This article originally appeared in the Sonoran Herpetologist

The Case of the Lost Lizard

By Vincent D. Roth

Years Missing
Mysterious Specimens
Amazing Rediscovery

This title sounds like an Earle Stanley Gardner mystery story but happens to be an account of sleuthing in a non-fiction science mystery. All of the elements of a mystery are present - a missing link, unidentified people, unknown localities, incomplete bits of information and an exotic setting.

"A detective story!" is the comment made by friends who have heard it. Will the hypothesis prove correct? Will the lizard be found? This uncertainty makes mysteries exciting and is what makes science exciting. Maybe this is the reason so many biological scientists find that their vocation is also their avocation.

The missing clue in this mystery was Ditmars' horned lizard, last seen alive in 1898.

Most of the lizards along our borders are well known. Of 136 species from the United States listed in Hobart Smith's Handbook of Lizards, all but three are well documented. One of the three is the smooth-necked alligator lizard, Gerrhonotus levicollis levicollis (Stejneger), from western and southern Chihuahua and recorded originally from the "Mexican Boundary", but has not been found along the Arizona and New Mexico-Mexico borders since. Another is Bipes sp., a soft-bodied two-legged worm lizard. The nearest distribution of this genus is represented by Bipes biporus at the tip of Baja California where the habitat is damp sandy soil. In spite of rumors reported by Smith, it is doubtful that it ever was found in the mountains of southern Arizona because there is almost no damp sandy soil in this area. There have been many reports of two-legged lizards in the Chiricahua Mountains in Southeastern Arizona, but they consistently turn out to be the local alligator lizard, G. kingi (Gray), a slender lizard with tiny legs and a snake-like movement.

The mystery involving the third, Ditmars' horned lizard, could not be solved so easily. Two collections of ''ditmarsi'' were made in 1890 and 1897, for a total of three specimens and none had been found since, in spite of the efforts of many professional and amateur herpetologists, including myself. Trips through back country in Sonora in my well-traveled pickup Camper ''El Ghosto Blanco" produced nothing more than a few specimens of the regal horned lizard, Phrynosoma solare, along the valley roads. But the quiet old towns, each with its central plaza, church and adobe houses, looking as they did when missions were first established in the late 1600s, made the trips worthwhile.

The type specimen of Ditmars' Horned Lizard (<em>Phrynosoma ditmarsi</em>), USNM 36022
The type specimen of Ditmars' Horned Lizard (Phrynosoma ditmarsi), USNM 36022

The country is relatively unexplored by biologists and ditmarsi could occur anywhere. The roads, all narrow, winding, gravel or merely two ruts, skirted vast canyons, cottonwood lined rivers, outcrops of rhyolite and volcanic plugs standing stark above the landscape. They wound through narrow canyons with jungle-like foliage and bright-plumed trogons, up dry washes and over rocky mesas. Some places required a second run to get up the hilly roads, even in compound low.

In broad, sycamore-shaded Guadalupe Canyon, at the junction of the three states of Arizona, New Mexico and Sonora, I visited with John Magoffin, a local cattle rancher. He assured he had never seen a horned lizard in Guadalupe Canyon, nor in the adjacent Sierra San Luis.

From the Trail Dust Zoo near Bisbee, Arizona, came rumors that ditmarsi had been found by someone from California. Mr. Howard Hamm, a talented western artist and curator of the zoo who has a "green thumb" when it comes to animals (all his animals seem friendly!) assured me he had seen ditmarsi among the lizards brought to him. But later, when my hopes were raised, he decided that actually he hadn't seen any. While looking over the wide range in color of the douglassi in his cages, an onlooker commented, "You seem to know something about lizards." I admitted a moderate knowledge. "Well, I've seen one like that," he said, pointing at a douglassi, "reddish and flat, but with no horns. My boy picked it up at the Sunnyside Church in Douglas a few years ago."

This was exciting news, but when reconsidered and a second look taken at Douglas, it was discarded. Douglas lacked the necessary habitat.

Tim Walker, an amateur herpetologist from Paradise, Arizona, had made many hiking trips in the mountains below the border insearch of snakes and lizards. When it comes to locating snakes, Tim is one of the best and most persistent of the herpetologists, but he had had no succcss in locating the elusive ditmarsi. He and I spent many hours speculating on the habitat of ditmarsi, and came to the conclusion that it must he on one of the isolated mountain ranges - but which one?

