MYOLOGY

The jaw musculature of doves is not an imposing system. The eating

habits impose no considerable stress on the muscles; the mandibles are

not used for crushing seeds, spearing, drilling, gaping, or probing as

are the mandibles of many other kinds of birds. Doves use their

mandibles to procure loose seeds and grains, which constitute the major

part of their diet (Leopold, 1943; Kiel and Harris, 1956: 377; Knappen,

1938; Jackson, 1941), and to gather twigs for construction of nests.

Both activities require but limited gripping action of mandibles. The

crushing habit of a bird such as the Hawfinch (_Coccothraustes

coccothraustes_), on the other hand, involves extremely powerful

gripping (see, for example, Sims, 1955); the contrast is apparent in

the development of the jaw musculature in the two types. Consequently,

it is not surprising to find a relatively weak muscle mass in the jaw

of doves, and because the musculature is weak there are few pronounced

osseous fossae, cristae and tubercles. As a result, the bones, in

addition to being small in absolute size, are relatively weaker when

compared to skulls of birds having more distinctive feeding habits

which require more powerful musculature.

The jaw muscles of the species dissected for this study are, in gross

form, nearly identical from one species to another. Thus, a description

of the pertinent myology of each species is unnecessary; one basic

description is hereby furnished, with remarks on the variability

observed between the species.

The terminology adopted by me for the jaw musculature is in boldfaced

italic type. Synonyms are in italic type and are the names most often

used by several other writers.

~_M. pterygoideus ventralis:_~ part of Mm. pterygoidei, Gadow,

1891:323-325, table 26, figs. 1, 2, 3 and 4, and table 27,

fig. 3--part of M. pterygoideus internus, Shufeldt, 1890:20,

figs. 3, 5, 6, 7 and 11--part of M. adductor mandibulae

internus, Edgeworth, 1935:58, figs. 605c and 607--part of M.

pterygoideus anterior, Adams, 1919:101, pl. 8, figs. 2 and 3.

~_M. pterygoideus dorsalis:_~ part of Mm. pterygoidei,

Gadow, 1891:323-325, table 26, fig. 7 and table 27, figs. 1

and 3--part of M. pterygoideus internus, Shufeldt,

1890:20--part of M. adductor mandibulae internus, Edgeworth,

1935:58, fig. 605c--? part of M. pterygoideus anterior,

Adams, 1919:101, pl. 8, figs. 2 and 3.

~_M. adductor mandibulae externus:_~ _a_) ~_pars

superficialis:_~ parts 1 and 2 of M. temporalis, Gadow,

1891:320-321--part of M. temporal, Shufeldt, 1890:16,

figs. 5 and 7--part of M. adductor mandibulae externus,

Edgeworth, 1935:58-60--M. capiti-mandibularis medius and

profundus, Adams, 1919:101, pl. 8, fig. 1.

_b_) ~_pars medialis:_~ ? parts 1, 2 and 3 of M. temporalis,

Gadow, 1891:320-322--part of M. masseter and ? part of M.

temporal, Shufeldt, 1890:16-18, figs. 5, 6, 7 and 11--part

of M. adductor mandibulae externus, Edgeworth,

1935:58-60--M. capiti-mandibularis superficialis, first

part, Adams, 1919:100-101, pl. 8, fig. 1.

_c_) ~_pars profundus:_~ part 2 of M. temporalis, Gadow,

1891:321, table 27, fig. 2--part of M. temporal and ? part

of M. masseter, Shufeldt, 1890:16-18--part of M. adductor

mandibulae externus, Edgeworth, 1935:58-60--? part of M.

capiti-mandibularis medius and all of pars superficialis,

second part, Adams, 1919:100-101.

~_M. pseudotemporalis profundus:_~ M. quadrato-maxillaris,

Gadow, 1891:322-323--M. pterygoideus externus, Shufeldt,

1890:20-21, figs. 3, 5 and 11--part of M. adductor mandibulae

medius, Edgeworth, 1935:58-59--? part of M. pterygoideus

posterior, Adams, 1919:101, pl. 8, figs. 2 and 3.

