Palaeontologia Electronica http://palaeo-electronica.org PATTERN MATCHING: CLASSIFICATION OF AMMONITIC SUTURES USING GIS Lori L. Manship ABSTRACT Geographic Information Systems (GIS) is utilized to apply spatial analysis tech- niques to visually and quantitatively match ammonoid suture patterns for classification. The Turonian ammonite family Coilopoceratidae was chosen as the basis for this project, because the similar suture patterns within the family make species-level identi- fication a challenge. A Coilopoceras springeri suture template was created by overlay- ing 10 different Coilopoceras springeri suture patterns, using the right holotype suture pattern as the basal or designation guide. Templates for Coilopoceras colleti and Hopli- toides sandovalensis sutures were constructed in the same manner. Sutures of known and unknown specimens were tested within the templates in order to identify species. The sutures of known specimens matched with the correct templates and did not com- pare well with other species’ templates. Sutures of unknown specimens clearly fit within one template better than within others and, hence, could be reliably classified to the species level. In addition to species classification, the GIS method provides a mechanism for both visual and quantitative comparisons of individual sutures. This GIS method will aid professional and avocational paleontologists, biostratigraphers, and geologists in classifying ammonite species, and may help further our understanding of suture morphogenesis and function by providing a standard basis for morphological comparison of complex sutural patterns. Department of Geosciences, Texas Tech University, Lubbock, Texas, 79409-1053, USA. [email protected] KEY WORDS: ammonite; Geographic Information Systems (GIS); suture pattern; Turonian; Cretaceous PE Article Number: 7.2.5A Copyright: Paleontological Society. December 2004 Submission: 14 April 2004. Acceptance: 10 September 2004. INTRODUCTION shell wall of the ammonite phragmocone. Because of the complex structural components of suture An important method for ammonoid identifica- patterns, it may be difficult to visually match pat- tion is the recognition of suture patterns. These terns for species identification. However, the linear patterns mark the union between the septa and the nature of the sutures makes them a prime candi- Manship, Lori L., 2004. Pattern Matching: Classification of AMmonitic Sutures Using GIS. Palaeontologia Electronica Vol. 7, Issue 2; Art. 6A:15p, 736KB; http://palaeo-electronica.org/paleo/2004_2/suture/issue2_04.htm MANSHIP: GIS IDENTIFICATION OF AMMONITES date for evaluation using a Geographic Information System (GIS). GIS was developed to enable com- puters to perform spatial analysis for environmental problems and geological mapping. Using GIS is a novel and innovative way to apply spatial analysis techniques to paleontological problems. A GIS model has been developed that functions as a user-friendly template for matching ammonitic suture patterns for species identification. Unlike other methods, only a fragment of the ammonite that reveals the lateral sutural elements is Figure 1. Coilopoceras springeri suture pattern using a required–it is not necessary to break the specimen modified version of Wedekind’s terminology. Suture pat- to see the inner whorls. This model will aid paleon- tern nomenclature is expressed by the letters L = lateral tologists and geologists in identifying ammonites and U = umbilical. Curved line separates the saddle for systematics and biostratigraphy. One advan- from the lobe. Straight line is the division between the tage of using the GIS sutural template is that GIS lateral and umbilical sutures. Arrow on venter points software is widely available, and GIS methods are toward aperture. taught in many universities. While developed spe- cifically for species identification, this approach I. The 'U' subscript gives the order in which the also permits quantification of variation in suture umbilical elements appeared during ontogeny. form and, hence, will be a valuable tool for morpho- Ruzhentsev (1949, 1957) and Popov (1965) use a metric analyses. modified version of Wedekind’s terminology, using different names and symbols for sutural elements. Suture Patterns Morphographic sutural terminology is a Sutures consist of groups of individual ele- descriptive system based on the position of individ- ments. These elements transform during the ual elements. Schmidt (1921) developed this sim- course of phylogeny, and hence offer a method to pler morphographic method by adding symbols to identify ammonoids. Two types of sutural terminol- Wedekind’s terminology. This system works well ogies used by paleontologists are morphogenetic for communication of morphological