approach to ontogeny and evolution
(e.g. Brasier and Antcliffe 2004, 2009). This requires ter-
minologies that are appropriate to the study of self-similar
[Palaeontology, Vol. 55, Part 5, 2012, pp. 1105–1124]
ªThe Palaeontological Association doi: 10.1111/j.1475-4983.2012.01164.x 1105
rangeomorph units across a range of scales, independent
of hypothetical biological relationships and free from
morphometrics. We return to these questions of compet-
ing terminologies in the discussion section below.
In this article, we expand upon the morphological
scheme of Brasier and Antcliffe (2009), developing it into
a unified taxonomic framework. We have aimed for sim-
ple technical terms that can be used across a wide range of
scales (from first- to third-order rangeomorph units) and
that are easy to apply in both the field and laboratory. The
suggested scheme therefore makes use of simple English
words wherever possible. Indeed, our project amounts to
the writing of a verbal equation for growth and develop-
ment. Where uncertainties arise in comparisons between
taxa (e.g. of first-order branches in Bradgatia and Charnia;
see Brasier and Antcliffe 2009, fig. 19), we have therefore
adopted the principle of parsimony – that the simplest
descriptor is sufficient. That means that the whole fron-
dose organism is herein regarded as a single homologous
structure across the eight genera analysed below. This
approach allows our set of terms to be applied during
comparative analyses across this taxonomic spectrum.
Our scheme is also intended to permit the classification
of some (although not all) incomplete fossil specimens,
provided that sufficient detail is preserved within first-
and second-order branches. For the present, however, we
confine this treatment to Avalonian genera whose details
are well preserved down to third-order branching pat-
terns. Such examples require that we focus upon charac-
ters that are robustly independent of tectonic strain
TABLE 1. A glossary of terms useful for the description and analysis of frondose rangeomorphs.
Alignment: the orientation of branches with respect to the growth axis and to each other (Fig. 2B–D; see also subparallel,irregular and
radiating units).
Apical growth tip: distal tip of a frond that contains the main generative zone. It helps to define the polarity of a frondose organism
(Fig. 1A–F).
Apical insertion: addition of new branches at the apical growth tip, with inferred gradual displacement of these down the growth axis as
new branches are added at the apex.
Basal disc: disc or bulb that anchors the organism to the substrate. If present, it occurs at the base (proximal end) of the frondose
organism, to which it may be connected by a stem.
Base of the unit: end of a rangeomorph unit closest (more proximal) to the attachment site of that rangeomorph unit.
Bipolar: possessing a single growth axis but two apical growth tips (Fig. 1B).
Branches: the divisions of the frond.Primary (first order) branches consist of rangeomorph units, which in turn consist of smaller
secondary tertiary etc. branches, likewise consisting of rangeomorph units (Fig. 2A).
Concealed axis: astem or zone in the plane of the frond that is concealed by inward furling of the rangeomorph units (Fig. 2G–H;
see also exposed axis).
Deterministic growth: enlargement of a rangeomorph unit within finite limits of growth (see also non-deterministic growth).
Displayed unit: arangeomorph unit in which the details of branching lie in the plane of the frond and thus are visible in a typical plane
of preservation. Displayed units can either be furled or unfurled (Figs 1 and 3; see also rotated unit).
Distal inflation: where inflation of the rangeomorph units becomes greater away from the base of the unit (Fig. 1E; see also medial
inflation and proximal inflation).
Element: abranch or rangeomorph unit.
Exposed axis: astem in the plane of the frond that is not concealed by the furling of rangeomorph units (Fig. 2F)
Fixed: arangeomorph unit that had little freedom to pivot about its own growth axis during life (see also free).
Free: arangeomorph unit that had freedom to pivot about its own growth axis during life. Some post-mortem rotation may
subsequently take place in fixed units.
Frond: arangeomorph unit provided with one or more apical growth tips that can generate primary branches (Fig. 2B). Fronds may
therefore be unipolar,bipolar or multipolar. Where subsidiary growth tips are present in unipolar forms, then these are called subsidiary
fronds (Fig. 2E).
Frondose organism: an organism that possesses a frond. The term ‘frondose’ refers the whole body of the organism, including a frond
(and any subsidiary fronds), stem and basal disc if present (Fig. 1A–D).
Furled unit: arangeomorph unit that is partially folded around its growth axis, producing edges that lie outside the typical plane of
preservation because they are rolled up against their neighbours (Figs 1H–J and 3C–H).
Glide plane of symmetry: reflectional symmetry along the growth axis that includes a translation of less than one full branch (but
greater than zero) along the axis of reflection.
Growth axis: main axis of symmetry of a frond, which terminates in an apical growth tip. Smaller rangeomorph units are arranged along
subsidiary growth axes.
Inflation: expansion of some elements of morphology during growth without the addition of new units. It provides an aspect of growth
that is additional to apical insertion (Fig. 1C–E).
Irregular units: branches of a particular level of organisation (e.g. primary) that change or switch from subparallel to radiating, causing
irregular spacing and alignments of rangeomorph units along the growth axis (Fig. 2D).
(a feature common throughout Avalonian localities; see
discussion in Liu et al. 2011). Hence, our scheme makes
no use of the shape-based metrics of previous systems
(e.g. Laflamme et al. 2004, 2007; Laflamme and Narbonne
2008; see further discussion below).
The following system is therefore based on criteria con-
cerned primarily with the internal anatomy of branching,
with special reference to the figured type-specimens of
genera. Fortunately, with few exceptions (e.g. Charnia
and Vinlandia n. gen.), our descriptive system does not
require major reorganisation of taxonomic status within
or between the relatively small numbers of genera cur-
rently described. It does, however, permit us to bring the
existing generic diagnoses of Avalonian taxa into much
greater order, allowing them to be viewed as part of a
morphological continuum and to be described objectively
in relation to a shared set of character states.
Our model for the rules of growth in frondose Ediacaran
organisms (see Tables 1 and 2; Figs 1–3) builds upon that
outlined by Brasier and Antcliffe (2004, 2009) and Ant-
cliffe and Brasier (2007a, 2008). We agree with the termi-
nology of Laflamme and Narbonne (2008) in several
instances and adhere to the well-established use of pri-
mary, secondary and tertiary branches. We also concur
with the concepts of branch overlap (Laflamme et al.
2007; Laflamme and Narbonne 2008), and degrees of
branch rotation (Narbonne et al. 2009). But for reasons
discussed later, we do not follow those authors in their
revival of the terms ‘petalodium’ and ‘petaloid’ (sensu
Pflug 1972a), preferring to retain the terms ‘frond’ and
‘row’, respectively. We further develop the terminology of
Brasier and Antcliffe (2009) to introduce terms that are
TABLE 1. (Continued)
Medial inflation: where inflation of the rangeomorph unit is greatest roughly half way along the growth axis (Table 2; see also distal
inflation and proximal inflation).
Moderate inflation: where inflation of the rangeomorph unit does not change conspicuously along the growth axis (Fig. 2D; see also
distal inflation and proximal inflation).
Multipolar: possessing more than two apical growth tips (Fig. 1A; see also unipolar and bipolar).
Non-deterministic growth: enlargement of a rangeomorph unit without finite limits to growth (see also deterministic growth).
Polarity: the number of apical growth tips within a single frondose organism (Fig. 1A–E; see also unipolar,bipolar and multipolar).
Primary branches: the main (first order) subdivisions of the frond, each comprising a rangeomorph unit (Fig. 2A; see also secondary
and tertiary branches).
Proximal inflation: where inflation of the rangeomorph units becomes greater towards the base of the unit (Fig. 1C; see also distal
inflation and medial inflation).
Radiating branches: branches of a particular level of organisation (e.g. primary) that are aligned at increasingly steep angles to each
other along the growth axis of a rangeomorph unit (Fig. 2C).
Rangeomorph unit: a unit of organisation wherein branching proceeds along a glide plane of symmetry, with each branch acting as an
axis for lower levels of branching. At their simplest, these are self-similar structures, possessing comparable architecture at several
scales of investigation (Fig. 3A–B).
Rotated unit: arangeomorph unit that has rotated about its growth axis. It is a mechanism by which a rangeomorph unit can become
undisplayed (Figs 1I and 3E,G; see also displayed unit).
Row: a set of branches arranged on one side of the growth axis of a rangeomorph unit (Fig. 2A). Rows not only comprise primary
branches, they can also be recognised within smaller rangeomorph units.
Secondary branches: the main subdivisions of a primary branch. Also known as a second-order branch (Fig. 2A).
Stem: a stalk-like structure connecting the frond toabasal disc, where present. The stem may extend along the growth axis, and be
either exposed or concealed (Fig. 2F).
Subparallel units: branches of a particular level of organisation (e.g. primary) that are orientated almost parallel to each other along
the growth axis (Fig. 2B; see also radiating units).
Subsidiary growth tips: where a frond possesses a single main polarity, and additional growth tips are generated at subsidiary loci
during later stages of growth (Fig. 2E).
