GEORGE R. Z The Distribution and

Patterns of the Major

Arteries of the Iguanids

and Comments on the

Intergeneric Relationships

of Iguanids A

Reptilia: Lacertilia)

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY NUMBER 83
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SMITHSONIAN CONTRIBUTIONS TO

ZOOLOGY

NUMBER 83

George R.Zug The Distribution and

Patterns of the Major

Arteries of the Iguanids

and Comments on the

Intergeneric Relationships

of Iguanids

(Reptilia: Lacertilia)

SMITHSONIAN INSTITUTION PRESS

CITY OF WASHINGTON
ABSTRACT

Zug, George R. The Distribution and Patterns of the Major Arteries of the

Iguanids and Comments on the Intergeneric Relationships of Iguanids (Reptilia:

Lacertilia). Smithsonian Contributions to Zoology, 83: 1-23. 1971.—The spatial arrangement of the major arteries, i.e., systemic arches, carotid arches and

major branches, subclavians, coeliac, and mesenteries, are described for 42 genera

of iguanid lizards. The arterial patterns are relatively uniform in iguanids. All of

iguanids examined had carotid ducts, lacked a primary common carotid, and

with the exception of Iguana, the coeliac arose anterior to or adjacent to the

mesenteries. Variation was observed in the type of origin of the external carotid

and sternohyoid, subclavians, and mesenteries. These pairs of vessels could arise

separately, contiguous, or form a common trunk.

Ten arterial characters were analyzed to determine their taxonomic value.

Comparison of similarly generated phenograms, one for arterial data and the

other for extant iguanid data, showed the arterial characters to be of little value

for intrafamilial classification. The arterial data can function only as a weak

indicator of relationships.

Official publication date is handstamped in a limited number of initial copies and is recorded

in the Institution's annual report, Smithsonian Year.

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For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 - Price 40 cents (paper cover)
George R.Zug The Distribution and

Patterns of the Major

Arteries of the Iguanids

and Comments on the

Intergeneric Relationships

of Iguanids

(Reptilia: Lacertilia)

Introduction

The current systematic revolution revolves around

the search for new characters and methods of character analysis. The saurian arterial system possesses

a diversity of patterns, yet it has remained unanalyzed. Diversity is a prerequisite for determining phylogenetic relationships. Uniformity indicates

only the possibility of taxon derivation from a common ancestor but not the degree and form of intragroup relationships which are provided by diversity

(Throckmorton, 1968; Wake and Ozeti, 1969). Diversity, however, must be balanced with uniformity,

for excessive and discordant variation within the

taxon will mask the relationships. My objectives

have been to determine the patterns and amounts

of variation in the arterial system of lizards. The

iguanids were selected for a critical analysis of pattern variation, since the recent investigations of

Etheridge, e.g., 1959, 1964, 1967, show them to be

a natural assemblage of lizards and provide a basis

for an interpretation of intragroup relationships.

George R. Zug, Department of Vertebrate Zoology, National

Museum of Natural History, Smithsonian Institution, Washington, D. C. 20560.

Saurian Arterial System: A Selective Literature

Review

Corti's 1847 thesis on the circulatory system of

Varanus griseus generally is accepted as the first detailed description of the saurian circulatory system.

His description was based on two specimens, one

with the arteries injected. In 1857, Rathke published a survey of the aortic arches and its branches

in approximately fifty species of lizards and of the

visceral arteries of a similar number of lizards in

1863. Rathke's investigations were the first and most

valuable comparative surveys of the saurian arterial

system. His work clearly illustrated the existence of

different arterial arrangements, although his attempt to examine representatives of most saurian

families caused his data to be too superficial for

purposes of classification.

In 1886, two articles on the saurian arterial system appeared. Mackay described the arterial system

of Chamaeleo vulgaris. He noted that it was very

different from that of other lizards, although he

did not mention which other lizards. Van Bemmelen compared the aortic arches of Lacerta

muralis to those of a snake and birds. Shufeldt
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

(1890) provided a brief description of the arterial

system of Heloderma in his anatomical investigation

of this genus.

At the beginning of the twentieth century, Beddard published a series of articles, e.g., 1904, 1905,

1906, 1907, on the vascular system of lizards. His

interest in the classification of lizards led him to

draw some systematic conclusions based on the

vascular system. Shindo's (1914) survey of reptilian

cranial arteries contains data on the saurian condition and is of particular interest for its topographic

details. In 1920, O'Donoghue presented a detailed

study of the circulatory system in Sphenodon. Although his study was not concerned primarily with

lizards, he synthesized the published data on lizards

and provided the framework and terminology for

most subsequent investigations.

Three Indian genera of lizards were examined in

the 1920s and 1930s. Thapar (1923) compared the

arterial system of Varanus to those of Uromastix

and Hemidactylus. Bhatia and associate (1929, 1933)

extended and corrected Thapar's data on Uromastix and Hemidactylus. Additional information on

the lizards of this region was published by Meinertz

(1952) on Varanus, de Silva (1956a and b) on

Calotes, and Kashyap and Nigwekar (1964) on

Riopa.

Adams published a series of articles (1952, 1953,

1957a and b) on the carotid arch—all contain

valuable information on the saurian condition.

Sidky (1967) described carotid sinus of Chalcides

and Scincus. Oelrich (1956) gave topographic details for the cranial arteries of the iguanid Ctenosaura. Burda (1966) described the development of

intracranial arteries in Lacerta.

Material and Methods

IGUANID ARTERIAL SYSTEM.—The following description serves two purposes: (1) To familiarize the

reader with the topographic relationships of the

saurian arterial system and to indicate the vessels

examined, i.e., the names in this section that are

printed in bold type; (2) to provide sufficient details so that concise repetitive descriptions are

possible. Figure 2 provides a stylized illustration of

arterial arrangement.

The heart lies at the anterior end of the body

cavity between the forelimbs. Externally two large

vessels originate from the anterior end of the ventricle. Both are displaced dextrally of the ventricle's

midline. The pulmonary arch arises ventrally and

the systemic arch dorsally. Both extend anteriorly

between the atria. The pulmonary arch curves dextrally and dorsally. Concurrently the systemic arch

curves sinistrally and ventrally. As the two arches

diverge, the systemic bifurcates into right and left

branches. The branches cover ventrally the pulmonary arch and its bilateral bifurcation. Each

systemic arch curves laterally along the anterior

edge of its adjacent atrium.

The common carotid arteries arise paired from

the right systemic (systemocarotid of some authors)

as the latter begins its lateral course. A primary

carotid artery does not exist. The common carotids

pass laterally along the anterior margins of their

respective systemic arches and continue dorsolaterally to the ventral side of the internal jugular

veins. The common carotid divides beneath the

internal jugular. Three arteries, sternohyoid, external carotid and internal carotid, arise from this

division in several different arrangements. The

small sternohyoid extends ventrolaterally and bifurcates into an anterior branch to the ventral

throat musculature and frequently to the thyroid

gland and the posterior branch to the pectoral girdle. The external carotid passes anteriorly along the

ventral surface of the internal jugular vein to the

level of the thyroid gland and bifurcates. A small

branch supplies the anterior part of the esophagus

and thyroid gland. The major arterial supply of

the thyroid gland, however, is derived from the

paired laryngotracheal arteries, which arise from

the pulmonary arches. The larger lateral branch

of the external carotid, hyomandibular artery,

passes to the posterior base of the mandible and

divides into numerous branches.

The internal carotid artery extends dorsally

along the medial surface of the internal jugular.

Its posteriomedial face is continuous with the carotid gland. Dorsally at the body wall, the internal

carotid bifurcates. The posterior branch, carotid

duct, passes caudally and joins the systemic arch at

the beginning of the latter's posterior course. The

anterior branch, the internal carotid, extends

anteriorly along the medial edge of the internal jugular and enters the base of the skull. It is accompanied on its anterior course by a branch of the

musculocervical artery. The musculocervical artery

arises from the dorsal surface of the carotid duct
NUMBER 83

and has numerous small branches supplying the

cervical muscles, glands, and digestive tract.