~_M. protractor pterygoidei:_~ part 4b of M. temporalis,

Gadow, 1891: 322-323, table 27, fig. 4--part of M.

entotympanious, Shufeldt, 1890:19-20, figs. 3 and 11--part

of M. spheno-pterygo-quadratus, Edgeworth, 1935:57.

~_M. depressor mandibulae:_~ M. digastricus s. depressor

mandibulae, Gadow, 1891:318-319--M. biventer maxillae,

Shufeldt, 1890:18-19, figs. 3, 4, 5, 6, 7 and 11.

~_M. pseudotemporalis superficialis:_~ M. spheno-maxillaris,

Gadow, 1891:323--part of M. temporal, Shufeldt, 1890:16--part

of M. pseudotemporalis, Hofer, 1950:468-477--part of M.

adductor mandibulae medius, Edgeworth, 1935:277.

~_M. adductor mandibulae posterior:_~ ? part of M. temporal,

Shufeldt, 1890:16--part of M. adductor mandibulae medius,

Edgeworth, 1935:58-59--? part of M. pterygoideus posterior,

Adams, 1919:101, pl. 8, figs. 2 and 3.

~_M. protractor quadrati:_~ part 4a of M. temporalis, Gadow,

1891:322-323, table 27, fig. 4--part of M. entotympanicus,

Shufeldt, 1890:19-20, figs. 3 and 11--part of M.

spheno-pterygo-quadratus, Edgeworth, 1935:57.

The terminology adopted by me is that of Lakjar (1926) except that the

divisions of _M. depressor mandibulae_ are designated by the Latinized

equivalents of the names used by Rooth (1953:261-262).

~_M. pterygoideus ventralis lateralis._~--The origin is fleshy and by

aponeurosis on the ventral side of the palatine anterior to the

palatine fossa. The insertion is fleshy on the ventromedial surface of

the lower mandible and continues along the anteromedial surface of the

internal angular process to its distal tip. A few fibers leave _pars

lateralis_ and insert on an aponeurosis which receives also all the

fibers of _M. pterygoideus dorsalis lateralis_. The latter fact may

have prompted Rooth (1953:257) to make the statement that the fibers

originating on the dorsal part of the palatine inserted more laterally

than those originating on the ventral side. Rooth worked with _Columba

palumbus_, the Woodpigeon, and his description concerned _M. adductor

mandibulae internus pterygoideus_, which is composed of _Mm.

pterygoideus ventralis et dorsalis_ of Lakjar (1926). His assertion

that ventral fibers, that is to say, fibers arising on the ventral

surface of the palatine, insert medially does not appear to be

completely true for doves.

Aponeuroses cover most of the lower surface of the muscle and one or

two nerves extend into the substance of the muscle. The nerves run from

the anterior edge of _M. pterygoideus dorsalis medialis_ and farther

posteriorly from a separation in the muscle.

~_M. pterygoideus ventralis medialis._~--The origin is by aponeurosis

from the ventral surface of the palatine and fleshy from the palatine

fossa. The aponeurosis is the same that gives origin to the fibers of

_pars lateralis_. Part of the aponeurosis becomes tendonlike in the

middle of _M. pterygoideus ventralis_ and separates its two divisions.

The insertion is fleshy on the lower one-third of the anterior surface

of the internal angular process of the lower mandible, and by two

tendons on the distal tip of that process. Many of the fibers of _pars

medialis_ insert on the tendons. The fibers at their insertion are not

distinctly separate from those of _pars lateralis_ and there is

considerable mingling of the fibers. Consequently, the medial part of

_M. pterygoideus ventralis_ cannot be removed as a part distinct from

the lateral part (figs. 1, 4, 10, 21 and 22).

