Osteology and Myology of the Head and Neck Regions of Callisaurus, Cophosaurus, Holbrookia, and Uma (Reptilia: Iguanidae)

Great Basin Naturalist

Volume 37 Number 1 Article 3

3-31-1977

Osteology and myology of the head and neck regions of Callisaurus, Cophosaurus, Holbrookia, and Uma (Reptilia: Iguanidae)

Douglas C. Cox Brigham Young University

Wilmer W. Tanner Brigham Young University

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Recommended Citation Cox, Douglas C. and Tanner, Wilmer W. (1977) "Osteology and myology of the head and neck regions of Callisaurus, Cophosaurus, Holbrookia, and Uma (Reptilia: Iguanidae)," Great Basin Naturalist: Vol. 37 : No. 1 , Article 3. Available at: https://scholarsarchive.byu.edu/gbn/vol37/iss1/3

This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. OSTEOLOGY AND MYOLOGY OF THE HEAD AND NECK REGIONS OF CALLISAURUS, COPHOSAURUS, HOLBROOKIA, AND UMA (REPTILIA: IGUANIDAE)

Douglas C. Cox' and Wilmer W. Tanner^

Abstract.- A detailed study of the anterior osteology and myology of Callisatmis, Copho.saurus, Holbrookia, and Vma reveals the phylogenetic relationships among the sand lizards. An SPSS discriminant analysis of osteological characters combined with myological characters indicates that Callimiirtis is most primitive, Cop- hosaurus and Holbrookia are most closely related, and Uma is the most distinct of the sand lizard genera. Be- cause of close relationships between Cophosaurus and Holbrookia, it is postulated that earlessness evolved once, and Cophosaurus is returned to synonymy under Holbrookia.

Blainville (1835) wrote the first descrip- (1932) Holbrookia propinqua stonei; Smith tion of a sand lizard and named it Calli- (1935, 1943, 1946:137, 145) Holbrookia ele- saurus draconoides. Since then various au- gans thermophila, Holbrookia elegans ele- thors have pubhshed articles concerning gans, Holbrookia bunkeri, Holbrookia macu- sand lizards. Girard (1851) described Hol- lata ruthveni, Holbrookia maculata brookia maciilata, Trochel (1852) described dickersonae, Holbrookia maculata pulchra, Cophosaurus texanus, and that same year and Holbrookia maculata thermophila; Lins- Baird and Girard synonymized Cophosaurus dale (1940) Callisaurus draconoides myurus with Holbrookia, providing the name Hol- and Callisaurus draconoides gabbii; Heifetz brookia texana, which then remained un- (1941) Uma notata notata; Bogert and Dor- changed for over 100 years. Subsequently, som (1942) Callisaurus draconoides brevipes; Baird (1858) described Uma notata. Smith and Burger (1950) Holbrookia prop- By 1858 all genera represented in the inqua propinqua and Holbrookia propinqua sand lizard group had been described. Since piperata; Peters (1951) Holbrookia texana then new species and subspecies, as well as texana and Holbrookia texana scitula; Axtell new combinations, have been added by var- (1956) Holbrookia lacerata, Holbrookia lacer- ious authors as follows: Bocourt (1874) Hol- ata subcaudalis and Holbrookia maculata brookia elegans- Cope (1880, 1883, 1894, perspicua; Smith and Cochran (1956) Calli- 1895, 1896, 1900) Holbrookia lacerata, Hol- saurus draconoides rhodostictus; and Wil- brookia maculata fkwilenta, Uma scoparia, liams, et al. (1959) Uma paraphygus. Uma inornata, Uma rufopuncatata, Calli- Some summaries, reviews, checklists, and saurus crinitus, Callisaurus rhodostictus, comparative studies have also been written. Holbrookia maculata maculata, Callisaurus Cope (1896) synonymized Uina and Calli- draconoides ventralis, and Callisaurus ven- saurus in a short paper di.scussing the genus tralis gabbii; Stejneger (1890) Holbrookia Callisaurus. He recognized Uma again in maculata approximans and Holbrookia his large work on the crocodilians, lizards, maculata lacerata; Richardson (1915) Calli- and snakes of North America (1900) and saurus ventralis myurus; Dikerson (1919) recognized one species and three subspecies Callisaurus carmenensis; Schmidt (1921, of Callisaurus. 1922) Holbrookia maculata campi, Hol- brookia pulchra, Holbrookia dickersonae, and Smith (1946:137, 145), in his "Handbook Callisaurus ventralis inusitatus; Schmidt of Lizards," recognized in Callisaurus one and Bogert (1947) Uma exsul; Barbour species and ten subspecies and stated (p. (1921) Holbrookia thermophila; Harper 145): 'The whole group of Callisaurus of

'Department of Zoology, Brigham Young University, Provo, Utah 84602. 'Life Science Museum, Brigham Young University, Provo, Utah 84602.

35 36 Great Basin Naturalist Vol. 37, No. 1

western United States is in need of revision. U. n. rufopunctata, U. n. inornata, U. sco- The subspecies are not adequately charac- paria, and U. exsul. He discussed the evolu- terized, nor are their ranges well worked tion of Uma and its relationship to other

out. There is very little information on the sand lizards.

