thiolliericrinid crinoids from the lower cretaceous of crimea

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— 655 —Fig. 16 — Reconstruction of the skeleton of some Thiolliericrinidae (x 1) : Thiolliericrinus (below from the left ; a part of the arms is removed),Heberticrinus (in the centre) and Burdigalocrinus (from the right ; traces of parasites settlings are shown on the centralradius).Reconstitution du squelette de quelques Thiolliericrinidae (x 1) : Thiolliericrinus (en bas à gauche ; une partie des bras est enlevée),Heberticrinus (au centre) et Burdigalocrinus (à droite ; les traces de l’action de parasites sont montrées sur le rayon central).
primaxillaries but are asymmetrical. Their innerupper facet is considerably greater than the outer one.The construction of tertibrachials is like that of thesecondbrachials. Only the wedge-shaped form ofseparate plates is more pronounced. Also the odd brachialshave their external surface like an obtuse horizontalridge. One failed to determine the number ofbrachials in the third arm series. The tertiaxillaries aresymmetrical having flattened lateral faces as before.The axillaries of the second and third orders have nopinnules. The tertibrachials have smooth external surfacewithout any dependence on the calyx ornamentation.The crown of Thiolliericrinidae was uniform on thewhole, differing only in details in different speciesand even genera. It formed, in the closed position, acontinuous tube at least up to the level of the tertiaxillaries(fig. 16). By that, relatively very small pinnuleswere enclosed into the crown and not visible from theoutside. One can say that the crown skeleton was atest being made of closely adjusted and firmly unitedbrachial plates. The Thiolliericrinidae crown resembled,in this respect, the crown of Triassic Encrinusliliiformis L a m a r c k but was considerably greater.6 — ONTOGENETIC VARIATIONS OF THE CALYXESAccording to available materials, the calyx ontogenycould be reconstructed for three Thiolliericrinidaespecies : Loriolicrinus asper, Umbocrinus umbonatusand Heberticrinus heberti. One fact attracts ourattention : in all three forms, in spite of their belongingto different genera, there are almost the samecalyxes in young specimens, namely : high-conical orcylindrical with high free radial surface. However,subsequently the development of the calyxes proceededby different ways in each of the three species.The radiais grew quicker than the centrodorsal in L.asper (fig. 17A). Therefore the centrodorsal of thisspecies remained low and its upper surface is convex.The young forms of U. umbonatus (fig. 17B) havestrongly pronounced though low basais and fullydeveloped fossae under radiais. Then the centrodorsaland the radiais grew at an about equal speed. Thereforethe upper centrodorsal surface is flat. Simultaneouslywith the preserving of the basais on the externalcalyx surface, the relative height of the free radialsurface considerably decreased. The sutural pores didnot disappear but even increased in number and size,so that they changed into irregular openingsFig. 17 — Schematic sections of some Thiolliericrinidae calyxesshowing the stages of the ontogenetic development (R -radial, В - basal, Cd, centrodorsal) : A - Loriolicrinus,В - Umbocrinus, С - Heberticrinus.Sections schématiques des coupes dorsales de quelquesThiolliericrinidae, montrant les stages du développementontogénétique.cdc
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 and 8: 630 —
Page 9 and 10: — 632 —not only specific but al
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: — 654 —SIS rllAxsurface (Loriol
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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