Examensarbete vid Institutionen för geovetenskaper ISSN 1650-6553 Nr 307 Study of the Taxonomy and the Inter and Intra Specific Variability of Phacopidae from the Lower Devonian of Algeria: Morphometric Approach and Meaning Gauthier Hainaut INSTITUTIONEN FÖR GEOVETENSKAPER Examensarbete vid Institutionen för geovetenskaper ISSN 1650-6553 Nr 307 Study of the Taxonomy and the Inter and Intra Specific Variability of Phacopidae from the Lower Devonian of Algeria: Morphometric Approach and Meaning Gauthier Hainaut Supervisor: Prof. Catherine Crônier 2015 Title page: Drawing by the author of a cephalon of Austerops lemaitrii sp. nov. in dorsal view Copyright © Gauthier Hainaut and the Department of Earth Sciences, Uppsala University Published at Department of Earth Sciences, Uppsala University, Uppsala, 2015 www.diva-portal.org www.geo.uu.se Abstract: An Algerian Phacopid fauna, described by Lemaître in 1952, is reexamined here. Species are reevaluated in order to be in agreement with modern taxonomy. To characterize the size and shape of our specimens, as well as inter- and intraspecific variations, a morphometric analysis was performed. Only holaspids were analyzed. Results of our analysis show that genera can be be well differentiated thanks to quantitative methods. However, at a specific level, only Austerops lemaitrii nov. sp. is well- defined. Other species can be defined, however, thanks to quantitative methods. Shape variations during growth were also defined in order to understand the evolution of our specimens. Three species show a correlation between shape and size variations for cephala, and two species for the pygidia, which show an ontogenic control of the shape. A covariate analysis was made between the shape of the cephala and the shape of the pygidia, and all of the specimens analyzed show a covariance between cephalic and pygidial shape. Keyword : Paleontology, Trilobite, Devonian, Biometry, Morphometry, Covariance. Populärvetenskaplig sammanfattning Trilobiter utgjorde en viktig del av faunun under paleozoikum. I denna artikel studeras och omprövas en trilobitpopulation från Algeriets devon. För att bättre förstå populationstillväxt och evolution görs analyser av storlek (biometrisk analys) och form (morfometrisk analys). Resultaten visar att de olika släktena är väldefinierade och att tillväxten av somliga arter påverkar formen. Analysen visar också på en samvariation mellan cephalons och pygidiums form. Keyword : Paleontology, Trilobite, Devonian, Biometry, Morphometry, Covariance. Index : 1. Introduction:.....................................................................................................................................1 2. Aim of the study :..............................................................................................................................1 3. Geological setting :............................................................................................................................1 4. Material and methods:.....................................................................................................................3 4.1 Material:...................................................................................................................................3 4.2 Biometric analysis:...................................................................................................................4 4.3 Mophometric analysis:..............................................................................................................4 4.4 Covariance analysis :................................................................................................................5 5. Results : ............................................................................................................................................6 5.1 Biometry:..................................................................................................................................6 5.2 Geomorphometric analysis:....................................................................................................10 5.2.1 Cephala :........................................................................................................................10 5.2.2 Pygidia :.........................................................................................................................13 5.3 Relation between size and morphology:.................................................................................14 5.4 Covariance:.............................................................................................................................16 6. Discussion and Conclusion:............................................................................................................16 7. Acknowledgement:..........................................................................................................................19 8. Bibliography:..................................................................................................................................20 Appendices 1. Systematic palaeontology:.........................................................................................24 Appendices 2. Plates...........................................................................................................................46 1. Introduction: Trilobites were one of the most diverse Paleozoic fossil group, both in term of number of species and disparity. Within trilobites, the Phacopidae family was one of the most diverse. They appeared during the Silurian, and disappeared at the end of the Devonian with the Hangenberg event (Chlupáč, 1994, House, 2002). This last period was very important for the phacopid diversity. In particular, the Early Devonian period was important for phacopid development, with the occurrence of numerous events, which influenced their diversity and its fluctuations. Such events could have induced an increase of trilobite diversity, like the Basal Pragian event (characterized by an increase of trilobite diversity and new elements, and caused by a global regression) or by extinction or faunal turnover, like for the Daleje event (characterized by a transgression of anoxic water, which caused a faunal turnover with numerous small-eyed and blind taxa, Chlupáč, 1994). The lower Devonian is also characterized by several trilobite Lagerstätte deposits (Brett et al., 2012), for example the one from the Emsian of Morocco, which has been well studied (McKellar and Chatterton, 2009). Localities close to Morocco, however, have only been slightly studied (Lemaître, 1952). This study contributes to the systematic study of the Lower Devonian phacopids. The discovery and re-discovery of new occurrences assigned to Austerops, Barrandeops, ?Boeckops and Phacops s.l. from the South West of Algeria give us the opportunity to a better understanding of the genera and the species. Indeed, phacopid trilobites from the localities described by Lemaître in 1952 are redescribed here, and the different specimens are reassigned. Additionally, the disparity of the Phacopids from the Lower Devonian has been explored through a geometric morphometric approach in order to characterize the intra- and interspecific variability. The size and shape of our specimens were also characterized, as well as their shape variations during the growth. 2. Aims of the study : One of the goal of this study is to reevaluate an Algerian Phacopid fauna. Indeed, a lot of work and a lot of progresses were made on this family since the 70's (McKellar and Chatterton, 2009). We also wanted to characterize the inter and intra specific variations of morphology thanks to quantitative methods (and, in particular, geometric morphometric), and compare them with qualitative ones. The last goal was to show and understand the variations in shape that appear during the organisms growth. 3. Geological setting : Specimens come from two western Algerian sections (Fig. 1), near the boundary with Morocco, in an area studied by Lemaître in 1952. This area is mainly composed of Paleozoic rocks in a succession of anti- and synclinals with axes oriented NW-SE (Lemaître, 1952). The first section is the Marhouma or the “km30” section. This section is at 30 km in direction of the SE of the town of 1 Figure 1 : Geological map of the Ougarta region in Algeria and localisation of the studied sections (in red). After Boumendjel et al., 1997. Beni Abbes, and at 5 km of the Mar oasis, and is composed of rocks with a dip of 15°, NNE in direction (Lemaître, 1952). The second section is the Erg Djemel section, situated at 70 km in direction of the South of the town of Beni Abbes. Trilobites specimens come from the Chefar al Ahmar Formation for both sections, which is upper Emsian to Frasnian in age, and is mostly composed of marls intercalating with some carbonate levels. These carbonate levels are more present in the Marhouma section than in the Erg Djemel one (Boumendjel et al., 1997). The base of the Upper Emsian is delimited in this formation by the presence from the chitinozoan species Bursachitina riclonensis (Paris 1981), which is present with conodonts from the invertus zone (Paris et al., 1997). The end of the Upper Emsian is situated at some distance above a remarkable coralligenous level. All Phacopid trilobite specimens are Upper Emsian in age, and were extracted from carbonate fossiliferous levels. Three of these levels (Ed3n1, Ed3n2 and Ed4) come from the Erg Djemel section, while there is only one of them