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An evaluation of the current use of the breast-shoulder apparatus characters in anurans
Abstract
Historically, it has been accepted that all the elements of the breast-shoulder apparatus (BSA) are homologous in anurans, that the arciferal condition is primitive and the firmisternal condition derived, and that arciferal and firmisternal conditions have evolved several times. However, some studies have suggested that not all BSA elements are homologous in anurans and that the firmisternal condition is primitive with respect to arciferal condition. Also, it has been argued that the existence of convergent arciferal and firmisternal conditions preclude us from using those conditions reliably. The developmental anatomy of the BSA elements in 19 species of anurans, 2 species of lizards, and 1 species of salamander was examined in order to answer four questions: (1) are all the ventral elements of the breast-shoulder apparatus (BSA) homologous in anurans? (2) is the arciferal condition primitive to the firmisternal condition in anurans? (3) is there a firmisternal taxon? (4) is there an arciferal taxon? To answer those questions a new method for testing homology is proposed. It is based on the use of developmental data combined with the principles of cladism and must be used as alternative to parsimony. It was concluded that: (1) all the ventral BSA elements in anurans are homologous, (2) all BSA elements (including prezonal and epicoracoidal horns) are present in most anuran species (although showing different shapes), (3) there is more than one kind of epicoracoid overlap (arcifery) in anurans; (4) there are no bases to consider the arciferal condition, such as occur in Bufo, Acris crepitans, and Spea bombifrons, primitive to fimisterny (on the contrary the data support its deriveness), (5) there are no bases to consider the firmisternal condition apomorphic within anurans, (6) the data do not support the existence of convergent firmisternal conditions in anurans (such as in Atelopus), (7) there is no support for the existence of a firmisternal taxon, and (8) a new BSA element (the intermediate element, IE) is described.
Subject Area
Zoology
Recommended Citation
Kaplan, Moises Daniel, "An evaluation of the current use of the breast-shoulder apparatus characters in anurans" (1993). ETD collection for University of Nebraska-Lincoln. AAI9406079.
https://digitalcommons.unl.edu/dissertations/AAI9406079