life history." Although we now know much The conflict relative to the classification more about the life history of CaUisaurus, it of the notata-scoparia group was discussed is still in need of a comprehensive tax- by Mayhew (1964b). He recognized U. in- onomic review and remains a monotypic ornata, U. notata, and U. scoparia all as full genus. (A careful revision for CaUisaurus species on the basis of temperature toler- has not yet been attempted.) ance and reproductive data. The genus Holbrookia has had two revi- Peters (1951) reviewed Holbrookia texana sions. Schmidt (1922) made the first; a sec- {Cophosaurus texanus). He described two sub- ond was by Axtell (1958). Schmidt (p. 709) species, but mentions little concerning rela- stated: "The taxonomy of the North Ameri- tionships with other sand lizards. can lizards of the genus Holbrookia Girard Clarke (1965) revived Cophosaurus texan- offers one of the most interesting and diffi- us on the basis of behavioral data collected cult problems in North American herpeto- in a large comparative study of the sand logy." fizard group. He recognized several species and states Ecological and behavioral studies con- that (p. 712) ^'Holbrookia is obviously di- cerning sand lizards have also rectly related to CaUisaurus, from which it been pub- differs only in the concealed tympanum and lished by Burt (1931a, 1931b), Stebbins 1954, with which it agrees in general features of (1944, 1966), Ramsey (1948, 1949), color pattern and scutellation." Cagle (1950), Williams and Smith (1958), Smith (1946:137, 145) doubts that a prac- Axtell (1960), Lannom (1962), Carpenter tical means of characterizing the species ex- (1963, 1967), Clarke (1965), Mayhew (1964a, 1964b, Pianka ists and believes that "until such a means is 1966), and Parker found there will remain indefinitely a prob- (1972), Tanner and Krogh (1975), and Judd lem in defining the ranges of the several (1974, 1975). subspecies, or in defending their actual The anatomy of these lizards has not validity. Accordingly the genus, par- been thoroughly studied. Earle, in a series ticularly the maculata group, merits a care- of articles (1961a, 1961b, 1961c, 1962), de- ful study perhaps more than any other in scribed in detail the comparative anatomy the United States." of the middle ear of sand lizards. Stebbins Axtell (1958) recognized only three spe- (1943, 1944) described the nasal structures cies, HoUjrookia lacerata, H. propinqua, and and some aspects of the ecology of Uma, H. maculata. He considered H. texana to be then (1948) described the nasal structures of a species of the genus CaUisaurus and lizards in general, which included the sand therefore did not discuss it. He did list two lizards. Axtell (1958) described the osteology subspecies for lacerata, two for propinqua, of Holbrookia and stated that it is essentially and 11 for maculata. the same as found in all sand lizards. Eth- Uma has been reviewed by Heifetz ridge (1964) studied the skeletal morphology (1941), Norris (1958), and Mayhew (1964b). of sceloporine lizards, which includes sand Heifetz recognized U. notata notata, U. no- lizards, and compared their relationships. tata cowlesi, U. inornata, and U. scoparia. Savage (1958) studied Urosaurus and Uta He also referred to the taxonomic confusion and made remarks concerning related gen- that exists because of erroneous type local- era, which included sand lizards. A few ref- ities in this genus. In his checklist Schmidt erences to sand lizards were made by Lar- (1953) recognized only one species (notata), sen and Tanner (1974) while studying with three subspecies {notata, inornata, and Sceloporus, and Guttman (1970b) also refers scoparia). to them in his electrophoretic study of the Norris (1958) recognized Uma n. notata. hemoglobins of sand lizards. He found that March 1977 Cox: Lizard Morphology 37 all genera possessed the same major and mi- from San Bernardino Co., California: (BYU) nor protein components. 11389, (CAS) 42072. Only portions of the osteology have been Skeletal material was prepared by careful adequately treated; the myology is essen- dissection. Bones were cleaned with forceps tially untouched. The objectives of this and dissecting needles and soaked in Clorox study are to: (1) describe the skull osteology bleach for several minutes to loosen soft tis- and branchiomeric myology of sand lizards; sues, after which hirther picking and clean- (2) identify osteological and myological ing was done. Skulls were not allowed to characteristics that distinguish the sand liz- dry, but were preserved in 70 percent ard generic groups; and (3) determine more EtOH to insure that cartilaginous skeletal accurately the relationships between these elements could be examined. groups. No attempt will be made to deal The Statistical Package for the Social Sci- with the species and subspecies except as ences (SPSS) discriminant analysis was uti- they relate to the generic phylogeny. lized to aid in the identification of characters where they were not already obvious. Materials and Methods The statistical analysis will be described below. Specimens used were obtained from the Myological examinations consisted of Brigham Young University Life Sciences careful dissection in which each muscle was Museum (BYU), the California Academy of separated and its origin and insertion deter- Sciences (CAS), and the Strecker Museum mined. General morphology (shape, relative at Baylor University. At least four speci- size, and position) of each muscle was also mens from each of the four genera were noted. Muscle comparisons are based on used for osteological examinations. The both origin-insertion and muscle morpho- myology of these 16 specimens, plus four logy. Only the branchiomeric muscles asso- additional individuals from each genus, ciated with the hyoid arch and the jaws are were also used in developing the myological described. description. The following list indicates the material used: Callisaums draconoides gabhi Osteology from N.T.S., Nye Co., Nevada: (BYU) 2943, 2967, 3079, 40037; C. d. inusatatus from Sand lizard skulls have been examined in Tiburon Island, Sonora, Mexico: (BYU) detail. The length and width of individual 30175, 30176, 30178; C. d. splendidus from elements were measured with a Golgau ver- Isla Angel de la Guardia, Gulf of California, nier caliper and a five-millimeter mini-tool. Mexico: (BYU) 41112; C. d. carmenesis from Comparisons were made on the basis of ra- Baja California Sur, Mexico: (BYU) 41095, tios, as well as on the shape and position of 41231; Cophosaunis texanus texanus from each bone in relation to other articulating Chihuahua, Mexico: (BYU) 14339, 15712; C. bones. The lower jaw and hyoid have been t. scitula from Sierra Co., New Mexico: studied in the same manner.

(BYU) 30512, 30513, 30515; C. t. scitula The skull is streptostylic, with a freely from Pima Co., Arizona: (BYU) 34331, movable quadrate bone. In mature individ- 34336; Holbrookia lacerata from Giaraz Co., uals the ethmoid region of the braincase

Texas: (CAS) 73979; H. maciilata approx- proper is not ossified, but consists of carti- imans from Colonia Dublan, Mexico: (BYU) lage plates from which cartilaginous rods 11370, 17099; H. maculata hunkeri from extend dorsad to add to and support the Chihuahua, Mexico: (BYU) 15782, 15785, membranes that protect the brain. Eyes are 15788, 15789; H. propinqua propinqua from large, and only a thin sheet of cartilage sep-

Padre Island, Cameron Co., Texas: (CAS) arates them medially; there is no apparent 16187; Uma notata inornata from Riverside area of ossification, even in mature individ- Co., California: (BYU) 3263, 3266, (CAS) uals. 22824, 22826; U. n. cowlesi from Sonora, The sand lizard skull follows the basic Mexico: (BYU) 30144, 30156; U. scoparia plan of Sceloporine lizards as described by 38 Great Basin Naturalist Vol. 37, No. 1

Ethridge (1964) and Larsen and Tanner distinct, with Cophusaurus midway between (1974, 1975); there is a great deal of unifor- CalUsaunis and Holhrookia. mity within the sand lizard group. We will One of the first variations noticed, as not give detailed descriptions of each bone skulls were being prepared, was that Co- here; however, these data are available to phosaurus and Holhrookia had a para-occipit- those who may desire them. We will, how- al process directed anterolaterally. That of

ever, describe the variations from the Sce- CaUisaurus and Lhna is directed lateral or loporine skull as well as the differences be- slightly posterior. As a result of this varia- tween the sand lizard genera. tion, variations in the length and width of The following is a list of the skeletal ele- the quadrate, squamosal, jugal, and postor- ments measured and described (they are il- bital were noted. In lhna and CaUisaurus lustrated on Figs. 1, 2, 3, 4): the ventral articulating process is ventral to the basioccipital, whereas in Cophosaurus