At the lateral edge of the atria, the systemic

arches curve sharply dorsally. They pass medial to

the internal jugular and curve posteriorly as they

reach the body wall. The left systemic arch gives

off several small esophageal arteries before joining

with the right systemic to form the dorsal aorta.

The left and right subclavian arteries arise from

the right systemic near the axillary plane. If they

arise separately, the left is usually displaced posteriorad of the right. A vertebral artery may arise

dorsally from the right systemic near the subclavians or proximally from the left subclavian. The

vertebral artery has a number of branches to the

esophagus and a major branch extending dorsally

into the neck. Posterior to the subclavians, the

paired parietal arteries appear in every segment.

The first pair of parietals may originate from their

respective subclavians. An irregular number of

small gastric arteries extend ventrally from the

aorta to the dorsal surface of the stomach.

Three large arteries arise from the aorta and

extend to the digestive tract. The sequence of

origin—anterior to posterior—is usually coeliac,

inferior mesenteric, and superior mesenteric. The

inferior mesenteric supplies the posterior end of the

small intestine, the caecum, and the large intestine.

The superior mesenteric extends to the middle and

anterior end of the small intestine, the posterior

part of the pancreas, the pyloric region of the

stomach, and generally to the liver in the region of

the gall bladder. Unlike the former two arteries, the

coeliac originates from the sinistral surface of the

aorta rather than the ventral surface. The coeliac

supplies most of the stomach, the spleen, and the

anterior part of the pancreas.

SPECIMENS EXAMINED.—All specimens listed below with the exception of an Iguana from a biological supply-house, did not have the arteries

injected and are a part of the United States National Museum of Natural History herpetological

collection. The number in parentheses denotes the

number of specimens examined.

Anolines: Anisolepis undulatus (1), Anolis frazeri

(Alpha Group) (1), Anolis peter si (Beta Group)

(3), Anolis vermiculatus (Alpha Group) (2), Chamaeleolis chamaeleontid.es (1), Chamaeleolis porcus

(1), Phenacosaurus heterodermus (2), Polychrus

marmoratus (3).

Basiliscines: Basiliscus basiliscus (2), Basiliscus

galeritus (2), Basiliscus plumifrons (1), Basiliscus

vittatus (1), Corytophanes hernandesi (2), Laemanctus longipes (2).

Iguanines: Amblyrhynchus cristatus (2), Brachylophus fasciatus (1), Ctenosaura acanthura (1),

Ctenosaura hemilopha (1), Ctenosaura similis (1),

Cyclura carinata (2), Cyclura macleayi (1), Dipsosaurus dorsalis (2), Iguana iguana (4), Sauromalus

obesus (2).

Sceloporines: Callisaurus draconoides (2), Crotaphytus collaris (3), Gambelia wislizeni (2), Holbrookia maculata (1), Holbrookia texana (2),

Petrosaurus mearnsi (1), Petrosaurus thalassinus

(2), Phrynosoma asio (1), Phrynosoma coronatum

(2), Phrynosoma douglassi (1), Phrynosoma orbiculare (1), Sceloporus cyanogenys (2), Sceloporus

magister (2), Uma notata (1), Urosaurus ornatus

(2), Uta stansburiana (3).

Tropidurines: Ctenoblepharis jamesi (1), Leiocephalus carinatus (3), Liolaemus elongatus (1),

Liolaemus fitzingeri (2), Ophryoessoides guentheri

(2), Plica plica (3), Plica umbra (1), Stenocercus

crassicaudatus (2), Tropidurus delanonis (2),

Tropidurus hispidus (1), Tropidurus peruvianus

(1), Uracentron azureum (1), Uranoscodon superciliaris (2).

Malagasian iguanids: Chalarodon madagascariensis (2), Oplurus quadrimaculatus (1), Oplurus sebae

(2).

Incerta sedis: Cupriguanus spatulata (1), Enyalioides heterolepis (1), Enyalioides microlepis (1),

Enyalius iheringii (2), Leiosaurus paronae (1),

Morunasaurus annularis (2).

CHARACTERS EXAMINED.—Typically, the variation

within the circulatory system is presented qualitatively. Such a presentation is usually by necessity

rather than by choice. Nonetheless, it makes accurate analysis of variation impossible. Since many

vessels have their origin along the dorsal midline of

the peritoneal cavity, they share a common axis

with the longitudinal body axis. This linear arrangement enabled me to take the succeeding measurements with a high degree of accuracy. All

measurements were taken with Helios dial caliper

to the closest millimeter. It was necessary to pin out

all specimens to ensure that the longitudinal axis

was straight.

Snout to ventricle length (SVR): Distance from the
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

ec

me

sh

FIGURE 1.—The two divergent patterns of carotid arches in iguanids. A, The tropidurine type.

B, The iguanine type. Abbreviations: cc, common carotid; cd, carotid duct; ec, external carotid;

ic, internal carotid; me, musculocervical; sh, sternohyoid.

anterior end of the lower jaw to the posterior tip

of the ventricle.

Snout to vent length (SV): Distance from the anterior end of the lower jaw to the anteromedial

edge of the vent.

Ventricle length (VR): Distance from the origin of

the pulmonary trunk to the posterior tip of the

ventricle.

Snout to axilla length (SA): Distance from the anterior end of the lower jaw to the transverse axillary plane.

Snout to subclavian length (SS): Distance from the

anterior end of the lower jaw to the anterior

edge of right subclavian or common subclavian

at its origin.

Snout to dorsal aorta (SD): Distance from the anterior end of the lower jaw to the dorsal junction

of the right and left systemic arches.

Snout to coeliac length (SC); Snout to inferior

mesenteric length (SIM); Snout to superior

mesenteric length (SSM); Snout to common mesenteric length (SCM) : Distance from the anterior

end of the lower jaw to the anterior edge of the

aforenamed arteries at their origin.

A number of other arterial characteristics were

noted but could not be quantified. The origins of

the external carotid and the sternohyoid may be

separated, contiguous, or from a common trunk.

The relative diameter of the carotid duct is extremely variable and difficult to record. Generally

it is nearly equal to the internal carotid. Two types

of carotid arches are recognizable. In the tropidurine type (Figure 1A), the carotid duct originates

in common with the internal carotid and external

carotid as a trifurcation of the common carotid. In

contrast, the carotid duct and internal carotid of

the iguanine type bifurcate distal to the origin of

the external carotid (Figure 1B). These two types

are the extremes of a continuous range, thus it is

impossible to designate two separate classes. The

subclavians may arise widely separated, contiguous,

or from a common trunk. As the subclavian extends

laterally, it passes beneath a thin ligament or the

muscular bundle of a subvertebral muscle (longus

colli ?). The coeliac is usually present; only in one

species was it absent. The inferior and superior

mesenteric may originate separately, contiguous, or

from a common trunk.

CHARACTER ANALYSIS.—The mensural data were
NUMBER 83

Or—

29 -

33

35 -

36 -

60 -

72

75 -

100*—

\ /

FIGURE 2.—The arterial arrangement and their positions in

the hypothetical lizard. The numerical column provides the

values (in millimeters) assigned to the different measurements. The value assigned to the common mesenteric is 75

mm. Abbreviations: c, coeliac; cc, common carotid; da, dorsal

aorta; ec, external carotid; ic, internal carotid; im, inferior

mesenteric; sa, systemic arch; sc, subclavian; sm, superior

mesenteric; v, ventricle.

analyzed by ratio diagrams (Simpson, 1941). Rather

than plot a ratio diagram for each single specimen,

the data for each genus were combined and a mean

was determined for each measurement. Usually one

of the taxa examined is selected as a standard,

and all other taxa are compared to this standard.

I have constructed, however, a hypothetical lizard

(Figure 2) to be used as a standard. A hypothetical

specimen has several advantages over an actual

specimen: (1) In a hypothetical specimen the

positions of the arteries can be set so that the proportions are evident, i.e., as percentages. (2) Interpretation of the diagram is enhanced, since all

lizards are compared to a single standard of known

proportions. (3) Selection of an actual specimen

implies a certain significance attached to that taxon

and it is difficult to compare the proportions within

this species since all the measurements have been

standardized to zero.

