Bailiella aequalis ( Linnarsson, 1882 )

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 : 1063-1064

Bailiella aequalis ( Linnarsson, 1882)

( Fig. 8 )

Conocoryphe aequalis Linnarsson, 1882: 25 , 26, pl. 4, figs 12-15. — Grönwall 1902: 92, pl. 1, fig. 22.

Conocoryphe (C.) aequalis – Cobbold 1913: 32, pl. 3, figs 18a-c (?).

Bailiella aequalis – Westergård 1950: 28, 29, pl. 5, fig. 13; pl. 6, figs 1-3. — Rudolph 1994: 191, pl. 23, figs 6, 7 (?). — Sdzuy 2000: 308, pl. 3, figs 11-15; pl. 7, figs 4-6 (?).

Bailiella aff. aequalis – Šnajdr 1958: 166, pl. 35, figs 1-5.

LECTOTYPE. — Specimen originally figured by Linnarsson (1882: pl. 14, fig. 12) and designated as lectotype by Westergård (1950). From the Ptychagnostus puntuosus Zone , lower portion, Andrarum , Scania, Sweden.

DIAGNOSIS. — Cranidium width/length ratio of c. 2/1; anterior margin narrow; occipital ring without node; packed coarse granulose ornamentation, grains with flattened to impressed top (based on Linnarsson 1882, with modifications).

MATERIAL EXAMINED. — One cranidium of Bailiella aequalis ( NFM F-3811). Collected at 5.90 m ( Fig. 2 ) of the Manuels River Formation, type locality, Conception Bay South, Newfoundland, Canada .

OCCURRENCE. — Bailiella aequalis is a rare middle Cambrian species ( Westergård 1950), which is here documented from southeastern Canada, eastern Newfoundland, in the Paradoxides hicksi Zone ( Fig. 2 ). It is also reported from United Kingdom, England ( Cobbold 1913), Sweden ( Ptychagnostus punctuosus Zone ; Westergård 1950), Denmark in Bornholm ( Ptychagnostus punctuosus Zone ; Rudolph 1994) and Germany ( Sdzuy 2000).

DESCRIPTION

The cranidium is 40.0 mm wide and 21.0 mm long. The glabella is 11.0 mm wide and 12.0 mm long. It is very wellpreserved as an internal cast, with an anterior margin that appears to be folded backwards.

REMARKS

Bailiella aequalis is closely related to Bailiella tenuicincta ( Linnarsson, 1879) , but differs by a shorter preglabellar area and packed granulose ornamentation. The ornamentation of B.tenuicincta is fine granulose with scattered grains ( Linnarsson 1882). According to Linnarsson (1882) B. aequalis lacks a node on the occipital ring, differing from B. tenuicincta in which this node is present ( Linnarsson 1879). Cobbold (1913) described B. aequalis based on six cranidia of which one was illustrated. He mentioned that these specimens were collected from a coarse sediment and that fine structures might therefore not be preserved.However,the shape of outline as well as the width/length ratio (c. 1.5/1) of the illustrated incomplete cranidium on his plate 3, figure 18a, does not match B. aequalis . We therefore regard the assignment as questionable. A pygidium illustrated by Rudolph (1994: pl. 23, fig. 7) as B. aequalis is doubtful as no diagnosis is known to us for the pygidium of this species. Sdzuy (2000) described and figured several cranidia of B. aequalis . As he also mentioned the fragment of a fixed cheek on plate 3, figure15, cannot definitely be assigned to the species and hence the assignment is here considered questionable.

Figures

FIG. 8. —Bailiella aequalis (Linnarsson,1882) internal cast of a cranidium (NFM F-3811 from 5.90 m). Scale bar: 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).