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Gli squali fossili

Xiphodolamia

LEIDY 1877
Extinct mackerel shark
Lower - Middle Eocene
Ordine Famiglia
Lamniformes BERG 1958 Lamnidae MÜLLER & HENLE 1838

The teeth of this genus represent a heterodont dentition in which the roots become more flattened, elongated and rectilinear distally, while the smooth cusps become more flattened and triangular. The genus has at times been placed in Hexanchiformes (Leriche 1905 & Casier 1958), Isuroidea (Glikman 1964) and Lamnidae (Cappetta 1987).

The roots of the anteriors and antero-laterals show short, but distinct, branching lobes. The cusp of the anterior teeth are mesio-distally compressed and bear cutting-edges on the labial and lingual faces. The cutting-edge of the antero-laterals (and laterals) runs along the mesial and distal margins of the cusp.

Lateral teeth are strongly compressed mesio-distally with a distally inclined and lingually directed cusp and short distal heel. The root has a flat basal margin and face, the latter bears a circular foramen.

Cappetta (1987) notes three species and attributes them to deep-water deposits. The type species, Xiphodolamia ensis LEIDY 1877 (Lower Eocene), is from New Jersey marls and has been found elsewhere in North America and the former Soviet Union. X. barbadica (CASIER 1958) has been reported from the Middle Eocene of the West Indies and X. eocaena (WOODWARD 1889) from the Lwr Eocene (Ypresian ) England & Denmark and the Mid Eocene (Lutetian) of Belgium. The genus has also been reported from the Middle Eocene of West Africa
 
Fig. 1 - Xiphodolamia ensis
Lateral -- height = 1.7, width = 1.4 cm
Woodstock Member, Nanjemoy Formation (Ypresian)
Charles Co., Maryland
from the collection of Bob Wiest
>Fig. 2 - Xiphodolamia ensis
Anterio-lateral (left) -- contact Potapaco Bed C & Woodstock
Posterio-lateral (right) -- Potapaco Bed C
Nanjemoy Formation (Ypresian), Popes Creek, Maryland
from the collection of Gary Grimsley

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