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The ?Seeds? on 
Padgettia readi
 are Insect Galls: Reassignment of the Plant to
Odontopteris
, the Gall to 
Ovofoligallites
 N. Gen., and the Evolutionary Implications
Thereof
Author(s): Gregory W. Stull , Conrad C. Labandeira , William A. Dimichele , Dan S. Chaney
Source: Journal of Paleontology, 87(2):217-231. 2013.
Published By: The Paleontological Society
DOI: http://dx.doi.org/10.1666/12-063R.1
URL: http://www.bioone.org/doi/full/10.1666/12-063R.1
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THE ??SEEDS?? ON PADGETTIA READI ARE INSECT GALLS:
REASSIGNMENT OF THE PLANT TO ODONTOPTERIS,
THE GALL TO OVOFOLIGALLITES N. GEN., AND THE
EVOLUTIONARY IMPLICATIONS THEREOF
GREGORY W. STULL,1 CONRAD C. LABANDEIRA,2,3 WILLIAM A. DIMICHELE,2AND DAN S. CHANEY2
1Department of Biology and Florida Museum of Natural History, University of Florida, Gainesville, FL 32611, USA, ,gwstull@gmail.com.;
2Department of Paleobiology, NMNH Smithsonian Institution, Washington, DC 20560 USA; and 3Department of Entomology and BEES Program,
University of Maryland, College Park, 20742, USA
ABSTRACT?The Early Permian (Asselian) Euramerican plant Padgettia readi Mamay is reassigned to Odontopteris
Brongniart, as O. readi (Mamay) Stull et al. n. comb. Distinctive elongate structures on neuropteroid pinnules of this plant,
previously interpreted as fructifications, are herein reinterpreted as foliar histoid galls, structurally analogous to blister or
vein galls, and probably induced by an early lineage of hemipterans or mites. These distinctive features are assigned to the
new gall ichnogenus Ovofoligallites Labandeira, n. ichnogen. n. ichnosp, as O. padgetti Labandeira. The Early Permian
association between an Odontopteris host and Ovofoligallites gallers probably originated during the Middle Pennsylvanian
as a similar, antecedent association between Macroneuropteris scheuchzeri (Hoffmann) Cleal, Shute, and Zodrow and the
maker of U-shaped surface features long known as a distinctive, unattributed damage type, but now recognizable as a
likely gall. The persistence of this association between the galler and certain medullosan pteridosperms into the Permian
adds to the morphological richness of the Permian galler insect fauna. The Permian ecological expansion of galling insects
resulted in colonization of new host plants, primarily through a shift from the consumption of entire, mostly pteridophyte
axial organs during the Pennsylvanian to the partitioning of seed plant tissues in leaves and small branches in the Permian.
The Ovofoligallites galler was part of a diverse Permian galler guild involving a variety of plant taxa, organs and tissues
that overwhelmingly targeted multiple lineages of seed plants.
INTRODUCTION
PADGETTIA IS a monospecific genus erected by Mamay (1960)based on isolated pinnules of a neuropteroid pteridosperm
or seed fern (terms that are used interchangeably) possessing
putative seed-like fructifications. Re-examination of these
specimens reveals that the previously described seeds actually
represent a distinctive type of insect damage similar to late
Paleozoic U-shaped surface-feeding lesions that contain
necrotic or otherwise histologically altered tissue surrounded
by a prominent border of reaction tissue. This distinctive kind
of surface feeding has been diagnosed as a Damage Type (DT)
97 (Labandeira et al., 2007), often found on seed-fern taxa
during the Pennsylvanian through Permian (Mu?ller, 1982; Beck
and Labandeira, 1998; Labandeira, 2006b; Krassilov and
Karasev, 2008). While the variously shaped structures de-
scribed by Mamay (1960) resemble that of DT97, the
distinctive damage on Padgettia pinnules now is allocated
informally to DT239, herein formally recognized morpholog-
ically as a new ichnogenus and species: Ovofoligallites padgetti
n. ichnogen. n. ichnosp. The naming of such ichnogenera is
provided for by the latest (fourth) edition of the Code of
Zoological Nomenclature (Bertling et al., 2006), including galls
(Tubbs, 2003).
Mamay (1960) did not consider that an insect might have
been the causative agent of these ovoidal structures. An insect
gall would have been an obvious candidate, particularly as a
superficially similar insect and possibly fungal damage type,
DT97 (Labandeira et al., 2007), occurs commonly on a variety
of seed-fern foliage throughout the late Middle Pennsylvanian
to Early Permian (Mu?ller, 1982; Labandeira and Beall, 1990)
and in the Late Permian (Krassilov and Karasev, 2008) of
Euramerica. However, this distinct type of damage was not well
documented at the time and probably not known to Mamay. In
addition, it is now well established that various modern gall
associations overwhelmingly are species specific, targeting
particular organs and tissues and typically occurring in
recurring spatial patterns on their host plants (Meyer, 1987;
Johnson and Lyon, 1991; Gagne?, 1994). This host-plant
specificity increasingly has been documented on Permian plants
as well (Florin, 1950; Banerjee and Bera, 1998; Beck and
Labandeira, 1998; Labandeira and Allen, 2007; Guleva and
Raman, 2007; Vasilenko, 2007; Prevec et al., 2009). The ??ovoid
objects?? mentioned by Mamay (1960) also show considerable
conformity to a well known type of specialized herbivory,
galling. Conspicuous reaction rims (i.e., plant wound responses
or cellular proliferations) occur on these ovoidal objects,
providing strong evidence that insect damage is present.
Furthermore, these structures are variable in shape, size,
internal distribution of contents, position, and their effect on
adjacent foliar tissues. Ovules embedded in the lamina, or
attached to it, as proposed in Mamay?s original paper, should
have left detectable scars on the leaf surface if attached to the
lamina, or, alternatively, be clearly embedded within foliar
tissue. Instead, the structures interpreted as ovules or seeds are
hollowed-out and extend to the leaf margin, but not beyond.
Finally, a pinnule of a typical Odontopteris pinna, in Mamay?s
original Padgett collections, has been found with similar
marginal U-shaped disorganized tissue surrounded by reaction
rims. When Mamay (1960) considered the origin of these
enigmatic structures, virtually nothing was known about
Paleozoic plant galls, as indicated by more recent reviews of
the topic (Larew, 1992; Scott et al., 1994; Labandeira, 2002).
Since the time of these reviews, a significant diversity of
217
Journal of Paleontology, 87(2), 2013, p. 217?231
Copyright  2013, The Paleontological Society
0022-3360/13/0087-217$03.00
Permian gall material has been documented (Labandeira, 2006a,
2006b), necessitating a reconsideration of the origin of these
curious structures.