Ordinarily _M. pterygoideus ventralis_ does not cross the ventral edge

of the lower mandible, but in one white-wing the muscle was slightly

expanded on the right side and it could be seen in lateral view. The

homologous muscle in _Columba palumbus_ apparently is consistently

visible in lateral view. (See Rooth, 1953, fig. 6.)

~_M. pterygoideus dorsalis medialis._~--The origin is fleshy on the

dorsolateral surface of the palatine immediately anterior to the

pterygoid and also on the anterior, dorsolateral, posterior and

ventromedial surfaces of the pterygoid. The insertion is fleshy on the

ventromedial surface of the lower mandible and the anterior surface of

the internal angular process immediately dorsal to the insertion of _M.

pterygoideus ventralis lateralis_.

~_M. pterygoideus dorsalis lateralis._~--The origin is fleshy from the

dorsolateral surface of the palatine, anterior to the origin of _pars

medialis_ and the insertion is by means of an aponeurosis on the medial

surface of the lower mandible, lateral to the insertion of _M.

pterygoideus ventralis lateralis_. The aponeurosis crosses the medial

side of the insertion of _M. pterygoideus dorsalis medialis_. The

fibers run in a posteroventrolateral direction and insert on the

ventromedial side of the aponeurosis (figs. 1, 6, 8, 9, 13-22).

In one individual, a Mourning Dove, the origin of _pars lateralis_ of

_M. pterygoideus dorsalis_ extended to the pterygoid. With this one

exception the muscle was uniform throughout the several species.

~_M. adductor mandibulae externus._~--This is the most complex muscle

in the jaw owing to its system of tendons and aponeuroses. Three

divisions of this muscle were described by Lakjar (1926:45-46) and the

divisions appear to be distinguishable in the doves, but there is no

clear line of demarcation for any of the parts and the following

description is based upon my own attempts to delineate the muscle.

~_M. adductor mandibulae externus superficialis._~--The origin is

fleshy from the most lateral area of the temporal fossa. Dorsally the

origin is bounded by the base of the postorbital process and ventrally

by the temporal process. The fibers converge upon a tendon that passes

beneath the postorbital ligament and runs anteriorly among the fibers

of _pars profundus_. The insertion is tendinous on the dorsal surface

of the lower mandible in common with the dorsal aponeurosis of _pars

profundus_. The insertion is immediately anterior to the ventral

aponeurosis of _pars profundus_ near the medial edge of the dorsal

surface on a tubercle at the posterior end of the dorsal ridge of the

lower mandible.

~_M. adductor mandibulae externus medialis._~--The origin is by a flat,

heavy tendon from the temporal process. The tendon is attached almost

vertically on the temporal process. It twists approximately 130 deg. as

it runs anteriorly, and becomes a thin aponeurosis, which gives rise on

its dorsal and ventral surfaces to many fibers that insert in a

fan-shaped area on the mandibular fossa. Fibers from the dorsal and

dorsomedial sides of the heavy tendon run rostrad and insert on the

ventral surface of the dorsal aponeurosis of _pars profundus_. From the

ventral surface the most posterior fibers converge on an aponeurosis

that inserts on a transverse crista on the dorsal surface of the

mandible immediately lateral to the ventral aponeurosis of _pars

profundus_ and dorsal to the insertion of ~_M. adductor mandibulae

posterior_~. The more anterior fibers insert fleshily on the mandibular

fossa. The tendon of origin is actually one with the ventral

aponeurosis of _pars profundus_, which is situated in a horizontal

plane. The insertion is primarily a fleshy attachment on the mandibular

fossa. Some of the fibers that arise on the dorsomedial and lateral

surfaces of the tendon of origin attach to another tendon, which

inserts in the midline of the mandibular fossa on a small tubercle near

the anterior end. Also, there is insertion by an aponeurosis anterior

to _M. adductor mandibular posterior_ as stated above. Fibers attach to

the dorsal and ventral side of the aponeurosis.

