A TAXONOMIC REVISION OF THE TERTIARY ECHINOID GENUS MONOSTYCHIA Tony Sadler ORCID: 0000-0002-3406-8885 Submitted for the total fulfilment of the requirements of the degree of Doctor of Philosophy July 2020 School of Earth Sciences The University of Melbourne ABSTRACT For over 100 years the genus Monostychia (Echinoidea: Clypeasteroida) and its type species M. australis Laube, 1869 have been a taxonomic home for a wide range of genera and species with the commonality of a rounded to pentagonal, discoidal test and a submarginal periproct. The specimens comprising this group are all extinct and from the Tertiary strata of southern Australia. While there have been a few minor species identified beyond M. australis, notably M. etheridgei Woods, 1877 and P. loveni (Duncan, 1877), it has been clear to many researchers that the variability remaining in M. australis was representative of numerous other taxa awaiting discovery. Recent taxonomic works on the Clypeasteroida suggested that the number of interambulacral plates on the oral surface of the test of some species was a useful diagnostic character. Of interest were the plates that first come into contact with the periproct. However, there appeared little evidence in the literature that it had been established that the number of such plates remained constant with test length and age, or that the variability in each taxon, of those plate numbers, has been determined. Without understanding those two issues the utility of plate numbers was questionable. This study set out to resolve some of those issues for Monostychia and its relatives. It was found that the number of interambulacral and ambulacral plates on the oral surface was fixed and did not change with increasing test length and therefore there was potential utility for plate numbers as a taxonomic tool. However, there was substantial variability in the numbers. As a result, the use of plate numbers in the paired interambulacra, paired ambulacra, and ambulacrum III on the oral surface appears to have limited utility at genus level. At the species level, however, such numbers can be quite useful diagnostically, particularly when paired interambulacral, paired ambulacral and ambulacrum III plate numbers are used in combination. The plates that first come into contact with the periproct was shown to ii have little value taxonomically at the genus or species level within the monostychioids, largely because most species had the same plate number dominating, but also because of the variability. At subfamily level the taxonomic value of this feature is yet to be established. A previously unreported structural feature was identified in many of the specimens. This was a thin circumferential wall of stereom present on the right-hand side of the test, lying half way between the marginal and central buttressing. It was a form of intestinal buttressing referred to hereafter as the intermurum. Its presence enabled the establishment of a new subfamily, Monostychinae in the family Arachnoididae. Four genera have been placed in the Monostychinae; Monostychia Laube, 1869, Quinquestychia gen. nov., Rotundastychia gen. nov. and Deltoidstychia gen. nov. A key to these genera is provided. Several species have been established and others redescribed in this study. In Monostychia there are seven species; M. australis Laube, 1869, M. macnamarai Sadler et al. 2017, M. alanrixi Sadler et al. 2017, M. merrimanensis Sadler et al. 2019, M. etheridgei Woods, 1877, M. glenelgensis Sadler et al. 2019 and M. robheathi sp. nov. A new genus, Quinquestychia gen.nov., has also been established. It contains four species: Q. mannumensis sp. nov., Q. gigas sp. nov., Q. berylmorrisae sp. nov. and Q. robertirwini (Sadler et al. 2017). The last of these species was published as a Monostychia earlier in this study but reassigned later on the basis of further data. A second new genus, Rotundastychia gen. nov., has also been established. It contains three species: R. pledgei sp. nov., R. aquilaensis sp. nov. and R. eyriei sp. nov. A third new genus, Deltoidstychia gen. nov., has also been established. It currently contains a single species, D. erioaster sp. nov. In addition to the above, two other new genera were established but they do not belong in the subfamily Monostychinae. Instead they are tentatively placed in the subfamily Ammotrophinae. iii The first of these is Obscurostychia gen. nov. with two new species: O. spirographica sp. nov. and O. curtus sp. nov. Keys to all the genera discussed above that contain more than one species have been provided. iv DECLARATION This is to certify that: i. this thesis comprises only my original work towards the PhD except where indicated in the preface; ii. due acknowledgement has been made in the text to all other material used; and iii. this thesis is fewer than 100,000 words in length, exclusive of tables, maps, bibliographies and appendices. Tony Sadler v PREFACE This thesis contains the product