In addition, the host plant of these distinctive, insect-induced
structures is revised. If Mamay?s interpretation of these foliar
features (now considered as galls rather than seeds) is excluded,
the foliar characters shown by Padgettia readi Mamay (1960)
are similar to those of the pteridosperm genus Odontopteris (of
the mixoneuroid type) to the extent that this can be determined
from disarticulated remains. Nevertheless, the specimens differ
from known species of Odontopteris in subtle but consistent
ways. Therefore, Padgettia readi is reassigned to Odontopteris
Brongniart, as Odontopteris readi (Mamay) Stull, DiMichele
and Chaney. As a consequence of these changes, the taxonomy
of the host plant is emended and a new ichnotaxon for foliar
structures, formerly considered as seeds, is erected. These two
actions will help to distinguish a distinctive new medullosan leaf
type as well as provide an account of a new form of gall, adding
to the increasingly diverse inventory of Permian gall morphol-
ogies.
THE INSECT GALL
OVOFOLIGALLITES Labandeira new ichnogenus
Figures 1, 2.1, 2.2
Type species.?By monotypy.
Diagnosis.?Flattened ovoidal, ellipsoidal, lenticular, pyri-
form, or otherwise elongate pinnular structures with a long axis
parallel to the major venation of a leaf and characterized by a
variously positioned inner chamber and adjacent modified tissue,
an encircling rim of plant-host response tissue, and tumescent
foliar tissue extending to pinnular margin (Fig. 1).
Etymology.?From the Latin: ovo, meaning an egg, folium,
referring to a plant leaf, and galla, signifying a tumor or gall-like
structure.
Occurrence.?Ovofoligallites n. gen. is known from a single
locality in Texas, U.S.A., occurring approximately 3.2 km NW of
Padgett in Young County, Texas, U. S. Geological Survey
locality 8967 (Mamay, 1960). The stratigraphic position is Lower
Permian, within the upper part of the Archer City Formation,
below Sandstone 8 (Hentz, 1988), of Asselian age.
Remarks.?In 1960 Mamay put forth the following arguments
for his interpretation of Padgettia readi as a medullosan
fructification. First, approximately 100 ovoidal structures are
restricted to the leaves of one plant species, despite the
considerable diversity of plants in the deposit. Second, the
stereotyped orientation and approximately regular spacing of
the foliar structures indicated a reproductive origin rather than
the presence of histologically anomalous tissue. Lastly, the
shape and size of the ovoid objects are comparable to other
small pteridosperm seed types from Permian deposits. From
these three categories of evidence, Mamay (1960) concluded
that the most parsimonious interpretation of the admittedly
unusual structures was that of a seed embedded in the surface
tissues of a medullosan leaf that he named Padgettia readi. It
now appears that these ??seeds?? have incongruous features
inconsistent with known Carboniferous or Permian seed-plant
reproductive structures, and in particular the morphological
range of seed morphologies in medullosan seed ferns. As well,
the taxonomic affinities of the P. readi plant also provide
insight into the identity of these seed-like structures. The
taxonomic affiliation of P. readi, coupled with an evaluation of
the Late Carboniferous and Early Permian plant-damage record
on earlier medullosan (especially neuropteroid) foliage, now
provides a more accurate determination of these curious
structures.
OVOFOLIGALLITES PADGETTI Labandeira new ichnospecies
Figures 1, 2.1, 2.2
Diagnosis.?Enclosed ovoid, elliptical or pyriform structures,
occasionally U-shaped, from 2.5 to 9.0 mm long and 2.0 to 5.0
mm wide, usually borne one to two, and up to several per pinnule,
irregularly spaced in the latter instances. The thickened swellings
are oriented lengthwise along the decurrence of lateral veins
inclined 20 to 308 to the midrib, always on the pinnule blade, with
the rounded, broadest ends oriented toward the midrib, some in
contact with midribs, and apparently adnate to and embedded in
laminar tissues throughout their length. Swellings surrounded by
a prominent ridge of distinctive reaction tissue, often consisting
of carbonized material. Some structures have apices that extend
as either broad or constricted ??beaks?? enclosing distinctive
necrotic or otherwise altered tissue that terminate acutely near or
are abruptly truncated at the pinnular margin.
Description.?Structures numbering approximately 100, dis-
tributed on 52 pinnules, varying from one to nine (perhaps 10) per
pinnule. Structures flattened, retaining significant three-dimen-
sionality revealing subepidermal emplacement of thickened
tissues (Fig. 1); evidence lacking for pedicellate attachment
(Baxter, 1978). Structures occur on the lower pinnular surface,
frequently concentrated toward the pinnular base, occurring
independently at varying intervals along each side of midrib (Fig.
1.1, 1.2, 1.4), not in paired, opposite fashion, never extending
beyond the leaf margin, unlike seeds (Cridland and Morris, 1960).
Larger, pyriform variants have featureless beak-like apices or
constrictions (Fig. 1.1?1.4, 1.5, 1.8, 1.9, 1.11) truncated at
pinnular edge (Fig. 1.1, 1.2, 1.4, 1.10, 1.11); smaller variants
broadly ellipsoidal lacking beaks or extended necrotic areas
toward the pinnular margin (Fig. 1.2, 1.6, 1.7). All structures lack
reproductive features such as spores, sporangial tissues, or seed
membranes.
Structures consist of four recurring, major features: 1) outer
encompassing wall; 2) internal chamber; 3) irregular tumescenses
of tissue adjacent to the internal chamber; and 4) histologically
altered zone extending as a beak distally toward the pinnular
margin (Fig. 1.9), a narrowing (Fig. 1.3), or broader area ending
at margin (Fig. 1.5). Structures enclosed by a distinctive
bordering wall preserved as a ridge or furrow, in turn, surrounded
by zone of altered tissue extending outward to unaffected pinnular
tissue. This wall lacks typical, irregular, botryoidal appearance of

FIGURE 1?The gall Ovofoligallites padgetti (Mamay) Labandeira (2012), n. ichnogen. n. ichnosp., corresponding to DT239, on Odontopteris readi (Mamay)
Stull, DiMichele and Chaney, n. comb., from the Lower Permian (Asselian) locality of Padgett, in north-central Texas. 1, rephotographed image of O. readi
(Mamay, 1960), showing nine or possibly 10 galls, and illustrating their variation in size, shape and contents on the same pinnule, USNM 41165a; 2, camera
lucida drawing of specimen in 1, showing variation in individual gall histology; 3, camera lucida drawing of the detail in the encircled, upper-right gall in 1 and
2, exhibiting a central chamber and adjacent nutritive tissue, necrotic tissue extending to the pinnular margin, and an outer, encapsulating wall; the circular
structure in the lower left may be a hemipteran scale mark; 4, counterpart of specimen in 1, USNM 41165b; 5, enlargement of two galls with prominent outer
walls outlined in the rectangular template at 4, the top one showing a contracted necrotic zone and the bottom one displaying an extended, necrotic swath; 6,
immature ovoidal galls at top (arrow) and bottom (square outline), USNM 546100; 7, enlargement of lower-right gall in 6, showing a thick outer wall and
featureless interior; 8, rephotographed image of O. readi of Mamay (1960), showing an urn-shaped gall, USNM 42179; 9, camera lucida enlargement of
encircled gall in (H), displaying a central chamber, surrounding nutritive tissue, and outer wall; 10, another Ovofoligallites gall on Odontopteris readi, but
bearing a resemblance to U-shaped galls on Macroneuropteris scheuchzeri in 2.3 and 2.4; 11, two pinnules, rephotographed from Mamay (1960), attached to a
rachis at right, with each bearing an Ovofoligallites gall, indicated by arrows, USNM 546101. Scale bars: solid?1 cm; striped?1 mm.