Basioccipital Jugal and Holhrookia the quadrate is much short- Supraoccipital Postorbital er. Uma and CaUisaurus also have a wider Vomer Dentary Maxilla Splenial squamosal, and the squamosal and jugal just Frontal Hyoid meet. In the earless genera the jugal pushes Parietal wing Posttemporal fossa Quadrate Exoccipital in between the squamosal and postorbital. Surangular Ectopterygoid In one Uma individual the squamosal and Coronoid Premaxilla jugal failed to meet, and the postorbital Orbit Prefrontal Suprateinporal fossa Parietal had pushed in between them. Some other Basisphenoid Squamosal variations (such as the configuration of su- Pterygoid Articular tures between the frontal and parietal, the Palatine Angular Nasal Temporal fossa frontal and nasals, the basisphenoid and ba- Infraorbital fossa sioccipital, and the maxilla and premaxilla, as well as proportional variations in the The sand lizard skulls differ from the gen- maxilla, postorbital, and premaxilla) were eral sceloporine skull in that they lack the also found, but they were slight and had no lacrimal and the postfrontal bones. They significance. These are attributed to individ- differ among themselves in several ways, ual variation on the species or subspecies but most of the variance seems to be associ- level. ated with the posterolateral position of the skull. The discriminant analysis selected 116 Myology ratios that could aid in discriminating the four genera. Six measurements were found The myology of the neck and throat re- to be important. Every ratio selected in- gion has been carefully studied. Axtell cluded at least one of these six. They are (1958) pointed out that the inter- listed along with their frequency of use: mandibularis muscle in the most anterior re- squamosal width (26), quadrate length (26), gion of the throat is degenerate. The gen- mandible length (20), hyoid length (20), ioglossus is therefore the most ventral mandible width (19), and maxillarv length muscle in that region. This condition is con- (15). stant throughout the sand lizard genera. Representative ratio comparisons are giv- The variations within the sand lizard genera en to illustrate the separation and relation- are found in the intermandibularis muscles, ships of genera. Figures (1-4) of the lateral, depressor mandibularis, constrictor colli, and dorsal, and ventral aspects of the skull are the omohyoideus-sternohyoideus complex. also presented, including the lateral and me- The intermandihularis anterior super- dial views of the lower jaw and the dorsal ficiaUs (Figs. 5, 6) is a small muscle. In view of the hyoid. lhna, it is distinctly fan shaped. In CaUi-

Earl (1961a, 1961b, 1961c, and 1962) re- saurus and Holhrookia it is not fan shaped, ported on the osteological variations in the and Cophosaurus shows a slight amount of ear and indicated that all four groups were fanning. In Holhrookia the fibers of this March 1977 Cox, Tanner: Lizard Morphology 39

Fig. 1. The skull osteology of Callisaurus BYU 3079: A. lateral view of skull; B. lateral view of lower jaw; C. medial view of lower jaw; D. dorsal view of skull; E. ventral view of skull; F. dorsal view of hyoid. The symbols used are: an-angular 40 Great Basin Naturalist Vol. 37, No. 1

Fig. 2. The skull osteology of Uma BYU 3266: A; B; C; D; E; F; same as Fig. 1. The symbols used are the

same as Fig. 1. March 1977 Cox, Tanner: Lizard Morphology 41

Fig. The 3. skull osteology of Holbrookia BYU 15783: A; B; C; D; E; F; same as Fig. 1. The symbols used the same as Fig. 1 42 Great Basin Naturalist Vol. 37, No. 1

symbols used are Fig. 4. The skull osteology of Cophosaurus BYU 30518: A; B; C; D; E; F; same as Fig. 1. The

the same as Fig. 1. March 1977 Cox, Tanner: Lizard Morphology 43

Lhna BYU 3263; B. Callisaurus BYU Fig 5 Lateral view of head and neck musculature; superficial depth. A. symbols used are: am-adductor mandibulans 2943- C. Holbwokia BYU 15782; D. Cophosaurus BYU 30512. The au-auditory meatus; cc-constrictor colli; dm- externus medius; as-adductor mandibularis externus superficialis; profundus; ias-mtermandibulans anterior depressor mandibularis; gg-genioglossus; iap-intermandibularis anterior oris; mhl-mandibulohyoideus I. superficialis; ip-intermandibularis posterior; la-levator angularis 44 Great Basin Naturalist Vol. 37, No. 1

las iap

mh II

mh I pm

d m

.cc

sh I sh II oh

first depth at right. A. Uma BYU 3263; Fig. 6. Ventral view of throat musculature; superficial layer at left and The symbols used are: cc-con- B. Callisauru-s BYU 2943; C. Ilolbrookia BYU 15782; D. Cophosaurus BYU 30512. anterior profimdus; ias-mter- strictor colli; dm-depressor mandibularis; gg-genioglossus; iap-intermandibularis mhll-mandibulo- mandibularis anterior superficialis; ip-intermandibularis posterior; mhl-mandibulohyoideus I; I; shil-stemohyoideus II. hvoideus II; oh-omohyoideus; prn-pterygomandibularis; shi-sternohyoideus March 1977 Cox, Tanner: Lizard Morphology 45 muscle pass posteromedial, whereas in the expanded anteriorly to partially cover the other three genera they pass transversely or tympanic cavity. fan out. The sternohyoideus I and omohyoideus

The intemnandihukiris anterior profundus are closely related, and there is considerable (Figs. 5, 6) occupies a position posterior and confusion in the literature concerning them. dorsal to the intermandibularis anterior su- The position taken here is that those por- perficialis, and anterior and dorsal to the in- tions that originate on the scapula and cla- termandibularis posterior. In Uma the fibers vicle are omohyoideus, and those portions extend medially, with only a few fibers at that originate on the sternum are ster- each end fanning out. In Cophosaurus it is nohyoideus. distinctly fan shaped, and in Callisaurus it Both muscles are deep to the constrictor fans out to a lesser degree. In Holbrookia it colli, and the episterno-cleidomastoideus. is slightly fan shaped, with most fibers slant- The muscle dorsal to them is the sterno- ing posteriorly. There were two areas of hyoideus II. variation seen in the neck musculature. The omohyoideus (Fig. 6) takes two The constrictor colli (Figs. 5, 6) is the su- forms; in Uma and most species of Hol- perficial muscle of the neck, originating in brookia it has a single head originating on the dorsolateral fascia of the neck and in- the scapula and clavicle. In Callisaurus, serting in the ventral raphe of the throat Cophosaurus, and some Holbrookia the omo- posterior to the intermandibularis posterior. hyoideus is divided for its entire length,