Dr. Charles H. Lowe
Dr. Charles H. Lowe

Dr. Charles H. Lowe, a well-known herpetologist of the University of Arizona at Tucson, has been on the lookout for ditmarsi since the 1950's. He obtained a large collection of horned lizards from a mining engineer, Arthur Ruff from Cananea, Sonora, but they were all the mountain short-horned species, P. douglassi (Bell).

During the 1890-91 Lumholtz Archaeological Expedition, sponsored by the American Museum of Natural History (AMNH), F. Robinette collected the first specimen of ditmarsi, which languished for many years unidentified and with no locality in the AMNH herpetological collections. In 1968, a graduate student of Lowe's, Mike Robinson, began an analysis of the first part of the Lumholtz expedition, and in 1969 received a grant from the Arizona-Sonora Desert Museum to aid his search for the missing lizard. During his visits to the Southwestem Research Station (SWRS), we shared information accumulated separately and speculated whether ditmarsi was a valid species or might even be extinct. Mike tried following the guessed-at route of the Lumholtz expedition without success in finding the lizard.

The problem has been that the exact route of the expedition from Bisbee to Fronteras was not indicated by Lumholtz in any of his articles. His field notes were not on file at the AMNH and local newspapers of the 1890s didn't record the arrival and departure of the expedition. After searching through published reports it was possible to piece together some localities and dates given by J. A. Allen in his list of mammals and birds collected on the expedition. Although there were some errors in those records, a tentative route was established.

The expedition left Bisbee on September 6 and headed southwest to Greenbush Ranch (the present-day Stevenson Ranch) near Palominos, Arizona, crossed the Mexican border September 15 at the San Pedro River to the Mexican Aduana (Customs Station at San Pedro just south of Palomitas), and then turned east along the border where they stopped at Trincheras (September 20), Santa Barbara (September 21) and Leoncita (September 23). These small villages are uninhabited today and not on recent maps.

They probably stopped at Ojo de Agua at the north end of the Sierra de los Ajos and passed through the mountains. After reaching the "Fronteras Highway" they traveled south, arriving in Fronteras on September 23, and in Oputo (also spelled Opoto) on October 22. Although the lizard collected by Robinette had no locality nor a date available we speculated that ''Northern Sonora" would indicate all area north of Oputo, especially since the expedition didn't leave there until November 25 or so. late for horned lizards to be active.

Raymond L. Ditmars
Raymond L. Ditmars
Dr. Leonhard Stejneger
Dr. Leonhard Stejneger

The second and third specimens collected in 1897 had been turned over by a "Mr Eustace" to Raymond L. Ditmars, then Curator of Reptiles in the New York Zoological Park. Ditmars kept one specimen alive for about a year and commented on its peculiar habits in a letter to Dr Leonhard Stejneger, Curator in the Division of Reptiles and Batrachians at the United States National Museum (USNM). This letter of October 12, 1905 was located in the USNM archives by Dr. George Zug, Assistant Curator of the Division of Reptiles and Amphibians. Ditmars wrote, "This little creature used to jump clear off the ground in most clown-like fashion when annoyed, emitting a series of hisses like miniature sneezes."

The lizards were preserved and later forwarded to Dr. Stejneger for identification, and he subsequently described them in 1906 as Phrynosoma ditmarsi. Stejneger, naming them after his colleague Raymond Ditmars. In his letter to Stejneger, Ditmars wrote. "the most definite locality I can give you for this specimen is 'Northern Sonora, Mexico'." Stejneger gave the type locality as ''State of Sonora, Mexico, not far from the boundary of Arizona," elaborating slightly on the data available.

My attempts to locate Mr. Eustace, or information about him or his descendants failed. A letter to the Douglas Dispatch directed towards old timers, and searches through the Bisbee, Naco and Tombstone newspapers of the 1890s, and through the Arizona Historical Society files, and even telephone directories, produced no mention of his name.

At this point it became obvious that additional information was necessary before the species could be recovered. So far all efforts had produced only frustration, stronger leg muscles and worn out vehicles. For such a scarce lizard, it was impractical to search over so wide a country. Even in the Chiricahua Mountains, its relative the short-horned lizard, P. douglassi, was not easily found. Because of the similarity of the two species, Mike Robinson and I conjectured that it might be a mountain species rather than a low-land species like the Texas horned lizard, P. cornutum, or the regal horned lizard, P. solare.

After Mike and I had almost given up hope of finding the lizard, another possibility arose. While identifying the stomach contents of some local lizards for a student, Carol Simon, the solution to finding ditmarsi became apparent to me. The stomach contents of the three preserved specimens of ditmarsi could be studied to identify the insects upon which the lizards fed, determine their habitats and known distribution and then a summary of the data would identify the type of habitat and locality of ditmarsi.

