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Journal of Paleontology

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DIRECT EVIDENCE OF THE ROSTRAL ANATOMY OF THE AÏSTOPOD PHLEGETHONTIA, WITH A NEW CRANIAL RECONSTRUCTION

¹ Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Dr. NW, Calgary, Alberta, Canada T2N 4N1, <janders@ucalgary.ca>

The first 20% of the full text of this article appears below.

	INTRODUCTION

 
IN A series of recent papers, colleagues and I (Milner, 1994; Carroll, 1998; Anderson, 2002, 2003a, 2003b; Anderson et al., 2003) have revised Aïstopoda, a collection of elongate, limbless tetrapods from the Paleozoic of Euramerica. Aïstopods are part of a larger, monophyletic assemblage of tetrapods known as lepospondyls, which are proving to be critical to understanding the early evolution of amniotes and are possibly related to the origins of some, or all, modern amphibians (Carroll, 1995, 2000a, 2000b; Laurin and Reisz, 1997, 1999; Laurin, 1998; Anderson, 2001; Ruta et al., 2003; Vallin and Laurin, 2004).

Sound phylogenetic analysis depends upon careful descriptive anatomy, but when working with fossils one also has to contend with variation in the quality of preservation. Thus, in my revision of the genus Phlegethontia Cope, 1871 in these pages (Anderson, 2002) I was forced to extrapolate the shape of the nasal bone based upon the shape of surrounding cranial elements, because no specimen at my disposal permitted direct observation.

Subsequent to publication of this revision, I learned of a large collection of Mazon Creek nodules from Pit 11 in the invertebrate paleontology collection at the Royal Ontario Museum in Toronto. Pit 11 preserves specimens from both the mostly marine Essex and more terrestrial Braidwood faunas (Baird et al., 1985). Many of the nodules in this collection are unopened, and most that are opened and fossiliferous contain remains of invertebrates or plant material. A few, however, contain vertebrate remains, including a recently described enigmatic temnospondyl (Godfrey, 2003). One of the nodules contained the skull and anterior postcranial skeleton of a phlegethontiid aïstopod which, upon inspection, preserves the entire rostrum, including the rarely complete . . . [Full Text of this Article]