Estudios geol., 43: 513-520 (1987)
OXFORDIAN AND KIMMERIDGIAN "ASPIDOCERAS" IN THE MEDITERRANEAN. A METHODOLOGICAL APPROACH
A. Checa (*) F. Olóriz (*)
RESUMEN
En el presente trabajo se lleva a cabo un análisis contrastador de la Hipótcsis Nula es tablecida como base metodológica para la investigación evolutiva de los"Aspidoceras" mediterráncos (Checa & Olóriz, 1985). Esta contrastación se lleva a cabo integrando nuevos datos y forma parte de un programa de investigación cuidadosamente planificado. Las divcrsas consideraciones paleogeográficas, sedimentológicas, estratigráficas y paleo biológicas han proporcionado nuevos modelos evolutivos que suponen una sustancial reor ganización estructural de la Hipótesis Nula. En esta estructuración, las Configuraciones Evolutivas Básicas no son consideradas como meros grupos morfológicos, resultado de una lectura del rcgistro fósil, sino que constituyen unidades evolutivas que pueden, por tanto, relacionarse entre sí.
Palabras clave: ammonites, relaciones jilogenéticas, evolución, Jurásico superior, Medite rráneo, Aspidoceratidae, Aspidoceras, Pseudowaagenia, Physodoceras, Orthaspidoceras, Benetticeras, Simaspidoceras, Schaireria.
ABSTRACT
In this study we present a contrastive analysis of the Null Hypothesis, established as thc methodological basis for the evolutive invcstigation of Mediterranean "Aspidoccras" (Checa & Olóriz, 1985). This contrast is carried out using new data, and is part of a re search programme which has been carefully planned. Palcogeographic, sedimentological. stratigraphic and palcobiological considerations have provided ncw evolutive modcls which in turn ¡ead to a structural reorganization of thc Null Hypothesis. In this new struc turc, thc Basic Evolutionary Conformations are no longer considcred as mere morphologi cal groupings, the rcsult of a direct reading of thc fossil record. In this way we propose morphological blocks, rcprcsenting evolutive units which can be related to one another.
Key words: ammonites, phylogenetic relations, evolution, upper Jurassic, Mediterranean, Aspidoceratidae, Aspidoceras, Pseudowaagenia, Physodoceras, Orthaspidoceras, Benettice ras, Simaspidoceras, Schaireria.
Introducción data obtained from later observations. In this first stage the work was principally based on the stra In an earlier study (Checa & Olóriz, 1985) the tigraphic examination of the Subbetic fossil re authors presented the bases of a study project on cord. Here, a series of Basic Evolutionary Con European "Aspidoceras" considering it as having formations was established; these structures re its origin related to the Subbetic Mediterranean presented morphological groupings in which association. In the organization of our research "species", were integrated either in their traditio project two stages were established. In the first, nally accepted sense or in the way they are used data from studies by Olóriz (1976) and Checa in the most recent works. The fundamental rea (1981) were presented and discussed; this allowed son why this treatment was thought most appro us to propose the Null Hypothesis (Checa & Oló• priate was because we wanted to obtain an overa riz, 1985) which was to be contrasted with the 11 view of the morphological stability of these am-
(*) Departamento de Estratigrafía y Paleontología, Faeultad de Cieneias de la Universidad de Granada, Avda. Fuentenueva, s/n. lR002-Granada. 514 A. CHECA y F. OLORIZ monites, on the basis morphological groupings Evolutionary Conformations nor in the interrela which were of the most "cohesive" possible. In tionships which really provide us with the design this way, the integration of "related species" was of the Null Hypothesis do we include evolutiona achieved, as was a certain degree of buffering of ry processes which must necessarily take place in the distortion caused by the multiplicity of syste order to induce the real process of the proposed matic criteria used by different authors. In addi structure. In this linear process we should expect tion, c10se stratigraphic examination allowed us to discover the possibility of recognizing a segre to establish change paths which could express the gation which would imply different levels of in