Tertiary branches: the main subdivisions of a secondary branch. Also known as a third-order branch.
Undisplayed unit: arangeomorph unit that has rotated about its growth axis so that the branching detail is no longer visible in the
plane of preservation (see also displayed and furled units).
Undivided unit: arangeomorph unit in which the preserved surface appears smooth, so that any details of subdivision (if they existed)
cannot be seen (Figs 1J and 3H–I).
Unfurled unit: arangeomorph unit that is not folded along its margins, so that the alternating pattern of rangeomorph branching may
be seen within the plane of preservation (Figs 1G and 3A–B; see also furled,exposed,concealed). Unfurled units are commonly free to
Unipolar: possessing one apical growth tip (Fig. 1C–F).
Italics highlight those related terms that are also shown in this glossary.
novel to this work and essential to the architectural argu-
ments developed herein. Table 1 brings these various
descriptive terms together in the form of a glossary, while
Table 2 allows major character states to be compared
between eight rangeomorph genera.
Our unifying model can be summarised as follows. A
frond is a rangeomorph unit with a growth tip that can
generate primary branches. Fronds are able to grow away
from a point of origin (which is often in contact with the
seafloor), progressively generate new primary branches at
their growth tips and ‘inflate’ all of the elements so
formed over time. This growth may eventually cease, or it
may continue indefinitely (deterministic vs. nondetermin-
istic growth, sensu Brasier and Antcliffe 2009). Branches
tend to exhibit forms of ‘rangeomorph architecture’
(sensu Narbonne 2004), comprising second-, third- and
fourth-order self-similar units, each arranged in an alter-
nating pattern along a growth axis. Following Brasier and
Antcliffe (2009), we here propose that the differences
between eight rangeomorph genera (Table 2) can be
explained by variation in a limited number of architec-
tural characteristics. Study of the best-preserved range-
omorph holotypes and paratypes shows that the
morphologies of these Ediacaran organisms can be under-
stood using the following six concepts:
Each unit provided with a growth tip (i.e. a ‘pole’) is here
regarded as a ‘frond’ (Fig. 1). In some frondose taxa, pri-
mary rangeomorph units are generated only at a single
growth tip, with a single terminal pole at the apex of the
frond (e.g. the genera Avalofractus Narbonne et al., 2009;
Beothukis Brasier and Antcliffe, 2009; Charnia Ford, 1958
and Trepassia Narbonne et al., 2009). Such forms we call
unipolar (Fig. 1C–F). Some taxa show a single main
polarity, with subsidiary growth tips (Fig. 2E), as seen in
Bradgatia Boynton and Ford, 1995, where large amounts
of internal division can be observed in super-mature pri-
mary branches (i.e. branches that have started to generate
additional branches by developing subsidiary growth tips,
sensu Brasier and Antcliffe 2009, figs 5 and 8). Other
forms show two distinct growth tips and hence are bipo-
lar, having two poles arranged at 180 degrees (Fig. 1B;
Fractofusus Gehling and Narbonne, 2007; Hapsidophyllas
TABLE 2. A comparison between the character states seen within eight genera of frondose rangeomorphs.
Charnia Trepassia Vinlandia Beothukis Avalofractus Bradgatia Hapsidophyllas Fractofusus
Number of poles 1 1 1 1 1 1 22
Number of rows 2 2 2 2 2 2 22
Inflation of first order
proximal (p), medial (me),
moderate (mo), distal (d)
pmomemep d p p
Inflation of second order
proximal (p), medial (me),
moderate (mo), distal (d)
mo–me mo–me mo–me mo–me mo–me d p d
Displayed structure (mature)
1st order
No No No No Yes Yes Yes Yes
Displayed structure (mature)
2nd order
No No No Yes Yes Yes No Yes
Furled structure (mature)
1st order
Yes Yes Yes Yes No No Yes–No Yes–No
Furled structure (mature)
2nd order
Yes Yes Yes Yes No No Yes Yes–No
Growth axis
Concealed by furling (C),
Exposed as a stem (E)
Subparallel (P) or radiate (R)
1st order
Subparallel (P) or radiate (R)
2nd order
Presence of basal disc Yes Yes Yes Yes Yes No No No
Bamforth and Narbonne, 2009). A few forms not yet
encountered within Avalonia (such as Rangea Gu
1930) may have three or more growth tips and poles (e.g.
Pflug 1972a,b; Grazhdankin and Seilacher 2005). We
here refer to such forms as multipolar (Fig. 1A).
Rows of branches
In the manner of a fern, each frond is typically subdivided
into segments called first-order (or primary) branches (see
Figs 2 and 3). These in turn can be subdivided into sec-
ond-order (or secondary) branches (Fig. 2A), and those
into third-order (or tertiary) branches, and so on. In each
frond, these branches are typically arranged in ‘rows’ alter-
nately along two sides of the growth axis (Fig. 2A). Second-
to third-order branches are also arranged in rows. The rows
of first-order branches (sensu Brasier and Antcliffe 2009) are
found either side of a glide plane of reflectional symmetry
along the growth axis, and such an arrangement can be
seen in all of the taxa discussed herein. In some cases, these
alternations are regularly spaced along the main growth
axis (Fig. 2B, e.g. Charnia), whereas in other taxa (Fig. 2D,
e.g. Beothukis,Trepassia), they appear irregularly spaced.
Further forms occur where three or more rows are thought
to be arranged along the axis. Such taxa include Rangea
(e.g. Jenkins 1985) and Swartpuntia Narbonne et al., 1997,
although the suggestion that this also applies to the holo-
type of Charniodiscus concentricus Ford, 1958 (Brasier and
Antcliffe 2009) has yet to be confirmed across other speci-
mens currently assigned to this genus (e.g. those described
in Laflamme et al. 2004 or Wilby et al. 2011).
This refers to patterns of enlargement between branches
of a given order along a given row (see Fig. 1). When
first-order branches are compared to each other within a
row, they commonly show greater enlargement towards
FIG. 1. Graphic illustration of rangeomorph architecture seen in Ediacaran fronds, demonstrating the concepts of polarity (A–E),
inflation (C–E), furling and rangeomorph display (G–J; sensu Brasier and Antcliffe 2009). Arrows mark the positions of apical growth
tips (which are not detailed here).
the base of the frond. Such examples of proximal infla-
tion (Fig. 1C) are seen, for example, in Charnia masoni
Ford, 1958 (Fig. 4A–B) and Fractofusus andersoni Gehling
and Narbonne, 2007 (Fig. 7C–D). In other cases, greater
inflation appears to have taken place towards more distal
portions of the row of first-order branches. Such distal
inflation (Fig. 1E) can be seen in well-preserved examples
of Bradgatia (Figs 6C and 8F). In yet other cases, greatest
inflation is seen in the medial portions of the first-order
branches, as found in well-preserved examples of Beothukis
mistakensis Brasier and Antcliffe, 2009 (Fig. 5C). Further
examples, exhibiting little or no enlargement in either
direction, include mature specimens of Trepassia wardae
Narbonne et al., 2009 (Fig. 4C–D). The latter condition is
here termed moderate inflation (Figs 1D and 2A–B).
Varying patterns of inflation can also be found at
different levels of subdivision within each frond. Thus, in
Fractofusus misrai Gehling and Narbonne, 2007 (Fig. 7C–
D), first-order branches show proximal inflation, while
second-order branches show distal inflation.
FIG. 2. A, terms for describing rangeomorph fronds, including first-order (primary) branch, second-order (secondary) branch and a
single row of first-order branches. The arrows show the growth axis and point in a distal direction towards the apical growth tip of
the frond. B, a single frond showing subparallel alignment of both its primary and secondary branches (cf. Charnia). C, frond with
radiating alignments of both primary and secondary branches (cf. Bradgatia). D, frond with ‘irregular’ (i.e. subparallel to radiating)
alignments of primary branches and radiating alignments of secondary branches (cf. Vinlandia n. gen.). E, frond showing the
development of two supplementary growth tips (‘S’) near the proximal end (cf. Bradgatia). F, frond with growth axis exposed as a
central stem (cf. Charniodiscus). G, frond with growth axis concealed by furling to form a weakly zig-zag to linear suture (cf.
Trepassia). H, frond with growth axis concealed by tight furling to form a zig-zag suture (cf. Charnia).
Rangeomorph display and furling
There are variations between taxa in the degree to which
the rangeomorph branching architecture is clearly
displayed (see Fig. 1). We here recognise four main char-
acter states that relate to ‘display’:
1. Displayed branches show alternating rangeomorph
units on either side of the central axis of growth
(Figs 1G–H and 3A–D). In many cases, the edges of
these units appear to have been loose and free to
overlap or rotate, in the manner of mature fern pinn-
ules (Fig. 3B). The number of subdivisions visible
within any given specimen varies not only between
taxa, but also between growth stages in a single taxon
and between different qualities of preservation in that
taxon. Well-preserved specimens can display second-,
third-, fourth- and even fifth-order sub-branches (the
colloquially named ‘fractal’ subdivisions of Narbonne
2004) within a first-order branch.