218 JOURNAL OF PALEONTOLOGY, V. 87, NO. 2, 2013
STULL ET AL.?REINTERPRETATATION OF PADGETTIA 219
callus tissue, appearing well organized as curvilinear structures of
relatively constant width (Fig. 1.3, 1.5, 1.7, 1.9). In central part of
structure is single, central, irregularly shaped chamber with
smooth surface and embayed margins (Fig. 1.3, 1.5, 1.9).
Surrounding this chamber are one or more variously shaped
clusters of prominent, puffy areas extending to walls (Fig. 1.1?
1.5). Between the ovoidal central body and distal pinnular margin
is a histologically disorganized area of epidermal and subepider-
mal tissues.
Etymology.?From the sole locality where this ichnospecies is
known at present, Padgett, in Young County, Texas.
Holotype.?USNM-41165a and USNM-41165b, as part and
counterpart (Fig. 1.1?1.3). All specimens are deposited in the
Paleobotanical Type and Illustrated Collection, Department of
Paleobiology, National Museum of Natural History, Smithsonian
Institution, Washington, DC, U.S.A.
Material.?Figure 1.1?1.11: USNM-4115a,b; USNM-546100;
USNM-42179: USNM-546101; Figure 2.1, 2.2: USNM-546192;
and Figure 3: USNM-544639.
Plant host.?Odontopteris readi (Mamay) Stull, DiMichele and
Chaney (Tracheophyta, Spermatopsida, Medullosales, Medullo-
saceae).
Occurrence.?Ovofoligallites padgetti n. gen. n. sp. is known
from a single locality in Texas, U.S.A., occurring approximately
3.2 km NW of Padgett in Young County, Texas, U.S. Geological
Survey locality 8967 (Mamay, 1960). The stratigraphic position is
Lower Permian, within the upper part of the Archer City
Formation, below Sandstone 8 (Hentz, 1988), of Asselian age.
Comparisons.?Ovofoligallites padgetti represents a histoid
gall in which certain localized tissues are affected rather than
entire organs of the plant?s axial vascular system. Histoid galls
form at the site of gall induction and produce cells that display
abnormal histology such as cellular hypertrophy and hyperplasia,
forming tumor-like malformations and affecting only particular
tissues of an organ (Ku?ster, 1911; Roskam, 1992). Histoid galls
affect at most a few local tissue types of an organ and are made
typically by holometabolous insects such as sawflies, beetles,
wasps, and flies (Meyer, 1987). By contrast, organoid galls are
induced at a site remote from gall induction, display a histology
of normal cells but otherwise producing abnormal modifications
resulting in a more systemic co-optation of the host?s
FIGURE 2?Comparison of Ovofoligallites padgetti galls (Mamay) Labandeira (2012), n. ichnogen. n. ichnosp., on hosts other than Odontopteris readi (Fig. 1);
1, an Ov. padgetti gall on a Padgett Odontopteris sp. host other than Ov. readi, USNM 546102; 2, enlargement of gall outlined in the square at 1, showing a
thickened outer wall, bulbous internal contents and possible incipient necrotic tissue toward the pinnular margin; 3, a Macroneuropteris scheuchzeri pinnule from
the late Middle Pennsylvanian Mazon Creek locality of northeastern Illinois, FMNH PP 31384; 4, enlargement of U-shaped, gall-like structure (DT97) from the
outlined square in 3, showing a poorly developed outer border, structureless inner contents, and absence of necrotic tissue. Scale bar?10 cm.
220 JOURNAL OF PALEONTOLOGY, V. 87, NO. 2, 2013
developmental and metabolic machinery (Ku?ster, 1911; Roskam,
1992). Organoid galls are broad-spectrum galls, such as witches?
brooms, formed by fungi, mites and aphids that result in
conspicuous, three-dimensional teratologies typically affecting
stems and buds (Meyer, 1987). In addition, O. padgetti represents
a particular type of histoid gall, a prosoplasmic histoid gall in
which there is a definite size, shape and differentiation into
multiple anomalous tissue layers, in contrast to a cataplasmic
histoid gall, which displays amorphous, poorly differentiated
galled tissues variable in size and shape (Meyer, 1987). Because
of these two, important developmental and morphological gall
distinctions?histoid versus organoid galls, and within histoid
galls, prosoplasmic versus cataplasmic versions?in addition to
other structural peculiarities, O. padgetti can be distinguished
from all other fossil galls.
Most Paleozoic and some early Mesozoic galls are organoid in
nature and typically are deployed as large tumescenses of the
axial portion of the plant, particularly affecting the vasculature
and surrounding tissues. Conspicuous organoid galls from the
Euramerican late Paleozoic include the Middle Pennsylvanian
gall Acrobulbilites sp., consisting of large teratological expan-
sions on sphenopsid cones of northern Europe (Weiss, 1876;
Thomas, 1969; Van Amerom, 1973); the Late Pennsylvanian gall
Pteridoichnos stipitopteri, on the basal petiole of a marattialean
tree-fern host, consisting of hyperplasic and hypertrophic
FIGURE 3?Odontopteris readi (Mamay) Stull, DiMichele and Chaney n. comb. Several overlapping neuropteroid pinnae/pinnules of the type originally
attributed to Padgettia. Note coarseness of lateral veins, thickness of midvein, tapering pinna apex and relatively narrowness compared to length. Arrows point to
galls of the Ovofoligallites padgetti Labandeira 2012, n. ichnogen. n. ichnosp. type, USNM 544639. Scale bar?1 cm.
STULL ET AL.?REINTERPRETATATION OF PADGETTIA 221
alteration of mostly inner parenchyma induced by a holometab-
olous galler (Labandeira and Phillips, 1996, 2002); and an Early
Permian gall, assigned to DT121 (Labandeira et al., 2007),
consisting of a distinctive bud gall on vegetative branchlets of a
walchian conifer (Labandeira and Allen, 2007), similar to galls of
modern aldegid hemipterans on pinaceous conifers (Plumb,
1953). Triassic organoid galls similarly are broadly different
from O. padgetti, the best example of which is the Middle
Triassic ??cone gall?? on an herbaceous voltzialean conifer
(Grauvogel-Stamm, 1978; Grauvogel-Stamm and Kelber, 1996),
consisting of petiolar swellings of short axes that give rise to
female cones, resembling modern sawfly damage. Other formally
described or figured organoid galls from the later Mesozoic and
Cenozoic can be separated from O. padgetti by noticeable
organoid features.