dynamics of the group under study, although in a fluence of the evolutionary processes. As a result general manner. In this first stage of the project we could come c10se to an understanding of the we did not discuss paleobiological questions organization of the structure, which would mean which might cause systematic changes. Thus, we the knowledge of the evolutionary dynamics of did not use concrete taxonomic references, ex the group under study. The Null Hypothesis cept, naturally, those that were obligatory at a which we have mentioned can thus be seen as an generic level in order to establish a c1ear basic or interpretation in which it is necessary to separate der in the exposition of our hypothesis. We the the strains of merely superficial effects from rhose refore used genera in their most usual sense and which are intirnately connected with the processes we further supplied a list of "c1assical species" in which determine the evolutive development. In c1uded in the Basic Evolutionary Conformations. order to achieve this we must contrast the Null The second phase of the study, following the Hypothesis with the data presentIy available and original work plan, has been carried out taking establish the differences which arise whe we con into consideration general geological observations trast the latter with the starting point of our re as well as those of paleogeographical, sedimento search project. logical and biostratigraphical nature. In this con text, we have analysed the various associations, New data and we have evaluated the acquired characters and the fluctuations observed in those that were The most recent interpretation of "Aspidoce inherited. In this way we have given an interpre ras" is to be found in the studies by Checa & tation of the significance of the morphological Olóriz (1984) and Checa (1985). In the first of groupings we have recognized. These groupings these studies paleobiogeographical considerations undoubtedly represent morphospecies, but when and stratigraphic examination occupy a central subject to the aboye described treatment, they position. Starting from these considerations a mo turn out to be justifiable approximations to the nographical study of the aspidoceratiforms in Eu groups which were earlier biospecies of "Aspido rope was carried out, and a new systematic orde ceras" in the Mediterranean Subbetic Basin. The ring established, which takes into account the most significant results in this second phase are "evolutionary results" (cf. Gould, 1977) obser presented in Checa & Olóriz (1985) and Checa ved. In brief: in Oxfordian and Kimmeridgian (1985). forms recapitulatory phenornena (with or without At the present moment the aim of this study is terminal addition) arc interpreted, such as, for to show the results obtained from a contrast of example, evolutionary acceleration and hyper the Null Hypothesis which served as the starting rnorphosis. Pacdornorphosis (presumably neote point for this research project. As a consequence nic) is also dctcctcd on occasions, and sorne cases we will provide an account of the present state of of proportionatc giantisrn were also observed. knowledge about Subbetic Oxfordian and Kim For thc timc bcing thosc examplcs where the ob meridgian "Aspidoceras". taining of new characters cannot be determined by stratigraphic exarnination, have been interpre ted as cases of c1andestine evolution. The structure of the Null Hypothesis In Checa & Olóriz (194H) a quantitativc analy sis of the fossil record is carricd out. This analysis As we have outlined aboye and as has been is organizcd according to the systernatic proposals presented in greater detail in Checa & Olóriz made in Checa (19H5), and the influencc of the (1985), the structure of the Null Hypothesis is ba environrnent in the f1uctuations of the group sed upon ornamental configurations which are throughout the time assessed. The conclusions at considered "sufficiently stable" (at least in princi the genus leve! are of special interest, as is the in pie) as to characterize Basic Evolutionary Con tegration of the data at the subfamily level and formations. Nonetheless, neither in the Basic the obscrvations on the distribution of acmes at