Middle Ordovician – Silurian
Cyclonema is an extinct genus of faculatively mobile epifaunal coprophage-deposit feeders
Identification in Hand Sample:
- Turbiniform or trochiform with spiral ornamentation
- Rapidly increasing size from apex to aperture; few volutions
- Oblique aperture with reflected inner lip
- Short spire with ventricose whorls
Fossils of Ohio (1996):
- Transverse and spiral ornamentation present; Ranges from the Middle Ordovician to Silurian and is represented by several medium sized species in Ordovician rocks of Ohio.
Caster, Dalve & Pope (1961):
- In the Cincinnatian, only a few genera of snails are common. Strangely, the shells of certain genera, for example Cyclonema, are usually found complete; whereas only the internal molds of other genera, Lophospira, are commonly found. This undoubtedly reflects an original difference in the physical or chemical structure of the shell.
Treatise on Invertebrate Paleontology, Part I, Mollusca 1 (1960):
- Basically Turbiniform or trochiform but variously modified by stationary coprophagous habit; always with characteristically sharp spiral and finer collabral threads
- Shell turbinate, non-umbilicated, with short spire, composed of few more or less ventricose whorls. Aperture oblique with reflected inner lip, always excavated. Surface with spiral lines and small ridges crossed obliquely by sharp lines of growth.
Ulrich & Scofield (1897):
- Shell turbinate or conical, never thick, composed of few more or less ventricose whorls; no umbilicus; surface sculpture consisting of numerous revolving lines and small ridges crossed obliquely by sharp lines of growth; aperture oblique, varying from rounded to subquadrate; inner lip more or less thickened, reflected, always excavated. Types, C. bilix Conrad and C. mediale Ulrich.
- The principal characteristic of this genus is the excavation of the inner or columellar lip. This peculiarity distinguishes the genus at once from Gyronema which includes some otherwise not very different shells. In Strophostylus there is a fold on the inner lip, forming a similar excavation, but it is generally so much twisted that its upper end is not visible in a direct view of the mouth. As a rule also the inner lip is much thicker than in Cyclonema. It seems a little strange that the relations of Cyclonema and Strophostylus have not been recognized heretofore. They are certainly very closely related and in practice it is often difficult to distinguish them. But if we are correct in deriving Cyclonema from Gyronema then the two groups must have different roots. The oldest known shells (Stones River group) that are strictly referable to Cyclonema have relatively coarse revolving ridges. In our Strophostylus textilis, on the other hand, the revolving lines are very delicate. The difference is so marked that we cannot believe that Strophostylus came from the same immediate root as Cyclonema. In our opinion they represent two independent lines.
- The composition of the shell of Cyclonema must be different from that of the majority of Lower Silurian Gastropoda. On the hills about Cincinnati, where thousands of specimens have been collected, the test is preserved when all the other shells occur as casts of the interior only. Indeed, we have never seen a natural cast of Cyclonema. Another point worthy of notice is the extreme rarity of specimens retaining the apical nucleus. Out of considerably over one thousand good shells before us only six retain the apex entirely. In nearly all of the other cases the evidence at hand seems to show that these minute whorls were lost during the life of the shell, or, at any rate, before fossilization, while in four of the six specimens preserving them they were covered and protected by an encrusting bryozoan.
- Shells turbinate; thin; spire short, consisting of few volutions which increase rapidly from the apex; aperture large, rounded anteriorly, and somewhat flattened on the columellar side ; umbilicus none; surface strongly marked by spiral threadlike striae, which are cancellated by finer striae.
- The shells of this genus include forms which have been referred to Pleuromaria littorina but which have no slit or indentation in the outer lip, or band upon the volution. The surface is marked by elevated striae parallel to the direction of the volutions, and the spaces between these are marked by finer stria crossing the others obliquely; the latter, however are often obsolete.
- The Pleurotomaria bilix of CONRAD, may be regarded as the type of this genus.
