Kenomagnathus

Last updated

Kenomagnathus
Temporal range: Late Pennsylvanian
~304  Ma
O
S
D
C
P
T
J
K
Pg
N
Kenomagnathus-fig1-fossil.jpg
Holotype fossil ROM 43608
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Sphenacodontia
Genus: Kenomagnathus
Spindler, 2020
Species:
K. scottae
Binomial name
Kenomagnathus scottae
Spindler, 2020

Kenomagnathus (meaning "gap jaw", in reference to the diastema in its upper tooth row) is a genus of synapsid belonging to the Sphenacodontia, which lived during the Pennsylvanian subperiod of the Carboniferous in what is now Garnett, Kansas, United States. It contains one species, Kenomagnathus scottae, based on a specimen consisting of the maxilla and lacrimal bones of the skull, which was catalogued as ROM 43608 and originally classified as belonging to "Haptodus" garnettensis . Frederik Spindler named it as a new genus in 2020.

Contents

Discovery and naming

Norman Newell discovered a fossil locality near Garnett, Kansas, United States in 1931, belonging to the Rock Lake Member of the Stanton Formation. [1] Around 1932, Henry Lane and Claude Hibbard had collected a variety of animal and plant fossils from the locality. Among these were skeletons of Petrolacosaurus , which were subsequently described in 1952 by Frank Peabody. Hoping to find more material, a field team from the University of Kansas Natural History Museum conducted further excavations in 1953 and 1954; they found trackways, coelacanth fish, several additional Petrolacosaurus skeletons, and "pelycosaur" (early-diverging synapsid) fossils representing three genera. One of these was a partial skeleton that distinctly differed from the others; when Peabody reported on these discoveries in 1957 paper, he observed that the skeleton was of a primitive sphenacodontid, but deferred its description to a later time. [2]

Interpretative drawing of the holotype ROM 43608 Kenomagnathus-fig2-drawing.jpg
Interpretative drawing of the holotype ROM 43608

In 1965, Robert Carroll found another articulated partial skeleton in the same locality. Philip Currie attributed this skeleton to the primitive sphenacodontid of Peabody in 1977, and recognized it as a new species of Haptodus , which he named Haptodus garnettensis . [3] However, up until that point, all specimens of H. garnettensis were either badly crushed or immature. Throughout the 1980s, a number of additional specimens were discovered at the locality, including adult and subadult specimens. This allowed Michel Laurin to identify distinguishing characteristics for H. garnettensis and to incorporate it into a phylogenetic analysis, which found it to be outside the Sphenacodontidae. He published these results in 1993. [4] Among the additional specimens was a partial skull consisting of a left maxilla and lacrimal, which were catalogued in the Royal Ontario Museum (ROM) as ROM 43608. [5]

Analyses of specimens assigned to H. garnettensis by Frederik Spindler and colleagues later suggested that there was not one but between four and six distinct taxa among them, which primarily differed in their jaws and teeth. They also recognized differences between "H." garnettensis and the type species of Haptodus, H. baylei. [6] In a 2013 conference presentation, Spindler, Kirstin Brink, and Graciela Piñeiro suggested that this variation was based on diet, making these taxa a prehistoric analogue of Darwin's finches. [7] Spindler formally named ROM 43608 as belonging to a new genus and species in 2020, which he named Kenomagnathus scottae. The generic name Kenomagnathus is derived from the Greek words κένωμα ("gap") and γνάθος ("jaw"), referencing the diastema (gap) in its tooth row. Meanwhile, the specific name scottae honours Diane Scott, a fossil preparator at the University of Toronto Mississauga who "greatly helped with teaching and specimen handling", inspired Spindler's research, and further prepared the specimen in 2013. [5]

Description

Skull reconstruction of Kenomagnathus (top right) compared to other Garnett "haptodontines" Kenomagnathus-fig4-recon.jpg
Skull reconstruction of Kenomagnathus (top right) compared to other Garnett "haptodontines"

Among close relatives, Kenomagnathus can be distinguished by its tall snout, judging by the maxilla and especially the lacrimal. The projection at the front of the lacrimal would have formed a large part of the rear border of the bony nostrils. [5] In "H." garnettensis, the lacrimal still contributed to the border, but with a narrow projection. [6] From below, the upward projection at the front of the maxilla would also have contributed to the border of the nostrils, but the angle of this projection differed from "H." garnettensis. The height of the lacrimal, which bordered the front of the eye socket, also implies that Kenomagnathus had large eyes. [5]

