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Skeleton of Labidosaurus hamatus (Captorhinidae), an early member of Eureptilia.

Skeleton of Labidosaurus hamatus ( Captorhinidae ), an early member of Eureptilia.

Temporal occurrence
Upper Carboniferous ( Bashkirium ) to this day
315 to 0 million years
  • worldwide
Jaw mouths (Gnathostomata)
Land vertebrates (Tetrapoda)
Amniotes (Amniota)
Scientific name
Olson , 1947

The Eureptiles (Eureptilia) are an extensive taxon of the "higher" terrestrial vertebrates ( Amniota ), which unites most of the extinct and all recent reptiles including birds (Aves). It is mainly used in paleontological systematics. In the zoological system, which only considers recent animals, it is redundant to the taxon Diapsida .

Taxonomic history and modern definition

The name "Eureptilia" was coined in 1947 by the American geologist and paleontologist Everett C. Olson in the course of a reorganization of the class Reptilia under the abandonment of the Cotylosauria . In addition to the diapsids , Olson's eureptiles, in contrast to today's concept, also included the synapsids , which at that time were still defined as a purely fossil group without the mammals . He contrasted the eureptiles with the parareptiles , which, like today, comprised procolophonoids and pareiasaurs , but also forms that are now generally no longer considered amniotes, such as the Diadectomorpha and Seymouriamorpha . They also contained the turtles ("Chelonia"). The key feature was the absence (eureptilia) or the presence (parareptilia) of a pronounced otic slit in the posterior side wall of the skull. In addition, Olson suspected an independent origin of the two reptile groups within the more basal terrestrial vertebrates ("amphibians" in the broader sense).

As part of one of the first cladistic analyzes of the kinship relationships of the various large groups of amniotes, Gaffney (1980) discusses a possible sister group relationship of the turtles (Testudines) with a common clade of synapsids and diapsids and calls the latter “Eureptilia”. Gaffney's Eureptilia hypothesis was, however, in comparison with the sauropsid hypothesis established in subsequent analyzes , in which diapsids and turtles form a common clade, u. a.   supported by significantly fewer synapomorphies . The sauropsid hypothesis has essentially survived in the zoological and palaeontological system to this day (see systematics ), albeit with a changing position of the turtles within the sauropsida.

Laurin & Reisz (1995) define the Eureptilia stem-based as " Diapsids and all amniotes that are more closely related to these than to the Testudines ". The results of their cladistic analysis also confirm the sauropsid hypothesis, in that their eureptilia contain the diapsids and some “primitive” reptiles, but not the synapsids. By their definition, they clearly differentiate the Eureptilia within the Sauropsida from the tortoises and call the clade containing the tortoises Parareptilia. They are roughly based on Olson's original concept of the two groups.

Since the idea that turtles are diapsids themselves gained increasing acceptance in the late 1990s, Tsuji & Müller (2009) redefined the Eureptilia in the form of a “ stem-based triplet ” as “ the most comprehensive clade that includes both Captorhinus aguti and Petrolacosaurus kansensis contains, but not Procolophon trigoniceps ”.


Müller & Reisz (2006) list the following synapomorphies for the Eureptilia:

  • dorsal part of the ilium ( iliac blade ) narrow or low,
  • no contact between postorbital and supratemporal ,
  • severe ventrolateral constriction of the vertebral bodies of the trunk vertebrae.

For all Eureptilia with the exception of the most basal taxon Coelostegus prothales they also name the following synapomorphies:

  • The rear edge of the dorsal roof of the skull, receding in the form of a bay, on both sides of the central suture of the skull,
  • small supratemporale,
  • Participation of the supratemporals and parietals in the formation of the posterior lateral corner of the dorsal roof of the skull,
  • Participation of the Squamosum in the border of the post-temporal window,
  • Nasale is shorter than frontal.

However, a combination of all or at least most of these features occurs only in the most basic eureptiles ("basic construction plan"). For the "higher" (more strongly derived) taxa z. B. the supratemporal completely reduced or incorporated into the squamosum or the posterior edge of the dorsal cranial roof is straight or receding median instead of bilaterally. The back of the head is also closed in archosaurs , i.e. that is, they no longer have a post-temporal window.


The taxon Eureptilia is primarily of importance for vertebrate paleontology, since all recent Eureptiles are also diapsids at the same time. Taking into account the diapsid hypothesis of the phylogenetic origin of the turtles, all recent sauropsids are also diapsids at the same time. In addition, the Parareptilia, the Eureptilia sister group, are a purely fossil group. The use of a taxon Eureptilia does not make much sense under these circumstances in the zoological systematics.