Histoid galls appear in the fossil record during the Permian and,
like O. padgetti, occur overwhelmingly on seed-plant foliage. The
most commonly described foliar galls are small, hemispheroidal,
and circular to somewhat ovoidal in outline, of the same regular
shape, and display a modest variation in size, indicating a
prosoplasmic histoid origin. Such galls are significantly different
from the larger ovoidal to elongate-lenticular shapes that
characterize O. padgetti, and include formally described and
informally mentioned galls on various glossopterid leaf taxa of
Late Permian age (Pant and Srivastava, 1995; Banerjee and Bera,
1998; Banerjee, 2004; Prevec et al., 2009). A similar prosoplas-
mic gall, from the Early Permian of Texas (Labandeira and Allen,
2007), is elliptical in shape and occurs in the midveinal area of a
peltasperm leaf (Labandeira and Allen, 2007) but, like the above-
mentioned glossopterid galls, is different in size, shape, surface
texture and position compared to the galls of O. padgetti.
Similarly, Triassic galls from Gondwana, Euramerica and Angara
are morphologically differentiated from O. padgetti, such as
broom-like galls on the vegetative branches of Voltzia conifers
from the Middle Triassic of France and Germany (Grauvogel-
Stamm and Kelber, 1996; Rothwell et al., 2000); the prominent,
bulbous to hemispheroidal pouch galls on distorted leaves of
Dechellyia, a probable gnetalean seed plant from the Late Triassic
of Arizona (Ash, 1997); and the very different, cataplasmic
histoid galls on the pinnules on various species of the
corystosperm Dicroidium, in the Molteno Formation of South
Africa, consisting of pinnular irregular thickenings of miniscule
chambers that exhibit a pockmarked surface texture, similar to
modern erineum mite galls (Labandeira, 2006b). Other gall types
on gymnospermous foliage occur from the Jurassic to Early
Cretaceous, such as distinctively clustered, hemispheroidal to
bulbous to occasionally pedicellate galls of Wonnacottia on
bennettitalean Anomozamites leaves from the Middle Jurassic of
Yorkshire, United Kingdom (Harris, 1942, 1969); and notably
two small, hemispheroidal gall types from the Jurassic?Creta-
ceous boundary from the Chita Region of Russia, Paleogallus
porusoformis, 1?2 mm in diameter on the bennettitalean leaf
Pityophyllum, and the other, Paleogallus zherichini, 2?4 mm in
diameter on the leaf of the podocarpalean Desmophyllum
(Vasilenko, 2005).
For the Late Cretaceous and Cenozoic, various galls on
angiosperm hosts have been described, but with one possible
exception, none are similar to O. padgetti. Lesquereaux (1992)
and Berry (1923) provided cursory descriptions of an ??oak gall,??
presumably attributable to a gall wasp inducer and on unknown
dicot leaves, from the Dakota Formation of the western United
States. However, the morphology of these bulbuous, hemi-
spheroidal galls lack any known resemblance to O. padgetti.
Krassilov et al. (2008) described and illustrated an irregularly
shaped, polygonal gall housing an unusually small central
chamber, of probable cataplasmic histoid origin, on Dewalquea
gerofitica (Dobuskina) Krassilov 2005 (Krassilov et al., 2005),
from the early Late Cretaceous of Gerofit, Israel. From the same
site, Krassilov and Rasnitsyn (2008) erected two ichnogroups,
three ichnosubgroups, 10 ichnogenera and 25 ichnospecies of
galls, categorized by: 1) whether they represent anomalous
proliferation of surface tissues associated with oviposition scars
or alternatively are true galls; 2) if the galls are organoid or
histoid; and 3) the histoid galls are cataplasmic or prosoplasmic in
histological features. The gall morphologies represent 10 basic
morphologies: cupulate scars bordered by an encircling callus rim
(Cupleon); unenclosed pit galls (Foveon); minutely chambered,
scabrate, pitted galls (Emergeon); small, ostiolate, pustulate galls
(Pustleon); lenticular to fusiform blister galls (Lenticeon);
nonostiolate, spheroidal, pustular galls (Cephaloneon); horned,
conical, ostiolate galls that abscise from the leaf surface
(Ceratoneon); petiolar galls (Petioleon); midrib and primary vein
galls (Costaeon); and leaf-margin roll galls (Involuteon). These
gall-like structures and true galls are highly host-specific,
typically occurring on one host or occasionally on two hosts,
and colonizing a variety of early dicot lineages. None of these
galls resemble O. padgetti. Also dissimilar from O. padgetti are
highly host-specific, histoid-prosoplasmic, and distinctive galls
from the Cenozoic, such as petiolar Pemphigus galls on species of
poplars (Salicaceae, Populus) (Ma?dler, 1936), representing a
significant modern association; and various deciduous cynipid
spindle galls, such as Antronoides, on species of oak (Fagaceae,
Quercus) (Waggoner and Poteet, 1996; Waggoner, 1999; Erwin
and Schick, 2007), both of which survive as prominent
associations in the modern flora (Aoki and Moran, 1996; Russo,
2006). These two later galls, and almost all other documented
Cenozoic galls (Scott et al., 1994) lack features that characterize
O. padgetti, with one exception.
The only described or otherwise figured gall in the fossil record
that could be confused with O. padgetti is Mikiola pontiensis
Villalta (1957), a distinctive cecidomyiid (gall midge) swelling
on a leaf of the beech Fagus pristina Saporta (1867) (Fagaceae),
from the late Miocene of Spain (Die?guez et al., 1996). This
distinctive gall consists of histoid thickening of epidermal and
inner parenchymatic tissues, typical of galls made by some extant
gall-midge species of Mikiola, such as M. fagi Hartig (1839) on
Fagus sylvatica L. (1753). The broadly lenticular-shaped galls are
inclined along the intercostal area between the secondary veins of
the central leaf blade region, and do not contact the midrib nor the
leaf edge. Ovofoligallites padgetti differs from M. potiensis in
that the former has a much larger, ovoidal central chamber, the
distal gall region has a constriction, and the mature gall extends to
the leaf margin. It also is notable that the Cecidomyiidae probably
had an origin during the Early Cretaceous (Blagoderov and
Grimaldi, 2004), postdating O. padgetti by ca. 190 million years
and the end-Permian extinctions.
Remarks.?The O. padgettii structures are interpreted as insect
galls on the basis of three essential features: an outermost wall, an
internal chamber, and adjacent thickenings of nutritive or similar
consumable tissue. In addition, these features bear evidence of
plant response in the form of a disorganized, necrotic area
??downstream?? of the primary supplying vasculature, toward the
pinnular margin that reveals plant-host containment of the gall.
The three reasons offered by Mamay (1960, p. 54) in support of
the fructification interpretation of the U-shaped structures on the
pinnule surfaces also equally support a gall interpretation. The
first of these reasons was the ??. . .complete restriction [of these
features] to one species of plants in a reasonably diverse flora. . ..??
