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ZONATION OF THE CRETACEOUS OF CENTRAL COLOMBIA BY AMMONITES 41 of the ventral nodes. The final type of ornamen tation -as far as it is known- consists of well marked slightly flexuous, well separated ribs which project a bit onto venter where they are slightly depressed along the ventral median area and slightly raised on both sides of that area. The ribs begin at the external part of the umbi lical wall with a little thi!:kening but are not tu· berculate; there Is usually one intercalary rib whicll begins at the periumbilical rim whre it is inclined toward the preceding rib. The inter· costal whorl section is transversely rectangular with rounded comers. The umbilicus is deep, slightly inclined. DIAGNOSIS. This species is characterized l:ly: A) the early and brief strenthe ing of its lateral tubercles and the ventral hngu1form pro· jection or the ribs, and B) its compressed sub qudrate whorl section. Measurements. c. 514 C·514 D Euw 16 6 30 12 H W D/Euw % 7 8 33 12 14 40 D/H% 46 47 COMMENTS. This species differs from Vei:tisites (Zambranoites) zambranoi n. sp. be cause on the latter the projection of the ribs on venter is retained or stressed to a greater diame ter. Ve ctisites (Zambranoites) cruzi n. sp. by cofrtrast stresses its ornament very early in the otitogeny and the intercostal distance is very .lile, OCCURRENCE. Socota Member. Upper Aptian. This species is named in honor of Hermann Duque, paleontologist of the Instituto Nacional ? } nvestigaciones <strong>Geolo</strong>gico-Mineras, Bogota. f : LC( yp a : a .:,o!.}!_ te (8:2 HJ!pacanthoplites Spath, 1923, p. 64. 2!1 TYPE SPECIES. Acanthoceras mille tianum (d'Orbigny) var. plesiotypica Fritter, original designation. raacanthoplites (?) os_naliciae n. SJ?.: .. PI03, fig. 11. Ho)otype. T.P.I. Guaduas (U.N.C.M.H.N.C.P.Ht. , . · N.30). Paratypes. T.P.I. Guaduas (U.N.C.M.H.N.C.P.Pt. N30,31). ·. A) Up to 15mm diameter{T.P.I. Guaduas]. At 'the .innermost whorls (D:9mm) the section ubquadrate with rounded periventral mar· ipDS and venter; the sides are convex, the umbi· heal willl is subvertical. The ornament consists o ribs which begin at the umbilical rim and are S!lghtly flexuous, rounded, with short vertical s.les but flattened top and they progressively Wl.d.en . from the umbilical margin toward the Penphery; the ribs are separated by subequal !n.tercostal spaces; the former cross the venter 1" a feeble adoral curvature. The ribs are slightly depressed along the ventral median line producing on each side feeble transverse bullaelike elevations: Occasionally a minute conical tubercle developes on one rib (??). The ribs may also bifurcate on the adumbilical third of the flank; they tend to become more rounded with growth. B) Up to 30 mm D [T.P.I. Guaduas]. The early portion of the last whorl is subquadrate, it has flattened sides but rounded periventral and ventral margins; the umbilical wall is subvertical and rounds smoothly into the flanks; at the adoral portion of this specimen the whorl sec· tion is subrectangular. The ornament consists of ribs which initiate midway on the umbilical wall. The ribs are rounded,. well separated , sigmoidal; irregularity some of the ribs bifurcate on the adumbilical third of the flank, both from the adapical side of the primary ribs or from the adoral side of them ; there are intercalary ribs also. The ribs become slightly higher and wider on the venter. The ribs flare out on the umbilical rim and are slightly weakened on the middle of the venter. C) Up to 50 mm D [T.P.I. Guaduas]. The ornament is characterized by a conspicuous alternation of ribs which on one side appear as primary but on the other as secondary. Toward the aperture the venter is well rounded, the ribs tend to be prorsiradiate uniform and elevated on venter. The ribs have a weakly biconcave profile and are slightly elevated on the venter. There are 37 ribs on venter of the last preserved whorl. DIAGNOSIS. This species is characterized at mediun and large sizes by : A) its radial to fee· bly flexuous ribbing, B) the tendency of the secondary ribs to branch from the raised peri· umbilical flanges of the primary ribs and C) the tenuous periventral bullate swl#llings on venter. Measurements. D Euw H W D/Euw "/o D{H% T.P.I. Guaduu 15 5 7 7 33 46 T.P.I. Guaduaa 30 10 13 12 33 43 T.P.I. Guaduas 32 18 21 18 35 40 COMMENTS. A comparable species was described by Liss6n (1925, p. 27, pl. 2, figs. 4, 5) as "Parahoplites Mill e tianum d' Ob. sp.", but very little can be determined from his illustration or description except that the Colombian and the Peruvian specimens look very similar. The neotype of Hypacanthoplites plesio· typicus (Frittel) as figured by Casey {1965, p. 42tl, Text-Fig. 155b, c) has stronger and flexuous ribbing on the flanks than on the Cclombian species. Furthermore on the former the ribs are thick on venter [on the illustration] but they are thin in the Colombian species. OCCURRENCE. Socota Member. Upper Aptian. This species is named in honor of Miss. Alicia Vanegas Leyva, former librerian of the Servicio <strong>Geolo</strong>gico Nacional of Colombia.
