Schizorhiza
Encyclopedia
Schizorhiza is a fossil genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of cartilaginous fish, containing a single accepted species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 Schizorhiza stromeri. Its fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

s are found in rocks dating from the Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...

 and Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...

 stages; it thus lived between about 71 and 65.5 million years ago. Its Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...

 suborder, the Sclerorhynchoidea, cannot be unequivocally assigned to the Rajiformes
Rajiformes
Rajiformes is one of the four orders of batoids, flattened cartilaginous fishes related to sharks.Rajiforms are distinguished by the presence of greatly enlarged pectoral fins, which reach as far forward as the sides of the head, with a generally flattened body. The undulatory pectoral fin motion...

 (skate and ray) or to the Pristiformes (sawfish) order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

. Due to its unique rostral
Rostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....

 teeth, Schizorhiza is placed in the monotypic subfamily Schizorhizinae. Like all Sclerorhynchoidea, it probably did not survive the K-Pg mass extinction; there are a few remains from the Paleogene
Paleogene
The Paleogene is a geologic period and system that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic Era...

 but these seem to have been rework
Rework
Rework is the term for the refinishing operation or repair of an electronic printed circuit board assembly. Mass processing techniques are not applicable to single device repair and/or replacement, so specialized techniques are required to replace defective components – most notably area array...

ed from Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...

 deposits.

Schizorhiza is unique among all "saw-snouted" Elasmobranchii
Elasmobranchii
Elasmobranchii is a subclass of Chondrichthyes or cartilaginous fish, that includes the sharks and the rays and skates .-Evolution:...

 in that its rostral teeth did not fall off as they are replaced. Rather, they remain in place, with the new teeth under them, until they are worn off. Thus, the rostrum's edge had a continuous serrated cover of tooth enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...

. Full-grown rostral teeth measured less than in other Sclerorhynchoidea, let alone sawfishes, at 1-2 cm tall and 4-8 mm wide. They had a small triangular or rhomboidal shape at the tip, with sharp cutting edges, and a long forked peduncle
Fish anatomy
Fish anatomy is primarily governed by the physical characteristics of water, which is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does.- Body :...

, each lobe of which divides into four lobelets proximally. The new teeth developed inside the peduncular fork; the scientific name Schizorhiza – meaning "split root" – refers to the shape of the rostral teeth. The oral
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....

 teeth were very small (about 1.5-2.5 mm high and 1-2 mm wide), with a large and recurved central point and keels at the side that formed tiny secondary points.

It lived in the Tethys Ocean
Tethys Ocean
The Tethys Ocean was an ocean that existed between the continents of Gondwana and Laurasia during the Mesozoic era before the opening of the Indian Ocean.-Modern theory:...

 between about 30° northern and southern latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...

, and apparently was a successful species that ranged widely. Its fossils have been found in northern and central Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, Iraq
Iraq
Iraq ; officially the Republic of Iraq is a country in Western Asia spanning most of the northwestern end of the Zagros mountain range, the eastern part of the Syrian Desert and the northern part of the Arabian Desert....

, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

, Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...

 (USA), Coahuila
Coahuila
Coahuila, formally Coahuila de Zaragoza , officially Estado Libre y Soberano de Coahuila de Zaragoza is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico...

 (Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

) and Bolivia
Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...

. As its rostrum seems to be well-adapted for slashing and of little use for digging, it is presumed that this species did not share the whip-like tail of the bottom-dwelling relative Sclerorhynchus
Sclerorhynchus
Sclerorhynchus is an extinct genus of primitive batoidean that lived in the Cretaceous. The namesake of the Mesozoic suborder Sclerorhynchoidea, it is not quite clear whether they were closer to the Rajiformes or to the Pristiformes . Its fossils have been found mainly around the Mediterranean...

, but apart from the peculiar rostrum must have looked not too different from one of the sawfishes of today, regardless of whether they were very close relatives or not. Its total length was about 1.5 meters.

Its habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...

 was apparently shallow or epicontinental seas, as evidenced by its associated fauna
Fauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...

, the cartilaginous fish Pseudocorax, Scapanorhynchus texanus
Scapanorhynchus
Scapanorhynchus is an extinct genus of shark from the Cretaceous era. Their extreme similarities to the living goblin shark, Mitsukurina owstoni, lead some experts to consider reclassifying it as Scapanorhynchus owstoni...

and Serratolamna serrata, and the molluscs Cymprimera, Ethmocardium, Eutrephoceras, Platyceramus vanuxemi
Platyceramus
Platyceramus was a genus of Cretaceous bivalve molluscs belonging to the extinct inoceramid lineage. It is sometimes classified as a subgenus of Inoceramus.The largest and best known species is P. platinus...

, Sphenodiscus
Sphenodiscus
Sphenodiscus is an extinct genus of acanthoceratacean ammonite. The genus has been found from many continents and is thought to have had a large global distribution during the Maastrichtian stage of the Late Cretaceous...

and Turritella vertibroides
Turritella
Turritella is a genus of medium-sized sea snails with an operculum, marine gastropod mollusks in the family Turritellidae. They have tightly coiled shells, whose overall shape is basically that of an elongated cone....

.

See also

  • Flora and fauna of the Maastrichtian stage
    Flora and fauna of the Maastrichtian stage
    This is an incomplete list that briefly describes vertebrates that were extant during the Maastrichtian, a stage of the Late Cretaceous Period which extended from 70.6 to 65.5 million years before present...

  • List of prehistoric cartilaginous fish (Chondrichthyes)
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