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ZONATION OF THE CRETACEOUS OF CENTRAL COLOMBIA BY AMMONITES 43 whorl is subcircular. The third whorl is higher than wide. The earliest ornament observed is on the second volu lion and consists of annular fine rounded ribs which are visible from near the umbilical margin, they then trend pr;>rsira· diate as a very elongated S on the convex·flank, and cross the venter unihterruptedly; they are as wide as the intercostal spaces though a cons· trictlon-like intercostal space can be observe on this specimen. The ribs rapidly become narrower than the intercostal spaces (adoral por tion of the third volution) and at the same tl l]le they broaden on venter; shortly after (H:7 mm) the ribs become prominent on the flanks; contemporaneously the ribs begin to inflate on the ad umbilical third of the flank and to con· tractact on the adventral third; this contraction is followed by the development of a slight de· pression of the ribs on their adoral .side along the median ventral line, this produces delicate to accentuated humps on both sides of venter; the ribs have not been observed to be interrup ted on venter. At this stage of growth the ribs are . prominent, separated by wider intercostal apaces and they are straight of feebly flexuous. . • B) Up to 41 mm D (Santa Ana A.P.G.). As in the preceding specimen, the successive whorls only cover the external third of the preceding whorl; the umbilical wall is inclined and evenly rounds into the flanks; the periventral rnaigiq is abruptly rounded and the venter is rounded to flattened. The . ornament consists of primary ribs which appear about the middle of the umbilical wall but may extend, on exterior of shell to the umbilical seam. The ribs describe a slightly adoral concavity in the umbilical region, then a con laxity on the adumbilical and middle thirds of th flank where they are flared, then they are febly concave adomlly or straight on the adventral third . of . the flank, there they are .flattened and contracted; the ribs cross the l't!.n ter straight, flat-topped and prominet; along . tbe periventral margin the ribs have delicate lvations. The ribs are now differentiated into cp,unary and secondary ribs, the former genera JI:y· flare on ftanks out to the involution line m :\Vhere .they are less prominent; the secon· g!!Y ribs anse imprecisely outside the umbilical j(,',; ::Sn:;;nrlnt f»1 111Jd generally do not flare out. t :!a f:lt:1Ve PMl&Q' or secondary. ribs occasiona· .t'Wl;lll· The intercostal spaces are almost , c . • -, I1S wide as the ribs. The periventral ,Iy.a,fions on the ribs attenuate towa..tl the 14.o. end of the conch at this diameter. The ;g ell8Jllber ccuJ?ies three four!bs (3/4) of . iila·'lution, on Its venter the ns broaden '"· "'frund . and th adventral elevations disap , . owever, particularly on the in tern a! mold. !l_dQ face of the ribs on venter show a ctetllctlon. .. _,:,;:· .. ; G DIA NOSIS. This species is characterized by: A) its moderately large size and evolution, B) the regular alternation of feebly flexuous, wen spaced, primary and secondary ribs on middle and late stages of growth, and C) the ;JrJ: ri:. ssing of ventral "ele· - - .-:"i"':.-""· Meuurcneru D Euw H w 0/EUW 0/H No.R % % Sta. Ana ·1 30 Sta. Ana · 2 Sta . .Alla ·3 Sta. Ana •4 26 10 11 8 38 43 20 Sta. Ana · r. 26 11 10? 8 44 40'1 21 Sta. Ana • 6 30 14 12 9 47 40 2& Sta. Ana · 7 36 167 1& 10 .42? 42 26 Sta. Ana · 8 29 12 12 9 41 41 22 Sta. Ana • 9 37 17 13 1 46 36 24 Sta. Ana ·10 437 19 17 12 44 39 20 Sta. Ana ·11 39 19 16 10 49- . 41 26? Sta. Ana ·12 38 20 15 11 63 39 21 Sta. Ana ·13 367 17 1& 10 47? 42 . 24 Sta. Ana ·1 4 48 24 18 12 50 38 .