Insect galls are widely understood to be overwhelmingly host
specific and are typically confined to particular organs and often
222 JOURNAL OF PALEONTOLOGY, V. 87, NO. 2, 2013
tissues of their host plants (Johnson and Lyon, 1991; Gagne?,
1994). Consistent with this assertion of Mamay?s and with the
taxonomic reassignment of the suite of Padgett specimens to one
species of Odontopteris, inspection of the larger Padgett
collection did uncover a specimen of a pinnate pinna of
Odontopteris readi (Fig. 2.1, 2.2) that bears Ovofoligallites
padgetti marginal damage, although it is noteworthy that the vast
majority of damage is confined to the neuropteroid pinnules of O.
readi.
Secondly, Mamay mentioned that the ??. . . strict conformity of
the long axes of the objects with the decurrence of the lateral
veins of the supporting pinnules indicates a preferential
orientation along the ultimate vascular strands.?? Whereas Mamay
correctly suggested that reproductive tissues such as ovules are
necessarily connected to a vascular tissue supply, such a
nourishing role also is true for galls (Meyer, 1987). Insect galls
on plants require continual input of nutrients, lipids, essential
elements, and other fluids from vascular tissue necessary to
produce tissue consumed by developing gall occupants. This
delivery system involves hormonal control by the insect galler of
the plant host?s developmental machinery, including in many
instances the production of nutritive tissue, an anomalous tissue
mimicking meristematic growth, consumed by the subadult gall
occupant. Thirdly, Mamay suggested that the ??. . .shape of these
structures is seed-like and their size is comparable to that of any
number of smaller pteridospermous seeds.?? However, the highly
variable size, shape and arrangement of these structures and their
internal features are within the typical range of foliar galls among
a wide variety of candidate arthropod galler groups, including
eriophyoid mites; hemipterans comprising aphids, adelgids,
phylloxerids and psyllids; thrips; sawflies; and perhaps beetles
(Meyer, 1987; Johnson and Lyon, 1991), all of whose ancestral
lineages were present during the Permian (Labandeira, 1998,
2006b, 2011; Shcherbakov, 2000, 2008). Also noteworthy are the
gross and subtle morphological aspects found in these structures.
If these were seeds, both a greater uniformity in size as well as
consistency of fine morphological details would be expected. By
contrast, galls typically are more morphologically variable, given
their more complex origins and expression of variably deployed
patterns of plant-host reaction. Lastly, the apices of the
presumptive seeds are abruptly truncated along the leaf margin,
a feature mentioned in passing by Mamay. Such a termination
suggests a cecidogenous origin, as most shallow-tissue galls, such
as blister galls and vein galls, do terminate at the leaf edge,
whereas projecting seed structures would be expected to extend
beyond the leaf margin without interruption (Cridland and Morris,
1960).
The variability of these morphological features (Fig. 1) and the
high sample size of O. padgetti galls suggest a developmental
sequence. Cecidogenesis commenced as small, ovoidal, walled
galls lacking clear differentiation of internal features and the
absence of adjacent necrotic tissue (Fig. 1.6, 1.7). This was
followed by histogenesis of several clusters of anomalous tissue
occurring next to a variously positioned chamber with limited
production of necrotic tissue (Fig. 1.5 top, 1.9, 1.11 bottom). The
process ended with the largest, most elongate galls characterized
by robust development of a wall and extension to the pinnule
margin of a broad swath of disorganized host-plant tissue (Fig.
1.1, 1.2, 1.5 bottom). These phases of cecidogenesis parallel those
of many modern insect galls (Meyer, 1987).
The morphology, association with a particular host plant, and
physical location on the plant organ strongly suggest that these
ovoid structures are insect galls, herein described as Ovofoligal-
lites padgetti, and permit attribution to a modern gall type, though
less reliably to a specific galler clade. Of the wide variety of gall
morphologies present in a variety of habitats, both modern
(Meyer, 1987; Johnson and Lyon, 1991; Gagne?, 1994) and fossil
(Larew, 1992; Scott et al., 1994; Labandeira, 2002; Labandeira et
al., 2007), there are two obvious gall types to which O. padgetti
bears closest resemblance. One is a foliar blister gall, commonly
formed by mites, aphids, sawflies and gall midges (Nyman et al.,
2000; Maia and Fernandes, 2004; Stireman, 2009), which usually
consists of puffed epidermal tissue and anomalous hyperplasic
and hypertrophic proliferation of relatively shallow tissue, such as
palisade parenchyma, all of which may be encapsulated by a
variously hardened response tissue, such as corky parenchyma
(Meyer, 1987; Johnson and Lyon, 1991). A second attributable
gall type is a foliar vein gall. Histologically deeper-seated vein
galls occur along the primary and especially secondary veins of
leaves where the vasculature and surrounding tissue is galled,
expressed on the surface as an elongate, often ellipsoidal,
epidermal thickening that follows a secondary vein course and
extends on each side of the vein (Yukawa, 1978; Johnson and
Lyon, 1991). Vein galls are significantly thicker than the ungalled
leaf blade and are prominent; like the reaction tissue of mature
blister galls, they would be expected to be highly recognizable if
fossilized. Although blister and vein galls are made by a wide
variety of extant organisms, and occasionally fungi, it was
especially mites and hemipteroid insects that were the likely
fabricators during the Early Permian. The most likely culprit was
an early ancestral lineage of Hemiptera that currently encom-
passes aphids, scale insects, whiteflies, and psyllids, or alterna-
tively, and more remotely, eriophyoid mites (Labandeira, 1998,
2006b). A hemipteran or a mite culprit for the gall would be
consistent with the absence of coprolites or chewed tissue
fragments in O. padgetti gall chambers, indicating that the
fabricator was not a mandibulate insect.
THE HOST PLANT
Division TRACHEOPHYTA
Class SPERMATOPSIDA
Order MEDULLOSALES
Family MEDULLOSACEAE
Genus ODONTOPTERIS Brongniart
ODONTOPTERIS READI (Mamay) Stull, DiMichele and Chaney
Figures 3?6
Basionym.?Padgettia readi Mamay (1960).
Diagnosis.?Fronds at least twice pinnate. Ultimate pinnae
bearing pinnules with varying degrees of lateral fusion,
completely free to completely fused. Free pinnules from 5 mm
high 3 4 mm wide to 12 mm high 3 8 mm wide. Small free
pinnules with straight, nearly parallel, lateral margins, broad,
slightly rounded apices and broad basal attachments to pinna
rachises. No midvein, all veins originating from common strongly
decurrent basal vein inserted in pinna rachis at pinnule base.