The tooth-bearing bottom margin of the maxilla in Kenomagnathus was more convex than "H." garnettensis, and is unique in that it lacked a concave region (or "precanine step"). Another distinguishing characteristic is the diastema, a toothless region spanning the width of three teeth at the front of the maxilla, where the bone noticeably thinned and could not have borne tooth sockets. Behind the diastema were two precanine teeth, two large canine teeth, and at least fourteen post-canine teeth (eleven being preserved). There were two weakly thickened regions, or buttresses, on the maxilla, with one above the canines and one further back. Due to the shortness of the maxilla, the canines were located further forward than in close relatives. Like "H." garnettensis, Kenomagnathus had tall and nearly straight teeth, with striations on the inner surfaces of the teeth reaching the tips, but those of Kenomagnathus were more slender and blunter at the tip. [5] [6]

Classification

Life restoration Kenomagnathus DB.jpg
Life restoration

In 2020, Spindler identified three characteristics that placed Kenomagnathus in the Sphenacodontia: the blunt teeth, the convex bottom margin of the maxilla, and the height of the lacrimal and the upward projection of the maxilla. However, based on the contribution of the lacrimal to the border of the bony nostrils, Kenomagnathus was excluded from the more restrictive group Sphenacodontoidea. Within this evolutionary grade of "haptodontine" sphenacodontians, the fragmentary nature of specimens has complicated the resolution of their relationships. This is exacerbated by the fact that many "haptodontines" are very similar to each other save for differences in their teeth and skull proportions. [5]

For his 2015 thesis, Spindler conducted a preliminary phylogenetic analysis of "haptodontines", based on a new set of characteristics that he assembled to resolve their relationships. After defining the specimens associated with "H." garnettensis as opposed to Kenomagnathus and a taxon he named "Tenuacaptor reiszi", he could not resolve whether Kenomagnathus or Ianthodon was more basal (less specialized). Removing "Tenuacaptor" produced a more derived (more specialized) position for both Kenomagnathus and "H." garnettensis inside the Sphenacodontia. Phylogenetic trees illustrating both phylogenetic hypotheses are shown below. [6]

Topology A: All genera and characteristics [6]

Eupelycosauria

Topology B: With "Tenuacaptor" and some tooth-based characteristics removed [6]

Eupelycosauria

Evolutionary history

Closeup showing the diastema of Kenomagnathus Kenomagnathus-fig3-closeup.jpg
Closeup showing the diastema of Kenomagnathus

Modern mammals (except whales) commonly exhibit heterodont teeth, or teeth of several different types. [8] Among the extinct relatives (stem group) of mammals, there is a gradient from animals with isodont (uniform) teeth to animals with heterodont teeth, associated with the development of distinct "zones" along the tooth row. Canine-like teeth — double canines like that of Kenomagnathus in particular — are common among basal synapsids and also other basal amniotes, along with the enlargement of the first premaxillary tooth at the front of the skull. [9] There is a morphological gap between basal synapsids like "Haptodus" garnettensis, which have precanine teeth but less tooth variation over all, and therapsids (which are closer to mammals), which have no precanine teeth, only one set of canines, and more subtle tooth variation. Precanine teeth are often replaced by a large diastema in therapsids. [5] [10]

Kenomagnathus had both precanine teeth and a diastema, which fills the gap between basal synapsids and therapsids to some extent. It reflects what would have been an ongoing transition, which other stem-mammals with diastemata would also have gone through. Spindler hypothesized that the diastema initially developed as a consequence of the maxilla and premaxilla being angled against each other by the precanine step, which would have prevented the precanine teeth from growing longer; this is seen as an "initial diastema" in "H." garnettensis, Ianthasaurus, and Ianthodon. This would have allowed the corresponding canines on the lower jaw to grow longer and fill the gap, which in turn would have led to a full diastema. However, Spindler also noted that the relationship between the development of the precanine step, tooth loss, and the diastema was unclear, and that the feeding styles of these animals may also have had an effect. [5]

Paleobiology

The skull of Kenomagnathus has been compared to Tetraceratops Tetraceratopsinsignis1DB.jpg
The skull of Kenomagnathus has been compared to Tetraceratops

