Janassa sp.

Hodnett, John-Paul M., Toomey, Rickard, Olson, Rickard, Tweet, Justin S. & Santucci, Vincent L., 2023, Janassid petalodonts (Chondrichthyes, Petalodontiformes, Janassidae) from the middle Mississippian (Viséan) Ste. Genevieve Formation, Mammoth Cave National Park, Kentucky, USA, Historical Biology CLXVI (CLXVI), pp. 1-10 : 7-8

Janassa sp.

Referred specimens

MACA 62173, partial lateral tooth.

Locality and horizon

Mammoth Cave National Park, Kentucky, Joppa Member, Ste. Genevieve Formation.

Description

Apartial and worn lateral tooth that is 9-mm high and 6-mm wide as preserved ( Figure 6 ). The tooth is sigmoidal in mesiodistal profile. Crown is spatulate-like and relatively rounded and wide with minute longitudinal cristae seen on the lingual margin of the carina. The lingual heel is approximately as wide as the rest of the crown. The six lingual cristae are transversely horizontal and well-spaced apart. Asmall remanent of the labial base indicates it was narrow and angled approximately 90° from the crown. Alow labial ridge is also present.

Remarks

This partial tooth is identified as a janassid petalodont by its sigmoidal profile and small labial base that is set 90° from the crown. We referred this specimen to the genus Janassa by the presence of relatively wide spatulate-like crown and horizontally traverse cristae. Due to its worn preservation, we are unable to identify this specimen to species. As noted above, during the Middle to Late Mississippian only three species of Janassa are presently recognised. The type specimen to J. imbricata is a partial tooth lacking the crown, that is exposed lingually showing well-spaced but pronounced lingual cristae. This tooth is also proportionately more elongate in height and narrower than the Mammoth Cave specimen. In general, proportions of the Mammoth Cave specimens agrees with the morphology of J. clavata and J. clarki , both of which are relatively more mesiodistally broad than labiolingually elongated, with broad rounded spatulate cusps. Complicating comparison is the fact that all specimens of J. clavata are preserved in matrix with only the labial sides exposed, leaving the lingual morphology currently unknown. J. clarki is an isolated tooth with 12 lingual cristae ( Lund 1989). Until we can find more additional specimens of Janassa at Mammoth Cave National Park, it is best to leave this identification at the generic level.

Figures

Figure 6. MACA 62173, Janassa sp. from the Joppa Member of the Ste. Genevieve Formation at Mammoth Cave National Park, Kentucky. (a) lingual, (b) labial, (c) mesial views. Scale 5 mm.