OXFORDlAN AND KIMMERIDGIAN "ASPIDOCERAS" IN THE MEDlTERRANEAN 515 the species level. The parallelism observed bet nary base of block O in Checa & Olóriz, 1985 ween the eustatic curve (Hallam, 1978) and the to be, fig. 1). profile of the fossil record in this group of ubiqui New characters which do seem to be of signifi tous ammonites, as well as considerations on dis cance include: tortions in relation to paleoecological factors are - uncoiling in block O. all subject to analysis. In this way the structural - the reappareance of external tubercles in the li- stability of the shells and their relation to conti ving chamber in the forms characteristic of nuity in time is c1early to be seen, as it is also the block C. influence of paleobiogeographical-paleoecological - the restriction of external tubercles to inner factors on the stratigraphic distribution. Finally, whorls in the forms included in block C. the correlation of the environmental volume to the production, frequency and temporal exten In the new structure given for the genus Aspi sion of the acmes is also shown, as is the inciden doceras (Fig. 1) we can observe considerable ce of these factors in the configuration of the sub changes with reference to the stratigraphic distri families. bution of the blocks. The Basic Evolutionary Conformations are now related according to tho Contrast with the Null Hypothesis se evolutionary facts which are most important for this genus. In this way it is possible to distin A contrastive study of the Null Hypothesis, ta guish the following differences among change ken together with the new data available should events which have proved to be essentially recapi be carried out on the basis of the Basic Evolutio tulatory: nary Conformations previously considered. To - the frequency with which evolutionary accela the extent to which the Basic Evolutionary Con ration is found. formations contain groups of c10sely related spe - the different influence on this process accor cies it will be possible to establish directly the dif ding to whether the A-B connection or the A ferent influence in the evolutive processes invol O-E connections, added terminally. accompany ved in the structure of this group of ammonites. it. We will therefore proceed to contrast the Null - the comparative, secondary value of hyper Hypothesis by genera, analysing the "real value" morphosis, with or without terminal addition according to present day interpretations of the (B-C connection), and of proportionate gian characters which define each Basic Evolutionary tism (block O). Conformation. Each of these structures (blocks in Checa & Olóriz, 1985) is potentially susceptible In general, the contrast produces slight changes of a greater or lesser readjustment. As a conse in the structure of the Null Hypothesis. This is quence, the new configurations that are produced probably due to the fact that, during the interval as a result will show us the evolutionary structure under study, the "functional plasticity" in this ge of the group at a generic level as a hierarchical nus must have allowed changes to be produced organization of the evolutionary processes at without reaching a limit situation where deep res work. Finally, we will compare and contrast the tructuring would be the only alternative. In this conclusions of a general nature (d to g in Checa case, therefore, we should not be surprised to & Olóriz, 1985) which affect this group of ammo find the appearance of little penetration of the nites during the Oxfordian and Kimmeridgian in paleobiological considerations in a morphological the Subbetic zane. ordering which is based exclusively on a direct reading of the fossil record. a) Aspidoceras
