Osteology and Anuran Systematics: Intrapopulational Variation in Hyla Lanciformis

Trueb, L. (Museum of Natural History and Department of Systematics and Ecology, The University of Kansas, Lawrence, Kansas 66045) 1977. Osteology and anuran systematics: Intrapopulational variation in Hyla lanciformis. Syst. Zool. 26:165-184.-Although osteological features are utilized frequently in comprehensive systematic reviews of anuran taxa, no serious attempt has been made to quantify the data and assess its variation other than in a descriptive context. Such assessments first must be made at the population level; thus, 119 osteological measurements were madeon a series of adult males and females of the Neotropical frog Hyla lanciformis (Anura: Hylidae). The results of this study show that nearly 50% of these characters demonstrate relatively low levels of variation in both sexes within the population. This suggests that osteological features can be quantified, and selected characters can be utilized to generate an osteological profile of a taxon to be used in concert with other numerical data for subsequent analyses. [Osteology; intrapopulational variation; Anura; Hyla lanciformis.] To a great extent the history of anuran classification -represents a chronology of investigations of anuran osteology. In the earliest classification of anurans (Wagler, 1830; Dumeril and Bibron, 1841), frogs were divided into two groups depending upon the presence (Phaneroglossa) or absence (Aglossa) of a tongue. The utility of the latter classification and others which followed (e.g. Thomas, 1854; Bruch, 1863; L'Isle, 1877) based on pupil shape and amplectic type were not accepted widely once Cope (1864, 1865) defined arcifery and firmisterny and designated two primary anuran groups on the basis of apparent dichotomous pectoral girdle structure. Boulenger (1882) perpetuated Cope's designations by describing "series" (Arcifera and Firmisternia) within the order Anura. This classification prevailed until Noble (1922) established five suborders of anurans predicated on differences in thigh musculature and, principally, the structure of vertebral centra. Noble's conclusions largely stood unchallenged until recent reassessments by Griffiths (1963), Inger (1967), Kluge and Farris (1969), Starrett (1973), Sokol (1975), and Duellman (1975). A glance at more recent work at familial and generic levels (e.g. see Zweifel, 1956, on pelobatids; Lynch, 1971, on leptodactylids; Tihen, 1962, on bufonids; Duelhman, 1970, on hylids; Trueb, 1970, on hylids; Laurent, 1940, 1941 a and b, 1943, and 1944, on ranids and rhacophorids; Parker, 1934, on microhylids) demonstrates the pervasiveness of osteological criteria in studies of anuran relationships. Scarcely a species description exists which does not specify snout-vent length. Moreover, morphometric assessments of head width, and hind limb length are presented, usually, as a matter of standard procedure and frequently are expressed as proportions of the snout-vent length. Among other characters commonly encountered are the shape of the snout, various cranial features (e.g. condition of dermal bone and presence or absence of cranial elements and dentition), fusion of limb bones, development of prehallux and prepollex, and number of presacral vertebrae. It is patently obvious that these characters are osteological as are the "standard measurements" of head, body and limb dimensions. Another issue of paramount importance in understanding the relationships among modem anurans is the fossil record, the interpretation of which is contingent almost exclusively on osteological criteria. All too