Edops, a Primitive Rhachitomous Amphibian from the Texas Red Beds

Exceptional endocranium and middle ear of Stanocephalosaurus (Temnospondyli: Capitosauria) from the Triassic of Algeria revealed by micro-CT scan, with new functional interpretations of the hearing system

“…The stylus columellae of the stapes is shorter and thicker than that of Mastodonsaurus giganteus (Schoch, 1999a: fig. 22) but not of Edops craigi (Romer & Witter, 1942: fig. 12).…”

“…4), which are also visible in Benthosuchus sushkini (Bystrow & Efremov, 1940), Lyrocephaliscus euri (Mazin & Janvier, 1983), Edops craigi (Romer & Witter, 1942), Eryops megacephalus (Sawin, 1941) or Dvinosaurus primus (Shishkin, 1968): they are consensually 610 assigned to the arteria carotis internae, a ramification of the arteria carotis communis observed in numerous species of Rana (Gaupp, 1899) and Salamandra (Francis, 1934). Consequently, as all conducts found in the parasphenoid of Stanocephalosaurus amenasensis seem to come from the arteria carotidis internae, they should belong to the arterial system.…”

“…Edops craigi (Romer & Witter, 1942), Eryops megacephalus (Sawin, 1941) and "Stanocephalosaurus" pronus (Howie, 1970) where these conducts are consensually assigned to branches 1 and 2 of the hypoglossal nerve XII. A third conduct is more problematic: located at the base of the processus paroticus in Stanocephalosaurus amenasensis, it leads to the posterior surface of the opisthotic.…”

“…The stapes completely sutures the parasphenoid in adults of Lyrocephaliscus euri (Säve-755 Söderbergh, 1936;Mazin & Janvier, 1983), Eryops megacephalus (Sawin, 1941), Edops craigi (Romer & Witter, 1942), Dissorophus multicintus (DeMar, 1968) and Tersomius texensis (Carroll, 1964), preventing any movements. If the ossification of the stapes is continuous through ontogeny (as demonstrated for long bones based on skeletochronology, see Steyer et al, 2004), this suggests a progressive reduction of the underwater hearing 760 function of the stapes.…”

“…Endocranial structures of temnospondyls are only known from a few exceptionally wellpreserved specimens belonging to Edops craigi Romer, 1936(Romer & Witter, 1942; Eryops 70 megacephalus Cope, 1877(Sawin, 1941; Dvinosaurus egregius Shishkin, 1968(Shishkin, 1973, Benthosuchus sushkini (Efremov, 1929) (Bystrow & Efremov, 1940); Lyrocephaliscus euri (Wiman, 1914) (Säve-Söderbergh, 1936;Mazin & Janvier, 1985); Mastodonsaurus giganteus (Jaeger, 1828) (Schoch, 1999a); and Paracyclotosaurus davidi Watson, 1958. 4/41 (Sigurdsen, 2008) and Gerrothorax pulcherrimus (Fraas, 1913) (Witzmann et al, 2011) have contributed to our knowledge. Nevertheless, the endocranium is still relatively poorly known in temnospondyls.…”