It is one or two muscle fibers thick, rather connected only by a myocomma located narrow, and the origin is broader than the midway between the origin and insertion, insertion. bisecting the muscle and binding the muscle In all four genera the muscle fibers of the fibers together. This myocomma also bisects constrictor colli reach the mid-throat area, the sternohyoideus I, and the two muscles but they originate in a facia without reach- are bound firmly together by it. ing the dorsal skeletoginous septum. The omohyoideus can be easily separated

The constrictor colli is widest in Uma. It from the sternohyoideus posterior to the covers from the posterior edge of the tym- myocomma, but they cannot be distin- panum to the shoulder, nearly covering the guished anterior to it except by position. depressor mandibularis completely. In the The sternohyoideus I (Fig. 6) originates other three genera it is more straplike and on the sternum and inserts on the proximal only fills half the space between the posteri- end of the ceratobranchial I and II. The or edge of the tympanum and shoulder, myocomma is at its junction with the omo- being centered in this area. hyoideus, and it unites the two muscles. The The depressor mandibularis (Figs. 5, 6) medial portion of the omohyoideus cannot originates in the mid-dorsal raphe, along the be distinguished from the sternohyoideus an- posterior borders of the parietal bone and terior to this myocomma in all genera. parietal wings. The insertion has three slips; one inserts deep to the pterygomandibularis Statistical Analysis on the articular process of the lower jaw. Another passes superficially to the pterygo- The osteology of the skulls was analyzed mandibularis and the intermandibularis pos- by taking 43 measurements from each skull terior; it inserts on the ventrolateral surface and by calculating all possible ratios. The of the mandibular rami by interdigitating at Statistical Package for the Social Sciences right angles with these muscles. The third (SPSS) discriminant analysis was employed slip inserts on both sides of a tendon that to determine which ratios were of value in extends dorsally from the articular process. distinguishing genera and if the lizards The attachment of this slip to the articular could be classified by using them. The theo-

is superficial to the deep slip mentioned ry and use of discriminant analysis is de- above. In the earless lizards (Cophosaurus scribed by Klecka (1975). From each skull and Holbrookia) a portion of this muscle is 903 ratios were generated, and those suf- 46 Great Basin Naturalist Vol. 37, No.

ficient to separate one genus from the other nant analysis, it is possible to classify the three were used. four genera. Of 21 tests, classification The discriminant analysis proceeds in a agreed with the present taxonomic system stepwise fashion by selecting the single best- in 17 of them. The first classification error discriminating variable, and then selects a was in Test 7, where a CaUisaurus and a second on the basis of its ability to improve Cophosaums were both classified as Hol- the value of the discrimination criterion in brookia. Only three ratios were involved, combination with the first variable. Third and all three involved the squamosal width and subsequent variables are similarly se- divided by the vomer width, palatine lected according to their ability to contrib- length, and palatine width respectively. ute to further discrimination. A plot of the These ratios were effective in separating discriminant score in two dimensions, a ter- Uma from the other three, but were not ritorial map, and a classification based on useful in distinguishing between the other the preceding analysis are given. Range, three genera. mean, and standard deviation of ratios for The second classification error occurred each genus are also given, and examples are in Test 8. Here a CaUisaurus and a Hol- presented in Figs. 7 and 8 along with a plot hrookia were both classified as Cophosaums. of the ratios (Figs. 7-11) that illustrates rel- Four ratios were involved, and each one ative relationships between genera. These used the squamosal width divided by the figures are only examples of the ratios, and pterygoid width, the epipterygoid width, were selected because they clearly demon- the hyoid length, and the hyoid width. strate the results referred to below. Whereas Uma was well separated in Test 7, A multivariate analysis of variance was it was not well separated in Test 8. performed to determine the significance of The most confused classification was in differences between the four genera. The Test 15. Here one CaUisaurus and one Hol- comparisons were based on a non-orthogan- brookia were both classified as Cophosaums, al set such that the differences between one CaUisaurus was classified as Uma, one Uma and the other three genera were test- Cophosaurus was classified as Holbrookia, ed (comparison #1), the differences be- and one Holbrookia was classified as CaUi- tween CaUisaurus and Cophosaums were saurus. Two ratios were used, and they tested (comparison #2), and, finally, the were derived from the mandible width di- differences between Cophosaums and Hol- vided by the frontal width and the nasal brookia were tested (comparison #3). width. Uma is the most distinct in this test; Using 116 ratios selected in the discrimi- however, the individual plot scores show

CalUsa March 1977 Cox, Tanner: Lizard Morphology 47

considerable variation, and there is no dis- crete grouping to distinguish the separate genera. The last confused classification was in Test 17. Here four ratios were used that involved the mandible width divided by the palatine length, palatine width, epipterygoid length, and the mandible length. In this classification a Callisaurus and Co- phosaurus were both mistaken for Hol- brookia. The plot indicates a complete separation of Uma, but with an overlap of the other three genera. Over all 21 tests the centroids were separated on the average of the following dis- tances: Uma was separated from Callisaurus by 2.10 mm, from Cophosaurus by 2.44 mm, and from Holbrookia by 2.67 mm; Cal- lisaurus was separated from Cophosaurus by 1.19 mm and from Holbrookia by 1.58 mm; and Cophosaurus was separated from Hol-

Fig. 9. Range, mean, and standard deviation in the brookia by 0.92 mm. These centroids are four current genera plotted for the ratios of: A. squa- derived from the discriminant functions, mosal length /squamosal width; B. squamosal which in turn are derived from linear com- width /quadrate length; C. jugal length/squamosal variables in each test. width; D. squamosal width/mandible length. binations of the used The purpose for the discriminant analysis was to find ratios that would discriminate

Holbrookia

Fig. 10. Range, mean, and standard deviation in the four current genera plotted for the ratios of: A. quad- Fig. 11. Range, mean, and standard deviation in the rate length /quadrate width; B. maxillary four current genera plotted for the ratios of: A. man- length /quadrate length; C. jugal length /quadrate dible length/mandible width; B. jugal length /mandible length; D. skull length /quadrate length. length; C. skull length/jugal length. 48 Great Basin Naturalist Vol. 37, No. 1 between the groups; this goal was achieved. The probability of error in differentiating

