Murraypneustes biannulatus, Holmes & Yee & Krause, 2005

Holmes, Francis C., Yee, Christopher Ah & Krause, Janice, 2005, Two new Middle Miocene spatangoids (Echinoidea) from the Murray Basin, South Australia, Memoirs of Museum Victoria 62 (1), pp. 91-99 : 93-94

publication ID	https://doi.org/ 10.24199/j.mmv.2005.62.3
DOI	https://doi.org/10.5281/zenodo.10870974
persistent identifier	https://treatment.plazi.org/id/C17C87DA-990B-716F-FF6E-E65C9347FB18
treatment provided by	Felipe
scientific name	Murraypneustes biannulatus
status

Treatment

Murraypneustes biannulatus View in CoL . sp. nov.

Figures 2A–F View Figure 2 , 3A–C View Figure 3 , 4A, B View Figure 4 , 5 View Figure 5

Type material. Holotype, NMV P312370 View Materials from early Middle Miocene Glenforslan Formation (Batesfordian), Morgan Group, 7 km NNE of Murray River Lock 1, Blanchetown, South Australia [ NMV locality PL 3203].

Paratypes, NMV P312371 View Materials and P312372 from the same location .

Diagnosis. As for genus.

Description. Test moderately large, ovoid in outline with shallow anterior sulcus and pointed, slightly truncated posterior. Specimens range from 72 to 81 mm in length, with maximum width 81–86%TL occurring at 45%TL from anterior ambitus. Test 44.1%TL high (uncompressed specimen) with apex of all specimens well posterior of centre, 63–67%TL from anterior ambitus.

Centre of test on adapical surface depressed around apical disk and proximal end of paired petals to form minor apices in interambulacra 1, 4 and 5, and conjointly, a raised area across ambulacrum III and interambulcra 2 and 3. Adoral surface mildly concave in vicinity of peristome with ambulacrum III slightly recessed anteriorly and the plastron forming a fairly pronounced keel posteriorly, terminating at the anterior edge of the subanal fasciole.

Primary tubercles on adapical surface of 2 distinct sizes, both widely and randomly spaced. Larger of the two restricted to the distal 35% of the radius on interambulacrum 5, and 25% elsewhere. Adorally, larger primary tubercles closely and evenly spaced throughout, with exception of naked areas in ambulacra I and V and phyllode plates of ambulacra II, III and IV. Overlapping scrobicules on adoral surface form distinct diagonal ridges. Small tubercles closely spaced immediately below ambitus increase in size to that of larger primary tubercles below curvature of margin. Large primary tubercles, perforate with undercut mamelon and crenulated platform, and maximum scrobicular diameter of approximately 2.5 mm, twice size of smaller counterparts. Ring of scrobicular tubercles not always present.

‘Peripetalous’ and subanal fascioles present, the former, though not continuously visible on any specimen clearly passes above periproct, while latter is distinctly angular, forming hexagonal outline where in contact with lower edge of periproct. Intermittent horizontal fasciole bands also present laterally above and parallel to marginal ‘peripetalous’ fasciole. Uppermost very narrow and more continuous fasciole, although clear of distal ends of petals, appears to be a rudimentary peripetalus fasciole not indented interradially ( Fig. 3 View Figure 3 ).

Apical system anterior of centre, 39.5–42.2%TL from anterior ambitus to centre of disk, level or slightly below proximal end of paired petals. Ethmolytic, with 4 small closely spaced gonopores approximately 0.3 mm in diameter, anterior pair closer together than posterior pair. Detail of ocular plates indeterminate. Hydropores numerous, approximately 70 visible in one specimen, centrally located but extending between posterior pair of gonopores and possibly ocular plates I and V ( Fig. 4A, B View Figure 4 ).

Petals lanceolate, moderately wide at midlength, closed distally, situated in gentle concave depressions incorporating adradial edges of adjacent interambulacra and continuing proximally across apical disk. Anterior paired petals shorter than posterior pair, extending on average 60% of the radius measured along the surface of the perradial suture from centre of apical disk to ambitus; posterior pair about 56% radius. Inner pores of petals oval, outer pores slot-like, slightly curved and 50% wider. Pore pairs not conjugate but linked by a fine ridge which extends along both sides of each pore ( Fig. 5 View Figure 5 ). Maximum width of interporiferous zone slightly more than twice width of poriferous zone. Anterior paired petals diverge at approximately 135° and contain on average 23 pore pairs, posterior petals 297° and 26 pairs. Secondary tubercles extend randomly across interporiferous and poriferous zones and for a distance outside petals without primary tubercles. Ambulacrum III not petaloid, basically flush with adjoining interambulacra for about 50% radius, then gradually becoming concave towards anterior sulcus. Other details unknown, no sign of pores or regularly spaced tubercles being visible on specimens.

Peristome reniform, centre situated 27–30%TL from anterior ambitus, longitudinal dimension approximately 6.5%TL, transverse dimension 12%TL. Phyllodes short and not particularly well developed.

Labrum long and narrow, averaging 20.5%TL, slightly curved at junction with peristome and abutting the plastron at centre of third pair of adjacent ambulacral plates. Numerous small tubercles adjacent to peristome with a few larger ones towards the posterior end ( Fig. 2C View Figure 2 ).

Plastron closely tuberculate, width approximately 75% length measured from posterior edge of labrum to anterior edge of subanal fasciole. Strong posterior taper suggests sixth and subsequent plates of ambulacra I and V indent behind paired episternal plates.

Periproct opening marginal, not visible from above, tear shaped, slightly wider than high, set in a slight truncation approximately 65° to the horizontal.

Etymology. biannulatus (L) – two-ringed, referring to the presence of two ‘peripetalous’ fasciole rings.