Only the means are plotted in the ratio diagrams.

The sample sizes are too small for the range, standard deviation, or 95-percent confidence interval to

be meaningful. It is to be expected that the amount

of variation reflects the range of body length instead of interspecific differences. Iguana has the

greatest range of body size and would be expected

to have the highest standard deviations.

Observations and Comparisons of the Arterial

System

ANOLINES.—Compared to the hypothetical lizard

(Figure 3) the body proportions of the anolines differ by having the heart more posteriorly, i.e., beyond 33 percent of the body length. The latter is

indicated by SVR greater than SV. The heart lies

at the extreme anterior end of the body cavity and

anterior to the transverse axillary plane. In all

genera, the heart is nearly 4 percent of the body

length, SV sa VR.

The carotid arches of Anisolepis and Phenacosaurus are of the tropidurine type, whereas the

other genera have a more iguanine type of arch.

Anisolepis and Phenacosaurus have the origins of

the sternohyoid and external carotid separate but

contiguous. The two vessels originate by a common

trunk in Chamaeleolis. Anolis (Alpha and Beta

Groups) and Polychrus possess both of the previously mentioned conditions.

The subclavians arise widely separated in all

genera except Anisolepis and one specimen of

Phenacosaurus. The former has a long common
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

SSM

FIGURE 3.—Ratio diagram of arterial characters for anolines. A, Phenacosaurus. B, Anisolepis.

c, Anolis (Beta), D, Anolis (Alpha), E, Polychrus. F, Chamaeleolis. The stars indicate the position

of the hypothetical lizard. An open circle denotes the presence of a common mesenteric. The

abbreviations on the left are explained in the characters examined section.

subclavian trunk, the latter a short one. In Anolis

(Alpha and Beta Groups) and Chamaeleolis, the

subclavians do not pass beneath a muscular bundle

as in the other genera. The origins of the anoline

subclavians and dorsal aorta are clearly separated

and lie beneath the heart in all genera.

The origin of the coeliac is variable. In Anisolepis and Polychrus, it arises anterior to and well

separated from the mesenteries. The remaining

genera has the coeliac arising in close association

with the mesenteries, both anterior and posterior

to them in Phenacosaurus, posterior to them in

Anolis (Alpha and Beta) and Chamaeleolis, and

laterally contiguous in one Anolis (Alpha). The

relative position of its origin is greater than 60

percent of body length in all genera.

In Anolis (Alpha), Chamaeleolis, and Polychrus

the inferior and superior mesenteries arise separately, although only in Chamaeleolis are the two

mesenteries not contiguous at their origin. The

mesenteries arise as a common trunk in Anisolepis,

Anolis (Beta), and Phenacosaurus. In the genera

with two mesenteries, they arise at approximately

72 percent of the body length, i.e., the point of

origin of the inferior mesenteric in the hypothetical

lizard. In the genera with a common mesenteric,

the origin is less than 72 percent of body length.

BASILISCINES.—The body proportions of the basiliscines are very similar (Figure 4). The heart and

the axilla are located posterior to the anterior third

of the body. The entire heart lies anterior to the

transverse axillary plane. The heart is clearly

greater than 4 percent of the body length.

The carotid arches are of the iguanine type. The

external carotid and sternohyoid arise distinctly

separated in all specimens examined.

The subclavians arise paired, one on each side

of the right systemic. The subclavians extend laterally beneath a thin ligamentous muscle attachment. The origin of the dorsal aorta is well removed

from the origin of the subclavians. Both lie dorsal

to the heart.
NUMBER 83

SSM

FIGURE 4.—Ratio diagram of arterial characters for basiliscines and sceloporine allies, A,

Crotaphytus. B, Phrynosoma. c, Corytophanes. D, Gambelia. E, Laemanctus. F, Basiliscus. The

stars indicate the position of the hypothetical lizards. An open circle denotes the presence of a

common mesenteric. The abbreviations on the left are explained in the characters examined

section.

The coeliac is present and anterior of the mesenteries in Basiliscus galeritus, B. plwnifrons, B. vittatus, Corytophanes, and Laemanctus. The coeliac,

however, is small and supplies only the anterior

part of the spleen and the stomach in that region.

The superior mesenteric has a branch which supplies the visceral region usually supplied by the

coeliac. In B. basiliscus, the coeliac is absent, and

the superior mesenteric has completely taken over

the functions of the coeliac.

Both the inferior and superior mesenteries are

present in all basiliscines. The inferior mesenteric

precedes the superior, and both are anterior of the

site of origin in the hypothetical lizard, SIM and

SSM less than SV.

IGUANINES.—Like the anolines and basiliscines,

the heart lies further posterior in the iguanines

than in the hypothetical lizard (Figure 5). The

heart extends posteriorad to the transverse axillary

plane only in Sauromalus. All other genera have

their hearts anterior to the axillary plane. Heart

size is variable. It is larger than the hypothetical

lizard's heart in all genera except Brachylophus in

which it is smaller.

The carotid arches are of the iguanine type. The

origins of the external carotid and sternohyoid are

variable. All three types of origins are present, and

two different ones may occur in an individual, i.e.,

left and right sides.

The subclavians arise paired, one on each side of

the right systemic. In all the genera except Brachylophus and Dipsosaurus, the subclavian passes

laterally beneath a muscle bundle. In the Brachylophus and Dipsosaurus, only a thin flat ligament

covers the subclavian. The origins of the dorsal

aorta and the subclavians are clearly separated. In

Dipsosaurus and Brachylophus, the origins of both

lie dorsal to the heart. Only the subclavians' origins

lie above the heart with the aorta's origin posterior

to the heart in the remaining genera.

The position of the coeliac's origin in relation to

the mesenteries is variable, whereas its relative position in the body is always very similar to that of the

hypothetical lizard. In all genera except Iguana, the
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

04. .08 16 20 24 .28

VR

sv

SA

SVR

SS

SD

SC

SCM

SIM

•

•

•

•

•

•

SSM

FIGURE 5.—Ratio diagram of arterial characters in iguanines. A, Brachylophus. B, Dipsosaurus.

c, Amblyrhynchus. D, Sauromalus. E, Cyclura. F, Ctenosaura. G, Iguana. The stars indicate the

position of the hypothetical lizard. The open circle denotes the presence of a common mesenteric.

The abbreviations on the left are explained in the characters examined section.

coeliac arises anterior to and separate from the

mesenteries. In Iguana, the coeliac may arise posterior to and separated from the mesenteries, contiguous with the superior mesenteric or nearly so,

between the mesenteries, or contiguous with the

inferior mesenteric.

An inferior and a superior mesenteric are present

in all the genera; however, in one Ctenosaura and

one Sauromalus, the mesenteric arises from a common trunk. When paired, the inferior mesenteric

always arises anterior of the superior. The mesenteries always arise more anterior than those of the

hypothetical lizard.

SCELOPORINES.—The heart of sceloporines lies

posterior to that of the hypothetical lizard (Figures

4 and 6). Only in Phrynosoma, does the heart lie

near to the anterior third of the body. The heart in

Crotaphytus, Gambelia, Holbrookia, Uta, Callisaurus, Petrosaurus, and Sceloporus lies anterior to

the transverse axillary plane. In Urosaurus, Uma,

and Phrynosoma, it extends posteriorly beyond the

axillary plane. The size of the heart is nearly

equivalent to that of the hypothetical lizard in

Urosaurus, Uta, Petrosaurus, and Sceloporus, much

smaller in Callisaurus, Uma, Crotaphytus, and

Gambelia, and much larger in Phrynosoma and

Holbrookia.

The carotid arches of the sceloporines are of an

intermediate type. The arches of Sceloporus approach closest to the iguanine type, whereas those

of Callisaurus are more tropidurine in appearance.