• 2& Sta. Ana ·1 5 36 16 13 10 46 37 24 Sta. Ana ·16 60 26 18 13 62 36 . 215 Sta. Ana ·17 417 19 16 12 46 36 26 Sta. Ana ·19 337 14 13 9 42 39 22? Sta. Ana ·20 267 117 11 ? ? 7 . 26? Sta. Ana •26 41 21 15 10 51 36 22 Sta. Ana ·27 36 16 13 9 43 · 37 21 Sta. Ana ·30 59 30 21 16 61. 35 28 Sta. Ana ·31 64 28 21 15 62 39 24 Sta. Ana ·34 407 18 16 10 45 40 26 Sta. Ana ·35 31 14 12 9 46 39 22? Sta. Ana ·36 37 17 14 11 46 38 26 Sta. Ana ·37 36? 18 13 10 46 37 23 Sta. Ana ·38 37 18? 14? 10 49 38 21? St.. Ana ·39 327 16 13 9 47 40 19 Sta. Ana -40 35 17 13 9 48 37 207 Sta. Ana ·42 49 24 21 11? 49 43 28 COMMENTS. Same as for the genus. OCCURRENCE. Socota Member. Upper ' Aptian. J!MmdYdJamit{lJIS joepecki.,n. sp • lil: 4, fig. 5. Holotype. U.C.M.P •• C -1325 (Dlustrated by Casey, 1965, p. 418, text-fig. 152). Hypotype.Sta. Ana 9 (U.N.C.M.H.N.C.P.lly.7) Only one specimen is available (Sta Ana A.P.G. 19). Very flat, slab·like sides, planar ven· ter and very wide, radial ribs which are like clove buds; ther are slightly but clearly flanged on the adumbihcal third of the Dank. On t.'t e In· temal mold the intercostal spaces are one and a half times as wide as the ribs; the ribs are very wide on venter and cross it l in early. luqndurhamicras_gj[_qldgj, n. sp. PI. 3, fig:-"!3. Holotype. Sta Ana A.P.G. N. 42. (U.N.C.M.N. C.P.Ht. 32) •
44 F. ETA YO · SERNA One large specimen is referred to this species. The early internal whorls are covered with fine rounded ribs, convex on the adumbllical third of the whorl ; some of them, especially those which begin at the umbilical wall are prominent and flaring (=primary ribs); the secondary ribs start at the periumbilical margin usua· lly in pails, they are thin. On the last preserved whorl the ribs are fine, particularly on the in· temal mold. The primary ribs describe an adoral concavity on the umbilical wall and part of the periumbilical third of the flank, then they des· cribe an adoral bow, sporadically very strong, approximately on the central third of the flank, on the remaining third they develop another adoral shallow concavity and the profile of the ribs is consequently biconcave; the ribs are slightly thicker but rounded on venter where they are feebly elevated. The whorl section is higher than wide, It has an inclined umbilical region which rounds into the flank; the periventral margins are rounded. The last whorl has 28 ribs on venter; the living chamber is preserved as half the length of the last whorl. DIAGNOSIS. This species is characterized by: A) the delicately humped periventral margin of the ribs is transient, B) the flexuous rib· bing starts early in the ontogeny, and C) the rib· bing is less prominent. Me&llll'emenu. D Euw H W D/EUW D/H No.R. Sta. Ana 42 49 24 21 11? 49 43 28 . COMMENTS. This species differs from Juizndurhamiceras juandurhami n. sp., because on the latter the whorl section is more contrac .ted adventrally, and its ribs have conspicuous periventral elevations throughout ontogeny. OCCURRENCE. Socota Member. Upper Aptian. This species is named in honor of Mr. Car· los Giraldo of the Instituto Nacional de Investi· gaciones <strong>Geolo</strong>gico-Mineras, Bogota. cG·"":If -!fPfii Acantho hoplites Sinzow, 1907, p.458. . 19;·\ TYPE SPECIES. Acanthohoplites aschiltaensis (Anthula), subsequent desig· nation, Spath, 1921. Acanthol!gp_lites boureti[grme. n. sp. Pl .5, fig. 2; Text-fig. 5U, 5V. Holotype. C-127 (U.N.C.M.H.N.C.P.Ht. N.33) Paratype. VL10·10 (U.N.C.M.H.N.C.P.Pt. N.35) "?1938 Acanthoplites bigoureti Seusnes, Riedel, p.45, p, J , _ . , g.7, pl.14, fig. 24. 19S8 Acrrfohbplites bigoureti sensu Riedel (non Seus.), Etayo-Sema, p.20, fig.3. 