Spindler likened Kenomagnathus to the enigmatic synapsid Tetraceratops , as both had short faces, large eyes, and a diastema in their jaws. While this implies that the skulls of both were specialized for food processing, Spindler noted that further comparisons "cover a wide range of possibilities". In particular, Tetraceratops was highly specialized; the diastema in Tetraceratops does not line up with the position of the lower canines, but is located slightly behind it, and the first premaxillary tooth would have jutted out from the front of the jaws when they were closed. Spindler suggested in 2019 that Tetraceratops was durophagous (i.e. it fed on hard-shelled prey), based primarily on its teeth. [11] He inferred a similar lifestyle for Kenomagnathus based on its tall skull in 2020, and suggested that the diastema of Kenomagnathus may have been covered by rigid tissue, against which a potentially enlargened lower tooth would have pressed to crush prey items. [5]

Paleoecology

Haptodus garnettensis.jpg
Ianthasaurus223DB.jpg
Petrolacosaurus BW.jpg

The rocks that Kenomagnathus was found in originate from the base of the Rock Lake Member of the Stanton Formation, which is in turn part of the Lansing Group. These rocks have been assigned to the Late Pennsylvanian subperiod of the Carboniferous period, specifically near the transition between the Kasimovian and Gzhelian ages around 304 Ma (million years ago). [12] [13]

At the Garnett locality, the base of the Rock Lake Member consists of carbonaceous calcareous mudstone (i.e. mudstone containing organic matter and calcium carbonate) that is moderately layered and dark greyish-brown in color. [1] Plant fossils in these rocks are dominated by the conifers Lebachia and Walchia , along with smaller plants like the ferns Dichophyllum , the seed ferns Alethopteris , Neuropteris , and Taeniopteris , the cycad Spermopteris , the horsetail Annularia , and the gymnosperm Cordaites . [14] [15] At the top of these rocks is a layer of marine bivalve fossils measuring 2–5 cm (0.8–2 in) thick, which were likely deposited at high tide. Collectively, this implies that Kenomagnathus lived on a coastal plain in a coniferous forest. Towards the top of the Rock Lake Member, the rock layers become more irregular, and fossils of land animals and plants are increasingly replaced by fossils of marine invertebrates, implying that estuarine waters gradually flooded the region as sea levels rose. [1] [16]

The Garnett locality has produced several basal synapsids, including the "haptodontines" Kenomagnathus, "H." garnettensis, "Tenuacaptor", and Ianthodon; [6] the edaphosaurid Ianthasaurus ; the enigmatic synapsid Xyrospondylus , which may also be an edaphosaurid; [17] an undescribed member of Ophiacodontidae that has been assigned to Ophiacodon and Clepsydrops ; and possibly another sphenacodontian. [18] Petrolacosaurus is the most common reptile, known from nearly fifty specimens; a possible member of the Protorothyrididae is also known from tracks. Only the amphibian Actiobates is known, [19] while the fish consist of the coelacanth Synaptotylus , a larger coelacanth, and xenacanthid sharks. Invertebrates include insects like Euchoroptera and Parabrodia ; the scorpion Garnettius ; the bivalves Myalinella , Sedgwickia , and Yoldia ; the brachiopods Composita , Lingula , and Neospirifer ; and bryozoans, serpulid worms, trilobites, crinoids, sea urchins, rugosan corals, and sponges. [1] [20] Spindler speculated that Kenomagnathus may have fed on bivalves. [5]

Related Research Articles

<i>Galesaurus</i> Extinct genus of cynodonts from the Triassic of South Africa

Galesaurus is an extinct genus of carnivorous cynodont therapsid that lived between the Induan and the Olenekian stages of the Early Triassic in what is now South Africa. It was incorrectly classified as a dinosaur by Sir Richard Owen in 1859.

<span class="mw-page-title-main">Sphenacodontidae</span> Extinct family of synapsids

Sphenacodontidae is an extinct family of sphenacodontoid synapsids. Small to large, advanced, carnivorous, Late Pennsylvanian to middle Permian "pelycosaurs". The most recent one, Dimetrodon angelensis, is from the latest Kungurian or, more likely, early Roadian San Angelo Formation. However, given the notorious incompleteness of the fossil record, a recent study concluded that the Sphenacodontidae may have become extinct as recently as the early Capitanian. Primitive forms were generally small, but during the later part of the early Permian these animals grew progressively larger, to become the top predators of terrestrial environments. Sphenacodontid fossils are so far known only from North America and Europe.

<span class="mw-page-title-main">Sphenacodontia</span> Clade of synapsids

Sphenacodontia is a stem-based clade of derived synapsids. It was defined by Amson and Laurin (2011) as "the largest clade that includes Haptodus baylei, Haptodus garnettensis and Sphenacodon ferox, but not Edaphosaurus pogonias". They first appear during the Late Pennsylvanian epoch. From the end of the Carboniferous to the end of the Permian, most of them remained large, with only some secondarily becoming small in size.

