New and poorly known Valanginian ammonites from South-West ...

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noEvgenij J. BARABOSHKIN & Irina A. MIKHAILOVAless tuberculated venter, presence of bipartite dichotomicribs and a more evolute adult stage. It is veryprobable that it is the ancestor of Pseudacanthodiscus.Pseudacanthodiscus is also similar to the Upper BerriasianTranscaspiites LUPPOV, 1985 (in BOODANOVA et al.,1985), which differs by the absence of the single ribs incycles, absence of constrictions and less developed umbilicaltubercles.Distribution: Thurmanniceras pertransiens Zone ofSouth-West Crimea, Lower Valanginian of Bulgaria,the Himalayas and (?) Madagascar.PseudacanthodiscusBARABOSHKIN, 1997PI. 3, Figs. 7a-bcrymicus1937 - Acanlhodiscus Euthvmi: TZANKOV, p. 61. pi. IV,fig. 2.1967 - Acanlhodiscus twanensis: DiMlTROVA, p, 125,pi. LXI, fig. 2.1997a - Pseudacanthodiscus crymicus: BARABOSHKIN,p. 118, pi. 38, fig. la-b"; 2a-b.2000 - Pseudacanthodiscus crymicus: BARABOSHKIN,p. 105, pi. 5. fig. 8a-b,"9a-b.Material: Holotype MSU 94/8, a nearly complete phragmoconeand four large fragments from the Lower Valanginian,bed Kp29/54, condensed Thurmanniceras pertransiensZone of the Sbrosovy Log Ravine, BeibekRiver, South-West Crimea.Description: Large, moderately evolute shells with octagonalwhorl-section, high on the outer whorls. Umbilicusrelatively broad, shallow with steep to vertical umbilicalwall.The cyclic sculpture is formed by alternating simple,bifurcate and/or intercalated ribs and constriclions.Fine simple ribs are significantly curved in the directionof the aperture. Bipartite and intercalated ribs arethickened and branched in the upper third of the whorlheight. Branches are short, directed forward. A largetubercle appears at the point of branching (intercalation)and on the umbilical shoulder. All ribs terminateby small flattened ventre-lateral tubercles, directed withan angle of 75-80° to the plane of the symmetry of theshell.The cycles of ribbing consist of one or two simpleribs (at the beginning of each cycle), 3-4 bipartiteand intercalated ribs on the early whorls (D=20-30mm)and separated by shallow and narrow constrictions.Cycles of the middle whorls (D=30-60 mm) consistoftwo pairs of bipartite and intercalated ribs and onesimple rib between them. Outer whorls (D>60-70mm)are ornamented by alternating simple and intercalatedribs, with loss of lateral tubercles.Measurements (see table).No. D H W Du Wu a. a 2P T94/13 21,5 25 7 20 65 8594/8 85 30 31 34 7,5 0 10-15 20 50 70-8094/12 46,5 42 8 20 50 8594/9 62,5 50 9 20 45 85Remarks: Pseudacanthodiscus crymicus differs from P.subradiatus (UMLIG, 1910) by the presence of simple ribsand broad constrictions on the middle whorls, and a verysmall angle between the ventro-lateral tubercles and theplane of symmetry of the shell.DIMITROVA (1967) has refigured Acamhodiscus euthymi(from TZANKOV, 1937) as Acanlhodiscus twanensis. Itis very similar to large fragments of Pseudacanthodiscuscrymicus. and differs from Acanlhodiscus by straightenedbi - tripartite ribs.Distribution: Lower Valanginian, Thurmanniceras pertransiensZone of South-West Crimea, Lower Valanginianof Bulgaria.DiscussionThe results of our investigation of the Valanginian ammonitesfrom Crimea permit a more complete knowledgeof the Neocomilidae. We agree with AGUIRRE-URRETA(1998, p. 40) that the replacement of Karakaschiceras(and therefore Bodrakieeras in the old sense) and Neohoplocerasin the Subfamily Endemoceratinae SCHINDE-WOLK, 1966, the endemic ammonites of the North Europe,is unjustified. The character of the development of themorphology and the suture line of the mentioned ammonitescompels us to include them into NeocomitinaeSALFELD. 1921. We combine the new results in the phylogeneticscheme (Figure 10), which is based on themorphological similarities and the available data on thesuture lines (Figure 11).The Neocomitidae belong in the Superfamily Perisphinctaceaeand they have a specific early branchingof the internal lobe (I) and displacement of Id branch tothe inner side. The sulural lobe is formed as a result ofseveral recurrent branching of the secondary lobes, whichare located on the umbilical seam before branching. It isknown in Balkiies BOGDANOVA & KVANTALJANI. 1983,Berriasella s. I. and for Thurmanniceras. Therefore, thenew elements of the suture line in the umbilical seamaspect of Perisphinctaceae are due to branching of thesuture lobe. This feature is also typical for the SuperfamiliesStephanocerataceae. Desmocerataceae and Hoplitaceae,which have five primary lobes. It allows themto be included the Suborder Perisphinctina (BEZNOSOV &MIKHAILOVA, 1983).The ammonites of the lineage Balkites -Luppovella