~_M. adductor mandibulae externus profundus._~--The origin is fleshy

from the medial surface of the temporal fossa, the posterior wall of

the orbit and the otic process of the quadrate. The origin is bounded

laterally by the origin of _pars superficialis_ and medially by the

origin of _M. pseudotemporalis superficialis_. Ventrally the muscle

lies against its own ventral aponeurosis, which originates on the

posterior wall of the orbit immediately above the articulation of the

otic process of the quadrate, and which also receives many fibers from

the surface of the quadrate. The insertion is primarily by means of two

aponeuroses. The most dorsal aponeurosis inserts on a tubercle at the

posterior tip of the dorsal edge of the mandible. The lateral tendon of

_M. pseudotemporalis superficialis_ converges with the aponeurosis. It

is superficial and there are no fibers on its dorsal surface. The

ventral aponeurosis inserts on a crista immediately below the insertion

of the dorsal aponeurosis. It receives fibers on its ventral surface

from the otic process of the quadrate, and on its dorsal surface gives

rise to fibers that insert on the dorsal aponeurosis (figs. 2, 3, 5, 9,

10, 11, 13-18).

The tendon of insertion of _pars medialis_ of _M. adductor mandibulae

externus_ does not become a superficial aponeurosis posteriorly in the

Zenaida Dove as it does in the Mourning and White-winged doves.

~_M. pseudotemporalis profundus._~--The origin is fleshy from the

medial and partially from the dorsal surface of the lower mandible. The

origin is almost completely anterior to and partly dorsal and ventral

to the medial (most anterior) insertion of _M. pseudotemporalis

superficialis_. The anterior margin of the origin is at the point where

the mandibular ramus of the trigeminal nerve enters the mandible.

Posteriorly the origin is bounded by the insertion of _M. adductor

mandibulae posterior_, and ventrally by a ridge that is situated about

halfway down the medial side of the mandible. The insertion is by

aponeurosis on the tip of the orbital process of the quadrate and

fleshily on the anterior surface of the same process. The aponeurosis

extends about three-fifths of the distance along the muscle and it is

dorsal or superficial to all of the fibers. Many fibers insert on the

ventral side of the aponeurosis (figs. 1, 5, 13, 14, 15, 16, 21 and

22).

This muscle is the most variable of all the jaw muscles. In the

Mourning Dove the muscle appears rather slender in dorsal view and in

the White-winged Dove has an enlarged lateral belly that gives the

appearance of a thicker muscle. In the Zenaida Dove _M.

pseudotemporalis profundus_ is intermediate in shape between those of

the other two species. This muscle will be discussed in detail later.

~_M. protractor pterygoidei._~--The origin is fleshy from the junction

of the sphenoidal rostrum and the interorbital septum. Fibers converge

on the pterygoid in anteroventrolateral and posteroventrolateral

directions. The posterior edge of the muscle is in contact with _M.

protractor quadrati_ with which its fibers mingle. The insertion is

fleshy on the posterior surface of the lateral half of the pterygoid to

its articulation with the body of the quadrate (figs. 6, 8, 9, 11,

13-20).

~_M. depressor mandibulae superficialis medialis._~--The origin is

fleshy from the lateral edge of the basioccipital where the muscle is

attached to _Ligamentum depressor mandibulae_ and extends in a lateral

direction to a point where the structures involved turn dorsad. The

insertion is by fibers and a light aponeurosis on the crista that is

situated on the posteroventromedial edge of the lower mandible.

~_M. depressor mandibulae superficialis lateralis._~--The origin is

fleshy from the squamosal region, slightly posteroventral to the origin

of _M. adductor mandibulae externus superficialis_. A thin aponeurosis

lies medial to the muscle fibers. The insertion is by means of an

aponeurosis that becomes tendonlike along the posteroventrolateral

crista and the posteriormost part of the ventral edge of the lower

mandible.

~_M. depressor mandibulae medialis._~--The origin is fleshy from the

lateral and ventral surfaces of _Ligamentum depressor mandibulae_. The

insertion is fleshy on the posterior surface of the lower mandible,

posterodorsal to the insertions of _partes superficialis medialis et

lateralis_ (figs. 4, 9, 10, 13 and 14).