2. Rotated branches have experienced rotation about
their growth axes, so that the rangeomorph alterna-
tions have become twisted to lie beyond the surface of
inspection (such that they are not displayed, except in
rare three-dimensional examples of preservation;
Figs 1I and 3E, G). In Charnia and Trepassia, this rota-
tion was ubiquitous and formed an aspect of growth
(e.g. Fig. 4). In others, such as Bradgatia (Fig. 6C–D)
or Fractofusus (Fig. 7C–D), it could also arise from
later dishevelment of displayed branches.
3. Furled branches are rangeomorph units whose edges
have become furled (folded curled up), to make
smooth junctions with their neighbours (Figs 1H–J
and 3C–H). This state may be present (furled) or
absent (unfurled) in branches having displayed archi-
tecture, but it is especially well seen in branches that
are rotated or undivided (see below). As a term, furling
may also be applied to the condition of the growth
axis. In some forms such as Avalofractus,Hapsido-
phyllas and Charniodiscus, a stem is clearly exposed
along the central axis (Fig. 2F). Where a central stem
is not visible (e.g. Fig. 2G), this concealed condition
is here explained by inward furling of adjacent row
margins to form a linear suture. Where this furling
along the growth axis is very tight, it can result in a
zig-zag suture along the midline (Fig. 2H), of the
kind commonly seen in Charnia (Fig. 4B) and some
specimens of Beothukis (Fig. 5C). As zig-zag sutures
can change into linear sutures according to preserva-
tion, these features are not accepted here as a strong
taxonomic criterion.
4. Undivided branches have edges that are typically
furled, but sutures between the subunits of the
branch appear smoothed over, so that rangeomorph
architecture is not distinct (Figs 1J and 3H–I). This
may explain the smooth and apparently featureless
appearance of small and juvenile branches seen within
otherwise well-preserved specimens.
These four character states can be found together
within the impressions of a few remarkable specimens, as
seen, for instance, in the complex impression of the para-
type for Beothukis mistakensis (OUMNH A
´T.411 p; see
Brasier and Antcliffe 2009, p. 380, fig. 18) and in several
examples of that taxon from Spaniard’s Bay (Narbonne
et al. 2009). These examples all demonstrate how second-
FIG. 3. Illustration of rangeomorph units that can be
displayed, rotated or furled at different levels of branching. The
arrows show the growth axis and point in a distal direction
towards the apical growth tip. A–B, rangeomorph units
displayed and unfurled within both first- and second-order
branches (cf. mature Bradgatia). C, rangeomorph units displayed
and furled within both first- and second-order branches (cf.
immature Bradgatia). E–F, rangeomorph units rotated and
furled in the first order but displayed and furled within the
second order (cf. Beothukis). E, G, rangeomorph units rotated
and furled in both first- and second-order levels (cf. Charnia).
H–I, rangeomorph units furled but undivided at first-order
level, so that second-order subdivisions cannot be seen (cf. some
examples of Charniodiscus).
order rangeomorph units can be furled along their axes.
Likewise, tight rotation and furling of higher order units
can be seen in exceptional material of Charnia masoni
preserved in three-dimensional casts from Russia (e.g.
PIN 3993-7018; see Grazhdankin 2004, p. 207, fig. 2B).
Variation in the degree of rangeomorph display results in
fronds that possess a similar gross morphology, but quite
distinct details of architecture (e.g. Fig. 3). For example,
rangeomorph structure can be displayed within both the
first- and second-order branches of some taxa and may
be visible in smaller sub-branches as well (Fig. 3A–D; e.g.
Avalofractus). In other forms such as Beothukis, range-
omorph elements are typically rotated and undisplayed in
the first-order branches (Fig. 3E), but clearly displayed in
the second-order branches (Fig. 3F). In some taxa, the
furling of branch margins can be highly variable (Table 2,
‘Yes-No’). Further taxa, such as Charnia, exhibit range-
omorph elements that have been rotated at all stages visi-
ble for inspection (Fig. 3E, G), and are thus undisplayed
Alignment of branches
Within a frond, the branches usually show a specific pat-
tern of axial alignment (see Fig. 2). Two main kinds of
alignment may be distinguished:
1. Subparallel branches, with branch axes aligned in a
broadly parallel series along the length of the branch
or frond (Fig. 2B; e.g. Charnia).
2. Radiating branches, with branch axes arranged at dif-
fering angles along the length of the branch or frond
(Fig. 2C; e.g. Bradgatia).
In several taxa, these alignments may change gradu-
ally, or switch rapidly, from subparallel to radiating
within a single specimen, to form a pattern here called
‘irregular’ (Fig. 2D; e.g. Vinlandia n. gen and Beothukis).
In Trepassia wardae (Fig. 4C), the first-order branches
are mainly subparallel, but the second-order branches
vary from subparallel to radiating (see Table 1). While
such radiating alignments could conceivably arise from
the freedom of certain rangeomorph units to pivot
about their axes, they clearly form part of the growth
habit in several taxa.
Presence of a basal disc
Several taxa have a frond connected to a basal disc either
via a distinct stem (e.g. Beothukis,Avalofractus) or with-
out a distinct stem (Charnia,Vinlandia n. gen.). The
basal disc, where present, may have been used for
attachment of the organism to the substrate. No evidence
for such a basal disc has yet been confirmed in Bradgatia,
Fractofusus or Hapsidophyllas.
By considering these features, the body plans of range-
omorph taxa can be characterised with reference to twelve
main character states, as shown for the eight specimens
described in Table 2.
This system has been tested in the field and laboratory
over several years, and we are confident that it provides
an improvement upon previous taxonomic diagnoses,
many of which are based upon shape metrics (length to
width ratios) or on concepts relating to gross morpholog-
ical shape (e.g. Laflamme et al. 2007) – characters that
could be regarded as insufficiently robust for generic
diagnoses. Substantial (and not accurately quantified)
tectonic strain at many Avalonian sites makes this point
particularly relevant (see discussion in Liu et al. 2011).
There is also a common difficulty in compiling shape
metrics from incomplete but otherwise well-preserved
specimens, where only part of the internal architecture
can be well discerned. Our new approach attempts to
overcome these difficulties by basing taxonomy upon pat-
terns of internal branching, rather than upon statements
of overall shape. Consequently, we recommend the use of
branching patterns as a means of disentangling the taxon-
omy of rangeomorph fronds at generic level. This is in
contrast to features such as the numbers of branches at
first- and second-order level, which are here regarded as
more useful for distinguishing species. Shape metrics may
likewise be useful for characterising Ediacaran range-
omorphs at species level, but we feel that too little is yet
known about ontogenic variation within these frondose
taxa (e.g. Brasier and Antcliffe 2004), or of variation in
relation to ecological conditions, to accept shape metrics
as a safe diagnostic criterion. We raise the concern that
some forms have varied their length to width ratios in
non-isometric ways during growth, as, for example, in
relation to ambient seafloor conditions.
This scheme now provides a coherent framework of the
kind needed for future studies into rangeomorph growth,
evolutionary relationships and ecology. In the systematic
section at the end of this article, we demonstrate the util-
ity of the proposed terms by providing emended diagno-
ses for each of the eight rangeomorph genera discussed
and figured herein.
Along with other authors (e.g. Flude and Narbonne 2008;
Laflamme and Narbonne 2008; Narbonne et al. 2009), we
respect the efforts of Hans Pflug (1971, 1972a,b) in map-
ping out the details of what is now termed rangeomorph
architecture (Narbonne 2004). Unlike those authors,
however, we do not recommend redeployment of Pflug’s
largely forgotten terminology for the description of
Avalonian fossils, for the following reasons. Pflug (1972a,
b) was working on much younger (c. 549–543 Ma) and
rather more complex Ediacaran material from Namibia,
specifically, Rangea,Ernietta and Pteridinium (see Fedon-
kin et al. 2007, pp. 69–87). Unfortunately, his work is
written in a language so personal and so model-driven
that it admits of no easy employment here. Our under-
standing of his work is that he envisaged a suite of new
conceptual terms. ‘Corpus’ was used to refer to the whole
body of the fossil (often provided with a stem but with-
out a basal disc). ‘Petaloid’ was used for leaf-shaped
elements of somewhat uncertain homology with our
structures, perhaps ‘rows’. Bunches of six petaloids were
collectively referred to as a ‘flabellum’. ‘Feather structure’
was then used to refer to smaller subdivisions within
these branches, of the kind we here call rangeomorph
units (each constructed from a feather shaped ‘petalon’, a
‘shaft’ and a ‘root’; Pflug 1972a,b, fig. 2). ‘Petalodium’
was seemingly employed to describe the pair of rows of
primary branches found on either side of a ‘petaloid
groove’, but paradoxically, according to our reading of
his models, these two-rowed petalodia did not necessarily
arise directly from a single growth axis (see Pflug 1972a,
b, fig. 3). In other words, Pflug’s terminology does not
appear to be synonymous with the terms used by Nar-
bonne et al. (2009). Nor can it be applied with ease to
Pflug’s Namibian material (see, for example, Grazhdankin
and Seilacher 2005, who use the term ‘vane’ for structures
we here call ‘rows’). Added to this is the problem that
Pflug (1972a,b) assigned the following terms to different
subdivisions within the rangeomorph body, in ascending
order of size: ‘petalon’ (Greek, plural ‘petala’), ‘petaloid’
(English, pl. ‘petaloids’), flabellum’ (Latin, pl. ‘flabella’)
‘petalodium’ (Latin, pl. ‘petalodia’) and corpus (Latin, pl.