The origins of the sternohyoid and external carotid display the three possible patterns. Although the

pattern of origin tends to be symmetrical, some

individuals display different patterns on the left

and right sides.

The subclavians arise paired in all genera except

Phrynosoma. Phrynosoma has a short, but distinct,

common subclavian trunk. A muscle bundle covers

the initial lateral extension of the subclavian in all

genera. The origins of the subclavians and dorsal

aorta are usually separated, although in a few specimens they were nearly contiguous. These origins

lie above the heart in all genera.

The coeliac is the first major visceral artery to

originate. Its origin is well anterior to the mesen-
NUMBER 83

VR

SV

SA

SVR

SS

SD

SC

SCM

SIM

SSM

-.32 -.28 -2 4 -.20 -M -J2 - 0 8 -.04 J04 JO8 J2 .16 .20

FIGURE 6.—Ratio diagram of arterial characters in sceloporines. A, Via. B, Urosaurus. c, Callisaurus. D, Holbrookia. E, Uma. F, Petrosaurus. c, Sceloporus. The stars indicate the position of the

hypothetical lizard. The abbreviations on the left are explained in the characters examined

section.

terics* origins. Excluding Phrynosoma and Holbrookia, the origin is posterior to that in the

hypothetical lizard. In Holbrookia, the origin is

nearly identical to that of the hypothetical lizard;

whereas the origin in Phrynosoma is anterior.

Crotaphytus, Gambelia, Callisaurus, and Phrynosoma have a common mesenteric. Holbrookia,

Petrosaurus, Sceloporus, Uma, Urosaurus, and Uta

have an inferior and a superior mesenteric. In Uta,

Urosaurus, and Holbrookia, the mesenteries are

contiguous. The inferior mesenteric of Petrosaurus

and Uma is anterior to the superior mesenteric and

is separated from it by a short interval. Sceloporus

possesses both of the above conditions. Holbrookia,

Uma, Gambelia, and Phrynosoma are the only taxa

which have the mesenteries' origins lying well anterior to that in the hypothetical lizard. The other

genera have origins slightly anterior to that of the

hypothetical lizard.

TROPIDURINES.—As in all preceding iguanids, the

heart of tropidurines lies further posterior than

does that of the hypothetical lizard (Figure 7). The

posterior tip of the heart reaches the transverse

axillary plane in Ctenoblepharis, Plica, and Uracentron. The other genera have the heart completely anterior to the axillary plane. The hearts of

all tropidurines are proportionately bigger than

that of the hypothetical lizard.

All genera possess carotid arches of the tropidurine type, but of various degrees of development.

The arches are definite tropidurine in Ctenoblepharis and Tropidurus, less so in the other

genera. All three types of sternohyoid-external

carotid origins are present. The type of origin is

usually symmetrical within the individual, but there

is considerable intrageneric variation.

The subclavians arise from a common trunk in

Ctenoblepharis, Ophryoessoid.es, Plica, Stenocercus,

and Uracentron. In Leiocephalus and Liolaemus,

their origins are either contiguous or joined and

only contiguous in Tropidurus. The subclavians of

all tropidurines pass laterally beneath a thick muscle bundle. The origins of the subclavians and

dorsal aorta are usually separate, although in Stenocercus they are contigous, and separated by a small

interval in some of the other tropidurines. They lie
10

- 2 0 -16 -.12 -.08 -.04

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

04 08 .12 .16 -20 .24^ 8

SSM // ii /

FIGURE 7.—Ratio diagram of arterial characters for tropidurines. A, Ctenoblepharis. B, Ophryoessoides. c, Uracentron. D, Leiocephatus. E, Uranoscodon. F, Tropidurus. c, Liolaeinus. H, Plica.

The stars indicate the position of the hypothetical lizard. The abbreviations on the left are

explained in the characters examined section.

dorsal to the heart and not posterior to it.

The coeliac arises anterior of the mesenteries and

distinctly separated from them. Ctenoblepharis,

Leiocephalus, Liolaemus, Plica, and Tropidurus

have their coeliacs originate from approximately

the same body position as that of the hypothetical

lizard. In Uracentron, Stenocercus, and Ophryoessoides, the origin lies more posteriorly and slightly

anterior in Uranoscodon. All the tropidurines, except Plica umbra, Ophryoessoides, and Stenocercus

have the inferior mesenteric arise separately and

anterior to the superior mesenteric. In Stenocercus,

Uranoscodon, and one specimen of Ophryoessoides,

the mesenteries are contiguous. A common mesenteric is present in the other specimen of Ophryoessoides and P. umbra. The relative position of the

mesenteries' origin is similar to that of the hypothetical lizard in Plica, Tropidurus, Ophryoessoides,

and Uracentron. The origins are more anterior in

Ctenoblepharis, Liolaemus, and Leiocephalus, and

more posterior in Stenocercus.

MALAGASIAN IGUANIDS.—The ratio diagram (Figure 8) shows the two Malagasian iguanid genera to

be very similar. The heart lies further posterior

than in the hypothetical lizard. The posterior tip

of the heart reaches the transverse axillary plane in

Chalarodon and nearly so in Oplurus. The heart is

proportionately larger in Chalarodon and proportionately smaller in Oplurus than that of the

hypothetical lizard.

The carotid arches are of the iguanine type. The

sternohyoid and external carotid arise contiguously.

In Oplurus, there is a common subclavian trunk.

The subclavians are paired but nearly contiguous

in Chalarodon. The origins of the subclavians and

the dorsal aorta's origin lie dorsal of the heart in

Chalarodon. The dorsal aorta's origin of Oplurus

lies posterior to the heart.

The coeliac arises anterior to the mesenteries in

both genera. Its origin is posterior to that in the

hypothetical lizard. The mesenteries arise separately.

The inferior mesenteric appears first. In Chalarodon, they originate anterior to the position in the
NUMBER 83 11

- 20 -.12 -.08 -.04 .04 •08 .12 .20 .24 .28

ABC

VR

SV

SA

SVR

SS

SD

SC

SCM

SIM

SSM

•-V^D" if 1 mi. i

FIGURE 8.—Ratio diagram of arterial characters of iguanids of uncertain affinities, A, Chalarodon,

B, Leiosaurus. c, Cupriguanus. D, Enyalioides. E, Enyalius. F, Morunasaurus. c, Oplurus. The stars

indicate the position of the hypothetical lizard. The abbreviations on the left are explained in

the characters examined section.

hypothetical lizard and are nearly the same as the

hypothetical in Oplurus.

IGUANIDS OF UNCERTAIN AFFINITIES.—All of these

genera have their hearts farther posterior than in

the hypothetical lizard (Figure 8). The heart is always anterior to the transverse axillary plane. The

heart is proportionately smaller than that of the

hypothetical lizard in Cupriguanus and Leiosaurus

and proportionately larger in Enyalioides, Enyalius,

and Morunasaurus.

The carotid arches are distinctly tropidurine in

Cupriguanus. The arches of the other genera appear

iguanine in form. The origins of the sternohyoid

and external carotid are from a common trunk in

Enyalioides, Enyalius, Leiosaurus, and Morunasaurus. Enyalius and Morunasaurus have a very

short common trunk. In Cupriguanus, the origins

are contiguous or nearly so.

The subclavians arise separately and paired in

Cupriguanus. A common subclavian trunk is present in the other genera. One of the Enyalius had

a paired but contiguous origin of the subclavians.

The origins of the subclavians and dorsal aorta are

separate. The origin of dorsal aorta lies posterior

to the heart in only Enyalius, Cupriguanus, and

Leiosaurus.

The coeliac originates well anterior to the mesenteries in Cupriguanus, Enyalius, and Leiosaurus.

In Enyalioides heterolepis, the coeliac arises first

but is contiguous with the mesenteries. In Enyalioides microlepis, the coeliac arises posterior to and

separated from the mesenteries. The coeliac of

Morunasaurus is posterior to and contiguous with

the superior mesenteric. The relative body position

is similar to that of the hypothetical lizard in

Enyalius, and posterior in the remaining genera.

