A NEW STYLOPHORAN ECHINODERM 



53 



University College, London), for her constant encouragement and 

 for providing much useful advice. The suffix -carpus is a latinized 

 version of the Greek word ^apTioo (carpos), fruit, gender mascu- 

 line. 



Diagnosis. An ankyroid stylophoran echinoderm characterized 

 by: extreme reduction in size of M'^ and M^; absence of dorsal bar 

 between M'^ and M^; posterior zygal plate almost straight and with 

 slightly expanded and flattened distal half; poorly pronounced 

 denticulations present on lateral margins of M', and M,; nearly 

 bilaterally symmetrical arrangement of subpolygonal supracentralia 

 on anterior half of dorsal integument; occurrence of a large suranal 

 plate of irregular and variable shape flexibly articulated with M'^, 

 M„ M\ and M.. 



Juliaecarpus milnerorum sp. nov. 



Figs 1-8, Pis 1-8 



Derivation of name. After Drs Andrew R. Milner (Department 

 of Biology, Birkbeck College, University of London) and Angela C. 

 Milner (Department of Palaeontology, The Natural History Mu- 

 seum, London), for their continuous support and exchange of ideas 

 with the author over the years. 



HOLOTYPE. The Natural History Museum, London: Department 

 of Palaeontology, BMNH EE 3070a, b. 



Paratypes. The Natural History Museum, London: Department 

 of Palaeontology, BMNH EE 3069a, b, 3071 -2a, b, 3073^, 3075a. 

 b, 3079a, 3080-1 a, b, 3083a, 3084-6, 3088-9, 3090, 3093-4, 3095a, 

 b, 3098, 3101^a,b, 3105, 3108-9a,b, 31 1 1, 31 13, 31 14a, b, 31 15a, 

 b, 31 16a, b, 31 17, 3 121-2, 3123a-c,3124-5a,b, 3127a, b, 3129a, b, 

 3131-2a, b, 3134-7a, b, 3138-9, 3140-la, b, 3143, 3144-7a, b, 

 3149a, 3150a, b, 3152a, b, 3153, 3155a, b, 3157, 3158a, b, 3160a, b, 

 3161, 3162a, b, 3163-4, 3166-7a,b,3168a-c, 3 169, 3170, 3171a, b, 

 3173a-c, 3175a, b, 3176-7, 3178a, b, 3180-1, 3183^a, b. 



Diagnosis. As for the genus. 



Locality. Specimens were collected from locality 756 of 

 Destombes (see also Chauvel, 1 97 1 ), about 7 km west-south-west of 

 Tazzarine, near Tiz n'Takhrit, Morocco. The reference map is 

 Tazzarine Sheet of 1 : 1 00,000 topographical survey. The map coordi- 

 nates are: x = 477,75; y = 417. 



Horizon. The fossil material occurs in light grey mudstones in the 

 Upper Ktaoua Formation, which lies at the base of the southern part 

 of the Ktaoua plain in the Moroccan Anti-Atlas. The formation 

 consists mainly of grey-green arenaceous argillites interspersed with 

 rare bands of oolitic iron or phosphatic nodules and varies in thick- 

 ness from 70 m to 110m. 



Fossils are mainly concentrated in three different levels: a first 

 level situated 30 m above the base of the formation and dominated by 

 trinucleid and phacopid trilobites; a second level situated 1 m above 

 the previous level and containing a trinucleid fauna; a third level 

 encompassing the upper two-thirds of the formation, where a rare but 

 well preserved and diverse fauna (more abundant than in the previ- 

 ous two levels) is recorded in widespread pelitic carbonate lenses. 



The fauna of the Upper Ktaoua Formation includes, among the 

 other taxa, several brachiopods (e.g. Eostropheodonta intermedia. 

