Diadectidae

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Diadectids
Temporal range: Late Carboniferous – Late Permian, 305–256  Ma
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(possible Early Carboniferous occurrence)
Diadectes phaseolinus.JPG
Skeleton of Diadectes sideropelicus in the American Museum of Natural History
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Order:† Diadectomorpha
Family:† Diadectidae
Cope, 1880
Genera

Diadectidae is an extinct family of early tetrapods that lived in what is now North America and Europe during the Late Carboniferous and Early Permian, and in Asia during the Late Permian. They were the first herbivorous tetrapods, and also the first fully terrestrial animals to attain large sizes. Footprints indicate that diadectids walked with an erect posture. They were the first to exploit plant material in terrestrial food chains, making their appearance an important stage in both vertebrate evolution and the development of terrestrial ecosystems.

Contents

The best known and largest representative of the family is Diadectes , a heavily built animal that attained a maximum length of several metres. Several other genera and various fragmentary fossil remains are also known. Although well known genera like Diadectes first appear in the Late Pennsylvanian, fragmentary remains of possible diadectids are known from much earlier deposits, including a piece of lower jaw found in Mississippian strata from Tennessee.

Description

Life restoration of Diadectes, a well-known Early Permian diadectid Diadectes1DB.jpg
Life restoration of Diadectes , a well-known Early Permian diadectid

Diadectids have large bodies with relatively short limbs. The rib cage is barrel-shaped to accommodate a large digestive tract necessary for the digestion of cellulose in plants. The skulls of diadectids are wide and deep with blunt snouts. The internal nares (holes for the nostrils) are also short. [1] Paleontologist E.C. Case compared diadectids to turtles in 1907, noting their large pectoral girdles, short, strong limbs, and robust skulls. Case described them as "lowly, sluggish, inoffensive herbivorous reptiles, clad in an armor of plate to protect them from the fiercely carnivorous pelycosaurs." [2]

Diadectids have a heterodont dentition, meaning that their teeth vary in shape along the length of the jaws. The teeth are wide and bear many cusps or projections, an indication that diadectids ate tough plants. Some teeth are leaf-shaped and laterally compressed, another indication that diadectids were able to shred plant material. The procumbent front teeth of the lower jaw project forward. Diadectids likely had strong jaw muscles for processing plant material; the placement of the jaw joints above or below the level of the occlusal plane (the plane at which the teeth come together) would have given diadectid jaws mechanical advantage. The joints themselves give the jaws a complex range of movement suitable for consuming plants. Large holes and cavities in the skull called adductor chambers and temporal openings would have provided room for large jaw-closing muscles. [1] A ridge on the dentary bone of the lower jaw may have provided a surface for chewing or even supported a beak. [3]

History of study

The first diadectid to be described was Diadectes. American paleontologist Edward Drinker Cope named the genus in 1878 on the basis of several vertebrae and teeth from the Early Permian of Texas. [4] Cope erected the family Diadectidae in 1880 to include Diadectes and Empedocles , a genus he named two years earlier. [5] Nothodon , named by Cope's rival Othniel Charles Marsh in 1878, was soon placed in the family. [6]

Cope named several other diadectids, including Helodectes in 1880, [7] Chilonyx and Empedias in 1883, [8] and Bolbodon in 1896. [9] Paleontologist E.C. Case named four other diadectids: Desmatodon in 1908, [10] Diasparactus in 1910, [11] Diadectoides in 1911, [12] and Animasaurus along with paleontologist Samuel Wendell Williston in 1912. [13] Case and Williston considered Marsh's Nothodon and Cope's Bolbodon to be synonymous with Diadectes. Marsh named Nothodon in the American Journal of Science only five days before Cope described Diadectes in Proceedings of the American Philosophical Society . Under rules of the International Code of Zoological Nomenclature, the name Nothodon would have priority over Diadectes, but because the name Diadectes has been in use since Case and Williston first synonymized the genera, Diadectes remains the accepted name. [1]

In North America, diadectids are known from Texas, Colorado, Utah, New Mexico, Oklahoma, Ohio, West Virginia, Pennsylvania, and Prince Edward Island. A possible diadectid has also been found from Tennessee. It is known from a broken lower jaw and several teeth found in Mississippian-age (Chesterian) strata that are likely part of the Bangor Formation. [14] In a detailed review of Diadectidae, paleontologist E.C. Olson placed three North American genera within the family: Diadectes, Diasparactus, and Desmatodon. Chilonyx, Empedias, Diadectoides, and Animasaurus were synonymized with Diadectes, and four species of Diadectes (D. sideropelicus, D. tenuitectes, D. lentus, and D. carinatus) were recognized. [15] A fourth genus, Ambedus , was named in 2004 from the Early Permian of Ohio.