It is also desirable to determine how well between Callisaurus and Cophosaurus is each group is defined, and if it is signifi- similar to the probability of error in differ- cantly different from all other groups. The entiating between Cophosaurus and Hol- SPSS program does not provide this infor- hrookia (average between 9 percent and 12 mation, but it is possible, by studying the percent), verifying these statements. plots (Figs. 7-11), to see that the range of These data are based on 116 ratios that Callisaurus overlaps the range of Holhrookia were found to be the best discriminators of and/or Cophosaurus in nearly all ratios the 903 ratios examined. It is noteworthy plotted. The range for Uma is only occa- that by using the very best osteological dis- sionally overlapped by the other genera, criminators, the genera are often not clearly and it is usually only Callisaurus that over- separated. laps Uma. The multivariate analysis of variance was performed to determine the degree of sig- D ISCUSSION nificance between the four genera. The non- orthoganal set of comparisons was as fol- Sand lizards are a closely related group lows: according to Smith (1946), Norris (1958), Etheridge and Clarke Comp. Cal Coph. Hoi. Uma Axtell (1958), (1964), (1965). Smith referred to them as a closely 1 1 1 1 -3 knit group and listed their common charac- 2 -1 1 teristics as being oblique labials, granular 3 1 -1 dorsal scales, small head scales, a gular fold, The degrees of freedom, F-ratios, and actual a peculiar median triangular postmental, probability for each F-value are presented several prominent postlabials, much the in Table 1. same habits, similar habitat, scoop-shaped The differences between Uma and the heads, flaring labial regions, and a counter- other three genera are highly significant, sunk lower jaw. Axtell (1958) listed 22 char- but the differences between the remaining acters that he felt would describe ancestral three genera are only slightly significant, sand lizards. With only a few exceptions, and in many cases the differences are in- this list of characters might just as well ap- significant. ply to other sceloporine lizards.

Uma is therefore the best differentiated Callisaurus, Cophosaurus, and Holhrookia by these tests. The other three genera are exhibit many of the primitive characteristics close together, and although they can be mentioned by Axtell. Each genus, however, distinguished on the computer, their degree shows specializations that vary from those of separation is slight. listed. Callisaurus is similar to Axtell's cri-

Table 1. Summary of F-ratios from eight multivariate analyses of variance tests. March 1977 Cox, Tanner: Lizard Morphology 49

teria for the primitive condition, with the pothesis that sand lizards are highly special- most striking speciahzations being increased ized among the iguanids. length of tail and limbs and a more slender In discussing the osteology of Holbrookia, body form. Holbrookia is also similar to an- Axtell (1958:24) stated: cestral sand lizards except for the covered In general the osteology of the genera Calli- tympanum. Body form in Holbrookia is not saurus and Vma corresponds closely with that of Holbrookia, so this discourse may apply just as proportionately slender as it is in Calli- as well to the entire sand lizard section of the saurus, nor is the tail as long. The problem- family iguanidae. atic Cophosaums has characteristics of both. Its body form, limbs, and tail approach Development of the covered tympanum

those of Callisaurus, but it has a covered appears to be related to the osteological tympanum like Holbrookia. Uma has devel- variations observed in this study. The quad- oped, to a greater degree, the dorsovent- rate, squamosal, paraoccipital process, and rally flattened body and the toe fringes. mandible are all adjacent to the ear, and all

Callisaunis, Holbrookia, and Cophosaurus exhibit variations (Figs. 1, 2, .3, and 4). With occupy generalized habitats, probably sim- the loss of the external ear, the quadrate is ilar to that of the ancestral stock. Uma, on reduced in size, and the paraoccipital proc- the other hand, is restricted to a sand dune ess is directed forward, the mandible is habitat. shortened, the squamosal is narrowed, and

the hyoid is also shortened. These modifica- tions of the skull are apparent in earless Osteology sand lizards and are less modified in sand Comparisons of skulls of Ctenosaura lizards having an external ear. Callisaurus (Oelrich 1956), as well as general accounts and Uma are alike in that the paraoccipital of reptile osteology by Williston (1925), Ro- process is directed caudad, the quadrate mer (1956), and Avery and Tanner (1964, proportionately larger, and the mandible 1971) indicated that osteological character- long and wide in comparison to the earless istics of iguanid lizard skulls are generally forms (Figs. 1, 2, 3, and 4). In Uma the de- stable within a genus. Studies on Sauro- gree of development of these characters is malus (Avery and Tanner 1964), Croto- different because the squamosal is wide. A phytus (Robison and Tanner 1962), and ratio of skull length divided by squamosal Ctenosaura (Oelrich 1956) portrayed the ap- width shows: (a) Uma ranging from 5.4375 parent general stability of osteological char- to 7.1379; (b) Callisaurus ranging from acters found in iguanid skulls; however, 9.6975 to 12.3636; (c) Cophosaurus ranging skulls of Callisaurus, Cophosaurus, Hol- from 10.3333 to 13.8889; and (d) Holbrookia brookia, and Uma observed in this study are ranging from 11.0833 to 13.7500 (from Fig. peculiar to iguanid skulls as portrayed by 7). The quadrate and mandible length and the above authors because there is stability width are similarly enlarged in Uma when within the sand lizard genera as a group compared to the other groups. These differ- rather than within a single genus. The lac- ences are sufficient to permit the computer rimals and postfrontals are also absent in all to distinguish between these measurements the sand lizards, a condition not generally in Uma and those same characteristics found in iguanid skulls, except that Jenkins found in Callisaurus and the earless group. and Tanner (1968) found that two species There is some variation in the position groups of phrynosoma also lack these skull and articulation between the squamosal, bones. Etheridge (1964) pointed out the ab- jugal, and postorbital. In all except some sence of the lacrimals and postfrontals in Uma individuals, the jugal reaches the squa- sand lizards. mosal. In Callisaurus it edges between the Deviation by sand lizards from the gener- squamosal and postorbital. In Holbrookia al iguanid skull, particularly evidenced by and Cophosaurus the degree of encroach-

the fusion or loss of the lacrimal and post- ment is increased. This may be a result of frontal bones, is evidence supporting the hy- the forward direction taken by the para- 50 Great Basin Naturalist Vol. 37, No. 1 occipital process and the shortening of the vable differences that are discussed below jaw. Uma is unique in that the jugal fails to (Figs. 5 and 6). reach the squamosal in some individuals, in The intermandibularis muscles show some which case the postorbital is found wedg- variations that are useful in distinguishing ing between them (Fig. 3). In other Uma the genera. Uma is most distinct, with its individuals a mere contact is made without intermandibularis anterior superficialis mus- any overlap of the squamosal and jugal. cle being fan shaped (Fig. 6). This condition

