has a fleshy origin in one leg (fig. 20B), but in another, no part
attaches anterior to the femoral notch (thus the muscle is not notched).
In one leg, the insertional tendon is strongly fused to, and continuous
with, the ventral edge of the insertional tendon of M. gluteus
profundus.
_P. p. jamesi_
INDIVIDUAL VARIATION.--The part attaching anterior to the femoral notch
may be mainly or entirely fleshy. In one leg, the part attaching
anterior to the femoral notch is entirely separate from, although
overlapped by, the main part of the muscle for the entire length of the
fleshy belly (fig. 20C); both parts have a common insertional tendon.
=_M. Psoas_= (M. iliacus), Figs. 13, 15, 18
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Small and slender; on medial aspect
of proximal end of thigh lateral to proximal end of M. ambiens;
ventromedial to M. iliotrochantericus medius; proximal end visible from
inside pelvis (medial to inguinal ligament); passes dorsolateral to
inguinal ligament.
ORIGIN.--The muscle arises fleshily from the ventrolateral edge of the
ilium posterior to the femoral notch and ventral (adjacent) to the
origin of M. iliotrochantericus medius.
INSERTION.--The attachment is tendinous to the medial surface of the
femur a short distance proximal to the origin of M. femoritibialis
internus.
INNERVATION.--The posterior division of the femoral nerve, which spirals
completely around M. psoas, gives several twigs into the proximal part.
INDIVIDUAL VARIATION.--None of significance.
_T. cupido_
INDIVIDUAL VARIATION.--In two legs the insertion is partly fleshy.
_P. p. jamesi_
INDIVIDUAL VARIATION.--In one leg the insertion is partly fleshy. The
posterior division of the femoral nerve perforates the muscle in one
instance.
=_M. Flexor Cruris Lateralis_= (M. semitendinosus), Figs. 12, 13, 14,
15, 16, 17
This muscle represents only the main head of the muscle for which Fisher
and Goodman (1955) used the same name. Their accessory head of M. flexor
cruris lateralis is here termed M. femorocruralis.
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Large, thick, and strap-shaped; on
posterior surface of thigh; proximal part bounded anteriorly by Mm.
extensor iliotibialis lateralis and extensor iliofibularis; anterodistal
part deep to latter; bounded medially by Mm. caudofemoralis (proximally)
and flexor cruris medialis (distally); proximal end much narrower than
remainder and posterior to ilium; fused to underlying tough membrane,
which forms body wall posterior to ilium; proximal half of narrow part
aponeurotic; distal part of muscle posterior to M. femorocruralis;
separated from latter by common raphe to which both attach; caudal
muscle (M. transversoanalis) attached aponeurotically to superficial
surface of posteroproximal fleshy part of M. flexor cruris lateralis.
ORIGIN.--The origin is tendinous (superficial surface) and fleshy from
the entire dorsolateral iliac ridge and fleshy from an area of the ilium
below this ridge, also tendinous from the posterior edge of the ilium
medial to the dorsolateral iliac ridge, and also tendinous from the
transverse processes of the first free caudal vertebra and the vertebra
either anterior or posterior to the latter.
INSERTION.--M. flexor cruris lateralis and M. femorocruralis insert
broadly on opposite sides of a long tendinous raphe that extends
parallel to, but some distance posterior to, the distal half of the
femur; the distal end of this tendon broadens somewhat and fuses to the
medial surface of M. gastrocnemius pars media (continuous with the
tendon of the latter); the superficial part of this tendon continues
toward the tibiotarsus, soon fusing to the deep surface of the overlying
tendon of M. flexor cruris medialis; thus the common tendon of M. flexor
cruris lateralis and M. femorocruralis insert in common with both M.
flexor cruris medialis and M. gastrocnemius pars media.
INNERVATION.--A branch of the middle tibial division of the sciatic
nerve enters the substance of M. caudofemoralis pars iliofemoralis, and
emerges near its ventral edge, then passes lateral to M. caudofemoralis
pars caudifemoralis and enters the anterior part of M. flexor cruris
lateralis.
INDIVIDUAL VARIATION.--In three legs, the nerve does not perforate M.
caudofemoralis pars iliofemoralis, but passes deep to it.
_T. cupido_
INDIVIDUAL VARIATION.--In one leg, a small accessory slip arises from
the ventrolateral surface of the caudal musculature and joins the
posterior edge of the main part of M. flexor cruris lateralis a short
distance dorsal to the pubis. In several legs, the nerve does not
perforate M. caudofemoralis pars iliofemoralis, but passes deep to it.