One of the oldest terrestrial vertebrates, hylonomus , which is definitely considered a real amniot , comes from the early Upper Carboniferous ( Bashkirian , Westphalian A) and has been identified with the help of cladistic analyzes as the basal, but not the most basal representative of the Eureptilia. This means that the common ancestral species of eureptiles and parareptiles must also have lived in the early Upper Carboniferous at the latest, but well before Hylonomus . An origin of the sauropsids near the lower Carboniferous-Upper Carboniferous border is therefore relatively likely.


External system

Contrary to Olson's original assumption, eureptiles and parareptiles did not reach the level of organization of reptiles independently of one another, but rather go back to a common parent species that already belonged to the amniotes.

The possible family relationships are illustrated by the following, greatly simplified cladogram :

  Terrestrial vertebrates  

 Lissamphibia (today's amphibians)


 †  Lepospondyli


 †  Seymouriamorpha


 †  Diadectomorpha


 Synapsida (including mammals )

  Sauropsida  (Reptilia)  

 †  Parareptilia



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Internal system

The actual diversity of the parareptiles is not clear, but the eureptiles are undoubtedly the by far more comprehensive and diverse sauropsid line - if only due to the fact that their line of development has survived to this day and thus a good 230 million years longer. Among other things, it also includes the dinosaurs and thus the birds . The family relationships with a focus on the basal taxa outside the Diapsida (according to Müller & Reisz, 2006) are shown in the following cladogram :


 †  Coelostegus


 †  Captorhinidae


 †  Thuringothyris


 †  Brouffia


 †  Paleothyris


 †  Hylonomus


 †  Anthracodromeus


 †  protorothyris


 †  Cephalerpetone

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 †  Araeoscelidia


 †  Avicephala


 †  Younginiformes ( paraphyletic? )


†  Ichthyopterygia


? †  Sauropterygia



  Sauria 1  

Lepidosauromorpha  (including scaled reptiles ,
 bridge lizards ,?  Turtles ,? †  sauropterygia )


Archosauromorpha  (†  rhynchosaurs ,?  Turtles ,
 crocodiles , †  pterosaurs , dinosaurs including birds )

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Footnotes: 1) “Sauria” refers to the meaning of Gauthier et al. (1988) the common clade of Lepidosauromorpha and Archosauromorpha and should not be confused with the paraphyletic subtaxon lizards (also Lacertilia) of the Lepidosauromorpha, also called "Sauria" .


  1. Complete paragraph after: Everett C. Olson: The Family Diadectidae and its Bearing on the Classification of Reptiles. Fieldiana Geology. Vol. 11, No. 1, 1947, doi : 10.5962 / bhl.title.3579 , p. 43 ff.
  2. ^ Eugene S. Gaffney: Phylogenetic relationships of the major groups of amniotes. In: AL Panchen (Ed.): The Terrestrial Environment and the Origin of Land Vertebrates. Systematics Association Special Volume. No. 15, 1980, pp. 593-610.
  3. ^ Jacques A. Gauthier, Arnold G. Kluge, Timothy Rowe: The early evolution of the Amniota. in: Michael J. Benton (Ed.) The phylogeny and classification of the tetrapods, Volume 1: amphibians, reptiles, birds. Systematics Association Special Volume. No. 35A, 1988, pp. 103-155.
  4. Michael J. Benton: Phylogeny of the Major Tetrapod Groups: Morphological Data and Divergence Dates. Journal of Molecular Evolution. Vol. 30, No. 5, 1990, pp. 409-424, doi : 10.1007 / BF02101113 .
  5. Michel Laurin, Robert R. Reisz: A reevaluation of early amniote phylogeny. Zoological Journal of the Linnean Society. Vol. 113, No. 2, 1995, pp. 165-223, doi : 10.1007 / BF02101113 (alternative full text access : IUCN / SSC Tortoise and Freshwater Turtle Specialist Group PDF 672 kB).
  6. Linda A. Tsuji, Johannes Müller: Assembling the history of the Parareptilia: phylogeny, diversification, and a new definition of the clade. Fossil Record. Vol. 12, No. 1, 2009, pp. 71-81, doi : 10.1002 / mmng.200800011 .
  7. ^ A b c Johannes Müller, Robert R. Reisz: The Phylogeny of Early Eureptiles: Comparing Parsimony and Bayesian Approaches in the Investigation of a Basal Fossil Clade. Systematic Biology. Vol. 55, No. 3, 2006, pp. 503-511, doi : 10.1080 / 10635150600755396 .
  8. ^ Jacques A. Gauthier, Arnold G. Kluge, Timothy Rowe: The early evolution of the Amniota. Pp. 103–155 in: Michael J. Benton (Ed.): The phylogeny and classification of the tetrapods, Volume 1: amphibians, reptiles, birds. Clarendon Press, Oxford 1988.