data. and morphographic (Kullmann and Wiedmann Wedekind’s terminology is the oldest practica- 1970). ble morphogenetic system of terminology and is Noetling (1905, 1906) first used morphoge- the most popular today. The terminology used in netic symbol terminology. This system was this paper is a modified version of Wedekind’s. For improved by Wedekind (1913, 1916). Noetling and simplicity, only the L and U symbols will be used, Wedekind’s system is based on ontogenetic devel- because that is all that is necessary for this GIS opment that provides information on homologies. model of identification (Figure 1). Designated symbols are placed on the adult The Coilopoceratidae sutural elements, which record the ontogeny of the element, creating a sutural formula. The Upper Cretaceous Coilopoceratidae Wedekind’s terminology uses five symbols in Hyatt 1903, which includes the genera Coilopo- the order of their phylogenetic appearance. 'E' is ceras Hyatt 1903 and Hoplitoides von Koenen the external lobe and external saddle. The 'E' sad- 1898, are mostly compressed, involute ammonites dle is located on the venter. The saddle on the ven- that can be either smooth or broadly ribbed, and ter is cut medially so that one half is on one side of show slender to somewhat more inflated whorl the ammonoid, and one is on the other. The 'E' sections. They have a sharp venter that is narrowly lobe is between the 'E' saddle and the 'L' saddle. 'L' rounded on early whorls and becomes well is the lateral saddle and lateral lobe. Dorsal to the rounded on the later whorls. Cobban and Hook 'L' lobe is the 'U' saddle and 'U' lobe. 'U' denotes (1980) suggested that the Coilopoceras in the sutures close to the umbilical area of the Western Interior of North America were dimorphic ammonoid. 'A' signifies an adventitious lobe. 'I' is with one form being more compressed than the the internal saddle and lobe, the saddle and lobe other form. Another dimorphic difference noted by dorsal to the 'U' lobe. 'I' elements are covered by Cobban and Hook (1980) is the occurrence of both the overlapping shell and so are not usually visible. smooth and ribbed shells. Some specimens even Juveniles start out with one E, L, U, and I. As the exhibit low, rounded ventrolateral tubercles. ammonites grow and gain more umbilical lobes, Coilopoceras closely resembles Hoplitoides in the suture “formula” is denoted as E, L, U2, U, and appearance and suture pattern, making it difficult to 2 MANSHIP: GIS IDENTIFICATION OF AMMONITES Figure 2. Hoplitoides and Coilopoceras specimens used in this analysis; 1, Hoplitoides sandovalensis USNM 275883; 2, Coilopoceras chispaense holotype (Coilopoceras springeri) BEG 34086. Scale bar in upper image is 5 cm, and in lower image is 10 cm. distinguish between the two genera. Both Coilopo- Table 1. Coilopoceras springeri template specimen’s ref- ceras and Hoplitoides (Figure 2) have a character- erence list. istic suture in which the lateral lobe is broad and deeply bifid, and the dorsal branch of the lateral Museum lobe is in a lower position than the ventral branch. Specimen catalog # Publication Page # Cobban and Hook (1980) stated that Coilopoceras 1 Holotype Hyatt 1903 276, Plate XII was derived from Hoplitoides by the total loss of a Fig. 1 truncated venter. Hoplitoides shows a progressive 2 Holotype “ 276, Plate XII reduction in the extent of venter truncation (con- Fig. 2 stant in each species, but more reduced in younger species), which disappears completely in Coilopo- 3 USNM 420161 Kennedy 1988 66-67 ceras. The difference between Coilopoceras 4 USNM 420159 “ “ springeri (the oldest Coilopoceras) and Hoplitoides 5 USNM 275916 Cobban/Hook 18-19 sandovalensis (the youngest Hoplitoides) is that 1980 Coilopoceras springeri completely lacks a trun- cated venter in the early whorls, whereas Hoplito- 6 USNM 275907 “ “ ides sandovalensis retains a truncated venter in 7 USNM 275917 “ “ the early whorls. The age relationships within the Coilopocer- 8 USNM 275918 “ “ atidae in the Cretaceous Western Interior Seaway 9 USNM 278123 “ 20 of North America are generally sequenced as: 10 Drawing K. Young’s copied Hoplitoides wohltmanni von Koenen 1897 (the old- catalog of est species) followed by Hoplitoides sandovalensis sutures TMM Cobban and Hook 1980, Coilopoceras springeri Hyatt 1903, Coilopoceras colleti Hyatt 1903, and Coilopoceras inflatum Cobban and Hook 1980 Museum of Natural History in Washington, D.C., (considered the youngest Coilopoceras species by the University of Texas Memorial Museum in Aus- Cobban and Hook (1980)). tin, Texas, various literature sources (Table 1), and two field localities from the Chispa Summit Forma- METHODS tion in Texas where over 80 unknown ammonite specimens were collected. The ammonite specimens