_P. p. jamesi_
DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--The muscle is wider. The
extreme proximal end is fleshy up to its origin, which is fleshy and
tendinous from the vertebrae. The common insertional tendon of M. flexor
cruris lateralis and M. femorocruralis fuses with the distal end of the
fleshy part (instead of tendon) of M. flexor cruris medialis.
INDIVIDUAL VARIATION.--None of significance.
=_M. Flexor Cruris Medialis_= (M. semimembranosus), Figs. 12, 13, 14,
15, 16, 17, 20E
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Most posterior muscle on medial
surface of thigh; long and strap-shaped; bounded anteriorly by M.
adductor profundus; posteroproximal corner of latter medial to
anteroproximal part of M. flexor cruris medialis; bounded laterally by
Mm. caudofemoralis (proximally) and flexor cruris lateralis (distally);
anteroproximal corner adjacent to posteroventral corner of M. flexor
ischiofemoralis and lateral to extreme posteroproximal corner of M.
adductor superficialis; distal end tendinous, extending into proximal
part of shank; bounded medially by M. gastrocnemius pars interna and
laterally by Mm. gastrocnemius pars media and plantaris.
ORIGIN.--The muscle arises by a wide flat tendon from a narrow line on
the lateral surface of the ischium dorsal to the ventral ischiatic
tubercle.
INSERTION.--The wide flat tendon attaches to a narrow line on the medial
surface of the proximal part of the tibiotarsus a short distance
anterior to the proximal part of M. plantaris and deep to M.
gastrocnemius pars interna; the proximal end attaches immediately
anterior to the distal end of the medial collateral ligament. Part of
the common tendon of Mm. flexor cruris lateralis and femorocruralis
fuses with the lateral surface of the tendon of M. flexor cruris
medialis, inserting in common with it.
INNERVATION.--A branch of the middle tibial division of the sciatic
nerve passes deep to both heads of M. caudofemoralis and enters the
anterior part of M. flexor cruris medialis.
INDIVIDUAL VARIATION.--In several legs, the anterior edge of the
proximal part fits into a deep longitudinal groove in the posterior edge
of the proximal part of M. adductor superficialis; the two muscles fuse
slightly at this point.
_T. cupido_
INDIVIDUAL VARIATION.--In two legs, the extreme posterior end of the
origin is from the pubis. In two others, the proximal end is separated
by a slight gap from M. adductor superficialis. The nerve arises from
the posterior (rather than middle) tibial division in one leg.
_P. p. jamesi_
DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--The origin is wider; the
posterior third to half of the origin is fleshy. The entire origin is
from a strongly curved line, the middle part of which attaches to the
ventral edge of the ischium posterior to the ventral ischiatic tubercle.
The insertion is wider. The insertional tendon attaches posterior
(rather than anterior) to the distal end of the medial collateral
ligament; the proximal end of the insertion attaches to the articular
capsule (fig. 20E). The insertional tendon is shorter; as a result, the
common tendon of Mm. flexor cruris lateralis and femorocruralis fuses
with the distal end of the fleshy belly (instead of the tendon) of M.
flexor cruris medialis.
INDIVIDUAL VARIATION.--In two thirds of the legs, the proximal part of
the insertion is fleshy rather than tendinous. In one leg, the middle
part of the insertional tendon splits into two sheets, one attaching
anterior to and one attaching posterior to the distal end of the medial
collateral ligament. The nerve may arise from the posterior tibial
division (two legs), from the middle tibial division (one leg), or as an
independent division of the tibial nerve (three legs). In one leg, the
nerve perforates the lateral part of M. flexor ischiofemoralis.
