Journal of Systematic Palaeontology 5 (2): 163–192 Issued 25 May 2007 doi:10.1017/S1477201906002021 Printed in the United Kingdom C The Natural History Museum Hemipatagus, a misinterpreted Loveniid (Echinodermata: Echinoidea) Andreas Kroh∗ Naturhistorisches Museum Wien, Burgring 7, A-1010 Wien, Austria SYNOPSIS The echinoid genus Hemipatagus is a poorly understood fossil spatangoid taxon that is now usually treated as a subjective synonym of the extant genus Maretia, but was originally subject to considerable dispute within the scientific community. Restudy of the species attributed to Hemipatagus and a range of presumably related spatangoids including Lovenia and Maretia has been carried out to solve the problem of its relationships. Cladistic analysis shows that Hemipatagus is not close to Maretia, but is closely related to Lovenia and should be placed in the Loveniidae, which is here confirmed as a monophyletic group. Characters of the adapical tuberculation suggest that in Hemipatagus an internal fasciole is present in early ontogeny, but lost in the adults. A clade comprising the genera Eurypatagus, Paramaretia and Platybrissus, and here named Eurypataginae, appears in all resulting trees as sister group to Maretia. KEY WORDS Echinoidea, Hemipatagus, Loveniidae, Cenozoic, Eurypataginae nov. Contents Introduction 163 History of nomenclature 164 Material and methods 164 Abbreviations and repositories 167 Results 167 Status of Hemipatagus 167 Phylogenetic affinities of Hemipatagus 169 Cladistic analysis 171 Spatial and temporal distribution of Hemipatagus and Maretia 172 Systematic Palaeontology 173 Order Spatangoida Claus, 1876 173 Family Loveniidae Lambert, 1905 173 Genus Hemipatagus Desor, 1858 173 Family Spatangidae Gray, 1825 174 Subfamily Eurypataginae nov. 174 Acknowledgements 174 References 174 Appendix 1 Characters scored in the cladistic analysis 178 Appendix 2 Data matrix 179 Appendix 3 Annotated list of the nominal species of Hemipatagus and Maretia 180 Introduction exploiting organic detritus as their prime food resource. Due to their life habit and evolutionary success they are Spatangoids are echinoids characterised by their bilaterally the most diverse of all extant sea urchin groups and one of symmetrical corona and highly modified ambulacra form- the echinoid clades with the best fossil record (Kier 1977). ing a complex respiratory apparatus. They are well adapted Their highly adapted test morphology provides many fea- to a life as burrowers and ploughers in mobile sediments, tures that can be employed in classification. Consequently * Corresponding author. E-mail address: [email protected] spatangoid taxonomy is, in general, rather straightforward. 164 A. Kroh Particular features, however, have recently been shown (2) the broader, bilobed subanal fasciole in Hemipatagus (he to display high levels of convergence and homoplasy also disregarded this feature, although noted that it is im- (Markov & Solovjev 1995; Neraudeau et al. 1998; Villier portant for generic classification of some brissids). In the et al. 2004; Smith & Stockley 2005). Indeed, spatangoid ‘Treatise on Invertebrate Paleontology’ Fischer (1966: U609) phylogeny and higher-rank taxonomy has been heavily re- adopted Mortensen’s view and thus it was soon widely accep- liant on fascioles. These are narrow bands of small cili- ted in the scientific community, although some authors (e.g. ate spines secreting mucus that consolidates the walls of Philippe 1998: 222; Kroh & Harzhauser 1999: 163) still con- their burrows and protects the respiratory tube feet from fine tinued to express their doubts. Smith (2004: ‘The Echinoid mud (see Lawrence 1987). Unfortunately, fascioles were de- Directory’) noted the high similarity between Hemipatagus veloped several times during spatangoid evolution and can and Lovenia and proposed its inclusion in the Loveniidae. be secondarily lost (Villier et al. 2004; Smith & Stockley Part of the confusion surrounding Hemipatagus and 2005) and the emphasis placed on these structures has led to its relationship to Maretia and Lovenia resulted from considerable confusion and problems in spatangoid system- Desor’s (1858) statement that no fascioles are present in atics. The problem investigated here represents a case where Hemipatagus. Laube (1869) and Etheridge (1875), however, too much emphasis has been placed on presence and absence showed that a ‘spectacle-shaped’ (bilobed) subanal fasciole of fascioles. is present (see Fig. 2). Another major reason for the differing Hemipatagus (Pl. 1) is a genus widely distributed in the opinions resulted from the habit of basing conclusions on fea- Eocene to Miocene of Europe, occurring abundantly in the tures observed in various non-type species attributed to either famous