Orobates, a diadectid from Germany Orobates BW.jpg
Orobates , a diadectid from Germany

Diadectids are also known from Germany. Phanerosaurus was described from several vertebrae near Zwickau by German paleontologist Christian Erich Hermann von Meyer in 1860, but was not recognized as a diadectid until 1925. [16] A second species of Phanerosaurus was identified from some vertebrae and a fragmentary skull in 1882, and was given its own genus, Stephanospondylus , in 1905. [17] In 1998, a new species of Diadectes, D. absitus, was described from the Bromacker sandstone quarry of the Tambach Formation in the Thuringian Forest of central Germany. [18] A new genus of diadectid called Orobates was also named from the Bromacker Quarry in 2004. [19]

In 2015, the known geographic range of diadectids was expanded with the description of a new genus and species of diadectid from China, Alveusdectes fenestralis . Alveusdectes is also the youngest known diadectid by 16 million years, coming from a unit of the Late Permian Shangshihezi Formation that dates to about 256 million years. [20]

Classification

Diadectids have long been considered close relatives of the amniotes, tetrapods that lay eggs on land or retain the fertilized egg within the mother. In 1987, the paleontologist D.M.S. Watson placed the family in the larger group Diadectomorpha, which includes another family of large-bodied diadectomorphs, the Limnoscelidae, as well as the monotypic diadectomorph family Tseajaiidae, represented by the genus Tseajaia . Throughout the twentieth century, amniotes and diadectomorphs were often grouped together using the old name Cotylosauria, a name originally used for the most basal grade of what was then thought to be reptiles. In the early part of the century, many paleontologists regarded diadectids, along with other cotylosaurs (such as placodonts), to be close relatives of turtles. [21] In most recent studies of early tetrapod phylogeny, Cotylosauria is no longer recognized and Diadectomorpha is placed as the sister taxon of Amniota. However, while the majority of analyses now place diadectids outside Amniota, some have found them to be true amniotes. [22] [23]

Most phylogenetic studies of the three diadectomorph families – Diadectidae, Limnoscelidae, and Tseajaiidae – have found diadectids and limnoscelids to be more closely related to each other than either is to Tseajaia. In other words, Diadectidae and Limnoscelidae form a clade within Diadectomorpha and Tseajaia is excluded from the clade. In a 2010 phylogenetic analysis, Diadectidae formed a clade that was characterized by wide cheek teeth with cusps on either side. Unlike previous studies, it was found to be more closely related to Tseajaiidae than Limnoscelidae. The family was defined as Diadectes and all taxa sharing a more recent common ancestor with Diadectes than with Tseajaia. Below is a cladogram modified from the 2010 analysis: [1]

Diadectomorpha  

Diadectes is the best known diadectid, with six species named since its initial description. In a 2005 phylogenetic analysis, most species of Diadectes formed a clade with Diasparactus zenos. Two species, Diadectes absitus and Diadectes sanmiguelensis, were placed in more basal positions. These species possess primitive characteristics found in non-diadectid forms, such as Limnoscelis and Tseajaia. Because D. absitus and D. sanmiguelensis were placed far from other species of Diadectes in the analysis, their assignment to the genus was questioned. [24] The same results were found in the 2010 analysis. Two new genera were erected in the study to include D. abstus and D. sanmiguelensis. D. sanmiguelensis, the more basal of the two forms, was placed in the new genus "Oradectes". D. abstus was renamed "Silvadectes". [1] However, according to the ICZN, a name presented in an initially unpublished thesis such as Kissel's is not valid. Because the names "Oradectes" and "Silvadectes" have not yet been formally erected in a published paper, they were not, as of 2010, considered valid.