The parts of _M. depressor mandibulae_ are difficult to distinguish

from one another because of considerable intermingling of fibers.

~_M. pseudotemporalis superficialis._~--The origin is fleshy from the

posterior wall of the orbit, dorsal to the foramen of the trigeminal

nerve, lateral to the origin of _M. protractor quadrati_ and medial to

_M. adductor mandibulae externus profundus_. The insertion is by means

of an aponeurosis that bifurcates at the point of contact with the

mandibular ramus of the trigeminal nerve, which is at the level of the

orbital process of the quadrate (except in the Mourning Dove where the

division is more anterior), and which inserts as two tendons on the

dorsomedial edge of the lower mandible posterior to the insertion of

_M. pseudotemporalis profundus_. The lateral tendon is superficial to

the dorsomedial edge of _M. adductor mandibulae externus_, and

converges with the aponeurosis of _pars profundus_ of that muscle and

inserts with it on a tubercle near the dorsomedial edge of the

mandible anterior to the insertion of _M. adductor mandibulae

posterior_ as mentioned before. The anterior half of the medial tendon

lies ventral to the lateral edge of _M. pseudotemporalis profundus_ and

the mandibular ramus of the trigeminal nerve. All of the fibers of the

muscle insert on the posteroventral surface of the aponeurosis before

it divides. Part of _M. pseudotemporalis profundus_ also lies ventral

to the medial tendon of _M. pseudotemporalis superficialis_ and, in

effect, the tendon is imbedded in the substance of _M. pseudotemporalis

profundus_ as it proceeds anteriorly. The trigeminal nerve leaves a

slight impression on the ventral surface of the muscle near its origin

(figs. 1, 3, 11, 13, 14, 15 and 16).

~_M. adductor mandibulae posterior._~--The origin is fleshy from the

anterodorsal and anterior surfaces of the quadrate body, from the

anterodorsolateral, medial and anterior surfaces of the orbital process

of the quadrate. The muscle also has an origin from the otic process of

the quadrate, partly fleshy and partly by a slight aponeurosis. The

insertion is fleshy on the dorsal and lateral surfaces of the mandible

immediately anterior to the articulating surface. This muscle also has

extensive insertion on the medial side of the lower mandible dorsal to

the insertion of _M. pterygoideus dorsalis medialis_ and posterior to

the origin of _M. pseudotemporalis profundus_ (figs. 1, 3, 5, 17, 18,

19 and 20).

The fibers of _M. pseudotemporalis profundus_ can be distinguished from

the fibers of _M. adductor mandibulae posterior_ because the

pterygoideus nerve passes between the two (Lakjar, 1926:55). Rooth

(1953:255-256) considers as part of this muscle the ventral aponeurosis

of _pars profundus_ of _M. adductor mandibulae externus_ and all the

fibers ventral to it. But I could not justify the inclusion of that

aponeurosis as part of _M. adductor mandibulae posterior_ in the doves

because none of the fibers of _M. adductor mandibulae posterior_ as I

have described it were attached to that particular aponeurosis.

~_M. protractor quadrati._~--The origin is fleshy from the posterior

wall of the orbit medial to the foramen of the trigeminal nerve and

also medial to the origin of _M. pseudotemporalis superficialis_. The

origin describes an arc in the horizontal plane until it reaches the

interorbital septum and the optic nerve. The insertion is fleshy on the

posteromedial edge of the body of the quadrate and the orbital process

of the quadrate and on the otic process of the quadrate. The muscle

also inserts on the ventromedial surface of the orbital process of the

quadrate and the adjacent area of the body of the quadrate (figs. 5, 7,

9, 11, 13-18).

_M. protractor quadrati_ possesses many fibers that arise from _M.

protractor pterygoidei_. Consequently, it is difficult to determine the

exact extent of the origin or the insertion of either muscle.