Doberg section in northern Germany (Oligocene) genus (e.g. Duncan 1877). The type species of Hemipatagus and in Early Miocene strata of the Rhoneˆ Basin (Philippe and Maretia, in contrast, were rarely investigated with regard 1998), the Aquitaine Basin and the central Paratethys (Kroh to this question. Furthermore, most authors placed a heavy 2005). It is a spatangoid characterised by its heart-shaped emphasis on the presence or absence of an internal fasciole, outline and heterogeneous aboral tuberculation. The phylo- a feature which is often not readily observed in fossil speci- genetic and systematic relationship of Hemipatagus within mens. Moreover, it is known now that fascioles may be lost the spatangoids is uncertain, although it has commonly been during ontogeny, being present in juveniles and absent in the synonymised with Maretia (Pl. 2, figs 1 & 2), a Pliocene to adults of many spatangoids (e.g. Meoma (partial loss of the extant inhabitant of the Indo-West Pacific. The complicated subanal fasciole: Kier & Grant 1965; Chesher 1969), Para- nomenclatorial history of both genera is outlined below. maretia, Platybrissus and Eurypatagus (complete loss of the In this paper, the relationship between Hemipatagus, subanal fasciole: Mortensen 1950, 1951); see also Neraudeau´ Lovenia and Maretia is investigated using a cladistic ap- et al. 1998; Smith & Stockley 2005). proach based on morphological analysis. This generates a Although discussed at length it is not really clear why phylogeny and revised taxonomy for Hemipatagus and its Mortensen (1951: 23–27) finally chose to synonymise Hemi- relatives. patagus with Maretia. It would have been understandable if he had synonymised Hemipatagus with Lovenia, as he stated himself on p. 27 that ‘On the whole, the distinction between Maretia [here actually referring to Hemipatagus]andLove- History of nomenclature nia is, in case of the fossils, very difficult, the presence or absence of an inner fasciole – the only fully reliable distinc- The genus Hemipatagus was established in 1858 by Desor tion between these two genera – being, rather impossible to for the species Spatangus hoffmanni Goldfuss, 1829 (Fig. 1). ascertain beyond doubt, if the preservation is not very fine.’ It Subsequently, Agassiz (1873: 568) placed Hemipatagus in is difficult to understand why he rejected the shape of the sub- synonymy with Maretia. In the following years this place- anal fasciole as a diagnostic feature in Hemipatagus, while ment was subject to some debate. Some echinologists suppor- widely using it in brissid genera, particularly, as this feature ted Agassiz’s view (Cotteau 1885: 24–25; Fourtau 1920: 83), allows a very clear separation, with no known intermediate while others disagreed (Duncan 1877: 56–58, 1889: 222, 252; species. Mortensen (1951) also made a strong case against Lambert 1909: 107, 1915: 188, 1927a: 87). In his ‘A Mono- the use of the outline and the depth of the frontal sinus, graph of the Echinoidea’ Mortensen (1951: 23–27) discussed arguing that he would be forced to split Lovenia into sev- this matter at length and finally considered Hemipatagus eral genera when using these features to distinguish between Desor, 1858 a junior synonym of Maretia Gray, 1855. His Hemipatagus and Maretia. Yet, it is well known that features opinion was based on the observation that only one of the that are useful to separate some taxa might be highly variable three features discussed in the literature seemed important in others, not allowing a clear separation. to him (the presence of internal ampullae associated with spine tubercles in Hemipatagus). He argued that one feature alone was not enough to justify separation of the two gen- Material and methods era. Moreover, he had also observed internal swellings that he assumed were ampullae in juveniles of Maretia planu- Two specimens of the extant Maretia planulata (Lamarck, lata (Lamarck, 1816) and saw them as proof for his point of 1816) from the Gulf of Siam, Mauritius (NHMW, 2nd view. In addition, Mortensen noted that the presence of am- Zoological Department, collection Invertebrata-Varia no. pullae was not verified in the type species of Hemipatagus. 12715), three specimens of Lovenia elongata (Gray, 1845) The other two features listed by him were: (1) a more heart- from the Red Sea (NHMW, 2nd Zoological Department, col- shaped outline with deeper frontal notch (he disregarded this lection Invertebrata-Varia no. 12714) and 24 well preserved feature, due to the fact that large differences in the depth of the specimens of Hemipatagus hoffmanni (Goldfuss, 1829) frontal notch are also present in other genera, e.g. in Lovenia); from the Oligocene of the type locality Doberg near Bunde,¨ Hemipatagus – a misinterpreted Loveniid 165 Plate 1