Pycnodus jonesae Longbottom, 1984

Sarr, Raphaël, Hill, Robert V., Jenkins, Xavier A., Tapanila, Leif & O'Leary, Maureen A., 2024, A Composite Section of Fossiliferous Late Cretaceous- Early Paleogene Localities in Senegal and Preliminary Description of a New Late Maastrichtian Vertebrate Fossil Assemblage, American Museum Novitates 2024 (4013), pp. 1-32 : 22-24

Pycnodus jonesae Longbottom, 1984

Figure 12

REFERRED MATERIAL: SEN 056.

DESCRIPTION: The specimen is a partial left prearticular preserving a coronoid process and part of the lower dentition. The teeth have the bluish-white preservation elsewhere described for P. jonesae ( O’Leary et al., 2019) . The medial toothrow preserves three mediolaterally wide teeth with concave wear facets. The first lateral toothrow preserves 10 teeth, all wider than long. The tooth crowns of the medial and first lateral rows are similar in size; however, they become smaller anteriorly. The next lateral row preserves three rounded, buttonlike teeth.

DISCUSSION: Pycnodonts are an extinct clade of largely marine neopterygian fishes with deep, rounded bodies hypothesized to have inhabited ancient reefs and lagoons ( Kriwet and Schmitz, 2005). They existed from the Late Triassic through the Eocene and are known for their characteristic durophagous dentitions, which are relatively common elements of shallow marine Cretaceous through Paleogene deposits in West Africa localities in Mali ( Longbottom, 1984; Kriwet and Schmitz, 2005; O’Leary et al., 2019). The specimens recovered here represent only the second report of pycnodonts from Senegal ( Capasso, 2019). These individuals would have inhabited a paleoenvironment closer to the open ocean than their relatives in the Trans-Saharan Seaway of Mali.

Pycnodontidae gen. et sp. indet.

REFERRED MATERIAL: SEN 076, 077, 081. These specimens are figured as 2 D media on MorphoBank as follows, MorphoBank Project P4480: SEN 076 (M902030), SEN 077 (M902027, M902028), SEN 078 (M902029), SEN 081 (M901999).

DESCRIPTION: Isolated teeth.

DISCUSSION: These specimens have similarities to other pycnodonts but are too fragmentary to assign to species (images of them have therefore been included only in the supplementary online material at MorphoBank P4480).

SILURIFORMES Cuvier, 1817

Siluriformes indet.

Figure 9I, J

Two specimens compare closely with spines of Siluriformes. SEN 093 (fig. 9I) is the base of a dorsal spine, characterized by a flared proximal end and a triangular cross section. SEN 096 (fig. 9J) is likely the middle portion of a pectoral spine, missing both the base and tip and subject to some crushing. It bears several triangular denticles along the presumed cranial bor- der of the bone .

Osteichthyes indet.

Figure 9E–H, K–L

REFERRED MATERIAL: SEN 084, 085, 088, 097, 098, 101.

DESCRIPTION: Isolated sub-macroscopic osteichthyan elements and fragments, discovered as part of bioclastic matrix.

DISCUSSION: SEN 088 (fig. 9E) is one of numerous fish vertebrae preserved in the sample. This element is just over 1 mm in diameter, and preserves the centrum, notochordal canal, the base of the neural arch, and a ventral rib.

In addition to fish vertebrae, there are several fragmentary elements that we refer to Osteichthyes based on their resemblance to fish cranial elements. SEN 085 (fig. 9F) is a flat, roughly square element, with oblique ridgelike processes extending from two corners. Two foramina enter the bone surface and communicate with an expanded chamber between bony laminae. This may represent a partial skull element or vertebra. SEN 101 (fig. 9G) is likely a partial parasphenoid, preserving part of the ventral keel and one anterolateral process. SEN 084 (fig. 9H) is an indeterminate bone fragment that may also be a fish cranial element.

We tentatively interpret two additional bones as otoliths. SEN 097 (fig. 9K) is tetrahedral overall, with a deep excavation between three of the vertices. A shallow groove runs along one side of the element. SEN 098 (fig. 9L) is rounded, with a groove that nearly encircles the entire element. On one side of this groove, the element is smooth and hemispherical. On the other side, an orthogonal sulcus and two shallower, oblique sulci separate the other half of the bone symmetrically into four tubercles.

CROCODYLIFORMES Hay, 1930, sensu Benton and Clark, 1988

MESOEUCROCODYLIA Whetstone and Whybrow, 1983

Figures

FIGURE 12. Pycnodus jonesae (SEN 056) from the Late Maastrichtian Cap de Naze Formation discovered at the North Quarry of Poponguine. Left prearticular in occlusal view. Scale = 1 cm.