The Vertebrates Seymouriamorpha

Reptiliomorpha: Seymouriamorpha

Abbreviated Dendrogram
Tetrapoda ├─Temnospondyli └─┬─Lepospondyli │ └─Reptiliomorpha ├─Anthracosauroidea │ └─┬─Embolomeri │ └─Chroniosuchia └─┬─Gephyrostegidae └─Batrachosauria ├─Seymouriamorpha │ ├─Discosauriscus │ └─Kotlassiidae └─┬─Solenodonsaurus └─Cotylosauria ├─Diadectomorpha └─Amniota


Taxa on This Page

  1. Batrachosauria
  2. Discosauriscus X
  3. Kotlassiidae X
  4. Seymouriamorpha X
Seymouria baylorensis

Seymouria baylorensis Broili, 1904, (Seymouriamorpha - Seymouriidae ),
life reconstruction, by Dmitry Bogdanov (Larger image (Wikipemia))


DiscosauriscusBatrachosauria: Seymouria + Jane Seymour

Range: from the Carboniferous

Reptiliomorpha : Anthracosauroidea + (Gephyrostegidae + * : Seymouriamorpha + (Solenodonsaurus + Cotylosauria)

Intercentrum reduced, large canine-like maxillary tooth.

Comments: Batrachosauria ("Frog Saurians") is a name given either to very reptile-like amphibians dating from the Carboniferous and Permian periods, or to amniotes and those amphibians very closely related to them. In current cladistic schemes, Batrachosauria is the sister clade to the Anthracosauroidea MAK050702

Links: A Batrachosauroid from the late Cretaceous of France; Untitled Document; Abstracts for PaleoBios 16(4). ATW021125.

Seymouriamorpha: Ariekanerpeton, Seymouria.

Early Permian to Late Permian of Europe, Russia, Central Asia & North America.

Batrachosauria : (Solenodonsaurus + Cotylosauria) + * : Discosauriscus + Kotlassiidae.

long ventrally bent process of tabular?; posttemporal fenestrae small; slender stapes; otic tube composed of opisthotic, prootic, & parasphenoid; palate closed, without interpterygoid vacuities; pterygoid with large, transverse dorsal flange extending to skull roof (= epipterygoid?); trunk short (24-28 presacral vertebrae); vertebrae composed of large, cylindrical pleurocentrum & small, crescentic intercentrum; atlantal vertebra with paired pleurocentra & arches; neural arches "swollen" (strongly convex dorsally, in anterior or posterior view); 1, sometimes 2 sacrals; caudal hemal arches; ribs present from 1st cervical to proximal caudals; pectoral region ribs expanded; limbs stout; pectoral girdle with interclavicle, clavicles and cleithra; robust humerus & femur; phalangeal formula in manus 23443 or 23453, in pes 23453; dermal cranial bones of adults deeply sculptured, with hexagonal pattern of ridges also found in many temnospondyls (suggests skin tightly attached to skull); larvae with external gills known; lateral line present in juvenile specimens, possibly also ampullary electroreceptors.  

Image: Seymouria adapted from Clack (2002)

Note: Juveniles were aquatic, adults terrestrial.  

Links: Seymouriamorpha; Seymouria; First record of Seymouria from Early Permian fissure fills at Richards Spur, Oklahoma; Untitled Document; The Journal of Vertebrate Paleontology; The Journal of Vertebrate Paleontology; Seymouriamorpha; Utegenia shpinari; Abstracts for PaleoBios 17(1-4); Amniote origins?; Redescription of Seymouria sanjuanensis (Seymouriamorpha) from ... abstract);  NRC Research Press- Canadian Journal of Earth Sciences.

References: Clack (2002). ATW031014


Late Permian of Europe & China.

Seymouriamorpha : Kotlassiidae + *.

skull less ossified than in Seymouria; snout shortened, kinetic line absent; rectangular tabular process (= tabular horn?); jugal exposed on ventral margin of skull; suborbital fenestra present; postorbital may contact supratemporal; "Many specimens have subdivided or fused skull roof bones"; quadrate and articular unossified; narrow interpterygoid vacuities in some; transverse flange of pterygoid may project ventrally below margin of skull; small Meckelian fenestrae present on medial face of jaw; 3 coronoids, all with teeth; dentary with up to 43 teeth; labyrinthodont dentition in more mature forms; 1-4 palatal tusks per vomer & 1-5 on palatines; 24 presacral vertebrae; 1 sacral with massive rib; gastralia absent; pectoral girdle with interclavicle bearing long parasternal process; paired clavicles with broad lateral plates; cleithra slender & cylindrical; scapula with stout supraglenoid buttress & large supraglenoid foramen; coracoid with distinct coracoid foramen; phalangeal formula is 2-3-4-5-3 for manus and pes; lateral line well preserved; ampullary electroreceptive organs present; integument of rounded scales with concentric rings.

Image: from Chordata (former site:

Note: Similar to Seymouria, perhaps less terrestrial. It has been repeatedly suggested that Discosauriscus is simply a larval form of Seymouria. This appears not to be correct, but it is true that many reported "discosauriscids" are juvenile forms.

Links: Discosauriscus; Discosauriscus sp.; Synonyms of Discosauriscus austriacus; ?????????? ?????? (Japanese); Paleontology and Geology Glossary: Di; The Journal of Vertebrate Paleontology; Mauro J. Cavalcanti Personal Page - Abstracts;; PERMIANO; Muzeum vychodnich Cech v Hradci Kralove (Czech); Snapshots from the 2002 Show: Ammonoidea 2002 I. ATW020623.

Kotlassiidae: Buzulukia, Bystrowiana, Dromotectum, Karpinskiosaurus, Kotlassia

Late Permian of Russia.

Seymouriamorpha : Discosauriscus + *.

aquatic seymouriamorph, larger than discosaurs; 1½ sacrals(!), as only one rib of anterior sacral contacts ilium; rhomboidal ventral bony scales.

Links: paleng1_2p72abs; 615921; Seymouriamorpha; Samples2.PDF; PaleoNET | Библиотека (associated fauna). ATW031025.

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