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A new Carboniferous edaphosaurid
and the origin of herbivory
in mammal forerunners
Arjan Mann
1*, Amy C. Henrici
2, Hans‑Dieter Sues
1 & Stephanie E. Pierce
3
Herbivory evolved independently in several tetrapod lineages during the Late Carboniferous and
became more widespread throughout the Permian Period, eventually leading to the basic structure
of modern terrestrial ecosystems. Here we report a new taxon of edaphosaurid synapsid based on
two fossils recovered from the Moscovian‑age cannel coal of Linton, Ohio, which we interpret as an
omnivore–low‑bre herbivore. Melanedaphodon hovaneci gen. et sp. nov. provides the earliest record
of an edaphosaurid to date and is one of the oldest known synapsids. Using high‑resolution X‑ray
micro‑computed tomography, we provide a comprehensive description of the new taxon that reveals
similarities between Late Carboniferous and early Permian (Cisuralian) members of Edaphosauridae.
The presence of large bulbous, cusped, marginal teeth alongside a moderately‑developed palatal
battery, distinguishes Melanedaphodon from all other known species of Edaphosauridae and suggests
adaptations for processing tough plant material already appeared among the earliest synapsids.
Furthermore, we propose that durophagy may have provided an early pathway to exploit plant
resources in terrestrial ecosystems.
e origin of herbivory in amniotes is intimately linked with the origin of modern terrestrial ecosystem structure
and an expansion of niche exploitation1–3. Currently, it is thought that the ability to eciently process plant mate-
rial was well-established by the early Permian, with groups including diadectid stem-amniotes, captorhinid and
bolosaurid reptiles, as well as caseid and edaphosaurid synapsids being the rst tetrapod lineages to adopt this
feeding strategy4,5. Whereas most early Permian members of the two synapsid clades are interpreted as high-bre
herbivores, such as the iconic large-bodied Cotylorhynchus (Caseidae) and Edaphosaurus (Edaphosauridae),
virtually all Late Carboniferous representatives of these synapsid lineages are smaller faunivorous forms that
likely preyed on insects or other small animals6–8. erefore, there is an apparent lack of transitional Carbon-
iferous synapsids with less-specialized dietary preferences such as omnivory and low-bre herbivory, which
would bridge the gap between ancestral carnivores/insectivores and high-bre herbivores characteristic of the
Permian3,5 (Hotton etal., 1997; Reisz and Sues, 2000). Part of this gap may be explained by the still insuciently
documented Late Carboniferous fossil record of early amniotes, which has recently started to reveal unexpected
morphological and ecological diversity (e.g., 9,10).
Recently, a series of papers11,12 have used various modelling approaches to address the origins of herbivory
in tetrapods, ultimately predicting its appearance during the mid-Carboniferous shortly aer the origin of
amniotes. While quantitative approaches can be powerful, conrmation of the resulting hypotheses can only
be established through the discovery of new fossil material. Here we provide such a new record, reporting a
new species of edaphosaurid synapsid from the famous Late Carboniferous (Pennsylvanian: Moscovian) fossil
locality of Linton, Ohio. e vertebrate-bearing cannel coal from Linton, Ohio, likely represents an abandoned
channel or oxbow lake that was an allochthonous deposit of sapropelic plant material13. Although this deposit
is well known for being particularly rich in sh and amphibian remains14, terrestrial faunal components such as
amniotes are rarely found (e.g. 9,10,15). e new edaphosaurid material is preserved on two blocks of cannel coal
that collectively document a good portion of the skull, including the distinctive marginal dentition. Its dentition
reveals features indicative of omnivory or low-bre herbivory, placing this animal among the earliest known
tetrapod herbivores and certainly the oldest known synapsid herbivore. is new discovery also oers additional
insights into the early evolution of herbivory among tetrapods and their ecosystems, revealing the importance of
OPEN
1Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, MRC 121,
P.O. Box 37012, Washington, DC 20013-7012, USA. 2Section of Vertebrate Paleontology, Carnegie Museum
of Natural History, 4400 Forbes Avenue, Pittsburgh, PA 15213, USA. 3Museum of Comparative Zoology and
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA. *email:
MannArjan@si.edu
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durophagous specialists in establishing these early guilds. Furthermore, the presence of this taxon in the Middle
Pennsylvanian oers the earliest knownfossil evidence of divergent feeding strategies and niche expansion among
amniotes, which occurred during the ‘wet-phase’ or coal swamp environments of the mid-Late Carboniferous.