=_M. Caudofemoralis_= (M. piriformis), Figs. 12, 13, 14, 15, 16, 20J
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Posterior to proximal part of shaft
of femur and deep to M. extensor iliofibularis; posterior part deep to
M. flexor cruris lateralis; bounded medially by Mm. flexor
ischiofemoralis (dorsally), flexor cruris medialis (posteriorly), and
adductor superficialis (anteroventrally); anterior end distal to
anterior end of M. flexor ischiofemoralis; two distinct heads--pars
iliofemoralis and pars caudifemoralis; _pars iliofemoralis_ dorsal to
pars caudifemoralis; posteroventral corner of former overlapped by
latter; pars iliofemoralis wider and much shorter than pars
caudifemoralis; extreme posterior end of pars iliofemoralis fused to
overlying posteroproximal aponeurosis of M. extensor iliotibialis
lateralis; small part of ventral edge sometimes fused with underlying
tendinous posteroproximal corner of M. flexor cruris medialis; entirely
fleshy except for small triangular tendinous area along dorsal margin at
point where branch of middle tibial division of sciatic nerve passes
deep to muscle; _pars caudifemoralis_ long, thin, narrow, and
strap-shaped; overlapping posteroventral corner of ischium; posterior
end of fleshy belly narrowed and forming long slender tendon passing
into caudal musculature; anterior end forming short narrow tendon fused
to deep surface of ventral edge of pars iliofemoralis relatively near
insertion; tendon continuous to insertion; fleshy anterodorsal corner of
pars caudifemoralis slightly overlapped by ventral edge of pars
iliofemoralis; some form of connection usually present between anterior
part of M. caudofemoralis pars caudifemoralis and dorsal end of raphe
between Mm. flexor cruris lateralis and femorocruralis, most often
consisting of narrow weak tendon.
ORIGIN.--_Pars iliofemoralis_: This arises fleshily from the
ventromedial surface of the posterior part of the lateral iliac process,
from the entire lateral ischiatic ridge, and from the lateral surface of
the ischium anterior to this ridge nearly as far forward as the
posterior edge of origin of M. flexor ischiofemoralis; the
posteroventral corner reaches the ventral edge of the ischium and
usually attaches to the ischiopubic membrane posterior to M. flexor
cruris medialis. _Pars caudifemoralis_: This arises by a narrow tendon
from the ventral surface of a broad, thick, tendinous sheet ventral to
the pygostyle, which, in turn, attaches to the ventral surface of the
pygostyle.
INSERTION.--The common belly formed by the union of the two heads
narrows (width variable) and attaches to the posterolateral surface of
the femur distal to the level of insertion of M. iliacus and in contact
with the posterior edge of origin of M. vastus lateralis pars lateralis;
the dorsal part is fleshy and the ventral part is tendinous.
INNERVATION.--A branch of the middle tibial division of the sciatic
nerve gives several twigs to the deep surface of pars iliofemoralis;
another twig enters the substance of pars iliofemoralis and emerges from
the ventral edge of the latter, then enters the dorsal edge of pars
caudifemoralis. The latter twig was not found in all legs, but was
probably destroyed during dissection.
INDIVIDUAL VARIATION.--The tendinous area in the dorsal margin of pars
iliofemoralis is lacking in one leg and extremely small in some others.
In both legs of one specimen, the connection between M. caudofemoralis
pars caudifemoralis and the raphe between Mm. flexor cruris lateralis
and femorocruralis consists of a small (11 × 2 mm.) but well developed
and entirely fleshy muscle slip (fig. 16). In one leg, the ventral third
of this connection is fleshy, the remainder tendinous; in another, this
connection is completely lacking.
_T. cupido_
INDIVIDUAL VARIATION.--The tendinous area in the dorsal margin of pars
iliofemoralis is lacking in one leg. The connection between pars
caudifemoralis and the raphe between Mm. flexor cruris lateralis and
femorocruralis is lacking in several legs. A conspicuous variation
occurring in three legs is the presence of a tendinous area in the belly
of pars caudifemoralis, dividing the latter into proximal and distal
parts (fig. 20J). In one leg, the posteroventral corner of pars
iliofemoralis arises from the pubis. The origin of pars caudifemoralis
in three legs is directly from the anteroventral surface of the
pygostyle. In one instance, the insertional tendon of pars
caudifemoralis is long and extremely slender and extends for some
distance in a groove on the medial surface of pars iliofemoralis before
fusing with the latter.
_P. p. jamesi_
DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--There is no connection at
all between pars caudifemoralis and the raphe between Mm. flexor cruris
lateralis and femorocruralis. The posteroventral corner of pars
iliofemoralis is some distance dorsal to the ventral edge of the ischium
and, therefore, does not attach to the ischiopubic membrane.
INDIVIDUAL VARIATION.--The insertion (narrow) is entirely tendinous in
one leg.
=_M. Flexor Ischiofemoralis_= (M. ischiofemoralis), Figs. 16, 17
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Thick; on lateral surface of
anterior part of ischium; posterior end in lateral iliac fossa; deep to
Mm. extensor iliofibularis and caudofemoralis pars iliofemoralis;
overlapping ventral extrapelvic part of M. obturator and anteroproximal
part of M. adductor superficialis (slightly fused to proximal edge of
latter); posteroventral corner contacting anteroproximal corner of M.
flexor cruris medialis; extreme anterodorsal corner usually overlapped
by tendon of M. piriformis.
