|Description: Three different species of porbeagle shark, also known as the mackerel shark, occur at this locality.
Cretolamna appendiculata lata teeth possess several characteristics that distinguish it from other species. Their teeth have very broad, robust roots that are almost rectangular in shape and perpendicular to the main cusp. The root is also compressed and, when viewed from the side, is lacking a prominent medial protrusion. The triangular and smooth main cusps are accompanied by two large stocky and triangular shaped cusplets. The lateral and posterior teeth are similar to the anterior teeth except the main cusp is reduced with a slight curve towards the back of the jaw. Their teeth are usually 1 to 2 cm (about .5 to .75 in) long.
The root lobes of Archaeolamna kopingensis are more arched and pointed than that of Cretolamna. Also the medial protrusion is somewhat more prominent on these more rounded teeth. The main cusp is more pointed and less triangular than Cretolamna. The main cusps of anterior teeth are straight becoming more curved and smaller to the posterior of the jaw. The cusplets are more slender and in some teeth, may posses a smaller secondary set of cusplets. These teeth, like most porbeagle teeth, are smooth and lacking any substantive longituial striations. The teeth of A. kopingensis are usually 1 to 2 cm (about .5 to .75 in) long.
The presence of the other species of porbeagle, C. borodini, at Big Brook is reported from only a few sources, but the evedence would sugest that the idendification is correct. They are similar to that of A. kopingensis but the features are more pronounced. The root is highly curved and comprises little more than half the total length of the tooth. The medial protrusion is very porminent and has the characteristic pin sized nutrient foramen. The main cusp is more slender, slightly curved lingually and unlike other porbeagles, posses very fine plications of ruffles on the labial side of the main cusp along the root margin. The cusplets of this species are more slender, divergent, and can be unattached from the main cusp. The size of these teeth are the main difference with .5 to 1.3 cm (about .25 to .5 in) being the norm.
Commonality: The teeth of the porbeagle shark are very common at Big Brook except C. borodini, which is uncommon.
Similar fossils: The only confusion in the identification of the porbeagles would seem to be within the porbeagles themselves, but occasionally, a A. kopingensis tooth can be confused with a posterior goblin tooth. Attention to a few characteristics should clear up any problems. Goblin teeth have a deep nutrient groove on the medial portion of the root, unlike the porbeagle that only has a pin sized nutrient foramen and lacks a nutrient groove. Teeth of the goblin are generally larger.
Size: Both C. appendiculata and A. kopingensis ranged about 2 to 3 meters (About 7 to 10 ft) in length, while C. borodini was only 1 to 2 meters (about 3 to 7 ft) in length.
Notes: Interstingly, C. appendiculata is the oldest reported shark in the Late Cretaceous sediments of New Jersey. An Amateur paleontologist found a cast of a tooth in the upper part of the Rarities formation, the first marine transgression of the sea. C. appendiculata is also believed to be the ancestor of the great white lineage of sharks.
Modern porbeagles are open water sharks that feed on small to medium sized fish and squid. Their bodies are somewhat stocky in appearance and resemble their close cousins, the makos and the great whites. The lamnoid group of sharks was widespread worldwide during the Cretaceous and their descendents are still alive today.