Taking into account the new information avai b) Pseudowaagenia lable on this genus we can say that the following characters are of little significance: In this case, the new information obtained. has the effect of producing a deep rcstructuring of - the design of tubercle base (blocks A, C, O in the Null Hypothesis. The appearancc ami di~ap Checa & Olóriz. 1985, fig. 1). pearance of blocks and/or evolutionary bases 01' - the design of the whorl section (blocks B, O in blocks, variations in the stratigraphic distribution Checa & Olóriz, 1985, fig. 1). and new connections are the facts which are most - the correspondence between umbilical and la significant at first sight. Moreover, in one case teral tubercle rows (block e and the evolutio- (block C) the new interpretation implies the pro- 516 A. CHECA y F. OLORIZ posal of a new genus (which is phylogenetically presentatives of a genus which had not been con related to the other): Schaireria. sidered previously: Simaspidoceras. Characters which are not very significant inelu Characters of no great importance are: de: - the design of the tuberele base (block A). - the correspondence between umbilical and la - the increasc in size shown in the evolutive base teral tubereles (block A). of blocks C and D. - the presence of external tubereles in the outer - shell uncoiling in blocks C and E. whorls (block E and evolutive base of block - the increase in the number of tubereles m D). block Go New characters which do acquire systematic New characters which do represent important importance are: systematic factors: - the position of the external tubereles (block - the design and position of tubereles in block G o D). - the considerable increase in size (new block). According to the data we have outlined aboye, there appear four taxa at the generic level in the In the new configuration of the Basic Evolutio new configuration, instead of the two which we nary Conformations, both appearance (block .F) had proposed in the Null Hypothesis. One very and disappearance (block B and the evolutlve important fact is the joining of the primitive base common to blocks C and D) are conditioned blocks C and D and of their evolutionary bases, by the control of the evolutionary relations. Pr.i in one single block C/Do This new block has mitive block B turned out to be a polyphyletlc block A of the genus Pseudowaagenia as ances whic~ grouping. The evolutionary fact. pr0.ved toroIn connection with this fact a series of distor gIV~S most important is paedomorphosls, WhlCh tions in the primitive structure takes placeo The rise to the new genus Schaireria (block C). Thls family relation between blocks A and CID is re specie~ genus develops its most typical in the 10 versedo Block C/D becomes the Basic Evolutio wer Tithonian its common ancestor IS Pseudo nary Conformation and block B derives from it ~he waagenia. Factors of less importance in new (in our previous proposal it was related to A)o configuration are evolutionary acce1eratlOn (A, Block E becomes extremely significant, since it is D, E) and proportionate giantism, which charac now considered as the common ancestor for terizes the new block F. blocks F and G o Block G is subdivided as from In general this contrast produces major chan the observations on the tubereleso We should ges linked to evolutionary phenonema of great emphasize the general nature of this reconsidera dev'elopment potential (paedomorphosis) ..alt tion of the biostratigraphy in the new Basic Evo hough it is not possible to interpret the ongmal lutionary Conformations. motivating process, due to the reduced nllmb~r As we have observed, this is the group of of observations available. We have also found ml forms where the consideration of paleobiological nor changes in which, as in the case of the genus data leads to the most drastic restructuring. This Aspidoceras, evolutionary acceleration and pro is due to the first-rank evolutionary processes portionate giantism are involved: the c~ang~ does which determine the connections between Basic not produce a high level of morphologlcal dlscon Evolutionary Conformationso Indeed, neotenic tinuity either. paedomorphosis can be shown in 40% of the evo lutive relations we have observedo We propose c) Physodoceras and Orthaspidoceras elandestine evolution for the origins of the blocks that are directly derived from basic C/D, and as This group undergoes important modifications the origin of block G] (in the cases mentioned after the contrastive analysis. The restructuring this should not be interpreted as the product of of the blocks is a profound one, and as a result inadequate or defective information)o Finally, the new relations and new stratigraphic distributions appearance