is contrasted with that found in Holhrookia, That these variations exist is verified by where the transverse mandibulae muscles the statistical analysis. The SPSS discrimi- are so nearly parallel that the borders of nant analysis was able to identify character- each muscle are difficult to discern. Co- istics that were capable of separating the phosaurus and Callisaurus exhibit an inter- genera into distinct groups. However, the mediate condition with some fanning seen, analysis of variance points out that differen- but not to the extent seen in Uma. Co- ces between Callisaurtis, Copho.saurus, and phosaurus can be distinguished from Calli- Holhrookia (as identified by SPSS) are insig- saurus in that fibers of the intermandicularis nificant and that Ihna is indeed a distinct anterior superficialis extend posteromedially, group. The F-ratios derived from the analy- and in Cophosaurus, a portion of the in- sis of variance illustrate these facts. The sertion of the intermandibularis anterior tests comparing Uma with the other three profundus is found anterior to the super- genera have high F-values (96.377 to 7.797) and consequently low probability of making ficialis, a condition not seen in Callisaurus. depressor mandibulae also shows classification errors (from 0.000062 percent The some variations. In the earless lizards there to 0.79 percent). Therefore the differences is an expanded anterior edge of this muscle, between Uma and the other sand lizards are which partially covers the enclosed tympa- highly significant. In comparing Callisaurus the with Cophosaurus, the F-values were found num. This muscle emerges from beneath constrictor colli to insert upon the man- to be lower (16.830 to 1.141), and con- dible, with its most ventral fibers inter- sequently the probability of classification er- digitating at right angles with the inter- ror is higher (41.24 percent to 0.077 per- mandibularis posterior. Furthermore, the cent). Only two of the eight tests were depressor mandibulae fibers extend much significant (below 2.5 percent probability of further along the mandibular ramus than in error). The tests comparing Cophosaurus the eared genera. In Cophosaurus these fi- with Holhrookia are similar to those com- mandibular ramus with only paring Callisaurus and Cophosaurus. The F- bers reach the a few interdigitating with the inter- ratios range from 31.231 to 1.973. The mandibularis posterior. probability of error is again higher (21.29 The omohyoideus is also variable in these percent to 0.026 percent). Low F-ratios and genera. In the unfolding of the evolutionary high error probability indicate that the dif- development of the omohyoideus, a branch ferences between the three genera are in- of the rectus cervicus originated on the sca- significant. pula and inserted on the hyoid. In sand liz-

ards it further developed into a complex of Myology muscles. In Uma the omohyoideus has a second head that originates on the sternum.

The literature is void of studies dealing This then can be called sternohyoideus I. directly with myology of sand lizards. Earle Another muscle, the sternohyoideus II, (1961a, 1961b, 1961c, 1962) dealt with the arises on the sternum, passes deep to the

middle ear and also touched on the myol- sternohyoideus I, and inserts on the pos- ogy in the ear region. In this study, we will terodorsal edge of the ceratobranchial I. deal only with the myology of the head and Avery and Tanner (1964) designated this neck region. A comparison of the anterior muscle thyrohyoideus in Sauromalus, but,

anatomy of sand lizards shows some obser- since it clearly originated on the sternum in March 1977 Cox, Tanner: Lizard Morphology 51

sand lizards, it is designated sternohyoideus that the CaUisaurus-Holbrookia stock was II in this study. divided. The data available to us from this A division of the oniohyoidens has oc- study tend to support Norris' concepts con- curred in CaUisaurus, Cophosaiirus, and two cerning the radiation of sand lizards. Ac- specimens of Holbrookia {Holbrookia lacerata cording to Maslin (1952), "The basic as- CAS 73979 and Holbrookia m. approximans sumption upon which all taxonomic BYU 17099). Thus, in sand lizards the practices rest is that similar organisms are muscle may have one to three origins: the related." If we assume that sand lizards most lateral dorsal one is on the scapula, have occupied similar habitats and have the second is on the clavicle, and the most me- been subject to similar environments dial is on the sternum and interclavicle. The throughout their recent history, then we can omohyoideus also has two insertions: the assume that the degree of similarity be- most lateral division inserts on the distal tween groups is an indication of the close- two-thirds of the ceratobranchial I, and the ness of their relationship. Maslin (1952) also second and medial heads unite and insert on states that because internal characters are the proximal third of the ceratobranchial II less variable, they are of much greater val- and the basihyal. In Uma and for the most ue in establishing relationships than are ex- part in Holbrookia, such division of the ternal characters. The internal characters omohyoideus has not occurred, and the in- considered here indicate a closer relation- sertion is continuous along the ceratobran- ship between Holbrookia and CaUisaurus chial I, the basihyal, and the proximal third than between Uma and CaUisaurus, in-

of the ceratobranchial II. These myological dicating that Uma was probably the first of variations, although observable, are not of the sand lizards to break away from the an- great magnitude and may not be sufficient cestral line. to support generic status for CaUisaurus, Clarke (1965) examined the behavior and Cophosaurus, or Holbrookia. In all there is external morphology from the standpoint of an overwhelming myological similarity 20 characters; in 14 of them Cophosaurus within these three genera, and they are ob- was like CaUisaurus, in 5 of them Co- viously closely related to Uma. phosaurus was unique, and in only one was Cophosaurus like Holbrookia. In discussing these comparisons he states: Phylogeny The distinctness of Cophosaurus is evident. It

is intermediate in many features between CaUi- Norris (1958) and Axtell (1958) agreed saurus and Holbrookia, with the data indicating a closer that sand lizards began their radiation in affinity to CaUisaurus than to Hol- brookia. The uniqueness of Cophosaurus is most early or middle Miocene. This is the time clearly shown in the distinctness of the push-up when the Sierra Madre Occidental Range of pattern. Mexico was being built by volcanism along the western and southern borders of the On the basis of five characters, Clarke Mesa of Central Mexico (Schuchert 1935, would separate Cophosaurus as a separate