‘corpi’). His scheme therefore requires a complete under-
standing of the life cycle and growth of any given range-
omorph taxon, and of its homologies with other taxa. It
also requires us to be sure we are looking at a whole
organism, not just parts of it. Unfortunately, it seems
safer to admit our ignorance here (as highlighted by
Brasier and Antcliffe 2004) and to employ a less convo-
luted, and more permissive, terminology.
We therefore advocate the use of the clear and simple
terms outlined in Tables 1–2 and Figures 1–3. These
terms can be applied to all portions, or subdivisions, of
rangeomorph architecture, even by a novice. Thus, a
‘branch’, a ‘row’ or a ‘growth axis’ can be named regard-
less of the level of subdivision to which it belongs.
Authors such as Ford (1958), Glaessner (1984) and Jen-
kins (1992), as well as the authors in Fedonkin et al.
(2007), have likewise used the English term ‘frond’ for
the leaf-like body of the organism. It is true that ‘frond’
has sometimes been used to refer to the whole ‘frondose
organism’, including any stem or basal disc, whereas we
use ‘frond’ to specifically refer to a rangeomorph unit
provided with one or more apical growth tips that can
generate primary branches. We avoid the term ‘frondlet’
for subdivisions of a frond (e.g. Narbonne 2004) because
of its uncertain application across the various genera and
its ready confusion with ‘frond’. We prefer instead to use
Narbonne’s more utilitarian term of ‘rangeomorph unit’
(or its synonym, ‘rangeomorph element’), because it can
be used at all scales. We avoid Pflug’s term ‘petalodium’
(1972; pace Laflamme and Narbonne 2008; Narbonne
et al. 2009), not only because it is easily confused with
‘petaloid’ and ‘petalon’, but because it is controversial.
We do not agree that Pflug’s usage was intended to be
synonymous with the whole leaf-like body. Finally, we
would remark that the terms ‘petalon’, ‘petaloid, ‘petalo-
dium’, ‘flabellum’ and ‘corpus’ have not proved practical
for Ediacaran teaching, field work or research.
The terminology introduced herein is intended to provide
a secure basis for the diagnosis of rangeomorph fossils,
allowing enigmatic specimens to be recognised and classi-
fied within a coherent framework. It also recognises the
morphological variation seen in these organisms and
allows for the accommodation of future discoveries of
rangeomorph morphotypes, hopefully without the need
for further terminology. The taxa as diagnosed herein (see
below for diagnoses) may represent ‘way-points’ along a
phylogenetic continuum. We have attempted to provide a
clear definition of the genotypic concept for Ediacaran
fronds, so as to divide this morphological continuum into
discrete entities. Cladistic analysis of these trends is still
preliminary (note, for example, the unrooted tree pre-
sented in Brasier and Antcliffe 2009), in part because it is
still very difficult to polarise characters in our data matrix
by means of ancestor–descendant relationships. Most
important here will be the filling out of the morphospace
of Ediacaran organisms (see Antcliffe and Brasier 2007b),
through the discovery of additional forms with character
combinations that are currently undocumented. Our aim
is that this proposed framework should help to provide a
template for the description and analysis of growth and
evolution, in new and existing rangeomorph taxa.
The picture of rangeomorph architecture is becoming
ever more coherent and complete, thanks to the efforts of
several independent teams working around the world, all
of them contributing significantly to the overall body of
evidence (e.g. Grazhdankin 2004; Laflamme et al. 2004;
Narbonne 2004; Gehling and Narbonne 2007; Hofmann
et al. 2008; Brasier and Antcliffe 2009; Narbonne et al.
2009). We believe that debates regarding the nature of
these organisms now require a consistent working termi-
nology that focuses upon the architecture of branching
anatomy, such as the one proposed herein. Once such a
consensus is achieved, it is hoped that exciting questions
relating to evolutionary context, ontogenetic dynamics
and ecological models should come to the fore.
Remarks. Below, we provide emended generic diagnoses
for some of the best-preserved Avalonian frondose taxa,
using the new terminology proposed herein. We have
omitted, for the time being, those taxa whose details can-
not yet be confirmed at third or lower orders of branch-
ing (e.g. Frondophyllas Bamforth and Narbonne, 2009;
Pectinifrons Bamforth et al., 2008; Parviscopa Hofmann
et al., 2008; Primocandelabrum Hofmann et al., 2008; Cul-
mofrons Laflamme et al., 2012). Nor do we consider
Charniodiscus here, owing to uncertainties that remain
about the nature of the holotype in relation to other
specimens from Avalonia and Australia (cf. Laflamme
et al. 2004; Brasier and Antcliffe 2009; Wilby et al. 2011).
Internal patterns of frond architecture are taken from
observations of exceptionally well-preserved and mature
specimens, either on bedding planes directly or from casts
and digital images. Table 1 provides a summary of the
diagnostic criteria for selected genera, with illustrations
(Figs 4–8), and more formal descriptions, presented in
the same order as in the text.
Charnia Ford, 1958
Frond unipolar, comprising two rows of primary
branches arranged alternately along a tightly furled central
axis, forming a zig-zag suture (Figs 4A–B and 8D). First-
order branches typically show proximal inflation, whereas
second-order branches show moderate-to-medial infla-
tion. All first to third-order branches are aligned in mark-
edly subparallel series, with furled margins, having
rangeomorph elements that are rotated and undisplayed.
A basal disc is sometimes preserved.
Trepassia Narbonne, Laflamme, Greentree and Trusler,
Frond unipolar, comprising two rows of irregularly
spaced primary branches arranged along a furled central
axis, commonly forming a linear suture (Figs 4C–D and
8H). Inflation of first-order branches is moderate with no
clear direction, while that of second-order branches is
mainly medial. Alignments of first-order branches are
subparallel. Those of second- and third-order branches
within a single specimen are more irregular and range
gradually or switch abruptly from subparallel to distinctly
radiate. Mature first- to third-order branches have furled
margins, with rangeomorph elements that are rotated and
undisplayed. A basal disc is sometimes preserved.
Vinlandia gen. nov. Brasier, Antcliffe and Liu
Frond unipolar, comprising two rows of irregularly
spaced primary branches, arranged alternately along a
furled central axis, forming a linear to zig-zag suture
(Figs 5A–B, 8C and 9). Inflation of first- and second-
order branches is moderate to medial. First- and second-
order branches are arranged in radiating to subparallel
series. All first- to third-order branches have furled mar-
gins, with rangeomorph elements that are rotated and un-
displayed. A basal disc is rarely preserved.
Beothukis Brasier and Antcliffe, 2009
Frond unipolar, comprising two rows of primary branches
arranged in irregularly spaced alternations along a furled
central axis, forming a linear suture (Figs 5C–D and 8B).
Inflation of first- and second-order branches is moderate
to medial. Mature first- and second-order branches typi-
cally have furled margins, with alignments that are
arranged in radiating to subparallel series. Rangeomorph ele-
ments of the first-order branches are usually undisplayed,
whereas those of second-order branches are clearly dis-
played. A basal disc and stem is sometimes preserved.
Comment. As primary branches were seemingly free to move,
and not fixed to each other except at their bases, presentation of
the fronds can be highly variable, as noted in the paratype (Bra-
sier and Antcliffe 2009, fig. 18).
Avalofractus Narbonne, Laflamme, Greentree and Trusler,
Frond unipolar, comprising two rows of first-order
branches arranged in subparallel series that alternate
either side of a stem exposed along the central axis
(Figs 6A–B and 8A). Inflation of first-order branches is
proximal, while that of second-order branches appears
moderate to medial. Mature first- to third-order branches
are displayed and not furled or rotated. A basal disc is
sometimes preserved.
FIG. 4. A, camera lucida of the holotype of Charnia masoni (LEICT G279) with enlargements of main sketch showing detail. B,
schematic sketches of Charnia. C, above and middle shows camera lucida drawings of the holotype of Trepassia wardae (ROM38628);
at lower right is shown a digital image of juvenile OUMNH A
´T.467 p from Spaniards Bay (locality of Narbonne, 2004). D, schematics
of Trepassia showing architecture. Parts A and C in Figures 4–7 are based on camera lucida drawings that are not retrodeformed.
