thiolliericrinid crinoids from the lower cretaceous of crimea

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— 631 —В - basal plate (the basal) ;Be - centrodorsal basis ;IIBr - secondbrachial (the plates of the secondbra chial series) ;С - stem joint (columnal) ;Cd - centrodorsal plate (the centrodorsal) ;Co - opening of the axial canal ;Ct - cavity of the calyx ;F - fossa on the centrodorsal ;Fi - interradial furrow in the theca cavity ;FI - lateral fossa ;Fm - marginal fossa ;Fr - radial furrow in the theca cavity ;R - radial plate (the radial) ;Rf - radial facet (the upper face of the radial) ;Ri - intermediate ridge ;Rm - marginal ridge ;Rs - external (free) face of the radial ;Rt - transversal (fulcral) ridge ;Sc - cirrus socket ;SI - left second brachial series ;Sm - marginal crenulation ;Sr - right secondbrachial series ;St - crenularium on the transversal (fulcral) ridge ;The measurements used for the description of spe -cies are (see fig. 2) :A f - angle of the inclination of a radial facet ;Bf - width of a radial facet ;Dc - diameter of a centrodorsal basis ;Dt - diameter of a theca ;He - height of a centrodorsal ;Hr - height of the external (free) radial face ;Ht - height of a theca ;Lf - length of a radial facet ;In some cases, to show the morphological featuresmore clearly, the relative parameters are used :Hr : H t - relative height of the external radial face ;Bf : Lf - relative width of the radial facet.4 — TAXONOMIC DESCRIPTIONClass CrinoideaSubclass Articulata Miller, 1821Order COM ATULIDA A .H . Clark, 1908Family Thiolliericrinidae A .H . Cla r k, 1908Type genus :Thiolliericrinus Et a llo n, 1859.Diagnosis :The theca consists of five radiais, five basais (ofteninvisible outside) and one centrodorsal. The firstbrachial is axillary. Immovable junctions are absentin the arms. The branching of the arms is isotomous(sometimes slightly asymmetrical) and not less thanthrice-repeated. Secondbrachials and tertibrachialsare closed, forming a massive tube. The centrodorsalwith or without cirri. The short stem consists of severalcolumnals. The columnal articula are bifascial(synartrial). The attachment disk has a shape of thecone-like knot.Generic features : Exposure of the generic featuresfor the family meets a considerable difficulty. Thefact is that the representatives of this group, just asmost reef-dwellers, have many variations concealingFig. 2 —Main elements of the Thiolliericrinidae skeleton.A - calyx without cirrus sockets on the centrodorsal (side view) ; В - calyx with fossae and cirrus sockets on the centrodorsal (sideview) ; С - separate radial (view from above) ; D - calyx (view from below) ; E - calyx (view from above) ; F - relative partial reconstructionof the skeleton ; G - cruciate columnal (the arrows mark the direction of the fulcral ridge) ; H - parallel columnal (thearrows as on fig. G) ; I - articulum of a columnal.For designations see the text.Éléments principaux du squelette des Thiolliericrinidae.A - coupe dorsale sans surface d’articulation des cirres sur la centrodorsale (vue latérale) ; В - coupe dorsale avec les fossettes et lessurfaces d’articulation des cirres sur la centrodorsale (vue latérale) ; С - radiale isolée (vue en dessus) ; D - coupe dorsale (vue endessous) ; E - coupe dorsale (vue en dessus) ; F - reconstruction partielle conventionnelle du squelette ; G - columnale à crêtes fulcralescroisées (les flèches marquent la direction de la crête fulcrale) ; H - columnale à crêtes fulcrales parallèles (les flèches commela fig. G) ; I - facette articulaire d’un article.Explications dans le texte.
— 632 —not only specific but also generic limits. However, onecan determine the main generic features, being guidedDy phylogenetical considerations (see below), as follows:1 - The degree of the development of cirrus socketson a centrodorsal, namely : a - they are functionaland are distributed regularly (Solonaerium) or irregularly(Thiolliericrinus) ; b - there are no true sockets,but structureless fossae scattered over the centrodorsal(Burdigalocrinus) or remained only on thesuture between radiais and the centrodorsal (Umbocrinus,partly Loriolicrinus) ; the calyx is deprived ofany traces of cirri (Conoideocrinus, Heberticrinus) ;2 - The degree of the development of radiais,namely : radiais have a high external face and nearlyhorizontal muscular facets (Solonaerium, Burdigalocrinus,Conoideocrinus, Loriolicrinus, partly Thiolliericrinus); radiais are low, their facets are stronglyinclined outside and bordered close to a centrodorsal(Heberticrinus, Umbocrinus, partly Thiolliericrinus) ;3 - The degree of the development of basais,namely : a - basais are large (Solonaerium, Conoideocrinus,partly Thiolliericrinus and