Methodology
Specimens used in this study are housed at the following institutions: American Museum of Natural History
(AMNH), New York, New York; Carnegie Museum of Natural History (CM), Pittsburgh, Pennsylvania; Field
Museum of Natural History (FMNH), Chicago, Illinois; Museum of Comparative Zoology at Harvard University
(MCZ), Cambridge, Massachusetts; and USNM, National Museum of Natural History, Washington, District of
Columbia. Fossils were photographed with a Canon EOS 6 with a Canon Macro EF 100mm lens. Digital photo-
graphs were processed and gures were assembled using Adobe Illustrator CS6. CM 93778 and CM 93779 were
microCT–scanned and digital peels were generated and rendered into stereolithography les at the University of
Texas at Austin CT scanning facility. Stereolithography les of the digital peels were 3D printed using a Stratasys
Connex500 Polyjet printer for observation. Processing and printing were conducted by 3DPhacktory in Toronto,
Ontario, Canada.
Systematic palaeontology.
Synapsida Osborn16.
Sphenacomorpha Ivakhnenko17 sensu Spindler etal.18.
Edaphosauridae Cope19.
Melanedaphodon hovaneci gen. et sp. nov.
Holotype. CM 93778, a natural mould of cranial remains comprising a partial right mandibular ramus, a right
pterygoid, the posterior part of a right maxilla, and the right jugal (Fig.1). Donated to CM by Scott McKenzie.
Referred material. CM 93779, a natural mold of partial skeleton comprising a right maxilla, a right pterygoid,
a le parietal, a le frontal, a parabasisphenoid, and postcranial bones (Fig.2). Collected by John Spina and
donated by Scott McKenzie.
Locality and horizon. Coal mine operated originally by the Ohio Diamond Coal Company at Linton in Saline
Township, Jeerson County, Ohio, U.S.A. (for details see Hook and Baird, 1986). Local cannel coal immediately
below the Upper Freeport coal, Allegheny Group. Middle Pennsylvanian (Moscovian).
Etymology. Generic name derived from the combination of the Greek ‘melanos’ meaning ‘black’ and ‘edaphon’
meaning ‘pavement’ and ‘odon’ meaning ‘tooth’, referring to the dense shagreen on the pterygoid and to the posi-
tion of the taxon among Edaphosauridae. e specic epithet hovaneci honors George Hovanec who generously
donated funds to facilitate the CT scanning of Linton fossils.
Diagnosis. An edaphosaurid synapsid with the following autapomorphies: long maxilla with 20 tooth posi-
tions; marginal dentition consisting of tall teeth with bulbous crowns that have pointed apices; and cutting
edges of tooth crowns without serrations. Further dierential diagnosis includes: an elongate pterygoid shared
with Ianthasaurus but not Edaphosaurus. Palatal shagreen with enlarged teeth on the anterior (palatal) ramus of
pterygoid shared with Ianthasaurus but not Edaphosaurus. Diers from Ianthasaurus butshares with Edapho-
saurus in having a tooth battery instead of enlarged single tooth row on the transverse ange of the pterygoid.
Diers from Gordodon in the absence of a diastema on the anterior end of the maxilla.
Comments. Spindler etal.20 briey redescribed the putative bolosaurid “Belebey” augustodunensis from the
early Permian (Artinskian) of France21 and reinterpreted it as a probable edaphosaurid. is reassessment was
based on the peculiar bulbous teeth of the holotype, which lacks the diagnostic ‘oset heel’ or ‘shelf ’ on the teeth
of bolosaurid parareptiles such as Belebey and Bolosaurus. Spindler etal.20 considered “Belebey” augustodunensis
a nomen dubium. We concur with their assessment and nd a close similarity between the teeth of this taxon and
those of the new edaphosaurid Melanedaphodon hovaneci. Both appear to possess distinct bulbous teeth with
cutting edges on the crowns. Although it is likely that “Belebey” augustodunensis is an edaphosaurid, perhaps
closely related to Melanedaphodon, additional material is needed in order to conrm this reassignment.
Statement of permission for study. All new fossil specimens reported in this paper (CM 93778 and
CM 93779) are permanently housed at the Carnegie Museum of Natural History. All specimens were studied
with permission from the Carnegie Museum of Natural History collections and curatorial sta (Matthew C.
Lamanna).