<span class="mw-page-title-main">Eupelycosauria</span> Clade of synapsids

Eupelycosauria is a large clade of animals characterized by the unique shape of their skull, encompassing all mammals and their closest extinct relatives. They first appeared 308 million years ago during the Early Pennsylvanian epoch, with the fossils of Echinerpeton and perhaps an even earlier genus, Protoclepsydrops, representing just one of the many stages in the evolution of mammals, in contrast to their earlier amniote ancestors.

<i>Tetraceratops</i> Extinct genus of synapsids

Tetraceratops insignis is an extinct synapsid from the Early Permian that was formerly considered the earliest known representative of Therapsida, a group that includes mammals and their close extinct relatives. It is known from a single 90-millimetre-long (3.5 in) skull, discovered in Texas in 1908. According to a 2020 study, it should be classified as a primitive non-therapsid sphenacodont rather than a genuine basal therapsid.

<i>Haptodus</i> Extinct genus of synapsids

Haptodus is an extinct genus of basal sphenacodont, member of the clade that includes therapsids and hence, mammals. It was at least 1.5 metres (5 ft) in length. It lived in present-day France during the Early Permian. It was a medium-sized predator, feeding on insects and small vertebrates.

<i>Secodontosaurus</i> Extinct genus of synapsids

Secodontosaurus is an extinct genus of "pelycosaur" synapsids that lived from between about 285 to 272 million years ago during the Early Permian. Like the well known Dimetrodon, Secodontosaurus is a carnivorous member of the Eupelycosauria family Sphenacodontidae and has a similar tall dorsal sail. However, its skull is long, low, and narrow, with slender jaws that have teeth that are very similar in size and shape—unlike the shorter, deep skull of Dimetrodon, which has large, prominent canine-like teeth in front and smaller slicing teeth further back in its jaws. Its unusual long, narrow jaws suggest that Secodontosaurus may have been specialized for catching fish or for hunting prey that lived or hid in burrows or crevices. Although no complete skeletons are currently known, Secodontosaurus likely ranged from about 2 to 2.7 metres (7–9 ft) in length, weighing up to 110 kilograms (250 lb).

<i>Eothyris</i> Extinct genus of synapsids

Eothyris is a genus of extinct synapsid in the family Eothyrididae from the early Permian. It was a carnivorous insectivorous animal, closely related to Oedaleops. Only the skull of Eothyris, first described in 1937, is known. It had a 6-centimetre-long (2.4-inch) skull, and its total estimated length was 30 centimetres. Eothyris is one of the most primitive synapsids known and is probably very similar to the common ancestor of all synapsids in many respects. The only known specimen of Eothyris was collected from the Artinskian-lower.

<i>Euchambersia</i> Extinct genus of therapsid from Late Permian South Africa

Euchambersia is an extinct genus of therocephalian therapsids that lived during the Late Permian in what is now South Africa and China. The genus contains two species. The type species E. mirabilis was named by paleontologist Robert Broom in 1931 from a skull missing the lower jaw. A second skull, belonging to a probably immature individual, was later described. In 2022, a second species, E. liuyudongi, was named by Jun Liu and Fernando Abdala from a well-preserved skull. It is a member of the family Akidnognathidae, which historically has also been referred by as the synonymous Euchambersiidae.

<i>Pantelosaurus</i> Extinct genus of synapsids

Pantelosaurus is an extinct genus of basal sphenacodonts known from the Early Permian period of Saxony, Germany. It contains a single species, Pantelosaurus saxonicus.

<i>Palaeohatteria</i> Extinct genus of synapsids

Palaeohatteria is an extinct genus of basal sphenacodonts known from the Early Permian period of Saxony, Germany. It contains a single species, Palaeohatteria longicaudata.

"Haptodus" garnettensis is an extinct species of basal sphenacodont from the Late Carboniferous (Pennsylvanian) of Kansas, USA.

<i>Milosaurus</i> Extinct genus of synapsids

Milosaurus is an extinct genus of non-mammalian synapsids native to Illinois that was alive during the latest Carboniferous and earliest Permian. It was named in 1970 on the basis of FMNH 701, a partial skeleton, as well as referred material.