Miller 1942). Axtell indicated that this vol- genus. These five characters are: (1) place- canism split the sand lizards into two ment of the lateral bar: anterior for CaUi- groups, a Uma-Callisaurus group and a Hol- saurus, posterior for Cophosaurus, and cen- brookia prototype. Norris also believed the tral for Holbrookia; (2) body shape: slender sand lizards were divided at this time, but for CaUisaurus, intermediate for Co- indicated that Uma was isolated from the phosaurus, and stout for Holbrookia; (3) CaUisaurus- Holbrookia stock. Norris further middle ear: distinct with an external open- indicated that Uma was subsequently split ing for CaUisaurus, distinct without an ex- by continued mountain-building processes in ternal opening for Holbrookia, and inter- the mid-Pliocene, giving rise to the exsul mediate without an external opening for group and notata-scoparia stocks. He also Cophosaurus; (4) preferred body temper- postulated that it was during this same time ature: 39.2 C for CaUisaurus, .38.3 C for 52 Great Basin Naturalist Vol. 37, No. 1

Cophosaurtis, and 35.7-38.1 C for Hol- What is deplorable in splitting is the tendency to raise the ranks of groups without need, hrookia; and (5) push-up pattern: distinct in that is, without gaining any practical advan- all three groups. In four of the five charac- tage. One of the more evident symptoms of this ters the differences are only comparative, tendency is the appearance of many monotypic and do not indicate a clear-cut distinction; groups in classification. only in the fifth does Cophosauriis show a real distinctness. The proposal resulting from this study and An alternate interpretation of these data data examined from other studies would would have to conclude that there is not eliminate one monotypic genus and would enough difference to warrant generic status provide a better indication of the close rela- for Cophosaurtis; indeed, there also may not tionships that are so evident in the sand liz- be enough difference to warrant generic ards. status for Holbrookia. The variations de- Axtell (1958) believed that the sand liz- scribed are of the kind and magnitude used ards evolved under subhumid conditions, in the descriptions of species. Clarke (1965) not greatly different than the conditions ex- stated that the push-up pattern is the most isting today in the sand lizard range. He distinct feature of Cophosaurtis. Carpenter postulates that it was during the mid-Plio- (1963, 1967) described the same behavior cene that Holbrookia developed the covered for Uma, indicating that a genus is capable tympanum. He then states, "The species of supporting greater variation than Clarke previously known as Holbrookia texana, but has allowed for in Callisaurus, Cophosaurus, which now appears to belong in the Calli- or Holbrookia. saurus line of evolution, has probably devel- Guttman (1970b) also commented on oped the covered tympanum independ- Clarke's study, stating: ently." Axtell's phylogenetic tree for the

sand lizards is presented in Figure 12. A comparison of Callisaurus, Cophosaurus, Earl (1961a, 1961b, 1961c, and 1962) in- and Holbrookia (Clarke 1965) indicated the dicated that Cophosaurus was intermediate great similarity among these genera. According

to Clarke, the uniqueness of Cophosaurus is between Callisaurus and Holbrookia in ear most clearly shown by its distinctive push-up anatomy, but agreed with Axtell that ear- pattern. A comparison of the display-action pat- lessness evolved twice, reporting that re- terns of two species of Urosaurus (Carpenter 1962) or three species of Uma (Carpenter 1963)

SPECIALIZATION , indicated to this writer that sufficient in- ^ DIRECTION OF 3 trageneric variation exists to refrain from establishing a genus based on this display pattern.

Guttman was reporting his electrophoretic study of sand lizards, in which he analyzed the hemoglobin components and found that they were all identical. This is highly un- usual, especially for different genera. Elec- trophoretic techniques have been of value in confirming taxonomic relationships. This has been demonstrated by Dessaur et al. (1962), Dcssauer (1966), Gorman and Des- sauer (1965), Gorman (1966), Maldonado and Ortez (1966), and Guttman (1970a and TYMPANUM 1970b). The conclusion Guttman (1970b) COVERED came to, and the one that supports our con- SAND LIZARD clusions, was that the .sand lizards are more PROGENITOR closely related than their present taxonomic status indicates. Fig. 12. Phylogeny of the sand lizards according to Simpson (1945) states: Axtell (1958).' March 1977 Cox, Tanner: Lizard Morphology 53 lated groups have the potentiaHty to devel- cept. Earless sand lizards are closely related, op identical clines, and under similar their geographic ranges overlap, their habit- environmental conditions these identical ats are similar, their food requirements are clines may develop at different times and similar, the ear anatomy is similar, and we places. This concept was discussed by Mas- lack any evidence from fossil records that lin (1952), who put forth the idea while dis- they diverged before the earless character cussing morphological criteria of phyletic arose. Where evidence indicates a close tax- relationships. Norris (1958) and Clarke onomic relationship, as it does here, the (1965) also agreed with Axtell about the idea of a single evolution for the earless idea of separate earless evolution. character is most plausible. It is very un- The concept of two evolutions for earless- likely that the same character would evolve ness may be a major barrier to the under- twice in the same way in two groups that standing of sand lizard relationships. Since are as closely related as are earless sand liz- we lack a fossil record of sand lizards, there ards. (A proposed phylogenetic tree is given is no way of knowing when or how such a in Figure 13.) character came about. It has been suggested These data, when added to that of earlier (Earl 1961a) that it came about in response workers, seem to clearly indicate that sand to the burrowing habit, but this is purely lizards may best be represented by three speculative, as there are many burrowing genera: Uma, Callisaurus (as at present con- species that do not have a covered tympa- stituted), and Holbrookia. num (including Uma). A covered tympanum The characteristics that separate sand liz- " is not unique to "sand lizards because the ards into genera are few and not well de- agamid genus Tympanocryptis in Australia fined when compared to distinctions be- is earless, and so are some of the members tween other Sceloporine genera. The of Phrynocephahis. Phrynosoma has both relationship between Callisaurus and Hol- eared and earless members. Norris's (1958) brookia is especially close, with earlessness idea is acceptable when he says that CalU- (and its associated skull characters) and saurus and Holbrookia split in the early body proportions being the most striking Pliocene, with Holbrookia occupying the variants. Uma, on the other hand, appears table lands of the mesa of Central Mexico, to be well defined. It is felt that Holbrookia and Callisaurus having been isolated from is, therefore, a recent derivative of Calli- Holbrookia before their radiation to the more northern habitats. The habitats of the ^ DIRECTION OF SPECIAIIZATION ^ Chihuahuan desert and Sonoran desert are similar; the draconoides and texanus groups would have had an excellent opportunity to parallel each other sufficiently to account for the external morphologic similarities. In- ternal structures are not as accessible to external selective pressures and may, then, indicate more accurately the true relationships: that the texanus group is more closely related to Holbrookia than to

Callisaurus, which it resembles through par- allelism. That earlessness may have evolved twice TYMPANUM COVERED is possible, and it is most probable that there were separate evolutions for this character in the genera Tympanocryptis, Phry- SAND LIZARD PROGENITOR nocephalus, Phrynosoma, and sand lizards.