Description
e available material of Melanedaphodon hovaneci consists of skeletal remains of two individuals preserved on
separate blocks of cannel coal, CM 93778 and CM 93779 (Figs.1, 2). ese specimens both represent individu-
als at perhaps slightly dierent growth stages, as evident from the dierent dimensions of the maxilla, with CM
93779 being slightly smaller. e holotype, CM 93778, preserves most of the right mandibular ramus in lateral
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perspective, including the posterior portion of the dentary, the anterior part of the splenial, and the angular,
surangular, and articular (Fig.1). ere is also a well-preserved, disarticulated right pterygoid preserved in ven-
trolateral aspect, the posterior part of the right maxilla with teeth in medial view, and an almost complete right
jugal in lateral aspect. CM 93779 presents a nearly complete right maxilla in lateral aspect, the ventral aspect of
a crushed le pterygoid, a well-preserved le parietal in dorsal aspect, a probable le frontal, and the ventral
surface of the parabasisphenoid (Fig.1). e postcranial skeleton of CM 93779 is represented by a radius, a cau-
dal vertebra, and an incomplete dorsal vertebra (lacking most of the neural spine). Descriptions of the elements
below are based on both specimens.
e maxilla of Melanedaphodon is long with a moderately developed facial lamina that rises midway along the
maxilla at the level of the largest teeth in the tooth row (Figs.1, 2). It has a short posterior process. Anteriorly, a
small subnarial process likely contributed to the ventral margin of the external narial opening. e lateral surface
of the maxilla is slightly rugose and pierced by small neurovascular foramina. e more complete maxilla has
spaces for approximately 20 teeth (Fig.3).
e teeth of Melanedaphodon are distinctive in possessing bulbous tooth crowns with apical cutting edges
and tall roots. Proportional to the size of the maxilla, the teeth of Melanedaphodon appear much broader than
those of other known edaphosaurids. e exposed portion of the tooth bases or necks reveal a pattern of infold-
ing that indicates the presence of plicidentine9. e shape of the teeth is similar to that seen in Edaphosaurus,
but the crowns are more expanded and have well-dened apical carinae. Although there may be some variation
along the tooth row, some of the larger teeth on CM 93778 do not show clearly dened cutting edges but instead
appear to terminate in an oset apex, giving the appearance of a nozzle-like tip as in Edaphosaurus (Fig.3). ese
tooth apices also appear to bear enamel striations (Fig.3).
Figure1. Holotype of Melanedaphodon hovaneci gen. et sp. nov., CM 93778. (A) Photograph showing the
negative relief/natural mould. (B) Digital three-dimensional rendering of the CT data in positive relief.
(C) Interpretative drawing of specimen based on micro-CT data and original fossil. Top le corner shows
a reconstruction of the skull in lateral view with the preserved cranial elements highlighted. Anatomical
abbreviations: ang angular, art articu lar, d dentary, j jugal, mx maxilla, pt pterygoid, sur surangular, sp splenial.
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e right jugal, present on CM 93778, is elongate and mediolaterally narrow, with the Y-shaped posterior end
forming the anteroventral margin of the temporal fenestra and ventral margin of the orbit (Fig.1). e dorsal
process of the jugal, which forms part of the postorbital bar, appears forked but this may be the result of crush-
ing. e anterior portion of the jugal is thin and tapers to a point that would havecontacted the dorsal edge of
the posterior process of the maxilla. Overall, the jugal is very similar to that of other edaphosaurids including
Glaucosaurus, Gordodon, and species of Edaphosaurus22,23.
CM 93779 preserves the le parietal (Fig.2). e parietal is large, plate-like, and rectangular with emargina-
tions and processes for the contacts with adjacent elements. Anteromedially, there appears to be an area that was
overlapped by the frontal. Anterolaterally, the parietal bears a large embayment for contact with the postfrontal.
Medially, there is a large circular excavation near the centre of the element, which formed part of the margin of
a large pineal foramen. Posterolaterally, the parietal is embayed for contact with the supratemporal. Posteriorly,
a gentle emargination receives both the tabular and part of the postparietal. Overall, the parietal morphology
is not as derived as that of Edaphosaurus where the lateral portion of the parietal is ‘free’. Instead, the parietal
morphology is similar to that of early-diverging sphenacomorphs and most similar to that of Ianthasaurus
among edaphosaurids. ere is also a bone that appears to be the right size and shape for a frontal, but is mostly
obscured by the overlapping parietal, preventing denite identication.