The search was becoming more exciting.

In May 1970 an airmail request was sent to Dr. Richard G. Zweifel, head of the Department of Herpetology at the AMNH, for the stomach and large and small intestines of their specimen of ditmarsi (AMNH 557). They arrived by return mail.

The stomach contents were removed. washed repeatedly in alcohol and screened into various sizes. I then sorted them microscopically using progressively higher magnification. Many of the specimens were partially digested and in pieces, but a total of eighteen different items were separated: pebbles of andesite, seeds of three species of grasses, and fourteen insects.

Stomach contents of <em>Phyrnosoma ditmarsi</em>
Stomach contents of Phyrnosoma ditmarsi specimens; Table published by Vincent Roth in the Journal of the Arizona Academy of Science

This approach was so successful that I sent an immediate request to Dr. Zug at the USNM for the stomachs of the other two lizards. One of the two had been kept in captivity for a year, so only one stomach would be of value. Imagine the concern and consternation when Dr. Zug replied that one lizard had been eviscerated! The other lizard was being sent by return mail. The question immediately arose - would Mr. Eustace have removed the stomach of the lizard that had died? Or would Ditmars have eviscerated a lizard that died in the laboratory? The question was pondered apprehensively since one specimen would be useless, the other of great value.

When the specimen arrived by registered mail, excitement charged the laboratory as I opened the package and one of the three known specimens in the world was unveiled. And as the cheesecloth shroud was unfolded, unveiled it was! Such an insignificant animal, alcohol soaked, gray, dead over seventy years, the tips of many tubercles rubbed off, the short horns just as Stejneger had described. With some trepidation. the lizard was opened by Ralph Luetke, a volunteer assistant at the Station, and the stomach and intestines removed.

We held our collective breaths as the first slit was made, and out popped gramma grass seeds, Bouteloua sp., and Apache harvester ant heads, Pogonomyrmex apache (Wheeler), the same seed and species of ant as found in the AMNH specimens. The stomach contents were from the Southwest and not laboratory food. We were on the right track.

Then began the process of sorting and identifying. I made the initial identifications and then made the specimens available to specialists, writing almost fifty letters and making an equal number of personal contacts. For instance, the weevils were taken to Karl Stephan, an amateur coleopterist (specialist in beetles) in Tucson, then sent to a specialist on weevils for a generic identification, and then on to a person who specialized on the specific genus. Everyone cooperated enthusiastically and, caught up in the spirit of the search, remarked, "Let me know if you are successful."

When sorting was finished, there were thirty different items the lizards had ingested, and of special importance, eight species of ants in one stomach. There were pebbles picked up accidentally by the horned lizard, indicating it had fed upon the ants as they carried pebbles from their nest. There were gramma grass seeds, almost one seed for each harvester ant! The lizard obviously was also feeding upon ants returning to the nest.

No specific identifications were available for the seeds, but several grass specialists hazarded guesses. I spent a day in the University of Arizona Herbarium comparing seeds and narrowed the possibilities to several gramma grasses of one type and to bullgrass, Muhlenbergia sp. Roy Snelling of the Los Angeles County Museum studied the ants and returned a summary of the habitats of the eight species. Later, other species were sent to additional ant specialists. Among them was one unique reticulated thorax and part of an abdomen of a ponerine ant, Gnamptogenys regularis (Mayr), previously known only from Tepic, Nayarit, Mexico. Were we wrong in assuming that ditmarsi came from near the border of Arizona?

The next bit of information also directed our attention southward. Dr. Ann Howden of Ontario, Canada recognized the three weevils as identical to an undescribed species of Pandeletius collected a few years before by her husband in the southern part of Sonora at Yecora, on a juniper at 7,000 feet.

Each time an identification was obtained, it meant searches through the literature and of the University ot Arizona insect collection for distribution records. Gradually information came in, and a pattern slowly developed. The distribution of most of the specimens showed an affinity for the mountains of southern Arizona or northern Sonora.

Other weevils, tiphid wasps, a male scale, jumping spiders, true bugs and grasshoppers were identified. Once of the grasshoppers was Barytettix h. humphreysii (Thomas) upon which Dr. Ted Cohn of San Diego State College was working at the time. Its distribution is west of Agua Prieta and Sierra San Jose near Naco, whereas the distribution of a related species, B. h. cochesei Gurney occurs east of Agua Prieta. One extremely unusual insect, a true bug with short wings, lateral thoracic horns, and a dorsal scutellar horn, was represented by only a few parts. After almost giving up attempts to identify it, I assembled the parts like a jigsaw puzzle, made a composite drawing and sent it to Dr. R. C. Froeschner of the USNM in Washington D.C.

