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AMERICAN MUSEUM NovJitates PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. 10024 Number 2815, pp. 1-10, figs. 1-7, table 1 April 11, 1985 Preserved Ammonitellas of Scaphites (Ammonoidea, Ancyloceratina) NEIL H. LANDMAN' ABSTRACT Ammonitellas, embryonic shells ofammonites, and body chamber angles less than 600. However, occur in the Upper Cretaceous (Turonian) ofCol- the lack of a body chamber during life is an im- orado associated with adults of Scaphites ferro- possibility and suggests that the primary varix must nensis Cobban. They average 650 ,um in diameter be a point of weakness for postmortem breakage. and are similar to the embryonic whorls of the This, plus the presence of young postembryonic associated scaphite species to which they probably shells that extend beyond the primary constriction belong. They terminate at the primary constriction and reveal two to six septa, implies that variation and accompanying varix but display variation in in number of embryonic septa above the prosep- number of embryonic septa from shells with only tum may be false. Based on functional morphol- a single prismatic proseptum and body chamber ogy, the newly hatched ammonite may have led a angles of2900 to shells completely filled with septa planktic existence for some time after hatching. INTRODUCTION Embryonic shells of ammonites (called other shelled cephalopods. I report here the ammonitellas by Drushits and Khiami, 1970) results ofa study on minute ammonite shells have been discovered in Mesozoic deposits identified as ammonitellas of Scaphites from throughout the world (Dreyfuss, 1933; True- the Upper Cretaceous (Turonian) of Colo- man, 1940; Wetzel, 1959; Drushits and rado. Khiami, 1970; Birkelund, 1979; Blind, 1979; Kulicki, 1979; Bandel, 1982; Dietl in letter AND cited in Bandel, 1982; Landman, 1982a). In- MATERIAL METHODS spection of intact, well-preserved shells per- Several thousand minute ammonite shells mits the determination ofthe number ofem- were discovered in the body chambers and bryonic septa and the patterns of embryonic adhering matrix of 15 mature specimens of development. The mode oflife ofthese newly Scaphitesferronensis Cobban, an Upper Cre- hatched ammonites is based on their func- taceous (Turonian) heteromorph. These 15 tional morphology, faunal association, and specimens were collected by W. A. Cobban mode of occurrence. These observations on in 1967 from the top of the Juana Lopez morphology and mode of life form the basis Member of the Mancos Shale 1.7 miles for comparison with the early ontogenies of northeast of Austin in Delta Co., Colorado I Assistant Curator, Department of Invertebrates, American Museum of Natural History. Copyright © American Museum of Natural History 1985 ISSN 0003-0082 / Price $1.50 2 AMERICAN MUSEUM NOVITATES NO. 2815 The original shell microstructure is generally preserved and the chambers are filled with shale and orange-colored calcite. Associated with these ammonites are thousands of tiny clams, fish scales, and vertebrae. The clams range from 300 to 550 ,um in length and ap- pear to have already undergone metamor- phosis from a planktic larval state (Lutz, per- sonal commun., 1984). Several minute ammonite specimens were worked out ofthe matrix but tended to break or emerge as internal molds without shell. A more reliable method to view the entire spec- imen and avoid breakage was to embed shells still retaining matrix in epoxy. Prior to embedding, these specimens were mounted onto an epoxy base and oriented. They were subsequently ground and polished to the me- FIG. 1. Diagram of median section of am- dian plane of symmetry through the siphun- monitella illustrating protoconch diameter (PD), cle. All size measurements and counting of ammonitella diameter (AD), and ammonitella an- gle (<). The ammonitella angle is equivalent to septa were made on the median plane. Spec- the body chamber angle of an ammonitella with imens were also uncovered by grinding down only a proseptum. chunks of ammonitiferous material. This method sometimes revealed the most com- plete specimens but because orientation was (USGS Locality no. D6022). No other am- not preset, measurements of diameter and monite species were present at this locality other dimensions were subject to error. Al- (Cobban, personal commun., 1984). The body though preservation was generally very good, chambers of these 15 specimens are largely the presence of calcite fracture surfaces and internal molds and are composed of calcar- obscuring sedimentary matrix in some shells eous shale and coarsely crystalline calcite in made counting of septa problematic, so such addition to the accumulations of small am- shells were omitted from study. Therefore, of monites. These ammonites, less than 1 mm 85 polished sections prepared, 65 were used in diameter, co-occur with numerous slightly in this study. larger specimens up to 2 mm in diameter. Five standard measurements were made *_ t46* B s * _ ;* s S o.,.' ' s |L* s .