<i>Progalesaurus</i> Extinct genus of cynodonts

Progalesaurus is an extinct genus of galesaurid cynodont from the early Triassic. Progalesaurus is known from a single fossil of the species Progalesaurus lootsbergensis, found in the Lystrosaurus Assemblage Zone of the Balfour Formation. Close relatives of Progalesaurus, other galesaurids, include Galesaurus and Cynosaurus. Galesaurids appeared just before the Permian-Triassic extinction event, and disappeared from the fossil record in the Middle-Triassic.

<i>Ianthodon</i> Extinct genus of synapsids

Ianthodon is an extinct genus of basal haptodontiform synapsids from the Late Carboniferous about 304 million years ago. The taxon was discovered and named by Kissel & Reisz in 2004. The only species in the taxon, Ianthodon schultzei, was found by separating it from a block that also contained the remains of Petrolacosaurus and Haptodus. The evolutionary significance of the taxon wasn't realized until a publication in 2015. The fossil of this organism was discovered in Garnett, Kansas.

<i>Raranimus</i> Extinct genus of therapsids

Raranimus is an extinct genus of therapsids of the Middle Permian. It was described in 2009 from a partial skull found in 1998 from the Dashankou locality of the Qingtoushan Formation, outcropping in the Qilian Mountains of Gansu, China. The genus is the most basal known member of the clade Therapsida, to which the later Mammalia belong.

<i>Cutleria wilmarthi</i> Extinct genus of synapsids

Cutleria is an extinct genus of basal sphenacodontids or derived stem-sphenacodontoid known from the Early Permian period of Colorado, United States. It contains a single species, Cutleria wilmarthi.

<i>Karenites</i> Genus of therapsids from the Late Permian of Russia

Karenites is an extinct genus of therocephalian therapsids from the Late Permian of Russia. The only species is Karenites ornamentatus, named in 1995. Several fossil specimens are known from the town of Kotelnich in Kirov Oblast.

<i>Abdalodon</i> Extinct genus of cynodonts

Abdalodon is an extinct genus of late Permian cynodonts, known by its only species A. diastematicus.Abdalodon together with the genus Charassognathus, form the clade Charassognathidae. This clade represents the earliest known cynodonts, and is the first known radiation of Permian cynodonts.

<i>Gordodon</i> Extinct genus of edaphosaurid synapsids

Gordodon is an extinct genus of non-mammalian synapsid that lived during the Early Permian of what is now Otero County, New Mexico. It was a member of the herbivorous sail-backed family Edaphosauridae and contains only a single species, the type species G. kraineri. Gordodon is unusual among early synapsids for its teeth, which were arranged similarly to those of modern mammals and unlike the simple, uniform lizard-like teeth of other early herbivorous synapsids. Gordodon had large incisor-like teeth at the front, followed by a prominent gap between them and a short row of peg-like teeth at the back. Gordodon was also relatively long-necked for an early synapsid, with elongated and gracile vertebrae in its neck and back. Like other edaphosaurids, Gordodon had a tall sail on its back made from the bony neural spines of its vertebrae. The spines also had bony knobs on them, a common trait of edaphosaurids, but the knobs of Gordodon are also unique for being more slender, thorn-like and randomly arranged along the spines. It is estimated to have been rather small at 1 m in length excluding the tail and 34 kg (75 lb) in weight.

