While weathering and the complex dentition of most sharks often makes exact identification difficult, I may have found the following types of prehistoric shark teeth in our local creeks. They are listed in order of their occurrence, that is the most commonly found teeth are first, and so on. So far I have only found Miocene species, although others have found Eocene teeth.
Order Carcharhiniformes (Requiem or Grey Sharks)
This family of sharks are the most diverse and numerous modern group, as well as our most common fossil shark find.
Negaprion brevirostris or N. eurybathrondon (Lemon Shark) teeth are 1/8" to
1" long. Lots of these guys are found, the cusps are smooth but have serrations
on the shoulders and a weak nutrient groove on the roots.
Carcharhinus species are abundant, but distinguishing individual species can be difficult. Serrations usually extend all around the cusp and shoulders and sizes range from 1/10" to 1" long with a deep nutrient groove.
Carcharhinus leucas (Bull Shark) is an extant species found worldwide
both now and in the fossil record. One of the largest grey sharks it has a
broad flat cusp with medim sized serrations.
Other species of this genus found here include C. egertoni is an extinct species with a broad distribution. The cusp is narrower and smooth with smaller serrations.
C. obscurus (Dusky Shark) is also a living species with teeth very similar to the Bull Shark.
C. priscus is another generic extinct species with larger serrations than C.egertoni.
C. falciformis (Silky Shark) is an extant species with a distinctive triangular cusp.
C. seali (Blackspot Shark) is a very rare extant species with teeth very similar to small tiger sharks.
C. maclotti (Hardnose Shark) are much like lemon shark teeth, but with very large cusplets on the shoulders.
C. albimarginatus, C. amboiensis, C. borneensis, C. brevipinna, C. frequens, C. gibessi,
C. isodon, C. limbatus, C. longimanus, C. perezei, C. porosus, C. plumbeus, C.signatus, C. sorrah and C. wheeleri fossil teeth have also been identified in this area.
Galeocerdo species (Tiger Sharks) are usually less than 1", though they do get larger, and usually several are found each trip.
G. aduncus is the generic extinct species having simple serrations on both
sides of a flat cusp. Most that I find fall into this category. Some now doubt
the validity of this species, but I prefer this to an unnamed species.
G. contortus is also extinct and are more rare, with very find serrations on along
a pointed, twisted cusp.
G. cuvier (extant tiger shark) is the modern species and very rare here. The
serrations are very complex with a very large main cusp.
The extinct species G. clarkensis, G. mayumbensis, G. triqueter and an unnamed species have also been reported here. Physogaleus species have been reported by others, and are very similar to Tiger shark teeth.
Rhizoprionodon (Sharp Nosed Sharks) species are rare in the fossil record,
though a common extant species exists. These are tiny, 1/8" long teeth with
an unusual curved cusp and small serrations on one shoulder. R. acutus,
R. laticaudus, R. fisheri have been found here by some.
Sphyrna (Hammerhead Sharks) species can be distinguished from others in
this family by the large lingual protrubance and thick triangular cusp with no
serrations. S. laevissima, S. lewini, S. zygaena and Eusphyra blochii have
been found by some in this area and are usually smaller than 1 inch.
Isogomphodon acuarius is a rare deep water extinct shark. It's teeth are usually 1/4" long with a needle like cusp.
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Fossil Teeth, Vertebrae and Coprolites of Neoselachians