In a 2013 study, David Berman argued that there wasn't enough evidence to justify Ambedus being in Diadectidae. He stated in his paper that its assignment to Diadectidae is based only on several isolated maxillae and dentaries containing cheek teeth that only exhibited a resemblance in their molar-like morphology to those in Diadectids. There are also a number of other characteristics that distinguish Ambedus from all other Diadectids, such as a shallow rather than deep deep dentary, and relatively high maxillary and dentary tooth counts, among other characteristics that distinguish them from Diadectids. Furthermore, the appearance of Ambedus pusillus so late in the fossil record also casts a doubt on the fact that it is supposed to represent the basalmost member of the Diadectid lineage. In contrast, the first Diadectids from the Upper Pennsylvanian were far more developed and had the characteristic dentary and maxillary features of the Diadectid lineage. This implicates that there should be a ghost lineage that goes back all the way back to the Middle Pennsylvanian, which is highly unlikely according to Berman. [25]

Evolutionary history

Diadectids were some of the first tetrapods, or four-legged vertebrates, to attain large sizes. Diadectids first appear in the Late Carboniferous with the genus Desmatodon , although recently described bones from Tennessee suggest that they may have appeared even earlier in the Early Carboniferous. [14] They underwent a small evolutionary radiation in the Late Carboniferous and Early Permian, diversifying into thirteen species and outnumbering other diadectomorphs, such as the limnoscelids. This radiation was likely the result of diadectids' expansion into a new herbivorous ecological niche that was previously unfilled.

Diadectids had a much wider geographic distribution than their relatives; while the distribution of limnoscelids is limited to parts of North America and Tseajaia is restricted to just the southwestern United States, diadectids are present in North America, Europe, and Asia. [1] During the late Carboniferous and Permian these regions formed a single landmass called Laurasia, which comprised the northern portion of the supercontinent Pangea. For most of their evolutionary history, diadectids were likely limited to the western half of Laurasia, which is now North America and Europe. The presence of the late-surviving Alveusdectes in China suggests that diadectids radiated eastward across Laurasia. They could not have reached what is now China until the Middle Permian because, prior to that time, the Tethys Sea separated it from the rest of Laurasia. The group does not seem to have diversified to the same extent in the east as they did in the west given that no diadectids are known from Russia, which has an extensive fossil record of Early and Middle Permian tetrapod assemblages. [20]

Paleobiology

Diet

Life restoration of Diasparactus Diasparactus1DB.jpg
Life restoration of Diasparactus

Diadectids were the first fully herbivorous tetrapods. Although several other groups of early tetrapods independently acquired herbivory, diadectids were the only Carboniferous tetrapods that were able to process high-fiber terrestrial plants. Diadectids were also the most diverse group of herbivores, representing the first radiation of plant-eating tetrapods. [1] Both Cope and Marsh recognized that diadectids were herbivores in 1878 when they studied their distinctively broad, cusped teeth (in his description of Diadectes, Cope mentioned, "animals belonging to this genus were, in all probability, herbivorous" [4] ).

Locomotion

Diadectids were once thought to be sprawling animals with their short, robust legs positioned to the sides of their large bodies. Despite this, several lines of evidence, including trackways and limb morphology, suggest that diadectids moved in a more erect posture. While earlier tetrapods possess several simple tarsal bones in their ankles, diadectids have a more complex astragalus formed from the fusion of these bones. Astragali are present in terrestrial amniotes and are identical in structure to those of diadectids. Therefore, the ankle structure of diadectids bears a closer resemblance to those of advanced terrestrial vertebrates like mammals and reptiles than those of earlier tetrapods. Since diadectids are the only diadectomorphs with astragali, they likely developed the structure independent of amniotes. [26]

Although they bear similarities to those of amniotes, the tarsal bones of diadectids are poorly ossified and loosely connected. The digits of the foot connect only to the fourth distal tarsal, providing a wide range of movement in the foot. This flexibility enabled diadectids to rotate their feet in a forward position while walking, providing greater force when pushing off. The feet could also be placed closer to the midline of the body to give diadectids an erect stance. [26]

