Meneviella venulosa ( Hicks, 1872 )

Unger, Tanja, Hildenbrand, Anne, Stinnesbeck, Wolfgang & Austermann, Gregor, 2022, Biostratigraphy and taxonomy of polymerid trilobites of the Manuels River Formation (Drumian, middle Cambrian), Newfoundland, Canada, Geodiversitas 44 (33), pp. 1051-1087 : 1065-1066

Meneviella venulosa ( Hicks, 1872)

( Fig. 10 )

Erinnys venulosa Hicks, 1872: 177 , pl. 6, figs 1-6. — Salter 1873: 5. — Illing 1915: 426.

Erinnys (Harpides) venulosa – Salter 1866a: 285 (?), nomen nudum.

Salteria venulosa – Walcott 1884: 31, 32.

Erinnys breviceps – Matthew 1899: 91-95, pl. 4, fig. 9.

Conocoryphe (Erinnys) venulosa – Grönwall 1902: 94-96, pl. 1, fig. 23.

Bailiella venulosa – Howell 1925: 30, 31 (?).

Menevia venulosa – Lake 1938: 272, pl. 39, figs 4-9; 1940: 273, 274. — Harrington et al. 1959: O244, fig. 181.10.

Menevia cf. venulosa ; Kindle & Whittington 1959: fig. 3i (?).

Meneviella venulosa – Hutchinson 1962: 108, pl. 16, figs 2-7 (?). — Shaw 1966: 855, pl. 99, fig. 17. — Korobov 1973: 124- 126, pl. 12, fig. 1. — Egorova et al. 1982: 110, pl. 3, fig. 10; pl. 9, fig. 10 (?). — Kindle 1982: pl. 1.2, fig. 7. — Morris & Fortey 1985: pl. 1, fig. 10. — Buchholz 1991: 222, pl. 2, fig. 2; 1997: 251, pl. 20, figs 7, 8. — Rudolph 1994: 197, 198, pl. 22, fig. 8 (?). — Cotton 2001: text.fig. 1A, pl. 3, figs 1-4. — Young et al. 2002:, pl. 4, fig. xiii (?). — Fletcher 2006: pl. 34, fig. 37. — Weidner & Nielsen 2014: 75, 76, figs 44A-E. — Bushuev & Makarova 2016: 15, 16, pl. 1, fig. 4.

Meneviella viatrix Shergold, 1973: 21-25 , pl. 10, fig. 1; pl. 11, figs 1-4; pl. 12, figs 1-8.

Dasometopus groenlandicus – Babcock 1994: 87, 88, fig. 7.3.

LECTOTYPE. — Specimen no. SM A1033 , Sedgwick Museum of Earth Sciences, Cambridge, United Kingdom, originally figured in Hicks (1872) and designated as lectotype by Stubblefield (1951), from the Menevian of Port-y-rhaw , St. David’s, Wales.

DIAGNOSIS. — Cranidium with wide border; glabella two thirds of cranidial length with three pairs of furrows, S1 curves back to occipital furrow axially, S2 and S3 short; occipital furrow arching forward axially; occipital ring with node; fixigena divided by ridges that run out from eye ridges, tapering backwards and spread out to anterior part by splitting into venulose markings, posterior part granulated.

MATERIAL EXAMINED. — 16 cranidia of Meneviella venulosa (for NFM numbers seeAppendix 1). All specimens range between 10.00 and 16.55 m ( Fig. 2 ) of the Manuels River Formation, type locality, Conception Bay South, Newfoundland, Canada.

OCCURRENCE. — Meneviella venulosa has a wide middle Cambrian distribution and has been documented from southeastern Canada, eastern Newfoundland, in the upper Paradoxides hicksi to Paradoxides davidis zones ( Hutchinson, 1962) . It has also been reported from western Newfoundland ( Tomagnostus fissus and Ptychagnostus atavus bearing Zone 3; Kindle 1982), United States of America in Vermont ( Paradoxides davidis Zone ; Shaw 1966), Greenland ( Ptychagnostus atavus Zone ; Babcock 1994), United Kingdom in Wales ( Hypagnostus parvifrons to Ptychagnostus punctuosus zones; Thomas et al. 1984; Young et al. 2002) and England ( Paradoxides davidis Zone ; Illing 1915), Denmark in Bornholm ( Ptychagnostus punctuosus Zone ; Buchholz 1991; Grönwall 1902; Rudolph 1994), Russia in Siberia ( Tomagnostus fissus to Paradoxides hicksi zones and Anapolenus henrici Zone ; e.g., Egorova et al. 1982) and Australia in Queensland ( Ptychagnostus punctuosus and Goniagnostus nathorsti zones; Shergold 1973).

