Berabichia oratrix

Berabichia oratrix (Orłowski, 1985) (Figs 3-6; 8; 16 A-F; 17)

Comluella oratrix Orłowski, 1985: 244, text-fig. 14, pl. 5, figs 1-7, pl. 7, fig. 9.

Strenuaeva primaeva – Samsonowicz 1959b: 521, pl. 1, figs 1-9; 1962: 11, pl. 2, figs 1-4; 6-7, pl. 3, figs 3; 5.

Termierella sandomirensis – Samsonowicz 1962, pl. 1, fig. 7 only.

Comluella igrzycznae Orłowski, 1985: 245, text-fig. 15, pl. 6, figs 1-6.

Ornamentaspis ? oratrix – Geyer 1990: 127.

Ornamentaspis ? igrzycznae – Geyer 1990: 127.

HOLOTYPE OF COMLUELLA ORATRIX. — External mould of a cephalon with incomplete thorax (MWG ZI/29/1340; former number of the Institute of Geology collection: 1.607), figured by Orłowski (1985: pl. 5, fig. 4), illustrated herein in Figure 3.

HOLOTYPE OF COMLUELLA IGRZYCZNAE. — External mould of cephalon with thorax (MWG ZI/29/1418; former number of the Institute of Geology collection: 1.301), figured by Orłowski (1985: pl. 6, fig. 4a, b), illustrated herein in Figure 5B, D.

TYPE LOCALITY AND TYPE STRATUM. — Igrzyczna Hill, HCM; Holmia-Schmidtiellus Assemblage Zone, Cambrian Series 2 (middle part of the traditional Lower Cambrian).

AGE AND OCCURRENCE. — Berabichia oratrix is known from the Holy Cross Mountains, Poland, from the Holmia-Schmidtiellus Assemblage Zone, Cambrian Series 2 (Samsonowicz 1959b; Orłowski 1985).

EMENDED DIAGNOSIS. — A species of Berabichia with glabella c. 40% of palpebral cranidial width; front rounded to bluntly sub-triangular; occipital ring sagittally of slightly less than 20% of cephalic length; maximum fixigenal width slightly less than 60% of posterior glabellar width; palpebral lobes slightly more than 30% of cephalic length. Librigena with relatively long and slender spine.

MATERIAL EXAMINED. — 14 complete specimens, four cranidia with thoraces, eight thoraces, five cephala, over 840 detached cranidia, three detached librigenae; MWG ZI/29/1103, 1105, 1260, 1263, 1340-1483, 1514, 1526, 1530, 1569; MWG ZI/42/007, 021, 023, 067-072, 074-078, 081-089, 094, 100, 173, 178, 179, 182-188, 190, 191, 193, 195-198, 200, 201, 204, 205, 207-214, 216-218, 220, 223, 224, 227-233, 235-243, 252, 264, 267-272, 274-288; MUZPIG 1.II.8B, 23, 38, 42-45, 57, 59, 63, 64, 68, 73, 80, 85-89; MUZPIG 110.II.37, 38, 56, 62, 68, 70-72, 77, 78, 82, 86, 93, 95-99, 102, 105, 108, 110, 115-123, 126, 130, 133, 135, 141-146, 150, 151, 155-159, 164, 166, 170-174, 176, 177, 180, 182-184, 186, 188-203, 205, 213, 219, 229-231, 235; MUZPIG 113.II.2, 4, 8, 37; MUZPIG 8.II.30, 31; AK 300/CD 20-1, 12/ TA 1−38; UJ 214P/ T 5, 6, 11, 12, 20, 23, 25; JN 033-043, 045-086. All specimens come from the local Holmia-Schmidtiellus Assemblage Zone of Cambrian Series 2 at Słowik, Telegraf Hill, Cisów, Nowa Huta, Igrzyczna Hill, Leśniakowa Dębina, Ociesęki, Sterczyna Hill, Zbelutka, Ujazdek, Malkowska Hill, Buczyna, Pranie, and Dąb, Holy Cross Mountains, Poland. MEASUREMENTS. — Cranidial length 4.4-13.9 mm, cranidial width across centre of palpebral lobes 5.8-18 mm. The holotype cranidium is 8 mm long and 10 mm wide across centre of palpebral lobes.