Veins strongly upwardly arced, in lower third of length and then
sub-perpendicular to pinnule margin, forking two, rarely three
times, meeting pinnule margin in upper two-thirds, majority
reaching rounded apex. Large free pinnules with subparallel to
slightly convex lateral margins, broadly triangular apex, broad,
attachment to pinna rachis with both basipetal and acropetal
constriction. No midvein. Veins entering pinnules in central and
basiscopic portions at several points, resulting in concentration of
veins in middle portions. Veins in acroscopic half of laminae
proceed more directly to pinnule margins than those in basiscopic
half, which are more curved. Veins fork up to four times and
contact pinnule margins along entire lengths. Pinnae terminate
with various degrees of pinnule fusion, leading to small
undifferentiated terminal pinnules or elongate neuropteroid
pinnules. Large neuropteroid pinnules caducous, mostly
STULL ET AL.?REINTERPRETATATION OF PADGETTIA 223
isophyllous, variable in length, ,1.5 cm to .12 cm, and width to
3 cm wide, with entire margins and cordate bases, rarely lobed at
base or bearing paired, opposite, basal ovoid pinnules. Laminae
taper gently to apices varying from bluntly to sharply acute.
Pinnule midribs to 3 mm wide, finely striate, extending nearly to
pinnule apices. Lateral veins decurrent, depart midrib at an angle
of approximately 308, arching, becoming sub-perpendicular by
laminae midpoints to meet pinnule margins nearly perpendicu-
larly, usually forking once within a short distance of midribs. Leaf
surfaces may bear short, irregularly directed adpressed hairs most
commonly on abaxial sides.
Description.?The specimens from the Padgett locality in
Texas are fragmentary remains of once larger fronds. It is
virtually impossible to reconstruct the frond, with any confidence,
from such material, and the property is no longer accessible for
additional collection. Thus, the taxonomic determinations made
here must be a hypothesis?not only that there was a biological
species in the Early Permian that bore leaves of the type assigned
to Odontopteris readi, but that the various disconnected pinnae
and frond bits of the forms illustrated and described herein belong
to this same species.
In his original description, Mamay (1960) provided a combined
generic and specific diagnosis, a practice that makes descriptions
of new species difficult, essentially requiring re-diagnosis of the
genus. It also turns species emendation into an effective re-
diagnosis. The practice of combined generic-specific diagnoses
should be discouraged. Mamay (1960) also did not link the
morphologies of the large, mixoneuroid pinnules, on which insect
damage is prominent, to the more typically odontopterid pinnae
and their somewhat falcate, broadly attached, decurrent pinnules,
describing the plants (p. 53) as having ??large neuropteroid
pinnules. . . apparently isophyllous, long (12 cm or more) and
relatively narrow (to 3 cm wide) with entire margins and cordate
bases??. On this basis, Mamay (1960) concluded conservatively
that the fronds were at least once pinnate.
Within the larger Padgett collection, a specimen typical of
Odontopteris (Fig. 2.1) was discovered with an Ovofoligallites
padgetti-type gall (Fig. 2.2), identical in form to the kind found
on the large, neuropteroid pinnules upon which the genus
Padgettia was based. This ultimate pinna bore small, bluntly
rounded pinnules and raised the possibility that the original
Padgettia specimens were, in fact, part of a morphologically
variable Odontopteris frond, possibly terminal pinnules of lateral
pinnae or from terminal parts of the frond where pinnule fusion
had taken place. Morphological variability of this kind is known
FIGURE 4?Odontopteris readi (Mamay) Stull, DiMichele and Chaney n. comb., two specimens, USNM 544633. 1, natural size; 2,33 magnification. Upper
specimen is a pinna bearing elongate, neuropteroid pinnules that become more typically odontopterid toward the apex. Lower specimen is a larger neuropteroid
pinnule with slight undulations of a generally entire margin. Scale bars?1 cm.
224 JOURNAL OF PALEONTOLOGY, V. 87, NO. 2, 2013
in many Odontopteris species (e.g., Barthel and Amelang, 2011).
In the Padgett collection, a continuum is found in shape from
neuropteroid pinnae with entire margins to pinnae consisting of
entirely free odontopterid pinnules, illustrated in Figures 3
through 7. This series begins with the typical ??Padgettia?? of
the type originally described by Mamay (1960) (Fig. 3). Figure 4
illustrates a pinna composed of small, but tongue-shaped
pinnules, with an elongate, terminal portion composed of
progressively more fused pinnules, becoming more odontopterid
in shape closer to the apical area. Some of the larger pinnae show
marginal undulations, as illustrated by two overlapping pinnae in
Figure 5.1 and 5.2. These marginal undulations become deeper in
other pinnae (Fig. 5.3, 5.4), revealing more odontopterid pinnule
shapes of a somewhat rounded form with broad, flat apices.
Continued lobing leads to mostly free but still basally fused
pinnules (Fig. 6.1). Ultimately, pinnae bearing free pinnules can
be found, with broad but slightly constricted bases that are weakly
confluent (Fig. 6.2) or completely free and distinct (Fig. 7). In all
of these forms, the venation is essentially the same: coarse,
relatively sparse, somewhat fasciculate, and extending to the
distal margin of the pinna or pinnule. This is illustrated in a series
of camera-lucida line drawings (Fig. 8) that follows the same
trajectory as illustrated in the photographic plates, beginning with
typical ??Padgettia??-type pinnules of various widths, some with
slight marginal undulation (Fig. 8.1?8.4), then showing various
degrees of pinna to free pinnule transition (Fig. 8.5?8.9).
Etymology.?Mamay (1960) named the species in honor of
Charles B. Read, paleobotanist with the U.S. Geological Survey.
Holotype.?USNM 41165a and USNM 41165b, as part and
counterpart (Fig. 1.1, 1.4). All specimens are deposited in the
Paleobotanical Type and Illustrated Collections, Department of
Paleobiology, National Museum of Natural History, Smithsonian
Institution, Washington, DC, U.S.A.
Occurrence.?Odontopteris readi is known from a single
locality in Texas, U.S.A. This location was given in Mamay
(1960) as lying approximately 3.2 km NW of Padgett in Young
County, Texas, as U.S. Geological Survey locality 8967. It is
FIGURE 5?Odontopteris readi (Mamay) Stull, DiMichele and Chaney n. comb. 1, 2, two overlapping pinnae with slight marginal lobing, USNM 544638; 3, 4,
pinna with deeply incised margins that define confluent, but relatively distinct pinnules, USNM 544632. Scale bars?1 cm.
STULL ET AL.?REINTERPRETATATION OF PADGETTIA 225
FIGURE 6?Odontopteris readi (Mamay) Stull, DiMichele and Chaney n. comb. 1, pinna with confluent pinnae, USNM 544636; 2, pinna with free pinnules (top
specimen) showing slight basal confluence, and pinna (lower specimen) of same order with pinnules fused in proximity to the pinna apex, USNM 544637. Scale
bars?1 cm.
226 JOURNAL OF PALEONTOLOGY, V. 87, NO. 2, 2013
stratigraphically in the Lower Permian, at the time assigned to the
Moran Formation, of Asselian age. In the revised stratigraphic
terminology of Hentz (1988), the Padgett locality is in the upper
part of the Archer City Formation, below Sandstone 8.