DESCRIPTION

The cranidia range from 11.0 mm to 17.0 mm width and from 4.5 mm to 8.0 mm length. They are well-preserved as internal casts and moulds. Some are broken along the dorsal furrow on one side of the glabella. In smaller specimens the venulose markings are less prominent and granulation covers the whole cranidium. Cranidia from stratigraphically lower beds (three cranidia from 10.00 m) have a more prominent granulation than those from stratigraphically higher beds (12 cranidia above 15.73 m). One internal cast has a white surface (NFM F-3655).

REMARKS

Salter (1866a) first reported Erinnys (Harpides) venulosa as a nomen nudum. He doubted that it could be distinguished from Harpides Beyrich, 1846, but without supporting this view by additional information, e.g. descriptions or figures. Thus, the assignment is questionable and Hicks (1872) is the author who first described the species. Matthew (1899) distinguished Erinnys breviceps from Erinnys venulosa based on the marginal furrow and border of the former, which, according to him, does not border the entire cranidium of E. breviceps . Matthew’s plate 4, fig. 9 ( Matthew 1899) illustrates a cranidium attached to the anterior portion of the thorax with a marginal furrow and border surrounding the whole cranidium. Therefore, the illustrated specimen is here assigned to M. venulosa . Howell (1925) repported specimens of Salter’s Erinnys venulosa and named them Bailiella venulosa without providing a description or illustrations. The assignment of his unfigured specimens is questionable. Kindle & Whittington (1959) illustrated one cranidium of Menevia venulosa which does not show the characteristic vein-like markings of the cephalon. Hence, the assignment is questionable. Note that Kindle & Whittington (1959) used Menevia in the figure description and Meneviella in the written text. Hutchinson (1962) described and illustrated different growth stages of M. venulosa , reporting that meraspid specimens (described as younger specimens by Hutchinson (1962)) show a more prominent granulation and less venulose markings than meraspid to holaspid specimens. The assumption that the specimen figured on Hutchinson’s plate 16, figure 2 ( Hutchinson 1962), is a young specimen of M. venulosa cannot be assigned with certainty due to the low resolution of the image.

Shergold (1973) described the new species Meneviella viatrix . According to the author, it differs from M. venulosa by a smaller size, fewer axial rings, more pygidial segments, and weaker geniculation in the posterior cranidial margin. The body size is a questionable taxonomic characteristic ( Müller 1994). In combination with the fewer axial rings, Shergold’s (1973) almost completely articulated specimens may represent a late meraspis stage. Cephala figured by Shergold (1973) are indistinguishable from M. venulosa , especially as no weaker geniculation (diagnostic character introduced by Shergold [1973]) is seen in the posterior cranidial margin. The different number of axial rings may represent a different ontogenetic stage or represent a possible variation within M. venulosa . Shergold (1973) only figured one disarticulated and two slightly deformed pygidia, all three attached to the thorax. The material is preserved and illustrated insufficiently to determine the number of pygidial axial rings. Therefore, M. viatrix is here interpreted to be a synonym of M. venulosa . One cranidium of M. venulosa figured by Egorova et al. (1982: pl. 3, fig. 10) is illustrated insufficiently. Therefore, the assignment is here considered questionable. Babcock (1994) defined the new species Dasometopus groenlandicus . The illustrated fragment in his figure 7.3 shows the vein-like markings of the cephalon characteristic for M. venulosa and was attributed to this species by Weidner & Nielsen (2014). Their suggestion is followed here. A small cranidium with a disarticulated glabella was illustrated as M. venulosa by Rudolph (1994: pl. 22, fig. 8), whose material includes several juvenile cranidida. The illustrated specimen does not show the characteristic vein-like markings of the cephalon. The case is similar to the incomplete cranidium illustrated by Young et al. (2002: pl. 4, fig. xiii). The illustrated specimen does not show the characteristic venulose markings, possibly due to the resolution of the illustration. In both cases, the assignment to M. venulosa is therefore questionable.

Figures

FIG. 10. — Meneviella venulosa (Hicks, 1872): A, B, internal cast and mould of the same juvenile specimen, venulose markings on mould visible (NFM F-3213 from 10.00 m); C, internal cast of cranidium,specimen covert in white (NFM F-3655 from 16.26 m); D, disarticulated internal cast of cranidium (NFM F-3600 from 15.73 m). Scale bars: 1 mm.

FIG. 2. — Lithology of the type locality of the Manuels River Formation, range chart of the here described species. Agnostid biozones from Hildenbrand et al. (2021) and polymerid biozones from Howell (1925).