The mesenteries are paired and clearly separated

in one Enyalius, Enyalioides, and Morunasaurus.

They are paired and contiguous in Cupriguanus

and Leiosaurus. In the other Enyalius, there is a

short common mesenteric trunk. The mesenteries

lie anteriorly relative to their position in the hypothetical lizard in all except Morunasaurus and the

Enyalius with a common mesenteric. Morunasaurus
12 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

has the origin nearly identical to that of the hypothetical lizard, whereas it is more posterior in the

Enyalius.

COMMENTS.—The primary carotid (carodis primaria) is absent in all iguanids. This condition is

common to most lizards with the exception of varanids and possibly anguids and scincids. Rathke

(1857), Thapar (1923), and Meinertz (1952) report its presence in varanids. A short one is

reported in Anguis by Rathke. Likewise the illustrations of Kashyap and Nigwekar (1964) show a

short but distinct primary carotid in Riopa, a scincid. A short one is reported in Hemidactylus, a

gekkonid, by Bhatia and Dayal (1933), although

their illustration suggests that the carotids arise

paired. It is absent in amphisbaenids (Rathke,

1857), Chamaeleo (Mackay, 1886), Heloderma

(Beddard, 1906), Uromastix (Bhatia, 1929), and

Calotes (de Silva, 1956a and b). I did not observe a

primary carotid in Dicrodon or Tupinambis, teiids.

Carotid ducts were observed in all iguanids. Poor

preservation and different degrees of development,

however, occasionally made them difficult to locate.

The level of my observations prevents any decision

on whether the ducts were functional vessels in all

iguanids. Adams (1953) states that the ducts are

absent in amphisbaenids, chamaeleonids, helodermatids, and varanids.

Intraspecific variation was most prevalent in the

origins of the sternohyoid and external carotid and

the origin of the coeliac relative to the mesenteries.

Occasionally the type of subclavian origin would

display intraspecific variation. As a whole, however,

the pattern of vessel origin is relatively stable

within a genus and commonly within groups of

related genera.

The functional significance of this stability and

its selective value is difficult to explain. Embryologically, the large blood vessels appear before circulation begins and will continue development even

if circulation is impeded (Copenhaver, 1955). Yet

there is also evidence that vessel formation is

strongly influenced by the growth and metabolism

of adjacent tissues. These factors suggest that perhaps the vessel pattern is established by the pattern

of the other body organs, although growth is inherent within the circulatory system and free from

mechanical influence. Iberall (1967) provides two

facts which further suggest that one pattern is mechanically no more efficient than another: (1) The

cross-sectional area of the cardiovascular system

does not change significantly from the aorta to the

major arteries. (2) High blood pressure does not

fall until the terminal levels of the arterial tree, i.e.,

below 100 fi diameter. Thus different arterial patterns do not indicate that one pattern is any more

efficient than another one.

Analysis of the Arterial Characters

Several sets of interrelated questions should be

asked of each new character before it is incorporated

into general taxonomic usage. (1) What is the character's range of variation? Is the range of variation

continuous or discontinuous? At what level, i.e.,

intraspecific, interspecific, etc., does the variation

occur? Can the variation be traced to specific

causes, e.g., ontogenetic, environmental, genetic?

(2) Does the new character or particularly the set

of new characters provide evidence of genetic relationships among the compared taxa? If new relationships are indicated, how valid is the new

interpretation? (3) How is the character related to

other characters? Is the character a primary or secondary character (sensu Kendrick, 1965)? How

many states does the character possess? Can the polarity, i.e., primitive to derived, of the character

states be determined? Are the character states

uniquely derived (sensu Wilson, 1965 or Le Quesne,

1969)? In the following sections, I will attempt to

answer for the arterial characters some of the questions proposed in sets one and two.

CHARACTER VARIATION.—Of the characters described in the anatomical section, only ten are considered sufficiently distinct and nonredundant for

further analysis (Table 1). The presence of the

carotid ducts or the absence of the primary carotid

trunk are useless characters in iguanids, for they are

invariable. Other characters, e.g., origin of sternohyoid and external carotid, type of carotid arch, or

size of carotid duct, either show considerable intraspecific variation or are difficult to record accurately.

Seven distance measurements (SA, SVR, SS, SD,

SC, SSM, SIM) display intergeneric variation and

can, thus, be analyzed to determine their value as

indicators of intergroup relationships. Although the

sample size for each genus is too small for statistical

analysis of variation, the consistently narrow range

of variation within each genus suggests that the
NUMBER 83 13

TABLE 1.—The arterial characters of the iguanids used to generate the shortest

connection networks. Columns A through G are proportions. A, SA/SV. B,

SVR/SV. C, SS/SV. D, SD/SV. E, SIM/SV. F, SSM/SV. G, SC/SV. H, Muscle

covering subclavians: 0, absent; 1, ligamentous; 2, muscular. I, Type of subclavian origin: 0, separate; 1, contiguous; 2, common trunk. J, Type of mesenteric origin: 0, separate; 1, contiguous; 2, common trunk.

TAXON

ANISOLEPIS

PHENACOSAURUS

ANOLIS (B.t« )

POLYCHRUS

ANOLIS (Alpha)

