Hebeia integra, Opik, 1967

Smith, Patrick M., Paterson, John R. & Brock, Glenn A., 2018, Trilobites and agnostids from the Goyder Formation (Cambrian Series 3, Guzhangian; Mindyallan), Amadeus Basin, central Australia, Zootaxa 4396 (1), pp. 1-67 : 60-61

Henadoparia integra Öpik, 1967

Fig. 29

1967 Henadoparia integra ; Öpik, p. 348–350, text-fig. 134, pl. 37, figs 1–5.

2005 Henadoparia integra Öpik ; Jago & Cooper, p. 671, fig. 4M–O, Q, non fig. 4J, P.?2009 Henadoparia cf. integra Öpik ; Bentley, Jago & Cooper, p. 185, fig. 8O–S.

Material. Ten cranidia figured, CPC42415–CPC42424. Fifteen cranidia not figured (mostly fragments).

Description. Cephalon semicircular, up to 4 mm long (sag.) in complete specimens and 6 mm long (sag.) in incomplete fragments. Length:width ratio approximately 53%; moderately convex (sag., tr.). Anterior margin strongly rounded (tr.). Posterior margin bowed moderately anteriorly. Facial sutures appear absent. Glabella anteriorly truncate, trapezoidal in outline, strongly convex, with maximum convexity across midwidth, lateral slopes gently convex; width:length ratio of 84%, occupying 81% of the cephalon length; axial furrow narrow and deep. S1 well defined, deep and narrow (exsag.), intersecting axial furrow approximately level with ε, directed slightly posteromedially for a short distance, before bifurcating with the anterior branch traversing a small distance anteromedially before becoming indistinct and the posterior branch continuing posteromedially. S2 and S3 fainter; S2 is directed transversely, whilst S3 is directed slightly anteromedially. Occipital ring of moderate length (sag.), becoming slightly narrower abaxially, posterior margin strongly bowed backwards. SO narrow, strongly bowed backwards medially, deepening abaxially before intersecting the axial furrow, lateral extremities bifurcate level of anterolateral corners of glabella. Anterior cranidial border narrow (sag., exsag.), slightly convex, occupying about 8% of sagittal cranidial length. Anterior border furrow shallow and wide (sag., exsag.). Preglabellar field short (sag., exsag.); slightly concave, almost forming a preglabellar furrow. Preocular field, slightly convex, strongly downsloping toward the anterior border furrow. Palpebral lobes large, reniform in outline, defined by narrow (tr.), shallow palpebral furrow, anterior tip situated slightly forward of S2, posterior tip just behind the position of S1. Eye ridge moderately defined, extending slightly posterolaterally from S 3 in a straight line towards the anterior tip of palpebral lobe. Palpebral area slightly convex, downsloping towards the axial furrow, maximum width (tr.) is 39% adjacent glabellar width. Postocular field moderately long (exsag.) and slightly downsloping toward the posterior border furrow. Posterolateral corners strongly downsloping in a similar manner towards the lateral corners and onto the genal spine. Posterior border narrow (exsag.), separated from the rest of the cephalon by moderately deep, wide (exsag.) border furrow. Lateral margins of cephalon, including that of genal spine, evenly curved. Lateral border moderately well defined by slightly wide (tr.), moderately deep lateral and posterior border furrows; furrow continues onto genal spine. Genal spine broad-based, blade-like, length approximately 45% cephalic length (sag.).

Prosopon on the borders, palpebral area and palpebral lobes all smooth. Lateral, subocular surfaces of cephalon as well as the glabella and occipital ring covered in minute granules. Genal field with an anastomosing network of genal caeca.

Rostral plate, thorax unknown. See Öpik (1967) for a description of the pygidium from the type locality.

Discussion. The specimens from the Goyder Formation are essentially indistinguishable from Henadoparia integra Öpik, 1967 from the Mindyallan O’Hara Shale and Georgina Limestone in the Georgina Basin. The Goyder Formation cephala have the same outline, a short (sag.) preglabellar field, fused facial sutures, identical glabellar shape and furrow development, matching palpebral lobe morphology, and the presence of genal caeca ( Fig. 29H ).

The Goyder Formation material also closely resembles specimens described by Jago & Cooper (2005) and Bentley et al. (2009), as H. integra and Henadoparia cf. integra , respectively, from the Mindyallan Spurs Formation in Antarctica. While the Goyder Formation specimens are almost identical to those described by Öpik (1967) and Jago & Cooper (2005), the more incomplete specimens illustrated by Bentley et al. (2009) leave some doubt as to whether they are conspecific.

Occurrence. GOY section horizon 73.2 m ( Fig. 3 ). Also found at AS 168.

Distribution. Goyder Formation, Amadeus Basin, Northern Territory. Georgina Limestone and O’Hara Shale, Georgina Basin , Northern Territory and Queensland. Spurs Formation, Northern Victoria Land, Antarctica. All occurrences are Cambrian Series 3, Guzhangian (Mindyallan) in age.

Figures

FIGURE 3. Generalised lithostratigraphy and taxon ranges through the Goyder Formation at the GOY section. Sampled horizons are indicated on the right side of the section, with sample numbers representing tape meterage along the section line (see Fig.2). Measurements on the left side of the section are in meters (true thickness) from the base of the Goyder Formation. SF = Shannon Formation, PSS = Pacoota Sandstone. Solid black circles represent the occurrences of taxa present in the GOY section. Hollow circles represent the approximate stratigraphic occurrences of taxa found at nearby spot localities. Ranges of taxa found only atspot localities approximate, and has been inferred using lithological, faunal and geographical information.

FIGURE 29. Henadoparia integra Öpik, 1967. A–G come from spot locality AS168; and H–M come from sample GOY/97. A, C, CPC42415, partial cranidium; A, dorsal view; C, lateral view. B, D, G, CPC42416, partial cranidium; B, dorsal view; D, oblique anterolateral view; G, anterior view. E, CPC42417, partial cranidium. F, CPC42418, partial cranidium. H, CPC42419, partial cranidium. I, CPC42420, partial cranidium. J, CPC42421, partial cranidium. K, CPC42422, partial cranidium. L, CPC42423, partial cranidium. M, CPC42424, partial cranidium.All scale bars are 1 mm, except J = 2 mm.