Novyitates Published by the American Museum of Natural History City of New York February 25, 1953 Number 1610

AVMEIRiICAN MUSEUM NOVYITATES PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CITY OF NEW YORK FEBRUARY 25, 1953 NUMBER 1610 THE OPILIONID FAUNA OF CHIAPAS, MEXICO, AND ADJACENT AREAS (ARACHNOIDEA, OPILIONES) BY CLARENCE J. AND MARIE L. GOODNIGHT CONTENTS INTRODUCTION ..................................................... 1 Acknowledgments ................................................ 2 Historical Factors that may Influence Distribution of Opilionids in Chiapas ....................................................... 3 Ecological Factors that may Affect Distribution of Opilionids .......... a Present-day Opilionid Distribution ................................. 7 Gazeteer of Collecting Localities ................................... 9 SYSTEMATIC STUDY ................................................. 12 REFERENCES CITED ................................................. 76 INTRODUCTION During the course of extensive studies on the opilionids, or phalangids, we have become increasingly impressed with their possible value as indicators of zoogeographical and distributional patterns. The reasons for these conclusions are several. Among them is the fact that these animals are old geologically; thus their distribution has been molded by the many geological events of the different epochs. Also they are not able to fly, so must rely upon their own ability to crawl slowly about or upon chance events for any extension of their ranges. Before there can be any validity to the conclusions concerning the distribution of these animals as influenced by historical geology and modern ecology, the classification of necessity must rest on surer concepts than have been previously provided. The problem thus is a twofold one: first, to study the possible adoption of new 1 Department of Biological Sciences, Purdue University, West Lafayette, Indiana. 2 AMERICAN MUSEUM NOVITATES NO. 1610 taxonomic methods, and, second, to clarify the distribution of these animals. The area selected for this study was the state of Chiapas in southeastern Mexico. This state is extremely mountainous and presents conditions that vary from high mountains of pine and oak forests to lowlands covered with tropical rain forest. All variations of humidity are encountered, from the saturated rain forests to the dry scrub areas. Again, various geological ages are well represented. The mountains of the Mesa Central date from the Cretaceous, while those of the Pacific range were born in the volcanic upheavals of the Pleistocene and Recent epochs. These coastal mountains are still in the throes of geologic adjust- ment. Chiapas thus has both historical and ecological features to recommend it. For the taxonomic portion of the study, large series of animals were collected in many different localities, and their variations were studied. By this means it has been possible to alter radically our generic concepts and thereby to demonstrate phylogenetic relationships. By studying the variability of these species and by using the breeding population as a unit, we feel that the taxonomy of these interesting arachnids is brought more into line with modern taxonomic concepts. ACKNOWLEDGMENTS A study of this kind would be impossible without the assistance and advice of a large number of individuals. Inasmuch as the state of Chiapas is relatively undeveloped, travel through many of the areas is dependent upon the hospitality and friendliness of the inhabitants. It is quite impossible to acknowledge the scores of considerate people who have aided us in so many ways. Worthy of particular thanks are the following: the Bulnes family of the Finca El Real, Sr. Palomeque of Tapachula, and Sr. Jose Trinidad Patino Navarrete who was temporarily in charge of the Finca Guatimoc. These people gave us the hospitality of the fincas for considerable periods of time. Mr. and Mrs. Frans Blom of Las Casas, Sr. Eizi Matuda of Mexico City, and Dr. T. C. Schneirla of the American Museum of Natural History gave us invaluable advice on collecting localities. Dr. Eduardo Noguera, Director of Prehispanic Monuments, made possible our stay at the Ruins of Palenque during the sum- 1953 OPILIONID FAUNA OF MEXICO 3 mer of 1949. During the month of July, 1950, Dr. Lewis J. Stannard was a welcome field companion. Mention must also be made of the constant aid and helpful criticism of Dr. W. J. Gertsch of the American Museum of Natural History. During the summer of 1950, the largest number of localities was visited under the sponsorship of a grant from the Penrose Fund of the American Philosophical Society. The stay at Palenque was sponsored by a special grant from the Purdue Research Foundation. We wish to express our sincere appreciation to both of these organizations. HISTORICAL FACTORS THAT MAY INFLUENCE DISTRIBUTION OF OPILIONIDS IN CHIAPAS The state of Chiapas, with an area of 27,200 square miles, varies greatly in physiographic features. It varies in altitude from sea level to a high point of 13,090 feet on the volcanic peak of Tacanat. Schuchert (1935) recognizes five physiographic units. These are: 1. The Low Pacific Coastal Plain consisting of Pleistocene and Recent deposits on the south shore. 