1968 Acanthohoplites bigouretii sensu Riedel (non Seusnes), Etayo-Sema, p. 28, tab.L i970 Acanthoh-(oplites) bigoureti, Wiedmann, p.484, ex review of Etayo-Semas's paper. Only half an individual is available. On the earliest observed whorl there appears to be bullae-like tubercles along the line of involution, however the preservation does not permit one to be sure of this, after these bullae there is a tract on which pleats rather than ribs are developed. At this stage of growth the whorl section is depressed; the umbilical wall is subvertical but there is no well defined umbilical rim. At a larger stage (on the penultimate whorl) the ribs differentiate. The prominent primary ribs begin at the umbilical seam, they trend across the umbilical wall and adumbilical half of the flank describing a slight adoral concavity; one or two intercalary ribs develop between the primary ribs, they attenuate before reaching the umbili· cal seam. On the last whorl the intercalary ribs are present in groups of two or three, of these ribs the adoral one sometimes inclines towards the immediate adoral primary rib as lf branching from it. The primary rib develops a prominent triangular area with a spine; from this tubercle the ribs bifurcate or trifurcate. The in tercostal spaces are slightly wider than the ribs when shell is preserved but they are one and a half times as wide as the ribs on the internal mold. The ribs themselves have steep sides and roun· ded top, they describe a wide concavity on the flank and project on venter where they are slightly wider and flat-topped, the latter .is. particularly conspicuous on the intemlll mold,> On the venter the ribs tend to be :equally developed but occasionally some are narrower. At the beginning of the last whorl the section is subcircular, at its adoral part it becomes ogival, slightly compressed ad orally. DIAGNOSIS. This species is characterized by: A) the accelerated strengthening of its oma· ment, especially the lateral tubercles, B) the constancy of the wide intercostal distance, C) the dominant flaring character of the ribs, and D) the ogival section of the whorl on ribs. MeaUrements D Euw H W D/Euw D{H No. R. •;, Ofo C-127 24 11 9 9 46 37 21(1/2) COMMENTS. The section of the young specimen described by Jacob as "Douuilleiceras bigoureti Seunes sp." (1905, p. 415, pl.3, fig. Sa, 6b) is transversely elongated, lenticular. The inner whorls of the Colombian specimen appears to have more ribs than the specimens refe· rred to Seunes' species and figured by Pervin· quiere (1907, p.195, pl.S, fig. 37, 38) both sha· re however a circular section (intercostal) of the whorl. c;'5eunes (1887' p.567) previously 'noticed> that in this group of taxa the young specimens · of related (?) species are similar, the species being differentiated .. only in the adult stages. Seunes' figured specimens are larger than my specimen, however, their primary ribs are out·
Page 1 and 2: Publicaciones Geolo_gicas Especiale
Page 3 and 4: PUBLICACIONES GEOLOGICAS ESPECIALES
Page 5 and 6: CONTENTS ABSTRACT . . . . .. . . .
Page 7 and 8: Pl ate 4. Plate 6. Plate 6. Plate 7
Page 9 and 10: 2 F. ETA YO· SERNA The materials t
Page 11 and 12: 4 F. ETA YO· SERNA PHYSICAL STRATI
Page 13 and 14: FIGLH 1\ 2 2AJ Vl:LLA DE LEIVA CD -
Page 15 and 16: 8 Gloriaceras paulinae n. sp. Zumpa
Page 17 and 18: 10 F. ETA YO -SERNA coarse grained
Page 19 and 20: 12 F. ETA YO · SERNA trated in sev
Page 21 and 22: 14 F. ETA YO · SERNA ated. In the
Page 23 and 24: 16 F. ETA YO · SERNA TABLE I ASSEM
Page 25 and 26: 18 F. ETA YO ·SERNA tion consisfli
Page 27 and 28: 20 F. ETA YO ·SERNA increasing ove
Page 29 and 30: 22 has a subelliptical to subcircul
Page 31 and 32: 24 F. ETAYO ·SERNA rounds abruptly
Page 33 and 34: 26 F. ETAYO · SERNA ffer, 1963, p.