To theorize that it evolved twice in the Fig. 13. Proposed phylogeny of the sand lizards as sand lizards is, however, a questionable con- dictated by data developed from this study. 54 Great Basin Naturalist Vol. 37, No. 1

saiirus, evolving earlessness and an adapta- of two new subspecies of Holbrookia. Bull. Chi- tion for varied habitats in a relatively short cago Acad. Sci. 10(11):161-179. 1958. A monographic revision of time, perhaps since their separation in the the iguanid genus Holbrookia. Diss. Abstr. 19(6): 1476-1477. late Pliocene. 1960. Orientation by Holbrookia maculata Sand lizards, particularly the species and (Lacertilia, Iguanidae) to solar and reflected subspecies, particularly in H. maculata, in- heat. Southwestern Naturalist 5(l):47-48. dicate that this group has recently under- Baird, S. F. 1859. Description of new genera and species of North American lizards in the museum gone adaptive radiation. If recent geological of the Smithsonian Institution (Uma). Proc. past has been correctly interpreted by re- Acad. Nat. Sci. Philadelphia 10:253 (1858). cent paleontological findings (Etheridge Baird, S. F., and C. Girard. 1852. Holbrookia texana. 1961, Wells and Jorgensen 1964), the desert Proc. Acad. Nat. Sci. Philadelphia 6:124. Barbour, T. 1921. A new lizard from Guaymas, Mexi- areas of today, extending from Texas to co. Proc. New England Zool. Club 7:79-80. California, were very different as recently Blainville, H. M. D. de. 1835. Description de as 10,000 years ago, indicating that sand liz- quelques especes de reptiles de la Californie ard adaptative radiation must be relatively precedee de I'analyse dun systeme general recent. d'herpetologie et d'amphibiologie. Nouv. Ann. Mus. Natn. Hist. Nat. Paris, (3)4:232-296. Evidence from internal morphology and BocouRT, M. F. 1873-1897. Etudes sur les reptiles. geographical distribution indicates that ear- Mission scientifique au Mexique et dans less sand lizards should remain as two close- FAmerique Central-Becherches Zoologiques, ly related groups in the genus Holbrookia. (q.v.) part 3. Bogert, C. M., and E. E. Dorsom. 1942. .\ new lizard Data from comparative skull and throat of the genus Callisaurus from Sonora. Copeia anatomy, if used alone, indicate a very close 1942(3): 17,3-175. relationship between all genera in the sand Burt, C. E. 1931a. On the occurrence of a throat-fan lizard group, but it is felt that the dis- in the sand lizard, Uma notata Baird, with tinctions, however small, do indicate that notes on the adaptive specialization of the form. Copeia 1.5-16. Holbrookia has evolved from CaUisaums 1931(1): 1931b. On the occurrence of a throat-fan in sufficient distinctness stock and has achieved Callisaurus ventralis gabbii and two species of to be given generic status. It is, therefore, Crotaplnjtus. Copeia 1931(2):58. proposed that sand lizards be classified as Cagle, F. R. 1950. Notes on Holbrookia texana in Texas. Copeia 1931(2):58. they were before Cophosaiirus was split off Carpenter, C. C. 1962. A comparison of the patterns by Clarke (1965). This is as follows: of display of Urosaurus, Uta, and Streptosaurus. Uma notata Baird Herpetologica 18:145-152. Uma scoparia Cope 1963. Patterns of behavior in three forms of Uma exsul Schmidt the fringe-toed lizards, Uma. Copeia Uma pamphijgas Williams, Chrapliny, and Smith 1963(2):406-412. CaUisaums draconoides Blainville 1967. Display patterns of the Mexican iguanid Holbrookia texana Troschell lizards of the genus Uma. Herpetologica Holbrookia lacerata Cope 23(4): 285-293. Holbrookia maculata Girard Clarke, R. F. 1965. An ethological study of the igua- Holbrookia propinqiia Baird and Girard nid lizard genus Callisaurus, Cophosaurus, and Holbrookia. The Emporia State Research Studies 13(4): 1-66. Cope, E. D. 1880. On the zoological position of Texas. Literature Cited Bull. U.S. Nat. Mus., No. 17:1-51. 1883. Notes on the geograhical distribution of Batrachia Reptilia in western North Amer- Avery, D. F., and W. W. Ta.nner. 1964. The os- and ica. Sci. Philadelphia 36:10-11. teology and myology of the head and thorax re- Proc. Acad. Nat. gions of the obesus group of the genus Sauro- 1894. On the iguanian genus Uma Baird. Am. maliis Dumeril (Iguanidae). Brigham Young Nat. 28:4.34-435. Univ. Sci. Bull., Biol. Ser. 5(.3):l-30. 1895. On the species of Uma and Xantusia. 1971. Evolution of the iguanine lizards (Sauria Am. Nat. 29:938-939. Iguanidae) as determined by osteological and 1896. On the genus Callisaurus. Am. Nat. .30:1049-1050. myological characters. BYU Sci. Bull., Biol. Ser. 12(3): 1-79. 1900. The crocodilians, lizards, and snakes of AxTELL, B. VV. 1956. A .solution to the long neglected North America. Report U.S. Nat. Mus. for 1898, Holbrookia lacerata problem and the description pp. 15.3-1270. March 1977 Cox, Tanner: Lizard Morphology 55

Dessauer, H. C. 1966. Taxonomic significance of elec- the desert lizards, Callisaurus and Vma. Copeia trophoretic patterns of animal sera. Rutgers 1962(2):437-4.38. Univ., Serai. Mus. Bull. 34:4-8. Larsen, K. R., and W. W. Tanner. 1974. Numeric Dessauer, H. C, W. Fox, and F. H. Pauch. 1962. analysis of the lizard genus Sceloparus with spe- Starch-gel electrophoresis of transferrins, este- cial reference to cranial osteology. Great Basin rases, and other plasma proteins of hybrids be- Nat. 34(1):1-41. tween two subspecies of whiptail lizard (genus 1975. Evolution of the sceloporine lizards Cnemidaphoms). Copeia 1962:767-775. (Iguanidae). Great Basin Nat. .3.5(1): 1-20. DicKERsoN, M. C. 1919. Diagnoses of twentv-three Linsdale, J. M. 1940. Amphibians and reptiles in Ne- new species and a new genus of Lizards from vada. Proc. Am. Acad. Arts Sci. 73(8): 197-257. lower California. Bull. Mus. Nat. Hist., Maldonado, a., and E. Ortiz. 1966. 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