Remarks.?When considered in terms of this pattern of
variability in form, Odontopteris readi compares closely with
several species of Odontopteris from the latest Pennsylvanian and
Early Permian of equatorial Pangaea, variously classified as part
of the Mixoneura Weiss group of odontopterids. There is
considerable confusion surrounding the use of the name
Mixoneura, however, a matter that is cogently discussed in
Wagner and Castro (1998). Laveine and Delbecque (2011) argue
for a natural biological distinction between Odontopteris and
Mixoneura on the basis of frond architecture. However, as they
note, this complex is in need of detailed taxonomic revision. The
name Odontopteris was chosen for the Padgett material, in part
because of the present state of understanding of Mixoneura and,
in part, because of the fragmentary nature of the specimens,
preventing reconstruction of the frond architecture.
The species to which O. readi compares most closely include
Odontoperis lingulata Goeppert and O. subcrenulata Rost, which
are possibly synonymous. These species are characterized by
pinnule shape variation similar to that of O. readi, including
forms intermediate between more typically pinnulate pinnae and
entire-margined, neuropteroid pinnae. Free to basally confluent
pinnules are mostly rounded and often with squarish apices; entire
margined, neuropteroid pinnae have wide, well marked midveins.
Venation, however, appears to be considerably finer than that
typical of O. readi specimens. Furthermore, in the Padgett
population of O. readi specimens, no pinnae were found that
show a clear transition from free or mostly free pinnules to large
terminal pinnules of neuropteroid aspect, which implies that such
transitions may have been disposed differently in O. readi than in
these other species, or that the O. readi frond might have been
small and zones of such transitions limited or non-existent.
The morphological variation proposed here to exist in
Odontopteris readi may find a parallel in Odontopteris schlo-
theimii Brongniart, recently redescribed by Barthel and Amelang
(2011), who propose frond dimorphism, possibly sexual in origin,
between polleniferous and ovuliferous plants. The nature of the
variation in shape that they illustrate for this species is similar to
that seen in O. readi. The similarity extends to details such as the
coarseness of the venation, the strong differentiation of pinnule-
bearing pinnae and entire, neuropteroid pinnae, strong midveins
in neuropteroid pinnae, and the presence of ??intermediate?? forms
with various degrees of marginal undulation. Free pinnules of O.
FIGURE 7?Odontopteris readi (Mamay) Stull, DiMichele and Chaney n. comb., USNM 544635. 1, natural size; 2, 33 magnification. Pinnae (right-hand
specimen) with completely free pinnules of odontopterid aspect. Note constricted base and rounded shape. The left hand specimen is an entire, large neuropteroid
pinnule with thick midvein, sparse, coarse lateral venation and entire margin. Note the cordate base. Scale bars?1 cm.
STULL ET AL.?REINTERPRETATATION OF PADGETTIA 227
schlothemii, however, are somewhat more angular than those of
O. readi, which tend to be rounded in most forms of development.
There are other species that belong in this mixoneuroid group
of plants, at least based on the spectrum of variation displayed by
their dispersed remains. This includes such forms as Odontopteris
gimmi Remy (Wagner and Castro, 1998), Mixoneura wagneri
Lorenzo (Castro, 2005), and Odontopteris pseudoschlothemi de
Maistre (Doubinger et al., 1995). These all differ from one
another and from O. readi in various details regarding the shape
of pinnules, the commonness of specimens displaying transitions
from pinnulate pinnae to entire-margined neuropteroid pinnae/
pinnules, and aspects of venation.
In his original description of Padgettia, Mamay (1962) noted
that his new plant ??bears a close resemblance to Neuropteris
permiana Sellards (1908) . . . and the two species would possibly
be regarded as conspecific if the fructifications of the Padgett
material were not known?? (p. 55). Sellards (1908) original
description of this Early Permian species is accompanied only by
line drawings, which show large, neuropteroid pinnules with an
unusually strong midvein that goes all the way to the pinnule
apex, relatively coarse lateral venation that curves steeply to meet
the margin, a cordate base without transition to small, free
pinnules, and entire margins. The pinnules are described as long
and sloping gradually to an obtuse apex. This certainly appears to
be similar to the non-divided pinnae/entire pinnules of Odontop-
teris readi. In addition, Sellards (1908) also describes and
illustrates, as O. reichiana, an Odontopteris of typical aspect in
the same flora as the large pinnules?the Banner City locality in
the Wellington shales (Wellington Formation). Based on the
illustrations, the pinnules of this plant are somewhat more angular
than those of O. readi. Yet, the entire suite from this locality
suggests the possibility of a mixoneurid odontopterid not unlike
O. readi, if not identical to it. Unless better material can be
obtained of both O. readi and N. permiana, this matter may be
impossible to resolve further.
Sellards? (1908) attribution of mixoneurid-like material to
Neuropteris brings to mind a more distant comparison between
Padgettia readi and similar neuropterids, in this instance
Macroneuropteris scheuchzeri, a specimen of which is illustrated
in Figure 2.3, and is important in the context of this paper because
of the nature of arthropod damage it demonstrates (Fig. 2.4).
Odontopteris readi is vaguely similar to M. scheuchzeri in several
features (illustrated in Figs. 1.10, 3, 4), including the large
pinnule size in many specimens, elongate pinnule shape,
generally much longer than wide, the bluntly acute apices, a
midrib that runs nearly to the pinnule apex with arching lateral
veins, and surface hairs (Laveine and Legrand, 2008). However,
the pinnules of O. readi (Fig. 1.10, 3, 4) can be far more elongate
than reported for any Macroneuropteris Cleal, Shute and Zodrow
species and narrow relative to their length. The pinnule midveins
are wide, more than 3 times wider than is typical of virtually any
medullosan, and are solid in appearance, not a bundle of
independent fine veins (Fig. 1.10, 3). The lateral veins are
relatively heavy and sparse (Fig. 5). In addition, the surface
ramentum is different from that of M. scheuchzeri, consisting of
variably dense, nearly triangular hairs directed mostly toward the
margins, rather than the fine, elongate, apically directed hairs
typical of M. scheuchzeri (Darrah, 1969; Cleal et al., 1990;
Laveine and Behlis, 2007).
DISCUSSION
The reassignment of Padgettia to Odontopteris reduces the
number of plant genera thought to be endemic to western North
America and provides another link with the Permian equatorial
regions of central Pangaea. In addition, the Ovofoligallites gall
is of particular importance when considering the expansion of
the galler insect functional feeding group during Permian time.
Thus, the reassignment of Padgettia readi to both a new host-
plant as well as to a new type of gall has implications that
extend beyond taxonomy and systematics, providing insight on
biogeography and the ecological context of plant?insect
associations during the late Paleozoic.
