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 SERIAL PUBLICATIONS OF THE SMITHSONIAN INSTITUTION

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. UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON : 1971 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