Laboratory studies and field observations were correlated to compose a complete description of breeding behavior in the leopard frog. The significance of various calls and their relationship to the sexual cycle and quantitative details of egg-laying behavior in 41 ovipositions were determined. Investigation of the sensory basis of reproductive behavior revealed that sex discrimination, which occurs during amplexus, is based upon the fact that an ovulated female is much fatter than a male or a non-ovulated female, and that non-ovulated females and males emit a warning croak when they are clasped, whereas the ovulated female is silent. The oviposition reflexes of the female are elicited by the tactile stimulation associated with the male's sexual clasp. The ejaculatory pumps of the male occur in response to tactile stimuli resulting from the egg-laying movements of the female. Pseudo-oviposition (egg-laying reflexes) was induced in gravid, non-ovulated females following interperitoneal injection of physiological saline solution which increased the female's girth and prevented the utterance of the warning croak. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
To the extent now possible, I trace out what appear to be the adaptive changes involved in the origin of rodents. This requires, as a preliminary, a critical analysis of the existing evidence that bears on their phylogenetic relationship to other groups. Part of the paper provides such an analysis, from an unusual perspective. The evidence for a phylogenetic association of rodents and lagomorphs is weaker than is usually claimed but may nevertheless reflect reality. In particular, the precursors of rodents are not yet adequately identified. The initial adaptations of rodents were for the most part quite different from those of lagomorphs, despite their similar gnawing. There is evidence that the Myomorpha constitute the earliest diverging branch of extant rodents. Conapomorphy and spermativore are new terms.
Chronostratigraphy and biochronology are the prime conceptual methods for relating biologic events to the geologic time scale. Chronostratigraphy is the dominant method applied in the oceanographic-marine realm, and biochronology is the dominant method for the terrestrial realm. These concepts were conceived in the early half of the 20th century, and major advances in both occurred during the latter half of the 20th century. Historical development of both chronostratigaphy and biochronology is briefly reviewed, and it is concluded that the early definition and application of biochronology is tainted by reference to and inference from biostratigraphy. It is proposed that biochronology be redefined as the organization of geologic time according to the irreversible process of organic evolution, following the characterization and application by Berggren and Van Couvering (1978, G.V. Cohee, M.F. Glaessner, and H.D. Hedberg [editors], Contributions to the geologic time scale: 39-55. Tulsa, OK: American Association of Petroleum Geologists). The new term "chronostratigraphic marker" is proposed and defined as any chronologically significant event (biologic, isotopic, isotopic-ratio, or paleomagnetic), recorded in a stratigraphic sequence, that can be directly related to and/or tied to any other chronostratigraphic marker. According to definitions given herein, a biochronologic event can become a chronostratigraphic marker, but only when tied to a discrete stratigraphic sequence and related to other stratigraphic sequences and/or chronostratigraphic markers. The terms and concepts "datum event", "land mammal age", "stage of evolution", and "appearance event ordination" are discussed and defined. A datum event is defined as any chronostratigraphic marker. Land mammal ages, along with European Neogene and Paleogene mammal units, are considered biochronologic entities; they are defined as relatively short intervals of geologic time that can be recognized and distinguished from earlier and later such units (in a given region or province) by a characterizing assemblage of mammals. Stage of evolution is a very basic biochronologic concept defined as the chronologic ordering of faunal assemblages based on morphological (evolutionary) differences observed in members of a single, well-established phyletic lineage. Appearance event ordination is a new tool of biochronology. It is defined as ordering the appearance of fossil mammal genera by multivariate analysis, using overlapping (conjunctive) and nonoverlapping (disjunctive) range distributions in large sets of data.
Phylogenetic analyses based on morphological data support monophyly of Glires, but not a link between Glires and zalambdalestids. Glires are more closely related to several Tertiary taxa, including primates, leptictids, pseudictopids, anagalids, and macroscelideans. Phyloge- netically constrained distributions of Glires support the conventional view for a post K-T boundary radiation of modern orders of placental mammals and disagree with conclusions of some molecular studies that divergence of Rodentia and Lagomorpha at infraordinal, ordinal, and certain supraordinal levels occurred in the Cretaceous. Current hypotheses employed to explain the discrepancy between the fossil record and the molecular clock hypothesis are not supported by phylogenetic and distributional evidence of Glires. There is no compelling evi- dence that close relatives of Glires were present in the Cretaceous.
Reprint from the Bulletin of the American Museum of Natural History, vol. lxv. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy, in the Faculty of Pure Science, Columbia University.