FIG. 5. A, camera lucida of the new designate plesiotype of Vinlandia antecedens gen. nov. (OUMNH A
´T.409 p.) with enlargement
of main sketch showing detail. B, schematics of Vinlandia showing architecture. C, camera lucida of the holotype of Beothukis
mistakensis (OUMNH A
´T.410 p) with enlargement of main sketch showing detail. D, schematics of Beothukis showing architecture.
FIG. 6. A, digital image of the paratype of Avalofractus abaculus (NFM F-754) with inset image showing details of a cast OUMNH
´T.465 p. B, schematics of Avalofractus showing architecture. C, camera lucida of the holotype of Bradgatia linfordensis (LEICT G26)
with enlargement of second specimen showing detail. D, Schematics of Bradgatia showing architecture.
FIG. 7. A, camera lucida drawing of a specimen of Hapsidophyllas flexibilis (in situ on the Mistaken Point F Surface), with
enlargement of main sketch showing details. B, schematics of Hapsidophyllas showing architecture. C, camera lucida of Fractofusus
misrai (OUMNH A
´T.407 p) with enlargement of main sketch showing details. D, schematics of Fractofusus showing architecture.
Comment. All known specimens of Avalofractus are small
(<100 mm) and potentially immature (early ontogenetic state),
raising the possibility that this taxon may represent the unfurled
or partial (fragmentary) remains of a juvenile form belonging to
another rangeomorph taxon.
Bradgatia Boynton and Ford, 1995
Frond unipolar, with subsidiary growth tips present in
mature specimens, at the distal ends of large first-order
branches (Figs 6C–D and 8F). First- to second-order
branches tend to be distally inflated. First-order branches
comprise two rows of second-order branches with the
freedom to overlap and rotate. First-order branches
arranged in radiating series, alternating along a furled
central axis. Towards their bases (and often in juvenile
stages), first- to second-order branches typically furled
and sometimes rotated, but rangeomorph elements
become progressively displayed and unfurled in the direc-
tion of growth (Fig. 6D). A basal disc is not confirmed.
Comment. In Brasier and Antcliffe (2004, fig. 8), Bradgatia was
envisaged as a colony of Charnia-like fronds. In this article, as
in Brasier and Antcliffe (2009, fig. 19), we favour the more par-
simonious hypothesis that the whole frondose organism of Brad-
gatia is homologous to the frond of Charnia.
Hapsidophyllas Bamforth and Narbonne, 2009
Frond bipolar, comprising two rows of primary branches
emanating alternately from a central axis, which may be
displayed (Figs 7A–B and 8G). Inflation of first-order
branches is proximal, and inflation of second-order
branches is also proximal. First-order branches show sub-
parallel alignments of units with displayed structure, with
both furled and freely overlapping margins. Second-order
branches are often poorly preserved, but are seemingly
rotated and furled, and possess subparallel alignments. A
basal disc is not seen.
Comment. These frondose organisms can appear (falsely) to be
multipolar, owing to freely overlapping margins of their first-
order branches. Juvenile morphologies are poorly known.
Fractofusus Gehling and Narbonne, 2007
Frond bipolar, comprising two rows of primary branches
arranged in irregularly spaced alternations along a furled
central axis, forming a zig-zag suture (Figs 7C–D and 8E).
Inflation of first-order branches is proximal, while infla-
tion of second-order branches tends to be distal. First-
order branches show subparallel alignments of units, with
displayed structure, often infolded or rotated in juvenile
stages. These units are broadly perpendicular to the main
central axis, along which they can be either furled or
overlapping. Axes of second-order branches are subparal-
lel to radiating, often freely displayed and overlapping
towards their margins. A basal disc is not seen.
The system of nomenclature presented above is based
upon the growth and structural architecture of range-
omorph organisms. That being so, it is evident that some
previously described specimens, and species, do not com-
ply with the generic definitions proposed herein for their
respective taxa. We therefore present below a revised syn-
onymy list and diagnosis for the taxon Charnia antecedens
Laflamme et al. 2007, assigning it as the type species of
Vinlandia gen. nov. We also provide an updated taxon-
omy of Charnia masoni to resolve several taxonomic
irregularities regarding that genus. For reasons of strict
formality, we repeat the generic diagnoses of Vinlandia
and Charnia in the section below.
Genus VINLANDIA gen. nov.
Derivation of name. Named after the old Norse name for
Newfoundland, Vinland.
Diagnosis. Frond unipolar, comprising two rows of irreg-
ularly spaced primary branches, arranged alternately along
a furled central axis, forming a linear suture. Inflation of
first- and second-order branches is moderate to medial.
First- and second-order branches are arranged in radiat-
ing to subparallel series. All first- to third-order branches
have furled margins, with rangeomorph elements that are
rotated and undisplayed. A basal disc is rarely preserved.
Type species: Vinlandia antecedens Laflamme, Narbonne, Green-
tree and Anderson, 2007, Newfoundland, Canada.
Vinlandia antecedens (Laflamme, Narbonne, Greentree and
Anderson, 2007)
Figures 5A, 8C, 9
?1998 ‘Charnia masoni’; Nedin and Jenkins, p. 315, fig. 1.
?2003 ‘Charnia masoni’; Narbonne and Gehling,
p. 28, fig. 2a.
.2004 ‘Bush-like form, possibly comparable with Bradgatia
but showing Charnia-like attributes’ O’Brien and
King, p. 210, pl. 5A.
v.2007 Charnia antecedens sp. nov. Laflamme, Narbonne,
Greentree and Anderson, p. 249, fig. 6.
FIG. 8. Rangeomorph Ediacaran taxa from the Avalon region of Newfoundland for which emended diagnoses are provided in the text.
A, Avalofractus abaculus, Upper Island Cove. B, Beothukis sp. Bonavista Peninsula. C, Vinlandia antecedens gen. nov., Bonavista Peninsula.
D, Charnia masoni, Bonavista Peninsula. E, Fractofusus misrai, Mistaken Point. F, Bradgatia sp., Little Catalina. G, Hapsidophyllas
flexibilis, Watern Cove. H, Trepassia wardae holotype ROM38628. Scale bars represent 10 mm (A–E, H), 50 mm (F) and 100 mm (G).
.2008 Charnia antecedens; Hofmann, O’Brien and King,
pp. 17, 19, figs 13.7–13.8, 15.2–15.5?
v.2009 Charnia antecedens; Brasier and Antcliffe,
p. 378, fig. 16.
Diagnosis. As per genus.
Holotype. ROM 54348 (Fig. 9A); redesignated from Charnia an-
tecedens holotype, from the Drook Formation, Conception
Group, Mistaken Point Ecological Reserve, Newfoundland.
Plesiotype. OUMNH A
´T.409 p; new designated plesiotype
(Figs 5A and 9B–D) from the Mistaken Point Formation, near
to the town of Catalina, Bonavista Peninsula, Newfoundland.
Discussion. Since the reallocation of Charnia wardi (Nar-
bonne and Gehling, 2003) to the type species of Trepassia
wardae (Narbonne et al., 2009), it has become apparent
that the even more distinct Charnia antecedens ought no
longer to remain within Charnia. O’Brien and King (2004,
p. 210) have already commented on the clear intermediary
nature of this form as ‘possibly comparable with Bradgatia
but showing Charnia-like attributes’. We agree with this
and therefore place C. antecedens within Vinlandia gen.
nov. This then allows us to characterise the morphological
sequence from Beothukis mistakensis through Vinlandia
antecedens,toTrepassia wardae and thence to Charnia ma-
soni, with much greater clarity (see Table 2 for the ana-
tomical states of each taxon). In this way, each genus now
represents a fundamental constructional type within a
morphological continuum. Vinlandia has rotated range-
omorph elements throughout and can thereby be distin-
guished from Beothukis, which typically has fully displayed
rangeomorph elements in mature second-order (but not
first- or third-order) branches. Both taxa show radiating
first- and second-order elements. Vinlandia is distin-
guished from Trepassia and Charnia in having a marked
tendency towards radiating rather than subparallel first-
and second-order branches. In contrast, Trepassia has
moderately radiating second-order branches, while
Charnia has subparallel second-order branches. Species
differences within each of these genera may be established
on the basis of numbers of branches and shape metrics.
Genus CHARNIA Ford, 1958
Emended diagnosis. Frond unipolar, comprising two rows
of primary branches arranged alternately along a tightly
furled central axis, forming a zig-zag suture. First-order
branches typically show proximal inflation, whereas sec-
ond-order branches show moderate-to-medial inflation.
All first- to third-order branches are aligned in markedly
subparallel series, with furled margins, having range-
omorph elements that are rotated and undisplayed. A
basal disc is sometimes preserved.
