PHYLOGENETIC RELATIONS AMONG OXFORDIAN AND KIMMERIDGIAN ASPIDOCERATINAE « CLASSICAL SPECIES », DEDUCED FROM THE SUBBETIC RECORD (SOUTH SPAIN). A PROPOSAL by An to n io CHECA * Sum m ary R £ s u m £ The present work aims to present a scheme, that Ce travail essaie de presenter un schema, qui ne doit must not be considered as definitive, which principal pas Stre considere comme definitif et dont le principal interest is the easening of an image on the relations interSt reside dans le fait qu’il fournit une image sur between « classical species » of Aspidoceratinae in les relations entre « esp^ces classiques » d’Aspidoce­ agreement with the information obtained in the Sub- ratinae, conformement k l’information obtenue dans betic Zone (South Spain), altogether with the detailed la Zone Subb6tique (Sud de l’Espagne), ainsi qu’& la stratigraphical reference of those species in this rSfdrence stratigraphique d6taill6e de ces esp^ces dans region. The last aspect reflects significant peculiarities cette region. Le dernier aspect reflete des particulari­ showed by ammonites (Aspidoceratinae in this case) t y significatives montrees par les ammonites (Aspido­ as are biostratigraphical differences related with their ceratinae dans ce cas) comme le sont les differences biogeographical distribution. The four european biostratigraphiques en rapport avec leur distribution genera of Aspidoceratinae are analysed. Physodoce­ biogeographique. On analyse les quatre genres euro- ras and Orthaspidoceras appear narrowly related, pdens d’Aspidoceratinae. Physodoceras et Orthaspi­ being the basical morphologies of this last genus doceras apparaissent en dtroite relation, les morpho­ always obtained through the accentuation of single logies de base de ce dernier genre s’obtenant toujours characters present in the corresponding species of au moyen d’une accentuation de caractfcres simples Physodoceras. Aspidoceras has two main morpholo­ presents dans les esp£ces correspondantes de Physo­ gical tendencies, that giving rise to the >1. acanthicum doceras. Aspidoceras presente deux tendances mor- (O p p el, 1863) group, that loses its upper row of phologiques principales ; celle qui donne lieu au tubercles through the ontogenetic development, and groupe d’Aspidoceras acanthicum (Op p e l , 1963) qui another more « conservative » tendency, producing perd le rang supdrieur de tubercules £ travers le d6ve- in any case extreme morphologies. Within Pseudo- loppement ontog£n6tique, et une autre tendance plus waagenia, three of the four considered species, that « conservatrice » qui donne lieu, dans certains cas, k show a chronological replacement, compose a very des morphologies extremes. Dans le genre Pseudo- well morphologically recognized evolutive line. waagenia, trois des quatre esp£ces consid£r£es, qui se relayent dans le temps, composent une ligne evolutive tr£s bien reconnaissable morphologiquement. KEY-WORDS : AMMONOIDEA, ASPIDOCERATINAE, PHYSODOCERAS. ORTHASPIDOCERAS, ASPIDOCERAS, PSEUDO- WAAGENIA, PHYLOGENETIC RELATIONS, EVOLUTIVE TENDENCY, OXFORDIAN AND KIMMERIDGIAN BIOSTRA­ TIGRAPHY, SUBBETIC ZONE. MOTS-CLfeS : AMMONOIDEA, ASPIDOCERATINAE, PHYSODOCERAS, ORTHASPIDOCERAS, PHYSODOCERAS, PSEUDO- WAAGENIA, RELATIONS PHYLOGfiNfiTIQUES, TENDANCE EVOLUTIVE, BIOSTRATIGRAPHIE OXFORDIENNE ET KIMMfiRIDGIENNE, ZONE SUBBfeTIQUE. • Departamento de Geologia, Colegio Universitario de Almeria (Departamento de Geologia General, Universidad de Granada) - Departa- mento de Paleontologia y Departamento de Investigaciones Geolbgicas del C.S.I.C., Universidad de Granada, Spain. Geobios, n° 17, fasc. 1 p. 21-31,4 fig. Lyon, fSvrier 1984 — 22 — CONTENTS I — Introduction....................................................22 V. 1 Physodoceras and Orthaspidoceras..........26 II — Antecedents....................................................22 V .2 Aspidoceras..................................................29 V.3 Pseudowaagenia..........................................29 III — Morphological characteristics......................23 VI — Acknowledgements........................................30 IV — Differential diagnosis at the genus level . .23 VII — Literature cited................................................31 V — Phylogenetic considerations..........................24 I. INTRODUCTION The present work puts together conclusions from a incidence in the associations where they take part, previous unpublished work by A. Checa (1981), and reaching a 20-25% during the Kimmeridgian (016riz also the way of the posterior research up today. The & Tavera, 1981), in other words they can be conside­ acomplished labour is centered on the systematic revi­ red as a very important component of the Subbetic sion of the Aspidoceratinae of the Subbetic Zone, car­ fauna at