Page 35 and 36: 28 F. ETA YO - SERNA this is partic
Page 37 and 38: 30 F. ETAYO ·SERNA and bifurcate;
Page 39 and 40: 32 F. ETA YO · SERNA thirds of the
Page 41 and 42: 34 F. ETA YO · SERNA Hypotype. (U.
Page 43 and 44: 36 F. ETA YO - SERN A tuberculation
Page 45 and 46: 38 F. ETAYO - SERNA they project sl
Page 47 and 48: 40 last whorl the ribs are inconspi
Page 49: 42 Hypacanthoplites dognaliciae n.
Page 53 and 54: 46 F. ETAYO - SERNA "Acanthoplites
Page 55 and 56: 48 F. ETA YO · ERNA These tubercle
Page 57 and 58: 50 .,CQ.IQmQ.ik.er::fJ§. W forg.ro
Page 59 and 60: 52 Among the subsequent flared ribs
Page 61 and 62: ZONATION OF THE CRETACEOUS OF CENTR
Page 65 and 66: zoNATION OF THE CRETACEOUS OF CENTR
Page 71 and 72: ? ? ZONATION OF THE CRETACEOUS OF C
Page 91 and 92: 86 F. ETA YO - SERNA rent localitie
Page 93 and 94: 88 The adapical end of this conch h
Page 95 and 96: 90 F. ETAYO · SERNA dies out near
Page 97 and 98: 92 OCCURRENCE. La Frontera Fonnatio
Page 99 and 100: 94 re is an asymmetrical sulcus bor
Page 101 and 102:
96 (1898, p. 198, figs. 23a,b,c), w
Page 103 and 104:
98 the flank and have a periventral
Page 105 and 106:
100 F. ETA YO - SERNA On the adapic
Page 107 and 108:
102 ventral third of the whorl side
Page 109 and 110:
104 but "Fundort: Von Stiibel im Be
Page 111 and 112:
106 F. ETA YO · SERNA En dos regio
Page 113 and 114:
108 In due regioni della Cordiglier
Page 115 and 116:
110 REFERENCES ANDERSON, F. M. 1938
Page 117 and 118:
112 -- 1963.- Atlas des fossiles ca
Page 119 and 120:
114 KARSTEN, H. 1858.- Vber die geo
Page 121 and 122:
116 Colon. Geol. min. Resourc., uol
Page 123 and 124:
118 F. ETA YO • SERNA WIEDMANN, J
Page 125:
120 A) B) C) D) E) F) G) H) I) L) M
Page 129:
124 F. ETA YO • SERNA A) B) C) D)
Page 133 and 134:
FIGURA 7 A Q 8 ) / ! E I c K FIGUR
Page 136 and 137:
132. A) B) C) D) E) F) G) H) I) J)
Page 138 and 139:
134 Scatter diagram of the distribu
Page 140 and 141:
136 Scatter diagram of the relation
Page 142 and 143:
Page 144 and 145:
140 F. ETA YO · SERNA Scatter diag
Page 146 and 147:
Page 148 and 149:
144 F, ETAYO ·SERNA Scatter diagra
Page 150 and 151:
146 F. ETA YO · SERNA FIGURE 16 Sc
Page 152 and 153:
148 F. ETA YO · SERNA Scatter diag
Page 154 and 155:
PLATES 1-15
Page 157:
154 F. ETA YO · SERNA Fig. 1) Chel
Page 161:
158 F. ETA YO · SERN A PLATE 4 Fig
Page 165:
162 Fig. 1) Vectisites (Zambranoite
Page 169:
166 F. ETA YO · SERNA Fig. 1) Eodo
Page 173:
170 Fig. 1) Carloscaceresiceras cac
Page 179:
176 Fig. 1) Fig. 2) Fig. 3) Fig. 4)
Page 183:
180 Fig.1) Codaziceras scheibei (Ri
Page 186 and 187:
184 Engonoceras, 74. duartci, n. sp
Page 188:
186 Tegoceras, 82. benavidescaceres
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Publicaciones Geolo_gicas Especiales Del lngeominas

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