Styloichthys

Taxobox
name = "Styloichthyes"
fossil_range = Early Devonian


image_width = 250px
image_caption = line drawing of "Styloichthyes"
regnum = Animalia
phylum = Chordata
subphylum = Vertebrata
infraphylum = Gnathostomata
classis = Osteichthyes
subclassis = Sarcopterygii
ordo = Coelacanthiformes
genus = "Styloichthyes"
species = "S. changae"
binomial = "Styloichthyes changae"
binomial_authority = Zhu & Yu, 2001
range_

range_map_width = 250px
range_map_caption = "Styloichthyes" range (in blue)

"Styloichthyes" or "Styloichthys" (Greek: "stylo" "pillar" and "ichthyes" "fish"; "Pillar fish") is a prehistoric sarcopterygian, lobe-finned fish which lived during the Early Devonian (Lochkovian) period of East Yunnan, South China.

Because it is clear that the jaws and skull of "Styloichthys" share many derived features with coelacanthiformes [cite journal
last = Friedman
first = Matt
authorlink =
coauthors =
title = Styloichthys as the oldest coelacanth: implications for early osteichthyan interrelationships
journal = Journal of Systematic Paleontology
volume = 5
issue = 3
pages = pp. 289-343
publisher =
location =
date = 08/10/2007
url = http://home.uchicago.edu/~mattf/Friedman_2007a.pdf
doi =
id =
accessdate = 2007-12-28] it is placed as the oldest coelacanth.

Description

"Styloichthyes" is characterized by large pores on the cosmine surface. These pores are offen 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.

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 "Styloichthyes" 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 "Styloichthyes" 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

* [http://www.palaeos.com/Vertebrates/Units/140Sarcopterygii/140.400.html#Styloichthys "Styloichthys" at Palaeos]
* [http://npg.nature.com/nature/journal/v418/n6899/full/nature00871.html A primitive fish close to the common ancestor of tetrapods and lungfish]
* [http://www.cas.ac.cn/html/Dir/2002/08/16/4558.htm Chinese Academy of Sciences]