Cyrtogomphoceratidae

From Palaeos.org

Jump to: navigation, search
(changed to characters of the Cyrtogomphoceratidae,)
(added much to the page)
 
Line 1: Line 1:
-
The Middle Ordovician to Lower Devonian cyrtogomphoceratid lineage of discosorid cephalopods includes the paraphyletic Cyrtogomphoceratidae and later [[Phragmoceratidae]]. The Phragmoceratidae have strongly constricted shell apertures.
+
: Systematic Paleontology <br/>
 +
: Class: [[Cephalopoda]]<br/>
 +
: Subclass: [[Nautiloidea]] <br/>
 +
: Order: [[Discosorida]]<br/>
 +
: '''Family: Cyrtogomphoceratidae'''
-
'''Characters''' (from Teichert 1964): M [[Ordovician]] to L [[Silurian]] dominantly medium-size to large, compressed, endogastric, cyrtoconic, [[Discosorida]] with the siphuncle close to the ventral side. Siphuncle segments short, broadly expanded. Connecting rings thick, expanded at the adapical end into thick swollen bulletts that reinforce the septal openings.  
+
The Cyrtogomphoceratidae comprise Middle Ordovician to Lower Silurian endogastric [[Discosorida|discosorid]] cephalopods, derived from the [[Ruedemannoceratidae]], and which give rise to the Silurian and Lower Devonian [[Phragmoceratidae]].  
-
The Cyrogomphoceratidae differ from the later Phragmoceratidae in having simple, open, apertures and swollen bulletts, and from the coeval Westonoceratidae in being endogastric rather than exogastric.   
+
==Descriptive analysis==
 +
 
 +
Cyrtogomphoceratids have shells that are mostly of medium size to large with the siphuncle close to the ventral side, which is logitudinally concave. Siphuncle segments are short, broadly expanded with thick connecting rings that are adapicaly expanded into thick swollen bullettes that reinforce the septal openings.
 +
 
 +
The Cyrogomphoceratidae, which happen to be paraphyletic, differ from the later Phragmoceratidae in having simple, open, apertures and swollen bullettes, and from the coeval [[Westonoceratidae]] in being endogastric rather than exogastric
 +
 
 +
==Phylogeny==
 +
 
 +
The phylogeny of the Cyrtogomphoceraidae begins in the Middle Ordovician with ''Ultichoceras'', derived probably from ''Ruedemannoceras''. In turn ''Ulrichoceras'' gave rise to ''Strandoceras'', which give rise to both ''Kiaeroceras'' and ''Cyrtogomphoceras'', which gave rise to ''Landeroceras''.  ''Strandoceras'' is also the probable source for the Phrogmceratidae.  ''Strandoceras'' is from the middle and upper Ordovician as are ''Cyrogomphoceras'' and ''Landeroceras''. ''Kiaeroceras'' is from the Upper Ordovician. Uppermost is the Lower Silurian ''Kunglungenoceras'', derivation uncertain.
 +
 
 +
==Paleoecology==
 +
 
 +
Cyrtogomphoceratid species were, with little doubt, bottom crawlers that may have spent some time hovering close to the sea bottom.  They were active predators, but mot fast swimmers.  Orientation was vertical with the aperture face down and shell held above, curving to the rear.  The  endogastric form is conducive only to this orientation, shared by many of the earlier, Lower Ordovician, [[Piloceratidae]]. In contrast the contemporary Wetonoceratidae were most likely bottom scooters, with the aperture facing forward, shell extending behind.   
Line 81: Line 97:
'''Credits'''
'''Credits'''
-
[[User:Christopher|Christopher]] 23:19, 21 January 2011 (UTC)
+
Christopher 21 January 2011 <br/>
-
[[User:John M|John M]] Apr 26, 2012
+
[[User:John M|John M]] 26 Apr. 2012; 19 Jul 2014

Latest revision as of 14:13, 19 July 2014

Personal tools