Galeocerdo alabamensis

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The extinct shark *Galeocerdo alabamensis* is a relative of the modern tiger shark, though its classification has shifted. Recent scientific work links it more closely to the prehistoric genus *Physogaleus* (tiger-like sharks) than to *Galeocerdo* (true tiger sharks). In 2003, it was placed in *Galeocerdo*, but by 2019, tooth shape—the primary source of information for this species—led researchers to argue it is morphologically closer to *Physogaleus*. Distinguishing between these two genera in extinct sharks from the Oligocene and Miocene is difficult due to a lack of clear paleobiological data. **Distribution** Referred to here as *P. alabamensis*, its fossils have been found in the southern United States, specifically Alabama, Arkansas, and Louisiana. It lived during the Eocene Epoch, a time when tiger sharks first appear in the fossil record. Many tiger shark species have since gone extinct, leaving *G. cuvier* as the only living one. The first recorded appearance of *P. alabamensis* dates between 41.3 and 38.0 million years ago, and its last between 37.2 and 33.9 million years ago. Its identification and habits are often confused with taxonomically similar sharks from the same period because knowledge is sparse and mostly limited to tooth fossils. **Taxonomy** Most existing knowledge of *P. alabamensis* comes from recovered teeth and fossils, with additional information inferred from sister species that also existed only in the Eocene. It is likely a predecessor to *G. aduncas*. Morphologically similar species include *P. contortus*, *G. casei*, *G. davisi*, *G. gajensis*, and *G. paulinoi*, which presumably occupied similar ecological niches. *P. contortus* and *G. aduncas* had overlapping distributions along the U.S. East Coast during the Miocene, much like *P. alabamensis*. Based on tooth characteristics, some researchers have proposed combining *P. alabamensis* with *G. argyptiacus*. **Diet and Tooth Fossil Shape** As a member of the family Carcharhiniformes, *P. alabamensis* was carnivorous. The modern tiger shark, *G. cuvier*, has larger, more robust teeth and a versatile diet ranging from squid to sea turtles. The smaller teeth of *P. alabamensis* and its Eocene relatives suggest a less varied diet, likely targeting smaller prey. The most morphologically similar teeth to *P.