New and poorly known Valanginian ammonites from South-West Crimea 111(Planibulliceras) - L. (Neoluppovella) have equal externaland first lateral saddles with sharp reduction of thesuture line in the direction of the umbilical seam thatreflects the shape of the suture lobe symmetrically deepeningtowards the umbilical seam (Figure 11). Theumbilical lobe in Luppovella (Planibulliceras) and L.(Neoluppovella) becomes asymmetric and the first lateralsaddle becomes much narrower than the external saddle.Luppovella (Luppovella) is the latest representative ofthis lineage, having a very deep asymmetric umbilicallobe, which is somewhat similar to the neocomitinidKilianella and the berriasellinid Balkites (Figure II).The morphology of the ribbing is similar in this lineage,but has developed in two ways:1. Luppovella cycle of ribbing consisting of single, bifurcateand bipartite bidichotomic ribs. Cycles separatedfrom each other by constrictions, which becameshallower in the lineage. The other developed featureare the tubercles, which became sharper and appearontogenetically later in this lineage.2. Kilianella cycle of ribbing consisting of single, bifurcateand bipartite bidichotomic ribs. Cycles separatedfrom each other by constrictions deeper in the earlywhorls. Umbilical and lateral tubercles usually poorlydeveloped, but ventro-lateral tubercles of the terminalrib of the cycle are very high, well-developed as inNeolioploceras.Tn the ammonites in the lineage Berriasella s.l. - Thurmanniceras- Campylotoxia. the umbilical lobe is tripartite,nearly symmetrical (Figure II). It is deeper in Berriasellathan the ventral lobe in Thurmanniceras andCampylotoxia and the first lateral saddle is much narrowerthan the external saddle; both saddles or one ofthem become unequal. The Thurmanniceras cycles ofribbing, which is separated by weak constrictions in theearliest whorls, are represented by sinuous single, bifurcate,3-4 - branch ribs and bidichotomic ribs. Umbilicaltubercles are strong, lateral tubercles are poorly developed.Ventrolateral tubercles arc orthogonal or suborthogonalto the plane of symmetry of the shell in Thurmanniceras,becoming subparallel in Campylotoxia.The ammonites in the branch Bodrakiceras- Busnardoitesdemonstrate a sharply asymmetric umbilical lobe.In Busnardoites this is associated with sharp reduction ofthe first lateral saddle in contrast to the external saddle.The ornamentation shows the disappearance of thelateral tubercles and increase of the umbilical tubercleswith the joining of the ribs in bunches as in Bodrakicerasconstrictum. Neolioploceras has a deep and narrow umbilicallobe which is weakly asymmetric in the ammonitesof the Bodrakiceras - Neohoploccras branch. Thesimilarity of the sculpture of both genera is discussedabove. The Neohoploccras cycle of ribbing notably differsfrom Bodrakiceras by having the complex bidichotomicterminal rib in each cycle with very high and strongtubercles in the ultimate branch and in general by coarserribbing and a very late effacemenl of the ornamentation.The branch Bodrakiceras - Karakaschiceras, in contrastto Neohoploccras. shows the reduction of lateral andventral tubercles and early smoolhing of the shell. Thesuture lines of the ammonites in the branch are similar,but the umbilical lobe (U) in Karakaschiceras is deeperthan the ventral lobe (V).The lineages Euthymiceras s.l. - Belbekiceras and Euthymicerass.l. - Distoloceras are characterised by thealmost symmetrical umbilical lobe (U), somewhat deeperthan the ventral one (V) and the suture lobe descends tothe umbilical seam. Cycles of ribbing in Belbekiceras areseparated by shallow constrictions and consist of simple,bi- or tripartite ribs, branching on the umbilical shoulderand in the upper third of the lateral sides, being differentfrom Euthymiceras s.L. which usually has intercalatedribs.AcknowledgementsWe arc grateful lo Hugh Owen for correction of the English of thispaper. We also (hank Hugh Owen, Jaap Klein and Philip Hoedemaekertor their discussion of the article. Jaap Klein also kindly helped us withliterature. The research was done in the frame of the IGCP projects 362and 381 and with the support of RBSF foundation (Project 98-05-64195).ReferencesAcktermann. E., 1932. Die Unterkreide im Ostteil des Preslav-Sattelysystems (Ostbulgarien). Beitrage zu ihrer Fauna, Stratigraphieund Lagerung. Siichsischen Akademie der Wissenschaften.Abhandhwgen der Mathematisch - Phvsischen Klasse, 41,S: 1-55.AGUtRRE-URRETA, MB., 1998. The ammonites Karakaschicerasand Neohoptoceras (Valanginian Neocomitidae) fromthe Neuquen Basin. West-Central Argentina. Journal of Paleontology.72, 1: 39-59.ArnAim, H„ Gidon, M. & THIEULOY, J.-P., 1981. LesCalcairesdu Fontanil des environs de Grenoble: leur place dans la stratigraphiedu Neocomten entre le Jura et le domaine vocontien.Eclogue Geologicae Helvetiae, 74. 1: 109-137.ATROPS, F. & REBOULET. S., 1993. Nouvelles donnees sur lazonation par ammonites du Valanginien superieur de 1'hypostratotyped'Angles (Alpes-de-Haute-Provence) et sur ses correlations.Comptes Rendus des Seances de I'Academie desSciences, (II), 317: 499-506.ATROPS. F. & REBOULET, S., 1995. Le Valanginien - Hauterivienbasal du bassin vocontien et de la bordure provencale:zonation et correlations. Comptes Rendus des Seances de I Academicdes Sciences, (Ila), 320: 985-992.
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