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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 124, No. 2, June 2012 
ventral margin of the proximal two-thirds of the 
ischium, and the adjacent pubis. There is a large, 
triangular, tendinous sheet in the caudoproximal 
part of the belly. The tendinous insertion occupies 
a long line on the caudal surface of more than the 
distal two-thirds of the femur. The origin of the 
superficial pars lateralis is partly fleshy, dorsal to 
the origin of pars medialis, and constricted to the 
ventral margin of the middle half of the ischium. 
The insertion is mainly Heshy on the caudal 
surface of the femoral shaft, lateral to that of pars 
medialis. 
M. tibialis cranialis (Figs. 2, 4: TC) has two 
heads of origin, one by a short tendon from the 
distal end of the condylus lateralis of the femur, 
the other mainly by fleshy fibers from cristae 
cnemialis cranialis and lateralis, and crista 
patellaris of the tibiotarsus. The well-developed 
belly occupies the cranial portion of the proximal 
two-thirds of the tibiotarsus, immediately beneath 
the M. fibularis longus. The stout tendon of 
insertion is ossified before passing beneath the 
fibrous loop near the distal end of the tibiotarsus. 
The tendon inserts on tuberositas m. tibialis 
cranialis on the proximal tarsometatarsus after 
traversing the intertarsal joint. 
M. extensor digitorutn longus (Figs. 4. 5: EDL) 
lies deep to M. tibialis cranialis. This bipennatc 
muscle arises fleshy from cristae cnemialis 
cranialis and lateralis, and sulcus interenemialis 
of the tibiotarsus. The belly extends downward 
from its origin and becomes gradually narrowed 
before merging with the tendon at about the 
proximal end of the distal third of the bone. The 
distal part of the tendon is ossified and passes 
through the fibrous loop shortly above the 
condyles in company with that of M. tibialis 
cranialis. Just below this fibrous loop, it passes 
alone beneath pons supratendineus before travers¬ 
ing the cranial side of the intertarsal joint. The 
tendon continues its course along the craniolateral 
surface of the tarsometatarsus. first passing 
beneath a fibrous loop near the proximal end of 
this bone, then bifurcating near the proximal end 
of the distal three-fifths of the tarsometatarsus. 
The medial branch supplies Dig. II and sends a 
tendon to the medial side of Dig. Ill: the lateral 
branch bifurcates to the lateral side of Dig. HI and 
to Dig. IV. The individual branch inserts on the 
dorsal surface of each phalanx of the correspond¬ 
ing toe. More than the proximal half of the tendon 
is ossilicd along the cranial surface of the 
tarsometatarsus. 
M. fibularis longus (Fig. 1: FL) is the superfi¬ 
cial musculature on the craniolateral surface of ilk- 
lower leg. and arises mainly by aponeurosis from 
the cranial and lateral cnemial crests, and the 
craniomcdial surface of the proximal tibiotarsus, 
The flat, fusiform belly is confined to the 
proximal two-thirds of the lower leg and close!;, 
attached to M. tibialis cranialis and the pars 
medialis of M. gastrocnemius and M. flexor 
perforans et perforatus digiti III. which lie deep, 
medial and dorsal to it. respectively. The ossified 
tendon is formed at about the middle of the lower 
leg. It is wider proximally and narrows as it passes 
caudolaterally. The tendon is unossified jusi 
above the condylus lateralis and sends a short 
caudal branch to the proximal end of the lateral 
side of the cartilage tibialis. The cranial mam 
branch passes a bony canal at the distal end of the 
shaft, then continues distally over the lateral side 
of the intertarsal joint, and finally inserts on the 
cranial edge of the ossified tendon of M. flexor 
perforans digiti 111, a short distance inferior to the 
hypotarsus. 
M. fibularis brevis (Figs. 1, 2. 4, 5: FB) is a 
relatively weak, bipennate muscle. It originates 
mainly bv fleshy fibers from the craniolateral 
surface of the tibiotarsus and the adjacent surface 
of the fibula, beginning just distal to the insertion 
ol M. iliofibularis to the distal sixth of the lower 
leg. The tendon of insertion is held in place by 
passing through a small fibrous canal just above 
the lateral condyle. It then crosses the intertarsal 
joint, and inserts on the lateroproximal end of the 
tarsometatarsus. The distal end of the belly and 
the proximal end of the tendon enclose a 
sesamoid. 
M. gastrocnemius is the largest and most 
superficial muscle on the medial and caudal 
surface of the lower leg. It is composed of three 
separate origins and bellies that join to form one 
combined tendon. The tendon covers the posterior 
surface of the tibial cartilage and inserts on the 
caudal surface of the hypotarsus and tarsometa- 
tarsus. Pars lateralis (Fig. 1: GAL) arises hv a 
short tendon from the lateral surface of the lateral 
condyle of the femur. The origin tendon i> 
partially fused with the proximal end of the lateral 
arm of the ansa m. iliofibularis. The belly extends 
a little less than two-thirds the way down the 
lower leg and ends on an ossified tendon. 
Pars intermedia is the smallest of the three parts 
of M. gastrocnemius and arises by fleshy fibers 
from caudomedial surface of condylus medialis of 
