| | | |
| | | | | |
Tholaster sp., Maastrichtian, Byala Formation, Byala, Bulgaria
Фотография создана 23 июня 2013 года
Добавить в избранное
Если вы хотите оставить комментарий,
вам нужно зарегистрироваться (или авторизоваться, если вы уже зарегистрированы)
Комментарии:
<a href="http://ammonit.ru/foto/34384.htm#303592">http://ammonit.ru/foto/34384.htm#303592</a>
|
Добавить в избранное |
|
Guettaria:
Test strongly cordate in outline with deep frontal groove. Subconical in profile and flat-based.
Thick-shelled.
Apical disc subcentral with a gonopore in each genital plate and two or more gonopores in ocular plates II and IV.
Frontal groove weak adapically but becoming very deep by the ambitus and continuing to the peristome as a sharply defined channel.
Peristome circular and facing forwards into frontal groove.
Paired ambulacra sub-petaloid; pore-pairs in posterior column better developed than those in the anterior column.
Periproct posterior, with a bilobed subanal projection.
Plastron plating meridosternous - labral plate followed by single large and symmetrical sternal plate; episternals paired and almost symmetric. No rostral plate.
Plastron plating continuous in posterior interambulacrum, but disjunct in paired lateral interambulacra, with first interambulacral plate separated from succeeding interambulacral plates.
Ring of coarse primary tubercles in supra-ambital region around the most of the test. Otherwise tuberculation fine and uniform.
Marginal fasciole present.
|
комментарий 2 уровня |
Комментарий создан 19 августа 2017 года в 23:17:41 |
|
|
|
<a href="http://ammonit.ru/foto/34384.htm#303593">http://ammonit.ru/foto/34384.htm#303593</a>
|
Добавить в избранное |
|
Tholaster:
Test cordate, longer than wide with deep anterior sulcus. Lower surface apparently flat; upper surface low domal.
Apical disc subcentral with four gonopores.
Paired ambulacra non-petaloid; pore-pairs rudimentary. Ambulacral plates relatively tall over aboral surface.
Frontal groove present from apex; deepening towards ambitus and continuing adorally to peristome as sharply-defined groove.
Peristome small and oval, facing anteriorly into groove.
Plastron plating meridosternous - labral plate followed by single symmetrical sternal plate, subsequent plating biserial.
Periproct supramarginal on steeply sloping posterior face surface.
Enlarged primary tubercles prominent on outer column of interambulacral plates in interambs 2 and 3. Large primary tubercles also developed adapically in other interambulacral zones.
?No fascioles. |
комментарий 2 уровня |
Комментарий создан 19 августа 2017 года в 23:18:12 |
|
|
|