Dr. Froeschner replied immeddiately that it was very close to a South American genus of largid bug, Thaumastaneis, known only from Bolivia and Brazil! It is similar to a local ant-mimicking, brachypterous (short-winged) true bug, Arhaphe cicindeloides Walker (which lacks the dorsal spines), a very common largid bug among the dead leaves in oak stands in the Chiricahua Mountains.

In another field, several geologists and petrologists suggested that the tiny pebbles were not adequate for a specific determination. However, the pebbles were described by W. H. Pierce of the Arizona Bureau or Mines as "a finely crystalline igneous rock characterized by plates or tables of plagioclase feldspar and a dark to red brown ferromagnesian mineral of undetermined species. A small amount of magnetic and other unidentified material was present. Quartz was not observed. Based upon spotty evidence. I would suggest that the material is diorite in composition."

Mr. Sidney Williams of the Phelps Dodge Corporation at Douglas, Arizona, felt that these mineral specimens were andesite, a close relative of diorite. He knew the areas below the border, and suggested that two mountain ranges be investigated, Sierra Manzanal, south of Cananea, and Sierra San Luis, near the Chihuahuan border, both of which had extensive deposits of andesite. We were able to eliminate Sierra San Luis because it was east of Agua Prieta and out of the range of the Barytettix grasshopper.

It was time to summarize the data. After many hours of discussion over meals, in my office and laboratory, over campfires, retelling the story of the missing lizard to anyone who would listen, and then sifting through their ideas, suggestions, and speculations, plans for the future evolved. Looking over the data, it was possible to come to the following conclusions:

The lizards had been collected in the fall of the year as evidenced by the expedition collections from northenr Sonora and probably in the month of September. The seeds, grasshoppers and jumping spiders found in the stomachs had been mature, reconfirming the time of year. The presence of gramma grass seeds, Apache harvester ants, andesitic pebbles in both stomachs indicated that the lizards were collected in the same area. The soil would probably be sandy red as Ditmars described the color of the live lizard; horned lizards normally blend well with the substrate. The specific habitat had been described by Snelling as ''a canyon habitat with a small stream, rocky slopes, grass, oak-juniper, possibly with sycamores on the canyon floor. It looked to me like the lizard was foraging above the streams, between the stream and the sides of the canyon."

Then I realized there had been extensive change in the habitats over the past seventy years - lower rainfall and over-grazing in many areas. Was I studying lizards taken from the extreme edge of their habitat? There were still so many variables that at times I was ready to give up.

The Changing Mile by Hastings and Turner describing climatic changes of southeastern Arizona during the late 1800s and early 1900s showed some significant transformations in the vegetation. If similar changes took place south of the border, insect (and lizard) life may have been altered significantly and marginal species such as the horned largid bug, Gnamptogenys ant, and the Pandeleteius weevil, as well as ditmarsi, may have been pushed further south.

While the identifications of the plants, insects and spiders were being obtained, extensive collections of ants were made in the Chiricahua Mountain area at elevations ol 4160 to a1most 10,000 feet to determine the altitudinal distribution and habitat preference for the species found in the lizards' stomachs. Most of these species occured sympatrically within 4,800 to 5,400 feet on dry hillsides often adjacent to riperian situations.

The key items to locate were the andesite (its magnetic properties made it especially valuable), grasses (conspicuous in the fall), Barytettix grasshoppers, Apache harvester ants, Gnamptogenys ant, largid bugs, and Pandeleteius weevils. With the time of year determined, knowledge of the general area in Mexico and its habitats, and an idea of the mineral make-up of the area, we started serious searches in the field in mid-summer of 1970. The best possibility appeared to be the Sierra Manzanal. One of the two ranges below the border with known deposits of andesite. The mountains at Cananea, nearby, had produced only douglassi, and to the east Sierra de los Ajos had been searched briefly with no success. We made several insect collecting trips into northern Sonora for samples of the organisms and pebbles found in the lizards' stomachs. The habitat in which most of the species occurred would likely be the place where ditmarsi would be found.