of work carried out by me in a part-time capacity over the period September 2012 to May 2020 inclusive of minor breaks agreed to by the University. The work includes several manuscripts that have been published or submitted for publication in collaboration with other researchers as outlined below. The project was conceived entirely by myself. Associate Professor Stephen Gallagher acted as Principal Supervisor throughout the study and contributed to the writing and editing of both the thesis and manuscripts for publication. A/Prof Gallagher also provided logistical and financial support through University channels together with discussion and interpretation of the work throughout. The introduction to this thesis and the description of the genus Monostychia along with the species M. australis, M. elongata and part of M. etheridgei were published in Sadler, T., Kroh, A. & Gallagher, S.J., 2016, A review of the taxonomy and systematics of the echinoid genus Monostychia Laube, 1869. Alcheringa 40, 341-253. (Date accepted 12/01/2016.) Dr Andreas Kroh of the Department of Geology and Palaeontology, Naturhistorisches Museum Wien contributed to this publication by providing access to the type specimens of Laube, insightful discussions around taxonomy of echinoids, editing of the manuscript and suggestions with respect to analysis of CT scanning data, including defining intestinal buttressing in the specimens. The description of M. macnamara and M. alanrixi were published in Sadler, T., Martin, S.K. & Gallagher, S.J., 2017, Three new species of the echinoid genus Monostychia Laube, 1869 from Western Australia. Alcheringa 41, 464–473. (Date accepted 11/11/2016.) A third species, M. robertirwini was also published in this paper but has been reassigned to Quinquestychia in this thesis. Dr Sarah Martin of the Geological Survey of Western Australia contributed to this publication by providing access to specimens held by the Geological Survey, vi writing the initial draft of the section on stratigraphy, discussions about taxonomy of the various species involved and editing the manuscript. The description of M. merrimanesnis, M. glenelgensis and a revised version of M. etheridgei were published in Sadler. T., Holmes, F.C. & Gallagher, S.J., 2019, Two new species of the echinoid genus Monostychia from the Miocene of Victoria and a redescription of M. etheridgei Tenison-Woods, 1877. Alcheringa 43, 279-290. (Date accepted 22/09/2018.) Frank Holmes, an Honorary at Museum Victoria, contributed to this publication by assisting with access to specimens held at Museum Victoria, intense discussions about the data collected, their interpretation and the taxonomy of echinoids, and editing the manuscript. Several images used in this thesis are under copyright. Permission for use has been obtained from the National Library of Australia for images in Fig. 1.1.A. (permission number CD- 6789738) and Fig. 1.1.B. (permission number CD-6802093). The image in Fig. 1.1.D. is provided by the courtesy of the University of Adelaide Archives. The image in Fig. 1.1.C. is from a photographer unknown first published over 100 years ago and is an orphan work. Several images have been used from the three publications identified above in Alcheringa. While copyright for these images was transferred to Alcheringa as part of the publishing agreement, a precondition of that transfer was that the images could be used in educational works such as this thesis. vii ACKNOWLEDGEMENTS Foremost I thank my supervisor, Stephen Gallagher. It was a leap of faith on his behalf to take on a student unknown to him with a project somewhat removed from his specialty. This was compounded by the fact I chose to enroll as a part-time external student. We managed to communicate regularly, succinctly and effectively throughout and the success of the project is in no small way a result of Stephen’s management skills and good humour. I also acknowledge the Australian Commonwealth Government for the financial support of my PhD program through the Australian Government Research Training Program Fee-Offset Scholarship. I am grateful to The University of Melbourne for awarding me two scholarships. The Baragwanath Research Scholarship was used to travel to Vienna to access the type specimens for Monostychia. A separate Science Abroad Travelling Scholarship (SATS) was used to travel to London to access a range of specimens in the Natural History Museum. I am indebted to Dr Rich Mooi of the California Academy of Sciences for providing me with the impetus to engage in this PhD. While I have never met or spoken to him, we did engage in several critical emails prior to my enrolment. He outlined the need for this work to be completed and urged me onward. Such a study would never have been possible without access to museum specimens, equipment and services and I am pleased to acknowledge that I received positive support from all the museum and university staff from whom I sought such.