Pucapampella is an Extinction genus of Chondrichthyes from the Middle Devonian of Bolivia and Peru. As currently defined it includes only the Type species species P. rodrigae, although it is possible several yet-unnamed species are represented under this name. Spine-like organs assigned to the genus Zamponiopteron may belong to Pucapampella, but the two are not known to be directly associated. Pucapampella is one of the earliest known cartilaginous fish, and is unique due to features of its skull and teeth.
Discovery and naming
Pucapampella rodrigae was described in 1986 by paleontologists
Philippe Janvier and Mario Suárez-Riglos, based on three isolated skull fragments discovered in Bolivia. These remains are preserved in
Concretion and were initially identified as being from the
Middle Devonian (
Givetian stage) Sica Sica Formation and Huamampampa Formation,
although they were not discovered
in situ and are now thought to have originated from the older Early Devonian (
Emsian stage) Belén Formation.
A number of additional isolated skull fragments and a relatively complete braincase have subsequently been identified from Bolivia, including material from the
Icla Formation.
Later fossils discovered in
Phosphate nodule from the Chagrapi Formation of the Department of Puno, Peru have also been assigned to
Pucamampella.
An articulated skull and jaws from the Emsian-stage
Gydo Formation of South Africa was described in 2001 and also tentatively assigned to the genus,
although this specimen has since been reassigned to
Gydoselache.
The genus name honors the village of Pucapampa where the holotype specimen originated, and the species name, P. rodrigae, honors Gabriela Rodrigo who discovered the specimen.
Description
Pucapampella rodrigae is known from fossils of the
Skull and
Jaw. Uniquely among cartilaginous fish,
Pucapampella's teeth were skeletally attached to the
Palatoquadrate (upper jaws) and Meckel's cartilages(lower jaws), rather than being attached by soft tissue like other members of the Class.
The known skeleton of adult
Pucapampella was covered in mineralized
Tessellation,
a distinctive feature of Chondrichthyes, but these structures were apparently absent in juveniles.
The cranium was divided into two unfused, transversely-aligned segments by a cranial fissure, another feature unique among cartilaginous fishes.
Isolated fragments of Postcranium cartilage are known from the same deposits as Pucapampella, although it is unclear if these belong to the same animal.
In life, Pucapampella likely possessed well-developed subcephalic (beneath the skull) muscles which functioned to join the two segments of its neurocranium, similar to those of Sarcopterygii, Bichir, and certain Cow shark sharks.
Classification
When first described,
Pucapampella was thought to be a possible member of the
Bradyodonti (an assemblage of early chimaera relatives).
The discovery of more complete fossils has led to
Pucapampella being considered a
Crown group cartilaginous fish, and potentially the
Sister group to all other members of the Class.
Features such as the divided cranium and associated subcephalic muscles are thought to be primitive traits among
Gnathostomata, which are retained in
Pucapampella but lost in other members of Chondrichthyes.
Below is a simplified
cladogram from Frey and coauthors (2020), whose
Phylogenetics recovered
Pucapampella and
Gydoselache outside crown-group Chondrichthyes.
While only
P. rodrigae has been named, it has been proposed that multiple species of
Pucapampella are actually known due to the differences between specimens.
Paleobiology
Researchers Alexander Kuznetsov and Nadezhda Kryukova have suggested the genus fed by using a "backwards-ripping" motion, where backwards movement of the body would be used to pull chunks of flesh from prey. This behavior is in contrast to most living sharks which tear off chunks of flesh with side-to-side motions of the head, but is similar to the feeding method of living Sharpnose sevengill sharks.
This behavior would be allowed by the musculature of the head.
Paleoecology
During the Emsian stage, Bolivia and Peru were part of the Malvinokaffric Realm; a region which existed during the
Late Silurian and Early Devonian, is characterized by a unique fauna, was made up of portions present-day
Antarctica,
South America, and
Africa, and which sat near the
South Pole. In contrast to other regions at that time
Placoderm were largely absent, with the exception of
Bolivosteus.
It is likely that the rocks containing
Pucapampella were deposited in anoxic, deep-water environments.
See also
-
List of prehistoric cartilaginous fish genera