Both the right pterygoid of CM 93778 and le pterygoid of CM 93779 are exposed in primarily ventral view
(Figs.1, 2). e pterygoid has a long anterior ramus similar to those in most species of Edaphosaurus22,24,25. Its
anterior ramus bears at least three distinct elds of palatal teeth, which appear to be emplaced atop shallow
bosses. e anteriormost teeth are slightly enlarged as in Ianthasaurus26. e microCT scans reveal thatthe palatal
teeth are slightly bulbous and have pointed apices. e dorsoventrally shallow transverse ange on the pterygoid
bears a distinct, dense patch of teeth. e structure of this ange appears more derived than the condition seen
in Ianthasaurus and more similar to that of Edaphosaurus, perhaps representing an intermediate condition. e
quadrate ramus of the pterygoid is attened, tall, and fan-shaped posteriorly, similar to that of Ianthasaurus26.
Figure2. Melanedaphodon hovaneci gen. et sp. nov., CM 93779. (A) Photograph showing the negative relief/
natural mold. (B) Digital three-dimensional rendering of the CT data in positive relief. (C) Interpretative
drawing based on the CT scans and original fossil. Anatomical abbreviations: cv caudal vertebra, f frontal,
mx maxilla, p parietal, pas parabasisphenoid, pt pterygoid, rad radius, dv dorsal vertebra.
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e only braincase element condently identied for Melanedaphodon is the parabasisphenoid exposed in
dorsal view on CM 93779 (Fig.2). is compound bone is robust and has a long cultriform process. e cultri-
form process bears a attened extent of bone ventrally, which may be part of a crista ventrolateralis. ere are
two moderately developed basipterygoid processes, which undoubtedly would be more prominent ventrally. e
posterior region of the parabasisphenoid is roughly triangular in outline and expanded posteriorly. Overall, the
structure of the parabasisphenoid appears similar to that in other basal sphenacomorphs.
A nearly complete right mandibular ramus is preserved in CM 93778 in lateral view, missing only the anterior
ends of the dentary and splenial (Fig.1). e dentary appears shallow anteriorly but increases in depth posteriorly.
A low coronoid process extends posteriorly from the posterodorsal end of the dentary. On the lateral surface
of the dentary, close to the tooth row, there is an evenly spaced series of moderately-sized foramina that each
open into a posteriorly directed sulcus. ese openings likely transmitted both blood vessels and branches of the
inferior alveolar nerve. e dentary preserves a partial tooth row comprising approximately 14 tooth spaces with
12 well-preserved teeth in place. e teeth are identical in morphology to those of the upper jaw but appear to be
slightly smaller in size. A thin, elongated partial splenial embraces the ventral surface of the dentary. Posterior
to the dentary, the lower jaw gently bows outward in a manner similar to that in Gordodon27. e surangular
and angular meet the dentary along slightly interdigitated sutures. e surangular is long and gently tapers pos-
teriorly. e lateral surface of the angular is larger than that of the surangular. e angular is massive, long, and
quadrangular. Anteriorly, it has a process that extends along the dentary ventrally and appears to have reached
the splenial. e articular has only a slight, irregularly shaped exposure in lateral view. e suture between the
articular and angular is somewhat interdigitated.
CM 93779 preserves two vertebrae and a limb bone (Fig.2). One vertebra appears to be a small, cylindri-
cal distal caudal and the other is a dorsal lacking most of its neural spine. e dorsal vertebra is very similar to
those of other edaphosaurids including Edaphosaurus, Gordodon, and Ianthasaurus27,28. e centrum appears
hourglass-shaped with a moderately developed, rounded ventral keel. e neural arch is robust with prominent
pre- and postzygapophyses exposed in ventrolateral aspect. e preserved portion of the neural spine, separated
from the centrum, slightly tapers distally. e limb bone has a small rod-like sha and moderately developed
diaphyses; it possibly represents a radius. It bears general resemblance to the radii of early ‘pelycosaurs’ (e.g.,
ophiacodontids28).
Phylogenetic relationships
We explored the phylogenetic relationships of Melanedaphodon hovaneci using two distinct character–taxon
matrices. In order to determine the large-scale phylogenetic relationship of Melanedaphodon hovaneci within
amniotes we used the recent matrix of Ford and Benson29 (see Supplementary Information, S1, for matrix). Fol-
lowing this, we used a modied version of the character-taxon matrix by Spindler etal.20 (see Supplementary
Information, S2, for matrix), which is the most up-to-date data matrix for assessing the interrelationships of
Figure3. (A, C) Photograph and digital three-dimensional rendering of the maxilla of CM 93779. Digital
render shows the positive relief and true anatomy of CM 93779 revealing 16 wide-based teeth with bulbous tips.