CHAMAELEOLIS

CORYTOPHANES

LAEMANCTUS

BASILISCUS

DIPSOSAURUS

BRACHYLOPHUS

SAUROMALUS

AMBLYRHYNCHUS

CTENOSAURA

CYCLURA

IGUANA

UROSAURUS

UTA

CALL ISAURUS

HOLBROOKIA

UNA

A

•36

• «5

.46

• 39

• 51

•49

.51

. 4 4

.50

.38

. 4 4

• 39

. 4 1

. 4 4

. 4 1

.19

. 4 1

.46

. 4 1

. 4 0

. 4 0

B

• 39

. 4 4

• «3

.38

. 4 8

•49

• 4 7

•43

.47

• 37

. 4 0

.46

.39

. 4 1

• 39

•37

. 4 2

•45

. 4 1

. 4 0

. 4 1

c

• 33

. 4 1

. 4 1

• 33

.46

.45

•47

• 39

. 4 2

.32

.34

.38

•33

•37

•36

•35

•35

.38

.36

.36

•36

D

•35

• 43

. 4 2

•35

. 4 4

• 47

. 4 4

. 4 1

•43

• 3«

•38

. 4 8

•39

. 4 2

. 4 4

. 4 4

.36

. 4 1

• 38

.36

.39

E

• 71

.67

• 67

.70

• 74

• 74

.66

.68

• 70

.66

.67

.66

. 6 4

• 71

.66

• 59

• 73

• 73

• 71

• 69

.68

F

• 71

.67

• 67

.70

.74

• 75

. 6 8

•71

•71

.68

.69

.66

.65

.72

.68

.62

• 73

• 75

• 71

• 69

.69

0

. 6 4

• 67

.66

.67

• 75

• 76

.62

• 63

.62

.62

•59

.64

.62

.64

• <3

.61

.64

.67

. 6 4

. 6 2

•63

H

2

2

0

2

0

0

1

1

1

1

1

2

2

2

2

2

2

2

2

2

2

1

2

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

J

2

2

2

1

1

0

0

0

0

0

0

0

0

0

0

0

1

0

2

1

0

TAXON

PETROSAURUS

SCELOPORUS

PHRYNOSOMA

CROTAPHYTUS

CAHBELIA

URANOSCOOON

CTENOBLEPHARIS

URACENTRON

L I OLAEMUS

0PHRY0ES80I0ES

TROPIDURUS

STENOCERCUS

LEIOCEPHALUS

PLICA

CHALAROOON

OPLURUS

LEIOSAURUS

CUPRIGUANUS

ENYALIOIDES

ENYAL1 US

MORUNASAURUS

A

. 4 6

• 45

•35

. 4 8

. 4 2

. 4 6

. 4 2

.45

. 4 0

• 45

.46

. 4 8

. 4 8

• 45

.46

.47

• «3

. 4 8

. 4 8

• *9

• 51

B

. 4 4

.43

•39

.45

. 4 1

. 4 2

. 4 2

.45

.38

. 4 2

. 4 2

•47

. 4 4

. 4 4

.46

•45

•39

.47

. 4 4

• «5

. 4 8

C

•38

.36

.32

. 4 1

.38

•38

•35

• 39

• 34

•39

•37

. 4 0

. 4 0

•39

•39

. 4 1

• 38

. 4 1

. 4 0

.45

.45

0

•38

.39

• 37

.43

. 4 2

. 4 1

• 37

. 4 1

• 35

. 4 1

. 4 0

. 4 0

-43

. 4 1

. 4 2

. 4 6

. 4 2

. 4 4

. 4 1

• 47

•47

E

•73

•74

.66

• 72

.68

.67

.66

• 73

.66

• 74

• 71

• 78

.66

.69

.68

• 71

• 67

• 73

• 65

• 72

.74

F

•74

•74

.66

•72

.68

.67

.68

.74

.68

.74

•73

.78

• 67

.70

• 69

• 74

• 67

• 73

• 65

• 73

• 75

a

.65

. 6 4

.56

.68

.62

• 57

.60

.66

.60

.66

.61

. 6 8

. 6 2

. 6 0

•63

.67

.61

.68

.65

.67

• 7S

H

2

2

2

2

2

1

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

1

0

0

2

0

0

0

2

2

1

2

1

2

0

2

0

2

2

0

2

2

2

J

0

0

2

2

2

1

0

0

0

1

0

1

0

1

0

0

1

1

0

1

0

intraspecific and interspecific variation is small. In

addition, the distance measurements were converted

to proportions to eliminate the influence of body

size, thereby also slightly reducing ontogenetic variation. The proportions were obtained by dividing

each distance measurement of a specimen by the

specimen's snout-vent length. The proportions of

each character were summed and the arithmetic

mean recorded for each genus. Since some genera

lack separate mesenteric arteries, the mean proportion of the common mesenteric was used for both

the inferior and superior mesenteric.

Each of the three remaining characters possess

three states, which are designated by 0, 1, and 2,

respectively. The states for the subclavian enclosed

by a muscle are muscle absent, small and/or ligamentous, and large. The states for the type of subclavian origin and mesenteric origin are paired and

separate, paired but contiguous, and a single trunk.

Although the latter two character states were discrete and easily recognizable, there was occasional

intrageneric variation. Variation of the subclavian

occurred in Crotaphytus, Enyalius, Leiocephalus,

Liolaemus, and Stenocercus, of the mesenteric in

Anolis, Ophryoessoides, Sauromalus, Sceloporus,

and Uta. The most prevalent state in the taxa was

recorded.

The proportions, SSM/SV, and SIM/SV, and the

type of mesenteric origin are not redundant characters. The type of origin does not influence the

relative body position of the origin. The type of

origin, however, does affect the position of the

mesenteries in relation to one another. Since the

proportions indicate relative body position, the occasional fusion of the two mesenteries has a minor

effect. Of the ten characters, the SA/SV and the
14 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

muscle enclosing the subclavian do not reflect

arterial patterns. Nonetheless they are incorporated, since they have not previously been analyzed

for taxonomic purposes.

IGUANID RELATIONSHIPS.—The incorporation of

new characters into an extant taxonomic framework

must be done judiciously. Otherwise, the new characters may be disruptive without adding any

alternative or new interpretations of intergroup relationships. The following steps are utilized herein

to test the significance and validity of the arterial

characters.

(1) Select the taxonomic level, e.g., intrafamilial,

intrageneric, at which the classification information

of the new character set is to be compared. Assemble as completely as possible the extant character

set which is currently used to define the stated

taxonomic level.

(2) Select an objective and repeatable procedure

for generating relationship diagrams, i.e.,

phenograms, cladograms, etc.

(3) Generate a relationship diagram for each of

the character sets and compare the two diagrams.

If the two diagrams are strongly divergent, return

to step 1.

The preceding steps are based on several assumptions. A primary assumption is that the relationship diagram generated by the extant character

set will conform closely to the current interpretation of intergroup relationships. If this assumption

is not obtained, a valid comparison of the two character sets cannot be made. The current interpretation may be in error, the extant character set may

be too small or lack the diagnostic characters, or

the analysis procedure may be inadequate. Comparison of the two sets assumes that the general

pattern of intergroup relations is fairly well understood. It is necessary, however, to avoid circular

reasoning. Since the goal of obtaining new characters is to increase the accuracy of our current

interpretation, a new character set should not be

discarded simply because its diagram does not match

that of the extant character set. The degree of discordance must be weighed. Strong discordances imply that the new character set or at least part of it

is not usable at the chosen taxonomic level. There

is also the possibility, however, that the extant character set and its implied relationships are in error.

The zoogeographic implications of the relationship

diagram provide valuable criteria for evaluation.

Suggestions of unusual or irregular zoogeographical

patterns suggest an invalid set of characters. If clusters of taxa in a relationship diagram have a strong

correlation with ecological or behavioral groups,

body form or shape, etc., the relationships are probably not phylogenetic. The character set may be

reflecting a single adaptation system, and the

likelihood of convergence is great.

To test the arterial data, I have used a shortest

connection network computer program developed

by James S. Farris while at the University of Michigan. The program was used on the United States

National Museum of Natural History time-share

computing facilities. The network is entirely phenetic. Each taxon is linked to its most similar taxon,

and in turn linked segments or clusters are linked

together through the most similar member of each

cluster. None of the characters were weighted, nor

were they transformed. The character set (Table 2)

for the extant classification was extracted mainly

from articles of Etheridge.

The network (Figure 9), based on the extant

character set, clusters the genera similarly to the

groups proposed by Etheridge (1967:717). Actually

there is only one disagreement. The Crotaphytus

complex is clustered with the iguanines. This

linkage appears to result from the presence of zygosphenes and zygantra, variable presence of pterygoid teeth, presence of a secondary coracoid fenestra,

and number of sternal rib and presacral vertebrae.

Savage (1958) was the first to formally group

Crotaphytus with the iguanines. Etheridge (1964)

placed Crotaphytus in the sceloporine-tropidurine

lineage and showed it to be more similar to Petrosaurus than to any other Nearctic and Central

American iguanid. The difference between the

phenogram and Etheridge's interpretation is largely

due to Etheridge weighting characters and evaluating a larger character set. Etheridge showed that

zygosphenes and zygantra probably appeared independently in several iguanid lineages. Perhaps such

an occurrence is also true for the secondary coracoid

fenestra. The presence of pterygoid teeth may reflect nothing more than the retention of a primitive

character state. Thus, Etheridge's allocation of

Crotaphytus to the sceloporine-tropidurine lineage

should be accepted.

Although the arrangement of genera within clusters should be noted, the limitations of the data set

and the manner of constructing the network medi-
TABLE 2.—Some of the characters currently used to classify iguanids. This set of characters was derived

from the investigations of Etheridge (1959, 1964, 1965, 1966, 1967) and Savage (1958). A, Femoral pores:

absent, 0; present, 1. B, Caudal vertebra fracture plane: absent, 0; absent or present, 0.5; present, 1. C,

Transverse process of caudal vertebra: absent, 0; single, 1; double, 2. D, Inscription ribs: all joined to

dorsal ribs, 0; one or more floating, 1. E, Inscription ribs: opposites not fused on ventral midline, 0; one

or more fused, 1. F, Scapular fenestra: absent, 0; present, 1. G, Secondary coracoid fenestra: absent, 0;

absent or present, 0.5; present, 1. H, Sternal fontanelle: absent, 0; absent or present, 0.5; present, 1. I,

Clavicular fenestra: absent, 0; absent or present, 0.5; present, 1. J, Number of sternal ribs. K, Number

of xiphisternal ribs. L, Number of presacral vertebrae minus 20. M, Number of cervical ribs. N,

Zygosphenes-zygantra: absent, 0; present, 1. O, Pterygoid teeth: absent, 0; absent or present, 0.5; present, 1.

