Fish book son indd

Sturgeons – contemporaries of dinosaurs
97
in the northern Caspian and stay on the ice until they are taught to swim and 
forage. The seals were intensively killed for their valuable fur. Until recently, 
they were under the threat of extinction. Now the number of seals is being 
restored.
The third group of species is the Mediterranean species that came (either 
independently or with the humans’ help) to the Caspian from the Black 
Sea. These are: two types of mollusks – Mytilaster and Abra; crustaceans – 
amphipods (small, side-swimming crayfi sh); shrimps, Atlantic crab from the 
Black Sea, and the following fi sh – golden mullet and litt le mullet from the 
gray mullet family, the pipefi sh and the Black Sea turbot.
Finally, the fourth group includes the freshwater fi sh species. Having 
entered the Caspian Sea, they turned into seawater or diadromous (migrating 
upstream) fi sh. This group also comprises typical freshwater fi sh that enters 
saline waters. These species include catfi sh, sea sander, and fi sh of the carp 
family – Caspian barbel, Asp Caspian and Caspian vimba.
This group also includes Russian and Persian sturgeon, beluga and starred 
sturgeon. It should be noted that the Caspian Sea contains approximately 80% 
of the world’s sturgeon populations. Caspian barbels (reaching 1m in length 
and 20 kg in weight) and vimba (50 m, 3 kg) are valuable commercial fi sh. 
They feed on benthic organisms – mollusks, larvae, crustaceans and small 
fi sh.
Sturgeons are undoubtedly the main treasure of the Caspian Sea. Our 
book is dedicated to them.

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G.M.Palatnikov,  R.U.Qasimov
98
CONTEMPORARIES OF DINOSAURS
Sturgeon-like  fi sh are the most ancient among the currently living 
vertebrates. Their ancestors swam in the seas as early as the Jurassic period. 
Their traces are found in the Cretaceous deposits. The most ancient of the 
known sturgeons is Chondrosteus of the early Jurassic period. Remains of 
this  fi sh demonstrate that sturgeons did not change for millions of years. 
Regardless of their ancient origin and primitive morphology, until recently 
sturgeons have occupied a vast habitat area covering almost the whole 
Northern hemisphere of the Earth.
Areas of sturgeon distribution

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Sturgeons – contemporaries of dinosaurs
99
Position of sturgeons in zootaxy: 
 Type:  
Chordata 
(Chordates)
 Sub-type:  
Vertebrata 
(Vertebrates)
 Group:  
Pices 
(Fish)
 Sub-group:  
Actytoperygii 
(Actinopterygian 
fi sh)
 Superorder: 
 Chondrostei (Cartilaginous ganoids).
 Order:  
Acipenseriformes 
(Sturgeon-like)
 Family:  
Acipenseridae 
(Sturgeons);
 Genuses: 
  Huso (Belugas) – 2 species; Acipenser (Sturgeons) – 
18 species; Scaphirhynchus (Shovelnose sturgeons) 
– 2 species; Pseudoscaphirhynchus (False shovelnose 
sturgeons) – 3 species.
 
Family of Copepoda: (Polyodontidae)
 Two 
species:  
Paddlefi sh (Polyodon spathula); Chinese paddlefi sh 
(Psephurus gladius).
STURGEON FAMILY (ACIPENSERIDAE)
Sturgeons are diadromous, fl uvial anadromous and freshwater fi sh; 
inhabit the waters of the Northern hemisphere – Europe, North Asia and 
North America. Four genera are distinguished: beluga, sturgeon, shovelnose 
and false shovelnose.
Sturgeon-like  fi shes have a number of features that are common with 
Head of sturgeon 
(ventral view)
those of cartilaginous fi shes, and they are slightly 
similar to squaloids in appearance.
Sturgeons have a long fusiform body covered with 
fi ve rows of bony scutes: one dorsal, two lateral, and two 
ventral rows. Scatt ered between the rows of scutes are 
small bony granules and plates. The snout is elongated, 
conical or spatulate. The mouth is located on the lower 
part of the head and is edged by fl eshy lips; some have 
a mouth that projects to the sides of the head. There 
are 4 barbels in a transverse row on the lower part of 
the snout. The mouth is protractile, toothless; however, 
juveniles do have weak teeth.

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G.M.Palatnikov,  R.U.Qasimov
100
The forward pectoral fi n ray is strongly hardened and turned into a 
spine. The dorsal fi n is set back. The swim bladder is usually well developed 
(some sturgeons, like shovelnoses, have a rudimentary swim bladder) and 
connected to the stomach or esophagus. The internal skeleton is cartilaginous, 
and the notochord, which is covered by a thick joined sheath, remains for the 
life of the fi sh. Vertebral centra do not develop, although lower and upper 
vertebral curves do exist.
As with sharks, the sturgeon’s caudal fi n is heterocercal.
The common feature that unites bony fi shes and sturgeons is the presence 
of dermal bones in the neurocranium, which is covered with fi ve rows of big 
plates (scutes). Sturgeons have a bony operculum and swim bladder, which 
is connected to the intestines.
Among other ray-fi nned  fi shes, sturgeons have the most archaic 
structural features, which are not observed in bony fi shes. The sturgeons’ 
axial skeleton is based on a permanent notochord, the internal skeleton 
is made of cartilage, the internal cranium to a great degree remains 
cartilaginous, and the tail fi n is heterocercal with large upper peduncle. 
The body has fi ve longitudinal bony scales - “scutes,” which are vestiges 
of denticles. As with cartilaginous fi shes, sturgeons retain a spiracle – a 
special aperture on the edge of the operculum, which leads to the branchial 
aperture. The heart has a conus arteriosus, and the intestine has a spiral 
valve – just like in squaloids.
Sturgeon family representative – Kaluga (
Huso dauricus
)
Based on these characteristics, some authors considered sturgeons to 
be a very primitive group, similar to cartilaginous fi sh. In other words, they 
thought that the sturgeons originated not from the ancestors common with 
bony fi sh, but from primitive cartilaginous fi sh, ancestors of squaloids.

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