ORIGIN.--The muscle arises fleshily from a large area on the lateral
surface of the ischium extending ventrally to the origin of M. adductor
superficialis, anteriorly to the level of the posterior end of the
obturator foramen, dorsally to the ventral border of the ilio-ischiatic
fenestra and to the depth of the lateral iliac fossa, and posteriorly
approximately to the level of the ventral ischiatic tubercle.
INSERTION.--The short flat tendon attaches to the lateral surface of the
femur immediately posterior to the insertion of M. piriformis.
INNERVATION.--The posterior tibial division of the sciatic nerve
penetrates the dorsal surface.
INDIVIDUAL VARIATION.--The ventral part of the insertion may be fleshy.
_T. cupido_
INDIVIDUAL VARIATION.--None of significance.
_P. p. jamesi_
INDIVIDUAL VARIATION.--In all the legs except one, an additional twig
arises from the branch to M. flexor cruris medialis and penetrates the
lateral surface of M. flexor ischiofemoralis. The ventral part of the
insertion is fleshy in one leg.
=_M. Adductor Superficialis_= (M. adductor longus et brevis, pars
externa), Figs. 14, 16, 17
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Posterior to femur, lateral to M.
adductor profundus, and medial to Mm. flexor ischiofemoralis,
caudofemoralis, and femorocruralis; proximal end (fleshy) fused to
proximal tendinous end of M. adductor profundus.
ORIGIN.--The origin is fleshy and tendinous from the proximal end of the
lateral surface of M. adductor profundus and from a narrow line on the
ischium adjacent (dorsal) to the origin of the latter; the posterior
part of the origin sometimes extends farther dorsally on the lateral
surface of the ischium; the origin does not extend so far anteriorly nor
so far posteriorly as the origin of M. adductor profundus; the anterior
edge is at the posterior border of the obturator foramen.
INSERTION.--The attachment is fleshy and thick (distal end thin) to the
posterior surface of the middle part of the femur between the posterior
and posterolateral intermuscular lines; the attachment is adjacent
(lateral) to the insertion of M. adductor profundus and adjacent
(medial) to the origins of Mm. vastus lateralis (proximally) and
femorocruralis (distally); the proximal edge is approximately at the
level of the distal edge of the insertion of M. caudofemoralis.
INNERVATION.--A branch of the obturator nerve emerges from the obturator
foramen dorsal to the tendon of insertion of M. obturator pars postica,
turns ventrally (crossing latter), and passes deep to the anteroproximal
corner of M. adductor superficialis, extending posterodistally between
the adductor muscles and giving twigs to the medial surface of M.
adductor superficialis and to the lateral surface of M. adductor
profundus.
INDIVIDUAL VARIATION.--The anterior edges of the two adductor muscles
are so firmly fused together in some cases that the boundaries cannot be
identified at this point. In several legs, there is a deep longitudinal
groove in the posterior edge of the proximal part of the muscle into
which the anterior edge of M. flexor cruris medialis fits.
_T. cupido_
INDIVIDUAL VARIATION.--In some cases, the anterior edges of the two
adductor muscles are firmly fused together.
_P. p. jamesi_
DIFFERENCES FROM TYPICAL T. PALLIDICINCTUS.--The origin is narrower.
INDIVIDUAL VARIATION.--The anterior edges of the two adductor muscles
may be fused together. In one leg, the entire muscle is
indistinguishably fused with M. adductor profundus and they appear as a
single muscle.
=_M. Adductor Profundus_= (M. adductor longus et brevis, pars interna),
Figs. 13, 15, 17, 18
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Broad; on medial surface of thigh
immediately posterior to femur; bounded posteriorly by M. flexor cruris
medialis (medial to anteroproximal corner of latter), anteriorly by M.
femoritibialis internus (anterior edge overlapped by latter), and
laterally by Mm. adductor superficialis and femorocruralis; proximal end
tendinous (except anterior edge), fused to proximal fleshy end of M.
adductor superficialis.
ORIGIN.--The muscle arises tendinously from the ventral edge of the
ischium extending from the posterior border of the obturator foramen to
the ventral ischiatic tubercle and (anterior edge) fleshily from the
lateral surface of the pubis ventral to the obturator foramen; the
origin is adjacent (ventral) to the origin of M. adductor
superficialis.