These trips with friends and volunteers from the SWRS required crossing the border with all the hassles involved with Mexican officials over papers for the pickup truck, birth certificates or lack of them, temporary visas, below-age students without written permission from parents, a neat beard (''He's a heepie!"), a German passport, and the often expected mordida (the extra pay for "extra service").

The first stop in Mexico would be the panaderia for a bag of birotes, the tasty, hard Mexican rolls, some small but flavorful Mexican bananas, tamarindos, dried seed pods with a citrus-acid like flavor, limes for hot limeade or for squeezing over fresh mangos, and bars of panocha, a raw sugar for energy food. Then through Agua Prieta, typically lacking direction signs, past the cemetery to the checking station, and then abruptly out into the backcountry - wide open vistas, no power or telephone lines, no billboards, and little fencing.

Maps from the American Geographical Society, U. S. Coast and Geodetic Survey (Aeronautical Charts) and the Secretaria de Agricultura y Ganaderia, Direccion y Meterologia from Mexico City gave little help. They were consistent only in their inconsistencies. Localities on one map were missing or spelled differently on another, altitudes varied considerably in the mountain ranges which never seemed to be in the same place. Roads which didn't exist were depicted with heavy lines, and good roads not even indicated! Still, the maps were of some value.

Our first destination was the west side of the mounta range we thought was Sierra Manzanal. On a back trail, while we were lunching on birotes and mangos a truck bounced out of the mountains with a load of copper ore. We flagged it down and found we were not in the Sierra Manzanal, but in the Sierra de los Ajos. So back up the road to Cananea, a relatively American-looking mining town, and then south on a different road to our goal.

We checked out each road into the Sierra Manzanal, most of them never having seen a grader or bulldozer, so it meant a slow, rough trip. Five or ten miles per hour is considered good progress. After an hour or so on one narrow road gouged out of the steep mountain side we came to a small cluster of brown corrugated-paper-clad shacks with the usual half-dozen or more small children and their pregnant mothers. We asked about the road and about horned lizards. The road went on for a couple of miles, but as for the lizards, they knew of none in the area. One relaxed fellow said they could be found at Sierra San Antonio to the west, but were very rare. Later a look at the map showed no mountain by that name.

A couple of miles up the road we parked at a deserted mine and looked over the area. The habitat didn't appear promising except for many of the ants we were looking for. Soon dark clouds, lightning and rain in the distance cut short our stay. Being caught in a cloudburst in this country can mean an unexpected stay of a few days if the roads turn into rivers or quagmires. We returned to Canon de Evans in the Sierra de los Ajos and drove five miles up a sycamore and oak-lined wash to make camp.

The area was still promising with the type of habitat described by Snelling and with many of the insects we were seeking, but no andesite. On our way home we stopped in Douglas to see Sidney Williams, a geologist who knows northern Sonora well, and he gave us the directions we needed to get into the Sierra Manzanal.

Our next trip into Mexico took us deep into this mountain range because we picked up a Mexican who was heading for his ranch and showed us new roads. He seemed to know nothing about horned lizards and again we wondered if we could be in the right mountain range. After we dropped him off we located a small stream, cooled off in the water and took a siesta (when in Mexico, do as the Mexicans do). Some collecting in the area again showed a few of the insects in which we were interested, also some red rock similar to what we were looking for, but no lizards. That evening we camped beneath an old oak and had our usual dinner of potatoes wrapped in aluminum foil and baked in hot coals, birotes and fresh cantaloupes. Debris nearby indicated that many years ago this had been the site of a large mining camp. We wondered if Mr. Eustace had been a mining engineer and collected the lizards right here. On a nearby hill we saw and heard a drilling rig, indicating current drilling activity.

That night horizontal streaks of lightning broke into fingers of light and then ended in balls of fire . . . one of the greatest displays ot lightning I have ever seen. With the thunder, then came rain, and later a herd of curious burros. It was hard to sleep under my plastic ground cover. After a breakfast of corn pancakes, bananas and hot chocolate, we explored some nearby mine shafts, searched for horned lizards and then climbed the hill to investigate the drilling operation. ,We found an engineer, Hector Lopez, in charge, and with the help of my daughter, Susie, who had spent some time in Mexico, we communicated fairly well. ,After the usual. "What are you doing up here?'' from both sides, we got down to business.

"Any horned lizards? we asked.

''Si!" His children had been playing with them last week in the brush around the drilling rig. He drew a reasonable facsimile of a horned lizard then then cinched it by saying it squirted blood out of its eye, characteristic only of horned lizards.

I offered a reward of 100 pesos (about $10) to anyone who would get a specimen for me that turned out to be ditmarsi. With this agreement, we left with a promise to return soon.

