Schizorhiza Explained

Schizorhiza is an extinct genus of schizorhizid sclerorhynchoid that lived during the Late Cretaceous. It contains one valid species, Schizorhiza stromeri. It lived from the Campanian to Maastrichtian,^[1] and its fossils have been found in Africa, the Middle East, North America, and South America.^[2]

Taxonomy

Schizorhiza stromeri was named by Wilhelm Weiler in 1930 for rostral denticles from the Nubian Sandstone of Egypt. The species was named in honor of Ernst Stromer. A second species, S. weileri, was named by Giselda Serra in 1933 for rostral denticles from Libya. It is considered a junior synonym of S. stromeri.^[3]

Description

Schizorhiza is characterized by its robust rostrum with over 1,800 denticles arranged in dense batteries, which form a continuous cutting edge along each side.^[3] Each denticle was replaced by a series of smaller denticles nested inside its roots and new rows of denticles grew from the end of the rostrum.^[4] Among sclerorhynchoids, this denticle arrangement and replacement system is only found in Schizorhiza and its close relative Harranahynchus.^[5] The rostrum was likely used for swiping and slicing prey like sawfishes^[3] and has earned Schizorhiza the common name of "slasher ray".^[6]

Notes and References

1. Becker . Martin A. . Chamberlain Jr . John A. . Wolf . George E. . 2006 . Chondrichthyans from the Arkadelphia Formation (Upper Cretaceous: Upper Maasstrichtian) of Hot Spring County, Arkansas . Journal of Paleontology . 80 . 4 . 700–716. 10.1666/0022-3360(2006)80[700:CFTAFU]2.0.CO;2.
2. Book: Cappetta, H. . 2012 . Handbook of Paleoichthyology. Volume 3E. Chondrichthyes. Mesozoic and Cenozoic Elasmobranchii: Teeth. . Munich . Verlag Dr. Friedrich Pfeil . 978-3-89937-148-2.
3. Kirkland . J.I. . Aguillón-Martínez . M.C. . 2002 . Schizorhiza: a unique sawfish paradigm from the Difunta Group, Coahuila, Mexico . Revista Mexicana de Ciencias Geológicas . 19 . 1 . 16–24 .
4. Smith . M.M. . Riley . A. . Fraser . G.J. . Underwood . C. . Welten . M. . Kriwet . J. . Pfaff . C. . Johanson . Z. . 2015 . Early development of rostrum saw-teeth in a fossil ray tests classical theories of the evolution of vertebrate dentitions . Proceedings of the Royal Society B: Biological Sciences . 282 . 1816 . 20151628 . 10.1098/rspb.2015.1628 . free. 26423843 . 4614774 .
5. Book: Kaddumi, H.F. . 2009 . Fossils of the Harrana Fauna and the Adjacent Areas . Eternal River Museum of Natural History . 178–187 . A new genus and species of sawfishes (Chondrichthyes: Batoidea) from the late Maastrichtian sediments of Harrana.
6. Web site: Gibson . S.Z. . 2015-10-30 . The "slasher" ray: An extinct fish with a saw-like nose . 2023-03-20 . PLOS Paleo . https://web.archive.org/web/20151031113723/http://blogs.plos.org/paleocomm/2015/10/30/the-slasher-ray-an-extinct-fish-with-a-saw-like-nose/ . 2015-10-31 .