of block F provides an example of a are established. In one case one of the blocks change induced by a lower-rank factor, such as which had been proposed previously (B) is now evolutive acceleration, which is encouraged by considered to represent anew taxon at the gene terminal addition and becomes as important as ric level (Benetticeras) after making the changes some of the cases of neoteny we have mentionedo required according to the new information. Anot It is of special interest to note the presence of her of the original blocks (F) will now inelude re- homeomorphism in this group of forms. Benetti- OXFORDlAN AND KIMMERIDGIAN "ASPIDOCERAS" IN THE MEDITERRANEAN 517
ceras and Orthaspidoceras both derive from the g) A first increase in size at the leve! of the same evolutionary line of Physodoceras with a Strombecki zone can now only be found, partially stratigraphic difference of a little more than two in Aspidoceras. In the group of forms be!onging biozones in the lower Kimmeridgian. to Physodoceras-Orthaspidoceras, the increase in size OCCurS in the Divisum zone. In Pseudowaage d) Our original statement that "no stock with nia it is found at the base of the middle Kimme primitive configuration continues beyond the 10 ridgian. wer Kimmeridgian" has been proved to be basi Our estimates about the relation between the cally correct. Only one species, Pseudowaagenia repetition of this phenomenon and the diversifi micropla (OPPEL), penetrates the base of the cation of lines have been proved correcL middle Kimmeridgian (in the interval zone of Compsum). As a resuit, the middle Kimmerid h) The observations on the persistence of the gian may be considered as an interval where a re external row of tubercles should be limited to As newal of Mediterranean aspidoceratiforms takes pidoceras. In Pseudowaagenia the fluctuations do place. This group of ammonites is thus affected not seem to be significant. by the "faunal relay" which has been observed in i) Our generalizing remarks on the develop the Mediterranean association during the middle mental trends, which we applied to Aspidoceras, Kimmeridgian (Olóriz, 1976; Olóriz & Tavera, Pseudowaagenia and Physodoceras, could not be 1981). applied to this last genus. This new statement is e) With regard to the "great diversification in based on the examination of the intraspecific evo,. the Strombecki and Divisum zones" it is necessa lutive re!ations detected. ry to make sorne qualifying remarks, following j) The orientation and desing of tubercles in the quantification carried out by Checa & Olóriz upper Kimmeridgian Aspidoceras have been (1984): shown to be a secondary character. - the greatest diversification, together with the greatest deve!opment of the populations, oc ACKNOWLEDGEMENTS CurS in the interval running from the Divisum This research was carried out with the support of the project 33.21 of the CAICYT (Spanish Ministry of Education ami Scien zone up to the interval zone of Compsum; the ce). data obtained on diversity in the Kimmeridgian show that this, aboye and below that maximun Referencias point, falls and is uniformo the most diversified genera are Aspidoceras, Checa, A. (1981). Aspidoceratinae (Amlllonitinll) del kimmerid Pseudowaagenia and Orthaspidoceras. With the gense en la zona Subbética. Tesb de Licenciatura. Uni\'ersidad de Granada. 211 p. (unpublished). exception of Orthaspidoceras, which is limited Checa, A. (1985). Los aspidoceratiformes en Ellropll (AllllllOlli to the top of the lower Kimmeridgian and the tina, Aspidoceratidae: slIbfamilias Aspidoceratinae r Ph.l'Sodo base of the middle Kimmeridgian, both others ceratinae). Tesis doctoral, Universidad de Granada. -+ D p. maintain their level of specific diversity almost Checa, A. & Olóriz, F. (1984). Significative Mediterranean "As pidoceras" in upper Jurassic biostratigraphy. In: IlIIematiollal constant from the Divisum zone till the end of Symposium on Jllrassic Stratigraphy (O. Michelsen 8: A. the Kimmeridgian. Zeiss, edit.). Geo!. Survey of Denmark. Copenhagen. _,y-, 414. f) As regards the persistence of evolutionary li Checa, A. & Olóriz. F. (1985). Evolutionary trends in Oxfor nes in the middle and upper Kimmeridgian, we dian and Kimmeridgian Subbetic Aspidoceratinae (Southern Spain). A proposition of Null Hypothesis aoout Ihe evolutio can state the following: nary course in a highly significan! group of tethydian lurassic ammonites. BolI. SOl'. Paleolll. Itlll.. ~-+. 