Type species. Charnia masoni Ford, 1958, Charnwood Forest,
Charnia masoni Ford, 1958
Figures 4A, 8D
v* 1958 Charnia masoni Ford, p. 212, pl. 13, fig. 1.
? 1959 Charnia sp. Glaessner, p. 1472, text-fig. 1b.
? 1959 Rangea? sp. Glaessner, in Glaessner and Daily,
p. 397, pl. 46, fig. 2.
1961 Charnia sp. Glaessner, p. 75, text-fig.
1962 Charnia sp. Glaessner, p. 484–485, pl. 1, fig. 4.
1966 Rangea grandis Glaessner and Wade,
p. 616, pl. 100, fig. 5.
1973 Glaessnerina grandis; Germs, p. 5, fig. 1D.
1981 Charnia masoni; Fedonkin, p. 66, pl. 3,
figs, 5, 6; pl. 29, fig. 1.
1985 Charnia masoni; Fedonkin, p. 99, pl. 12,
fig. 4; pl. 13, figs 2–4.
v* 1995 Charnia grandis; Boynton and Ford, p. 168,
fig. 1.
.1996 Glaessnerina grandis; Jenkins, p. 35, fig. 4.1.
?1998 Charnia masoni; Nedin and Jenkins,
p. 315, fig. 1.
.1999 Charnia grandis; Ford, p. 231, fig. 3.
.2001 Charnia masoni; Narbonne, Dalrymple and
Gehling, p. 32, pl. 1C.
v.2003 Charnia wardi Narbonne and Gehling,
p. 28 (partim), fig. 2b,c.
.2004 Charnia Grazhdankin, p. 207, fig. 2.
.2005 Charnia masoni; Narbonne, Dalrymple,
Laflamme, Gehling and Boyce, p. 28, pl. 1I.
.2007 Charnia masoni; Laflamme, Narbonne,
Greentree and Anderson, p. 243, fig. 4a–j.
.2008 Charnia masoni; Hofmann, O’Brien and King,
p. 17 (partim), fig. 13.1.
.2008 Charnia grandis; Hofmann, O’Brien and King,
p. 18, fig. 14.
.2008 Charnia masoni; Grazhdankin, Balthasar,
Nagovitsin and Kochnev, p. 804, fig. 2A.
.2009 Charnia masoni; Bamforth and Narbonne,
p. 907, fig. 7.5.
.2011 Charnia masoni; Wilby, Carney and Howe,
pp. 656–657 (partim), figs 2A, 3A.
Diagnosis. As per genus.
Discussion. The emended diagnoses provided in this article
provide an opportunity to revisit the taxonomic concept
of Charnia masoni. We no longer see a need to distinguish
C. grandis from C. masoni on the basis that the fronds are
large or possess more than a particular number of primary
FIG. 9. A, holotype of Vinlandia antecedens gen. nov. ROM54348. B, newly designated plesiotype of V. antecedens OUMNH
´T.409 p. Specimen remains in situ at locality 9 of Hofmann et al. 2008 (their fig. 13.8). C, drawing of the specimen in part B. D,
enlargement of image in part B showing details of branching. Scale bars represent 50 mm (in A) and 10 mm (in B and C).
branches. As we have documented elsewhere (Antcliffe and
Brasier 2007a, 2008; Brasier and Antcliffe 2009), Charnia
is a genus that grows by the apical insertion of new pri-
mary branches and by their proximal inflation, within
which the concept of C. grandis clearly fits. We see, how-
ever, no evidence for distinctive juveniles of C. grandis,
which is therefore regarded as a large growth variant of
the smaller C. masoni (cf. Brasier and Antcliffe 2009).
The distinct nature of the holotype of Trepassia war-
dae (see Narbonne et al. 2009; ROM38628) is agreed
upon by us. However, we here suggest the reassignment
of a specimen once placed within C. wardi (see Nar-
bonne and Gehling 2003, ROM54349; later removed to
Trepassia wardae by Narbonne et al. 2009) to Charnia
masoni. Inspection of this specimen at the Royal Ontario
Museum has not confirmed the presence of internal
features here regarded as diagnostic for Trepassia wardae
(see above).
Acknowledgements. The authors would like to thank Jack
Matthews and Latha Menon at the University of Oxford and
Tony Hancey at the University of Bristol for helpful discussion
during the writing process. We also thank Duncan McIlroy and
the staff of the Memorial University of Newfoundland, as well as
Richard Thomas of the Mistaken Point Ecological Reserve, for
their much valued support throughout this work. Both JBA and
AGL acknowledge the value of NERC doctoral studentships
awarded while at the University of Oxford, which provided
financial assistance for field-based research. JBA gratefully
acknowledges the support of the Royal Commission for the
Exhibition of 1851, while AGL is currently funded by a Henslow
Junior Research Fellowship from the Cambridge Philosophical
Society. We would like to thank So
¨ren Jensen, Marc Laflamme
and Dimitriy Grazhdankin for valuable constructive reviews.
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... Traditional Ediacaran taxonomy emphasized unity of fronds as a high-level taxon (Glaessner, 1979), but more recent studies have suggested that frond morphology more likely represents convergent evolution due to competition for nutrients, oxygen, or gamete dispersal in the water column (Laflamme and Narbonne, 2008;Dececchi et al., 2017). Differences in branching architecture provide a key to subdividing Ediacaran fronds into three robust clades (Laflamme and Narbonne, 2008;Laflamme, 2009: Erwin et al., 2011;Brasier et al., 2012;Dececchi et al., 2017;Dunn et al., 2019a, b). Arboreomorpha exhibit parallel first-order branches, and in the bestpreserved specimens also exhibit second-order and rarely third-order branches perpendicular to the previous order of branching (commonly forming a structure resembling a peapod; Jenkins and Gehling, 1978;Laflamme et al., 2018;Dunn et al., 2019a). ...
... Arboreomorpha exhibit parallel first-order branches, and in the bestpreserved specimens also exhibit second-order and rarely third-order branches perpendicular to the previous order of branching (commonly forming a structure resembling a peapod; Jenkins and Gehling, 1978;Laflamme et al., 2018;Dunn et al., 2019a). Rangeomorpha consist of branches that are selfsimilar, fractal over at least three orders of magnitude, with all subsequent branching orders invariably at an acute angle to the previous branching order (Narbonne, 2004;Laflamme et al., 2007;Narbonne et al., 2009;Brasier et al., 2012;Vickers-Rich et al., 2013;Dunn et al., 2019b). Erniettomorpha consist of petaloids composed of unornamented tube-like first-order branches that are not divided into smaller-scale branches (Narbonne et al., 1997;Grazhdankin and Seilacher, 2002;Ivantsov et al., 2016;Darroch et al., 2022). ...
... Akrophyllas n. gen. does not exhibit rangeomorph architecture, in which the fronds consist entirely of elements commonly termed frondlets that exhibit self-similar branching over several fractal scales and are used as modules to construct larger structures (Narbonne, 2004;Narbonne et al., 2009;Brasier et al., 2012;Dunn et al., 2021), and thus cannot be regarded as a rangeomorph. ...
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Decimeter-scale, elongate, fossil fronds from the Ediacara Range in South Australia were formally described as Rangea longa Glaessner and Wade, 1966, but the disparate nature of documented specimens has hindered their inclusion in global syntheses and has resulted in these fossils being assigned to at least five different genera in two different clades since their discovery. Detailed study of the type material from the Ediacara Range and the few specimens subsequently collected elsewhere in the Flinders Ranges reaffirms that these specimens represent a single species, with the apparent morphological variation between specimens entirely taphonomic and reflecting the obverse and reverse surfaces of these fronds coupled with the orientation of the frond axis and petaloids at different angles relative to the sea bottom on which they were preserved. The preserved architecture of these fronds constitutes three orders of branching microstructure that are strictly orthogonal to immediately higher and lower orders. This implies affinities with the arboreomorphs, but representing a new frond genus herein named Akrophyllas . Akrophyllas n. gen. differs from all other Ediacaran fronds in exhibiting a stalk that is visible only on one side of the frond and is internal to the other side where the first-order branches instead meet at a zigzag axial trace. Akrophyllas n. gen. was attached to a bulbous holdfast on the sea bottom, and evidence for current scours that formed in the lee of the fronds and for a strong current alignment of felled fronds with depositional overlap of adjacent fronds imply an upright, epibenthic lifestyle for Akrophyllas longa new combination. UUID:
... First-order branches at the apical end of the petalodium are poorly preserved but seem to be shorter than those at the proximal end. First-order branches appear to be rotated and furled (sensu Brasier et al., 2012) or single-sided (sensu Narbonne et al., 2009). First-order branches are composed of about a dozen rectangular to near-rectangular second-order branches (sensu Dunn et al., 2021) or secondary branches. ...
