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ZONATION OF THE CRETACEOUS OF CENTRAL COLOMBIA BY AMMONITES 23 tlated from Aconeceras nisus d'Orbigny (1841, p.184, pl. 55, Figs. 7, 8, 9; Sarasin 1893, p. 153, pl. 4-6, Fig. 9a, b, c, Text-Fig. 1, 2) irrespective of size, mainly by the more massive and rectan gular base of E/L in the Colombian species. On Sara&in's Figs. 2,3 (ib., p.153) and in d'Orbigny's Fig. 9 of plate 55, the io_temal branch of E/L is stronger than the exteni81 branch of the same saddle, but in the Colombian specimens the re· verse 1s true. On Aconeceros nisoides (Sarasin) [ 1893, i.155, pl.4-6, Figs. lOa, b,c, Text-Flg.3; Casey, 961. p. 125, pl.26; Figs. 3-5, Text-Fig. 41a-c], again the internal branch of E/L is the predo minant (see also Fig. 4le, p.127, Casey, op.cit.); the growth striae in the Colombian species are more acute than in the French species (see Casey op.cit., fig. 41c). The specimen figured by Somay (1955, p.l2, pl.l, Fig.14) has a juvenlle suture with E/L symmetrically bifid. Incidentally, immature whorls of the Colombian species bear constrictions that are absent on mature whorls; ': ·. OCCURRENCE. Socota Member. Upper Aptian. Family DEPcMOCEATIDAE Genus Melchioriie sptit. i923, p.33 - _., .... ,. ---.. .. ...... , . · · '· . __ ... .... .. -- .. IMe Chiorite{ Spath, 1923. TYPE SPECIES. Ammonites melchioris Tietze, original designation. *ehtBrites media Riedel '? : : ig. 9; Text:Fig. 3Q, 3 R. 1938 Melchiorites emerici Rasp. var. media · Riedel, 1938, p. 17, pl. 4, Figs. 9 · 11 pl.12, Fig. 7, pl. 14, Fig. 3. ·· 1957 Melchiorites emerici meaius Riedel, Burgi, p. 134. 1964 Melchiorites emerici medius Riedel, Etayo-Serna, p. 111. non 1965 Melchiorites inca (Forbes), Btirgl, in .. Campbell arid BUrgi, L. C. D. 8393. 1!:1.65 Melchiorites emerici media Riedel, BUrgi, in Campbell and Btirg L.C.D. 839"3. l{olotype. Riedel's figured specimen, 1938, pl. 4, ... ·• . . . . .. Fig. 10-11. !otype.C-127 (U.N.C.M.H.N.C.P.Hy.N.2.). ·,.t'e locality. Utica (Cundinamarca). .. · · .. . Two specimens are available, one of them deformed. The conch is moderately involute· the section of the whorl is subquadrate, feebly on vex tq Oattened and subparallel on adumbilical halt of.flanks, then slightly converging to the feebly arched venter; the umbilical wall is short, vertical, and rounds abruptly Into the flanks. In both specimens the adapical third of the last preserved whorl is septate, the remaining part of the conch represents the living chamber; there are constrictions which begin at the umbilical seam, they are falcoid and wide, they describe an adoral arc on middle of flank and they project in a strong linguiform fashion on venter. On the test of the hypotype C-127 there are faint falcoid sheaves of stressed growth striae forming thin, flat ribbons that project on venter paralleUing the constrictions; on the living cham ber this ornament is visible also on the internal mold where the ribs still retain a uniform thickness. DIAGNOSIS. This species is characterized by A) Its compressed section of whorl, slightly taller than wide, and B) its peculiar sheaves of rm e striae that form low, flat falcoid bands on test. Meuu:rementa. D Euw H W D(Euw % -jH% Hypotype 18 5 7 7 28 38 COMMENTS. The type species of the genus, "Ammonites melchioris" Tietze (1872, p. 135, pl. 9, Fig. 9a, b, 10) has a higher and narrower vaulted whorl section than Riedel's species. Riedel has .discussed other comparable species. OCCURRENCE. Unnamed unit above the Socota Member and below the Capotes Member. Upper Aptian. .Me.l£hiorites121Jlmruj n. sp. PI. 6, Figs. 6, 10; Text-Fig. 3$ Holotype. C-223 (U .N.C.M.H.N.C.P.Ht.N.8). Paratype. (U.N.C.M.H.N.C.P.Pt.N.6.). A) Up to 20 mm fC-2001. Whorls slightly wider than high (at D:l1,H:7, W:9);each whorl covers approximately half of preceding whorl. The inner whorls have rather close, narrow but conspicuous oblique constrictions; on the adapica! segment of the last preserved whorl of this specimen the constrictions begin at the umbilical seam, slant across the umbilical wall, then bend and widen near the middle of the flank, and next project forward as a linguiform arc, that is most narrow at the ventral median line. The constrictions are preceded adapically by a rib which starts near the middle of the flank and on venter it projects in the same fashion as the constrictions; a very shallow depressed zone adorally precedes the rib also. The ornament becomes distinctive with growth. It consists of fine rounded riblets some of which begin in a subdued manner on the umbilical rim and one or two shorter intercalatory ribs appear about middle of the whorl; the large ribs are falcoid, all ribs are well developed on venter. The constrictions trend across the ribs. There are 8 constrictions on the last pre· served whorl and 8 riblets on the space between the two last constrictions; the intercostal dis· tance is slightly larger than the width of the ribs. The umbilical wall is short, vertical, it
