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Gli squali fossili

Premontreia

CAPPETTA 1992
Extinct catshark genus
Early Paleocene - Early Eocene
Ordine Famiglia
Carcharhiniformes COMPAGNO 1973 Scyliorhinidae GILL 1862

When erecting this genus, Cappetta (1992) assigned it to a new sub-family - Premontreinae. In Noubhani & Cappetta (1997), the genus was redefined. Struggling through the French, these are Scyliorhinidae teeth with rather large cusps (to 6 mm in height). The lingual face is convex and smooth and the labial, barely overhanging the root, is less convex and has enameloid ridges (vertical folds) at its base. One or two pairs of lateral cusplets may be present. Two species are noted by the authors, Premontreia subulidens (ARAMBOURG, 1952) and a new species, P. peypouqueti. The former is reported from Danian through Lower Ypresian [Early Paleocene - Early Eocene] and the later from Thanetian [Late Paleocene] sediments of Morroco.

Teeth from this genus also appear in North American sediments, having been found by the author in the Aquia Formation [Paleocene] of Maryland and the Nanjemoy [Early Eocene] of Virginia. Collected specimens compare well to the description and illustrations provided for P. subulidens and are particularly common in the Nanjemoy. When collecting the later, these teeth can be readily overlooked because of their similarity to those of the ever abundant Abdounia. Under magnification however, the similarities disappear. The defining differences include:

  • 1) Enameloid folds on the labial face (usually present)
  • 2) Vertical orientation of the cusp relative to the basal face of the root
  • 3) Lingually oriented foramen in the nutrient groove
  • 4) A flaring of the root basally (both labially and lingually)
The illustrated specimen is from an anterior/anterio-lateral position. Lateral teeth have a distally directed cusp.
 
Fig. 1 - Premontreia subulidens
hgt = 4.3, wid = 4.1, dep = 1.9 mm
Nanjemoy Formation, Virginia

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