Evidence for an erect stance can be found in trackways attributed to diadectids. The most well-preserved of these trackways are present in the Tambach Formation in central Germany. A 2007 study identified two different ichnospecies, Ichniotherium cottae and I. sphaerodactylum, as footprints of the diadectids Silvadectes absitus and Orobates pabsti, respectively. This was the first species-level identification of trackmakers of Paleozoic-era trackways, making the footprints the oldest yet associated with specific animal species. [27] The close positioning of the footprints attributed to the more advanced diadectides suggests that the animals held their feet almost underneath their bodies, giving them a more efficient gait and to some degree paralleling the stance of mammals more than that of the sprawling amphibians and most reptiles. [27] [28]

Related Research Articles

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"Labyrinthodontia" is an informal grouping of extinct predatory amphibians which were major components of ecosystems in the late Paleozoic and early Mesozoic eras. Traditionally considered a subclass of the class Amphibia, modern classification systems recognize that labyrinthodonts are not a formal natural group (clade) exclusive of other tetrapods. Instead, they consistute an evolutionary grade, ancestral to living tetrapods such as lissamphibians and amniotes. "Labyrinthodont"-grade vertebrates evolved from lobe-finned fishes in the Devonian, though a formal boundary between fish and amphibian is difficult to define at this point in time.

<span class="mw-page-title-main">Reptiliomorpha</span> Clade of reptile-like animals

Reptiliomorpha is a clade containing the amniotes and those tetrapods that share a more recent common ancestor with amniotes than with living amphibians (lissamphibians). It was defined by Michel Laurin (2001) and Vallin and Laurin (2004) as the largest clade that includes Homo sapiens, but not Ascaphus truei. Laurin and Reisz (2020) defined Pan-Amniota as the largest total clade containing Homo sapiens, but not Pipa pipa, Caecilia tentaculata, and Siren lacertina.

<i>Diadectes</i> Extinct genus of reptiles

Diadectes is an extinct genus of large reptiliomorphs or synapsids that lived during the early Permian period. Diadectes was one of the first herbivorous tetrapods, and also one of the first fully terrestrial vertebrates to attain large size.

<span class="mw-page-title-main">Diadectomorpha</span> Extinct clade of tetrapods

Diadectomorpha is a clade of large tetrapods that lived in Euramerica during the Carboniferous and Early Permian periods and in Asia during Late Permian (Wuchiapingian), They have typically been classified as advanced reptiliomorphs positioned close to, but outside of the clade Amniota, though some recent research has recovered them as the sister group to the traditional Synapsida within Amniota, based on inner ear anatomy and cladistic analyses. They include both large carnivorous and even larger herbivorous forms, some semi-aquatic and others fully terrestrial. The diadectomorphs seem to have originated during late Mississippian times, although they only became common after the Carboniferous rainforest collapse and flourished during the Late Pennsylvanian and Early Permian periods.

<span class="mw-page-title-main">Caseasauria</span> Extinct clade of synapsids

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

Sphenacodon is an extinct genus of synapsid that lived from about 300 to about 280 million years ago (Ma) during the Late Carboniferous and Early Permian periods. Like the closely related Dimetrodon, Sphenacodon was a carnivorous member of the Eupelycosauria family Sphenacodontidae. However, Sphenacodon had a low crest along its back, formed from blade-like bones on its vertebrae instead of the tall dorsal sail found in Dimetrodon. Fossils of Sphenacodon are known from New Mexico and the Utah–Arizona border region in North America.

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Ichniotherium is an ichnogenus of tetrapod footprints from between the Late Carboniferous period to the Early Permian period attributed to diadectomorph track-makers. These footprints are commonly found in Europe, and have also been identified in North America and Morocco. Three ichnospecies of Ichniotherium have been proposed as valid: I. cotta, I. sphaerodactylum, and I. praesidentis.

<i>Limnoscelis</i> Genus of diadectomorphs

Limnoscelis was a genus of large diadectomorph tetrapods from the Late Carboniferous to early Permian of western North America. It includes two species: the type species Limnoscelis paludis from New Mexico, and Limnoscelis dynatis from Colorado, both of which are thought to have lived concurrently. No specimens of Limnoscelis are known from outside of North America. Limnoscelis was carnivorous, and likely semiaquatic, though it may have spent a significant portion of its life on land. Limnoscelis had a combination of derived amphibian and primitive reptilian features, and its placement relative to Amniota has significant implications regarding the origins of the first amniotes.

