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Gli squali fossili

Scyliorhinus

BLAINVILLE 1816
Catshark
Lwr Cretaceous - Recent
Ordine Famiglia
Carcharhiniformi COMPAGNO 1973 Scyliorhinidae GILL 1862

Although represented in modern oceans by at least 15 genera and 89 species, this large family has few representatives in the waters of the Middle Atlantic States (1/Galeus, 1/Scyliorhinus and 1 or 2 Apristurus spp). Worldwide, the 13 species assigned to Scyliorhinus tend to regionally localized; Compagno (1984) notes none as being trans-hemispheric or trans-oceanic.

In instances where multiple species share a range, their bottom structure and/or depth preferences tend to be different. For example, two species are broadly distributed through the Eastern North Atlantic and Mediterranean. Both are deemed common in inshore & offshore waters (1 - 125 m) and have somewhat similar diets (crustaceans, mollusks, worms, cephalopods and fish). The smaller (to 100 cm), S. canicula (LINNAEUS, 1758), prefers mud, sand or gravel while the larger species (to 160 cm), S. stellaris (LINNAEUS, 1758), prefers a rough bottom. Scyliorhinus retifer (GARMAN, 1881), the Chain catshark inhabits the outer continental shelf & upper slope (to 450m) of the Western North Atlantic from New England to Florida and the Gulf of Mexico to Nicaragua.

Fossil specimens attributed to this genus have been reported from Europe, Africa, Asia and North America. Species listed by Cappetta (1987) include: Scyliorhinus. antiquus (AGASSIZ, 1843) Upper Cretaceous England, S. burnhamensis CAPPETTA 1976 Lower Eocene England, S. casieri CAPPETTA 1976 Lower Eocene England, S. dubius (WOODWARD 1889) Upper Cretaceous England, S. gilberti CASIER 1946 Lower-Upper Eocene Belgium & France, S. joleaudi CAPPETTA 1970 Middle Miocene and Middle Pliocene France. He goes on to note that the genus had been reported from the late Eocene of Georgia & Upr Cretaceous Texas.

Noubhani & Cappetta (1997) described three new species of catshark from the Paleogene of Morrocco, Scyliorhinus entomodon (Danian - Thanetian), S. ptychtus (Thanetian - Ypresian) and S. sulcidens (Thanetian). Teeth comparing well to S. ptychtus have been found in the Thanetian of Maryland and to S. entomodon in the Ypresian of Virginia. Kent (1994) attributes Scyliorhinus gilberti to the Paleocene and Eocene of the Chesapeake region and S. brivesi ARAMBOURG, 1952 to the Aquia (Paleocene) only. Case (1994) include S. gilberti in the Early Eocene fauna of Mississippi. Scyliorhinus teeth are also represented in the Miocene (Pungo River) and Pliocene (Yorktown) of North Carolina.

Cappetta (1987) describes the catshark dentition as a clutching-type, but goes on to note that dentitions of the living species are poorly known and cautions against the assumption that the paleontological usage of the term "Scyliorhinus" equates with the definition of extant genus of that name.

In general, Scyliorhinus teeth are small with a narrow cusp, one or more lateral cusplets, basal wrinkles on the lingual face and an incomplete cutting edge. The basal face of the root is flat and the lingual protuberance quite strong. Kent (1994) notes that the root has one or more pairs of margino-lingual foramina, and that S. gilberti typically has two cusplets (primary cusplet larger) and S. brivesi two or three with the primary and secondary of similar size.
 
Fig. 1 - Middle Eocene


Not only should Cappetta's warning about the genus be considered, but also the propensity to equate the North American teeth with previously described European species. In recent seas, most species are localized and European species are not reported from North American waters. 

 
Fig. 2
Scyliorhinus cf ptychtus
2.8 x 2.8 mm
Aquia Formation 
Thanetian (Late Paleocene) - Maryland
Indiscernible in the above image, the labial face has relatively strong but
short basal wrinkles which grow longer laterally, reaching a mid-crown
position. These folds can be seen on the lingual cusp-face as well, but 
they are much weaker. There is no discernable cutting edge.

 
Fig. 3
Scyliorhinus cf entomodon
3.4 x 1.8 x 2.0 mm
Nanjemoy Formation 
Ypresian (Lower Eocene) - Virginia

 
Fig. 4
Scyliorhinus "gilberti"
2.6 x 1.8 x 1.2 mm
Nanjemoy Formation 
Ypresian (Lower Eocene) - Virginia

 
Fig. 5 Scyliorhinus "gilberti"
Lateral 2.8 x 2.6 x 1.3 mm
Nanjemoy Formation Ypresian (Lower Eocene) - Virginia

 
Fig. 6
Scyliorhinus undesc
4.0 x 3.2 x 1.9 mm
Pungo River Formation
Miocene - North Carolina

 
Fig. 7
"Scyliorhinus" sp
2.3 x 1.5 x 1.0 mm
Round Mountain Silt Formation
Miocene - California 

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