Title: Variation within a large sample of<i>Ageleodus pectinatus</i>teeth (Chondrichthyes) from the Late devonian of Pennsylvania, U.S.A.
Abstract: The monospecific genus Ageleodus is a primitive chondrichthyan known exclusively from isolated Late Devonian and Carboniferous teeth. Due in part to the paucity of material, dental variation in Ageleo dus has not been fully recognized. This paper reports on a large new sample of Ageleodus pectinatus teeth (382) from the Catskill Formation (Late Devonian, late Famennian) at the Red Hill site in Clinton County, Pennsylvania, U.S.A. It represents the earliest recorded occurrence of the genus, and the largest catalogued sample of A. pectinatus from a single site. This sample allows for a thorough description of morpho logical variation within A. pectinatus teeth and gives occasion to a re view of the species' nomenclatural history. Nomenclatural History Agassiz (1838) described three species of Ctenoptychius (C. apicalis Agassiz, 1838; C. denticulatus Agassiz, 1838; and C. pectinatus Ag assiz, 1838) from isolated teeth. The type material of C. apicalis is from the Late Carboniferous (Westphalian) of Staffordshire, England. The type material of C. denticulatus and C. pectinatus is from the Burdie House Limestone (Early Carboniferous, Visean) of Scotland. Agassiz' original specimens are missing (Susan Turner, pers. comm.); the rele vant illustrations from Agassiz' (1838) plate are reproduced here in Figure 1. The original specimen of C. apicalis (Fig. 1A) has a short root and a raised, medially-acuminate crown with imbricated basal ridg es. Conical cusps divide the arching coronal margin. The prominent central cusp is bordered by three to four smaller cusps that decrease in size mesially and distally. (Note: because the arrangement of teeth with in the mouth of Ageleodus is unknown, in the present paper, the terms mesial and distal [sensu Peyer, 1968] refer to direction along the long horizontal axis or length of the tooth; lingual and labial refer to direction along the short axis or width of the tooth.) Two of the three original specimens of C. pectinatus (Fig. IB, C) exhibit a tall root punctured with nutritive foramina and a raised crown. The coronal margin is straight to slightly arched and is divided into nine or fewer cusps. The third specimen ascribed to C. pectinatus (Fig. ID) has a very different morphology and, under present consideration, does not belong to either Ctenoptychius or Ageleodus. This tooth has a raised crown and short root. The tightly arched coronal margin is divided into bulbous cusps. Cusp size decreases with proximity to the mesial and distal edges of the tooth. The original C denticulatus specimens (Fig. 1E-G) exhibit a tall root punctured with nutritive foramina and a raised crown. Four teen or more slender cusps of equal dimensions divide the coronal mar gin.
Publication Year: 2001
Publication Date: 2001-12-14
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 20
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