INSERTION.--The attachment is fleshy and tendinous from the posterior
intermuscular line and (proximally and distally) from a narrow adjacent
area. Proximally there are often two approximately parallel lines a
short distance apart, representing points of attachment of the lateral
and medial edges of the muscle; if there is only one line proximally, it
may represent the attachment of either the lateral or medial edge of the
muscle; distally there is usually only one line, representing the
lateral edge of the muscle. The distal end extends onto the posterior
surface of the proximal part of the internal condyle, and is adjacent
(lateral) to the origin of M. femoritibialis internus, adjacent (medial)
to Mm. adductor superficialis and femorocruralis, and adjacent
(proximal) to M. gastrocnemius pars media.
INNERVATION.--See M. adductor superficialis.
INDIVIDUAL VARIATION.--The anterior edges of the two adductor muscles
are strongly fused together in some cases.
_T. cupido_
INDIVIDUAL VARIATION.--The anterior edge may be fused with that of M.
adductor superficialis. The distal end is sometimes slightly fused with
M. gastrocnemius pars media. In one leg, the proximal two thirds of the
insertion is entirely tendinous, whereas in another the distal end of
the insertion is tendinous.
_P. p. jamesi_
INDIVIDUAL VARIATION.--The anterior edge (in one leg the entire muscle)
in some legs fuses with that of M. adductor superficialis.
=_M. Obturator_= (M. obturator externus + M. obturator internus), Figs.
16, 17, 18, 19C, D, 20K, L, M
I am adopting the single name M. obturator for the complex that Fisher
(Fisher, 1946; Fisher and Goodman, 1955) subdivides into Mm. obturator
externus and obturator internus. The reasons for this change are given
in the section on terminology.
For ease of description, it is desirable to apply names to the
subdivisions of M. obturator. It has been customary to divide the
obturator complex into two parts--an obturator internus and an obturator
externus; the latter has often been further subdivided. The evidence
given below demonstrates that a primary division of the complex into
only two parts is unsatisfactory.
I strongly suspect that comparable parts of the obturator complex have
been considered a part of the "internus" in some birds and a part of the
"externus" in others. In their work on the Galliformes, Hudson, _et al._
(1959) subdivide the obturator complex into only two
divisions--obturator externus and obturator internus. The extrapelvic
part of this complex that arises from the rim of the obturator foramen
and inserts in common with the stout tendon of the main intrapelvic part
of the obturator internus is considered by them to be a part of the
obturator internus. Their obturator externus lies anterior and deep to
the extrapelvic part of the obturator internus and inserts separately
from the latter. (I also have found this same arrangement in
_Tympanuchus_ and _Pedioecetes_.)
Berger (1952), in his description of the Black-billed Cuckoo (_Coccyzus
erythrophthalmus_), also divides the obturator complex into an obturator
internus and an obturator externus; the latter he subdivides into a
dorsal and a ventral part. He states (p. 530) that he did not find any
measurable differences in myology between _C. erythrophthalmus_ and _C.
americanus_. In order better to compare this arrangement with that in
_Tympanuchus_, I have examined two specimens of _C. americanus_. My
findings in the latter differ from Berger's description (p. 541) in one
respect. Whereas Berger states that the dorsal and ventral parts of M.
obturator externus are distinct except at their origin, I find them
fused for their entire length; the muscle fibers that connect these two
parts lie deep to the tendon of M. obturator internus. The origin of all
parts of the complex in _Coccyzus_ is similar to that in _Tympanuchus_.
The only notable difference in configuration is that the part in
_Coccyzus_ that appears to correspond to the obturator externus of
Hudson, _et al._ (1959) is not separate from the remainder of the
extrapelvic part of the muscle. Berger (1952) considers all parts of the
muscle having an extrapelvic origin to make up the obturator externus.
It appears to me that the dorsal part and a part of the ventral part of
the obturator externus of Berger correspond to the extrapelvic fleshy
part of the obturator internus of Hudson, _et al._
From my limited study, it seems to me to be desirable to recognize four
subdivisions of the obturator complex, for which I propose the terms
pars antica, pars dorsalis, pars ventralis, and pars postica. These
parts exhibit various degrees of fusion in different groups of birds and
some parts appear to be absent in certain birds. A study of a wide
variety of birds will be required to determine whether or not a
subdivision into the four parts proposed here is suitable for birds as a
whole.