DESCRIPTION

Cephalon semi-elliptical, overall convexity relatively low; length 127 ± 18 % of palpebral cranidial width (n = 138). Glabella slightly elevated above the fixigenae, defined by distinct furrow, 78 ± 4 % of cephalic length (n = 151) and 39 ± 4 % of palpebral cranidial width (n = 135). Glabella tapering forwards, with rounded to bluntly subtriangular front. Three pairs of rather shallow, slightly backwardly directed lateral glabellar furrows. Occipital furrow narrow and deep, slightly sinuous. Occipital ring 17 ± 3% of cephalic length (n = 151). Occipital node or spine not developed. Fixigenae 67 ± 7% width of occipital ring (n = 123), 29 ± 3% of cephalic length (n = 121) and 57±3% of posterior glabellar width. Ocular ridges indistinct, straight, slightly backwardly directed, visible on the shell exterior only, located at level of S3 and separated from glabella by narrow furrows. Palpebral lobes 32 ± 3% of cephalic length (n = 140), strongly convex, reaching from ocular ridges to posterior border furrows. Palpebral furrow a shallow depression, narrower anteriorly and distinctly widening posteriorly. Palpebral lobes slightly upturned posteriorly. Frontal area 22 ±4% of cephalic length (n = 147), entire, distinctly convex, without border furrow.

Librigena nearly flat, its width is less than onethird of transverse cranidial width across palpebral lobes, with sharp and slender librigenal spine whose base is at level of S1; librigenal spine slightly divergent from lateral margin, reaching to the level of the posterior part of second thoracic segment. In some cases, the spine is visible only on imprints of external moulds.Inner spine angle nearly rectangular. Librigenal border relatively wide and flat, separated from genal field by narrow furrow.

Thorax composed of up to 13 segments narrowing posteriorly, pleurae with distinct, long furrows, extending into backward-directed spines.

Pygidium small, sub-triangular, wider than long, axial piece strongly convex, reaching to posterior margin.

REMARKS

Assignment of this species to Berabichia Geyer, 1990 rather than Ornamentaspis Geyer, 1990 as tentatively suggested by Geyer (1990: 127) is justified by several cranidial features that include: a relatively flat cranidium with a tapering forwards glabella that has a rounded or bluntly sub-triangular anterior lobe, slightly upturned palpebral lobes, and a convex and entire frontal area; the lateral glabellar furrows in the studied specimens are oblique backwards, as in most species assigned to Berabichia, whereas in Ornamentaspis they attain a mixed kingaspidoid and protolenoid pattern (Geyer 1990). In the specimens studied the palpebral furrows are narrower forwards and distinctly wider backwards, a feature considered diagnostic of Berabichia (Geyer 1990: 78). As noted by Westrop & Landing (2000: 873), there is only subtle difference in palpebral furrow morphology between some species of Berabichia and Antatlasia Hupé, 1953. Nevertheless, the species which Westrop & Landing (2000) referred to (i.e. B. inopinata) was subsequently assigned to Epichalnipsus (see above) so that the palpebral furrow morphology can also be taken into consideration in the reassignment of the studied specimens to Berabichia. Morphometric analysis (see above) suggests that C. igrzycznae is a tectonically distorted morphological expression of B. oratrix. Other distinguishing features mentioned by Orłowski (1985: 245) in the original diagnoses have been caused by taphonomic processes (see above).

Berabichia oratrix is closest to B. subdita in most cranidial proportions and in the librigena (see Palmer & Gatehouse 1972: pl. 2, fig. 12). A significant difference is an elongated posteriorly occipital ring and test ornamentation in B. subdita. The external moulds of B. oratrix do not show any evidence of the test’s ornamentation or prosopon. Similar proportions occur also in the type species B. vertumnia; the only significant difference between them is the width of the fixigenae, which reach 50- 55% of posterior cranidial width in B. vertumnia, compared to almost 60% in B. oratrix. Compared with B. stenometopa, B. oratrix has a wider glabella at level of palpebral lobes, sagittally longer occipital ring, wider fixigenae and shorter palpebral lobes. Berabichia wilkesi is known from small, probably juvenile cranidia only, but the available specimens (Palmer & Gatehouse 1972: pl. 9, figs 1, 2) are distinguished by distinct ocular ridges and a relatively wide anterior border. From B. erratica it differs in much wider fixigenae and longer palpebral lobes; moreover, B. erratica differs from other species of the genus in its trend to a sub-arcuate anterior margin of the cephalon. Berabichia rotundata is distinguished from the studied species by a relatively longer frontal area, a bluntly rounded anterior lobe of the glabella and a slightly wider and shallower occipital furrow (Ahlberg & Bergström 1978: pl. 3, figs 1, 2).