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<i>Tseajaia</i> Extinct genus of tetrapods

Tseajaia is an extinct genus of diadectomorph tetrapod from the Early Permian of western North America. The skeleton is that of a medium-sized, rather advanced reptile-like animal. In life it was about 1 metre (3 ft) long and may have looked vaguely like an iguana. The dentition was somewhat blunt, indicating herbivory or possibly omnivory. It contains a single known species, Tseajaia campi.

<i>Orobates</i> Extinct genus of reptiliomorphs

Orobates is an extinct genus of diadectid reptiliomorphs that lived during the Early Permian. Its fossilised remains were found in Germany. A combination of primitive and derived traits distinguish it from all other well-known members of Diadectidae, a family of herbivorous reptiliomorphs. It weighed about 4 kg and appears to have been part of an upland fauna, browsing on high fibre plants.

<span class="mw-page-title-main">Limnoscelidae</span> Extinct family of tetrapods

Limnoscelidae is a family of carnivorous diadectomorphs. They would have been the largest terrestrial carnivores of their day, the other large carnivores being aquatic or semi aquatic labyrinthodont amphibians. The Limnoscelidae themselves, being close to the ancestry of amniotes, would have been well adapted land animals, but still dependent on anamniote eggs, and possibly having a tadpole stage. Contrary to the more advanced herbivorous diadectids, the teeth retained labyrinthodont infolding of the enamel, and were pointed and slightly recurved at the tip.

Ambedus is an extinct genus of possible diadectid reptiliomorph. Fossils have been found from the Early Permian Dunkard Group of Monroe County, Ohio. The type species A. pusillus was named in 2004. The genus name comes from the Latin word ambedo meaning "to nibble", in reference to its herbivorous diet. The specific name pusillus means "tiny" in Latin.

Phanerosaurus is an extinct genus of diadectid reptiliomorph from the Early Permian of Germany. Fossils are known from the Leukersdorf Formation near Zwickau. German paleontologist Christian Erich Hermann von Meyer named the type species P. naumanni in 1860 on the basis of several sacral and presacral vertebrae. A second species, P. pugnax, was named in 1882 but placed in its own genus Stephanospondylus in 1905.

Desmatodon is an extinct genus of diadectid reptiliomorph. With fossils found from the Kasimovian (Missourian) stage of the Late Carboniferous of Pennsylvania, Colorado, and New Mexico in the United States, Desmatodon is the oldest known diadectid. Two species are currently recognized: the type species D. hollandi and the species D. hesperis.

<i>Stephanospondylus</i> Extinct genus of tetrapods

Stephanospondylus is an extinct genus of diadectid reptiliomorph from the Early Permian of Germany. Fossils have been found in deposits of the Lower Rotliegend near Dresden. The type species S. pugnax was originally referred to the genus Phanerosaurus in 1882 but was placed in its own genus in 1905.

<span class="mw-page-title-main">Tambach Formation</span> Early Permian-age geologic formation in Germany

The Tambach Formation is an Early Permian-age geologic formation in central Germany. It consists of red to brown-colored sedimentary rocks such as conglomerate, sandstone, and mudstone, and is the oldest portion of the Upper Rotliegend within the Thuringian Forest Basin.

Alveusdectes is an extinct genus of diadectid tetrapod from the Late Permian of China. Like other diadectids, it was a large-bodied terrestrial herbivore capable of eating tough fibrous plant material. It was described in 2015 on the basis of a single partial skull and lower jaw found in the Shangshihezi Formation near the city of Jiyuan in Henan. This skull was found in a layer of the Shangshihezi Formation that dates to about 256 million years ago and contains the remains of many other terrestrial tetrapods including pareiasaurs, chroniosuchians, and therapsids. Alveusdectes is the youngest known diadectid by 16 million years and is also the only diadectid known from Asia. It likely represents a late-surviving lineage of diadectids that radiated eastward from western Laurasia into north China. Diadectids are otherwise absent from eastern Laurasia, which may reflect their low diversity at the time. Diadectids first appeared in the Late Carboniferous and were the first animals to have ever occupied the niche of large-bodied herbivores, allowing them to undergo an evolutionary radiation in the Early Permian. By the Late Permian many other groups of tetrapods had entered that niche, and increased competition among herbivores likely resulted in the eventual extinction of diadectids. Alveusdectes may have been able to persist because the fauna of north China seems to have been isolated from other Laurasian faunas during the Late Permian, meaning that fewer herbivores were competing for the same ecological space.

