Palæos:		Unit 400: Therapsida
The Vertebrates		410: Dinocephalia: Stenocybus

Therapsida: Dinocephalia: Stenocybus

SYNAPSIDA
|
Therapsida
|--Biarmosuchia
`--Eutherapsida
`--+--Dinocephalia
   |  |--Stenocybus
   |  |--Estemmenosuchidae
   |  `--+--Anteosauria
   |     `--Tapinocephalia
   `--+--Anomodontia
      |  |--Venyukovioidea
      |  `--Dicynodontia   
      `--Theriodontia
         |--Gorgonopsia
         `--+--Therocephalia
            `--CYNODONTIA

Taxa on This Page

1. Stenocybus X

Dinocephalia: Stenocybus

Stenocybus - artwork by Dmitry Bogdanov - Wikipedia

Stenocybus: S. acidentatus Cheng & Li 1997

Range: Middle Permian (Roadian) of China.

Phylogeny: Either: Dinocephalia: Tapinocephalia + (Anteosauria + *) (if basal Anteosaur) or Dinocephalia: (Tapinocephalia + Anteosauria) + * (if basal Dinocephalian)

Location: Xidagou Formation, Dashankou, Yumen, Gansu Province, China.

Remains: One near-complete skull (IGCAGS V 361), plus the right premaxilla, maxilla and dentary of a second (IVPP V12008).

Size: Skull length 12-15 cm.

Diagnosis: Cheng & Li (1997) Skull high, narrow, slender without pachyosteosis; orbit large; temporal fossa small; maxilla high, triangular-shaped, with top above canine and connecting with prefrontal; lacrimal large and extending forward; frontal with no boss and interorbital ridge; anterior border of attachment depression for lower jaw adductor on dorsal surface of postfrontal; small teeth present on palatine and transverse process of pterygoid; marginal tooth formula I 5/4, C 1/1, PC 6-8/6; incisors large, procumbent, interlocked, with labial talon pointer and lingual heel.

Comments: Stenocybus acidentatus was a relatively small dinocephalian that lacked the pachyosteosis of more derived forms. It had a very high, narrow skull, triangular in dorsal view, with a large orbit compared to other dinocephalians.

Cheng & Li (1997) assigned their new form to the Dinocephalia on the basis of the lingual heel on the incisors and the position of the lower jaw adductor, but regarded it as basal within the clade due to the small skull without pachyosteosis, small temporal fenestra, lower jaw articulation not anteriorly moved, maxilla with apex above the canine rather than posteriorly, and lacrimal extended anteriorly rather than short. While Cheng & Li (1997) placed Stenocybus outside the Anteosauria + Tapinocephalia clade, they seem to have only compared it with members of Anteosauria and not directly to members of Tapinocephalia. Rubidge & Sidor (2001) place it closer to Anteosauria than Tapinocephalia, again without much comment.

Credits: CKT071010

checked MAK091113 (original pagge Palaeos org - Stenocybus