Burdigalocrinus) ;b - basais are small, hardly visible or not visible on theexternal calyx surface (Loriolicrinus, Umbocrinusand Heberticrinus).Other features (size ratio of the radial ring and thecentro-dorsal, the stem facet construction etc.) arepresent in the generic diagnoses given below besidesthe enumerated characteristics. These features, however,have no importance. And what is more, theabove mentioned generic features, can neither separately,determine a genus in the family Thiolliericrinidae.However, they show quite clearly the differencesbetween the genera being presented as a table (table2).Intraspecific variation. The form and relative sizeof the centrodorsal plate are the most variable featuresof Thiolliericrinidae. These variations are markedmainly in cirriless forms. For example Heberticrinusheberti may have the centrodorsal height less thanthat of the radial ring, equal to it or several timesgreater. Besides, the place of the greatest diameter issituated in the base of the low centrodorsal or in theupper part of high one, directly below the radial ring.The centrodorsal diameter can be equal to that ofradial ring among specimens with an identical size butthe first diameter can exceed almost two times thesecond one. Heberticrinus heberti has a commonlyround centrodorsal outline. However, specimens withan oval centrodorsal can be found, lenghtening ofwhich coincides with a direction of the fulcral ridgeon its basis. Sometimes the rounded-pentangular outlineis marked in large specimens.The stem facet can be greatly deepened on the lowercentrodorsal face of H. heberti (this is typical forrather low calyxes), can be flat (in low calyxes) or canproject as an acute ridge (in high calyxes). The centrodorsalbasis is mostly horizontal but it can be placedobliquely with the calyx axis. Because of this, the centrodorsalcan be considerably higher on one side thanon another.The radial facets of H. heberti more often adjoindirectly the centrodorsal. But in some calyxes, onecan see a narrow strip of the free radial surface dividingthe facet from the centrodorsal. The width ofthis strip can varied, though in a small degree, even ondifferent sides of the same specimen.The size of basal plates is also subjected to a variation.Being concealed under the radiais, they neverhave an equal length. Some basais, even in one calyx,hardly reach a half of the distance from the centre tothe outer edge while the others can appear upon theexternal calyx surface. These variations are marked inHeberticrinus heberti and Burdigalocrinus maximus.The basais of Umbocrinus umbonatus are quite visible,as a rule, on the calyx surface. However, the caseswere marked, when some basais of individual specimensare concealed under the radiais.The sculpture of the external calyx surface is therelatively insignificantly variable feature. For example,the calyxes of Thiolliericrinus belbekensis arecovered with small granules and the radiais of T. torosusbear big knobs. However, a weak sculpture in theform of small irregular granules is observed in somespecimens of Umbocrinus umbonatus, for which thesmooth calyxes are typical.One must emphasize the difference between theintraspecific and the intrapopulational variations.The specimens which belong to the same species arerelatively poorly differ in each of the local population.At the same time, one can hardly found theforms which would be united under the same specificname even the two bioherms are placed side by side.Seven genera : Solonaerium Éta llo n, 1862 emend.Rasm ussen, 1978, Thiolliericrinus Éta llo n, 1859,Burdigalocrinus Jaekel, 1918, Loriolicrinus Jaekel,1918, Conoideocrinus nov. gen., Heberticrinus nov.
Page 1 and 2: THIOLLIERICRINID CRINOIDS FROM THE
Page 3 and 4: TABLE OF CONTENTS1 - Introduction..
Page 5 and 6: — 628 —Name of s p ecies L o ca
Page 7: 630 —
Page 11 and 12: — 634 —Fig. 3 — Calyxes and c
Page 13 and 14: — 636 —Fig. 4A scheme of the di
Page 15 and 16: — 638 —Thiolliericrinus elongat
Page 17 and 18: — 640 —Fig. 7 — Calyxes and c
Page 19 and 20: — 642 —cavity. The primaxillary
Page 21 and 22: — 644 —D e s c r i p t i o n :T
Page 23 and 24: — 646 —T y p e s p e c ie s :Ge
Page 25 and 26: — 648 —Fig. 12 — Calyxes and
Page 27 and 28: — 650 —T y p e l e v e l :Upper
Page 29 and 30: — 652 —5 — RECONSTRUCTION OF
Page 31 and 32: — 654 —SIS rllAxsurface (Loriol
Page 33 and 34: primaxillaries but are asymmetrical
Page 35 and 36: — 658 —At the same time, all th
Page 37 and 38: — 660 —AcknowledgementsThis art
Page 39 and 40: ROMAN F. (1897) - Recherches strati
Page 41 and 42: PLATE
Page 43: Geobiosn° 20, fasc. 5Pl. 1V.G. Kli

thiolliericrinid crinoids from the lower cretaceous of crimea

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