STRATIGRAPHY AND TRILOBITE FAUNAS FROM THE CAMBRIAN BURJ FORMATION 



139 



more complete, and consists of nine cranidia and some cranidial 

 fragments, a rostral-hypostomal plate, three librigenae, and a frag- 

 mentary pygidium tentatively referred to this species (BM U26209, 

 U26211-3). 



Description and discussion. The new specimens show that, 

 despite their fragmentary material, the Richters" description and 

 reconstruction of the cranidium are generally correct. The preglabellar 

 field is slightly longer than they showed it, and in small specimens is 

 crossed by a preglabellar ridge or plectrum; the anterior border bears 

 faint terrace-lines parallel to the margin. The palpebral lobes in the 

 new material are more evenly curved than in the reconstruction by 

 Richter & Richter (1941: pi. 2, fig. 6a); in the new material they do 

 not show the distal narrowing described by Richter & Richter, nor is 

 this very evident in their holotype (Fig. 7). The palpebral-ocular 

 ridge is not joined anteriorly to the glabella, nor is aparafrontal band 

 evident; this ridge appears to slope backwards more steeply in the 

 holotype than in the similarly sized specimen in Fig. 9, but there is 

 some variation in this feature among the various specimens on block 

 It.26209 (Figs 9, 11-13). The postocular section of the facial suture 

 is very short. Where unweathered the surface is seen to be finely 

 granulose. 



The rostral-hypostomal plate (Fig. 10) is abraded but resembles 

 those of other Redlichiidae (Zhang et al. 1980: 69). If correctly 

 assigned to this species, it shows that Redlichops is conterminant. 

 The presence of a plectrum crossing the preglabellar field is com- 

 monly seen in trilobites with conterminant hypostomes. 



The librigena (Fig. 8), confidently assigned because the course of 

 the facial suture corresponds to that of the cranidium, is narrow, the 

 border and the field within the border being of about the same width: 

 in this it differs from the large fragment figured by Richter & Richter 

 (1941: pi. 2, fig. 3), which we exclude from the species. 



One fragmentary pygidium (Figs lla-b) has a long, poorly 

 segmented axis and the pleural field nearly as wide as the axis. There 

 is one weak pleural groove. The surface is finely granulose and has 

 fine striae sub-parallel to the margin. The sculpture is much less 

 conspicuous than that of the pygidia from the same beds assigned to 

 Realaspis. 



The broad interocular areas of the fixigenae and the recurved 

 palpebral lobe make Redlichops blanckenhorni a distinctive taxon, 

 and no closely similar species is known. At a comparable size the 

 Pararedlichiine Eoredlichia yaoyingensis (Kobayashi) has narrower 

 interocular fixigenae and shorter palpebral lobes, but immature 

 forms have relatively longer, more curved palpebral lobes (Zhang et 

 al. 1980: pi. 35, fig. 10), suggesting that the peculiarities oi'Redlichops 

 may be progenetically derived. 



HORIZON. Redlichops blanckenhorni is known only from Jordan 

 and its biostratigraphical significance is not established. Pararedlichi- 

 inae occur typically in the low Lower Cambrian but are not known to 

 range into the Tissafin Stage which is low Middle Cambrian in 

 Geyer's (1990a) usage. However, Redlichops is only doubtfully 

 referred to the Pararedlichiinae, and is here considered to lie close to 

 the Lower-Middle Cambrian boundary, as originally suggested by 

 Richter & Richter (1941: 27). 



Subfamily METADOXIDINAE Whitehouse. 1939 

 Genus REALASPIS Sdzuy, 1961 



TYPE SPECIES. Realaspis strenoides Sdzuy, 1961, by original des- 

 ignation. 



DISCUSSION. Sdzuy (1961) placed Realaspis in the Neoredlichi- 



inae, and Chang (in Whittington et al., 1997: 458) referred it to the 

 subfamily Resseropinae, family Saukiandidae. However, the rela- 

 tively broad interocular area of the fixigenae and the short palpebral 

 lobe favour reference to the Metadoxidinae, as suggested by Opik 

 (1968: 151). 



Realaspis sp. nov. 



Figs 15-18 



Material. Four incomplete cranidia, one librigena, two pygidia, 

 and several doubtful granulose fragments, associated withRedlichops 

 blanckenhorni at Wadi Qunai (BM L26210-2). 



Description. Glabella tapered, rounded in front; glabellar fur- 

 rows very weak, seen on the largest cranidium as faint indentations 

 in the side of the glabella; occipital ring with small spine (Fig. 15a), 

 occipital furrow weak. Anterior border strong, with striae sub- 

 parallel to anterior margin. Preglabellar field practically absent, 

 forming a depressed groove shorter than border. Palpebral-ocular 

 ridge strong, oblique, not confluent with glabella, but in the smaller 

 figured cranidium (Fig. 16) seems to extend into a parafrontal band. 

 The eye extends approximately from the second glabellar furrow 

 (S2) to the occipital furrow (SO). At level of anterior end of eye the 

 width of cranidium is nearly three times the glabellar width at the 

 same level: at the posterior end of the eye it is a little more than twice 

 as wide. Interocular area of fixigena has a marked elongated 

 interocular swelling (Pillola 1993: 859) close to the glabella. 

 Preocular section of facial suture short, straight, subparallel or 

 slightly divergent forwards to the anterior border furrow; posterior 

 section very short. Surface with coarse but not very closely spaced 

 granules. Several fragments on the same bedding planes (Fig. 17) 

 bear the same sculpture and indicate the presence of much larger 

 individuals than the figured specimens. 



Two pygidia (Fig. 18) associated with R. blanckenhorni and 

 Realaspis sp. nov. are referred to the latter because their granulation 

 and coarsely striate margins resemble those of the cranidia assigned 

 to Realaspis. Outline rounded, with length two-thirds of the width. 

 The axis occupies less than half the width and nearly the whole 

 length of the pygidium and has one distinct and one obscure axial 

 ring. The pleural regions have one or two pairs of weak furrows and 

 the margin is entire; there is no semi-ankylosed anterior segment. 

 Surface granulose, with striae near to and subparallel with the 

 margin. 



Discussion. The pygidia of the present taxon are fairly distinc- 

 tive, most resembling those of the Neoredlichiinae and some 

 Metadoxidinae, especially Realaspis strenoides Sdzuy ( 1961 : pi. 4. 

 figs 18-24), though it has 1-2 rather than 3 axial rings. The cranidium 

 is also similar in outline toR. strenoides (Sdzuy 1961: 536(254), pi. 

 4, figs 1-12), but shows more marked relief: in R. strenoides the 

 anterior border and palpebral-ocular ridge are not so strong, the 

 border furrow in front of the glabella is narrower, the eye is shorter. 

 no interocular swellings are seen and there is no occipital spine 

 (Whittington etai, 1997: fig. 249. la). The sculpture \nR. strenoides 

 is unknown, so the granulation of the present species and the striae 

 on the anterior border cannot be compared. 



The present cranidia resemble some bigotinids related toHupetina 

 Sdzuy, 1978, from the lowest trilobite zone in the Issendalen Stage 

 of the Moroccan Cambrian (Geyer 1 990a). They differ from Hupetina 

 antiqua Sdzuy in having weaker glabellar furrows, a stronger ante- 

 rior border and longer preglabellar field: the interocular swelling is 

 larger and closer to the glabella than in Sdzuy's ( 1 978: pi. 1 , fig. 7 ) 

 paratype. In proportions and the weak glabellar furrows the present 

 material is more like the unnamed cranidium from the Lemdad 

 section A2. figured by Sdzuy (1978: fig. 3, top left), though that form 