 Eochonetes canaliferus, Chonetoidea radiatula, Comatopoma 

 sororium) and trilobites (e.g. Baniaspis globosa, Brongniartella 

 platynota marocana, Dreyfussina struvei, Eudolatites maiderensis, 

 Flexicalymene ouzregui, Kloucekia poueytoi. Lichas marocanus, 

 Mucronaspis greti. M. termieri, Actinopeltis sp., Amphitryon sp., 

 Calymenella sp., Dionide sp., Onnia sp., Selenopeltis sp., Stenopareia 

 sp.), some echinoderms (e.g. Destombesia diedra acuta, Echino- 



sphaerites aurantium transversalis. Heliocrinites ouguerfensis, 

 Maghrebocystis pachytheca cupuliformis. M. p. robusta, 'Placo- 

 cystites' bohemicus), rare conulariids. cephalopods, gastropods, 

 bivalves, ostracods and abundant microplankton. 



Juliaecarpus milnerorum (henceforth referred to as Juliaecarpus 

 for brevity) comes from the third level. 



Age. Although most fossils in the Upper Ktaoua Formation are 

 endemic, the fauna shows affinities with late Ashgill elements from 

 the British Isles, Bohemia, Poland and Sweden. In particular, species 

 belonging to certain genera of brachiopods (e.g. Eostropheodonta) 

 and trilobites (e.g. Brongniartella, Flexicalymene mid Mucronaspis) 

 are extremely similar to congeneric species found in upper Ashgill 

 rocks of northern, central and eastern Europe. 



Destombes et al. (1985) suggested that the trinucleid trilobites 

 (e.g. representatives of the genus Onnia) indicate an upper Rawtheyan 

 age for the upper part of the Upper Ktaoua Formation, where 

 Juliaecarpus occurs. Detailed palaeobiogeographical comparisons 

 between late Ordovician faunas from different regions of the Medi- 

 terranean Province can be found in Destombes et al. (1985), 

 Destombes & Willefert (1988) and Havlicek (1990). 



With regards to Juliaecarpus, this stylophoran is very similar to 

 several middle Ordovician and some late Ordovician ankyroids from 

 France and Bohemia (e.g. the genera Reticulocarpos. Beryllia and 

 Domfrontia; see also section on morphological comparisons below). 

 Discoveries of other stylophorans from Morocco (e.g. Chauvel, 

 1971; Cripps, 1990; Beisswenger, 1994) strengthen the affinities 

 between Ordovician North African faunistic elements and coeval 

 fossil faunas from several European regions (see also Chauvel, 1981, 

 1986). 



Other referred material. Chauvel (1971: 56, fig. 3f) briefly 

 described a poorly preserved specimen of a stylophoran from the 

 Upper Ktaoua Formation (Destombes Collection, no. 756c), provi- 

 sionally referred by him to the family Kirkocystidae Caster, 1952 

 (formerly placed in the lagynocystid mitrates, but now generally 

 referred to the peltocystid mitrates; Jefferies, 1973; Kolata et al., 

 1 99 1 ; Parsley, 1 99 1 ). The specimen in question is the internal mould 

 of a lower thecal surface displaying a considerable degree of disrup- 

 tion. Unfortunately, Chauvel's (1971) description was not 

 accompanied by photographs and it is, therefore, difficult to ascer- 

 tain the affinities of this fossil. Chauvel (1971) regarded it as an 

 undetermined genus and labelled it as AVIl. 



Based on his line drawings, however, AVII may belong to 

 Juliaecarpus. This is suggested by the relative proportions of the 

 preserved marginalia, including the plate referred to by Chauvel 

 (1971) as the posterior process, based on his attribution of the 

 specimen to the kirkocystids. The plate in question may alternatively 

 be interpreted as a posteriorly displaced posterior zygal plate. The 

 relative size and proportions of the posterior process of M'| with 

 respect to the preserved marginalia are very similar to those observed 

 in Juliaecarpus. 



ANATOMICAL DESCRIPTION 



Theca 



General aspect (Figs 1 , 2). The theca of Juliaecarpus consists of 

 10 marginal plates (or marginalia) forming a peripheral frame inter- 

 rupted posteriody at the level of the anal opening and showing an 

 anterior excavation for the insertion of the aulacophore. The theca 

 approaches a high degree of bilateral symmetry and is longer than 

 wide, subelliptical to vaguely pyriform in outline and with a length/ 