P, Palatine teeth: absentft; present, 1. Q, Meckel's groove: open, 0; closed, 1; fused, 2. R, Calcified endolymphatic glands: absent, 0; present, 1. The underlined values are questionable and should be confirmed.

TAXON

ANISOLEPIS

PHENACOSAURUS

ANOLIS (Alphi )

ANGUS (BtU )

POLYCHRUS

CHAMAELEOLIS

CORYTOPHANES

LAEMANCTUS

BASILISCUS

DIPSOSAURUS

BRACHYLOPHUS

SAUROMALUS

AN8LYRHYNCHUS

CTENOSAURA

CYCLURA

IGUANA

UROSAURUS

UTA

CALLISAURUS

HOI BROOK 1A

UNA

PETROSAURUS

SCaOPORUS

PHRYNOSOMA

CROTAPHYTUS

GAM BELIA

URANOSCODON

CTENOBLEPHARIS

URACENTRON

LI OLA EMUS

OPHRYOESSOIDES

TROPIOURUS

STENOCERCUS

LEIOCEPHALUS

PLICA

CHALAROOON

OPLURUS

LEIOSAURUS

ENYALIOIDES

ENYALIUS

HORUNASAUP.US

A

0

0

0

0

1

0

0

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

1

0

1

B

0

0

0.5

1

0

0

1

1

0

1

0

1

1

0.5

1

1

1

1

1

1

1

0

0

1

1

0

1

0.5

1

1

1

1

1

1

0.5

0.5

0

1

c

1

0

0

1

0

0

0

2

2

2

2

2

2

2

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

0

0

0

0

1

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

1

1

1

1

I

E

1

1

1

1

1

1

0

0

1

0

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

1

1

0

F

0

0

0

0

0

0

1

1

1

1

1

1

1

1

0

0

1

1

1

0

1

1

1

1

0

1

0

1

1

0

1

1

1

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16

CHAMAELEOLIS

POLYCHRUS

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

ANOLIS (Alpha) — ANOLIS (Beta) — — ANISOLEPIS

PHENACOSAURUS

LE1OSAURUS

ENYALIOIDES ENYALIUS

CHALARODON

OPLURUS

CALLISAURUS HOLBROOKIA

PHRYNOSOMA

UMA

SCELOPORUS

UTA

UROSAURUS

MORUNASAURUS

PETOOSAURUS

LAEMANCTUS

CORYTOPHANES

LEIOCEPHALUS — LIOLAEMUS - STENOCERCUS

I CTENOBLEPHARIS

OPHRYOESSOIDES ^ ^ URANOSCODON

I ^^ ^ URACENTRON

TROPIDURUS

BASILISCUS PLICA

AMBLYRHYNCHUS

SAUROMALUS

DIPSOSAURUS

BRACHYLOPHUS

IGUANA

CROTAPHYTUS GAMBELIA

FIGURE 9.—A shortest connection network for iguanids based on the characters in Table 2. The

bar equals one unit of difference. The mean difference for this network is 2.5.

ate against any "absolute" statement of phylogenetic

relationships. In other words, I do not propose that

the Malagasian iguanid are derived from sceloporine stock or that Brachylophus is derived from

an ancestral Amblyrhynchus. The relative position

and distribution of the clusters may provide clues

to the relationships of certain genera. Etheridge's

iguanids of uncertain affinities lie between the anoline and the tropidurine, so a search for their affinities should be with those groups. Also these incerta

sedis iguanids form a loose cluster. Perhaps this is a

natural assemblage. Likewise, what is the signifi-
OPHRYOESSOIDES.

/ I \ STENOCERCUS PLICA ENYALIUS

ANOLIS (Alpha) |

LEIOSAURUS

ANOLIS (Beta)

 CHAMAELE0LI S PHRYNOSOMA

URANOSCODON

BRACHYLOPHUS

ANISOLEPIS

URACENTRON — OPLURUS MORUNASA'JRUS

ENYALIOIDES

CTENOBLEPHARIS

LIOLAEMUS

TROPIDURUS

CORYTOPHANES

RASILISCUS

DIPSOSAURUS ——LAEMANCTU S

UTA

\

PETROSAURUS

SAUROMALUS \

LEIOCEPHALUS I SCELOPORUS

S I \

• CHALARODON — CTENOSAURA

IGUANA

PHENACOSAURUS

CYCLURA

AMBLYRHYNCHUS

POLYC

UMA 

FIGURE 10.—A shortest connection network for iguanids based on the arterial characters in Table 1. The bar equals on

unit of difference. The mean difference for this network is 2.7.
18 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

LEIOCEPHALUS

LIOLAEMUS

URANOSCODON PLICA PROCTOTRETUS TROPIDURUS

PLATYNOTUS

URACENTRON

STENOCERCUS

OPHRYOESSOIDES —

FIGURE 11.—A shortest connection network for tropidurines based on the characters in Table 3.

The bar equals one unit of difference. The mean difference for this network is 3.3.

LEIOCEPHALUS• URANOSCODON

PLICA

STENOCERCUS• OPHRYOESSOIDES

OJ.

TROPIDURUS

LIOLAEMUS •CTENOBLEPHARIS URACENTRON

FIGURE 12.—A shortest connection network for tropidurines based on the arterial characters in

Table 1. The bar equals one tenth of a unit of difference. The mean difference for this network

is 0.8.

cance of Plica forming a pivoting point for the

basiliscines, iguanines, and tropidurines?

Comparison of the former network (Figure 9)

with the arterial network (Figure 10) shows a high

degree of discordance. Of the clusters delimited by

a linkage of less than the mean of the coefficient of

similarity, only three of the clusters in the arterial

network contain a natural assemblage of genera,

i.e., based on Etheridge's groups. Three clusters are

composed of members of two groups, and two dus-
NUMBER 83 19

TABLE 3.—A series of characters for tropidurines taken from Etheridge (1966).

A, Tricuspid teeth: sharp cutting edge, 0; blunt edge, 1. B, Pterygoid teeth:

absent, 0; absent or present, 0.5; present, 1. C, Lower jaw: coronoid over dentary,

0; coronoid not over dentary, 1. D, Premaxillary-nasal overlap: nasal process of

premaxillary covered dorsally, 0; not covered dorsally, 1. E, Parietal: lateral

borders narrowly separated, 0; borders widely separated, 1. F, Inter clavicle:

lateral process widely separated from clavicle, 0; process contacts clavicle, 1. G,

Xiphisternon: xiphisternal rods extend posterior, 0; variable, 0.5; rods do not

extend posterior, 1. H, Parasternal ribs: absent, 0; one pair, 1; two pairs, 2;

three or more pairs, 3. I, Caudal vertebrae: spine above fracture plane, 0; above

entire arch, 1. J, Nasal-rostral contact: broad contact, 0; variable, 0.5; separated

or slight contact, 1. K, Dorsal head scales: smooth, 0; smooth and rugose, 0.5;

rugose, 1. L, Enlarged anterior auricular scales: absent, 0; absent and present,

0.5; present, 1. M, Middorsal crest: absent, 0; present, 1. N, Subdigital lamellae:

enlarged to form comb, 0; do not form comb, 1. O, Scale organs: five or less per

dorsal scale, 0; six or more per dorsal scale, 1.