Over two weeks passed before we could return and then we found that Senor Lopez had left for Mexico City where his wife was having a baby. In the meantime, we had studied the material taken on the previous trip and believed that we were in the right area, but intensive searches around the drilling rig produced no horned lizards. A new engineer. this time an American, Paul Geiger, was at the rig and communication was easy. He promised to obtain a lizard for us if possible. Other searches in the area produced no more likely place for ditmarsi. We returned to Canon de Evans to Camp and once again decided that the Sierra de los Ajos couldn't be the right locality.

Almost two weeks later a call came from Cananea. It was Paul Geiger asking if I could meet him in Douglas the following morning. He had a lizard! At the Station the excitement was at high pitch and everyone wanted to go to town immediately. We arrived early at the appointed spot and waited. As he drove in, we dashed up and were handed a small box. We cracked open the lid slightly and out peered a very spiny horned lizard. Our hopes died. ''A douglassi!" was all I could say at first, but then added. "It's a good record anyway." We sent a few dollars along for the collector as a consolation prize, and went home wondering where we would look next. At the Station the specimen was turned over to Chuck Lowe, who peered through a hole in the box and agreed it was a douglassi.

The next day a call came from Chuck. "Mike and I are coming down tomorrow." Just a flat statement, no reason, no nothing. Something was in the wind. They arrived the next morning with the electrifying news, the lizard had been identified by its abdominal keeled scales as ditmarsi! There still was a slight question in Chuck's mind, but in the meantime the type of the species had been requested for comparison. More specimens were needed for confirmations so it was back to Mexico.

Adult female <em>Phrynosoma ditmarsi</em> from the Sierra Manzanal
Adult female Phrynosoma ditmarsi from the Sierra Manzanal

This time, accompanied by Chuck and Mike, we decided to check out the road along the border to Rio San Pedro and possibly locate some of the Lumholtz Expedition tracks. The road was unproductive for lizards, but a picnic site along the river had a record sized wild grape vine a foot in diameter near the base. The back road eventually led along the river, across farm lands, through grasslands and ejidos to Cananea. We located none of Lumholtz's route.

We drove into the Sierra Manzanal and up a narrow mining road where we had to back up to make one turn on the precipitous mountain side to the drilling rig. I introduced Paul to Chuck and Mike and we made arrangements to obtain additional specimens of ditmarsi.

We looked carefully for lizards, found none, but took notes on this habitat. It was similar but not identical to the habitat we expected because it was on top of a rocky oak-covered hill with sandy red soil rather than in a canyon. Without a doubt we were near, but not necessarily at the type locality.

The rest of the tale was anticlimactic . . . we obtained more specimens, the identity of the lizard was confirmed, and the rediscovery was written up (Lowe, Robinson and Roth 1971). Stomach contents provided additional information on the food habits of these lizards (Roth 1971). The search was over . . . and successful. All that remained was to tell the story again and again to interested biologists and herpetologists who almost invariably replied, "Sounds like a detective story" - which it was!

A Ditmars' Horned Lizard (<em>Phrynosoma ditmarsi</em>) from northern Sonora © Jason Jones / HERP.MX
A Ditmars' Horned Lizard (Phrynosoma ditmarsi) from northern Sonora


Many thanks to David Hardy, Sr. and Karen Hayes who typed and repeatedly improved this paper.


Allen, J.A. 1893. List of mammals and birds collected in northeastern Sonora and northwestern Chihuahua, Mexico, on the Lumholtz Archaeological Expedition 1890-92. Bulletin American Museum of Natural History Article III, Vol. 5:27-42.

Ditmars, R.L. 1930. The Reptile Book. Doubleday, Doran and Co., Garden City, NewYork, 472 pp.

Hastings, J.R., and R.M. Turner. 1965. The Changing Mile. University of Arizona Press, Tucson. 317 pp.

Lowe, C.H., M.D. Robinson and V.D. Roth. 1971. A population of Phrynosoma ditmarsi from Sonora, Mexico. J. Arizona Acad. Sci. 6:275-277.

Roth, V.D. 1971. Food habits of Ditmars' horned lizard with speculations on its type locality. J. Arizona Acad. Sci. 6:278-281.

Smith, H.M. 1946. Handbook of Lizards. Comstock Publishing Co., Ithaca, New York.

Stejneger, L. 1906. A new lizard of the genus Phrynosoma from Mexico. Proc. U.S. Nat. Mus. 29:575-567.

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