... Remarks.-Three species of the genus Charnia-Charnia grandis Glaessner and Wade, 1966, Charnia wardi Narbonne and Gehling, 2003, and Charnia antecedens Laflamme et al., 2007have previously been erected in addition to its type species Charnia masoni Ford, 1958. However, C. grandis is considered a junior synonym of C. masoni (Wilby et al., 2011;Brasier et al., 2012), whereas C. wardi and C. antecedens were subsequently reassigned to Trepassia Narbonne et al., 2009 andVinlandia Brasier et al., 2012, respectively. This Shibantan specimen is tentatively classified in the genus Charnia due to its constrained and alternately arranged first-order branches as well as its single-sided rangeomorph units. ...
... branches and second-order branches are rotated and furled (sensuBrasier et al., 2012) or single-sided (sensuNarbonne et al., 2009). Third-order branches (sensuDunn et al., 2021) are barely discernable in some second-order branches, characterized by obliquely arranged ridges (e.g., Figs. ...
The terminal Ediacaran Shibantan biota (~550–543 Ma) from the Dengying Formation in the Yangtze Gorges area of South China represents one of the rare examples of carbonate-hosted Ediacara-type macrofossil assemblages. In addition to the numerically dominant taxa—the non-biomineralizing tubular fossil Wutubus and discoidal fossils Aspidella and Hiemalora , the Shibantan biota also bears a moderate diversity of frondose fossils, including Pteridinium , Rangea , Arborea , and Charnia . In this paper, we report two species of the rangeomorph genus Charnia , including the type species Charnia masoni Ford, 1958 emend. and Charnia gracilis new species, from the Shibantan biota. Most of the Shibantan Charnia specimens preserve only the petalodium, with a few bearing the holdfast and stem. Despite overall architectural similarities to other Charnia species, the Shibantan specimens of Charnia gracilis n. sp. are distinct in their relatively straight, slender, and more acutely angled first-order branches. They also show evidence that may support a two-stage growth model and a epibenthic sessile lifestyle. Charnia fossils described herein represent one of the youngest occurrences of this genus and extend its paleogeographic and stratigraphic distributions. Our discovery also highlights the notable diversity of the Shibantan biota, which contains examples of a wide range of Ediacaran morphogroups. UUID:
... Fig. 6c). The orientations of the first-order branches in these specimens appear to have been lifted from the sediment surface and resettled on the seafloor in a disordered or 'tousled' manner (sensu Brasier et al. 2012). This process of tousling provides unique insights into the morphology of parts of branches that are otherwise not in contact with the seafloor. ...
... Several authors have considered that the first-order rangeomorph units of Fractofusus were independent of each other, prone to modification by currents (e.g. Brasier & Antcliffe, 2009;Brasier et al. 2012) or capable of active autonomous movement (Jenkins, 1992). ...
... We consider that the upper and lower surfaces of F. misrai were not identical, but that the convex lower surfaces of F. misrai that produce the characteristic negative epirelief impressions curled upwards towards the overlying seawater in the portions that are furled (sensu Brasier et al. 2012) and were displayedand thus more seafloor parallelat their tips. Extrapolation of this model leads to the reconstruction of the upper surface of F. misrai (and by extension F. andersoni; Fig. 9b) as being more concave in morphology, having feathered edges that extended into the water column (Figs 6c-e, 9). ...
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The Ediacaran rangeomorph Fractofusus misrai is the most common and best-preserved of the E Surface fossil assemblage in the Mistaken Point Ecological Reserve of southeastern Newfoundland, Canada. Fractofusus has been interpreted as a fusiform epifaunal soft-sediment recliner, and like other rangeomorphs it has a self-similar, fractal-like branching morphology. The rangeomorph branching of Fractofusus has been considered to be identical on the upper and lower surfaces; however, study of specimens with complex biostratinomic histories suggests clear differences between the upper and lower surfaces. The first-order branches grew down�wards into the sediment from a high point near the midline but grew above the sediment–water interface at their lateral and distal margins. Our new three-dimensional appreciation of rangeo�morph branching in Fractofusus explains many of the taphomorphs of Fractofusus including straight, curved, kinked and tousled forms. The three-dimensional morphology, mode of life, taphonomy and palaeoenvironmental interactions of F. misrai are discussed along with a new three-dimensional reconstruction.
... The Rangeomorpha are an enigmatic late Ediacaran (575-539 Ma) clade that were integral to the first major radiation of macroscopic eukaryotic life, and which are characterized by a modular mode of construction based on the growth and differentiation of fractal branching frondlets. [1][2][3][4][5] Although this unusual fractal mode of construction has led to significant disagreements about how rangeomorphs are related to Metazoa, 1,6 recent phylogenetic and developmental approaches 7,8 suggest that they may represent stem-eumetazoans. However, while rangeomorphs may be relatively well phylogenetically constrained, 8 many facets of their paleobiologyincluding how they fed-are still debated, with a variety of competing hypotheses proposed. ...
... velocity and direction CFD results for Pectinfrons are shown inFigures 3,4,5,6, and S3-S13, while those for C. lyra are presented inFigures 7, 8, and S14-S20. Although the reconstructed patterns of fluid flow differed between models and orientations, some fundamental aspects were common to all simulations. ...
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Rangeomorphs are among the oldest putative eumetazoans known from the fossil record. Establishing how they fed is thus key to understanding the structure and function of the earliest animal ecosystems. Here, we use computational fluid dynamics to test hypothesized feeding modes for the fence-like rangeomorph Pectinifrons abyssalis, comparing this to the morphologically similar extant carnivorous sponge Chondrocladia lyra. Our results reveal complex patterns of flow around P. abyssalis unlike those previously reconstructed for any other Ediacaran taxon. Comparisons with C. lyra reveal substantial differences between the two organisms, suggesting they converged on a similar fence-like morphology for different functions. We argue that the flow patterns recovered for P. abyssalis do not support either a suspension feeding or osmotrophic feeding habit. Instead, our results indicate that rangeomorph fronds may represent organs adapted for gas exchange. If correct, this interpretation could require a dramatic reinterpretation of the oldest macroscopic animals.
... The Ediacaran biotas of Newfoundland have some of the oldest known well-dated complex soft-bodied macroorganisms (Narbonne 2005;Xiao and Laflamme 2009;Matthews et al. 2021) and are essential in furthering our understanding of the evolution of complex macroorganisms. The earliest macrofossils of the Ediacaran biota are widely considered to be stem eumetazoans , and many had unusual fractal-like growth patterns that have no good modern analogues (Narbonne 2005;Brasier et al. 2012;Hoyal Cuthill and Conway Morris 2014). Understanding these enigmatic organisms has been a challenge since their initial discovery (Gürich 1930;Ford 1958). ...
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Fossils from the deep-sea Ediacaran biotas of Newfoundland are among the oldest architecturally complex soft-bodied macroorganisms on Earth. Most organisms in the Mistaken Point–type biotas of Avalonia—particularly the fractal-branching frondose Rangeomorpha— have been traditionally interpreted as living erect within the water column during life. However, due to the scarcity of documented physical sedimentological proxies associated with fossiliferous beds, Ediacaran paleocurrents have been inferred in some instances from the preferential orientation of fronds. This calls into question the relationship between frond orientation and paleocurrents. In this study, we present an integrated approach from a newly described fossiliferous surface (the “Melrose Surface” in the Fermeuse Formation at Melrose, on the southern portion of the Catalina Dome in the Discovery UNESCO Global Geopark) combining: (1) physical sedimentological evidence for paleocurrent direction in the form of climbing ripple cross-lamination and (2) a series of statistical analyses based on modified polythetic and monothetic clustering techniques reflecting the circular nature of the recorded orientation of Fractofusus misrai specimens. This study demonstrates the reclining rheotropic mode of life of the Ediacaran rangeomorph taxon Fractofusus misrai and presents preliminary inferences suggesting a similar mode of life for Bradgatia sp. and Pectinifrons abyssalis based on qualitative evidence. These results advocate for the consideration of an alternative conceptual hypothesis for position of life of Ediacaran organisms in which they are interpreted as having lived reclined on the seafloor, in the position that they are preserved.
... The iconic images of the E surface with current-aligned fronds have fuelled the idea that the overlying tuffite was deposited from a turbidity current (Benus, 1988;Seilacher, 1999;Matthews et al., 2020). Many authors have also considered that it may have also been a water-lain ash-fall tuff (Anderson and Conway Morris, 1982;Jenkins, 1992;Wood et al., 2003;Bamforth et al., 2008;Brasier et al., 2012). The evidence for tuffite deposition from turbidity currents is ...