(B, D) Photograph and digital three-dimensional rendering of the maxilla of CM 93778. Digital render shows
the positive relief and true anatomy of the medial surface of the maxilla on CM 93778, revealing the bulbous
tooth tips from a dierent perspective. (E) Maxilla of a specimen of Edaphosaurus sp. (USNM PAL 299844),
showing teeth with bulbous crowns with nozzle-like apices. (F) Reconstruction of a tooth of Melanedaphodon
hovaneci gen. et sp. nov., highlighting the bulbous crown. Anatomical abbreviations: a.car apical carina,
e. enamel uting, plic plicidentine.
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Edaphosauridae. For this analysis, in addition to our new taxon, we also added the recently described Gordodon27
as well as limited our OTU sample to taxa that were reasonably well-diagnosed and not solely based on highly
fragmentary postcranial material. In both analyses Melanedaphodon was coded as a composite of both specimens
to achieve the most complete character sampling.
For the rst analysis, using the matrix of Ford and Benson29, we conducted a parsimony analysis using PAUP
soware v4.0b1030 with Gephyrostegus designated as the outgroup. e heuristic search option was selected, with
Maxtrees set at 10,000 and set to automatically increased by 100. All characters were treated as equally weighted,
and multistate taxa were treated as polymorphic. Ambiguous character states were resolved using the ACC TRA N
setting. Indices of goodness of t of the character data to the topology (e.g., consistency index [CI], homoplasy
index [HI]), retention index [RI], rescaled consistency index [RC]) were calculated in PAUP. To assess support
of internal nodes, bootstrap values were calculated using the “fast” stepwise addition option. e parsimony
analysis recovered 18 most parsimonious trees (MPT), each with 1619 steps (CI = 0.255; HI = 0.772; RI = 0.593;
RC = 0.151). e strict consensus of the results recovered Melanedaphodon as an edaphosaurid synapsid, speci-
cally as sister taxon to Edaphosaurus to the exclusion of Ianthosaurus (Fig.4A). e topology otherwise remain
consistent to what is reported in Ford and Benson29.
Figure4. (A) Strict consensus of the results of the parsimony analysis of early amniotes based on Ford and
Benson29. (B) Strict consensus of the results of the parsimony analysis of Edaphosauridae based on Spindler
etal.20. (C) Majority-rule consensus of the results of the parsimony analysis of Edaphosauridae based on
Spindler etal.20. In all analyses, Edaphosauridae is demarcated by a light green bracket and Melanedaphedon
hovaneci gen. et sp. nov. is highlighted in dark green. In the strict consensus trees, bootstrap values greater than
50% are indicated above nodes.
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Next, using the matrix of Spindler etal.20, we performed a parsimony analysis using PAUP soware v4.0b1030
with the early ophiacodontid Archaeothyris specied as the outgroup. We used the branch-and-bound search
option. Maxtrees were set at 10,000 and automatically increased by 100, all characters were equally weighted,
and all multistate taxa were treated as polymorphic. All ambiguous character states were resolved using the
ACC TRA N setting. Indices of goodness of t of the character data to the topology were calculated in PAUP.
To assess support of internal nodes, bootstrap values were calculated using the full heuristic search option
with 100 replicates. e parsimony analysis recovered 11 most parsimonious trees (MPT), each with 120 steps
(CI = 0.683; HI = 0.317; RI = 0.819; RC = 0.560). e strict consensus of the results recovered Melanedaphodon
within a polytomy of derived edaphosaurids comprising Glaucosaurus, Gordodon, Lupeosaurus, and a clade of
Edaphosaurus boanerges, E. cruciger, E. novomexicanus, and E. pogonias (Fig.4B). is polytomy is recovered as
the sister clade to the early edaphosaurid Ianthasaurus. Our analysis found Ianthosaurus as the basalmost member
of Edaphosauridae. e Majority–rule consensus of the results recovered a clade consisting of Melanedaphodon
as sister-taxon to Lupeosaurus to the exclusion of Glaucosaurus (Fig.4C). is clade is recovered a sister-taxon
to Edaphosaurus and its species to the exclusion of Gordodon. Again, Ianthosaurus is recovered as the earliest
diverging edaphosaurid. Bootstrap values supporting these relationships are shown above nodes in Fig.4.