|.Mt- W; . ; FIG. 2. (A). Ammonitella of Scaphites freed from the matrix. It is a steinkem but retains some shell near the primary constriction which displays a tuberculate micro-ornamentation{aX.-.(B). The -arrow.points. to the ventral saddle of the prosuture, the only suture present on the specimen. 1985 LANDMAN: SCAPHITES 3 TABLE 1 Ammonitella Diameter (in Microns), Angle (in Degrees), and Protoconch Diameter (in Microns) for Minute Ammonite Shells from USGS Locality No. D6022a Scaphites ferronensis and Group I Group II Group III Group IV Scaphites whitfieldi X SD n x SD n x SD n X SD n x SD n AD 645.7 77.76 18 605.8 33.05 19 617.3 39.42 10 648.0 67.1 15 619.0 42.49 199 AA 286.6 11.66 16 283.8 18.23 18 280.44 6.00 9 286.9 11.26 14 284.0 11.68 169 PD 322.3 21.30 9 327.1 10.86 9 319.1 15.79 7 331.0 19.31 3 320.1 29.09 184 a Group I refers to shells that end in the primary varix and possess only a proseptum. Group II refers to shells that end in the primary varix and are completely filled with septa. Group III refers to shells that end in the primary varix and possess 2 to 8 septa. Group IV refers to shells that extend beyond the primary varix. The last column on the right represents values for adults of S. ferronensis and S. whitfieldi from Landman, 1982b. Abbreviations: AD, ammonitella diameter; AA, ammonitella angle; PD, protoconch diameter; X, mean; SD, standard deviation; n, number of specimens measured. on all specimens wherever possible (fig. 1). and Waage, 1982). In exceptionally well-pre- (1) Protoconch diameter taken through the served specimens, the proseptum appeared center ofthe protoconch and the ventral edge prismatic; all later septa appeared nacreous. ofthe proseptum. (2) Maximum diameter of The caecum and prosiphon were not pre- the ammonitella measured through the cen- served in any specimens. ter of the protoconch and the primary varix, Based on the number ofsepta present these the conspicuous nacreous thickening near the 50 ammonitellas fell into three groups (fig. end of the first whorl (Landman and Waage, 3A-C, table 1). 1982). (3) Ammonitella angle measured from I: Twenty specimens featured only the pro- the proseptum to the end ofthe primary con- septum with body chamber angles (equiva- striction and accompanying varix. This is lent to ammonitella angles) ranging from equivalent to the body chamber angle of an about 270° to about 3100 (average approxi- ammonitella with only a proseptum. (4) Body mately 2900, fig. 4). Their average diameter chamber angle. This measurement may be was about 650 ,um. Their protoconch diam- particularly liable to underestimation be- eter averaged about 320 um. cause postmortem breakage may have short- II: A nearly equal number (19) were com- ened the body chamber. (5) Number ofsepta pletely filled with septa, with body chamber counting the proseptum as one septum. angles less than 600. In most specimens, the primary varix was perfectly intact and marked the end of the shell. In a few specimens the RESULTS varix was broken. Broken, curved fragments Fifty shells in polished section terminated of shell were sometimes observed near the at the end of the primary constriction and specimens. The ammonitella diameter and accompanying varix or at the varix trace. angle ofthese specimens averaged about 610 These features mark the end ofthe embryonic ,um and 2800, respectively. Their protoconch shell or ammonitella (Drushits and Khiami, diameter averaged about 330 ,tm. 1970; Drushits, Doguzhayeva, and Mikhay- III: Eleven specimens featured two to eight lova, 1977; Kulicki, 1979; Tanabe, Fukada, septa. Shells with two septa had body cham- and Obata, 1980; Bandel, 1982; Landman, ber angles of 2500 to 2600. Shells with four 1982a). Similar shells freed from the matrix septa had body chamber angles of 2000 to and viewed in the round displayed the tu- 2100. Those with six to eight septa had body berculate micro-ornamentation previously chamber angles less than 1500. Ammonitella observed on the embryonic whorls ofvarious diameter and angle averaged about 620 ,um species ofScaphites (fig. 2; Bandel, Landman, and 2800, respectively. Protoconch diameter 4 AMERICAN MUSEUM NOVITATES NO. 2815 FIG. 3. Median cross-sections of minute ammonite shells from the Upper Cretaceous (Turonian) of Colorado. Shells A-C terminate in the primary constriction and accompanying varix, features that mark the end of embryonic development. Shell A displays only a single proseptum, Shell B is filled with septa (the "color changes" between adjacent chambers help to emphasize the positions ofthe septa), and Shell C displays 6 septa. Shell D extends beyond the varix trace (the impression of the primary varix on the steinkem) and is clearly postembryonic. It possesses six septa.