2. Just north of this, the Sierra Madre Mountain Province. This province has an altitude averaging about 3000 feet in eastern Oaxaca and 9750 feet at the Guatemalan border. The southern slope has ancient granite and gneiss plus young eruptives. The northern slope has materials dating from late Paleozoic times. 3. North of this range is the Central Depression with an altitude varying from 1625 feet to 2275 feet. Bounded by mountains on each side, it is a block-faulted area. 4. North of the Central Depression is the Mesa Central, or Cretaceous Plateau, of San Cristobal which averages about 7500 feet in altitude. 5. Lastly there is the area of high rainfall and rich vegetation, the Northern or Cenozoic Mountain Province. The highest part of this province is from 4900 to 5850 feet. It descends step-like into the coastal plains of Tabasco. These provinces have come into existence chiefly through fault- ing. This is particularly noticeable in the Central Depression and the Mesa Central. The historical geology of Chiapas according to Schuchert (1935) briefly is as follows: 4 AMERICAN MUSEUM NOVITATES NO. 1610 An ancient geanticline, the protaxis of Central America, existed before Permian time. Towards the close of the Permian, the first fold-mountain making occurred. Until the early Cretaceous this nucleus continued when the seas spread over much of Mexico, leaving only the southern and southwestern portions dry. Fold- mountain making began again in the late Mesozoic and continued into early Eocene times. These movements thrust against the older southward formations of the nucleus, with the result that much of Oaxaca, Chiapas, and Guatemala became dry land. Late in the Eocene, the seas of the north again covered much of southern Mexico. The greatest elevations occurred during the late Pliocene, raising western Chiapas about 3500 feet, eastern Chiapas about 7000 feet, the central portion about 1950 feet, and the northern 7800 feet. The extent of elevation of the Sierra Madre at this time is not known. It appears from available information that the exact geologic age of all regions has as yet not been accurately determined. The indications are, however, that the low Pacific Coastland and the Gulf Lowlands were covered by the sea during periods of the Pleistocene and have emerged in relatively recent times (Quaternary). The Sierra Madre probably arose during the late Pliocene, with the volcanoes being of Pleistocene or Recent origin. Much of the Central Depression and Mesa Central can be con- sidered Upper Cretaceous, while the northern or Cenozoic Moun- tain Province is in part Tertiary, with the Gulf Lowlands dating from the Quaternary. During the course of this investigation, we were able to collect in all of the physiographic zones. Only one, the Central Depres- sion, was too dry when visited to yield any animals. The localities visited in the different zones were as follows: 1. Low Pacific Coastal Plain. Finca Santa Martha near HuehuetAn, Puerto Madero, and Tapachula. 2. Sierra Madre Mountain Province. Cacaohuatan, Uni6n Juarez, Finca Guatimoc. 3. Central Depression. Tuxtla Gutierrez, Chiapa de Corzo. 4. Mesa Central. San Cristobal Las Casas, Tenejapa, Cruz Quemada, ComitAn. 5. Northern, or Cenozoic, Mountain Province. Ocosingo, Finca El Real, Finca Monte Libano, Palenque, Teapa, Pichucalco, and Villa Hermosa. Numerous localities in the adjoining states of Campeche, Oax- aca, and Veracruz have also been visited. Much of the in- 1953 OPILIONID FAUNA OF MEXICO 5 formation so obtained has been used for the interpretation of the distribution and relationship of the various species ECOLOGICAL FACTORS THAT MAY AFFECT DISTRIBUTION OF OPILIONIDS Although the distribution of any animal group may be funda- mentally due to geological and physiographical influences, ecological factors also play an important role. In Chiapas the inter- action of these two influences is clearly illustrated. The principal groups that are present are due to historic factors, but their present-day distribution is determined by local ecological conditions. These local conditions may be as recent as last year's clearing of a forest. In a country so highly dissected as Chiapas, many local variants develop. In general, however, it is possible to identify various definite zones within each of the physiographic areas as recognized by Schuchert. 1. The Low

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