42 Hypacanthoplites dognaliciae n. sp. ? Reference. Specimen C· 222. The early portion of the last whorl is hi· gher than wide with maximum inflation on the adumbilical third of the flank; the sides are fla· ttened and slightly convergent towards the wide flattened venter. The umbilical wall is oblique and rounds smoothly into the flanks. The early part of the last whorl has fine acute ribs, which begin on the middle of the umbilical wall or at the umbilical rim; these ribs are more or less falcifonn on flanks. The primary ribs are characteristically prominent, flaring out on the adumbilical third of the flank whereas the secondary ribs may flank from the adoral side of the primary ribs on the adumbilical third of flank, or they may appear independently but they are not empha· sized adumbilically. The intercostal spaces are twice as wide as the ribs. On the adventral third of the whorl and on venter the ribs 1\le flattened. The ribs are almost imperceptibly elevated on venter. There are 38 ribs on the .renter of this specimen. Measurements D Euw H W D/Euw%DfH0/o C·228·B 32 11 14 12 34 44 COMMENTS. This specimen differs from the holotype mostly because the mature ('?) living chamber appears at a much smaller diameter, this. occupies two thirds of the last preser· ved horl. OCCURRENCE. Socota Member. Upper Aptian. r """ . -G";----ad:rham}cer-¥·'g·ni. 'm:E"SPECiEs. Jua;;;r; ;; ;··}u-;,;;trhan ; mi n. g.1 n. sp. L> :: Yu,r£nay•O. Kl."ttr v-- 16.>o•f; .-1!/Ar . DIAGNOSIS. Evolute conchs reachmg moderate size. The early depressed whorl section rapidly changes into a compressed oval sec· tion. The early ornament consists of fine flexuous, closely spaced ribs which cross the venter uninterruptedly, these ribs progressively separate from each other and widen on venter, likewise the ribs differentiate between primary and intercalary; with growth the primary ribs flare out on the adumbilical half of the flank, all ribs are less prominent on the adventral half of the flank. AU' ribs have a tendency to be excavated on their adoral face along the ventral median line, producing on both sides of it more or less conspicuous elevations. On the living chamber the depression of the ribs abruptly ceases and they have a girdle like appearance on venter f= Colo mbiceras-like stage] . No tubercles occur throughouWh.e ·ontogeny. . COMMENTS. This genus has already been illustrated as "Du{renoyia" by Casey {1965, p. 418, text-fig. 152): "Dufrenoyia sp. example showing Colombiceras·like sculpture on final quarter-whorl, indicative of a link between the F. ETAYO - SERNA Deshayesitidae and the Acanthohoplitinae, "Upper Aptian, near Bogota, Colombia (Univ. California no. C-1325)". I have examined this specimen and as is shown on the right-hand fi. gure in Casey's illustration the depression of the ribs along th ventral median line is accentuated adorally before the "Co lombiceras-like" sculpture suddenly develops. In other words, the depression of the ribs ceases before the final living chamber. From study of this new genus, it ap· pears that the "Clavate termination of the ribs bordering the siphonal band" of the "post·nepionic ventral growth" of Du(renoyiD (Caser, 1964, p.376) and the periventral "elevations ' of Juandurhamiceras are not homologous morphological elements: on the latter the ribs in early ontogeny cross. the venter uninterrupte· dly and subsequently they tend to depress along the ventral median line, but on the former the reverse is true with the addition that the ribs are interrupted on venter in an early stage. Previous to the present study precise in· formation on the exact stratigraphic position of Juandurhamiceras was not available. It is here presented because together with specimens of the type species I have found a specimen that I consider conspecific with the specimen illustrated by Casey (op. cit., text-fig.I52). I am making it the holotype of a new species: Juandurhamiceras joepecki n. sp., characterized by the rapid acquisition of the "Colombiceras-like sty· le of ribbing". Comments on the specimen illustrated by Casey, both as to its uncertain stratigraphic position or its significance as a "link" have been made by Wiedmann (1966, p. 45) and Wiedmann and Dieni (1968, p.93), respectively. The genus Juandurhamiceras differs from Colombi· ceras (Spath, 1923), here understood to embrace those species closely resembling the type species, by the lack of any indication of lateral tubercles, at any stage of owth. Incidentally the tendency to proCiuce girdle like ribbings, i believe, is not per se an indication of phlyoge· netic linkage. This genus is named in honor of Emeritus Professor John (Spanish: Juan) Wyatt Durham, of the Department of Paleontology, University of California at Berkely. ...J.BtrodurhQ!!Ji"m uangurhamJ..n. sp .. Pf.4, 1'ig.2; Pl.3, fig.5; Text-figs. 5C, 5J; 12. Holotype. Santa Ana A.P.G. (U.N.C.M.H.N.C.P . . Ht. 31). Paratype. Santa Ana A.P.G. (U.N.C.M.H.N.C.P. Pt. 32,33,34). • . ·-.,. . : •. . . . A) Up to 30 mm D (Santa Ana A.P.G.). The early whorls were studied by disecting one specimen. The protoconch is depressed; the adapical section of the..second whorl is wider than high , with its maximum width located at center of flank, but the adoral portion of this , ...
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: 40 last whorl the ribs are inconspi
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 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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