Previously, giant sharks had only been recovered from rock dating back 130 million years, during the age of the dinosaurs. The largest shark that ever lived, commonly called "Megalodon", is much younger, with an oldest occurrence at about 15 million years ago. This means the new fossils from Texas indicate giant sharks go much further back into the fossil record.
After the generous donation of these fossils and careful study with Dr. John Maisey of the American Museum of Natural History in New York, the team was able to estimate how big the entire sharks would have been by comparison with smaller and more complete fossils of closely related sharks. The results were very impressive.
The size range estimated for these two Texas 'supersharks' was between 18 and 26 feet in length (5.5 to 8 meters). The largest of these specimens was 25% bigger than today's largest predatory shark, the Great White. Although not nearly as large as Megalodon, which might have reached up to 67 feet in length (about 20 meters), the fossil sharks from Texas would have been by far the biggest sharks in the sea.
These fossil braincases may belong to an extinct species of shark called Glikmanius occidentalis, or they may represent a new and larger related species that is new to science. Closely related sharks are known from as far off as Scotland, showing this group of sharks was capable of dispersing across great distances.
Maisey, McKinzie, and Williams timed their research results very well, being able to present their Texas 'supershark' at the annual meeting for the Society of Vertebrate Paleontology in Dallas, Texas. According to Maisey, even 300 million years ago, "everything is bigger in Texas!"
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CORRESPONDING AUTHOR CONTACT INFORMATION
JOHN G. MAISEY
Division of Paleontology
American Museum of Natural History
New York, New York 10024-5192
OTHER EXPERT NOT DIRECTLY INVOLVED WITH THE STUDY
College of Science and Health
A PENNSYLVANIAN 'SUPERSHARK' FROM TEXAS
MAISEY, John G., American Museum of Natural History, New York, NY, USA
MCKINZIE, Mark, Dallas Paleontological Society, Grapevine, TX, USA
WILLIAMS, Robert R., Dallas Paleontological Society, Valley View, TX, USA
Parts of two gigantic chondrichthyan occipital regions are reported from the Finis Shale (Virgilian, Upper Pennsylvanian, ca. 300 Ma) of Jacksboro, Jack County, Texas. The specimens closely resemble the elongated occipital region observed in other Paleozoic 'ctenacanthiform' and xenacanth chondrichthyans, and are clearly different from the far shorter occipital regions of contemporaneous symmoriiform sharks. No xenacanth teeth or spines are known from the Finis Shale, but extremely large 'ctenacanthiform' teeth (referred to Glikmanius occidentalis) are known to occur at this locality, offering circumstantial support for identifying the 'Texas supershark' as some kind of 'ctenacanthiform', although its true identity will emerge only when other specimens are found in direct association with teeth and/or fin spines. Nevertheless, based on this preliminary identification, and assuming that the original proportions of these specimens were close to those of more complete 'ctenacanthiform' braincases (e.g., Ctenacanthus concinnus, Tamiobatis vetustus, 'Tamiobatis' sp., Cladodoides wildungensis), we estimate that the length of the largest braincase probably exceeded 80 cm.
An estimate of the overall length of the 'Texas supershark' was made by comparing cranial and body lengths in two reasonably complete 'ctenacanthiform' body fossils: Goodrichthys eskdalensis, from the Lower Carboniferous of Glencartholm, Scotland, and an undescribed Pennsylvanian 'ctenacanth' from Kinney Quarry, New Mexico. In both these forms, the total body length was approximately ten times the cranial length. If the 'Texas supershark' was similarly proportioned, the largest specimen represents an individual whose overall length probably exceeded 8 m (i.e., about 25% larger than the modern great white shark and considerably larger than Goodrichthys and the Kinney shark, both of which were approximately 2.5 m long). While this is only half the conservative estimated length of the Neogene lamniform 'megalodon', the late Pennsylvanian 'Texas supershark' is nevertheless the largest Paleozoic chondrichthyan whose dimensions have been established empirically rather than by guesswork (as, for example, in Edestus giganteus). Furthermore, these findings suggest that large (ca. 8 m) predatory sharks appeared much earlier than previously supposed (the next oldest is the Cretaceous lamniform Otodus obliquus).