24 F. ETAYO ·SERNA rounds abruptly into the convex sides. B) Up to 30 rmn [C-223]. One incomplete specimen septated throughout is available. The early whorls are smooth. The phragmocone is sculpt .. ued with periodic, widely spaced radial flared ribs. These prominent ribs begin at the umbilical margin in a subdued manner; they trend obliquely on the adumbilical third of the whorl or form a tenuous adoral concavity. At the boundaey with the central third of the whorl, the ribs make a sharp bend and then up to the ventral zone they fonn an adoral concavity. Next they cross the venter in a linguiform ado ral arc; they are emphasized adventrally. The section of the whorl is subcircular, slightiy wi· der than high (H: 10m.m; W: llmm), especially on the internal whorls; the venter is broadly rounded grading smoothly into the convex flanks which grade abruptly into the vertical umbilical wall. On the internal mold and also observable on the exterior of the test there is a constriction just ad oral to the flared rib; a flattened area develops adapical to it. Between two of the prominent ribs there are numerous fm e ribs (up to 10-14 on venter) which are divided into two types: 1) slightly prominent, low, fine, top rounded ribs that begin slightly above the urn· bilical rim, their trend is that of an elongated S, like the flared ribs, and 2) fine intercala..T)' ribs . which rise slightly higher on whorl and only rarely bifurcate from the primary ribs. The inter· costal space is at least twice as wide as the ribs, sometimes greater; the umbilical rim is smoot!":; with growth the bifurcation or trifurcation of the ribs seem rather common. On the adoral· most preserved segment the ribs gather in bundles ·fanning a low triangular periumbilical thic· kenning which extends form the center of the flank to the umbilical rim but this does not occur on the preceding whorls. . DIAGNOSIS. This species is characterized · by. A) its subrounded whorl section, B) the in· , creasing number of fine ribs through the onto· · geny, and C) by its strong, flaring linguiform ribs; Miluurements. D Euw · H w Holotype - 31 12 7 1 ·Paratype 22 7 1 7 D{Euw % D/H % 39 ? 32 ? . . COMMENTS,: Both specimens here COfilSi· dered conspecific have to be compared indepel) ·dently to other species. In regard to the smaller specimen, the .closest species known to me is the one figured by Pervinquiere (1907, p. 155, p. 156, Text-Fig. 61, pl. 6, Figs. 21a-b, 22a-c) as "Puzosia AnglGdei Sayn"; this thick form shows fine ribs mostly near the constrictions when:as in my specimens the ribbing is more uniform and perc.eptible inwards, down to the involution line; in the latter feature the Colombian species is more like the holotype (?) figured by Sayn (1890, p. 173, pL.2, Fig. 13a, b, c); this could possibly be due to preservation though. Pervinquiere (ib., p. 156) compared his specimens to "Puz. Emerici Raspail" though he remarked on the flattened flanks and the greater development of the last who;l in the latter. In regard to the large specimen (holotype}, this is somewhat similar to "Desmoceras akus· chaense Anthula" as figured by Jacob (1905, p. 402, pl. 12, Fig. 1; =Valdedorsella Brei&troffer, 1947), but the French species is much more in· volute and its flared ribs have a peculiar splitting at that point where the Colombian species have a centro-lateral acute adoral bend. The African and European species referred to Valdedorsella by Breistroffer (194 7, p. 60) are much more in· flated and narrowly umbilicated than the speci· mens from Colombian here assigned to Melchiorites. The constrictions on the latter group of species is Puzosia-like. This interesting Colom· bian species also resembles Melchiorites media Riedel, but the latter lacks the discrete ribbing on the external part of the whorl and its whorl section is ogival rather than rounded. OCCURRENCE. Socota Member Upper Aptian. Genus · \Valdedorsella)Breistroffer, 1947. : Valdedorsella Breistrofer, 1947, p. 60. . : '' --t. -·..,..-p:•• ,,_.._., • ...,,.,.::,•,j,..p...r•'"" -.... ,...-.,., ,.·,· --- ... . ••-· '• •-·· ----...·- TYPE SPECIES Desmoceras akuschaense An· tula, origtilal designation • Valdedoryella f71 colQ.mbia n. sp. 'M:3, Fig. 10; Text-Figs. 3V, 3W. . Holotype. Santa Ana (U. N. C. M. H. N. C. P. Ht.: ' N.9). Paratype. Santa "Ana (U.N.C. M. H,. N. C. P. Pt. N. 7). A) Up to 35 mm D. [Sta. Anal. 'The section of the whorls is suboval, inflated. The test is ornamented with sinous, flared ribs (27 per whorl), which correspond to prominent ribs on the internal mold. There is a constriction on both sides of the ridge on the internal mold, they follow the trend of the flared ribs but attenuate on venter. On the test the constric· tions are indicated by smooth bands parallel to the ridges. The sulcus immediately adapical to the flared ribs is usually the most prominent on the adumbilical half of the whorl side, but the reverse is true on the adventral half of the whorl side. Between two of the ·prominent ribs there are numerous (:up to 8), rounded ribs, separated by intercostal spaces one and a half as wide as the ribs. 'These ribs on venter represent both primary ribs that originate above the umbi· Iical rim and secondary ribs that arise from the primary at about the midpoint of the Oanks. At the same time the frrst pair of ribs immediately .adoral to constrictions tend to separate therrisel· ves from the rest which gather to form a low bundle at the umbilical rim. B) Up to 60 mm D [Sta. Ana]. The deve· lopment of the ornament continues similar to the previosly described stage except that there
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: 22 has a subelliptical to subcircul
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 and 50: 42 Hypacanthoplites dognaliciae n.
Page 51 and 52: 44 F. ETA YO · SERNA One large spe
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 81 and 82:
ZONATION OF THE CRETACEOUS OF CENTR
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
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
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94 re is an asymmetrical sulcus bor
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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
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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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