that period of time. ried out by the author since 1980. Other aspects such as the comparatively scarce com­ First of all, since this article will deal with evolutio­ plexity of the shell structuration and its ample strati- nary considerations on a group, whose systematic is graphical distribution-there are recordings at the under reorganization, there will be not so much of an Berriasian-ratify the interest that in principle might emphasis denomination contemplated in detail, as it have the application of the paleontological method in will be the recognition of certain morphological Aspidoceratinae. The study has been carried out on groups of wide spectrum that host a series of « classi­ material belonging to the collections of the doctoral cal species », among which might or might not be thesis of L. Sequeiros (1974) and F. 016riz (1976) included new forms, to evaluate its significate in the altogether with some of the author’s sampling. The evolutive history of the Aspidoceratinae. A general sample analysed was compounded by more than 1.000 view of the most apparent modifications occurring in specimens, the study has been as deep as possible on Aspidoceratinae can be obtained throughout the the morphological characteristics, as it has also been Upper Oxfordian and Kimmeridgian. on the biostratigraphic aspects, in order to conclude a The interest of the study of the, presently conside­ systematic treatment that will enable, definitely, a phylogenetic view of this group during the Oxfordian red, subfamily Aspidoceratinae Zit t e l , 1868 emend. and Kimmeridgian. Sp a t h , 1931 follows various aspects. On the first place, the essentially mediterranean and submediter­ A detailed description of the Aspidoceratinae and ranean character of this subfamily, and, therefore any their temporal distribution has been provided by F. review of this group must necessarily follow through a Olbriz (1976) and A. Checa (1981). The last one also profound study of the Subfamily Aspidoceratinae in presents a first approximation to the mathematical the Subbetic Zone, given the advantageous conditions treatment of the data collected from the sample stu­ of findings. This fact is notably reinforced given its died. II — ANTECEDENTS There is a large number of biostratigraphic studies the first trial to a systematic ordering. This study has of regional coverage where references are made to this two main limitations, first it was carried out on Sub­ group. Anyhow, the only monographic work on this mediterranean fauna essentially, and now we can be subject belongs to W. Buck (1958) and it represents conscious of the high significance that the strict — 23 — mediterranean forms have towards a global compre­ reference is F. 016riz (1976) that constitutes the most hension of this group. Second, the scarce diffusion of extensive review after W. Buck (1958) and the first the work has contributed to the fact that the treat­ approximation to a systematic treatment and biostra- ment of the Aspidoceratinae has not reached its previ- tigraphic determination of the Aspidoceratinae spe­ sible impact, that would also have open new ways. As cies. far as the Subbetic fauna is concerned, the obligated Ill — MORPHOLOGICAL CHARACTERISTICS They are clearly different from other groups of their A first order criterium for differentiation at the spe­ contemporary Perisphinctacea. The spiral is volumi­ cies level is the morphology of the tubercle, that nous in general terms, although there are exceptions. remains uniform at this level and even at the generic one. Finally, the directionality of the tubercle is an The living chamber rarely exceeds one-half a whorl important character at the genus level since they and ends in a simple opening, its design along the might follow a path toward the center of the umbili­ umbilical wall reflects almost fully the tracing of the cus or might be oblique to it or even perpendicular to growth lines in this zone. The ornamentation is based the flank. on simple schemes of tubercles and, occasionaly, ribs. It is interesting, as the principal ornamental characte­ A highly efficient differentiating criterium is the ristic with systematic value, above all the number of occasional presence of ribs. rows of tubercles whose consideration reaches a first The rest of the morphological characteristics, such order rank, being a helpfull criterium, even for dis­ as size, width of umbilicus, heigth and thickness of tinction at the generic level. There may be a single row spiral, design of section, usually have an importance as in Physodoceras and Orthaspidoceras or two as in subordinated to the hierarchy imposed by ornamental Aspidoceras, Pseudowagenia and Simaspidoceras. criteria, although in some cases they may reach a significant r61e face