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The assumption that the majority of the Ediacaran fossil taxa on the iconic Mistaken Point E lived erect in the water column underpins inferences concerning: 1) paleoecology of early macrofossil assemblages; 2) how they reproduced; 3) importance of tiering and 4) controls on community dynamics (Mitchell et al., 2015; Mitchell et al., 2019; Mitchell and Butterfield, 2018; Mitchell and Kenchington, 2018). Recent work has cast some doubt on the erect mode of life of some elements of the Mistaken Point biota (namely Beothukis mistakensis, Charnia masoni, Charniodiscus procerus and Gigarimaneta samsoni; McIlroy et al., 2020; McIlroy et al., 2021; Taylor et al., 2021). Careful consideration of morphology, taphonomy and sedimentology have led to the proposal that the fractal-like Rangeomorpha in particular could have harboured sulfur-reducing symbionts and lived as soft sediment recliners (Dufour and McIlroy, 2017; McIlroy et al., 2020, McIlroy et al., 2021). Critical to this type of palaeobiological assessment is determining life attitude. To this end, it has been proposed that—since it seems that rangeomorphs and relatives could feasibly live in the reclining position like Fractofusus—the null hypothesis for interpreting the mode of life of the organisms in this biota should be that they lived as they are found, flat upon the ancient seafloor (McIlroy et al., 2021). This challenge to the Ediacaran palaeobiological community included recommendations for evidence that might be sought to demonstrate an erect mode of life (McIlroy et al., 2021) such as the presence of associated scratch circles (Jensen et al., 2018). Those methodologies have been used to good effect in demonstrating that Charniodiscus concentricus and Arborea spinosus lived with the frond somewhat erect (sediment-parallel recumbent) in the water column, whereas C. procerus was probably a recliner (Pérez-Pindeo et al., 2022).
... Fractally multiplied elements within a cluster could also undergo glide reflection transformations (for example, in Avalofractus or Beothukis (Narbonne et al., 2009)). The splitting of the main axis, together with multiple transformations of the lowest rank, led to the formation of the most complex three-dimensional structures, the degree of symmetry of which cannot be determined from the existing flat one-sided imprints (for example, Primocandelabrum, Pectinifrons, and Bradgatia (Hofmann et al., 2008;Bamforth et al., 2008;Flude and Narbonne, 2008;Brasier et al., 2012;Narbonne et al., 2014)). Fractal multiplication and E x p l a n a t i o n o f P l a t e 1 Late Precambrian Metazoa: (3, 4, 8, 11) latex casts, (7) pyrite pseudomorph over the organic matrix, other are natural imprints and casts; all specimens are photographed with ammonium chloride coating; scale bar 1 cm. ...
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The deep marine Ediacaran fossil record of Avalonia is dominated by the Rangeomorpha, a clade characterized by up to four orders of fractal-like branching. Despite their abundance, morphological diversity and the recent increase in Ediacaran studies, aspects of their palaeo-biology, palaeoecology and phylogenetic position in the tree of life are still hotly debated. The clade has traditionally been interpreted as consisting of organisms that lived erect in the water column and tethered to the seafloor, based on the intuitive interpretation of their frondose body plan. However, recent work has challenged this view and instead proposes a reclining mode of life for several rangeomorphs, possibly in symbiosis with chemoautotrophic bacteria. Here, we offer a detailed description of exceptionally preserved specimens of Culmofrons plumosa from the Discovery UNESCO Global Geopark in Newfoundland, Canada. We suggest that Culmofrons plumosa should be reinterpreted as a reclining organism based on taphonomic and morphological evidence. Additionally, reproductive modes and a growth model of the species are here inferred, and they appear to be most consistent with a reclining mode of life, offering a novel palaeobiological reconstruction of the species.
Quilted fossils known as vendobionts have remained enigmatic because preserved as unrevealing impressions in sandstone, for example, Arumberia banksi Glaessner & Walter, Noffkarkys storaasli Retallack & Broz, and Hallidaya brueri (Wade) Retallack & Broz from the Ediacaran to Cambrian, Grant Bluff and Arumbera formations of central Australia. These same species are reported here in shaley facies of the Early Cambrian Flathead Sandstone of Fishtrap Lake, Montana. These fossils preserved in three dimensions are infiltrated by clay and confirm that each taxon has distinctive internal chambers reflecting segmentation seen on the surface. Sedimentary structures, petrography and geochemistry of the Montana sediments are evidence that Arumberia, Noffkarkys and Hallidaya lived on supratidal flats of a wave-protected rock-bound estuary unaffected by marine bioturbation, and represent intertidal to supratidal ecosystems widespread from the Ediacaran to Cambrian.
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Charniodiscus is one of the most iconic and first described of the Ediacaran frondose taxa. Since the diagnosis of the holotype of C. concentricus in 1958, the scarcity and poor preservation of unequivocal specimens has resulted in genus-level taxonomic uncertainty. Since the recent reinterpretation of C. concentricus as a multifoliate frond, other Charniodiscus species—all of which are bifoliate—have been left in taxonomic limbo, with most authors comparing them to the clade Arboreomorpha and also the Rangeomorpha. Reconsideration of the taphonomy of the holotype of C. concentricus has revealed that the frond is bifoliate as first described, and also that the frondose portion was broadly conical rather than planar as previously inferred. The conical frond of Charniodiscus is thus morphologically quite different from all other frondose taxa within the Arboreomorpha. Our emendation of the generic diagnosis of Charniodiscus to encompass bifoliate arboreomorphs with conical fronds without a backing sheet distinguishes Charniodiscus concentricus and C. procerus from more planar leaf-like arboreomorphs such as Arborea, A. longa and A. spinosa, all of which has a distinctive backing sheets. Additionally, we find no evidence of rangeomorph-type fractal branching in Charniodiscus.
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The first challenge to the traditional interpretation of the Late Proterozoic Ediacara fossils came with a paper by A. Seilacher (1984, 1989) which not only proposed that Ediacaran organisms became extinct before the Cambrian, but that they represented a previously unrecognized kingdom of structurally unique multicellular organisms: the Vendozoa. This new model is based on a number of uncontested generalizations about size, shape, lifestyle and preservation, that have persisted in the literature. Many of these assumptions are now shown to be misconceptions, as a consequence of newly discovered material in Australia, Canada and the USSR, revealing a more diverse fossil assemblage and suggesting that the organisms were dominantly benthic. The interpretation of this biota in phylogenetic terms, is vindicated by the realization of strong links between some Ediacaran and Cambrian organisms. -from Author
Reference to fossil imprints of soft-bodied Ediacaran metazoans made by Hill and Bonney (1877, p. 757) recorded two of “those curious arrangements of concentric rings which have been supposed to be organisms” present on one of the bedding faces of the North Quarry, Woodhouse Eaves in Charnwood, Forest, Leicestershire, England (see Ford, 1958, 1963); the markings were dismissed as being “accidental ... (and) inorganic.” Early this century, P. Range and H. Schneiderhöhn collected fossil remains of equivalent age at Kuibis Farm in South West Africa (Namibia), and the organic nature of this material was confirmed by Gürich (1929, 1933). The history of discovery of such fossils during the mid part of the century (Sprigg, 1947, 1949; Ford, 1958, 1963, 1968, 1979a,b, 1981; Anderson and Misra, 1968) and the subsequent finding of similar materials widely sited about the globe are well known (e.g., Glaessner, 1984; Hofmann, 1987).
The Ediacaran fauna of Charnwood Forest is reviewed and several new forms are formally named and described, including a complex colonial form Bradgatia linfordensis and three new medusoid genera and species, Ivesia lobata, Shepshedia palmata and Blackbrookia oaksi. A new medusoid species Cyclomedusa cliffi is described. The frondose fossil Charnia grandis is recorded from Charnwood Forest for the first time. Three trails are also noted. -Authors
The late Precambrian genus Rangea Gürich, 1929, a frond-like fossil composed of repeated foliate elements, is one of the first discovered forms belonging to the now widely known soft-bodied assemblages characterizing the Ediacaran Period. Rangea occurs together with the genera Pteridinium Gürich, 1933, and Ernietta Pflug, 1966, in the lower parts of the Nama Group, Namibia (South West Africa). Investigation of the preservation and structure of Rangea , utilizing a methodology similar to that established by Wade (1968, 1971), indicates that it was probably a colonial octocoral consisting of a large tapering primary polyp, or oozoid, and a number of leaf-shaped, conjoined fronds which bore the feeding polyps; it is suggested to belong to a group of early Ediacaran anthozoans which provide a fossil link between the still living Telestacea and Pennatulacea. Similar investigations of Pteridinium and Ernietta disclose that their structure is different from Rangea and does not support ideas that they are related to it.
The Avalon Assemblage (Ediacaran, late Neoproterozoic) provides some of the oldest evidence of diverse macroscopic life and underpins current understanding of the early evolution of epibenthic communities. However, its overall diversity and provincial variability are poorly constrained and are based largely on biotas preserved in Newfoundland, Canada. We report coeval high-diversity biotas from Charnwood Forest, UK, which share at least 60% of their genera in common with ones in Newfoundland. This indicates that substantial taxonomic exchange took place between different regions of Avalonia, probably facilitated by ocean currents, and suggests that a diverse deepwater biota may already have been widespread at the time. Contrasts in the relative abundance of prostrate versus erect taxa likely record differential sensitivity to physical environmental parameters (hydrodynamic regime, substrate) and highlight their significance in controlling community structure.