Gli squali fossili
Lwr Cretaceous - Recent
|Carcharhiniformi COMPAGNO 1973
||Scyliorhinidae GILL 1862
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
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.
Scyliorhinus cf ptychtus
2.8 x 2.8 mm
Thanetian (Late Paleocene)
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.
Scyliorhinus cf entomodon
3.4 x 1.8 x 2.0 mm
Ypresian (Lower Eocene)
2.6 x 1.8 x 1.2 mm
Ypresian (Lower Eocene)
Fig. 5 Scyliorhinus
Lateral 2.8 x 2.6 x 1.3
Nanjemoy Formation Ypresian
(Lower Eocene) - Virginia
4.0 x 3.2 x 1.9 mm
Pungo River Formation
Miocene - North Carolina
2.3 x 1.5 x 1.0 mm
Round Mountain Silt Formation
Miocene - California