Although previously unrecognized in the Paleozoic (Larew,
1992; Scott et al., 1994), insect galls have been documented
FIGURE 8?Odontopteris readi (Mamay) Stull, DiMichele, and Chaney n. comb. Series of camera lucida drawings of the venation of proceeding from
neuropteroid pinnae with entire margins, progressively through neuropteroid pinnae with undulate to lobed margins to free pinnules. In all specimens, the
venation shows the same pattern of coarseness, and multiple, upwardly directed vein bifurcations. 1, USNM 544634; 2, USNM 544630; 3, USNM 544631; 4,
USNM 544633, Figure 4.1, 4.2; 5, USNM 544632, Figure 5.3, 5.4; 6, USNM 544636, Figure 6.1; 7, USNM 544633, Figure 4.1, 4.2; 8, USNM 544637, Figure
6.2; 9, USNM 544635, Figure 7.1, 7.2. All magnifications33.
228 JOURNAL OF PALEONTOLOGY, V. 87, NO. 2, 2013
from Pennsylvanian (Van Amerom, 1973; Labandeira and
Phillips, 1996, 2002) and especially Permian (Pant and
Srivastava, 1995; Banerjee and Bera, 1998; Beck and Laban-
deira, 1998; Labandeira, 1998, 2002, 2006a; Guleva and Raman,
2007; Labandeira and Allen, 2007; Labandeira et al., 2007;
Krassilov and Karasev, 2008; Prevec et al., 2009) deposits. This
recent flurry of documentation contrasts with older references
that mentioned unusual teratologies for plant tissues that were
unexplainable based on known plant anatomy (Florin, 1945;
Thomas, 1969), and before insect damage had become a widely
recognized phenomenon in late Paleozoic plants. Some of these
older reports now have been reinterpreted as galls (Van
Amerom, 1973; Labandeira and Allen, 2007), but also there
have been new descriptions of galls based on the discovery of
additional fossil deposits. In the Permian, several types of galls
now have been documented on a variety of plant hosts.
Examples include the cone-mimicking bud gall on shoots of
the conifer Walchia piniformis Sternberg (Florin, 1945;
Labandeira and Allen, 2007); small, circular galls on Glossop-
teris browniana Brongniart (Banerjee and Bera, 1998) and other
glossopterid leaves (Prevec et al., 2009); elongate, midrib galls
on the leaves of the callipterid Autunia conferta (Sternberg)
Kerp (Labandeira and Allen, 2007); smooth-walled lenticular
and tiny, irregular pock galls on the probable peltasperms
Vijanikopteris rigida Naugolnykh and Pursongia sp. of Russia
(Vasilenko, 2007; Krassilov and Karasev, 2009); and perhaps
blister-like, epidermal ??Runzelgallen?? on the medullosan
Odontopteris sp. from Germany (Potonie?, 1893). The compar-
atively large, blister-like Ovofoligallites padgetti galls on
Odontopteris readi foliage adds to the structural diversity of
this increasing number of distinctive Permian galls.
Several patterns are notable in the diversity of late Paleozoic
galls. First, is the broad galler plant-host shift from Pennsylva-
nian sphenopsid and pteridophyte taxa to Permian seed-plant
taxa, which undoubtedly reflected major changes in plant
community development, particularly in Euramerica. Climatic
changes during the Pennsylvanian?Permian transition brought to
the fore non-wetland vegetation types, dominated by seed plants
and characteristic of seasonally dry habitats (DiMichele et al.,
2009). Such seasonally dry floras had existed since at least the
Middle Pennsylvanian, if not earlier (Mapes and Gastaldo, 1989;
Broutin et al., 1990; DiMichele and Aronson, 1992; Plotnick et
al., 2010; Falcon-Lang et al., 2010). They grew largely in extra-
basinal settings (Pfefferkorn, 1980), or in basins during periods
of drier climate (Falcon-Lang and DiMichele, 2010; DiMichele
et al., 2010), associated with the glacial?interglacial fluctuations
that characterized this time interval (Fielding et al., 2008).
Consequently, these floras, dominated by seed plants, rarely
appeared in the fossil record until the lowland basins became
more persistently and seasonally dry, even during the wettest
time periods. Because these floras are so poorly known, it is
possible that the movement of insect gallers into them occurred
much earlier than presently understood from the known fossil
record.
The second pattern of note is the shift from organoid galls,
which induce anomalous growth affecting segments of the stem
and axial reproductive organs in Carboniferous plant hosts, to
histoid galls, which target specific tissues within leaves and
terminal branches in Permian plants. The similarity of the
distinctive damage pattern on O. readi with that found on the
Pennsylvanian plant Macroneuropteris scheuchzeri (DT97)
may, however, necessitate a re-evaluation of the associational
affinities of the earlier occurring, U-shaped, Pennsylvanian-age
damage (Mu?ller 1982; Labandeira and Beall, 1990) as a less
developed blister or vein gall. These gall-like, apparently
internally featureless structures (Fig. 2.3, 2.4), characteristically
occur on M. scheuchzeri across the equatorial belt of Euramerica
in a variety of environments, and may have originated in
relatively xeric environments.
The third pattern is the ecological movement of the galling
functional feeding group from Pennsylvanian plants such as
calamites and marattialean ferns that occupied wetland envi-
ronments, to a much broader range of seed-plant lineages during
the Permian. Seed plants were the most herbivorized group of
land plants that occupied better drained sites of the Permian, and
would have been an attractor to a variety of herbivorous insect
functional feeding groups, including gallers (Fernandes and
Price, 1988). The taphonomy of this transition is affected by the
same matters discussed above regarding the general galler host
shift. Evidently, the floral transition provided opportunities for
greater resource exploitation by emerging insect lineages of new
plant-host taxa and tissues, as shown in the broader fossil record
of galls. For the Permian, most of these new lineages were
homopterous Hemiptera, which diversified throughout the
Permian, including the Aphidoidea (currently, aphids, adelgids
and phylloxerids), Psylloidea (psyllids), both extant galler
groups, and the extinct Paleorrhyncha during the Early Permian
(Shcherbakov, 2000). By the end of the Permian, several extinct
lineages of the Cicadomorpha additionally were present
(Shcherbakov, 2000), some of which may have been gallers.
In addition, eriophyoid mites also occurred (Krantz and
Lindquist, 1979), as well as early holometabolous insect
lineages (Labandeira, 2011), possibly including gallers. There
also were holdover associations from the Pennsylvanian?
perhaps, for example, the galler of Macroneuropteris?that
survived into the Early Permian, in refugial habitats.
ACKNOWLEDGMENTS
GS acknowledges support from the Natural History Research
Experiences internship program, funded by the National Museum
of Natural History. WD acknowledges support from the NMNH
Small Grants Program and the SI Endowment Funds. F. Marsh
expertly drafted the figures. This is contribution 252 of the
Evolution of Terrestrial Ecosystems consortium at the National
Museum of Natural History. The authors thank J. Genise and an
anonymous reviewer for their suggestions to the manuscript.
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