Material and Methods

The taxa used in this study are: Archanarcestes obesus (Erben, 1960) and Mimagoniatites fecundus Barrande, 1865, from the Mimagoniatitidae; Agoniatites vanuxemi (Hall, 1879) and Fidelites fidelis Barrande, 1865, from the Agoniatitidae; and Latanarcestes sp. from the Anarcestidae. Six of the specimens are from Morocco. The remaining specimen (A. vanuxemi) is from the Cherry Valley Limestone of New York State (see Clarke, 1899). Descriptions of Moroccan localities are given below. For a more detailed description of the geology and stratigraphy of these localities, see Becker and House (1994) and Klug (2000).

AMNH locality 3233: Archanarcestes obesus (AMNH 43374) from layer "4B" (Becker and House, 1994). Lower-Middle Devonian. East of Bou Tcharfine, near Erfoud, Morocco; latitude 31° 16' 46'' N, longitude 3° 53' 0.54'' W.

AMNH locality 3237: Archanarcestes obesus (AMNH 45370), Emsian, Devonian. Bou Tcharfine, near Erfoud, Morocco.

AMNH locality 3311: Mimagoniatites fecundus (AMNH 46645) and Latanarcestes sp. (AMNH 46646 and 50416). Emsian, Devonian. East of Bou Tcharfine, near Erfoud, Morocco; latitude 31° 22.51' N, longitude 4° 4.38' W.

AMNH locality 3312: Fidelites fidelis (AMNH 50417). Late Emsian, Devonian. Jebel Ouaoufilal, near Taouz, Taflalt; latitude 30° 55.93' N, longitude 4° 1.14' W.

Specimens were examined using the scanning electron microscope (SEM). Four of these specimens have been previously illustrated (Klofak et al., 1999); three specimens are studied for the first time. AMNH 45374 described in Klofak et al. (1999) is revised here as Archanarcestes obesus.

Ornament was examined to confirm previous findings and expand the database. In addition to qualitative observations, measurements were collected on the distance between lirae on both the ammonitella and postembryonic shell. Measurements were taken from SEM photographs using the Quartz PCI Imaging Management System. Measurements were taken from three positions on the shell, wherever possible: ventral, midflank, and dorsal (Fig. 2.5a). The ventral and dorsal measurements were not taken directly on the venter or dorsum, but as close as possible in lateral view. The midflank measurements were taken along a line on the middle part of the flank. This represents the point of maximum whorl width. Measurements began at the apex of the shell and extended to the aperture of the embryonic shell. "Distance 1" is the distance between the first and second lirae measured between the crests of successive lirae (Fig. 2.5b); "distance 2" is the distance between the crests of the second and third lirae, and so forth. Measurements began at the closest measurable lira starting at the apex. Postembryonic lirae are designated in the same manner with the first postembryonic lirae distance designated "distance 1."

Specimens used in this study are reposited in the American Museum of Natural History, New York, New York (AMNH), and the New York State Museum, Albany, New York (NYSM).

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