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  • Origin of the Tethyan Hemihoplitidae Tested with Cladistics (Ancyloceratina, Ammonoidea, Early Cretaceous): an Immigration Event? Didier Bert, Stéphane Bersac

    Origin of the Tethyan Hemihoplitidae Tested with Cladistics (Ancyloceratina, Ammonoidea, Early Cretaceous): an Immigration Event? Didier Bert, Stéphane Bersac

    Origin of the Tethyan Hemihoplitidae tested with cladistics (Ancyloceratina, Ammonoidea, Early Cretaceous): an immigration event? Didier Bert, Stéphane Bersac To cite this version: Didier Bert, Stéphane Bersac. Origin of the Tethyan Hemihoplitidae tested with cladistics (Ancylo- ceratina, Ammonoidea, Early Cretaceous): an immigration event?. Carnets de Geologie, Carnets de Geologie, 2014, 14 (13), pp.255-272. insu-01071656 HAL Id: insu-01071656 https://hal-insu.archives-ouvertes.fr/insu-01071656 Submitted on 17 Oct 2014 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Carnets de Géologie [Notebooks on Geology] - vol. 14, n° 13 Origin of the Tethyan Hemihoplitidae tested with cladistics (Ancyloceratina, Ammonoidea, Early Cretaceous): an immigration event? Didier BERT 1, 2 Stéphane BERSAC 2 Abstract: The Late Barremian Hemihoplitidae (Ancyloceratina, Ammonoidea) are widely known in the northern Tethyan Margin and the Essaouira-Agadir Basin (Morocco). Their rapid evolution and diversifi- cation make them one of the key groups for that period, but their origin remains poorly known and several competing hypotheses have been published. These hypotheses are tested here with cladistic analysis in order to reject those receiving the least support and discuss those well supported.
  • Albian and Cenomanian Ammonites of the Eastern Margin of the Lut Block (East Iran)

    Albian and Cenomanian Ammonites of the Eastern Margin of the Lut Block (East Iran)

    Carnets Geol. 16 (25) Albian and Cenomanian ammonites of the eastern margin of the Lut block (East Iran) Javad SHARIFI 1 Seyed Naser RAISOSSADAT 2, 3 Maryam MORTAZAVI MEHRIZI 4 Maryam MOTAMEDALSHARIATI 5 Abstract: Upper Albian and Lower Cenomanian ammonites occur on the eastern margin of the Lut block in eastern Iran. The ammonite assemblages described herein are from the Nimbolook and Kerch sections located west of Qayen. The following taxa are described: Mantelliceras mantelli (J. SOWERBY, 1814), Mantelliceras saxbii (SHARPE, 1857), Mantelliceras sp. 1, Mantelliceras sp. 2, Mantelliceras sp. 3, Sharpeiceras laticlavium (SHARPE, 1855), Sharpeiceras schlueteri (HYATT, 1903), Puzosia (Puzosia) mayoriana (ORBIGNY, 1841), Hyphoplites costosus C.W. WRIGHT & E.V. WRIGHT, 1949, Mortoniceras (Mortoniceras) cf. fallax (BREISTROFFER, 1940), Mantelliceras cf. mantelli (J. SOWERBY, 1814), Caly- coceras (Gentoniceras) aff. gentoni (BRONGNIART, 1822), Idiohamites fremonti (MARCOU, 1858), Mariella (Mariella) sp., Mariella (Mariella) dorsetensis (SPATH, 1926), and Turrilites costatus LAMARCK, 1801. The ammonite assemblages clearly indicate a late Albian-middle Cenomanian age for the Nimbolook section and late Albian-early Cenomanian age for the Kerch section. Key-words: • Albian; • Cenomanian; • Cretaceous; • ammonites; • systematic paleontology; • biostratigraphy; • Qayen; • Lut block; • Iran. Citation: SHARIFI J., RAISOSSADAT S.N., MORTAZAVI MEHRIZI M. & MOTAMEDALSHARIATI M. (2016).- Albian and Cenomanian ammonites of the Eastern margin of the Lut block (East Iran).- Carnets Geol., Madrid, vol. 16, no. 25, p. 591-613. Résumé : Ammonites albiennes et cénomaniennes de la bordure orientale du bloc de Lut (E Iran).- Des ammonites de l'Albien supérieur et du Cénomanien inférieur sont présentes sur la bordure orientale du bloc de Lut dans la partie orientale de l'Iran.