Il sito italiano sugli squali

Gli squali fossili


Tope shark
Upr Cretaceous - Recent
Ordine Famiglia
Carcharhiniformes COMPAGNO 1973 Triakidae GRAY 1851

Compagno (1984) includes a single extant species in the genus, Galeorhinus galeus (LINNAEUS, 1758). This is a moderately large (1.9 m) coastal-pelagic species of temperate continental and insular waters, ranging from bays to well out to sea (2 - 471 m). It is not present in the waters of the Western North Atlantic, but can be found in the South Atlantic and Eastern North Atlantic, Eastern Pacific and Australia. An opportunistic predator, it feeds on bony fish, cephalopods and miscellaneous invertebrates.

The dentition of this genus serves a clutching-cutting function and displays monognathic heterodonty. The crowns of these small teeth are compressed, triangular, and cuspidate - distally, there are numerous cusplets. In most tooth positions, the cusp is distally directed and the mesial cutting edge is convex, however, in anterior positions the cusp is rather upright and the mesial cutting may be straight or weakly concave. The labial face of the crown overhangs the root with a pronounced bulge. The root itself is broad, rather thin and flat, with a distinct nutrient groove.

Cappetta (1987) indicated the genus extends back to the Lower Turonian (Upper Cretaceous) and has been reported from Europe, Africa and North America. Some of the fossil species he included were: Galeorhinus cuvieri (AGASSIZ 1835) Lower Eocene of Italy (from well preserved skeletons), G. girardoti HERMAN 1977 Campanian and Maastrichtian of Belgium, G. minor (AGASSIZ 1843) Eocene of Europe and Morocco, G. minutissimus AARAMBOURG, 1952 Ypresian of Morocco, and G. ypresiensis CASIER 1946 Ypresian (Lower Eocene) Belgium.

Jordan & Beal (1913) described G. hannibaldi from Miocene and Pliocene sediments of Southern California. Ward & Wiest (1990) reported G. ypresiensis from Eocene of Maryland and Virginia. Welton & Farish (1993) reported G. girardoti teeth from Late Campanian - Maastrichtian exposures of Texas and Kent (1994) included it in the Chesapeake Bay Region. Teeth of this genus (G. aff galeus) have also been found in, but not formally reported from, the Oligocene of South Carolina (Chandler Bridge Formation) and Miocene and Lower Pliocene of North Carolina (Pungo River & Yorktown Formations).

Fig.1 - Galeorhinus Minor
4.7 x 6.0 mm
Ypresien (Eocene) -- Egem, Belgium 
From the collection of Marco Maas

Fig. 2 - Galeorhinus aff ypresiensis
3.5 x 4.0 mm
Nanjemoy Formation (Eocene), Virginia

Fig. 3 - Galeorhinus aff ypresiensis
3.8 x 5.7 mm
Nanjemoy Formation (Eocene), Virginia

Fig. 4 - Galeorhinus aff galeus
Lateral (left) 2.5, 3.6, 1.1 mm
Anterior (right) 2.7, 2.5, 1.0 mm
Yorktown Form. (Lwr Pliocene) NC

Fig. 5 - Comparison: Pachygaleus and Galeorhinus
A-I Pachygaleus lefevrei
J-M Galeorhinus aff ypresiensis
Nanjemoy Formation (Eocene), Virginia

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