Polazzodus
Encyclopedia
Polazzodus is an extinct pycnodontid from the late Cretaceous
(early Santonian
) of the Polazzo locality of northeastern Italy
. The paleoenvironment of Polazzo was a large marine carbonate platform and shallow internal lagoons formed from rudist reef
s. P. coronatus is known from a large number of specimens, many of which were very well-preserved.
The new genus Polazzodus was erected based on a number of autapomorphies that distinguished it from similar pycnodontid
fish. These include a second dorsal ridge scale (from which the Latin species name, coronatus, is derived), presence of olfactory fenestra on premaxilla, posterodorsal process on cleithrum, and several others. The largest measured recovered specimen was 97 mm (3.8 in), and the smallest was 30 mm (1.2 in), which represented a subadult specimen. Polazzodus, being a low-bodied pycnodont, is most similar morphologically to Pycnodus
and Tergestrinia, though its body shape is more oval than these genera.
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
(early Santonian
Santonian
The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series. It spans the time between 85.8 ± 0.7 mya and 83.5 ± 0.7 mya...
) of the Polazzo locality of northeastern 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...
. The paleoenvironment of Polazzo was a large marine carbonate platform and shallow internal lagoons formed from rudist reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....
s. P. coronatus is known from a large number of specimens, many of which were very well-preserved.
The new genus Polazzodus was erected based on a number of autapomorphies that distinguished it from similar pycnodontid
Pycnodontiformes
Pycnodontiformes is an extinct order of bony fish. The group evolved during the Late Triassic and disappeared during the Eocene. The group has been found in rock formations in Africa, Asia, Europe, North and South America....
fish. These include a second dorsal ridge scale (from which the Latin species name, coronatus, is derived), presence of olfactory fenestra on premaxilla, posterodorsal process on cleithrum, and several others. The largest measured recovered specimen was 97 mm (3.8 in), and the smallest was 30 mm (1.2 in), which represented a subadult specimen. Polazzodus, being a low-bodied pycnodont, is most similar morphologically to Pycnodus
Pycnodus
Pycnodus is an extinct genus of ray-finned fish ranging from the Cretaceous to Eocene periods. As its name suggests, it is the type genus of Pycnodontiformes....
and Tergestrinia, though its body shape is more oval than these genera.