1·15-159. after a very detailed stratigraphic examination Gould, S.J. (1977). Ol/rogel/)' al/(I phrlogelll·. Har\'anl Uni,. we found that there are eight lines, and not six, Press. Cambridge. 501 p. as was proposed in the original Null Hypothe Hallam. A. (1978). Eustatic cycles in the lurassic. I'alaeogeogr.. siso Palaeoclimatol., Palaeoecol.. 2-'. l--'~. Olóriz. F. (1976). Kimmeridgen.H'- Til/(íl/ico infáior 1'11 el sector with the restructuring of the Basic Evolutiona central de las Cordilleras Béticas (::ol/a SlIl>l>étiCll). Paleolltolo ry Conformations we find that there are three gía. Bioestratigrajía. Tesis doctoral. Universidad de Granada. (and not four) which originate in the Divisum 758 p. Olóriz, F. & Tavera, 1.M. (1981). El lur Appendix Species lO be included within each block accor ding to the systematics proposed in Checa (1985). block A: A. bil10dllm (OPPEL) block B: A. sesquil1odosllm FONTANNES block C: A. fil1aresi CHECA and A. lll1inodosum TOULA block D: A. longispinllm (SOWERBY) and A. hysrricosum (QUENSTEDT) block E: A. apenniniclIm ZITTEL JI 1 t~-----=-~ Ouh,. tubudu. are placed in the outt,. urgiR --={ Uncoi 1j"9 (1I) I ~ I 1 . I e e ~=-- O.t" t.b"d.. or. phced ot • h.H .r . F ~ ~ ho thirds on lhe fhnk Occnion~l e III in'rust in sizt (11) R 1/ ot 'Joter lubtrtlu are rutrichd to inntl" "horls r.",,'''"' '" . l II -: Oulw~,.ds disphc.utftt o, outer l",b~rc.hs ~ ~ult" tubertles ••y o,. hol reappur al oute,. whorh ¡"(rene in S.iH (1) 8!F-----=----:---· ----;1 :- ,,,~I J LL..-----.,------...... L- -r-'--+:'I iF=------Outer tubtr-cles disappeu al oultr whorls ~: j :------~~-----'i- -~~=~ __~--7 u. ~)ui inll'oluh lo nolule O Kounded to deprnnd uction A ~ "'o ro"s o( tttbtrchs '",berdes. of both rOll5 Il"'t sy.utricdly 01" tri.ngh-likt disposed Oute .. tubertlu arce pl.etd at once third or tiro fifth, on the fl.nk . ---1 __J..:;ln::n:.::.;.;':.:'.;.:.bTube .. ch$•.;;r::.c::lt:..s::..re se.inu.erous.:r;.:• •.:::p:..:I;.:.;.;tt::d:..::.n:;;.:.th.:::.:::.:..O:.,:b:..i;:;li::C::.._I_._d9_. ....IL- ~__ ___ "L""r'J Y ~ Tube .. tlu hue • b.ckw.rds hngthened bue Fig. I.-Evolutionary framework 01' the genus A.I'pidIJcera.l'. OXFORDlAN AND KIMMERIDGIAN "ASPIDOCERAS" IN THE MEDlTERRANEAN 519 block A: Psw. micropla (OPPEL) block C: Sch. neumayri CHECA block D: Psw. haynaldi (HERBICH) block E: Psw. acanthomphala (ZITIEL) block E: Psw. dietli CHECA r--.,.------:lr------~-~------~_j¡ ~ l- I q,-+------.....,f--+------:---~---.------1 Oval to rectangular seetion External tuberchs in urginal Uncoiling (very evolute) (Il) Incruse in sia (I 1I) Squared suture-line Tuberchs are placed at he D thirds on tlle fhnk f---r---T-1r------+------f---i-----~Tube,.clesare se.inu.erous Uncoiling (evolute) (1) F Disappnrance of ooJte,. tube~clu Co.parative incruse in the whorl (1) upansion rate Incruse in sin (11) .,¡;~ I ~ /---- 1 !======~ ~~ ¡ ______~_-----:' :.,, ....JI L-~---__(_------L._.+_------lI A u. Se_iinvolute Oval section, with narro" venter Medi¡;n whod expans:_~n ratee O TilO rollt' of hJbercles • X Outer tubercles -are phced on the .iddle flank 7 _~_-_-_~- -_~_ ~ F.1 Guterluberchstubercles..re nu.erouseln be present or Rot .___ -.!7 L --L.T_"b_._"_I_,_,_._i_'h_._"_._"_,_"_'i_._I_IY_le_"_._'h_._"_.d_b_.._. Jl~ ~ Fig. 2.-Evolutionary framework of the genera Pseudowaagenia and Schaireria. 520 A. CHECA y F. OLORIZ block A: Ph. altenense (D'ORBIGNY) block B: BII. benellii CHECA block C and O: Ph. \Vo/fi NEUMAYR block E: O. ziegleri CHECA block F: S. bucki CHECA block G,: O. garibaldii (GEMMELLARO) block G1: O. uh/andi (OPPEL) I ,------;¡ lubtrclu are plaud on the G2 Rounded d ------~ B e,D Oul uction, .ore or leu depruud Median whorl upansion rale (1) Tuberclu .. re seainu.erDus luberdu groll as cofttinntion af the fhnks and are direchd inlfards ove,. the u.bi I icus Tuberclu with an essntLI11y lengthened base .~ Fig. 3.-Evolutionary framework of the genera Physodoceras, Benelliceras. Ort!/(/spidoceras and SillJIIspidoceras.