<span class="mw-page-title-main">Organ Rock Formation</span>

The Organ Rock Formation or Organ Rock Shale is a formation within the late Pennsylvanian to early Permian Cutler Group and is deposited across southeastern Utah, northwestern New Mexico, and northeastern Arizona. This formation notably outcrops around Canyonlands National Park, Natural Bridges National Monument, and Monument Valley of northeast Arizona, southern Utah. The age of the Organ Rock is constrained to the latter half of the Cisuralian epoch by age dates from overlying and underlying formations. Important early terrestrial vertebrate fossils have been recovered from this formation in northern Arizona, southern Utah, and northern New Mexico. These include the iconic Permian terrestrial fauna: Seymouria, Diadectes, Ophiacodon, and Dimetrodon. The fossil assemblage present suggests arid environmental conditions. This is corroborated with paleoclimate data indicative of global drying throughout the early Permian.

References

  1. 1 2 3 4 5 6 7 Kissel, R. (2010). Morphology, Phylogeny, and Evolution of Diadectidae (Cotylosauria: Diadectomorpha) (Thesis). Toronto: University of Toronto Press. p. 185. hdl:1807/24357.
  2. ↑ Case, E.C. (1907). "Restoration of Diadectes". The Journal of Geology. 15 (6): 556–559. Bibcode:1907JG.....15..556C. doi:10.1086/621427. JSTOR   30061495.
  3. ↑ Welles, S.P. (1941). "The mandible of a diadectid cotylosaur". University of California Bulletin of the Department of Geological Sciences. 25: 423–432.
  4. 1 2 Cope, E.D. (1878). "Descriptions of extinct Batrachia and Reptilia from the Permian formation of Texas". Proceedings of the American Philosophical Society. 17: 182–193.
  5. ↑ Cope, E.D. (1880). "The skull of Empedocles". The American Naturalist. 14: 304. doi:10.1086/272549.
  6. ↑ Marsh, O.C. (1878). "Notice of new fossil reptiles". American Journal of Science. 15 (89): 409–411. Bibcode:1878AmJS...15..409M. doi:10.2475/ajs.s3-15.89.409.
  7. ↑ Cope, E.D. (1880). "Second contribution to the history of the Vertebrata of the Permian formation of Texas". Proceedings of the American Philosophical Society. 19: 38–58.
  8. ↑ Cope, E.D. (1883). "Fourth contribution to the history of the Permian formation of Texas". Proceedings of the American Philosophical Society. 20: 634.
  9. ↑ Cope, E.D. (1896). "Second contribution to the history of the Cotylosauria". Proceedings of the American Philosophical Society. 35: 122–139.
  10. ↑ Case, E.C. (1908). "Description of vertebrate fossils from the vicinity of Pittsburgh, Pennsylvania". Annals of the Carnegie Museum. 4: 234–241.
  11. ↑ Case, E.C. (1910). "New or little known reptiles and amphibians from the Permian (?) of Texas". Bulletin of the American Museum of Natural History. 28: 136–181. Archived from the original on 2014-06-12. Retrieved 2017-09-09.
  12. ↑ Case, E.C. (1911). "A revision of the Cotylosauria of North America". Carnegie Institution of Washington Publication. 145: 1–121. hdl: 2027/mdp.39015023570826 .
  13. ↑ Case, E.C.; Williston, S.W. (1912). "A description of the skulls of Diadectes lentus and Animasaurus carinatus". American Journal of Science. 33 (196): 339–348. Bibcode:1912AmJS...33..339C. doi:10.2475/ajs.s4-33.196.339.
