''Styloichthys'' (
Greek: ''stylo'' "pillar" and ''ichthys'' "fish"; "Pillar fish") is a
prehistoric
Prehistory, also known as pre-literary history, is the period of human history between the use of the first stone tools by hominins 3.3 million years ago and the beginning of recorded history with the invention of writing systems. The use of ...
sarcopterygian, lobe-finned fish which lived during the
Early Devonian (
Lochkovian) period of East
Yunnan,
South China
South China () is a geographical and cultural region that covers the southernmost part of China. Its precise meaning varies with context. A notable feature of South China in comparison to the rest of China is that most of its citizens are not n ...
.
Because it is clear that the jaws and skull of ''Styloichthys'' share many derived features with
coelacanthiformes
The coelacanths ( ) are fish belonging to the order Actinistia that includes two extant species in the genus ''Latimeria'': the West Indian Ocean coelacanth (''Latimeria chalumnae''), primarily found near the Comoro Islands off the east coast ...
[ ] it is placed as the oldest coelacanth.
Description
''Styloichthys'' is characterized by large pores on the
cosmine surface. These pores are often spoon-shaped and arranged in parallel grooves. There is a jagged margin between ethmosphenoid and otoccipital shields, an otoccipital with a wide flat surface carrying no vestibular
fontanelle
A fontanelle (or fontanel) (colloquially, soft spot) is an anatomical feature of the infant human skull comprising soft membranous gaps ( sutures) between the cranial bones that make up the calvaria of a fetus or an infant. Fontanelles allow f ...
.
The snout bends sharply downward and is slightly concave. The lower jaw has a ventrally protruding flange formed by prearticular and
meckelian bone.
Also characteristic of ''Styloichthys'' is the lyre-shaped trajectory of the supraorbital canal, a
fenestra ventralis, small internasal cavities, three
coronoids in the lower jaw, an eyestalk and a slender postorbital pila which connects the basipterygoid process and the side of the braincase wall.
Anatomical characteristics
Orbit region
The feature exceptional of ''Styloichthys'' is the recessed teardrop-shaped eyestalk area behind the optic canal.
The well defined natural margin of this unfinished area is indicated by surrounding periosteal lining which dips slightly into the unfinished recess. This corresponds to the eyestalk attachment reported in basal bony fishes.
A small depression serves for eye muscle attachment ventral to the eyestalk area.
Lower Jaw
Indication of three semilunar pockets along a shallow groove between the dentary and the prearticular shows that the lower jaw has three coronoids. It is unique in that it has a very large adductor fossa, a convex ventral flange, and a prearticular of minute denticles dorsally and undulating parallel ridges ventrally.
References
External links
''Styloichthys'' at Palaeos*
{{Taxonbar, from=Q15709160
Prehistoric animals of China
Prehistoric lobe-finned fish genera
Early Devonian fish
Devonian bony fish
Fossil taxa described in 2001