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88 ADVANCES IN PALAEOICHTHYOLOGY
dorsal process of the clavicle (Figs. 5B, C). The ventral part of the anterior edge of the
cleithrum is convex. Mesially from the anteroventral process and posteriorly from the
anteromedial depression there is a process parallel to the former, named here the ventral
anteromedial process. Its mesial surface is smooth; it is straight and the ventral tip
projects below the apex of the anteroventral process.
The corresponding part of the posterior edge of the cleithrum is, on the contrary,
concave and its outline almost follows in parallel that of the anterior edge. The contact
with the scapulocoracoid can be easily traced; it follows the sharp ridge of the
posteroventral edge. The posterodorsal edge of the bone is less acute and smoothly
arched in plan view.
The scapulocoracoid (Fig. 5B) is incompletely ossified and only its scapular portion
is partly preserved, in accordance with the condition noted by Holmes (1980) in
Proterogyrinus. This bone is solidly fused to the mesial side of the cleithrum, however,
in contrast to Ichthyostega, Acanthostega and Hynerpeton and in agreement with the
condition in Elginerpeton (Ahlberg 1998) its sutures are fairly well discernible. As
noted above, the posterolateral suture of the scapulocoracoid runs parallel to the
posteroventral edge of the cleithrum. Posterodorsally it is obscured by three shallow
muscle attachment pits, possibly for the analogue of the m. levator scapulae. These pits
are separated anteriorly from the anterodorsal part of the supraglenoid buttress by a
prominent transverse ridge. The anterodorsal crest at this point is robust, ventrally it
reduces in height forming a concavity at the anterior edge of the subscapular fossa,
which would have been large and comparable in configuration to that in Hynerpeton
(Daeschler et al. 1994) and Elginerpeton (Ahlberg 1998). The anteroventral part of the
anterior edge of the scapulocoracoid abuts the dorsal part of the ventral anteromedial
process of the cleithrum. A small supraglenoid foramen is situated close to the
scapulocoracoid-cleithrum suture in the same position as in Hynerpeton and foramen
“C” in Acanthostega (Coates 1996).
Only the distal part of the left femur (PIN 2657/344) is preserved. The major feature
distinguishing it from all other known Devonian tetrapods is the absence of an
intercondylar fossa (Figs. 6, 7) and correspondingly distinctly expressed condyles.
Instead, the dorsal (extensor) surface of the femur in its distal part is almost flat (Fig.
6B). Two shallow ridges, one running along the posterior edge of the dorsal surface and
the other parallel to it roughly in the middle of the surface, form a shallow groove with
uneven surface. The rest of the surface adjoining the tibial condyle is also flat and
pierced with several large blood vessel foramina. Its anterior edge forms an abrupt
bend to the condyle surface. More proximal part of the dorsal surface in the shaft area
is rounded and passes smoothly into the shaft portion of the anterior surface of the
femur. The massive adductor crest running obliquely towards the anterior bone surface
delimits the ventral margin of the anterior surface (Fig. 6A). The distal part of the
anterior surface is dominated by the bulky perichondral mass of the tibial condyle
strongly overhanging and even partly enclosing ventrally the large and deep triangularshaped
popliteal fossa (Figs. 6A, C). The ventral surface of the bone enclosed between
the adductor crest and a sharp ridge separating this surface from the posterior one is
narrow distally but widens in the proximal direction. The latter ridge is situated
topographically in the same position as a well marked unnamed ridge situated at the
ventral side of the femur receiving the distal extremity of the adductor crest and separating