  14. 1 2 Corgan, J.X.; Priestley, M.P. (2005). "A high-fiber tetrapod, Diadectes (?) sp., from the Mississippian (Chesterian) of south central Tennessee". Geological Society of America Abstracts with Programs. 37 (2): 39. Archived from the original on 2011-05-14. Retrieved 2005-07-14.
  15. ↑ Olson, E.C. (1947). "The family Diadectidae and its bearing on the classification of reptiles". Fieldiana Geology. 11: 1–53.
  16. ↑ Romer, A.S. (1925). "Permian amphibian and reptilian remains described as Stephanospondylus". Journal of Geology. 33 (4): 447–463. Bibcode:1925JG.....33..447R. doi:10.1086/623210. JSTOR   30060376.
  17. ↑ Stappenbeck, R. (1905). "Uber Stephanospondylus n. g. und Phanerosaurus H. v. Meyer". Zeitschrift der Deutschen Geologischen Gesellschaft. 57: 380–437.
  18. ↑ Berman, D.S.; Sumida, S.S.; Martens, T. (1998). "Diadectes (Diadectomorpha: Diadectidae) from the Early Permian of central Germany, with description of a new species". Annals of the Carnegie Museum. 67: 53–93.
  19. ↑ Berman, D.S.; Henrici, A.C.; Kissel, R.A.; Sumida, S.S.; Martens, T. (2004). "A new diadectid (Diadectomorpha), Orobates pabsti, from the Early Permian of Central Germany". Bulletin of Carnegie Museum of Natural History. 35: 1–36. doi:10.2992/0145-9058(2004)35[1:ANDDOP]2.0.CO;2. ISSN   0145-9058.
  20. 1 2 Jun Liu and Gabe S. Bever (2015). "The last diadectomorph sheds light on Late Palaeozoic tetrapod biogeography". Biology Letters. 11 (5): 20150100. doi:10.1098/rsbl.2015.0100. PMC   4455737 . PMID   25948572.
  21. ↑ Laurin, M.; Reisz, R.R. (1995). "A reevaluation of early amniote phylogeny". Zoological Journal of the Linnean Society. 113 (2): 165–223. doi:10.1111/j.1096-3642.1995.tb00932.x.
  22. ↑ Berman, D.S.; Sumida, S.S.; Lombard, R.E. (1992). "Reinterpretation of the temporal and occipital regions in Diadectes and the relationships of diadectomorphs". Journal of Paleontology. 66 (3): 481–499. doi:10.1017/S0022336000034028. JSTOR   1305873. S2CID   73547163.
  23. ↑ Modesto, S.P. (1992). "Did herbivory foster early amniote diversification?". Journal of Vertebrate Paleontology. 12 (Supplement 3): 44A. doi:10.1080/02724634.1992.10011483.
  24. ↑ Kissel, R.; Reisz, R.; Berman, D. (2005). "Revisiting the taxonomy of Diadectidae (Cotylosauria: Diadectomorpha): a phylogenetic approach". Journal of Vertebrate Paleontology. 25 (Supplement 3): 78A. doi:10.1080/02724634.2005.10009942.
  25. ↑ Berman, David S (2013). "DIADECTOMORPHS,AMNIOTES OR NOT?". New Mexico Museum of Natural History and Science (60): 22.
  26. 1 2 Berman, D.S.; Henrici, A.C. (2003). "Homology of the astragalus and structure and function of the tarsus of Diadectidae". Journal of Paleontology. 77 (1): 172–188. doi:10.1666/0022-3360(2003)077<0172:HOTAAS>2.0.CO;2.
  27. 1 2 Voigt, S.; Berman, D.S.; Henrici, A.C. (2007). "First well-established track-trackmaker association of Paleozoic tetrapods based on Ichniotherium trackways and diadectid skeletons from the Lower Permian of Germany". Journal of Vertebrate Paleontology. 27 (3): 553–570. doi:10.1671/0272-4634(2007)27[553:FWTAOP]2.0.CO;2.
  28. ↑ Ker Than (12 September 2007). "Oldest Identifiable Footprints Found". LiveScience. Retrieved 6 February 2011.

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