Discussion
It has repeatedly been hypothesized that herbivory arose independently in several tetrapod clades around the
Permo-Carboniferous boundary and became more widespread during the Permian2,3,5. e earliest tetrapod
groups adopting herbivory—diadectids, edaphosaurids, and captorhinids—have their origins in the Late Car-
boniferous but did not diversify until the early Permian (Fig.5). High-bre herbivory is thought to have evolved
in these clades based on suites of morphological characters correlated with herbivory in extant reptiles and
Figure5. Time-calibrated phylogeny showing the origins of major clades with herbivory across the Permo-
Carboniferous. Herbivorous/omnivorous feeding habits among tetrapods are shown to originate in the
Late Carboniferous with Melanedaphodon as the oldest known example. However, herbivory becomes
more widespread among tetrapods in the Early Permian with a greater volume of high-bre herbivores.
Melanedaphodon is indicated with turquoise sunburst pattern. Dietary inferences are colour-coded (see gure
legend).
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mammals. ese herbivorous adaptations include the presence of occluding teeth or tooth batteries (marginal
and/or palatal), tooth-wear patterns, modications of the jaw apparatus for oral processing of plant material,
and expansion of the thorax and abdomen (as documented by the dimensions of the ribcage) to accommodate
large guts housing microbial endosymbionts to facilitate digestion of cellulose2,3,5.
e Moscovian-age Melanedaphodon is the oldest known edaphosaurid synapsid, and unlike the late Kasimo-
vian-age edaphosaurid Ianthasaurus, which was likely a carnivore, it already presents a craniodental structure
more similar to that of Edaphosaurus25(Fig.5). e pterygoid of Melanedaphodon shows a poorly developed
transverse ange that lacks the single large tooth row found in Ianthasaurus. Instead, the entire pterygoid (and
likely the whole palate) is covered by a moderately-developed tooth battery, which appears intermediary towards
the condition seen in Edaphosaurus (Fig.6). Due to preservation, there is as yet no information regarding wear
on the palatal teeth of Melanedaphodon, but it is likely that the palatal dentition could have served in processing
plant material, though perhaps not as extensively as in the high-bre herbivore Edaphosaurus28 (Fig.6). e
large and bulbous marginal teeth are is reminiscent of a tooth morphotype more oen associated with feeding
on hard-shelled invertebrate material such as arthropods or molluscs (durophagy) or on seeds (granivory)31,32.
Furthermore, similar types of bulbous teeth can be found in present-day squamates (e.g., Tiliqua rugosa, Tiliqua
multifasciata, Dicrodon guttulatum, Tupinambis rufescens) that also consume plant material and are varying
degrees of omnivorous or herbivorous31–36. In Melanedaphodon, the combination of the structure of the marginal
teeth alongwith the palatal dentition suggests that plant material made up a considerable portion of the diet.
However, for Melanedaphodon, we cannot eliminate the possibility that it fed on invertebrates in addition to
plant material; therefore, it is best considered an omnivore–low-bre herbivore that was capable of exploiting
plant resources.
Melanedaphodon provides the oldest known record of probable omnivory–low-bre herbivory in amniote evo-
lution, and thus provides novel data for our understanding when herbivory originated (Fig.5). Melanedaphodon
also reveals that herbivory in synapsids signicantly predated the origin of this feeding strategy in the conven-
tional conguration of traditionally recognized reptiles (i.e., without the addition of recumbirostrans sensu Pardo
etal.37) (Fig.5). Among reptiles, early-diverging captorhinid eureptiles evolved dierent strategies to expand
their feeding habits, such as the early Permian Captorhinus5 that had single or at most a few longitudinal rows of
teeth in the maxilla and dentary and have long been considered omnivorous. Larger, more derived, captorhinids
show craniodental features that suggest high-bre herbivory including broad maxillae and dentaries with up to
11 longitudinal rows of isodont teeth, which show tooth wear38. e bulbous marginal teeth of Melanedaphodon
provide a previously unrecognised dental morphotype among the earliest synapsids39,40, being clearly adapted
for feeding on tough, resistant food stus. Whereas such teeth are rare among early synapsids, similar types of
bulbous teeth are present in other Permo-Carboniferous groups of tetrapods, including the possible captorhinid
reptile Opisthodontosaurus, but more frequently among recumbirostran ‘microsaurs’. Recumbirostrans, which
have recently been reinterpreted as a fossorially adapted group of early reptiles9,37,41–44, apparently present the
greatest dental variety among early tetrapods, comparable to that of present-day squamates45. Dentitions adapted
for durophagy in recumbirostrans appear in the fossil record as early as the Bashkirian (~ 318Ma)46,47. It is
possible that durophagous feeding habits provided an alternate pathway to herbivory with bulbous teeth pro-
viding an exaptation to facilitate oral processing of the great variety of tougher plant food available in the Late
Pennsylvanian. Particularly, some groups of ‘microsaurs’ such as pantylids have apparently developed similar
Figure6. Comparative palatal reconstructions of three edaphosaurids. (A) Palate of the Late Carboniferous
(Kasimovian) early edaphosaurid, Ianthasaurus hardestiorum, from Garnett, Kansas (based on observations of
ROM 59933). (B) Palate of the Late Carboniferous (Moscovian) edaphosaurid, Melanedaphodon hovaneci gen.