Ordovician Cyclonema ni jamii ya wanyama wa mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea ya mimea. Caster, Dalve & Pope (1961): - Katika Cincinnati, ni jenasi chache tu za konokono ambazo ni za kawaida. Kwa kushangaza, makundi fulani ya wanyama, kama vile Cyclonema, hupatikana yakiwa kamili, ilhali aina nyingine za wanyama, kama vile Lophospira, hupatikana yakiwa na umbo la ndani tu. Bila shaka hilo laonyesha tofauti ya awali katika muundo wa kimwili au wa kemikali wa ganda hilo. "Treatise on Invertebrate Paleontology, Part I, Mollusca I (1960): ""Kimsingi Turbinate au trochiform lakini tofauti-tofauti iliyopita na kawaida ya kupumzika; daima na spiral ya kipekee na nyuzi ndogo za collabral - Shell turbinate, isiyo na umbilical, na spire fupi, iliyoundwa na whorls chache zaidi au chini ya ventricle.""" Aperture oblique na kutafakari mdomo wa ndani, daima kuchimbwa. Uso na mistari spiral na ridges ndogo kuvuka obliquely na mistari mkali wa ukuaji. Ulrich & Scofield (1897): - Shell turbinate au conical, kamwe nene, linaundwa na wachache zaidi au chini ventricose whorls; hakuna umbilicus; uso sanamu inayojumuisha mistari nyingi mzunguko na ridges ndogo kuvuka obliquely na mistari mkali ya ukuaji; aperture oblique, kutofautiana kutoka pande zote kwa subquadrate; mdomo wa ndani zaidi au chini thickened, kutafakari, daima kuchimbwa. Aina, C. bilix Conrad na C. mediale Ulrich. - Sifa kuu ya jenasi hii ni uchimbaji wa mdomo wa ndani au columellar. Kipengele hiki hutofautisha jenasi mara moja kutoka Gyronema ambayo inajumuisha baadhi ya shells vinginevyo si tofauti sana. Katika Strophostylus kuna fold juu ya mdomo wa ndani, kuunda kuchimba sawa, lakini kwa ujumla ni twisted sana kwamba mwisho wake wa juu si kuonekana katika mtazamo wa moja kwa moja wa kinywa. Kwa kawaida pia mdomo wa ndani ni mzito zaidi kuliko katika Cyclonema. Inaonekana kuwa ya ajabu kidogo kwamba uhusiano wa Cyclonema na Strophostylus haujatambuliwa hadi sasa. Wao ni hakika sana karibu kuhusiana na katika mazoezi ni mara nyingi ni vigumu kutofautisha yao. Lakini ikiwa tunapata Cyclonema kutoka kwa Gyronema basi makundi hayo mawili lazima yawe na mizizi tofauti. Makombora ya kale zaidi yanayojulikana (kikundi cha Mto Stones) ambayo yanahusiana kabisa na Cyclonema yana miamba inayozunguka yenye ukali. Kwa upande mwingine, katika Strophostylus textilis yetu, mistari inayozunguka-zunguka ni laini sana. Tofauti hiyo ni kubwa sana hivi kwamba hatuwezi kuamini kwamba Strophostylus alitoka kwenye mizizi ileile ya Cyclonema. Kwa maoni yetu wao kuwakilisha mistari miwili huru. - Muundo wa ganda la Cyclonema lazima uwe tofauti na ule wa wengi wa Lower Silurian Gastropoda. Katika milima ya Cincinnati, ambapo maelfu ya sampuli wamekusanywa, mtihani ni kuhifadhiwa wakati shells nyingine zote kutokea kama matoleo ya ndani tu. Kwa kweli, hatujawahi kuona mchoro wa asili wa Cyclonema. Jambo jingine linalostahili kuangaliwa ni kwamba ni nadra sana kupata spishi zilizo na kiini cha juu. Kati ya makombora zaidi ya elfu moja yaliyo bora mbele yetu ni sita tu yanayohifadhi kilele kikamilifu. Katika karibu visa vyote vingine, uthibitisho unaoonekana unaonyesha kwamba vifuniko hivi vidogo vilipotea wakati wa maisha ya ganda, au, kwa kiwango chochote, kabla ya fossilization, wakati katika nne kati ya sampuli sita zilizowahifadhi, zilikuwa zimefunikwa na kulindwa na bryozoa ya encrusting. - Shells turbinate; nyembamba; spire fupi, inayojumuisha volutions chache ambayo kuongezeka kwa haraka kutoka apex; aperture kubwa, pande zote mbele, na kiasi fulani flattened juu ya columellar upande; umbilicus hakuna; uso nguvu alama na spiral threadlike striae, ambayo ni kufuta na striae finer. - shells ya jenasi hii ni pamoja na aina ambayo wamekuwa inajulikana Pleuromaria littorina lakini ambayo hawana slit au indentation katika mdomo wa nje, au bendi juu ya volution. Uso ni alama na striae kuongezeka sambamba na mwelekeo wa volutions, na nafasi kati ya haya ni alama na stria finer kuvuka wengine obliquely; mwisho, hata hivyo, ni mara nyingi outdated. - Pleurotomaria bilix ya CONRAD, inaweza kuchukuliwa kama aina ya jenasi hii.