Progymnodon hilgendorfi Dames, 1883,

Ebersole, Jun A., Cicimurri, David J. & Stringer, Gary L., 2019, Taxonomy and biostratigraphy of the elasmobranchs and bony fishes (Chondrichthyes and Osteichthyes) of the lower-to-middle Eocene (Ypresian to Bartonian) Claiborne Group in Alabama, USA, inclu, European Journal of Taxonomy 585, pp. 1-274: 182-183

publication ID

publication LSID


persistent identifier

treatment provided by


scientific name

Progymnodon hilgendorfi Dames, 1883


Progymnodon hilgendorfi Dames, 1883 

Fig. 68View Fig

Progymnodon hilgendorfi Dames, 1883: 148  , pl. 3, fig. 13.

Diodon (? Chilomycterus) hilgendorfi – Weiler 1929: 29  , pls 6–7, 9, 13–14.

? Diodon  sp. – Thurmond & Jones 1981: 108, fig. 51.

Progymnodus cf. hilgendorfi – Suraru & Suraru 1987: 128  , fig. 1.

Chilomycterus hilgendorfi – Dica 2002: 40  , pl. 1, figs 1–2.

Material examined

UNITED STATES OF AMERICA – Alabama • 121 isolated teeth; Claiborne Group ; MSC 2396, ALMNH PV1993.2.456 (57 specimens), ALMNH PVPV 2005.6View Materials.438, MSC 37349.1 2, MSC 37398.1 2, MSC 37435View Materials, MSC 37440.1 44, MSC 37443, MSC 37450, MSC 37556, MSC 37602, MSC 37895, MSC 38494.1 5, MSC 38551.1 2, MSC 38842View Materials  .


Outer margin (the ‘beak’) composed of numerous stacked rows of very small (less than 1.0 mm) circular to wedge-shaped teeth. Premaxillary margin angular; dentary margin broadly convex. Triturating surface consisting of two stacks of subtriangular teeth; teeth separated from anterior margin by deep gap of bone. Individual teeth consist of thin enameloid crown, weakly convex; medial border (adjacent to tooth on other half of jaw plate) straight; anterior and posterior margins weakly convex, and the teeth have a sub-triangular outline in occlusal view.


We identified premaxillary and dentary elements belonging to the Diodontidae  based on the size and shape of the triturating teeth, the number of triturating teeth exposed at any one time through in vivo usage, and the nature of the anterior beak. Five fossil diodontid genera are considered valid, including Eodiodon  from the middle and late Eocene, Progymnodon  from the Paleocene to late Eocene, Oligodiodon  from the Oligocene and Miocene, Kyrtogymnodon  from the Pliocene, and Chilomycterus  and Diodon  from the Miocene to Recent (see Tavani 1955; Tyler 1980; Weems 1998; Schultz 2006; Ciobanu & Trif 2012). Tyler (1980) and Dica (2002) questioned the validity of Eodiodon  , with both authors citing that the lone diagnostic characteristic of this genus, the lack of teeth at the biting edge (the “beak”), could be attributed to wear and/or preservation. Diodontid tooth plates have been shown to be highly variable in terms of the shape of isolated triturating teeth and the number of teeth concurrently exposed (see Weems 1998: fig. 6a). Nevertheless, our Claiborne samples were assigned to Progymnodon  because the triturating teeth are separated from the beak by a bone gap, which is a diagnostic characteristic of this genus (see Ciobanu & Trif 2012). Furthermore, the tooth plates in our sample appear conspecific to those of Progymnodon hilgendorfi  as described by Dames (1883). Although Dica (2002) synonymized P. hilgendorfi  with Chilomycterus  , citing the gap between the beak and the triturating teeth as being characteristic of the latter genus, Ciobanu & Trif (2012) rejected this synonymy, citing the Miocene origins of Chilomycterus  .

Thurmond & Jones (1981: 108, fig. 51) reported and figured a specimen from the basal Gosport Sand at site ACl- 4 in Clarke County, AL that they assigned to “? Diodon  sp.” Our reexamination of this specimen ( ALMNH PV 2005.6.438) revealed that it instead belongs to P. hilgendorfi  .

Stratigraphic and geographic range in Alabama

The specimens in our sample were collected from the basal Gosport Sand at sites ACl-4 and AMo-4, and the Gosport Sand at site ACh-21. Middle Bartonian, Zone NP17.


Alabama Museum of Natural History










Tetraodontiformes (awaiting allocation)




Progymnodon hilgendorfi Dames, 1883

Ebersole, Jun A., Cicimurri, David J. & Stringer, Gary L. 2019

Progymnodon hilgendorfi

Dames W. 1883: 148

Diodon (? Chilomycterus) hilgendorfi – Weiler 1929: 29

Weiler W. 1929: 29


Thurmond J. T. & Jones D. E. 1981: 108

Progymnodus cf. hilgendorfi –

Suraru N. & Suraru M. 1987: 128

Chilomycterus hilgendorfi –

Dica E. P. 2002: 40