et sp. nov., from Linton, Ohio. (C) Palate of the Early Permian edaphosaurid, Edaphosaurus boanerges, from
Archer County, Texas25. Maxilla and pterygoid are highlighted in green and yellow, respectively.
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palatal structures to those of edaphosaurids, but with durophagous tooth morphology on the palatal and mar-
ginal dentition48,49. Such teeth would have been suited for processing roots and tubers, seeds or megaspores,
but additional research into the systematics and anatomy of ‘microsaurs’ is needed to conrm this hypothesis.
Conclusions
Melanedaphodon hovaneci gen. et sp. nov., fromthe Middle Pennsylvanian, Linton, Ohio, provides the old-
est known record of probable omnivory–low-bre herbivory in amniote evolution, and oers new anatomical
data in understanding when and how herbivorous adaptations arose (Fig.7). Melanedaphodon is the oldest
knownoccurrence of an edaphosaurid, rmly establishing the presence of this clade in the Moscovian (~ 307Ma;
Fig.5). Finally, the bulbous marginal dentition of Melanedaphodon represents a previously unrecognised dental
morphotype among the earliest synapsids, indicating some form of durophagous omnivory may have provided
an intermediate condition between carnivory and high-bre herbivory.
Data availability
All phylogenetic data used in this study, including the matrices, are provided in the accompanying Supplementary
Materials. CT scans of CM 93778 and CM 93779, only provide surface details due to the nature of preservation in
cannel coal. Stereolithographic les of the scans can be provided upon request to the corresponding author. is
published work and the nomenclatural acts it contains have been registered in ZooBank, the proposed online
registration system for the International Code of Zoological Nomenclature (ICZN). e ZooBank LSIDs (Life
Science Identiers) can be resolved and the associated information viewed through any standard web browser
by appending the LSID to the prex http:// zooba nk. org/. e LSIDs for this publication are: urn:lsid:zoobank.
org:pub:5EF205BE-1C54-4AA6-9F13-C0F8D0EEC161 (article); urn:lsid:zoobank.org:act:85C2C125-C717-4519-
B82F-9226D9D9F51B (genus); and urn:lsid:zoobank.org:act:E57B0D8C-B076-4B73-AF37-602C33DCC09C
(species).
Received: 22 November 2022; Accepted: 27 February 2023
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Acknowledgements
We thank David Berman for facilitating access to collections at the Carnegie Museum of Natural History. We
thank Robert Hook for providing useful discussion on the anatomy, taxonomy, and stratigraphic distribution
of Permo-Carboniferous synapsids. We thank Christian Kammerer for access to comparative CT data of Glau-
cosaurus. We are indebted to George Hovanec who generously provided funding for CT scanning of the Linton
fossils presented in this paper and several forthcoming research projects. Finally, we thank Jessica Maisano and
Matthew Colbert for handling the microCT–scanning of CM 93778 and CM 93779, we acknowledge support of
the UTCT lab by NSF grant EAR-1762458.
Author contributions
A.M. conceived the study, conducted analyses, and wrote the initial dra. A.M., A.C.H., H.-D.S. and S.E.P. wrote
and edited the paper.
Competing interests
e authors declare no competing interests.
Additional information
Supplementary Information e online version contains supplementary material available at https:// doi. org/
10. 1038/ s41598- 023- 30626-8.
Correspondence and requests for materials should be addressed to A.M.
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