References

  1. 1 2 3 4 Reisz, R.R.; Heaton, M.J.; Pynn, B.R. (1982). "Vertebrate fauna of late Pennsylvanian rock lake shale near Garnett, Kansas: Pelycosauria". Journal of Paleontology. 56 (3): 741–750. JSTOR   1304403.
  2. Peabody, F.E. (1957). "Pennsylvanian reptiles of Garnett, Kansas: edaphosaurs. Journal of Paleontology". 31 (5): 947–949. JSTOR   1300561.{{cite journal}}: Cite journal requires |journal= (help)
  3. Currie, P.J. (1977). "A new haptodontine sphenacodont (Reptilia: Pelycosauria) from the Upper Pennsylvanian of North America". Journal of Paleontology. 51 (5): 927–942. JSTOR   1303764.
  4. Laurin, M. (1993). "Anatomy and relationships of Haptodus garnettensis, a Pennsylvanian synapsid from Kansas". Journal of Vertebrate Paleontology. 13 (2): 200–229. doi:10.1080/02724634.1993.10011501.
  5. 1 2 3 4 5 6 7 8 9 10 Spindler, F. (2020). "A faunivorous early sphenacodontian synapsid with a diastema". Palaeontologia Electronica. 23 (1). doi: 10.26879/1023 .
  6. 1 2 3 4 5 6 7 Spindler, F. (2015). The basal Sphenacodontia: systematic revision and evolutionary implications (Dr. rer. nat.). Freiberg University of Mining and Technology.
  7. Spindler, F.; Brink, K.; Piñeiro, G. (2013). Reitner, J.; Yang, Q.; Wang, Y.; Reich, M. (eds.). An upgraded perspective on basal Sphenacodontia, the stem group of mammal-like amniotes. Palaeobiology & Geobiology of Fossil Lagerstätten through Earth History. Göttingen: Universitätsverlag Göttingen. pp. 157–158. ISBN   9783863951351.
  8. Osborn, H.F. (1893). "Recent researches upon the succession of the teeth in mammals". The American Naturalist. 27 (318): 493–508. doi: 10.1086/275741 . S2CID   84727644.
  9. Liu, J.; Rubidge, B.; Li, J. (2009). "New basal synapsid supports Laurasian origin for therapsids". Acta Palaeontologica Polonica. 54 (3): 393–400. doi: 10.4202/app.2008.0071 . S2CID   55062279.
  10. Sidor, C.; Hopson, J. (1998). "Ghost lineages and "mammalness": Assessing the temporal pattern of character acquisition in the Synapsida". Paleobiology. 24 (2): 254–273. doi:10.1666/0094-8373(1998)024[0254:GLAATT]2.3.CO;2. S2CID   83773704.
  11. Spindler, F. (2019). "The skull of Tetraceratops insignis (Synapsida, Sphenacodontia)". Palaeovertebrata. 43 (1): e1. doi:10.18563/pv.43.1.e1. S2CID   214247325.
  12. Mazierski, D.M.; Reisz, R.R. (2010). "Description of a new specimen of Ianthasaurus hardestiorum (Eupelycosauria: Edaphosauridae) and a re-evaluation of edaphosaurid phylogeny". Canadian Journal of Earth Sciences. 47 (6): 901–912. Bibcode:2010CaJES..47..901M. doi:10.1139/E10-017.
  13. Jewett, J.M.; O'Connor, H.G.; Zeller, D.E. (1968). "Pennsylvanian System". In Zeller, D.E. (ed.). The Stratigraphic Succession in Kansas. Bulletin of the Kansas Geological Survey. Vol. 189. Lawrence: Kansas Geological Survey. pp. 21–43.
  14. Winston, R.B. (1983). "A late Pennsylvanian upland flora in Kansas: Systematics and environmental implications". Review of Palaeobotany and Palynology. 40 (1–2): 5–31. doi:10.1016/0034-6667(83)90003-9.
  15. Kerp, J.H.F.; Haubold, H. (1988). "Aspects of Permian palaeobotany and palynology. VIII. On the reclassification of the West-and Central European species of the form-genus Callipteris Brongniart 1849". Review of Palaeobotany and Palynology. 54 (1–2): 135–150. doi:10.1016/0034-6667(88)90009-7.
  16. Heckel, P.H. (1975). "Conclusions". Stratigraphy and Depositional Framework of the Stanton Formation in Southeastern Kansas. Vol. 210. Lawrence: Kansas Geological Survey.
  17. Spindler, F.; Voigt, S.; Fischer, J. (2020). "Edaphosauridae (Synapsida, Eupelycosauria) from Europe and their relationship to North American representatives". PalZ. 94: 125–153. doi:10.1007/s12542-019-00453-2. S2CID   198140317.
  18. Spindler, F.; Scott, D.; Reisz, R.R. (2015). "New information on the cranial and postcranial anatomy of the early synapsid Ianthodon schultzei (Sphenacomorpha: Sphenacodontia), and its evolutionary significance". Fossil Record. 18 (1): 17–30. doi: 10.5194/fr-18-17-2015 .
  19. Gee, B.M.; Reisz, R.R. (2020). "A redescription of the late Carboniferous trematopid Actiobates peabodyi from Garnett, Kansas". The Anatomical Record. 303 (11): 2821–2838. doi: 10.1002/ar.24381 . PMID   32003550. S2CID   210982434.
  20. Schultze, H.-P. (1996). "Terrestrial biota in coastal marine deposits: fossil-Lagerstätten in the Pennsylvanian of Kansas, USA". Palaeogeography, Palaeoclimatology, Palaeoecology. 119 (3–4): 255–273. Bibcode:1996PPP...119..255S. doi:10.1016/0031-0182(95)00011-9.