TAXON

LEIOCEPHALUS

0PHRY0ESSOI0ES

LIOLAEMUS

PLICA

PROCTOTRETUS

STENOCERCUS

TROPIDURUS

URANOSCOOON

URACENTRON

A

0

1

0

0

1

1

1

1

0

B

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0.5

l

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c

0

1

0

1

1

1

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D

0

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0

1

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1

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E

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1

1

1

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1

1

1

1

F

0

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0.5

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0

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0

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M

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1

0

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0

0

0

0

0

0

0

0

POLYCHRUS —— PHENACOSAURUS — — ANISOLEPIS

ANOLIS (Beta)

ANOLIS (Alpha)

CHAMAELEOLIS

FIGURE 13.—A shortest connection network for anolines

based on the aiterial characters in Table 1. The bar equals

one unit of difference. The mean difference for this network

is 1.7.

ters possess members of three groups. The two

Malagasian genera are widely separated. Certain

linkage patterns, such as the closeness of Phrynosoma and Anisolepis or the dichotomy of the two

Anolis groups, cast additional doubt on the validity

of using the arterial character set at this taxonomic

level. A network generated by using only the proportions (first seven characters in Table 1) produces an even more discordant network. The

following linkages were, however, retained: Cupriguanus to Crotaphytus, Uracentron to Ophryoessoides, Sceloporus to Petrosaurus, Iguana to

Amblyrhynchus, Holbrookia to Uma, Liolaemus to

Ctenoblepharis, Corytophanes to Basiliscus, Ctenosaurus to Tropidurus, Laemanctus to Chalarodon

to Sauromalus.

Although the two networks (Figures 9 and 10)

are dissimilar, certain linkage patterns occur in

both. The basiliscines are linked, as are also Anolis

(Alpha and Beta) and Chamaeleolis. Ctenoblepharis

and Liolaemus, Ophryoessoides and Leiosaurus,

Tropidurus and Liolaemus, and Petrosaurus and
20

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

IGUANA

CYCLURA AMBLYRHYNCHUS BRACHYLOPHUS — — DIPSOSAURUS

CTENOSAURUS

0.1

SAUROMALUS

FIGURE 14.—A shortest connection network for iguanines based on the arterial characters in

Table 1. The bar equals one unit of difference. The mean difference for this network is 0.4.

UMA HOLBROOKIA"

•UROSAURUS

SCELOPORUS

I

PETROSAURUS

I

UTA

CROTAPHYTUS CALLISAURUS

PHRYNOSOMA- GAMBELIA

FIGURE 15.—A shortest connection network for sceloporines based on the arterial characters in

Table 1. The bar equals one tenth of an unit of difference. The mean difference for this network

is 0.6.

Uta are linked. The occurrence of these linkage patterns in two widely different data sets suggest that

these linkages may be natural.

Comparison of the arterial data at a lower taxonomic level, i.e., within Etheridge's "subfamilies"

(Figures 11 and 12) again shows discordance. Evaluation of the discordance is difficult at this level.

Each network has one or two genera not included

in the other. There is no obvious correlation with

ecology, size, etc. Thus neither network can be rejected or accepted on any logical criteron. Only a

single linkage group, Plica, Stenocercus, and Ophryoessoides, is shared by the two networks. This

linkage suggests that Plica should be removed from

the Strobilurus, Uracentron, Tropidurus, and

Platynotus group (Etheridge, 1968). Uracentron,

Tropidurus, and Platynotus are linked in Figure

11; Strobilurus was not included in the analysis.

Figures 13, 14, and 15 are not compared to phenograms derived from an extant character set. Both

the iguanine and anoline networks are very compact. Their members differ only slightly from one

another. The anoline network does not agree with

Etheridge's 1967 divisions, although Phenacosaurus

and Polychrus are linked. The tropidurine and

sceloporine networks show the same degree of dispersion, i.e., a higher degree of arterial diversity.

Comparison of the sceloporine network with Etheridge's phylogenetic tree (1964: fig. 6) shows few

similarities. The extreme divergence of Phrynosoma

is the only point of close agreement. Although

Gambelia and Crotaphytus are separated in the
NUMBER 83 21

network, I do not believe that this information is of

sufficient merit to be used in the Gambelia

controversy (see Montanucci for additional details).

The arterial characters employed herein appear

to be of minimal value in iguanid classification. At

the intrafamilial level, they are disruptive and form

groups of questionable zoogeographical unity.

Some of their implied relationships bear additional

investigation, but definitely should not be accepted

on the basis of arterial data alone.

Summary

Anatomically, the major arteries of iguanids show a

fairly uniform pattern. A single primary carotid and

a pair of carotid ducts are always present. The subclavians always arise from the right systemic arch

and usually above the heart. With the exception of

Iguana, the coeliac originates anterior to or adjacent to the mesenteries. The inferior and superior

mesenteries are always present, although they may

arise initially from the dorsal aorta in a common

trunk.

Variation was observed in the type of origin of

the sternohyoid and external carotid, the subclavians, and the mesenteries. The two vessels can arise

independently, separately but contiguous, or from

a common trunk. The carotid arch showed two extremes, an iguanine and a tropidurine type, of a

continuous pattern. Within the genus Basiliscus,

the manner of the coeliac loss is displayed by a

morphological series.

The anatomical observations are reduced to ten

characters by discarding those observations with

a large amount of intrageneric variation. Seven of

these are distance measurements which are converted to proportions to eliminate the influence

of body size. Each of the remaining three characters exist in three discrete character states. The

taxonomic information content of the arterial characters is determined by generating a phenogram

from the arterial data. Another phenogram is produced from the extant data on iguanids. When the

two phenograms are compared, they are very dissimilar, and cluster of genera in the arterial phenogram shows little correlation with zoogeographical,

taxonomical, ecological, or behavioral groups. Thus

the arterial characters employed herein may be useful as indicators of relationships but should not

be incorporated in our extant character set for

determining iguanid relationships.

As an indicator the different structure of the

carotid arch in iguanines and tropidurines supports

their separation into two groups. The basiliscines

are clustered in both phenograms, attesting to their

close relationships. Both the anolines and iguanines

form compact groups in the phenograms. Other relationships are implied among the iguanids but

require more data than that provided by the arterial characters.

Acknowledgments

I wish to thank Dr. James A. Peters and Dr. Richard Etheridge for their valuable suggestions and

constructive criticism. Dr. James S. Farris graciously

allowed me to use his shortest connection network

computer program.

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and (2) paragraph sideheads (caps and small caps in print) for subdivisions. Further headings

may be worked out with the editor.

In taxonomic keys, number only the first item of each couplet; if there is only one couplet,

omit the number. For easy reference, number also the taxa and their corresponding headings

throughout the text; do not incorporate page references in the key.

In synonymy, use the short form (taxon, author, date, page) with a full reference at the end

of the paper under "Literature Cited." Begin each taxon at the left margin with subsequent lines

indented about three spaces. Within a taxon, use a period-dash (.—) to separate each reference.

Enclose with square brackets any annotation in or at the end of the taxon. For references within

the text, use the author-date system: "(Jones, 1910)" or "Jones (1910)." If the reference is

expanded, abbreviate the data: "Jones (1910, p. 122, pi. 20: fig. 1)."

Simple tabulations in the text (e.g., columns of data) may carry headings or not, but they

should not contain rules. Formal tables must be submitted as pages separate from the text, and

each table, no matter how large, should be pasted up as a single sheet of copy.

For measurements and weights, use the metric system instead of (or in addition to) the

English system.

Illustrations (line drawings, maps, photographs, shaded drawings) can be intermixed

throughout the printed text. They will be termed Figures and should be numbered consecutively;

however, if a group of figures is treated as a single figure, the individual components should be

indicated by lowercase italic letters on the illustration, in the legend, and in text references:

"Figure 96." If illustrations (usually tone photographs) are printed separately from the text as

full pages on a different stock of paper, they will be termed Plates, and individual components

should be lettered (Plate 9b) but may be numbered (Plate 9: figure 2). Never combine the

numbering system of text illustrations with that of plate illustrations. Submit all legends on pages

separate from the text and not attached to the artwork.

In the bibliography (usually called "Literature Cited"), spell out book, journal, and article

titles, using initial caps with all words except minor terms such as "and, of, the." (For capitalization of titles in foreign languages, follow the national practice of each language.) Underscore

(for italics) book and journal titles. Use the colon-parentheses system for volume, number, and

page citations: "10(2) :5-9." Spell out such words as "figures" and "plates" (or "pages" when

used alone).

For free copies of his own paper, a Smithsonian author should indicate his requirements on

"Form 36" (submitted to the Press with the manuscript). A non-Smithsonian author will receive

50 free copies; order forms for quantities above this amount with instructions for payment will be

supplied when page proof is forwarded.